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1. DO_HPBOTTLE PTOTAL D1_HPBOTTLE PTOTAL DO_HPBOTTLE MFTOTAL D1_HPBOTTLE MFTOTAL 17_TANK MFINFPG 17_TANK MFINOPG 17_TANK MFOUTFUEL 17_TANK MFOUTOXIDIZER 18_FLUIDFLOWWALYE CONTROLYALUE 18_FLUIDFLOWVALVE MFIN 19_FLUIDFLOWVALVE CONTROLVALUE 19_FLUIDFLOWVALVE MFIN 20_ENGINE THRUST 20_ENGINE CSTAR 20_ENGINE CF 20_ENGINE ROF 22_STRUCTURE FORCEMAG 22_STRUCTURE SCVELOCITYX 22_STRUCTURE SCVELOCITYY 22_STRUCTURE SCVELOCITYZ 22_STRUCTURE SCPOSITIONS 22_STRUCTURE SCPOSITIONY 22_STRUCTURE SCPOSITIONZ 24_ATTITUDEDYNAMICS SCQ1 24_ATTITUDEDYNAMICS SCQ2 24_ATTITUDEDYNAMICS SCQ3 24_ATTITUDEDYNAMICS 5CQ4 24_ATTITUDEDYNAMICS SCPHI 24_ATTITUDEDYNAMICS SCTHETA C 24_ATTITUDEDYNAMICS SCPSI Create graph Run Debug Profile Versioning Tools Window Help TBD amp G 4 x E Engine java x E Enginecontroler java x 8 PRegri java x FA 0 File Graph P D 1 750 1 500 1 250 1 000 750 500 250 0 0 50 100 150 200 250 300 350 time s 20_ENGINE CSTAR 4 D 61 5 41 11 a lt 7 0 50 100 150 200 250 300 350 time s 20_ENGINE ROF en 0 25 50 75 100 125 150 175 200 225 250 275 200 325 350 375 time s 18_FLUIDFLOWVALVE CONTROLVALUE 19_FLUIDFLOWVALVE CONTROLVALUE alizatio D 25 000 4 22 500
2. Figure 3 OpenSimKit MMI main window The MMI main window comprises two subwindows The upper subwindow displays the OpenSimKit User Manual V3 7 0 17 94 submitted commands and their state and the lower subwindow displays the logged parameters sent to the MMI by the simulator via a packet transfer mechanism during running simulation The MMI menu bar comprises a File and a Figures menu s File menu Four buttons representing the most important OpenSimKit simulator control commands and a button to shutdown the MMI are included Shutdown of the MMI automatically implies shutdown of the simulation too O O O O 0 Click on the menu item File and then on the menu item Run to start the simulation computation Now you can enter commands in the Cmd Window Just enter your commands in the command window Named Cmd Window in the last empty line and hit the enter key to send the command For the results of your commands take also a look at the console output in addition to the Log Window Click on File Stop to pause the simulator Click on File Resume to resume the paused simulator Click on File Shutdown to terminate the MMI and the simulator For a list of available commands take a look at chapter 9 Command Reference The simulation generates an outputfile in this example named myOutFile txt into which it cyclically log the output results of the computation according those the variables selection and log frequency
3. get lt instance gt lt field gt Returns the value of a manipulatable variable lt instance gt is the name of the component instance you want to adress in case a class is instantiated more than once It is case sensitive With the supplied sample files there exist 20 components named 00 HPBottle to 19 FluidFlowValve However not all have manipulatable variables Use the help command to get a list of all available manipulatable variables lt field gt is the name of the member variable of the instance of which you would like to get its value It is case sensitive The following fields are in the instance 00_HPBottle mass double variable volume double variable specificHeatCapacity double variable ptotal double variable ttotal double variable fluid String variable Examples get 00 HPBottle mass 9 3 4 GetA geta lt instance gt lt field gt lt position gt Returns the value of an element of an one dimensional array lt instance gt is the name of the component instance you want to address in case a class is instantiated more than once It is case sensitive With the supplied sample files there exist 20 components named 00_HPBottle to 19 FluidFlowValve However not all have manipulatable variables Use the help command to get a list of all available manipulatable variables lt field gt is the name of the member variable of the instance of which you would like to get its value It is case s
4. Jens Eickhoff 2 0 2004 First OpenSimKit C release Jens Eickhoff 2 1 Dec 2004 C V2 1 cleaned up code release no longer comprising unused interfaces Jens Eickhoff 2 2 Feb 2005 Featuring XML inputfiles Peter Heinrich ETH Z rich 2 3 Mar 2005 Featuring XML Inputfile editor Peter Heinrich ETH Z rich 2 4 Aug 2006 Div bug fixes amp first Doxygen C code docu Jochen Scheikl Matthias Raif TU M nchen 2 4 1 Sept 2006 Simple Power electric system demo Jens Eickhoff 2 4 2 Jul 2007 Java control console amp simulator demo as multi program multi threading application Jens Eickhoff OSK J May 2008 OSK J 2 4 in Java port from C to Java V2 4 2 Alexander Branat OSK J July 2008 First version with full Ant based build system V2 4 4 Alexander Branat OSK J Sept 2008 Port of MatLab SimplePower Model to Java V2 4 5 Ivan Kossev Universit t Stuttgart OSK J Oct 2008 Provision of a simple Orbit Propagator in Java V2 4 6 Ivan Kossev Universit t Stuttgart OSK J 01 11 2008 Version featuring new XML File Structure revised V2 5 0 inputfile parsing and entirely new model kernel registration mechanisms First approach in direction of a service oriented architecture Alexander Branat OSK J Feb 2009 Now implementing absolute simulation time in ISO V2 5 1 format Alexander Brandt OpenSimKit User Manual V3 7 0 90 94 Release Date Changes OSK J May 2009 First release containing a first par
5. The Java Astrodynamics Toolkit is used in a very bare version which supports only the gravity model This is necessary as the complete JAT is very huge library which has itself lots of dependencies s Packet Library Used for the communication between the MMI and the Simulator However the Packet Library is an OpenSimKit subproject and therefore delivered as source code and completely included into the build process e Junit 4 6 JUnit is used as a framework for the unit tests included in the OpenSimKit source distribution e JFreeChart 1 0 12 JFreeChart is necessary for plot windows These software libraries are directly included in the OpenSimKit downloads and do not need to be installed separately by the user If the user already has other versions of these libs installed OpenSimkit will use its own ones during the build process to avoid conflicts The advantage is that OpenSimKit can be fully deinstalled simply by deleting its installation directory OpenSimKit User Manual V3 7 0 12 94 Part 5 Downloading amp Installing OpenSimKit When downloading OpenSimkit from the website the user receives a zip archive file which may be copied to the installation directory e g home OpenSimKit Unpacking the zip for an OpenSimkit release osk j X Y Z src zip will lead to generation of a subdirectory osk j X Y Z src in the selected installation directory By this means multiple OpenSimkit releases easily can be installed aside of e
6. mesh for mesh definitions Attributes none 8 6 2 Mesh Section Example A nested mesh definition is shown below OpenSimKit User Manual V3 7 0 25 94 lt meshes gt lt mesh name mesh_0 level top gt lt model gt 21_EngineController lt model gt lt mesh gt mesh_1 lt mesh gt lt model gt 22_Structure lt model gt lt model gt 23_Environment lt model gt lt mesh gt lt mesh name mesh_1 level sub gt lt mesh gt mesh_2 lt mesh gt lt model gt 05_Pipe lt model gt lt model gt 06_Filter lt model gt lt model gt 07_Pipe lt model gt lt model gt 08_PReg lt model gt lt model gt 09_Pipe lt model gt lt model gt 10_Split lt model gt lt model gt 11_Pipe lt model gt lt model gt 12_PReg lt model gt lt model gt 13_Pipe lt model gt lt model gt 14_Pipe lt model gt lt model gt 15_PReg lt model gt lt model gt 16_Pipe lt model gt lt model gt 17_Tank lt model gt lt model gt 18_FluidFlowValve lt model gt lt model gt 19_FluidFlowValve lt model gt lt model gt 20_Engine lt model gt lt mesh gt lt mesh name mesh_2 level sub gt lt model gt 00_HPBottle lt model gt lt model gt 01_HPBottle lt model gt lt model gt 02_Pipe lt model gt lt model gt 03_Pipe lt model gt lt model gt 04_Junction lt model gt lt mesh gt lt meshes gt 8 7 logOutput This element
7. Rouven Witt Attitude dynamics implementation Ivan Kossev Code merges system integration tests debugging packaging and user manual enhancements Jens Eickhoff OSK J December 2010 V3 6 0 V3 6 0 Dynamically updating plot windows including ground track plot of the rocket over Earth Michael Fritz Fix of a problem in Celestia with scripted spacecraft attitude via ECI quaternions Jens Eickhoff and Ivan Kossev Fix of longitude position computation formally implemented via Java Astrodynamics Toolkit Michael Fritz Oliver Zeile Jens Eickhoff User Manual updates Rouven Witt Jens Eickhoff OpenSimKit User Manual V3 7 0 92 94 Release Date Changes OSK J January 2011 Implementation of provider subscriber mechanism V3 7 0 for model variable interchange Alexander Brandt Jens Eickhoff User Manual updates Michael Fritz Ivan Kossev Jens Eickhoff OpenSimKit User Manual V3 7 0 93 94 21 License Trademark and Warranty Disclaimer e OpenSimKit Is a registered trademark of the original tool inventor and open source project coordinator Dr Jens Eickhoff Immenstaad Germany OpenSimkit is free software You are free to publish copy use and modify it under the conditions of the GNU General Public License Version 3 as published by the Free Software Foundation A copy of the GNU General Public License is enclosed in the tool distribution downloadable from www ope
8. where c m s is the characteristic velocity of the combustion gases in the 0 m thrust chamber c is mainly a function of the mixture ratio OF 5 of oxidizer to fuel f mass flow rate Now the nonlinear behavior of the thrust can be calculated with F mcxc 11 81 The values for c and cf are theoretical values with 100 efficiency thus efficiency factors for c and cr are used c describes the thrust factor a number that describes the the augmentation of thrust from the thrust chamber in the nozzle The value of cr depends mainly on the ambient pressure and the conditions in the thrust chamber The altitude for the ambient pressure calculation is currently static and needs to be imported from the Lat Long Alt routine 11 12 1 1 Characteristic Velocity c A polynomial for c has been calculated with NASA s CEA Gordon McBride http www grc nasa gov WWW CEAWeb c ber O F 2000 00 Eu 6 5_ 4 3 1800 00 y 0 1481x 4 3126x 50 87x 309 5x 1011 1x 1549 9x 880 12 1600 00 R 0 9999 1400 00 F z Astris N204 Aerozin 50 1200 00 1000 00 Probe des Polynoms 800 00 Polynomisch Astris N204 Aerozin 50 600 00 400 00 200 00 0 00 T T T 1 0 00 2 00 4 00 6 00 8 00 OpenSimKit User Manual V3 7 0 53 94 The values for c from the polynomial are ideal without losses so a factor for the combustion efficiency n c has been introduc
9. EngineController is a unit designed for control of oxidizer and fuerl flows to the engine of the modelled rocket It provides two analog line outputs which e g can be connected to FluidFlowValve components In the Engine Controller for each output line the function of the control value over time has to be programmed by the user according to the user s needs The delivered example code starts with a signal value read from input file and reduces the output signal within 200sec to zero 11 11 The IntervalController Model The IntervController also is a unit designed for control of oxidizer and fuerl flows to the engine of the modelled rocket lt provides two analog line outputs which e g can be connected to FluidFlowValve components This model class allows to specify up to 10 time intervals with individual control output value setting The start end time and value for each interval are loaded from the according input file section for both of the output lines Refering to Figure 6 the IntervalController and the EngineController can alternatively be used to control the rocket stage engine OpenSimkit User Manual V3 7 0 52 94 11 12 The Engine Model 11 12 1 Basics In previous versions of OSK the Engine thrust was only calculated with a constant ISP value with F mISPg 11 50 where m is the total mass flow of oxidizer and fuel into the thrust chamber To get a more realistic behavior the ISP is calculated from sp F g
10. Equipment Models in OpenSimKit This chapter describes the creation and use of a sample OpenSimKit system equipment model For a first look at the OpenSimkit architecture a simple temperature sensor for the example rocket stage system is implemented It starts with the creation of a Java class representing the component model and goes on to explain the compilation process of the model After this the input file is changed so that the model is actually used by the Simulator After a simulation run the simulator created output file is analyzed 16 1 Prerequisites e Netbeans IDE http www netbeans org get at least Version 6 1 e Create a Netbeans Free form Project for the OpenSimKit Simulator as described in the document Netbeans 6 x Integration odt found in the osk j x y z src doc directory As this tutorial focuses on the creation of a simulator component model it requires the use of the Netbeans IDE Although it is possible to use another IDE or no IDE at all to create an OpenSimkit component model the constraint of using only one IDE makes this tutorial much more focused on model development instead of IDE differences It is possible to use Netbeans 6 x for OpenSimKit Component development 16 2 Writing a Java Class For this tutorial it is best to include the new model in the rocket propulsion model library The reason for this is that there exists already a build file for this library and this model can be easily seen in action when in
11. contains all information about the logging of model variables to the output file OpenSimKit User Manual V3 7 0 26 94 Containing elements Fehler Referenz nicht gefunden Attributes Attribute Type Required Description delimiter string yes The delimiter between two entries The string T stands for the tabulator end string yes The time for which the logging will end factor positive yes Every factor iterations an entry is written to the integer output file start string yes The time for which the logging will start 8 7 1 entry This element contains information about one logfile entry Containing elements none Attributes Attribute Type Required Description format string no How the output value should be formatted All Java formatting options are supported see http java sun com j2se 1 5 0 docs api java util Formatter h tml header string no The header of the output values If this attribute is missing then the name of the variable is used for the header model string yes Name of the model variable string yes Name of the model s variable which should be written to the output file 8 7 2 LogOutput Section Example A log output definition is given below lt logOutput start 0 0 end 250 0 factor 1 delimiter t gt lt entry model timeHandler variable simulatedMissionTime header Mission Time format S1StFTS1StH
