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6 Degree of Freedom Splash Pattern Generation Tool

1. Line Contents 1 Must contain the pneumonic CG 2 Must contain at least 2 but no more than 24 numeric arguments These arguments are the masses kg numbers for which the centers of gravity see line 3 are valid for 3 Must contain at least 2 but no more than 24 numeric arguments These arguments are the centers of gravity corresponding to the masses listed in line 2 4 Must contain the data block termination string A sample center of gravity data block is shown below While this data block indicates a simple linear relationship between a launch mass and a burnout mass there is no reason why a more complex relationship could not be used CG DBZ 9545 Mass 12 0 11 4 CG Dref Center of Pressure Data Block As one may imagine the center of pressure data block contains information on the center of aerodynamic pressure Most simulation packages store a list of centers of pressure CP s for direct use in pitching moment calculations Splash on the other hand uses lists of coefficients of a polynomial that is in turn used to calculate a center of pressure In other words Splash calculates the center of pressure by using an equation of the form 36 CP A B AOA C AOA where CP center of pressure calibers A B C polynomial coefficients AOA angle of attack But while this equation provides a smooth center of pressure movement with a minimum of input requirements it neglects the
2. Line Contents 1 Must contain the pneumonic GENERAL 2 Must contain three numeric arguments In order these arguments are the rocket s launch mass kg length m and reference diameter m 3 Must contain the first line of the staging criterion As stated previously staging criterion will be discussed in detail in a later section of this manual 4 Must contain the second line of the staging criterion 5 Must contain the third line of the staging criterion 6 Must contain the data block termination string A sample general information data block is shown below GENERAL BR 2268 0 13 Mass length diameter Dref AS 6 Staging criterion line 1 G gt 0 Staging criterion line 2 A lt 1000 Staging criterion line 3 Inertial Tensor Data Block While the contents of the inertial tensor data block may be intuitively obvious to some it may not be so obvious to others For those without a background in 6DOF systems the inertial tensor is nothing more than a matrix that contains all the moments and products of inertia for a physical object The vehicle based coordinate system used by Splash for the inertial tensor and everything else is as follows Axis Plain English Equivalent X Forward Y Port left Z Up The format of the inertial tensor is as follows Line Contents 1 Must contain the pneumonic INERT
3. Line Contents 1 Must contain the pneumonic MOTORS 2 Contains a string of up to 240 non white space characters This string is used by the GUI to identify the motor but the 6DOF program logic does not use the string as anything other than a placeholder Which means that this line can not be left blank 3 Contains a single numeric argument This argument represents a delay in seconds after stage separation activation before the motor is ignited Generally this value will be set to zero but users who employ air started motors or significant delays before motor ignition after stage separation will find this feature useful 4 Contains a single numeric argument This argument represents the off centerline distance in calibers of the motor s thrust axis For the 1 motor see diagram of motor configuration this number should always be zero Similarly it should always be non zero for the remaining four motors 5 Contains three numeric arguments These arguments in order are the motor s propellant mass kg sea level total impulse N s and nozzle exit area m 6 Must contain at least 3 but no more than 24 numeric arguments These arguments are 41 a list of times s measured from motor ignition that correspond to thrust values listed in line 7 Note that the first argument should always be 0 7 Must contain at least 3 but no more than 24 numeric arguments These arguments are a list
4. The splash pattern file is perhaps the most significant output file it is what sets Splash apart from other 6DOF codes More to the point the splash pattern file contains a list of every impact point generated by every stage in every scenario simulated It is this data that ultimately determines the 3 sigma circle required of the FAA for a launch license As with all other input and output files used by Splash there is a naming convention associated with splash pattern files All splash pattern files are named by appending spl out to the base filename For example if the base filename is alpha then the corresponding splash pattern file will be named alpha_spl dat Latitude 118 117 9 117 8 117 7 117 6 117 5 Longitude An Excel plot displaying splash pattern data for 1000 flights of a boosted dart Blue diamonds denote impact point for the booster Red triangles denote impact points for the dart Similarly the blue oval represents a 3 sigma oval for the booster while the red circle Assuming the scenario file calls for multiple simulation iterations If only one iteration is requested then no splash pattern file is generated 46 represents a 3 sigma oval for the dart The green dot denotes the launch point Splash pattern files are simple text files containing simple columns of data The format of these columns is as follows Column Description Ru
5. The derivative of the normal force coefficient with respect to angle of attack CP Offset The center of pressure offset The offset is simply a constant that is added to the nominal CP to facilitate stability sensitivity studies Normally the associated value will be 0 0 but suppose the user wishes to model a CP shifted one caliber forward In this case the user would use a CP offset of 1 0 rather than re calculate and re type the entire center of pressure table CP The zero angle of attack center of pressure in calibers dCP The derivative of the center of pressure with respect to angle of attack Fins As the name of this input window implies the Fins input window contains data concerned with fins It should be prominently noted that Splash only uses fin data for yaw pitch roll damping Fin data does not affect lift drag or stability in the normal sense the effects of fins on these vehicle attributes are expected to have been included in the gross vehicle aerodynamics The Fins window is accessed through any of the Vehicle gt Stage pull down menus found at the top of the main Splash window Once opened a Fins window will appear similar to the window shown below Stage 1 Fin Prope m E General Info Number of fins Cant angle deg Area of 1 fin as a mulltiple of Aref Location Fin CP location longitudinal axis cal Fin CP location radial axis cal OK Cance
6. mash 6 Degree of Freedom Splash Pattern Generation Tool Release 1 1 0 2002 Hall Consulting 320 W Felspar Ave Ridgecrest CA 93555 http splashpattern com Forward While the general layout and presentation of knowledge in this text is such that the user may read 1t cover to cover the author doubts that many users endeavor to do so Rather it is expected that this text will primarily be used as reference As a result of this assumption the style of this text is rather stilted it is often short and sweet to a nearly excessive degree The text also repeats itself in several places as it was judged that redundancy of information was preferable to forcing the user to flip through several sections of the User s Manual just to perform or understand one facet of the simulation s operation or use That said this is also a convenient time and place for me to acknowledge those who have influenced me in ways that either made this work happen or made my job easier I would like to thank the following individuals for their encouragement knowledge help and or inspiration as appropriate Mr Ed Brown Mr Ray Calkins Mr David McCue Mr Tom Rouse Dr Ned Smith Mr Rick Wills Table of Contents INTRODUCTION RE 4 WHAT SPLAS S Si tb pitt 5 WHAT SHARE IN ia cdi 6 AILO D EE 7 EA EE 7 AIMOSPhere inici pai titi ee 7 Vehicia AS A A AS A AS AA AE add 7 INSTALLATION lr aia aliado 10 THE GULAPPLICATION WEE 11 ENTREE EE 12 IN
7. s been around the block enough times to do an adequate job mm 3 Se e La a a a ar ab at 5 aa The author aboard a gen u ine made in theUSSR SA 2 Guide Line 54 Glossary 3 sigma circle Axial force Azimuth Base drag Ca CATO Cb Center of gravity Center of pressure Cn Drag Dynamic pressure Elevation Ignition failure Lift Moment of inertia Normal force Pitch Product of inertia Q Roll Specific impulse Splash pattern Total impulse WGS 84 Yaw Zipper An imaginary circle or oval on the ground that encircles all potential impact points of a given vehicle to three standard deviations The aerodynamic force acting along the longitudinal axis of a flight vehicle At zero degrees angle of attack axial force is equivalent to drag An arc of the horizon measured between a fixed point and the vertical circle passing through the center of an object In astronomy and navigation azimuth is usually measured clockwise from the north point through 360 degrees of rotation The component of a vehicle s total drag that is due to aerodynamic effects at the aft end of the vehicle The axial force coefficient The catastrophic failure of a rocket motor usually characterized by the failure of the motor casing The base drag coefficient The location on a finite body through which the centroid of gravitational forces acting on that body passes The location on a finite body throu
8. 0 0 0 2375 229 O DO O le3 Zei bei 10e3 20e3 21e3 1 2 3 5 20 25 25 Stage Files Stage data files describe all parameters that are included within the vehicle itself This includes all aerodynamic and propulsion performance as well as information regarding staging and recovery If a full up rocket incorporates more than one stage then a stage data file is required for each stage The maximum number of stages is 3 Stage data files are identified by a file extension of stg but the naming of a stage data file is not just a matter of appending stg to the base file name as would be expected given the naming conventions of the scenario and splash data files Rather the stage number and stg must be appended to the base file name In other words if the base file name is alpha the corresponding stage data file for a first stage must be named alphal stg Similarly the stage data file for the second stage is alpha2 stg and the stage data file for the third stage is Alpha3 stg As with the scenario data file a stage data file is further subdivided into data blocks These data blocks may appear in any order within the stage data file but all must appear The format of each of these data blocks is discussed below in alphabetical order Axial Force Data Block As one may imagine the axial force data block contains information on the thrust off axial force Most simulation packages store a list of axial for
9. N generated by motor 4 Thrust5 Thrust N generated by motor 5 Propl Propellant kg remaining in motor 1 Prop2 Propellant kg remaining in motor 2 Prop3 Propellant kg remaining in motor 3 Prop4 Propellant kg remaining in motor 4 Prop5 Propellant kg remaining in motor 5 48 Appendices 49 Tips and Tricks This portion of the manual is nothing more than a listing of tricks a user may employ to model vehicles or situations that may not be obviously supported by Splash Dual Deployment Many high altitude vehicles employ a 2 stage recovery system That is to say that they deploy a very small drogue chute at high altitude followed by the deployment of a large parachute at low altitude While Splash does not directly support such systems it can be tricked into modeling such systems provided that they are 2 stage or less vehicles How 1 Set up the input data files windows normally Set the final stage s recovery criterion such that the deployment occurs at the same moment that it 1s wished for the drogue chute on the dual deployment system to deploy The recovery system properties for this stage should match those of the drogue chute 3 Set the final stage s staging criterion such that the stage separates at the same moment it is desired for the main chute on the dual deployment system to deploy 4 Create a new final stage This stage does not exist in reality it only exists in the m