12. currently only tested with Ant 1 7 0 and higher versions To compile OpenSimKit open a terminal console on your computer and navigate into the OpenSimkit distribution s build subdirectory Principally the build system has multiple targets i e simulator MMI etc can be built individually but this feature is postponed to a later chapter here For the beginner user the simple command gt ant all builds all binaries in the archive including the according javadoc documentation This is what most newcomers will do first The build process will report building of the diverse targets onto the text console A message similar to BUILD SUCCESSFUL Total time 4 seconds will document the successful compilation of all targets and the proper arrangement of all configuration files in the work directory 7 Quick Start Information To run a simulation the simulator must be started first It will start up and wait listening to communication sockets 1500 and 1510 for a Man Machine Interface to connect to it So after simulator startup the MMI has to be started which automatically searches for a booted simulator and connects to it and then from the MMI the simulation can be started stopped controlled terminated etc These steps are explained now in the subsequent subchapters 7 1 Starting Simulation and MMI To start up the simulator go into the work directory of the OpenSimkit distribution installation and type Command line Windows os
13. density and the friction coefficient now the outlet pressure of the pipe can be computed via y T Pou Pin 7 ur 11 14 For reflecting the throttling effects and heat transfer from pipe wall to fluid the pipe is split into 10 subsections and for each element the subsequent temperature changes are computed individually First the Nu elt number has to be computed which is done applying Re 1000 Pr 2 14127 PF 1 This equation again reflects the transition area and the entirely turbulent flow range 7 can be computed from the Reynolds number with 2 3 o Nu 1 11 15 T 1 82log Re 1 64 11 16 The heat transfer coefficient finally can be derived again via a Nun 11 17 11 4 The Junction Model The JunctionT1 model just serves to add the fluid flows from two inlets to one outlet flow Neither specific pressure drop effects nor heat transfer effects are considered The model however in backiteration steps of the boundary problem DEQ solving also works in reverse order by assuming inlet flows from left and right side and by saving the ratio derived in the previous iteration OpenSimKit User Manual V3 7 0 43 94 11 5 The Filter Model The FilterT1 model reflects the effects of a gas flow through a gas filter holding back any dust or other particles The pressure drop of the gas flow is modeled by a linear dependency equation The pressure drop at 0 0 ks s flow is obviously 0 0 bar The
14. down the variable meanings e The first 2 3 letters indicate the physical variable E g a heat transfer coefficient Alpha is called Alxxxx e The middle part typically indicates e g whether the variable describes something about the outer wall Au enwand AW or the separation wall btw Oxidizer and fuel tank Trennwand TW E g ALTWxx e The last letter s indicate whether the variable describes the tank wall section in contact with fuel Brennstoff B or oxidizer Oxidator O and whether the part with gas G or liquid L contact is described E g ALTWGO is the variable for the heat transfer coefficient Alpha between the separation wall and the gas in the oxidizer compartment 11 8 1 The Differential Equation System The processes inside the tank which take place during rocket stage operation can be reflected by a system of coupled first order ordinary differential equations The numerics problem to be solved is propagation all changes over time i e an initial value problem All variables describing the physics inside the tank shall be known at time For this point all derivatives of the to be integrated variables can be computed and the values for t dt are to be integrated numerically The tank model therefore computes all variable derivatives by means of the method DEQDeriv and provides them to the solver in a one dimensional array Y F t Y 11 19 t Start value of the independent variable time Y Arra
15. fixed frame and as positions in longitude latitude altitude format A more realistic model of the rocket engine computing thrust according to fuel oxidizer mixture and depending on flight altitude atmospheric pressure Ivan Kossev Mario Kobald Fabian Steinmetz Christoph Gomringer Helmut Koch Universitat Stuttgart OpenSimKit User Manual V3 7 0 91 94 Release Date Changes OSK J December 2009 V3 3 0 IntervalController model added which can be used as alternative to the EngineController By means of this model e g multiple engine firing off time intervals can be defined The PointMass model was updated to interpret resulting forces as being always tangential to orbit flight vector until a detailed attitude dynamics is available A first use of both new PointMass and IntervalController was to simulate a first rocket stage Hohmann orbit transfer PointMass enhancements by Ivan Kossev Universit t Stuttgart IntervalController Inputfile configuration for Hohmann Transfer and user manual enhancements Jens Eickhoff OSK J December 2009 V3 4 0 This release comes with an enhanced MMI featuring a S C ground track plot over Earth map to track S C position User manual enhancements Michael Fritz and Jens Eickhoff OSK J April 2010 V3 5 0 Comprising simple spacecraft attitude dynamics and interface to 3D Astrodynamics toolkit Celestia 3D geometry model and raw Celestia Lua scripts by
16. fuel tank Y 15 Temperature of outer wall of fuel tank in contact with gas Y 16 Temperature of outer wall of fuel tank in contact with liquid Y 17 Temperature of separation wall of fuel tank in contact with gas Y 18 Temperature of separation wall of fuel tank in contact with liquid Y 19 Mass of liquid oxidizer in oxidizer tank compartment Y 20 Mass of liquid fuel in fuel tank compartment In analogy thereto the variables stored in field Y of the TankT1 model represent the according derivatives E g Y 1 Mass flow of pressurization gas in oxidizer compartment Y 2 Temperature gradient of gas phase in oxidizer compartment Y 3 Volume gradient of gas phase n oxidizer compartment etc These derivatives Y can be expressed as functions of the state variables Y The according thermodynamic equations are cited in the subsequent sections OpenSimkit User Manual V3 7 0 46 94 11 8 2 Thermodynamics of the Oxidizer Tank Since the nitrogentetroxide as oxidizer has a non neglectable vapor pressure at 300K the gas phase in the oxidizer compartment must be treated as mixture of both oxidizer vapor and pressurization gas Helium Computations however have shown that the mass of gaseous oxidizer can be assumed to be constant over the rocket stage operations time 1 The temperature in the tank decreases during propellant consumption which implies that oxidizer vapor would condense but the overall volume of the gas phase increases Thus despite
17. id est gt that is with respect to Technical Abbreviations DEQ ECI ECEF IDE JAT JDK JRE JVM MMH MMI OSK SW XML Differential Equation Earth centered inercial coordinate frame Earth centered Earth fixed coordinate frame rotating with the Earth Integrated Development Environment Java Astrodynamics Toolkit Java Development Kit Java Runtime Environment Java Virtual Machine Monomethylhydrazine Man machine Interface OpenSimkit Software Extensible Markup Language OpenSimKit User Manual V3 7 0 8 94 2 Introduction OpenSimkit is a free System Simulation software used for teaching purposes at the University of Stuttgart Germany From its historic roots its application to spacecraft engineering is by far the most mature domain The very first core simulator was implemented in FORTRAN 77 in the eighties 1 later was converted to an object oriented Kernel in C mid of the nineties 2 and was made available for student s use in 2004 by the original author Begin of 2008 the toolkit was converted to Java language by one of the former students Alexander Brandt to make it even more generic and simple to use for students getting in touch with a simulator for the first time Applying Java all the nasty pointer and references handling topics belonged to the past the build process was significantly simplified for a user and finally also the simulator now is independent from the underlying operating system preferred by
18. lt logOutput start 0 0 end 250 0 factor 10 delimeter t gt lt entry model 20_TemperatureSensor variable temperature gt lt End changes for TemperatureSensor test gt lt logOutput gt OpenSimkit User Manual V3 7 0 81 94 16 5 Analyzing the Output File If the output file outfile txt is opened there should be an additional column named S18 TEMPERATURE in the file If the default simulator settings were used the values of the output file for the S18 TEMPERATURE column should look like this S18 TEMPERATURE 300 000000 301 272749 302 792946 304 637163 306 531399 308 227183 309 544285 310 382221 310 713733 310 568240 310 011523 309 126704 307 999127 306 706321 305 312682 303 867866 302 407565 300 955543 299 526275 298 127368 296 761670 295 428949 294 127142 292 853235 291 603823 290 375467 289 164980 287 969420 286 786121 285 612714 284 447013 283 287346 282 132376 280 980871 279 831664 278 683607 277 535991 276 388402 275 240327 274 091226 272 940610 271 788361 270 634546 269 479107 268 321976 267 163104 266 002430 264 839882 263 675404 262 508907 261 340189 OpenSimKit User Manual V3 7 0 82 94 17 Coding Guidelines During OpenSimkit porting developing from C to Java a few guidelines consistently have been applied They are presented here and should be followed by all contributors s No wildcard imports http stackoverfl
19. mc m mc 11 6 vV The cinetic energy of pressurant leaving the bottle can be neglected here 01 The conductive heat transfer results from the temperature difference btw fluid and bottle wall and is driven by the heat transfer coefficient O aA T T 11 7 For computation of the pressure gase s specific enthalpy please refer to section 11 1 Currently for integration of the DEQ 11 6 a simple explicit Euler method is used which is acceptable since all gradients are negative and thus the method is always converging and stable TST AT 11 8 new The gas pressure after finishing the timestep integration i e after simulating a dm of mass has vented from the bottle to its outlet is computed under consideration of the non ideal behaviour of the gas at high pressure levels This is essential for Helium as pressurant The deviation from the ideal gas law is reflected by the compressibility factor Z The equation reads as follows p ZpRT 11 9 The density p results from division of the remaining mass by the bottle volume But the factor Z itself is a function of the pressure The dependency of Z as function of p is computed in the pressurant Helium gas model through a polynomial approximation which is checked against experimental data 02 See equations 11 4and 11 5 Applying this OpenSimKit User Manual V3 7 0 40 94 method the remaining pressure in the bottle is computed iteratively A start pressure from ideal gas e
20. settings in the inputfile These logged parameters can be visualized in diverse ways using the next MMI menu Visualization OE amp 1 000 2 000 3 000 4 000 5 000 6 000 000 8 000 9 000 22_STRUCTURE SCPOSITIONX 22_STRUCTURE SCPOSITIONY 22_STRUCTURE SCPOSITIONZ Figure 4 MMI plot window with plotted simulation results e Figures menu O O O The first menu entry can be used to locate a simulation output file of a completed or still running simulation The second entry opens a dialog box for selection of parameters from the outputfile which are to be plotted over time together in one plot window An example of such a plot is given by Figure 4 Multiple such plot windows with different parameter sets may be opened in parallel The third menu entry opens a ground track plot window depicting the OpenSimkit User Manual V3 7 0 18 94 spacecraft s position evolution over an earth map see Figure 5 Figure 5 MMI spacecraft ground track plot over Earth map Since V3 6 0 of OpenSimkit the plot windows of the MMI are automatically updated with new parameter results written to the OSK result output file So parameter values evolving over time can be monitored The plot granularity depends on the output stepsize selected for the simulator result logging to the output file The latter is an adjustable parameter in the simulation run input file OpenSimkit User Manual V3 7 0 19 94 8 S
21. the decreasing partial pressure of the oxidizer approximately the overall mass of oxidizer is kept in vapor state over the entire stage operations time if extremely long coast phases are excluded This implies 0 11 22 The time derivative of the intrinsic energy of the gas volume in the oxidizer compartment can be formulated as U ai Myap Uyap T M reas U proas 1 1 23 From these two equations results U M si C prgas L m vap y P a m prgas Cy ee T gas 1 1 24 The first law of thermodynamics formulated for the gas volume of the tank oxidizer compartment thus reads m h T Q m C T m C M reas C P pikas Ta T P gas V eas 1 1 25 prgas prgas in prgas v prgas gas vap v vap The generic gas equation rearranged to solve for the temperature is VB T gs 5 11 26 S R gas M gas with M gas 7 M yap T M prgas 1 1 27 The differentiation of equation 11 26 results in 4 Vo R V as My T a gas D gas D En gas gas D gas gas dd prgas 1 1 2 8 gas M gas R gas m gas R gas m gas OpenSimKit User Manual V3 7 0 47 94 thereby keeping peas constant via pressure control In this formula Rsa represents the specific gas constant of the mixtrue from oxidizer vapor and pressurization gas R can be computed from m o oR m R R prgas prgas vap vap 1 1 29 m gas Considering equation 11 22 the differentiation then leads to R m prgas R prgas m prgas R prgas m vap Rn
22. the main graphics window from where the simulator can be commanded via mouse amp menu functions Also result plot amp log sub windows are provided here In addition during run the MMI process logs certain progress info into its start up ASCII terminal See also the figure with MMI 8 console snapshots above Since Version 3 5 0 OpenSimKit in addition offers an interface to the astrodynamics visualization toolkit Celestia 6 for displaying simulated spacecraft in 3D in Orbit Details on this functionality are given in Part Ill of this manual OpenSimKit performs simulation of technical scientific systems which are modeled via mathematical differential equation systems In principle it is suited for simulation of a large variety of systems such as power plants automobiles as well as for aerospace applications like rockets and satellites Environment 2222 Se ee W W W W W m m Ba m ter IH Line Based Data Fs EM Numerical Line Based IFs Pwr Y gt DEQ Solver Physical thermal IFs ME Physical mechanical IFs gt Figure 2 Components and Interactions Example Satellite Modeling from 3 OpenSimKit provides both solving of initial value problems e g spacecraft orbit propagation as well as boundary value problems and their combination e g physics of spacecraft propulsion systems or space station life support systems The important upgrade implemented in OpenSi