10. normal force coefficient degrees A B C polynomial coefficients AOA angle of attack But while this equation provides a smooth normal force curve with a minimum of input requirements it neglects the fact that normal force coefficients depend on Mach number For this reason Splash employs not one set of coefficients but a family of coefficients The format for the axial force data block is as follows Line Contents 1 Must contain the pneumonic CN 2 Must contain the normal force multiplier This is a number by which the final normal force is multiplied Usually the value of this number is 1 0 but any number can be used in the course of sensitivity studies For example if the user wishes to increase normal force by 10 in an attempt to see what would happen he need only input 1 1 as the multiplier rather than generate a new drag curve Must contain at least 2 but no more than 24 numeric arguments These arguments are the Mach numbers for which the normal force coefficients see lines 4 6 are valid Must contain at least 2 but no more than 24 numeric arguments These arguments are the Oth order normal force coefficients corresponding to the Mach numbers listed in line 3 Must contain at least 2 but no more than 24 numeric arguments These arguments are the Ist order normal force coefficients corresponding to the Mach numbers listed in line 3 Must contain at least 2 but no more than 24 nu
11. 2Longitude Longitude of the om stage impact point in degrees A negative angle corresponds to West longitude 2Latitude Latitude of the 2 stage impact point in degrees A negative angle corresponds to South latitude 3Longitude Longitude of the EW stage impact point in degrees A negative angle corresponds to West longitude 3Latitude Latitude of the 3 stage impact point in degrees A negative angle corresponds to South latitude 25 Splash Pattern alpha 1st Stage Splash Pattern 77 038 77 036 77 034 77 032 77 030 Latitude deg 1st Stage C 2nd Stage C 3rd Stage Print The Splash Pattern window displaying a 100 impact scenario The author concedes however that for presentation quality graphics the user is likely to be better off importing the data from the trajectory file s into a dedicated data processing application or spreadsheet Latitude 118 117 9 117 8 117 7 Longitude An Excel plot displaying splash pattern data for 1000 flights of a boosted dart Blue diamonds denote impact point for the booster Red triangles denote impact points for the dart Similarly the blue oval represents a 3 sigma oval for the booster while the red circle represents a 3 sigma oval for the dart The green dot denotes the launch point 26 Trajectory Data Files Window Splash generates anywhere from two to four trajectory files These files contain the flight parameters for the n
12. associated with different objects they are otherwise identical All are text files All share the same collimated data structure The format of the data found in these files is as follows Column Description Time Total time elapsed since beginning of simulation Longitude Longitude deg Latitude Latitude deg Altitude Altitude m ASL Azmth Body azimuth deg Eleva Body elevation deg Roll Body roll deg AbsVel Velocity with respect to the center of the Earth m s RelVel Velocity with respect to a point on the surface of the Earth at the same longitude and latitude as the vehicle m s AirVel Velocity with respect to the local air i e air speed m s YawRt Yaw rate deg s PitRt Pitch rate deg s RolRt Roll rate deg s Gamma Flight angle deg Headg Heading deg Mach Mach number AOA Angle of attack deg Axial Axial aerodynamic force N Ca Axial aerodynamic force coefficient normalized to the vehicle s nominal frontal area Normal Normal aerodynamic force N Cn Normal aerodynamic force coefficient normalized to the vehicle s nominal frontal area Mass Total vehicle mass kg Mdot Combined mass flow rate kg s through all 5 motor nozzles Thrust1 Thrust N generated by motor 1 Thrust2 Thrust N generated by motor 2 Thrust3 Thrust N generated by motor 3 Thrust4 Thrust
13. distance 13 5 31610 4e 3 Propellant It Aexit 0 0 0 01 0 13 0 23 1 12 2 24 4 16 4 96 6 14 Time D 2343 2003 1870 1310 1354 1434 450 QO Thrust Motors Null EDX Type 0 0 Ignition delay 0 25 Off centerline distance OH He 10 0 Propellant It Aexit Bt Et 0 Time 0 1 0 Thrust Motors Null EDX Type 0 0 Ignition delay 0 25 Off centerline distance 0 0 0 0 0 0 Propellant It Aexit 0 0 1 0 1 0 Time 0 1 0 Thrust 42 Recovery System Data Block The recovery system data block does exactly what one would assume it does it defines the recovery system More to the point the recovery system data block contains information on the deployment and subsonic drag characteristics of the recovery system Notice that the words recovery system are used and not parachute This is because Splash does not spend a lot of time doing detailed modeling of the recovery system It would thus be somewhat misleading to state that Splash models a parachute Nonetheless the vehicle slows to the appropriate descent rate and even swings from side to side much as a rocket under a parachute would In other words it does a good enough job for the task at hand While some of the data contained in this data bock is virtually self explanatory the deployment information is complex in nature and unique to Splash As a result there is a discussion of deployment criterion and formatting in the section entitled Staging and Recovery Criterio
14. is recommended that the user start with a small number 5 10 to see if the simulation has any obvious problems before committing oneself to a splash pattern generation a task that can take many hours to complete The number of iterations required for splash pattern generation will vary depending upon the complexities of the mission and the needs of the user Realistic iteration values range anywhere from 100 to 30 000 Mass Properties Mass The single standard deviation uncertainty in launch mass expressed as a percentage Moments of The single standard deviation uncertainty in moments Inertia and products of inertia expressed as a percentage Center of The single standard deviation uncertainty in center of Gravity gravity in calibers Aerodynamics Ca The single standard deviation uncertainty in axial force coefficient expressed as a percentage Cn The single standard deviation uncertainty in normal force coefficient expressed as a percentage CP The single standard deviation uncertainty in center of pressure in calibers Fin Cant The single standard deviation uncertainty in fin cant angle in degrees Propulsion Total Impulse The single standard deviation uncertainty in total impulse expressed as a percentage Propellant The single standard deviation uncertainty in propellant mass expressed as a percentage Thrust Axis The single standard deviation uncertainty in thrust alignment
15. parachute failure ooooonoccnnncnonnonnnonnnannnnnconoconocnnos 32 DU siete Eeer EE r 27 48 55 product Of inertia oooooncccnoncccnncconnncnonccnno 7 39 55 products of perta eee eee eeeeeeeeeees 19 Propellant cccsccssescesscesseteosesssesseesee 27 41 48 propellant mass 15 21 32 A Zeen 8 15 41 propulsion system 0 eee ese csecseeereeeeeeees 19 Q Q 44 55 R fall aed nee ai eae ae 14 POCO VOL Y ed ege Sek dE dee EECH 22 TECOVETY CLItCTION cocooococcconoconoconocnonnonnnonaninnnnnns 43 TECOVETY System nesia i aei 43 recovery system Talure eee eeeeeeeeee 15 refer nce area nenied oai a ii Seh 18 POM ect cette di 27 48 55 57 A Scenario UE 31 E decicion 45 SoftWare lc 53 specific Impulse curia ligas 55 splash potter 32 46 55 splash pattern Dle oooonnnnnnnnnncniccnonnconncnanonnnonnss 25 stage E 34 ON 22 39 staging criterion oooncconnconnnonnncnnnnnnonoconnccnnocnnonnos 43 system requirements cocconcccconocnnonnnonnconoconocinnonnns 10 T TEMPELALUL a acicate ee a 33 AMM aia 13 o Deen See 14 31 A ha ids Aa aa daa 27 43 48 UTC EE 27 48 thrust alignment oooconnccnoccnoncnnnnononancnonocnnocnnonnos 15 HEUSER 3 05 shore Edge eRd ee e 41 thrust misalignment oooconnnnnonnonnnonnnoncnnncnanccnnocnns 32 thrust time CUVE cocccnoooconnnccnnnnanonononononononns 22 41 A O ON 27 44 48 total impulse eee eeeeee eee 15 21 32 41 55 ON 47 trajectory lena iii 27 U ncertai ties s n
16. the scenario required The base filename should be entered sans any extensions sen stg etc For example if the input data files for a particular scenario are alpha scn and alphal stg then the user should enter the base filename of alpha That s it After base filename entry Splash will do its thing Program Files Splash Splash exe Splash 1 6 lt c gt 2BB2 Hall Consulting 326 W Felspar ve Ridgecrest CA Compiled 6 16 2662 Enter simulation base filename alpha screen capture of Splash prompting for the base filename Output Upon execution Splash produces a number of data streams The first and most obvious is the screen output In addition to screen output Splash generates anywhere from two to five data files Screen Output The Splash console application produces very limited screen output In fact this output is limited to nothing more than a progress update As Splash begins each simulation iteration it echoes the current iteration number and the total iterations requested by the user Nothing more Nothing less 45 Program Files Splash Splash exe Splash 6 1 6 c gt 2082 Hall Consulting 326 W Felspar fve Ridgecrest CA Compiled 6 16 2662 Enter simulation base filename alpha Processing Iteration 1 16 2 16 3 16 4 18 A screen capture of Splash as it processes the 12 of 10 iterations designated by the scenario alpha Splash Pattern File
17. unit system pane informs the user of the current unit system SI or English for which input output is expected presented The user may change the unit system at will by selecting the desired unit system from the pull down menu at the top of the main window Note however that before the unit system may be changed all input output windows must be closed SplashGul loj x File Edit Units Scenario Vehicle Run Output Arrange About CAPROGRAM FILES1SPLASH alpha si Units 09 27 2002 3 35 PM V3 The main window Input Windows A 6DOF simulation obviously requires a lot of data describing any number of conditions and properties applicable not only to the vehicle but to the launch environment as a whole Splash attempts to break up this mass of data into smaller logically organized blocks of data A window dedicated to each block of data handles the input of the appropriate data As a result it is believed that data input is as straightforward and intuitive as possible In other words the GUI should be largely self explanatory to any experienced rocketeer Launch Site As the name of this input window would imply the Launch Site input window contains all data concerned with the launch site This includes everything from the position and orientation of the launch rail to the altitude ASL of the anticipated impact zone The launch site window is accessed through the Scenario pull down menu found at the top of the main Splash wind
18. user wonder why include provisions for so many motors given the fact that the vast majority of the vehicle stages out there possess only one or two motors The answer is versatility By varying which motors are nullified the user may effectively model balanced clusters of 1 2 3 4 or 5 motors The table below illustrates in detail how various clusters may be modeled Motors in Cluster Active Motors Null Motors 0 1 2 3 4 5 1 1 2 3 4 5 2 2 3 1 4 5 3 1 2 3 4 5 4 2 3 4 5 1 5 1 2 3 4 5 The propulsion window allows the user to select any of 167 different pre defined commercial motors ranging from C impulse to N However by selecting a custom motor the user is also allowed to define his her own motors Custom motors have no size thrust or burn length limitations The propulsion window is accessed through any of the Vehicle gt Stage pull down menus found at the top of the main Splash window Once opened a propulsion system window will appear similar to the window shown below 20 Stage 1 Propulsion Properties Motor C4 es 9 Ch Ign Delay s Location m File Prop Mass kg Nozzle cm 2 OK Cancel CR ob Load Saveas Motors Estes_C6 EDX Total Impulse N s 8 82 0 0108 0 146438 10 xj Thrst N oom o of o ora 140 RE WO I m LL LL LL The propulsion system input window displaying data for motor 1 The contents of each
19. ATCOM HyperCFD PEP RockSim and Zeus Models Earth The Earth model employed by Splash is based on the WGS 84 Earth model Splash models the Earth as perfectly smooth rotating spheroid of uniform density The primary parameters of this model are as follows Major Axis m 6378137 0 Minor Axis m 6356752 3 Average Radius m 6371008 7 Angular Velocity rad s 72 92115e 6 Mass kg 5 979e24 Mass Gravitational constant mie 3 986004418e14 Standard Gravitational Acceleration m s 9 80665 Note that from the perspective of a fixed Earth centered coordinate system gravitational acceleration is assumed to be strictly a function of distance to the center of the Earth But this is only part of the story The fact that the Earth is non spherical coupled with its rotation yields a more complex gravitational model when by an observer on the Earth s surface The result is that gravitational acceleration as seen by an observer on the Earth s surface varies not only with altitude as one would expect but also with latitude as one may not expect Atmosphere Two different atmospheric models are used by Splash The first model used for density altitude correction initialization defines atmospheric conditions as the inverse of a 5 order polynomial The other model produces data that matches the ISO 1978 standard atmosphere to an altitude of 631 km above sea level and is used by Splash at all time
20. Each stage modeled by Splash is assumed to possess a cluster of up to 5 motors The engines are arranged in a cluster as seen in the picture below Obviously not every stage has 5 motors most in fact will not For stages with fewer than 5 motors the motors that do not exist in reality are simply simulated as motors that produce zero thrust and consume zero fuel The methodology used to describe any single motor is based upon proven methodologies used in government laboratories to model rocket motors within the context of kinematic analysis codes While these methodologies assume constant specific impulse throughout the motor s burn they do provide thrust corrections associated with the local ambient atmospheric pressure The input requirements for these methodologies is as follows Total impulse at sea level N s Propellant mass kg Nozzle exit area m 2 Time Thrust curve s N Installation Assuming a system capable of running Splash installation of Splash is trivial The distribution disk is set up to automatically launch the installation routine upon insertion into the disk drive If for any reason the installation routine should fail to automatically start up the user may manually start the routine The installation routine is found in the distribution disk s root directory and is called installer exe Installer handles everything associated with Splash installation with minimal input required of the user At installation t
21. First and foremost data files used by Splash are simple text files While not as compact or as elegant as other file formats text files allow for simple file manipulation and manual inspection for file accuracy Historically many simulation packages that utilize text data files have relied upon a very strict data formatting structure While some rules must apply every attempt has been made to make Splash input files easy to read for mere humans As a result the following may be said e Blank lines are ignored e Data is white space and or comma delimited In other words data items within a single line are delimited by any number of commas spaces or tab spaces e The occurrence of an asterisk denotes that any remaining text on a given line are comments and to be ignored by Splash e A single line of data is limited to 240 characters To better illustrate the conventions of data input below are a number of examples of lines of data that are 100 equivalent within the context of Splash input files 27 3 62610 0 0 008 lt That asterisk indicates comments 27 3 62 61e3 8e 3 Propelant kg It N s Nozzle m 2 27 3 62610 008 Propelant It Nozzle Exit Area 27 3 62610 8E 3 Are we getting the picture Each data file s name must also conform to a standard naming convention Again the details of each file will be discussed later but suffice to say that the names are all variations of a single file name
22. HC software program the software on a single computer The software is in use on a computer when it is loaded into temporary memory or installed into permanent memory of that computer Copyright The software is owned by HC and is protected by the United States copyright laws and international treaty provisions and all other applicable national laws Therefore you must treat the software like any other copyrighted material except for the fact that installation on a computer necessitates the creation of a copy of the software You may not copy any written material that accompanies the software Other Restrictions You may not rent or lease the software but you may transfer the software and accompanying written materials on a permanent basis provided you retain no copies and the recipient agrees to the terms of this agreement If the software is an update or has been updated any transfer must include the most recent update and all previous versions You may not reverse engineer decompile or dissassemble the software U S Government Restricted Rights The software and documentation are provided with restricted rights Use duplication or disclosure by the government is subject to restrictions as set forth in subparagraph c 1 ii of The Rights in Technical Data and Computer Software caluse at DFARS 252 227 7013 or subparagraph c 1 and 2 of the Commercial Computer Software Restricted Rights at 48 CFR 52 227 19 as applicable Manufactur
23. IA 2 Must contain the gross vehicle mass kg at which the moment and products of inertia calculations lines 3 6 were made This need not be the launch or burnout mass of the vehicle 3 Must contain three numeric arguments In order these arguments are Ixx m Ixy m and Ixz m 4 Must contain three numeric arguments In order these arguments are Iyx m Iyy m3 and lyz m3 5 Must contain three numeric arguments In order these arguments are Izx m Izy 17 Tf the user is unfamiliar with these terms the author recommends researching them on the internet as proper treatment of these topics would take more space than the author is willing to dedicate in these pages 39 m and Izz m Must contain the data block termination string A sample inertial tensor data block is shown below INERTIA 80 Be 0 0 Ixx Ixy IXZ 0 62 0 Iyx Iyy lIyz 0 0 62 LR ewe E22 Normal Force Data Block As one may imagine the normal force data block contains information about the aerodynamic normal force Most simulation packages store a list of normal force coefficients Cn s for direct use in normal force calculations Splash on the other hand uses lists of coefficients of a polynomial that is in turn used to calculate a normal force coefficient In other words Splash calculates the normal force coefficient by using an equation of the form C A B AOA C AOA where C
24. PUT WINDOWS reacia aii drid rice 12 LUCA iaa ds 12 UNG EE 14 EE 16 A A AAEE EE Seosteade ouch spuboeess Messe ANE AAE 17 Geometry EE 18 et EE 19 NT INC TEE 22 RUNNING THE BIMULATION nn nnnononnnnnnnnnncnnonnnnn ono nnnnnnnnananannncnnons 24 OUTPUT ee td no es o A PETE 25 Splash Patt rn EE 25 Trajectory Data File s Window siscsccssccessossassssasesisetnatise secure epesssaecpsdseubeotastigasvacsabesbassgeracdpetbestestasesteatigs 27 THE CONSOLE APPLICATION ssssiessssssicsissedsssssecesescssesdevsescessecssesvonsssecosssbssiseisceessseaseaiaossesesesssivsieesenes 29 DESCRIPTION POO EEEE DEE EEO AET ETE E EEO EEEE EE TEE O EEEE EEEE TE TETEE 30 INPUT REQUIREMENTS AORE EE EEO ANE ETE EE EEE EE EE ETEO EE EIEEE E EENE E TETEE 30 General Input Conventions s tne cessed AAEE E EE EAE NEEE E EE EEEE 30 AA TEE 31 Stage EE 34 Staging and Recovery Criterion Explained oooonnnnnnninnnonnnonncnnnonanonncnnnona nono n nan nnan cnn c on nooo none cn neon nera non 43 EXECUTION cz deciros Ee ia iii ae tase EEE 45 SP E NT 45 EE 45 Splash PatternPle oa as 46 Trajectory EE EE 47 SARA A RN TO 49 TIPLAND ARICA lados 50 KNOWN BUESA e ea cos 51 NEW FEATURES amp BUG EA ENEE AE 52 S101 RA RAAN a A D E IS AEREE E E E E E PEE Ee 53 ABOUTTAE AUTHOR e EEN 54 INS ebe EEE A I EI EE eg 55 SUE Eege ed 56 Introduction What Splash is Splash is a wind weighted 6 degree of freedom 6DOF rocket simulation with statistics based impact analysi
25. Time The data that defines the time axis on the thrust time curve Time is measured in seconds Thrust The data that defines the thrust axis on the thrust time curve Units are unimportant as the curve will ultimately be scaled to match the previously defined total impulse Staging Recovery The manner in which Splash handles staging and recovery system deployment is probably the most unique piece of programming logic within Splash Rather than simply staging deploying by time altitude or body elevation as many systems do Splash allows the user to construct more complex staging deployment criterion by combining up to three logical tests that are evaluated in series Each test performed for staging deployment contains three pieces of information The first piece of information is the flight parameter for which the testing is dependent Examples of the flight parameter are altitude time and dynamic pressure The second piece of information is a numerical value to which the flight parameter is compared The final piece of information is simply a flag to indicate whether the flight parameter is expected to be greater than or less than the numerical value indicated The flight parameters for which staging deployment may be linked to are as follows Parameter Description Altitude Altitude above sea level m or ft delta Altitude Change in altitude above sea level m or ft Atmospheric Pressure Local atmospheric press
26. ach input box in the aerodynamics window is as follows Classification Column Box Description Mach Ca Multiplier The axial force multiplier This is simply a constant by which the nominal axial force coefficient is multiplied by to facilitate drag sensitivity studies Normally the associated value will be 1 0 but suppose the user wishes to model a 10 drag increase In which case the user would merely have to use an axial force multiplier of 1 1 rather than re calculate and re type the entire axial force coefficient table The zero angle of attack axial force coefficient dCa The derivative of the axial force coefficient with respect to angle of attack Cb The base drag coefficient The user should ensure that the base drag coefficient is used many aeroprediction codes list the base pressure coefficient The two coefficients are related but not equivalent 16 Multiplier The normal force multiplier This is simply a constant by which the nominal normal force coefficient is multiplied by to facilitate normal force sensitivity studies Normally the associated value will be 1 0 but suppose the user wishes to model a 10 lift increase In which case the user would merely have to use a normal force multiplier of 1 1 rather than re calculate and re type the entire normal force coefficient table The zero angle of attack normal force coefficient usually zero dCn
27. aconcnononccnonanonanaconoss 21 41 ignition failure oooonnccnncccnonncnnccnonnnccnnos 15 32 55 IDEA HESE 31 A OS 32 impact pattern eee eee cess crono ncnnocnnos 46 US ee EE e 14 inertial enger 19 39 initial velocity oooconoccconccoconancnnnconnnanoconocnncnnccnnos 31 input CONVENTIONS oococcocccononnnonnncnnnonanannccnnccnnonnos 30 input requirement eee eens 6 12 30 INSTA ATION EEN 10 teratol se seei reoat iiaee 15 25 32 45 47 L latitude oe eee eee eee 13 25 27 31 47 48 launch MaSs esscceveccsscceesuiveseessteeeeeeeeusneenasersevens 19 launch rail 14 15 31 32 33 AA aaay 12 lawi 6 EE 15 32 length nd 7 19 A dE e 55 DT 13 longitude eee eee 13 25 27 31 47 48 M Mach EE 16 27 48 M S Shereene iniri i rse 7 19 27 32 39 48 MASS properties coooooooncccnoccconononoconocanccnnonanonns 15 18 1101016 e ee a ion 27 48 Model ica ais H moment Of inertia oooooooconcccnoniconononos 7 32 39 55 moments Of mertg cc ceceeeeeeceeeeeeeenees 15 19 OO 41 failure probability ooooonocnnonnnonnnococoncnaninnnnnos 32 MOOT C USTETS ennn ann i 20 motor fail re gudde 15 motor Jocapon 21 UE 21 N nominal diameter ooooococcconocinoccconononnncnonanonnncnnnos 19 nominal Jength n n 19 normal force occccconcnonocnnonocnnns 27 32 40 48 55 normal force muloplter cee eeeeeeeeeeneeeeeee 17 le Va EE 21 41 NUL MOLOTS ici id 20 O A eea a ae ea TS 25 45 P Parachute ns isor cit tri 15 22