23. time with millisecond resolution 14 8 System time The time of the system Normally this is local time This is in the default Java time format which is Unix time with millisecond resolution 22 n Data The data size ranges from 0 to a maximum of 2027 octets 22 n 2 Checksum The CRC16 CCITT checksum of the header and data Basically it is split into three parts header data footer The header has a length of 22 octets and contains the most basic information for the communication between the MMI and the simulator The packet type is used to distinguish TM from TC packets OpenSimKit User Manual V3 7 0 73 94 Note Currently only TM packets are used inside the simulator The commands from the MMI to the simulator are still simple strings This will change in future OpenSimkit releases The application ID is used to allow the definition of different kinds of packets which have different data inside Currently it is only possible to define 256 different TM and 256 different TC packets Note It is proposed that an additional field called context should be added to allow more different packets to be defined But this change will be discussed in the forum The sequence counter is used to track the reception of packets It shall be incremented by one for every packet send Each application ID shall have its own sequence counter If the maximum value of the sequence counter is reached it shall overflow to 0 Note Currently the se
24. you find a listener lua and a talker lua program Start them listener first and all you type into the listener will be echoed by the talker as soon as you press lt CR gt gt lua talker lua gt lua listener lua Attempting connection to host Binding to host and port 8080 localhost and port 8080 Waiting connection from talker on Connected Please type stuff empty 0 0 0 0 8080 line to stop Connected Here is the stuff whow it seems to work whow it seems to work Configuring Celestia to visualize the OpenSimKit Rocket Stage After Celestia Lua and the socketlib are installed Celestia must be customized manually to visualize the OpenSimKit Rocket MM opt kde3 share celestia av Y Name v Gr e Datum E data 37 Eintrage 2010 01 07 13 33 ES extras 7 Eintr ge 2010 01 14 01 00 extras standard 5 Eintr ge 2010 01 07 13 33 ES favicons 8 Eintr ge 2010 01 07 13 33 ES fonts 37 Eintr ge 2010 01 07 13 33 E models 68 Eintr ge 2010 01 07 13 33 scripts 5 Eintr ge 2010 01 07 13 33 shaders 44 Eintr ge 2010 01 07 13 33 socket del 1 Eintrag 2010 01 14 00 08 ES splash 1 Eintrag 2010 01 07 13 33 ES textures 5 Eintr ge 2010 01 07 13 33 bookmarks xml 3 3 KiB 2009 06 22 17 44 celestia cfg 13 9 KIB 2010 01 16 23 01 2 2 2 2 2 2 2 2 2 2 2 2 This comprises providing the Rocket geometry and configuring Celestia to invoke the relevant Lua routines They read posi
25. 0 57 94 Finally the matrices comprising different effects can be summarized to one transformation matrix U U 6 N P 11 57 Thus the ECEF position can be obtained with Rycer U Ryo 11 58 As the velocity is the derivative of the position it can be calculated applying the product rule Vieh UV zert UR gcr 11 59 with MO N P _d0 y U ii a N P 11 60 OpenSimKit User Manual V3 7 0 58 94 Part Ill 12 The OpenSimKit Guide Through Galaxy As cited already in section 2 OpenSimKit provides an interface to Celestia 6 for visualizing simulated spacecraft in Orbit in 3D Setting up this interface requires a handful of manual steps but it is manageable for people like Arthur Dent so Don t panic Douglas Adams 8 12 1 Introduction to Celestia Celestia is an astrodynamics software which models the entire solar system with all planets the moons comets major asteroids etc It allows the user to place his viewpoint at an arbitrary position in the solar system and watch bodies moving The user may accelerate simulated time or slow simulation down Celestia also allows visualization of man made objects such as the International Space Station or other famous spacecraft Figure 13 Celestia scene Voyager 2 passing Neptune This feature is used for visualizing objects simulated by OpenSimKit Especially for this purpose the Astris rocket upper stage geometric model was established 12 2 Concept of Interfacing Celestia f
26. 10 30000 will print an error message as the array starts at position 0 seta 02 Pipe qHFlow 9 20 OpenSimKit User Manual V3 7 0 33 94 9 3 10 Shutdown shutdown Stops the simulation and closes the simulator as well as the MMI This command is also available as a menu item File Shutdown 9 3 11 Stop stop Stops a running simulation This command is also available as a menu item File Stop OpenSimKit User Manual V3 7 0 34 94 10 De installing OpenSimKit To de install OpenSimKit simply remove the entire OpenSimKit release directory from your computer i e the osk j X Y Z src directory OpenSimKit does not create any files outside this directory structure OpenSimKit User Manual V3 7 0 35 94 Part Il 11 The Rocket Stage Model Library This section provides an introduction to the physics implemented in the equipment models of the rocket stage simulation library which is included in the OpenSimKit standard distribution This library models a rocket upper stage with a reingnitable engine powered by N204 and MMH The data also fit with sufficient precision for N204 Aerozine 50 oxidizer fuel combinations as it was used by the former ELDO Astris stage Part of the models from this library are descendants from 1 ad were verified with data from the ELDO Astris programme The layout of the propulsion system is shown in Figure 6 co C1 C2 c4 C3 gt f gt cs y lt gt Filter Pa Pressure c8 Regulator C12
27. 20 000 4 17 500 15 000 12 500 7 10 000 7 500 5 000 4 0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 time s 20_ENGINE THRUST Figure 11 Engine model reflecting non ideal oxidizer fluel mix ratios 11 12 2 2 Verification of c all olki 1 The current altitude of the simulation orbit is 600km where the ambient pressure is almost zero So no effects of ambient pressure to the thrust coefficient c can be noticed The value and change of cr becomes important in the lower altitudes especially for first and second stages of launch vehicles For verification of these effects the orbit has been changed to 30km to see the effects of cr For a simulated altitude of 30km cf was 1 8 ISP 300s and thrust 22200 N Whereas for 100km cr was 1 875 ISP 310 99 with a thrust of 23000 N This value is pretty close to the literature value http www astronautix com engines astris htm which says the vacuum ISP is 310 s and thrust is 23000 N for the Astris engine 11 13 The Structure Model The structure is modeled as a point mass with the according forces engine thrust gravity acceleration imposed to it The according S C overall acceleration vector the velocity and position are integrated in ECI coordinates applying 4 order Runge Kutta Integrators OpenSimKit User Manual V3 7 0 56 94 The velocity and position are converted from ECI to ECEE coordinate system by applying source
28. 22 222 EI A are 68 13 2 Using Netbeans Tai nennen AAA AE 68 13 3 How to add a new Dependency to OpenSimKit 4444444ssnnnnn nennen 68 14 Targets of the Ant build xml Tie 69 14 1 Global Targets for both the Simulator and the MMI sese 69 E L en ee ee 69 14 3 Packet Library Targets uni 70 OpenSimKit User Manual V3 7 0 6 94 14 5 SIMUISIOF R Te L a alle 71 13 0penSsimKilArchileelurfe a sie sods as ads la edo ais mada le ad uo ds ai aes ease ecg gt 72 A A T A S EEE INE EE 72 15 2 Model Libraries uti A een 72 153 P cket Library arena 72 154 OSKRackekspeciliealon an nel abiadagutermectsheatyn 73 16 Developing Equipment Models in OpenSimKit uuussssssssennennnnnnnnnnennee nn 75 16 1 Prereguisitesz A A nennen 75 16 2 Writing Ar Java Clas T 75 16 3 Compiling the Java Glass a ee 78 16 4 Modifying the Input Ale coat ereer 78 16 5 Analyzing the Output EIS sans a a 82 LECoding Legs lT L sn naeeetetaecs 83 18 Using the OpenSimKit Logger eeens eer ee eeeesssss renren ernn ennen nenes r nnen e eee 84 18 1 Logger Code Entries for Model Classes sees 84 18 2 Logger Configuration for Simulation Runs eee eee 85 TS EWG LU LA ne AR 86 Annexes 20 OpenSimKit History and Releases sese 90 21 License Trademark and Warranty Disclaimer esse 94 OpenSimKit User Manual V3 7 0 7 94 1 Abbreviations General Abbreviations a m cf e g i e w r t above mentioned confer example given Latin
29. An Academic Simulation Toolkit e OpenSimKit Photo ESO User Manual Software Release 3 7 0 Java Release date 2011 01 21 Editor Jens Eickhoff Authors The OpenSimKit Team www opensimkit org Copyright Information This Manual is published under Copyright of the OpenSimKit development Team Distribution of the software and documentation is granted under the GNU Public License Issue 3 Please also refer to section 21 of this manual Authoring team The following team members have contributed to this manual version 3 7 0 Editor layout didactic concept OpenSimkit introduction tank pressurization controllers and valve models Jens Eickhoff Infrastructure technical chapters Alexander Branat Jens Eickhoff MMI chapter Michael Fritz Engine model chapter Mario Kobald Spacecraft structure model chapter Michael Fritz Ivan Kossev Celestia interfacing recipe Jens Eickhoff Rouven Witt Contents TADO Ts dd aaa nn Eee 8 2 IH LOQU CLONE 9 3 Hardware and Operating System Prerequisites cccccccccccccccnnonnnncnnnnnnnnncnnnnnanancnnnn 11 4 S ltware Dependencies eenen see 11 Part 5 Downloading amp Installing OpenSimKit seeeeneeenennnnnnnen nennen nnnnnnnn nn 14 6 Building OpenSimKit Simulator and MMI Program ccccceeeeeceeeeeeeeeeeeeeeeeeeeeeeeeetess 16 7 Quick Start IFO ATION au naar 16 7 1 Starting Simulation and Vsti e Movi ea ad eld 16 7 2 OPEN III EIA ia de 17 8 St
30. C wall fl And for the part in contact with gas phase m ts T a O mail gas Wall gas wait Wall fl Well gas 1 1 39 m Wall gas C Wall gas m Wall gas C Wall gas OpenSimkit User Manual V3 7 0 49 94 The second term in addition considers the wall mass which comes into contact with the gas per second due to sinking liquid level in the tank compartment 11 8 3 Thermodynamics of the Fuel Tank The equation system for the fuel compartment of the tank is similar to that for the oxidzer compartment For the fuel however the gas phase can be approximated as to consist of pure pressurization gas since the vapor pressure of MMH or similar fuels is considerably low The derivative of the intrinsic energy of the gas phase thus is reflected by U gas m prgas u gas u gas M gas 1 1 40 With u c T H C T gas v gas gas gas v prgas gas Even if the gas phase only is consisting of pressurant for the terms describing gas inflow pressure p volume V temperature 7 and mass m the index prgas is used and for the variables describing the state inside the tank the index gas is used The same applies for material properties such as gas constant So the first law of thermodynamics for the gas phase of the fuel compartment is reflected by m prgas h prgas in T Q gas m prgas Cu prgas T wer m gas C v sd T gas T D gas 4 gas 1 1 4 1 From the generic gas equation Peas er 11 42 m gas R T T via transform
31. High Pressure Bottle Model 4 44 Henne 40 11 3 The Pipe Model a IO 41 11 3 1 Modeling the Pressure Dro i a 222 22 2 eed eur ered ee 41 11 4 The Junction Model sss sese 43 LS The Filter MOGe le een age eta 44 11 6 The Pressure Regulator Model 44 11 7 The Pipe Split MOL 299209 ZR 9 eee ZR YZ 9 ZR e Yd 9 ZR Y eed ZR YE 9 nated Baad EEEE dates 44 11 8 The Propellant Tank Model sss 45 11 8 1 The Differential Equation SystemM ooonooniicnnincniccconnnnconeconococonnancnrnrccnc nn 45 11 8 2 Thermodynamics of the Oxidizer Tank 47 11 8 3 Thermodynamics of the Fuel Tank sese 50 11 8 4 Thermodynamics of the Tanks in Blowdown Mode 51 141 9 The Flow Valve Model caida ida aia 52 11 10 The EngineController Model 52 11 11 The IntervalController Model sees 52 11 12 The Engine Model nat 53 11 1217 IBASICS sa 25822 53 11 12 1 1 Characteristic Velocity ee ee as ee 53 X I N M Thrust Factor Se air 54 11 12 2 Model Verficali n 2 Ra 55 111221 A re Vera ern 55 11 1222 NM CNCA ONO o Ei 56 11 13 The Structure Model acto ee ee an 56 Part Ill 12 The OpenSimKit Guide Through Galaxy sese 60 12 1 Introduction to Gal s ia iii a een 60 12 2 Concept of Interfacing Celestia from OpenSImKIL ee eee eee e eneen 60 12 3 Steps for the Infrastructure Sel p sta 61 Part IV 13 Developing Component Models for OpenSimKit uuuuossssesnnnneeenn nn 68 13 1 Using Eclipse JDT 33 2 2
32. S1StM S1StS S1StL gt l lt entry model 00_HPBottle variable ptotal format 6 6f gt lt entry model 01_HPBottle variable ptotal format 6 6f gt OpenSimKit User Manual V3 7 0 27 94 lt entry lt entry lt entry lt entry lt entry lt entry lt entry lt entry lt entry lt entry lt entry lt entry lt entry lt logOutpu mode mode model L 01_ mode mode model model model model model model model 22_S 22_S 22_S 22_S 22_S 22_S 22_S L 22_S mode t gt L 22_S C EUC C EUC Lruc Lruc Lruc Lruc Lruc Cruc C EUC 00_HPBottle HPBottle ture ture ture ture ture ture ture ture ture variable mftotal format 6 6 gt variable mftotal format 6 6 gt 20_Engine variable 20_Engine variable variabl variabl variabl variabl variabl variabl variabl variabl thrust format 6 6 gt alt format 6 6 gt le scVelocityX format 6 6f gt e scVelocityY format 6 6f gt e scVelocityZ format 6 6f gt e scPositionX format 6 6f gt e scPositionY format 6 6f gt e scPositionZ format 6 6f gt e scPosLat format 6 6 gt e scPosLon format 6 6 gt variabl e scPosAlt format 6 6 gt OpenSimKit User Ma
33. X 0 5 5 Y 241 1 ms 22_STRUCTURE SCPOSITIONZ y __QQ_ gt gt EE5AAAAAAAA A A 22 Output y 24_ATTITUDEDYNAMICS SCQ1 m m Usages pSize int DD oSk 3 SIM sim run x OSK J mmi run x 24_ATTITUDEDYNAMICS SCQ2 AAA z Al 24_ATTITUDEDYNAMICS 5CQ3 Konsole iienaa e Resetting strings 24_ATTITUDEDYNAMICS SCQ4 Console submitted command 24_ATTITUDEDYNAMICS SCPHI Resetting surings 777777777 Console submitted command 24_ATTITUDEDYNAMICS SCTHETA ARMOR aa AA 24_ATTITUDEDYNAMICS SCPSI A Console submitted command Create graph a OSK J N Mm n x a Figure 10 Engine model behavior during throttling with ideal oxidizer fuel mix ratio A first test has been done by letting the engine controller reduce the oxidizer and fuel mass flow and therefore the thrust linearly from the maximum value at start to zero Therefore the oxidizer to fuel ratio stays constant and the c should also be constant as it can be seen in the above picture To show the nonlinear behavior of the engine with changing oxidizer to fuel ratio the engine controller has been set to only reduce the fuel mass flow So the c is nonlinear decreasing from its maximum value at start with optimum oxidizer to fuel ratio to lower values as it can be seen in the following picture The nonlinear decay can also be seen in the thrust diagram OpenSimKit User Manual V3 7 0 55 94 G
34. ach other Unpacking the zip archive leads to the following substructure for binaries libraries and input files within the osk j X Y Z src directory osk j x y z src bin build dependencies janino 2_5_15 junit 4_6 osk j jat min slf4j 1_5 6 src tests models netbeans pkt woodstox 4_0_4 Root directory of the OSK J distribution Location of the jar files of both the MMI and the simulator Location of the ant build script build xml Location of the dependencies needed to compile the MMI and or the simulator An embedded Java compiler needed by logback jfreechart 1_0_12 Location of the jfreechart and jcommon jar file necessary for plotting graphs Location of the JUnit jar file in version 4 6 logback _0_9_15 Logging back end used by OSK J imum_1_0_0 Minimum version of JAT for OSK J Contains only classes necessary for gravity model The logging interface used in OSK J Location of the woodstox jar file in version 4 0 4 Location of libraries needed by the simulator and or MMI and or models MMI source code directory MMI unit test code directory Location of the model libraries Starting with release 2 5 the simulator does not include any simulation model classes Instead it searches for jar files containing model classes in this directory Netbeans free form projects One for each modu
35. ar Make sure you install version 5 1 or higher Now come the bit more clumsy steps but this recipe should navigate the user properly through the jungle even as a beginner Installing the Lua socket library Windows Under Windows XP for Lua 5 1 or higher the luasocket library from 12 is already included in the Lua standard installation described in the paragraph above This comprises the according dll files and lua scripts establishing socket access luasocket 2 0 2 lua 5 1 2 Win32 vc6 lua amp socket ftp lua http lua smtp lua tp lua url lua itn12 lua mime lua socket lua E mime core dil amp socket core dil ua5 1 dll ua5 1 exe No additional steps are required for installation Installing the Lua socket library Linux For some Linuxes such as SuSE 11 2 the socket library is not included by default in the Lua installation rpm So the luasocket library has to be downloaded from 12 and manual installation is required The tar gz archive has to be downloaded and stored into a convenient work directory e g luainstallwork Unpacking the archive will lead to a directory structure such as luainstallwork luasocket 2 0 2 For other Linux variants such as SuSE 11 3 a precompiled RPM packet is available already from the Linux supplier s repositories In such case this luasocket package just is to be installed by the standard package manager of the Linux distribution and the re
36. ation and derivation the temperature gradient results as 3 m oe as T as V as DE ee 11 43 l M gas an For the volume increase of the gas phase in the fuel tank the same equation applies as for the oxidizer compartment Pe V nowt Zn 1 1 44 A OpenSimKit User Manual V3 7 0 50 94 And in a similar approach as for the oxidizer the densitiy of liquid fuel as function of temperature can be approximated by 1 p C DT y 11 45 C and D again are constants The density gradient thus can be expressed by pp DT y 11 46 The first law for the liquid volume reduces to the same equation as 11 34 The heat transfer coefficients again are resulting from 11 36 and 11 37 For the temperature gradients of the tank walls again the formulas 11 38 and 11 39 apply Therewith also for the fuel tank a complete equation set is available which can be rearranged to the form of equation 11 35 11 8 4 Thermodynamics of the Tanks in Blowdown Mode The tank model supports computing the tank physics in blowdown mode when no more pressurization gas is fed in from the high pressure bottles due to closed valves and the rocket stage just is operated until the overall tank pressure has reduced to a certain minimum needed for engine feed Since the gas phases now do not reflect open but closed control volumes now the first law of thermodynamics changes to slightly different equation UO O ga Peas Y gas 11 47 Via rearrangement and insertion of U mc T mc T a
37. ature Sensor At the end the following XML block is inserted replacing the existing elements for the connection named 17_PureGas Basically the Temperature Sensor is inserted between the Models 16 Pipe and 17_Tank lt connections gt lt Begin changes for TemperatureSensor test gt lt connection name 17_PureGas class org opensimkit ports PureGasPort gt lt from model 16_Pipe port outputPort gt lt to model 20_TemperatureSensor port inputPort gt lt connection gt lt connection name 17a_PureGas class org opensimkit ports PureGasPort gt lt from model 20_TemperatureSensor port outputPort gt lt to model 17_Tank port inputPort gt lt connection gt lt End changes for TemperatureSensor test gt lt connections gt Finally the logOutput section has to be modified to print the TemperatureSensor s measured temperature into the output file At the end of the logOutputL section the following XML block is added The attribute model must be the name of the Model here 20 _TemperatureSensor The attribute Variable needs the name of the variable to print into the output file In this case it is the variable temperature Note that the variable written in this place needs at least to be annotated with Readable in the source of the Java class OpenSimKit User Manual V3 7 0 80 94 lt Begin changes for TemperatureSensor test gt
38. cketpropulsion PRegT1 name 08_PReg gt lt variable name description gt lt variable name length unit m gt 1 lt variable gt lt variable name mass unit kg m gt 2 6 lt variable gt lt variable name innerDiameter unit m gt 014 lt variable gt lt variable name specificHeatCapacity gt 900 0 lt variable gt lt variable name pcoeff length 4 gt 24 10245 4462006 1 84912E 3 2 580329E 6 lt variable gt lt variable name temperature gt 300 0 lt variable gt lt model gt Each model definition has the tag model It has the two mandatory attributes class and name The attribute class needs the fully qualified name of the class from which this model will be created In this case it is org opensimkit models rocketpropulsion PRegT 1 It means the class PregT1 from the package org opensimkit models rocketpropulsion The fully qualified class name is necessary because it is used by the OpenSimKit kernel to instantiate an object of the class The attribute name denotes the name of the Model Each Model must have a unique name In the example above the Model s name is 08_PReg The manipulatable variables of the Model are written between the tags of model The variables with the names length mass innerDiameter specificHeatCapacity and temperature are scalar variables They are written in the same way as in the source code of the P
39. co C14 Pressure Difference Regulator C15 Pressure Regulator C17 c21 C19 Flow Control Valve Engine Controller C18 C20 Engine Figure 6 Propulsion System Layout Besides the component models of the pure propulsion system the rocket stage model in addition comprises a structure model and a space environment model to be able to simulate rocket stage flight dynamics in space 11 1 The Helium Gas Model Helium is used frequently as inert gas to pressurize propulsion system tanks which are filled with hydrazine derivates and according oxidizers since these substances are highly reactive However when using Helium as pressure gas its non idealness especially concerning its expansion behaviour has to be considered to compute quantitatively proper results This can be achieved by reflecting in detail the variance of Helium s Joule Kelvin coefficient as function of both pressure and temperature OpenSimKit User Manual V3 7 0 38 94 3 f A x ei K bar y lt 0 68 554 E E T CEES FE aa DEIA SERPS EG S 50 DEE RESET E B se 108 158 2088 258 308 350 p bar Figure 7 Joule Kelvin coefficient of Helium as function of pressure and temperature The Joule Kelvin coefficient of Helium is required to compute its specific enthalpy In the Helium gas model the JKC is modeled by a set of polynomes at 1 bar 20 bar 40 bar etc up to 320 bar which model the JKC as fu
40. code which originally was implemeted as Matlab code at the Institute of Space Systems This code considers rotation precession and nutation which are depicted in Figure 12 Polar motion is disregarded because its effect is minor and can furthermore not be predicted correctly Figure 12 Earth s motion In a first step the UTC time which was committed to the method is converted both to UT1 and to TT Time is needed in these formats for further calculations Afterwards the Greenwich Mean Sidereal Time is calculated by applying GMST GMST J2000 0 86400 UTI yon 11 55 which refers to the Greenwich Mean Sidereal Time in J2000 Consequently the trans formation matrix comprising rotation effects can be calculated cos GMST sin GMST 0 O sin GMST cos GMST 0 11 56 0 0 il In the next step specific angles are calculated by applying correlations With these angles and trigonometric functions the transformation matrix P comprising precession effects is determined In the next step the longitude of the ascending node of the moon is calculated because it has an enormous impact on the Earth s nutation Therefrom both periodical change of the position of the Earth s vernal equinox and periodical change of the obliquity of the ecliptic can be determined Together with the obliquity of the ecliptic at J2000 and trigonometric functions the transformation matrix N comprising nutation effects is calculated OpenSimKit User Manual V3 7
41. d file has to be executed to build the whole simulator like described in the read me 16 4 Modifying the Input File To use the TemperatureSensor inside the simulation the configuration file describing the OpenSimKit User Manual V3 7 0 simulation has to be adapted The configuration file includes the model definition the mesh definition the connections and the logging definition To show the functionality of the TemperatureSensor it is not necessary to create a sample configuration file from scratch It is easier to modify an existing configuration file To do this a copy of the file Rocket Stage Simulation xml with the name Rocket Stage Simulation_sensor xml is created At the end of the models section the lines below have to be appended The fully qualified name of the TemperatureSensor class is org opensimkit models TemperatureSensor and its name is chosen as 20 TemperatureSensor As the TemperatureSensor does not have any variable requiring initialisation in other words no variable annotated by Manipulatable nothing needs to be written in between the model tags Rocket Stage Simulation xml lt models gt lt Begin changes for TemperatureSensor test gt lt model name 20_TemperatureSensor class org opensimkit models TemperatureSensor gt lt model gt lt End changes for TemperatureSensor test gt lt models gt Inside the TankPressurization_sensor xm
42. dencies This is another step away from a simple simulator and towards a simulation framework This separation of the simulator and its models allows users to simply share their model libraries and it makes OpenSimKit more flexible The default OpenSimKit models of a rocket propulsion system are now included in the file osk j rocket propulsion jar in the models subdirectory of the OpenSimKit distribution Those model libraries can be developed almost independent from the simulator They only need the osk j sim jar as compile time dependency because the latter include the interfaces and base classes which are needed to create an OpenSimkit model During start up the simulator is looking for jar files inside the models directory Any jar file found is included in the simulators classpath This is done by the method addModelLibrariesToClasspath of the Class InteractiveMain During the initialization of the simulation when the XML input file is read the Classloader is now able to find the model classes and can load them into the Java Virtual Machine 15 3 Packet Library Note The following section describes work in progress which means that in case of differences between the documentation and the source the source is true Additionally not all concepts described here are already fully implemented and tested OpenSimKit User Manual V3 7 0 72 94 The Packet Library is the core of the communication of the MMI and simulator The Packe
43. e OpenSimKit User Manual V3 7 0 32 94 lt value gt is the value the field should be set to Examples set 00 HPBottle mass 1000 set 00 HPBottle fluid test 9 3 9 SetA seta lt instance gt lt field gt lt position gt lt value gt Sets the value of an element of an one dimensional array lt instance gt is the name of the component instance you want to adress in case a class is instantiated more than once It is case sensitive With the supplied sample files there exist 20 components named 00 _HPBottle to 19 FluidFlowValve However not all have manipulatable variables Use the help command to get a list of all available manipulatable variables lt field gt is the name of the member variable of the instance of which you would like to get its value It is case sensitive The following fields are in the instance O2_ Pipe innerDiameter double variable length double variable specificMass double variable specificHeatCapacity double variable surfaceRoughness double variable temperatures Array of double variable length 10 qHFlow Array of double variable length 10 massPElem double variable pin double variable tin double variable mfin double variable pout double variable tout double variable lt position gt is the position in the one dimensional array lt value gt the value of the element Examples seta 02 Pipe temperatures 0 300 seta 02 Pipe temperatures 9 100 seta 02 Pipe temperatures
44. ed with a given value of 0 94 The isentropic exponent or ratio of specific heats kappa of the combustion gases is also a function of OF and has also been programmed as a polynomial from CEA picture below Isentropenexponent ber O F Kappa Polynomisch Kappa y 7E 07x 0 0001x 0 0034x 0 0324x 0 1493x 0 3251x 1 5018 R 0 9992 0 00 1 00 2 00 3 00 4 00 5 00 6 00 7 00 8 00 11 12 1 2 Thrust Factor c The effect of altitude adaption of the nozzle is integrated with the thrust factor c To provide the ambient pressure a simple atmospheric model has been included http www grc nasa gov WWW K 12 airplane atmosmet html With the formula for the area ratio of the nozzle A Pe 2k pth gt E I l 11 52 with 2k k 1 T kl IV 11 53 k 1 which assumes 1D isentropic adiabatic flow the nozzle exit pressure p is calculated iteratively with the Newton method With the exit pressure p ambient pressure p and chamber pressure p the thrust factor cs can be calculated for each time step A A Pe OpenSimkit User Manual V3 7 0 54 94 If the calculated nozzle exit pressure is to low flow separation can occur Then the value for the thrust may no more valid The criterion of Summerfield is used to check for flow separation in the nozzle pe lt 0 4 p In such case a LOG debug message is created as wa