28. ains the probability of a catastrophic failure CATO for each motor as a percentage Note that if any motor CATOs it is assumed that all other motors in the same stage suffer a similar failure due to debris impact 15 Contains the probability of a failure to deploy the recovery system as a percentage 16 Contains the probability of a parachute vehicle separation as a percentage 17 Contains the 1 sigma uncertainty for wind velocity in meters per second 18 Contains the 1 sigma uncertainty for wind direction in degrees 19 Contains the 1 sigma uncertainty for launch rail azimuth in degrees 15 Commonly referred to as a lawn dart 14 Commonly referred to as a zipper 32 20 Contains the 1 sigma uncertainty for launch rail elevation uncertainty in degrees H 173 21 Must contain the data termination string A sample uncertainty data block is shown below UNCERTAINTY 1000 How many times do we want to play MASS 3 Mass 1 sigma uncertainty percent 2 Moments of Inertia 1 sigma uncertainty percent 0 25 CG 1 sigma uncertainty calibers AERODYNAMIC 10 Ca 1 sigma uncertainty percent 10 Cn 1 sigma uncertainty percent 1 ER 1 sigma uncertainty calibers 05 23 Fin Cant Angle 1 sigma uncertainty degrees PROPULSION 5 Total Impulse 1 si
29. as theta 19 Usually referred to as gamma 22 While this may sound confusing at first it is actually very simple For example the staging criterion shown in the screen capture below indicates the following behavior 1 Wait until altitude is greater than 1000 m 2 Then wait for Mach number to drop below 0 5 3 Then immediately stage 3 test unused The staging recovery window is accessed through any of the Stage pull down menus found at the top of the main Splash window The only remaining input requirements found in the staging recovery system input window are the nominal diameter and chute Cd input blocks Splash assumes a recovery system that consists of a single circular parachute This parachute s nominal diameter and drag coefficient are thus obviously defined by the two remaining data input boxes Box Description Nominal Diameter Parachute nominal diameter m or ft Chute Cd Parachute drag coefficient assuming reference area equal to frontal area of parachute l Stage 1 Staging Recovery Properties Mach Number Immediate Immediate Immediate The staging recovery input window 23 Running the Simulation Once the user is satisfied that he she has set up the simulation scenario s to his satisfaction it is obviously time to run the simulation To do so the user at this time selects Run from the pull down menus at the top of the ma
30. ata concerning the flight of each individual stage from the moment it separates from the previous stage to the moment it impacts the Earth 21 Thus generating one two or three of these trajectories files as appropriate to the number of stages in the vehicle 47 Stage trajectory files share a common naming convention Specifically X out is appended to the base filename where X is the number of the stage in question For example if the base filename of the simulated scenario is alpha then the trajectory data for the first stage would be found in the file named alphal out Similarly the trajectory data for the second and third stages would be found in the files alpha2 out and alpha3 out respectively The remaining trajectory file the nominal trajectory file is the file that is most likely to be of initial interest to users This trajectory file combines the most interesting data from the stage trajectory files to create a single trajectory This trajectory describes the flight experienced by the vehicle if one assumes that boosters are no longer of interest after they separate from later stages The name of the nominal trajectory file is nothing more than out appended to the scenario base filename For example if the base filename of the simulated scenario is alpha then the nominal trajectory file is named alpha out Beyond the fact that the various trajectory files describe trajectories
31. c idea of where the rocket might land Latitude E 117 84 117 82 117 8 117 78 117 76 117 74 117 72 117 7 117 6822 117 ep Longitude A splash pattern representing 250 possible impact points The launch point is designated by the red circle on the right The figure above is a plot listing 250 potential impact points of a particular rocket The distribution of the impact points illustrates not just a nominal impact point but provides a level of confidence with respect to the likelihood of an impact in any given region Such data is indispensable in pre launch safety analysis and is also of use in determining possible locations for wayward rockets It is this capability that sets Splash apart The author is prepared to retract this statement the moment he is made aware of another simulation package of similar capability and price is made known to it What Splash isn t First and foremost Splash is not a modeling package In the eyes of the general public there is no perceived no difference between modeling and simulation There is however a difference Modeling involves the determination of static performance parameters For rockets this means things such as drag coefficients mass properties etc In contrast simulation involves putting models in motion in the context of set timelines and scenarios In lay terms models may be thought of as the input for simulations Beware Splash does not determine drag coefficient
32. ce coefficients Ca s for direct use in axial force calculations Splash on the other hand uses lists of coefficients of a polynomial that is in turn used to calculate an axial force coefficient In other words Splash calculates the axial force coefficient by using an equation of the form 34 C A B AOA C AOA where C axial force coefficient degrees A B C polynomial coefficients AOA angle of attack Extreme care should be used when selecting the values for A B and C in the above equation as poorly selected values will yield wildly inaccurate simulation results More to the point one should ensure that the values selected for A B and C produce a Ca of 0 0 at an angle of attack of 90 degrees While this methodology provides a smooth curve for Ca over a broad range of angles of attack with minimal user input it neglects the fact that axial force coefficients depend on Mach number For this reason Splash employs not one set of coefficients but a family of coefficients The format for the axial force data block is as follows Line Contents 1 Must contain the pneumonic CA 2 Must contain the axial force multiplier This is a number by which the final axial force is multiplied Usually the value of this number is 1 0 but any number can be used in the course of sensitivity studies For example if the user wishes to increase axial force by 10 in an attempt to see what would happen he need o
33. d moments products of inertia This is not always the best assumption but it is reasonable and simplifies user input requirements Ixx The moment of inertia kg m 2 or lbm ft 2 taken about the X axis longitudinal forward Ixy The product of inertia kg m 2 or Ibm ft 2 taken in the XY plane Ixz The product of inertia kg m 2 or Ibm ft 2 taken in the XZ plane lyy The moment of inertia kg m 2 or lbm ft 2 taken about the Y axis port lyz The product of inertia kg m 2 or Ibm ft 2 taken about the YZ plane Izz The moment of inertia kg m 2 or lbm ft 2 taken about the Z axis up Propulsion While providing perhaps the most obviously needed data in a rocket simulation the propulsion system input window is visually the most intimidating It really is quite simple though Splash models each stage as if it possessed five motors arranged as seen in the sketch below Obviously not every vehicle in the real world has five rocket motors in it most have considerably fewer To allow for this fact Splash does not require that every motor provide thrust have a nozzle or even have any mass for that matter In other words motors that are not found in the real world vehicle Splash is modeling are mathematically nullified thus ensuring that they do not affect simulation results 19 II The configuration of all five motors in each stage All these null motors may make the
34. e altitude plot viewed from within the Splash GUI slata plotting interface The author concedes however that for presentation quality graphics the user is likely to be better off importing the data from the trajectory file s into a dedicated data processing application or spreadsheet 28 The Console Application 29 Description The heart and soul of Splash is a console application that may be run independent of the GUI While the console application is not as easy to use without the GUL it allows the user to directly manipulate the simulation input files In the author s experience such direct manipulation often allows the user to simulate conditions not anticipated and thus often not directly supported by the original author As a result direct manipulation of the data files and use of the console application is considered to be the modus operandi of the serious user Thus some discussion of this is in order Input Requirements While many simulation packages include all data pertinent to a scenario in a single input file Splash separates the data into two to five data files depending upon the number of stages in the rocket of 2 different classifications The two different types of data files are as follows scenario files and stage files Each of these two file types will be discussed in detail but first 1t is appropriate to outline some basic conventions that hold true for all Splash input files General Input Conventions
35. e the amplitude of the oscillation falls to about 280 degrees In addition it does not appear that vehicles under parachute suffer from the bug Fortunately the extreme angles of attack that bring about this bug are rarely seen in realistic scenarios 51 New Features amp Bug Fixes Version 1 1 0 l Support for English units was added to the GUI Note that internally Splash still uses the SI system 2 The propulsion input window in the GUI was totally revamped The new window is less intimidating but just as easy to use 3 A maximun flight time of 3600 seconds 1 hour was inserted into the console application This allows users to go for orbit without putting Splash into an infinite loop 4 As the copy protection scheme was giving a few users problems that ranged from cosmetic or disastrous this has been removed 5 Atusers request the install routine now adds a shortcut to the Splash GUI to the desktop Version 1 0 1 1 The install routine now copies the User s Manual to the hard drive 2 A small bug that could result in negative thrust under certain circumstances was fixed 52 Software License Hall Consulting Software License This is a legal agreement between you the end user and Hall Consulting HC By installing and or using this software package you are agreeing to be bound by the terms of this agreement D 2 3 4 5 Grant of license HC grants you the right to use one copy of the enclosed
36. earch is recommended for clarification Dynamic pressure The angular position of a vehicle s dorsal fin or top with respect to horizontal Defined as the instantaneous thrust divided by propellant burn rate specific impulse proves a benchmark by which the efficiency of a propulsion system may be measured A graphical representation illustrating numerous impact points of a given vehicle on which a Monte Carlo uncertainty analysis has been performed Defined as the integral of a motor s thrust time curve the total impulse provides a benchmark by which the size of a motor may be measured The Earth model used in the Global Positioning System GPS The portion of any angular offset of the vehicle s longitudinal X axis with respect to the velocity vector that is about the vertical Z axis A recovery system failure mode in which the parachute or other drag inducing device is physically separated from the rest of the vehicle 55 Index 2 2 stage deplovment eee ee eee esse cee cnee eens 50 3 3 Sigma Circle oo else eee eee naia 46 55 A ACTOMYNAMNCS ACEN 8 16 alacant 31 SIE SPCC PERE SEEE ET 27 48 TE 41 altitude oe ENEE 14 27 43 48 angle Of attack oooocononnnonnnocnconononcconcnnninnnnnns 27 48 atmosphere sein eee i a E eo 7 13 atmospheric pressure ccccooccnocccnonnnoncononccnnnac noss 44 axial fOrC erse niir erra 27 32 34 48 55 axial force coeficient oooooonocccoccnoncononononancnanonnnono 16 a
37. ed to determine the local air density and thus the correct density altitude If the current barometric pressure is unknown or if the user simply wishes to use a standard atmosphere a negative value in this block will turn off atmospheric corrections Location Longitude The longitude in the WGS 84 coordinate system of rocket s center of gravity at the start of the simulation East longitude is defined as a positive angle while West longitude is defined as a negative angle Latitude The latitude in the WGS 84 coordinate system of rocket s center of gravity at the start of the simulation North latitude is defined as a positive angle while South latitude is defined as a negative angle 13 Altitude The altitude m or ft ASL in the WGS 84 coordinate system of the rocket s center of gravity at the start of the simulation Rail Data Azimuth The azimuth angle degrees in which the launch rail and rocket is pointing at the start of the simulation An angle of zero degrees defines a rail pointing to the North an angle of 90 degrees defines a rail pointing to the East etceteras Elevation The elevation angle degrees in which the launch rail and rocket is pointing at the start of the simulation An angle of 90 degrees defines a rail pointing straight up an angle of O degrees defines a horizontal launch rail Length The distance m or ft the vehicle must travel before it is released f
38. ehicle in question utilizes a pitot tube in conjunction with a barometric unit Change in dynamic pressure Time Trigger value units are seconds This parameter should be used when the vehicle in question utilizes a clock or pyrotechnic delay for staging deployment t Change in time Examples of possible user desired scenarios and the corresponding staging deployment criterion may be seen below Desired Profile Criterion Lines Fly for a total of 10 seconds Stage deploy gt 10 0 0 0 0 0 Fly until missile hoses over past horizontal Wait for missile to descend below 1000 m ASL Stage deploy 0 0 1000 0 0 VAVIV V Fly to apogee Wait three seconds Stage deploy HEQ vvv SWS ooo At this point the user may have noticed that in the above examples the third test of the staging deployment criterion is always I gt 0 0 This has nothing to do with program logic Rather it is representative of the fact that two tests will most likely provide all the functionality required for 99 of the users out there The third test was included to incorporate that last 1 of users who may have more complex requirements for staging deployment timing 44 Execution Execution of the console application is trivial From Windows the user need only double click the Splash console application executable At this time Splash will prompt the user for the base filename for
39. ents corresponding to the Mach numbers listed in line 6 Must contain at least 2 but no more than 24 numeric arguments These arguments are the 1st order normal force coefficients corresponding to the Mach numbers listed in line 6 Must contain at least 2 but no more than 24 numeric arguments These arguments are the 2nd order normal force coefficients corresponding to the Mach numbers listed in line 6 10 Must contain the data termination string A sample fin data block may be seen below This data block with the exception of lines 2 4 may very well represent s ufficiently accurate data for all the rockets the user ever desires to model FINS Polynomial is for FIN Cns 4 number of fins 6 FinArea Aref 22 1 CPx CPr in calibers 0 0 cant angle 0 0 0 8 1 4 E eo 22D EE Mach 0 0 0 0 0 0 A 0 022 0 022 0 022 0 022 0 022 0 022 B 1 2e 4 1 2e 4 1 2e 4 1 2e 4 1 2e 4 1 2e 4 SE General Information Data Block 38 The general information data block contains a mixture of basic mass and geometry information and staging information While the mass and geometry data is largely self explanatory the staging information is complex in nature and unique to Splash As a result there is a discussion of staging criterion and formatting in the section entitled Staging and Recovery Criterion Explained The format of the general information data block is as follows
40. er is Hall Consulting 320 W Felspar Ave Ridgecrest CA 93555 Warranty Splash includes no warranty in any way shape or form The user understands that while Splash represents the very best efforts of HC HC does not possess the resources to fully verify and debug software in a manner consistent with major corporations 53 About the Author At this point there are those who would rightfully question the capabilities of your average Joe to write such software With this question in mind a brief resume of sorts is offered 1993 1995 University Computing Services University of Oklahoma Provided technical support to students and faculty with an emphasis on debugging programs written in ANSI compliant C 1994 Awarded Bachelors of Science in Mechanical Engineering University of Oklahoma 1995 2001 Weapons Engineering and Analysis Branch Naval Air Warfare Center Weapons Division Authored and employed various 3 and 6 DOF codes to simulate military weapon systems ranging from shoulder fired rockets to IRBMs for both design and range safety purposes 2001 2002 Ordnance Test Support Branch Naval Air Warfare Center Weapons Division Provide engineering support for ordnance testing activities These activities include the static firing of solid rocket motors of up to 1 5 million pounds thrust While this hardly qualifies the author as the world s leading expert on rockets and 6 DOF codes it is hoped that the reader will concur that he
41. es m ASL for which corresponding wind direction data see line 4 is valid 4 Must contain the same number of numeric arguments as line 3 As previously mentioned these arguments define the direction degrees in which the wind is coming from O degrees indicates a wind from the North 90 degrees represents a wind from the East and so on Note that it is good practice to make the last 2 arguments identical to avoid any unchecked extrapolation in the event the vehicle exits the defined weather 33 patterns 5 Must contain at least 2 and no more than 24 numeric arguments These arguments are a list of altitudes m ASL for which corresponding wind velocity data see line 6 is valid Note that in practice lines 3 and 5 will most likely be identical but there is nothing in Splash programming logic that dictates this 6 Must contain the same number of numeric arguments as line 5 As previously mentioned these arguments define the velocity m s of the wind As with line 4 it is good practice to make the last 2 arguments identical to avoid any unchecked extrapolation in the event the vehicle exits the defined weather patterns H 173 7 Must contain the data block termination string a A sample weather data block may be seen below WEATHER A hot day with low level winds from the N and high level winds from the NNE 760 43 5 O le3 Zei bei 10e3 20e3 21e3
42. fact that the center of pressure also depends on Mach number For this reason Splash employs not one set of coefficients but a family of coefficients The format for the axial force data block is as follows Line Contents 1 Must contain the pneumonic CP 2 Must contain a single numeric argument the center of pressure CP offset The CP offset provides a simple way for the user to vary the CP as one may during the course of a sensitivity study While a nominal CP is calculated as described previously the CP offset is added to this value to move the CP fore or aft as desired For example if the user wishes to move the CP back one caliber the CP offset should be 1 0 Similarly if the user wishes to move the CP foreward 0 5 calibers the CP offset should be 0 5 Obviously 0 0 is the value normally selected 3 Must contain at least 2 but no more than 24 numeric arguments These arguments are the Mach numbers for which the center of pressure coefficients see lines 3 5 are valid 4 Must contain at least 2 but no more than 24 numeric arguments These arguments are the Oth order normal force coefficients corresponding to the Mach numbers listed in line 3 5 Must contain at least 2 but no more than 24 numeric arguments These arguments are the 1st order normal force coefficients corresponding to the Mach numbers listed in line 3 6 Must contain at least 2 but no more than 24 numeric arguments These arguments a
43. force N or lbf Cn Normal aerodynamic force coefficient normalized to the vehicle s nominal frontal area Mass Total vehicle mass kg or Ibm Mdot Combined mass flow rate kg s or lbm s through all 5 motor nozzles Thrust1 Thrust N or lbf generated by motor 1 Thrust2 Thrust ON or lbf generated by motor 2 Thrust3 Thrust N or lbf generated by motor 3 Thrust4 Thrust N or lbf generated by motor 4 Thrust5 Thrust N or lbf generated by motor 5 Prop1 Propellant kg or Ibm remaining in motor 1 Prop2 Propellant kg or Ibm remaining in motor 2 Prop3 Propellant kg or Ibm remaining in motor 3 Prop4 Propellant kg or Ibm remaining in motor 4 Prop5 Propellant kg or Ibm remaining in motor 5 12 No failures all mission parameters exactly as found in input files windows 27 As stated elsewhere Splash also allows the user to get a quick glimse of the data found in the trajectory files in a graphical format The plotting routines are accessed through the Output pull down menu found at the top of the main Splash GUI window The use of these routines is trivial and is reduced to selecting variables for the X and Y axis of a plot from pull down menus found on the plotting window see below Nominal Trajectory alpha Nominal Trajectory 400 350 4 _ 300 S 250 4 Si E 200 7130 100 50 D 10 20 30 40 50 60 Time s Avis M Print Close Y Axis Altitude m ASL y A tim
44. found to be true Splash begins to examine the third test When the third test is found to be true Splash separates the upper stage or deploys the recovery system as appropriate While some examples will be shown shortly it would be logical to first list the simulation parameters available to the user for staging deployment The simulation parameters currently supported by Splash for use in staging deployment are Parameter Description A Altitude Trigger value units are meters above sea level This parameter is most likely useful to those using barometer based deployment devices or a 6DOF inertial measurement unit IMU a Change in altitude Trigger value units are meters E Body elevation angle sometimes referred to as theta Trigger value units are degrees By convention 90 degrees specifies a vehicle pointing Straight up 18 Assume a single parachute of circular section 12 Note that a booster stage is allowed to separate from the sustainer and deploy a recovery system These events are completely independent of each other 43 while a 90 degrees specifies a vehicle pointing Straight down When using deployment devices such as horizon detectors this is most likely the parameter one should use CH Change in body elevation angle Flight angle sometimes referred to as gamma Trigger value units are degrees By convention 90 degrees specifies a velocity vect