45. ensitive The following fields are in the instance 02 Pipe innerDiameter double variable length double variable OpenSimKit User Manual V3 7 0 30 94 specificMass double variable specificHeatCapacity double variable surfaceRoughness double variable temperatures Array of double variable length 10 qHFlow Array of double variable length 10 massPElem double variable pin double variable tin double variable mfin double variable pout double variable tout double variable lt position gt is the position in the one dimensional array Examples geta 02 Pipe temperatures 0 geta 02 Pipe temperatures 9 geta 02 Pipe temperatures 10 will print an error message as the first array element is called 0 geta 02 Pipe qHFlow 9 9 3 5 Help help help lt command name gt help lt component name gt help lt simulator information gt The Help Command prints information about the simulator help Invoked without any parameter it prints a list of all available commands help lt command name gt Prints a detailed help about the command help lt component name gt Prints detailed information Manipulatables Readables Callables about the Component help lt simulator information gt Prints specific global simulator information Possible values are Components A list of the names of all Components inside the simulator as well as their type Manipulatables A list of all Manipulatables inside the simulator ordered by classes as
46. figurationFile path to config file implemented in OpenSimKit bat sh starting scripts 2 b name the file logback xml or logback test xml and place it into the classpath logback xml should be used for release settings logback test xml has priority over logback xml and can be used during development lt configuration gt lt root level INFO gt lt appender ref ref STDOUT INFO gt lt appender ref ref STDOUT DEBUG gt lt appender ref ref STDOUT DBGSHORT gt lt appender ref ref STDERR WARN gt lt appender ref ref STDERR ERR gt lt appender ref ref ERRORLOG FILE gt lt root gt lt logger name org opensimkit Kernel level DEBUG gt lt logger name org opensimkit models rocketpropulsion FilterT1 level TRACE gt lt configuration gt OpenSimKit User Manual V3 7 0 85 94 19 Literature 1 2 3 4 5 6 7 8 9 Eickhoff Jens Erstellung und Programmierung eines Rechenverfahrens zur thermodynamischen Erfassung des Druckgas F rdersystems der Ariane L5 Stufe und Berechnung des n tigen Heliumbedarfs zur Treibstofff rderung Study Thesis Institut f r Thermodynamik der Luft und Raumfahrt Universit t Stuttgart Pfaffenwaldring 31 Stuttgart Germany 1988 Eickhoff Jens Modulare Programmarchitektur f r ein wissensbasiertes Simulationssystem mi
47. he fluid flow from one inlets to two outlet flows Neither specific pressure drop effects nor heat transfer effects are considered The model in backiteration steps receives the mass flow boundary conditions requested from the components connected downstream the outlets and splits the inflow value in the according ratio not caring whether the overall inflow rate is sufficient To assure this the sum of the massflows requested at the outlets as boundary conditions is handed over to the next upstrem inlet component The overall iterative boundary condition solving method is described in 3 OpenSimKit User Manual V3 7 0 44 94 11 8 The Propellant Tank Model The combined fuel oxidizer tank is modeled by means of the class TankT1 This model includes a complete implementation of the tank physics DEQ system which models the behaviour over time in both tank compartments The thermodynamic effects modeled is limited to medium energetic fuel oxidzer combinations i e hydrazine derivates as fuel and nitrogen oxides as oxidizers For high energetic fuel oxidizer combinations additional physical effects of cryogenic fluids have to be considered 1 Please note that when looking into the sourcecode lots of variables can be found with slightly cryptic names and 6 characters name length all uppercase This is a heritage from the former FORTRAN77 implementation of the tank pressurization system in 1 The following recipe should be sufficient to trace
48. iguration files to bring everything together All components are available for both Linux and Windows platforms The setup described in the subsequent paragraphs works for both platforms Differences only appear considering the install directories of Celestia and Lua 12 3 Steps for the Infrastructure Setup Installing OpenSimKit At first a Celestia compliant OpenSimKit release has o be installed i e V3 5 0 or higher Please refer to chapter 5 for the according steps Installing Celestia On a lot of Linux platforms Celestia is already installed by default and no installation tasks have to be performed explicitly For the popular Linux implementations such as SuSE or Ubuntu or RedHat precompiled packages are available for installation and do not require Celestia builds from sourcecode The same applies for all MS Windows Platforms from XP onwards In case your operating system does not include a preinstalled Celestia the Celestia homepage and installation root can be found in 7 Just follow the instructions to receive the standard installation which nowadays is V1 6 0 Installing Lua Lua by default is pnot reinstalled on Windows nor on Linux platforms While on Windows platforms you have to install it from the Lua root 10 on most Linux es there are packages OpenSimKit User Manual V3 7 0 61 94 for Lua included in the distributions e g Ubuntu SuSE Use the according installation tool and install Lua via apt get YaST or simil
49. inal double MAXTSTEP 10 0 private static final double MINTSTEP 0 001 private static final int TIMESTEP 1 private static final int REGULSTEP 0 After this part of necessary code follows the only member variable needed for the TemperatureSensor the temperature Choose double as its type and make it private private double temperature Additionally the temperature should be accessible so it can be printed into the result file or inspected during run time However it should not be pre defined by the configuration file or manipulated during run time So it is annotated with Readable Readable private double temperature Now the ports are defined IsPort private Port lt PureGasDat gt inputPort IsPort private Port lt PureGasDat gt outputPort Next a constructor has to be written to allow for the correct instantiation of the TemperatureSensor If just the default constructor is used this class cannot be used as a Model As it is clearly visible basically the parent class constructor is invoked with class specific customizations public TemperatureSensor final String name super name TYPE SOLVER MAXTSTEP MINTSTEP TIMESTEP REGULSTEP OpenSimkit User Manual V3 7 0 76 94 Finally the temperature reading method has to be implemented For this the iterationStep method of the base class is overridden Override public int iterationStep throw
50. ins information about one provider subscriber table entry Containing elements Fehler Referenz nicht gefunden provider subscriber Attributes Attribute Type Required Description provider string yes Fully qualified name of the class from which this connection will be created name string yes Unique name of the connection OpenSimKit User Manual V3 7 0 24 94 8 5 2 ProviderSubscriber Table Section Example A providerSubscriber definition is shown below lt entry name gravityAcceleration gt lt Type double 4 gt lt provider model 23_Environment variable gravAcceleration gt lt subscriber model 22_Structure variable gravityAccel gt lt entry gt Note Vectors like given gravity example are defined as double 4 The first vector element contains the magnitude the other 3 the normalized direction components in the corresponding coordinate system 8 6 mesh for mesh definitions This element contains all information about the meshing of the models Containing elements mesh Attributes Attribute Type Required Description name string yes Unique name of the mesh level string yes The level of the mesh top for the top level mesh and sub for the sub level meshes 8 6 1 meshes This element contains all information about the meshing of the models for the boundary condition solver Containing elements
51. k j sim bat inputfile xml outputfile txt Command line Linux osk j sim sh inputfile xml outputfile txt e The inputfile Rocket Stage Simulation xml is distributed together with the OpenSimkit standard installation comprising the rocket simulation library as OpenSimKit User Manual V3 7 0 16 94 example e The outpuffile is the text file where the simulation will log its output data The selection of what results at which timesteps are to be logged can be specified in the inputfile details see later After the simulation is up and running and is waiting for an MMI to connect the MMI can be started up by Commandline Windows osk j mmi bat 127 0 0 1 Commandline Linux osk j mmi sh 127 0 0 1 7 2 OpenSimKit MMI After the simulation has been started up according to chapter 7 1 e g by osk j sim sh Rocket Stage Simulation xml myOutFile txt and after the simulation MMI has been started according to chapter 7 1 the simulation computation and results visualization can be controlled via the MMI Figure 4 depicts a screenshot of the MMI main window OSK Control Console OA amp Eile Figures E Cmd Window RUN Command successful Run E Log Window cO ptotal 2 7998820028015137E7 c8 tout 300 000061 4626333 c12 tout 300 0000614626333 c15 tout 300 0000614626333 c17 tin0 300 0000614626333 c17 tinl 300 00006122030317 c17 poxt 17 700000789469776 c17 GNwT 287 1499638033914
52. ket upper stage as it is e g used for positioning satellites in highly inclined earth orbits A flowchart of the system is given in Figure 6 Details on this system and its models are given in section 11 of this manual 3 Hardware and Operating System Prerequisites OpenSimkit was tested on Windows XP Vista 7 and diverse Linux platforms It needs at least e the JDK Java Development Kit 1 5 preferably 1 6 now called Java 6 and e Apache Ant 1 7 0 or higher OpenSimkit installs into a user defined directory and does not install any Windows DLLs Linux so libraries or similar Therefore complex package based installation techniques are not required 4 Software Dependencies From release 2 4 6 OpenSimKit onwards now each OpenSimkit release comprises in its installation zip file all necessary dependencies which are required to run the distribution Currently OpenSimkit has the following dependencies e Woodstox 4 0 4 Woodstox is a Stax parser implementation which is needed as the J2SE Runtime Environment JRE 1 5 does not include a Stax parser e SLF4J 1 5 6 The Simple Logging Facade for Java or SLF4J is an abstraction for various logging frameworks OpenSimkit uses it together with Logback e Logback 0 9 15 OpenSimKit User Manual V3 7 0 11 94 The back end used for logging inside OpenSimkit It can be extensively configured e Janino 2 5 15 Janino is an embedded Java compiler needed by logback e Extracts from JAT
53. l more modifications are needed First the meshes section needs to be modified Inside the first mesh a reference to the Temperature Sensor model has to be added This is done by putting the Model name in an element named model The Temperature Sensor has the name 20 _TemperatureSensor It is added at the end just after the Model with the name 19 FluidFlowValve Rocket Stage Simulation_sensor xml lt meshes gt lt mesh name m0 level top gt lt mesh gt mesh_1 lt mesh gt lt model gt 05_Pipe lt model gt lt model gt 06_Filter lt model gt lt model gt 07_Pipe lt model gt lt model gt 08_PReg lt model gt lt model gt 09_Pipe lt model gt lt model gt 10_Split lt model gt lt model gt 11_Pipe lt model gt lt model gt 12_PReg lt model gt lt model gt 13_Pipe lt model gt OpenSimkit User Manual V3 7 0 79 94 lt model gt 14_Pipe lt model gt Vv lt model gt 15_PReg lt model gt lt model gt 16_Pipe lt model gt lt model gt 17_Tank lt model gt lt model gt 18_FluidFlowValve lt model gt lt model gt 19_FluidFlowValve lt model gt lt Begin changes for TemperatureSensor test gt lt model gt 20_TemperatureSensor lt model gt lt End changes for TemperatureSensor test gt lt mesh gt lt meshes gt Next the connections have to be modified to allow for a proper inclusion of the Temper
54. le mmi pkt rpr sim OpenSimKit User Manual V3 7 0 14 94 sim temp work tests Packet Library source code directory Packet Library unit test code directory t propulsion system source code directory Rocket propulsion system unit test code directory Simulator source code directory Simulator unit test code directory Location of the temporarily created files during compilation Location of the simulator input files For the beginner user the work and the build subdirectories are of primary interest to build and start up the software Please see the following sections explaining software build and startup Since software version V3 3 example input files are provided to the user directly in the work subdirectory Furthermore from V3 3 due to distribution file size limits on the hosting server the software and the documentation are split into two downloads From V3 5 onwards a third optional download file is provided containing all elements for the coupling of OpenSimKit to the astrodynamics visualization software Celestia For more details please refer to Part III of this manual OpenSimKit User Manual V3 7 0 15 94 6 Building OpenSimKit Simulator and MMI Program To compile OpenSimKit the program Apache Ant is needed If it is not already present on your system you can download it from http ant apache org Please note that the OpenSimKit build system is
55. m prgas gas 2 1 1 30 m gas m gas The volume of the gas phase continuously increases during engine operation as oxidizer fuid is consumed Thereby two effects are to be considered One is the volume increase through direct oxidizer consumption by the engine i e reduction of mass of liquid oxidizer in the compartment The other effect is the change of oxidizer fluid density due to cold pressurization gas flowing into the tank and the gas phase in the tank cooling down accordingly and thus cooling the liquid oxidizer Thus the volume change can be formulated as Val aut Zr 1 1 31 The density of the liquid oxidizer can be approximated by a polynomial expression like py C DT ET 11 32 with C D and E being constants Thus the density change results as BT D 2ET 11 33 The first law of thermodynamics for the liquid phase volume in the oxidizer compartment of the tank can be expressed as f L 11 34 Mala With the equations 11 19 11 28 11 30 11 31 and 11 34 thus 5 equations are available for computation of the 5 variables OpenSimkit User Manual V3 7 0 48 94 These can be brought into the form A a Te prgas prgas 7 gas gas Tiras Tos F m Pos gas prgas gt Pa F gas 11 35 It has to be noted that the heat fluxes cited in the above equations are sum ups from several effects E g the heat flux imposed onto the gas phase in the tank adds up from heat transferred to the gas