45. gh which the centroid of aerodynamic forces acting on that body passes The normal force coefficient The component of the total aerodynamic force acting on an airplane or airfoil that acts opposite to the velocity vector of a vehicle The pressure exerted on a vehicle s leading edges due to the pressure exerted by moving air Usually denoted as Q The angle of a vehicle or launch rail s longitudinal axis with respect to horizontal Often denoted as theta A propulsion system failure defined by an igniter s failure to ignite a motor s propellant grain in a manner consistent with sustained combustion of said grain The component of the total aerodynamic force acting on an airplane or airfoil that acts perpendicular to the velocity vector A mass property that measures how resistant an object is to torque More precise definitions are somewhat complex and math intensive the reader is recommended to search for such a definition online The aerodynamic force acting perpendicular to the longitudinal axis of a flight vehicle At zero degrees angle of attack normal force is equivalent to lift The portion of any angular offset of the vehicle s longitudinal X axis with respect to the velocity vector that is about the horizontal Y axis Closely related to the moment of inertia the product of inertia measures the dynamic balance of a rotating object Again precise definitions are complex and math intensive again an online s
46. gma uncertainty percent 1 Propellant Mass 1 sigma uncertainty percent 0 25 Thrust Misalignment 1 sigma uncertainty degrees FATLURE 2 Ignition failure likelihood percent 1 CATO failure likelihood percent 5 Deployment Failure failure likelihood percent 10 Chute Failure failure likelihood percent WEATHER 3 Wind Velocity 1 sigma uncertainty mps 10 Wind Direction 1 sigma uncertainty degrees RATL 5 Azimuth Error 1 sigma uncertainty degrees 1 Elevation Error 1 sigma uncertainty degrees Weather Data Block Again the name of the data block is indicative of what data it contains In this case the data block contains the local atmospheric conditions Wind conditions obviously affect weather cocking but local barometric pressure and temperature effects density altitude which in turn effects lift drag and thrust generated by the rocket The format for the weather data block is as follows Line Contents 1 Must contain the pneumonic WEATHER 2 Must contain 2 numeric arguments In order they are the launch site s current barometric pressure mmHg and temperature C If the current barometric pressure is unknown or if the user simply wishes to use a standard atmosphere a negative value for barometric pressure will turn off atmospheric corrections 3 Must contain at least 2 and no more than 24 numeric arguments These arguments are a list of altitud
47. h rail The format of the rail data block is as follows Line Contents 1 Must contain the pneumonic RAIL 2 Must contain 3 numeric arguments In order they are the launch rails longitude degrees latitude degrees and altitude meters ASL Note that West longitude is denoted as a negative angle while South latitude is likewise considered a negative angle 3 Must contain 3 numeric arguments In order they are the launch rail s azimuth degrees elevation degrees and length meters Note that the convention used within Splash dictates that a negative elevation is pointing up 4 Must contain 1 numeric argument This argument is the initial velocity of the rocket in meters per second Most of the time this argument will be set to zero but the user was left with the option of non zero initial velocities to crudely model a gun launched rocket or similar system that may have a non negligible velocity at motor ignition H 173 5 Must contain the data block termination string d A sample rail data block may be seen below This data indicates that a rocket is to be launched due East and at an elevation angle of 80 degrees 10 degrees off vertical from the author s backyard in Southern California The launch rail is 10 meters long and the initial velocity is 0 meters per second RAIL 117 6726 35 6337 728 2 Longitude Latitude Altitude ASL 90 0 80 0 10 0 azimuth elevat
48. he user is asked to provide the name of a directory in which Splash will be installed The default directory is C Program FilesiSplash but the user may dictate any directory that suites his or her fancy by manipulating the pull down menus and text box at the upper right provided Splash Install Directory Dialog Install Splash into which directory Drive Path Directory Sc he Splash Ze Program Files 3 14 East A Accessories Adaptec J Adobe a Adobe Type Manag y C Program Files Splash The directory dialog within the install routine Upon completion of the install Splash is fully functional Further Splash makes no modifications to the system registry and all files required at runtime are found within the Splash directory or subdirectories thereof As a result uninstalling Splash is as simple as deleting the Splash directory 5 System requirements Win95 Pentium CD ROM 10 MB free hard drive space 10 The GUI Application Main Window In addition to providing the pull down menus that drive all user input in Splash the main window also provides some feedback to the user in the status bar at the bottom of the window Of primary interest are the base file name and unit system panes The base file name pane provides the current path and file name in which the data contained within the memory of the Splash GUI will be saved in the event the user commands Splash to save its data Similarly the
49. in Splash window When Run is selected Splash will immediately perform three tasks Saving all input data to disk is the first task Once saving is completed Splash will perform a simple sanity check on the input data to ensure there are no obvious blunders in the data Example a second stage mass higher than the first stage burn out mass Finally Splash will invoke the number cruncher that is the heart and soul of Splash the Splash console application When the console application is called a new window will appear on the screen This window is the console application and is an entity unto itself It neither knows nor cares about the existence of the Splash GUI Similarly the Splash GUI has no way of knowing what sort of progress the console application has made The upside of this behavior is that the GUI isn t completely locked up while iawaits for simulation results from the number cruncher The downside of this behavior is the user must use a small bit of self control and adhere to the following 1 Do not attempt to run the console application again until the console application has closed itself 2 Do not attempt to access trajectory files either from a DOS window or through the GUI until the console application indicates that it has started on its second iteration 3 Do not attempt to access the splash pattern file either from a DOS window or through the GUI until the console application has closed itself The GUI shou
50. in degrees Wind Direction The single standard deviation uncertainty in wind origin direction in degrees Velocity The single standard deviation uncertainty in wind speed in meters or feet per second Launch Rail Azimuth The single standard deviation uncertainty in launch rail azimuth angle in degrees Elevation The single standard deviation uncertainty in launch rail elevation angle in degrees Failure Ignition The likelihood of single motor ignition failure expressed as a percentage CATO The likelihood of single motor catastrophic failure expressed as a percentage Note that all CATOs are assumed to occur at motor ignition Deployment The likelihood of recovery system deployment failure expressed as a percentage Chute Failure The likelihood of recovery system failure expressed as a percentage 15 Aerodynamics As the name of this input window may imply the Aerodynamics input window contains data concerned with gross vehicle aerodynamics The Aerodynamics window is accessed through any of the Vehicle gt Stage pull down menus found at the top of the main Splash window Once opened a Aerodynamics window will appear similar to the window shown below HUTT h hi 5 o 0 005538 0 007958 TLL lelai UUU E L Stage 1 Aerodynamic Properties loj x o T o v Offset 0 03675 UE ULA LUU EU U e AUUT lilit AUUE EITEL Tea A The Aerodynamics input window The contents of e
51. input box in the propulsion system window is as follows Classification Column Box Description Motor X 1 5 Ign Delay The delay seconds from the activation of the current stage until the ignition of the motor in question In most cases the ignition delay will be zero Non zero numbers are however desired in the event of air started motors or multiple stage rockets with coast periods between stage separations and ignitions Location The motor s off centerline distance m or ft in accordance with the motor configuration sketch seen previously in this section of the manual Being on the centerline by definition motor will always have an off centerline distance of 0 0 The rest of the motors should obviously have non zero offset distances File The file that contains pre programmed motor data for the motor in question Performance data for custom motors is loaded or saved as appropriate to or from the listed file when the load save buttons are clicked Total Impulse The sea level total impulse N s or lbf s of the motor in question Note th distance s always zero at the number mo tor is assumed to be Prop Mass The mass of propellant kg or Ibm contained within the motor in question Nozzle The total exit area of all nozzles cm 2 or in 2 possessed by the motor in question on the vehicle s center line and thus the off centerline 21
52. ion rail length 0 velocity Terrain Data Block The terrain data block does nothing more than define the local terrain s altitude above sea level in the landing zone For most cases the local terrain and the launch rail will be at the same altitude but Splash allows the user to define separate altitudes for the launch and impact areas The most obvious use of this feature is to crudely simulate an air launch but it may find use in terrestrial launches as well to simulate other exotic systems Note that a rocket has been deemed to impact the Earth when it s altitude falls below the terrain altitude and it s flight angle gamma indicates the rocket is in a dive The format of the terrain data block is as follows 31 Line Contents 1 Must contain the pneumonic TERRAIN 2 Must contain a single numeric argument This argument defines the altitude of the impact area in meters above sea level 3 Must contain the data block termination string Although they are very simple a sample terrain data block is shown below for completeness T 728 ERRAIN Local terrain is about 2300 feet ASL Uncertainty Data Block Uncertainty data blocks contain information on all parameters that are to be modified in the generation of the splash pattern The format of the splash data file is as follows Line Contents 1 Must contain the
53. is due to drag at the base of the vehicle This data is used to calculate the difference in axial force between thrust on and off conditions 15 At zero angle of attack drag and axial force are identical 35 Note that one should ensure that the actual base drag coefficient is used some aeroprediction codes produce a base pressure coefficient A base pressure coefficient is not the same thing as a base drag coefficient Ifin doubt entry of zeros is probably the best bet The format of the base drag data block is as follows Line Contents 1 Must contain the pneumonic CB 2 Must contain at least 2 but no more than 24 numeric arguments These arguments are the Mach numbers for which the base drag coefficients see line 3 are valid for 3 Must contain at least 2 but no more than 24 numeric arguments These arguments are the base drag coefficients corresponding to the Mach numbers listed in line 2 4 Must contain the data block termination string A sample base drag data block is shown below CB 0 2 0 8 0 9 1 0 1 2 1 4 1 75 2 5 3 5 Mach 0 15 0 15 0 16 0 22 0 23 0 20 0 17 0 12 0 08 Cb Center of Gravity Data Block The center of gravity data block is nothing more than a one dimensional look up table listing the center of gravity in calibers and corresponding masses representative of various instants during a rocket s burn The format of the center of gravity data block is as follows