56. mkit since Version 3 7 0 is to determine between physical interaction of models based on real line or pipe interconnections and those which have no direct connection port In the above system diagram there exist physical data lines between the onboard computer and certain satellite equipment Similarly there exist real power lines between satellite equipment the power control and distribution unit PCDU or between PCDU and Battery and Solar Array OpenSimkit User Manual V3 7 0 10 94 Such connections can be modeled via so called port connections which are strongly typed However gravity is computed by the space environment model but there is no plug connection imposing it onto the spacecraft structure Furthermore such abstract parameters might be used by multiple client models gravity might be required by several models To avoid defining fictive line connections between e g environment model and structure as in Simulink OpenSimKit V3 7 0 and higher versions provide a so called provider subscriber mechanism Models computing abstract physical data provide these in according input file table entries and models using them place a subscriber entry To a provided variable there might exist multiple subscribers Models may use different local variable names Variable typechecking is assured The system example provided together with the simulator infrastructure via a m Website represents a modeled re ignitable medium energetic roc
57. nction of temperature The dependency of the JKC at a certain temperature over pressure can be modeled as linear interpolation The specific enthalpy of Helium at a reference pressure of 5 bar can be modeled as polynome h 19846 5 5732 967 T 2 42982T 3 332099 T 11 1 If the Helium state is characterized by another pressure instead of the actual temperature a reference temperature has to be inserted in the above equation This reference temperature is computed by the formula below and represents a state as if the gas were expanded compressed to the target pressure considering its non idealness through the JKC T ep T u p Prep 11 2 This reference temperature then can be entered in formula 11 1 to compute the specific enthalpy of the Helium gas Another topic is the computation of the non ideal behavior of Helium at high pressure levels The deviation from the ideal gas law can be reflected by a compressibility factor Z p ZpRT 11 3 OpenSimKit User Manual V3 7 0 39 94 Where Z 1 0 F xp 11 4 with pressure p is to be reflected in bar and F 1 913688 8 520942 T 1 358845 T 4 595341 T 11 5 11 2 The High Pressure Bottle Model The software class HPBottleT1 represents the high pressure bottles holding the pressurant gas Helium for pressurizing the rocket fuel and oxidizer tank The temperature over time is computed according to the first law of thermodynamics qr QU MTdt _hmdt
58. nd m 0 it results to be PEN Q gas _ D gas V gas sas Mm m C gas v gas gas v gas 11 48 In this equation for the oxidizer compartment for C a the value of the gas mixture from oxidizer vapor and pressurization gas is to be used For the fuel compartment the value of the pure pressurization gas The pressure gradient in the tank results from the differentiated generic gas equation gt m a R ak as m a R as as a 11 49 gas gas Also here for the specific gas constant R here in case of the oxidizer compartment the OpenSimkit User Manual V3 7 0 51 94 value for the mixture is to be applied and for the fuel compartment the value for the pure pressurization gas In blowdown mode the required derivatives to be computed are Do V eas Ta With the equations 11 48 11 49 11 31 and 11 34 as well as with the formulas for the heat transfers 11 36 11 37 11 38 and 11 39 for each tank compartment again a complete equation set is available which can be rearranges into the form of equations 11 35 11 9 The Flow Valve Model The FluidFlowValve is a simplistic representation of a flow control valve lt has a reference mass flow and a reference pressure loss and an analog control line port Depending on the analog signal on the control line between 0 0 and 1 0 the valve sets the fluid flow and pressure loss as linear interpolation accordingly Non linearities are not considered yet 11 10 The EngineController Model The
59. nsimkit org For all code from other libraries included in OpenSimKit like NASA s Java Astrodynamics Toolkit also the GPL applies with one exception Due to inclusion of the Woodstox Stax parser the following license information is to be considered in addition This product includes software licensed under the Apache License Version 2 0 http www apache org licenses LICENSE 2 0 Publishing and use of this software program is done under the assumption that it will be beneficial for the users but WITHOUT ANY WARRANTY even without any implicit warranty on READYNESS FOR MARKETING or the APPLICABILITY FOR A SPECIFIC PURPOSE Details can be found in the GNU General Public License OpenSimkit User Manual V3 7 0 94 94
60. nual V3 7 0 28 94 9 OpenSimKit Command Reference 9 1 How to enter Commands Enter your commands in the command window named Cmd Window in the last empty line and hit the enter key to send the command The commands themselves are not case sensitive however the arguments can be case sensitive Note A subset of the available commands are intuitively accessable via the MMI s pulldown menus 9 2 Short Command Overview These are all currently implemented simulator commands call lt instance gt lt method gt disconnect get lt instance gt lt field gt geta lt instance gt lt field gt lt position gt help resume run set lt instance gt lt field gt lt value gt seta lt instance gt lt field gt lt position gt lt value gt shutdown stop 9 3 Extended Command Description 9 3 1 Call call lt instance gt lt method gt Calls a callable method inside the simulator Currently only parameterless methods are supported lt instance gt is the name of the component instance you want to address in case a class is instantiated more than once It is case sensitive Use the help command to get a list of all available manipulatable variables lt method gt is the name of the method of the instance of which you would like to execute It is case sensitive Examples call cO init OpenSimKit User Manual V3 7 0 29 94 9 3 2 Disconnect disconnect Disconnects the MMI from the simulator 9 3 3 Get
61. ocumentation It is implicitly called by the target mmi javadoc to avoid having inconsistent HTML files mmi test Executes the MMI unit tests mmi clean Cleans the temporary directories as well as the directories containing the jar files of the MMI OpenSimKit User Manual V3 7 0 69 94 mmi run Executes the MMI application jar file 14 3 Packet Library Targets pkt dist Generates the Packet Library This includes the jar file as well as the javadoc documentation pkt build Creates the Packet Library jar file pkt javadoc Removes the old Packet Library javadoc documentation and creates a new one pkt javadoc clean Cleans the javadoc documentation It is implicitly called by the target pkt javadoc to avoid having inconsistent html files pkt test Executes the Packet Library unit tests pkt clean Cleans the temporary directories and deletes the jar file of the Packet Library 14 4 Rocket Propulsion System Targets rpr dist Generates the rocket propulsion system component library This includes the jar file as well as the javadoc documentation rpr build Creates the rocket propulsion system component library jar file rpr javadoc Removes the old rocket propulsion system javadoc documentation and creates a new one rpr javadoc clean Cleans the javadoc documentation It is implicitly called by the target rpr javadoc to avoid having inconsistent html files rpr test Executes the rocket propulsion system uni
62. ow com questions 147454 why is using a wild card with a java import statement bad 147532 e No static imports http www javapractices com topic TopicAction do Id 195 e Only one return e No singletons http code google com p google singleton detector wiki WhySingletonsAreControversial http misko hevery com 2008 08 17 singletons are pathological liars http www xflex cn blog archive 2009 03 why singleton is bad and how to avoid html http blogs msdn com scottdensmore archive 2004 05 25 140827 aspx OpenSimKit User Manual V3 7 0 83 94 18 Using the OpenSimKit Logger 18 1 Logger Code Entries for Model Classes 1 add slf4j imports 2 create one static logger per class named after the class 3 perform all output using the logger do not use System out printin 4 use optimized syntax when dynamically assembling output messages reasoning string is not computed prior to logging call but only if output is actually activated for the specific logger gt performance optimization 5 Rules of writing a message perform no formatting do not add Warning Error prefix or class method information only pure message text Perform Formatting using the config file import org slf4j Logger import org slf4j LoggerFactory public class MyClass private static final Logger LOG LoggerFactory getLogger MyClass class public void someMethod LOG debug a debugging message LOG info some o
63. phase from the outer tank wall from the separation wall and from the warmer liquid oxidizer phase The required heat exchange coefficients are computed via Nu elt equations Thereby the equation for free convection in spherical vessels is used for the heat transfer from the tank walls to the gas phase same as in high pressure bottle model Nu 0 098 Gr Pr 11 36 For the heat transfer between liquid and gas phase the heat transfer equation for a horizontal plate being heated from below is applied Nu 0 14 Gr Pr 11 37 d The tank object distinguishes between outer and separation wall since the separation wall is modeled as 2 layers with half of the real material thickness each One transferring heat into the oxidizer compartment and one into the fuel compartment To avoid a coupling of the oxidizer and fuel compartment DEQ systems and risking the overall DEQ set to become stiff see 3 no heat transfer cross the separation wall is considered Since the temperature ranges in both compartments anyhow are quite close to each other 1 the resulting error definitely can be neglected Finally the equations for the control volume tank wall itself have to be set up Here the convention is that heat transfers from wall to gaseous liquid fluid are counted as positive values For any wall outer or separation and for the part in contact with the liquid phase the following equation applies O wall fl T van gt 11 38 en M wan 0
64. put mass flow at the pipe s input port differ by less than 10 kg sec Using the flow velocity derived by this iteration the Reynolds number is computed and then the friction factor 4 is to be computed Ks A f log Re 7 11 12 OpenSimKit User Manual V3 7 0 41 94 IE E Na S 100A MN PF 4 EL Er A 20 z BR o ll rn zas ee 726 Nikuradse f 1300 Galavics roje aa anale A re o gt sandrauh technisch rauh Nau 15 o 30 un 12 Oo rR RL 7 CEA 4 6 8 193 2 4 6 8 pe 2 4 8 105 2 4 6 8 405 2 Re Gd Figure 8 Moody Diagram Pipe Lambda coefficient as function of Reynolds Number Manually this could be done by interpolating in the Moody diagram for computation purposes an iterative solving of the Colebrook equation is performed 1 VA 2log e D 3 714 2 51 RevA or zla PIs 25 11 13 A AL Ur Heliun U d k 1 66 H Enanz2 007561 8 4 1 8 2 8 L Figure 9 Flow friction coefficient for adiabatic Helium flow in pipe OpenSimKit User Manual V3 7 0 42 94 This approach is based on assuming pipes with TEFLON inliner and covers the transition range between laminar and entirely turbulent flow Purely laminar flows thus are not covered by this approach but since pipe inflow fittings elbow connectors etc will lead to at least partly turbulent flow conditions this implementation approach is valid With the available fluid
65. quence counter is not used in OSK and am not sure how to deal with the inability of Java to have unsigned types This means currently the sequence counter would be between 128 and 127 instead of O and 255 The packet length tells the length of the packet including header and footer The simulated time is used to track the time inside the simulation This is necessary as usually the simulation time is not the same as the local time For easier handling with the Java language it is 8 byte long The system time is used to track the local time This is necessary as usually the simulation time is not the same as the local time For easier handling with the Java language it is 8 byte long The second part contains the user data The definition of the data inside the packet and its position shall be defined beforehand by the sender and receiver For each pair of packet type and application ID there shall at most be only one definition of the user data Note Realistically we need a database could be Apache Derby based or plain XML to easily define the data inside the packets Because now everything must be hard coded inside the MMI and the simulator Any volunteers The third part called footer contains the check sum Calculated from position O to position 22 n 2 In other words from the beginning of the packet to the end of the user data and thus omitting the footer OpenSimKit User Manual V3 7 0 74 94 16 Developing
66. reference pressure drop at a given reference mass flow can be specified in the input file Heat transfer from filter housing to fluid is modeled via the same equations as for the PipeT1 model The filter however is modeled as one block and is not divided into subsections as the pipes are 11 6 The Pressure Regulator Model The PRegT1 class implements a model for dome pressure regulators The output pressure can be specified as polynomial dependent function of the input pressure via according coefficients in the inputfile The gas throttling from input pressure level down to output pressure however again reflects real gas effects of the Helium fluid i e the temperature increase during throttling is computed Throttling first is computed as being adiabatic and thus isenthalpic and heat transfer from regulator housing to pressure gas then is added in a subsequent step Concerning the throttling the model first computes the Joule Kelvin coefficient y of Helium corresponding to the input flow conditions This computation has to be very precise since at least at start of stage operations the Ap is rather significant and deviations in the JK coefficient would lead to errorneous outlet temperatures So the temperature after throttling can be derived as being Ta T OD Pon 1 1 18 The heat transfer is computed in analogy to the method used for the PipeT1 and gas FilterT1 models 11 7 The Pipe Split Model The SplitT1 model serves to split t
67. regT1 class The value of the variable must be compatible with the variable type inside the Java class It is also possible to write additional attributes to this XML tag but they are currently ignored by the OpenSimKit XML parser The variable pcoeff is an one dimensional array lt has the mandatory attribute length which denotes the length of the array The text of this tag includes the values delimited by at least one space OpenSimKit User Manual V3 7 0 22 94 A second example lt model class org opensimkit models rocketpropulsion PipeTl name 02_Pipe gt lt variable name description gt lt variable name length unit m gt 1 5 lt variable gt lt variable name specificMass unit kg m gt 6 lt variable gt lt variable name innerDiameter unit m gt 0085 lt variable gt lt variable name specificHeatCapacity gt 500 0 lt variable gt lt variable name surfaceRoughness unit m gt 1 E 6 lt variable gt lt variable name temperatures length 10 same true gt 300 0 lt variable gt lt model gt The important variable in this example is the temperatures variable As it is visible by the attribute length the temperatures variable is a one dimensional array The interesting thing to know is the same attribute It denotes that all array values are the same and as such there needs only one value to specified The OpenSimKit XML parser automatically initializes the array wi
68. rning by the model Because of the ideal 1D flow with losses an efficiency factor for cs is used with a constant value of 0 99 11 12 2 Model Verification 11 12 2 1 Verification of c i B S tor Run Debug Profile Versioning Tools Window Help ES b Bro m 5 gt G ER e TA lt 25 000 00_HPBOTTLE PTOTAL Y W b gt E C D1_HPBOTTLE PTOTAL 40 x S Engine java x EngineControllerjava x 22500 00_HPBOTTLE MFTOTAL 0 O 20 000 01_HPBOTTLE MFTOTAL 17 500 17_TANK MFINFPG 17_TANK MFINOPG ER EMIR TRTE A 15 000 17_TANK MFOUTFUEL E 12 500 17_TANK MFOUTOXIDIZER 18_FLUIDFLOWVALVE CONTROLVALUE 10 000 18_FLUIDFLOWVALVE MFIN eng 3 500 19_FLUIDFLOWVALVE CONTROLVALUE 19_FLUIDFLOWVALVE MFIN z SN Y 20_ENGINE THRUST 98820028214943E7 2 2 500 9 20_ENGINE CSTAR 2990819525 9317669766707 0 20_ENGINE CF 2940716584267 0 250 500 750 1 000 1 250 1 500 22_STRUCTURE FORCEMAG 62366150216 time s 5528582967817 22_STRUCTURE SCVELOCITYX 5 20_ENGINE THRUST 20_ENGINE CSTAR 22_STRUCTURE SCVELOCITYY 22_STRUCTURE SCVELOCITYZ Krasi 22_STRUCTURE SCPOSITIONX 248 ti Math pow 2 k 1 1 k 1 gt Math pow k 1 k 1 0 5 22 STRUCTURE SCPOSITIONY 249 t2 Math pow oldp 1 k Math pow 1 Math pow oldp k 1
69. rom OpenSimKit Interfacing Celestia from OpenSimKit is done by periodically supplying Celestia about position and attitude data of the spacecraft as being computed in OpenSimKit This is done by writing the position and attitude information onto a socket in OpenSimkit and OpenSimKit User Manual V3 7 0 60 94 making Celestia read from the socket Subsequently the spacecraft geometry is visualized by Celestia at scripted orbit position and in scripted attitude including proper illumination depending on sun eclipse position etc By default Celestia has fixed formulas for computing body movements along orbits and is not prepared to be supplied with position attitude from external However since Celestia V1 5 1 it provides the feature of writing extension plugins in a scripting language called Lua 9 And Lua provides a socket interface library and thus permits interfacing to the OpenSimkit simulator This feature is called scripted attitude respectively scripted orbit position in the Celestia documentation To realize the visualization of the included Astris rocket model as OpenSimKit calculates its position and attitude the following is required e Installed OpenSimKit V3 5 0 or higher e Celestia 1 5 1 or higher preferably 1 6 0 or higher e Lua 5 1 or higher e The Lua socket library 2 0 2 or higher 11 e Anda geometry model of the simulated spacecraft e g the Astris rocket stage e and some Lua routines and Celestia conf
70. ructure of an OpenSimKit XML Input Elle sese eee 20 8 1 OpensimKitG nfigFile r rl 20 A A A N De ri a ee 20 O MOI SR RN a ae 21 8 3 1 model for model definition aee 21 8 3 2 Val ar loa 21 8 3 3 Model Section Example sees 22 A O 23 O A tae aad Sea eas in ce ee ea e Gas 23 8 4 2 Connection Section Example see 24 8 5 providerSubscriberTable ccccccccccceeeeeeeeeeeeeeeeeeeecsseececeeeecauasseeeeeeeeeeeeeceeeeeeeeees 24 So ig FEN 24 8 5 2 ProviderSubscriber Table Section Example eee 25 8 6 mesh for MOSK STING ONS sad chs cts cha Keen 25 8 0 1 Meses E E E a a a da 25 8 6 2 Mesh Section Example eee eee 25 Bd NOG DUI aa totor tte 26 IA dr ed ci da ll 27 8 7 2 LogQutput Section Example sss eee 27 9 OpenSimKit Command Reference una sea lea 29 9 1 HOW to enter R ennn 29 9 2 Short Command Overview eee eee eee 29 9 3 Extended Command Description 00044444444400000n00Rnnn nennen nenn nennen nen 29 IB Cala daa oca 29 9 32 DISCOMMO e A ea en eh eh ee 30 EL me ma ee Dee ae A a a aed 30 O a EHLERS ee EHLERS EIFEL eee tree ner eee ee 30 9 SG AGNI sence Oacveuee RR e a occlu a E A EO EE EY 31 93 6 Resume aji 32 A a e ee ee e a E rT ee ER 32 A a Si ai a Rasa 32 II a re ee ee ae en u ae ee 33 9 210 SHULHOWN A re 34 OOO Dee ea ee Ll tn 34 19 De installing OpensimKii essen 35 Part Il 11 The Rocket Stage Model UDan 38 11 1 The Helium Gas Mode prin si A A A nd 38 11 2 The
71. s IOException PureGasDat indat inputPort readFromPort temperature indat temperature outputPort writeToPort indat return 0 The complete listing of the TemperatureSensor Model TemperatureSensor java package org opensimkit models import java io IOException import org opensimkit BaseModel import org opensimkit ports PureGasDat import org opensimkit manipulation Readable public class TemperatureSensor extends BaseModel private static final String TYPE TemperatureSensor private static final String SOLVER none private static final double MAXTSTEP 10 0 private static final double MINTSTEP 0 001 private static final int TIMESTEP 1 private static final int REGULSTEP ll o OpenSimKit User Manual V3 7 0 77 94 Readable private double temperature IsPort private Port lt PureGasDat gt inputPort IsPort private Port lt PureGasDat gt outputPort public TemperatureSensor final String name super name TYPE SOLVER MAXTSTEP MINTSTEP TIMESTEP REGULSTEP Override public int iterationStep throws IOException PureGasDat indat inputPort readFromPort temperature indat temperature outputPort writeToPort indat return 0 16 3 Compiling the Java Class In current software releases it is necessary to compile the entire simulator to include the new model The Ant buil
72. s on the right Enter a Project Name for example OSK J and as Project Folder choose the one where you placed your copy of the OSK J sources The Build Script Name build xml should be left alone Click Next gt to continue 13 3 How to add a new Dependency to OpenSimKit To be described OpenSimKit User Manual V3 7 0 68 94 14 Targets of the Ant build xml file To build selected applications of OpenSimKit instead of the entire OpenSimKit suite different distribution targets can be accessed individually E g for building the simulator only after some code changes the user can rebuild it by typing ant sim dist into the terminal console presuming the terminal root directory is the build subdirectory of the OpenSimkit distribution 14 1 Global Targets for both the Simulator and the MMI all This target generates the MMI and the simulator distribution as well as the sample fluid system component library This includes the jar files as well as the javadoc documentation clean This target cleans the temporary directories as well as the directories containing the jar files of the MMI the simulator and the fluid system component library 14 2 MMI Targets mmi dist Generates the MMI distribution This includes the jar file as well as the javadoc documentation mmi build Creates the MMI jar file mmi javadoc Removes the old MMI javadoc documentation and creates a new one mmi javadoc clean Cleans the javadoc d
73. st of this paragraph can be skipped OpenSimkit User Manual V3 7 0 62 94 doc 5 etc E samples E src E test config LICENSE luasocket sin mime vcproj NEW README socket vcproj Go into the directory with a text console and initiate the make command This will compile some c sources from the src subdirectory and install the binaries as well as a number of lua files from the etc directory onto your computer Having fulfilled these tasks you are ready to run the application However some additional steps are provided below to verify that the Lua sockets are properly installed and working First the proper installation of the lua libraries into the relevant directories can be checked Please note that on Linux the target hardware dependent files are stored in a different subdirectory than the target hardware independent ones So there should be a folder structure like usr local lib core so amp socket core so For the target hardware independent files the structure should look like usr local share lua 5 1 amp socket ftp lua http lua smtp lua tp lua url lua Itn12 lua mime lua socket lua OpenSimKit User Manual V3 7 0 63 94 The Linux download comes with several example files Two of them can be used for an intuitive and simple test To verify that the sockets are properly working start two text consoles and navigate to luainstallwork luasocket 2 0 2 samples There
74. sualized by a geometry 3d file called Astris3 cmod and lua files for orbit and attitude computation The for Celestia maindir comprises all stuff to be placed in the min directory The structure is as follows for Celestia maindir 5 lua E socket Itn12 lua mime lua socket lua celestia cfg luahooksocket lua start cel The figure shows the lua directory which contains all the lua routines for the sockets again It is a copy of the installation from the socket library since Celestia wouldn t be able to find them in the original installation location Another important file is the start cel It is a modification of the original start cel script coming with the Celestia installation This file contains the settings that at the start up Celestia sets view and focus to the initial position of the Rocket See lines 25 40 of the file for further details The delivered celestia cfg is a modification of the original file There is the new entry LuaHook luahooksocket lua OpenSimKit User Manual V3 7 0 65 94 It tells Celestia that there are Lua extension scripts to be used and that the main Lua routine is luahooksocket lua luahooksocket lua generates the communication socket instance in Lua and connects to socket 1520 which OpenSimKit writes the spacecraft position and attitude information on After the connection has been established Celestia periodically reads the provided data to be used by the Rocket s attitude lua and orbi
75. t Library consists of two parts The interfaces in the package org opensimkit packet and one sample implementation named OSKPacket in the package org opensimkit oskpacket This separation is helpful to separate the interface from the implementation If the OpenSimKit kernel only uses the interfaces then it is possible to exchange the current implementation which is called OSKPacket by a different yet compatible one 15 4 OSKPacket specification After reading this section please take also a look at the Packet Library javadoc An OSKPacket is a binary chunk of data which contains either information from the simulator to the MMI this is called telemetry TM or information from the MMI to the simulator this is called telecommand TC An OSKPacket has the following structure one octet is defined to be eight bits Offset Size Name Remarks octets octets 0 1 Packet type Identifies a packet as telemetry or telecommand packet 1 1 Application ID Used to address different applications 256 different applications can be addressed 2 1 Sequence A sequence counter to have a facility to detect lost counter packets Each application shall have its own sequence counter 4 2 Packet length The packet length including header and footer checksum It can be equal to MAX_PACKET_SIZE at most 6 8 Simulated The time of the simulation This is in the default Java time time format which is Unix
76. t erweiterter Anwendbarkeit in der Entwicklung und Betriebs berwachung verfahrenstechnischer Anlagen Dissertation der TU Hamburg Harburg VDI Fortschrittsberichte Reihe 20 Nr 196 VDI Verlag 1996 Germany ISBN 3 18 319620 4 Eickhoff Jens Simulating Spacecraft Systems Springer Verlag Berlin Series Springer Aerospace Technology Vol 1 ISBN 978 3 642 01275 4 http opensource gsfc nasa gov projects JAT JAT php and http jat sourceforge net G Engeln Muellges F Reutter Formelsammlung zur numerischen Mathematik mit Standard FORTRAN 77 Programmen 5 Aufl B I Wissenschaftsverlag Bibliographisches Institut Mannheim Wien Zuerich 1986 Laurel Chris http en wikipedia org wiki Celestia http www shatters net celestia Adams Douglas The Hitchhikers Guide to the Galaxy Pan Books UK 1979 lerusalimschy Roberto Programming in Lua Lua org December 2003 ISBN 85 903798 1 7 OpenSimKit User Manual V3 7 0 86 94 10 http www lua org 11 Nehab Diego LuaSocket http www tecgraf puc rio br diego professional luasocket 12 http luaforge net projects luasocket OpenSimKit User Manual V3 7 0 87 94 Annexes 20 OpenSimKit History and Releases Release Date Changes 0 1988 Simulation of a rocket tank pressurization system in FORTRAN7 7 see 01 Jens Eickhoff 1 0 1996 ObjectSim 2 0 3 from 02 being the predecessor of OpenSimKit
77. t lua Running OpenSimKit and Celestia After the installationi s finished OpenSimKit can be run with Celestia visualizing the Rocket Start the OpenSimKit simulator and MMI as usual As soon as the simulation is running start Celestia Enjoy the magnificent view from The Restaurant at the End of the Universe onto the flying rocket stage Status Live from OpenSimKit Folge Rocket Geschwindigkeit 0 00000 m s FOV 26 58 45 9 1 00 Figure 14 Rocket stage over North America Moon in the background OpenSimKit User Manual V3 7 0 66 94 Part IV 13 Developing Component Models for OpenSimKit The preferred method is to use the Eclipse Java Development Tools JDT Create a new Java Project from existing source Use the OpenSimKit directory in the source zip file as a base The class org opensimkit InteractiveMain is the main entry point for OSK J SIM The class org opensimkit console OSKConsole is the main entry point for OSK J MMI 13 1 Using Eclipse JDT 3 3 2 Go to File New Project New Java Project Enter a project name obviously you could use OSK J as project name Under Contents check Create project from existing source and browse for the directory where you placed your copy of the OSK J sources Click Next gt to continue 13 2 Using Netbeans 6 1 Go to File New Project in the following dialog choose Java from the categories on the left and Java Project with Existing Sources from the project
78. t of the results of V2 6 0 the 1st OpenSimKit Developers Weekend Mario Kobald Artur Bohr Universit t Stuttgart OSK J May 2009 Introduced named ports and reworked the XML V2 6 5 input file Alexander Branat OSK J June 2009 Introduced logging into the simulator and the model V2 6 7 library Timm Pieper OSK J July 2009 Release with fluid flow valves for engine fuel and V2 7 0 oxidizer flow control as well as an engine controller steering these flow valves Entire system thermodynamics revised to be robust against engine shutoff flows 0 0 and re ignition Jens Eickhoff OSK J August 2009 This release comprises essential results from the V3 0 0 1st OpenSimKit Developers Weekend It completes the rocket simulation by a simplistic Structure Model and includes the realistic Earth Gravity model from the Java Astrodynamics Toolkit JAT This allows first orbit simulations around Earth including delta V effects Mario Kobald Artur Bohr Claas Ziemke Universitat Stuttgart Jens Eickhoff OSK J September 2009 Further results from the 1st OpenSimKit V3 1 0 Developers Weekend have been added This release comprises the plot visualization of simulation results Michael Fritz Universitat Stuttgart OSK J November 2009 First results from the 2nd OpenSimkit Developers V3 2 0 Weekend have been added Enhanced S C dynamics model computing positions amp velocities now both in Earth centered inertial frame coordinates in Earth centered Earth