54. l The Fin input window 17 The contents of each input box in the fin properties window is as follows Classification Column Box Description General Info Number of fins The number of fins possessed by the rocket Valid numbers range from 3 to 6 Cant angle The fin cant angle in degrees Area of fin The area of one side of one fin expressed as a multiple of the aerodynamic reference area for the overall vehicle Location Fin CP The longitudinal center of pressure of a fin measured in longitudinal calibers from the tip of the vehicle s nose A good rule of thumb for this value is the 1 4 chord mark on the fin Fin CP radial The radial center of pressure of a fin measured in calibers from the centerline of the vehicle A good rule of thumb for this value is L caliber added Geometry Mass Obviously the geometry and mass properties window defines the gross vehicle dimensions as well as mass properties It should be noted that the nominal diameter entered on this page defines the reference area used for all aerodynamic calculations i e Aref PI 4 Diam 2 The geometry and mass properties window is accessed through any of the Vehicle gt Stage pull down menus found at the top of the main Splash window Once opened a geometry mass properties window will appear similar to the window shown below l Stage 1 Geometry Mass Properties Center of Gravity Geometry Reference Dia
55. ld prevent the user from doing any of the above nonetheless the user is to consider himself warned lest he find a way to circumvent the GUI s efforts at preventing the user from doing something stupid Hall Consulting 326 W Felspar fve Ridgecrest CA Feature frozen beta release Simulation base filename alpha Processing Iteration The console application as it starts the 4 iteration out of 10 requested The data is saved exactly as if the user had selected Save from the File pull down menu This step is required due to the program architecture employed by Splash 24 Output The Splash console application generates anywhere from four to six data streams depending upon the number of stages to be modeled in the simulation These streams provide user feedback trajectory data and splash pattern data The most obvious of these streams is the text sent to the console application s window The console application output seen above provides no data concerning scenario specifics but it does provide the user with information regarding overall simulation progress In other words it displays a counter showing how many iterations were requested and which iteration is currently being processed nothing less nothing more The remaining data streams are all ASCII text files of fixed column width for easy import into spreadsheets and other data processing applications But while these text files are designed for easy impo
56. le it logically follows that the aerodynamic assumptions used by Splash are axisymmetric as well This means that current roll angle does not affect axial or normal forces at non zero angles of attack One aspect of Splash s aerodynamic model that may throw many users off balance is the use of axial and normal aerodynamic forces rather than the lift and drag forces most people are familiar with Lift and drag forces are respectively defined to be perpendicular and opposite to the velocity vector By contrast normal and axial forces are defined as perpendicular and opposite to the vehicle s own longitudinal axis Both systems are valid Both systems provide for vector addition that yields the net aerodynamic forces acting upon the vehicle But to understand why the axial normal force pairing is advantageous for rocketry work one need only remember that the vast majority of hobby rocketry accelerometers are one dimensional they record accelerations in line with the vehicle longitudinal axis As a result the data processing required to properly interpret data from such instrumentation is reduced A sketch illustrating the relationships between lift drag normal and axial forces and their orientations with respect to the vehicle s longitudinal axis and velocity vector Splash models the axial force normal force and center of pressure as a family of second order polynomials that are functions of angle of attack and Mach number Propulsion
57. meric arguments These arguments are the 2nd order normal force coefficients corresponding to the Mach numbers listed in 7 line 3 Must contain the data block termination string A sample normal force data block may be seen below 40 CN For each Mach Cn AOA A B AOA C AOA 2 1 0 Cn fudge factor 0 0 0 8 1 4 1375 2 5 3D Mach 0 0 0 0 0 0 A 0 51 0 40 0 32 0 36 0 28 0 28 B 0 019 0 022 0 027 0 024 0 022 0 018 BIC Propulsion System Data Block Obviously the propulsion system defines the rocket motors driving the vehicle s flight What is not obvious however is the fact that each stage is assumed to possess five rocket motors No more No less The motors are arranged in a manner similar to the five F 1 s found on the Saturn V Those who are not up on their rocketry history may instead refer to the sketch of the motor arrangement found below As seen from the aft end the layout of the five rocket motors found in each stage But not every vehicle has five motors how is such a configuration suited to simulate vehicles with fewer than five motors In two words null motors While all five motors exist in program logic there is nothing in said logic that mandates these motors to provide any thrust or even have any propellant in them Thus excess motors do not actually affect the vehicle s flight in any way shape or form The format of the propulsion system data block is as follows
58. meter m 0 0254 6 875 Length cal 11 8 125 oa a Ei K Q Q ep o H 0 0493 Launch Mass Mass kg 0 0493 Inertial Tensor Mass 2 Calculation kg 0 0493 box bey kez kg m 2 0 000003 of 0 lyy lyz from 2 fo o0323 o Izz kg m 2 0 000323 OK Cancel boz f ses 0 043 0125 LL LL LL LL LL LL Wm LL LL LL LL LL E The geometry mass properties input window 18 The contents of each input box in the geometry mass properties window is as follows Classification Column Box Description Center of Gravity Mass The mass kg or Ibm associated with the CG listed in the next column At least two masses should be listed and all should be ascending order CG The center of gravity calibers that corresponds to the mass listed in the previous column Geometry Diameter The nominal diameter of the vehicle m or ft This parameter defines 1 caliber as well as the reference area used for most aerodynamic constants Aref PI Diameter 2 4 Length The nominal length of the vehicle calibers Launch Mass The initial mass kg or Ibm of the stage or vehicle in question Inertial Tensor Mass The mass kg or Ibm corresponding to the moments and products of inertia that make up the inertial tensor Obviously moments products of inertia vary with mass Splash assumes a linear relationship between the mass an
59. moments For this reason it is not terribly important to have exact numbers and in fact the numbers listed in the sample file may be sufficiently accurate for most applications The format for the fin data block is as follows Line Contents 1 Must contain the pneumonic FINS 2 Must contain an integer defining the number of fins the rocket has Note that while program logic will allow for any number of fins realistically the methods employed in Splash dictate that no more than 6 fins be used Must contain a numeric argument defining the planer area of a single fin as multiple of the cross sectional area of the vehicle While obviously a non standard nomenclature this method allows the scaling of vehicles up or down with a minimum of hassle Must contain two numeric arguments The first of these arguments is the longitudinal location of the fin s center of pressure measured as the number of vehicle calibers from the vehicle s nose The second argument is the radial location of the fin s center of pressure again measured in calibers Must contain a single argument the fin cant angle measured in degrees Must contain at least 2 but no more than 24 numeric arguments These arguments are the Mach numbers for which the fin normal force coefficients see lines 7 9 are valid Must contain at least 2 but no more than 24 numeric arguments These arguments are the Oth order normal force coeffici
60. n Explained The format of the recovery system data block is as follows Line Contents 1 Must contain the pneumonic RECOVERY 2 Must contain two numeric arguments In order these arguments are the recovery system s subsonic drag coefficient and nominal diameter m 3 Must contain the first line of the deployment criterion As stated previously staging criterion will be discussed in detail in a later section of this manual 4 Must contain the second line of the deployment criterion 5 Must contain the third line of the deployment criterion 6 Must contain the data block termination string Staging and Recovery Criterion Explained Within the general information and recovery system data blocks there exist six lines of data that have until now been unexplained As these lines are collectively referred to as the staging and deployment criterion it is obvious that these lines control exactly when and where a vehicle stages or deploys it s recovery system Exactly how these lines control staging and deployment is actually quite simple The staging criterion is a collection of three logical tests that must be satisfied in order Each test is a relatively simple numerical comparison between a given simulation parameter altitude time etc and a user specified trigger value When the first test is found to be true Splash begins to examine the second test When the second test is
61. n The iteration or run number While most runs include the randomization required of a Monte Carlo analysis it should be noted that the 0 run does not include any randomization In other words the 0 run is the nominal trajectory lLongitude Longitude of the 1 stage impact point in degrees A negative angle corresponds to West longitude lLatitude Latitude of the 1 stage impact point in degrees A negative angle corresponds to South latitude 2Longitude Longitude of the 2 stage impact point in degrees A negative angle corresponds to West longitude 2Latitude Latitude of the 2 stage impact point in degrees A negative angle corresponds to South latitude 3Longitude Longitude of the 3 stage impact point in degrees A negative angle corresponds to West longitude 3Latitude Latitude of the 3 stage impact point in degrees A negative angle corresponds to South latitude Trajectory Files Splash generates anywhere from two to four trajectory files per execution One file is generated to describe each stage s flight and a final file compiles selected portions of the stage trajectory files to generate a single nominal trajectory Altitude m Time s An Excel plot generated with time altitude data taken from two different Splash stage trajectory files illustrates the trajectory of each stage of a boosted dart The most informative of Splash trajectory files are the stage trajectory files These files contain d
62. nly input 1 1 as the multiplier rather than generate a new drag curve 3 Must contain at least 2 but no more than 24 numeric arguments These arguments are the Mach numbers for which the axial force coefficients see lines 4 6 are valid 4 Must contain at least 2 but no more than 24 numeric arguments These arguments are the Oth order axial force coefficients corresponding to the Mach numbers listed in line 3 5 Must contain at least 2 but no more than 24 numeric arguments These arguments are the 1st order axial force coefficients corresponding to the Mach numbers listed in line 3 6 Must contain at least 2 but no more than 24 numeric arguments These arguments are the 2nd order axial force coefficients corresponding to the Mach numbers listed in line 3 7 Must contain the data block termination string g A sample axial force data block may be seen below notice that the first row of coefficients the A row are simply the zero lift axial force coefficients which are equivalent to zero lift drag coefficients CA For each Mach Ca AOA A B AOA C AOA 2 1 0 0 2 0 8 1 2 t 2 5 34 5 Mach 0 97 0 91 1 66 1 42 1 23 1 11 A 0 035 0 015 0 086 0 022 0 024 0 010 B 0 0027 7e 4 0 0047 0 0014 0 0020 0 0011 C Base Drag Data Block The base drag data block is nothing more than a one dimensional look up table of base drag coefficients the portion of a vehicle s zero lift drag that