79. t tests OpenSimKit User Manual V3 7 0 70 94 rpr clean Cleans the temporary directories and deletes the jar file of the rocket propulsion system 14 5 Simulator Targets sim dist Generates the simulator distribution This includes the jar files as well as the javadoc documentation sim build Creates the simulator jar files sim javadoc Removes the old simulator javadoc documentation and creates a new one sim javadoc clean Cleans the javadoc documentation It is implicitly called by the target sim javadoc to avoid having inconsistent html files sim test Executes the simulator unit tests sim clean Cleans the temporary directories as well as the directories containing the jar files of the simulator sim run Executes the simulator application jar file OpenSimKit User Manual V3 7 0 71 94 15 OpenSimkit Architecture This chapter describes the OpenSimKit architecture the subsystems on which OpenSimkit is founded as well as the general intentions during the design of OpenSimkit 15 1 Subsystem OpenSimkit consists of the following subsystems e core commanding components manipulation ports steps xml 15 2 Model Libraries Since release 2 5 OpenSimKit no longer bundles any simulation models directly in the osk j sim jar file Instead it supports a concept of so called model libraries Model libraries are simple jar files containing the compiled class files of any number of models as well as their depen
80. tegrated into the default simulation At first a new Java class is created with the name TemperatureSensor in the package org opensimkit models If an IDE is used for development it is necessary to make sure that the new Java source file is located in the package org opensimkit models If a plain text editor is used the new Java source file needs to be located in the directory rpr src org opensimkit models To make this class an OpenSimKit Model it has to implement the Model interface The Model interface covers two basic methods which are needed by the simulator kernel Additionally it acts as a marker interface for the manipulation subsystem to enable advanced operations on models To make this class an OpenSimKit Model it is possible to add implement Model at the class definition Another possibility is to derive the TemperatureSensor from the abstract base class BaseModel which implements not only Model but also lot s of convenience members and methods for the current OpenSimkit Model programming model public class TemperatureSensor extends BaseModel Currently a Model needs a set of specific code for interaction with the numerical solver This includes a set of static member variables which can be different for each Model OpenSimKit User Manual V3 7 0 75 94 private static final String TYPE TemperatureSensor private static final String SOLVER none private static f
81. tes Attribute Type Required Description class string yes Fully qualified name of the class from which this model will be created name string yes Unique name of the model 8 3 2 variable This element contains all information to initialise one model variable Containing elements none Attributes Attribute Type Required Description description string no Contains a description of this variable length positive no Specifies the size of the array Necessary if this integer variable is an array The array counting starts with zero name string yes Unique name of the model same boolean no Specifies that all array elements are the same This avoids unnecessarily repeating the same value for each element of an array OpenSimKit User Manual V3 7 0 21 94 state string no Used to describe if this variable is an input or output variable unit string yes Contains the unit of the variable 8 3 3 Model Section Example A model definition is shown here lt model class fully qualified Classname name name of this model gt lt variable name variablel gt value lt variable gt lt variable name arrayVariablel length 3 gt valuel value2 value3 lt variable gt lt variable name arrayVariable2 length 4 same true gt value lt variable gt lt model gt An example lt model class org opensimkit model ro
82. th the correct values and frees the user from unnecessary writing ten times the same value into the configuration file 8 4 connections This element contains all information about the connections between the models Containing elements connection Attributes none 8 4 1 connection This element contains all information about the initialisation of one model instance Containing elements Fehler Referenz nicht gefunden Fehler Referenz nicht gefunden Fehler Referenz nicht gefunden Attributes Attribute Type Required Description class string yes Fully qualified name of the class from which this connection will be created name string yes Unique name of the connection OpenSimKit User Manual V3 7 0 23 94 8 4 2 Connection Section Example A connection definition is shown below A connection definition is shown here lt Connection of Pipe to Filter gt lt connection name 05_PureGasDat class org opensimkit ports PureGasPort gt lt from model 05_Pipe port outputPort gt lt to model 06_Filter port inputPort gt lt connection gt 8 5 providerSubscriberTable This element contains all information about variable interchange between models which is not subject to transfer via modeled real electrical connections fluid pipes or similar between the models Containing elements entry Attributes none 8 5 1 entry This element conta
83. the individual user This development lead to the current issue and the former C version meanwhile is deprecated and removed from the webpage For historic milestones please also refer to the web page and section 20 OpenSimkit is open source software and can be down loaded for free from www opensimkit org For topics of license warranty and trademark of OpenSimkit please refer to section 21 As being based on Java OpenSimkit runs on most computer platforms and a large variety of operating systems The development team always verifies proper functionality on MS Windows and on 32Bit and 64 bit Linux systems The current versions OpenSimKit OSK consist of two separate programs intercommunicating via 2 sockets e the simulator osk j sim and e the graphical man machine interface osk j mmi B OSK Control Console common triton k j 3 1 0 srciwork Befehisfenster Konsole _ O X Sitzung Bearbeiten Ansicht Lesez en Einstellungen Hilfe Befehisfenster as Befehisfenster Figure 1 MMI console window left and simulator console right plus MMI main window Both programs are started from ASCII consoles independent of the operating system used on the host computer The simulator process during run reports certain progress OpenSimkit User Manual V3 7 0 9 94 information e g actual time to the ASCII console but the simulator does not open up any further graphics window The MMI opens
84. tion and attitude data from the socket to which OpenSimkit transmits them For this purpose a Celestia Files package can be downloaded from the OpenSimkit webpage for OpenSimKit V3 5 0 or higher This package contains all files required to configure Celestia Please note that for Linux you ll need to activate your shell or filebrowser in administrators mode sudo to have the appropriate write permissions to the Celestia main directory The figure above shows the Celestia main directory as an example for a Linux KDE system There are a number of files plus the extras subdirectory to be mentioned The Celestia Files package from the OpenSimKit webpage contains two subdirectories One of them contains files to be placed inside the Celestia main directory and the other one OpenSimkit User Manual V3 7 0 64 94 contains files to be put into the Celestia extras subdirectory File installation can be done just by copying the files from the OpenSimKit package into the according Celestia locations Celestia Files E for Celestia extras dir E for Celestia maindir The for Celestia extras dir directory comprises all files concerning the Rocket model visualization The substructure should appear as follows 8 for Celestia extras dir amp Rocket E models Astris3 cmod amp textures attitude lua Rocket ssc The main files to be mentioned are the Rocket ssc telling Celestia that there is a spacecraft called Rocket vi
85. tructure of an OpenSimKit XML Input File The simulation input files consist of the following five sections system models connections meshes logOutput Which shall be described briefly on the following pages To avoid this section to become too theoretic please in parallel have a look at one of the provided xml input files included in the work subdirectory 8 1 OpenSimKitConfigFile The root element of an OpenSimKit XML configuration file Containing elements system models Fehler Referenz nicht gefunden meshes logOutput Attributes Attribute Type Required Description xmins string TBD TBD xmins xsi string TBD TBD xsi schemaLocation string TBD TBD 8 2 system This element contains all information about the simulator setup Containing elements The section system of the input files consists of three subsections e Sysdesc e RunSettings e SimulationCtrl Attributes TBD OpenSimKit User Manual V3 7 0 20 94 8 3 models The models section is used to specify the Models which are used in this particular simulation For each Model a separate subsection is created This subsection contains information for the particular Model Containing elements model for model definitions Attributes none 8 3 1 model for model definitions This element contains all information about the initialisation of one model instance Containing elements variable Attribu
86. utput for the user LOG warn a warning message LOG error an error message LOG error an exception will be raised new java io IOException System out println some output do not use this LOG debug Entry number i is String valueOf entry i OG info Entry number i good practice for 1 argument LOG warn Entry number is i String value0f entry i good practice for 2 arguments LOG error Value was inserted between and new Object newVal below above good practice for gt 2 arguments when nr of is higher than arguments it is printed plainly when nr of is less than arguments additional arguments are ignored OpenSimKit User Manual V3 7 0 84 94 18 2 Logger Configuration for Simulation Runs If no custom configuration is provided a default configuration is used General logback default e logging output to be directed on the console e log level DEBUG OpenSimkit default e level INFO e INFO output to console stdout and logfile located at execution path usually osk j src work e WARN output to console stderr e ERROR output to console stderr Logging properties level destination and format can be configured on a per class basis inheritance through package hierarchy 1 Create a logback xml configuration file 2 a use the following option when executing the program java Dlogback con
87. well as their type Readables A list of all Readables inside the simulator ordered by classes as well as their type OpenSimKit User Manual V3 7 0 31 94 Callables A list of all Callables inside the simulator ordered by classes Version Prints the version of the simulator Examples help help get help 00 HPBottle help components help manipulatables help readables help callables help version 9 3 6 Resume resume Resumes a stopped simulation This command is also available as a menu item File Resume 93 7 Run run Starts a simulation This command is also available as a menu item File Run 9 3 8 Set set lt instance gt lt field gt lt value gt Sets the value of a manipulatable variable lt instance gt is the name of the component instance you want to adress in case a class is instantiated more than once It is case sensitive With the supplied sample files there exist 20 components named 00_HPBottle to 19 FluidFlowValve However not all have manipulatable variables Use the help command to get a list of all available manipulatable variables lt field gt is the name of the member variable of the instance of which you would like to get its value It is case sensitive The following fields are in the instance 00_HPBottle mass double variable volume double variable specificHeatCapacity double variable ptotal double variable ttotal double variable fluid String variabl
88. xpansion is presumed the compressibility factor is computed and the resulting non ideal pressure is compared against the assumption The pressure value is iteratively corrected until the precision is better than 5x10 The adequate equation to model thermal heat transfer between pressure gas and bottle wall is the one for free convection in sperical containments Nu 11 10 With Nu 0 098 Gr Pr 11 11 11 3 The Pipe Model The PipeT1 model reflects a gas flow through a pipe considering friction effects and heat transfer from pipe wall to fluid Considering heat transfer to environment the pipe is modeled to be ideal adiabatic 11 3 1 Modeling the Pressure Drop To compute the pressure drop first the flow velocity inside the pipe has to be identified Therefore first the so called critical velocity of the flow is computed which depends on the in flow gas temperature and is received via the input port of the pipe model The flow velocity is computed in an iterative way e First a velocity is assumed therefrom using the critical velocity the Laval number is derived and then using the formulas for adiabatic gas expansion the pressure and temperature of the gas are derived e Then using the Helium gas model the gas density is computed considering again non ideal gas And therewith the mass flow through the pipe can be identified e Then the presumed input flow velocity is iteratively adapted until the derived mass flow and the in
89. y Solution of the DEQ system at time t Y 1 f t Y 1 Y n 4 11 20 Y n f t Y 1 Y n OpenSimKit User Manual V3 7 0 45 94 where Y 1 to Y n represent the values of the right side of the DEQs i e the derivatives of the dependent variables The integration of this DEQ system Y t dt Y t f Y 0 at 11 21 is performed by a class called DEgSys which is part of the simulator kernel package not the rocket propulsion library This integrator also historically stems from 1 and uses a Runge Kutta method of 4 5 order taken over with minor adaptations from 5 A detailed algorithm description can be found in this cited literature The variable list of the DEQ system 11 21 is listed below t Time Y 1 Mass of pressurization gas in oxidizer tank compartment Y 2 Temperature of gas phase in oxidizer tank compartment Y 3 Volume of gas phase in oxidizer tank compartment Y 4 Pressure in oxidizer tank compartment Y 5 Temperature of liquid oxidizer Y 6 Temperature of outer wall of oxidizer tank in contact with gas Y 7 Temperature of outer wall of oxidizer tank in contact with liquid Y 8 Temperature of separation wall of oxidizer tank in contact with gas Y 9 Temperature of separation wall of oxidizer tank in contact with liquid Y 10 Pressure in fuel tank Y 11 Mass of pressurization gas in fuel tank Y 12 Temperature of gas phase in fuel tank Y 13 Temperature of liquid in fuel tank Y 14 Volume of gas phase in

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