63. odel This new stage should match the real final stage in every way shape and form but it should deploy it s recovery system immediately The recovery system properties for this stage should match those of the main parachute The result of such a scenario will match that of a vehicle equipped with a dual deployment system The only caveat is that some cutting and pasting will be in order to piece together the true trajectory from the trajectory data files Vacuum Total Impulse Some users who attempt to program a pre existing motor into Splash may find a small bit of confusion in the entry of total impulse The performance parameters of many motors are listed under vacuum conditions Splash requires parameters to be under sea level conditions In the event one is unaware a total impulse conversion between these two conditions is rather trivial SeaLevellmpulse VacuumImpulse NozzleExitArea 101 3 kPa BurnTime or if you prefer English units SeaLevellmpulse VacuumImpulse NozzleExitArea 14 7 psi BurnTime 50 Known Bugs Excessive pitch oscillation during ballistic descent Currently the only known bug in Splash concerns yaw pitch damping during ballistic descent after the vehicle experiences extremely high angles of attack approx gt 160 degrees Rooted within the yaw pitch damping algorithms the bug results in a grossly underdamped yaw pitch oscillation This oscillation will eventually dampen out rather quickly onc
64. of instantaneous thrust levels N that correspond to the times listed in line 6 The first and last of the listed thrusts should always be 0 e DI 8 Must contain the data block termination string 9 15 Identical in format to lines 2 8 but concerning motor number 2 16 22 Identical in format to lines 2 8 but concerning motor number 3 23 29 Identical in format to lines 2 8 but concerning motor number 4 30 36 Identical in format to lines 2 8 but concerning motor number 5 It should at this time be noted that the thrust time curve entered is scaled such that a simple trapezoidal integration of the scaled thrust time curve will precisely match the user defined total impulse Below is a sample propulsion system data block It represents a 2 motor cluster of N class motors Notice that motors 1 4 and 5 while still in the data file provide no input to vehicle performance as they have no propellant total impulse or nozzle exit area MOTORS Motors Null EDX Type 0 0 Ignition delay 0 0 Off centerline distance 0 0 Hell Del Propellant It Aexit 0 0 1 0 1 0 Time 0 1 0 Thrust Motors Customl EDX Type 0 0 Ignition delay 0 25 Off centerline distance 13 5 31 610 4e 3 Propellant It Aexit 0 0 0 01 0 13 0 23 1 12 2 24 4 16 4 96 6 14 Time 0 2343 2003 1870 1310 1354 1434 450 O Thrust Motors Customl EDX Type 0 0 Ignition delay 025 Off centerline
65. ominal mission outlined in the input windows One file is produced for each stage 1 3 and an additional file is generated that tracks the topmost active stage I E generates a single nominal trajectory based on the trajectories of all activated stages Each trajectory file tracks a total of 33 parameters While more detailed discussion is found in the sections of the manual dedicated to the console application it may suffice to say that the data tracked is the following in tabular format Column Description Time Total time elapsed since beginning of simulation s Longitude Longitude deg Latitude Latitude deg Altitude Altitude m or ft ASL Azmth Body azimuth deg Eleva Body elevation deg Roll Body roll deg AbsVel Velocity with respect to the center of the Earth m s or ft s RelVel Velocity with respect to a point on the surface of the Earth at the same longitude and latitude as the vehicle m s or ft s AirVel Velocity with respect to the local air i e air speed m s or ft s YawRt Yaw rate deg s PitRt Pitch rate deg s RolRt Roll rate deg s Gamma Flight angle deg Headg Heading deg Mach Mach number AOA Angle of attack deg Axial Axial aerodynamic force N or lbf Ca Axial aerodynamic force coefficient normalized to the vehicle s nominal frontal area Normal Normal aerodynamic
66. ono nannnos 14 32 A n E 10 MN aara a NEEN 12 V Velo dene dee ed S eEiedet e 27 48 W Wed coa 33 weather cocking oooooccnocococononconnnonnncnncnoconocnnonnos 33 WGS 284 ee A AER AE 7 13 55 WIN init 13 15 32 33 Y Isa aser 27 48 55 Z DPP Age 32 55
67. or pointing Straight up while a 90 degrees specifies a velocity vector pointing Straight down This parameter is most likely useful to those using barometer based deployment devices or a 6DOF inertial measurement unit IMU Change in flight angle Immediate This parameter does not actually track any simulation variables The test in question is immediately valued as true and the simulation moves on to the next criterion test line Note that the direction and trigger values are still required as place holders but do not actually have any effect on simulation behavior Mach number Trigger value is unitless This parameter should only be used if the vehicle in question utilizes a barometric unit Change in Mach number ZIB Never This parameter does not actually track any simulation variables The test in question is perpetually valued as false and the simulation never moves on to the next criterion line and thus never stages deploys Note that the direction and trigger values are still required as place holders but do not actually have any effect on simulation behavior Atmospheric pressure Trigger value units are Pascals Obviously this parameter should only be used if the vehicle in question utilizes a barometric unit Change in atmospheric pressure OS Dynamic pressure often referred to as Q Trigger value units are Pascals Obviously this parameter should only be used if the v
68. ow Once opened the Launch Site window will appear similar to the window shown below 12 Launch Site Properties Wind Altitude Im ASL oo ME 9 9 LW a LW LW 9 9 mm a LW mm 9 LR LW LW 9 9 E mm na Direction my mM corn CO ao 2 ME mm mm mm em mm mm mm Atmosphere GE Temperature C 25 Pressure mmHg 760 Location Longitude 77 0361 Latitude 38 69711 Altitude Im ASL 75 Rail Data Azimuth 270 Elevation 85 Length m 0 914 Impact Zone Altitude m ASL tA OK Cancel The Launch Site input window The contents of each input box in the launch site window is as follows Classification Column Box Description Wind Altitude The altitude m or ft ASL for which the wind data direction and speed in the next columns is valid Direction The direction degrees from which the wind is originating An angle of zero degrees defines a wind from the North an angle of 90 degrees defines a wind from the East etceteras Speed The speed m s or ft s at which the wind is blowing Atmosphere Temperature The ambient temperature deg C or F at the launch site This data is used to determine the local air density and thus the correct density altitude It is not however used to modify local sonic conditions Pressure The barometric pressure mmHg or inHg at the launch site This data is us
69. pneumonic UNCERTAINTY 2 Contains the total number of iterations desired For mission planning is all you will want but for a full blown splash pattern to be submitted to the FAA as part of a launch license application 5 000 10 000 are probably better numbers 3 Contains the launch mass 1 sigma uncertainty as a percentage of the total mass 4 Contains the 1 sigma uncertainty of the moments of inertia as a percentage of the moment of inertia for the axis in question 5 Contains the 1 sigma uncertainty of the location of the center of gravity as a number of calibers 6 Contains the 1 sigma uncertainty in axial aerodynamic force coefficient Ca as a percentage 7 Contains the 1 sigma uncertainty in normal aerodynamic force coefficient Cn as a percentage 8 Contains the 1 sigma uncertainty of the location of the center of pressure as a number of calibers 9 Contains the 1 sigma uncertainty of the fin cant angle in degrees 10 Contains the 1 sigma uncertainty of each rocket motor s total impulse as a percentage of the total impulse 11 Contains the 1 sigma uncertainty of the propellant mass for each rocket motor as a percentage of said mass 12 Contains the 1 sigma uncertainty for each motor s thrust alignment i e thrust misalignment in degrees 13 Contains the probability of an ignition failure for each motor as a percentage 0 indicates a 100 reliable ignition 100 indicates a 100 likelihood of ignition failure 14 Cont
70. re the 2nd order normal force coefficients corresponding to the Mach numbers listed in line 3 7 Must contain the data block termination string A sample center of pressure data block may be seen below CP For each Mach CP AOA A B AOA C AOA 2 0 0 0 2 Oc 0 9 0 95 1 05 heel Mach 14 14 14 13 13 13 A 0 01 0 01 0 01 0 01 0 01 0 01 B 0 0 0 0 0 0 0 0 0 0 0 0 O Fin Data Block While the overall aerodynamic properties of the vehicle are primarily contained within the other data blocks the fin data block while obviously containing information on the vehicle s fins is concerned with vehicle yaw pitch damping and roll and does not effect simple axial or normal force calculations 1S Splash uses some non standard methodologies that appear to yield reasonable results while reducing the degree of sophistication required of the user in producing input data 37 Before line by line discussion of the format of the fin data block it should be noted that several lines of the fin data block are devoted to defining the normal force coefficient of a single fin The method in which these coefficients are calculated is identical to that used in the Axial Force Data Block to calculate axial force coefficients The fin normal force coefficients are not however used to calculate axial or normal forces experi enced by the vehicle they are used strictly for calculations involving yaw pitch damping and roll
71. referred to as the base file name In addition to the conventions listed above scenario and stage data files employ the use of data blocks Data blocks are small clusters of data to break down the file into more intuitive easier to use chunks of data For example each stage data file contains a propulsion system data block As one might guess the this data block contains all data pertaining to the rocket motors for that particular stage While data within each individual data block must be found in a particular order it should be noted that the order 30 data blocks appear in a file is unimportant This means that one may place often modified data blocks at the top of a file to facilitate faster modification due to the ease of finding the desired block in a text editor Scenario Files Scenario data files contain all information required to set up a launch that is not related to the rocket itself In other words scenario data files contain information on the launch rail the weather the local terrain and any uncertainties Scenario data files are identified by a file extension of scn In other words if the base file name is alpha the corresponding scenario data file must be named alpha scn A description of each data block listed in alphabetical order found in the scenario data file is as follows Rail Data Block As it s name implies the rail data block contains all information pertinent to the launc
72. rom the launch rail Impact Zone Altitude The altitude m or ft ASL of the impact zone s terrain Most of the time this will be the same as the launch rail altitude but not always An obvious exception to this rule would be an air launched system Uncertainties The primary purpose of Splash is to generate splash patterns for sounding rockets Obviously one must possess a working knowledge of the uncertainties associated with any given vehicle and launch scenario The Uncertainties input window defines these uncertainties The Uncertainties window is accessed through the Scenario pull down menu found at the top of the main Splash window Once opened the Uncertainties window will appear similar to the window shown below a be Scenario Uncertainties Iterations 1 Wind Mass Properties Direction deg Velocity m s Mass Moments of Inertia Launch Rail TE Center of Gravity cal Azimuth deg Aerodynamics Elevation deg Ca Failure Likelihood Cn Ignition 0 SE CATO n Fin Cant deg Deployment 0 5 Propulsion Chute Failure 0 5 Total Impulse Propellant Thrust Axis deg AE E At Kei A a The Uncertainties input window 14 The contents of each input box in the uncertainties window is as follows Classification Column Box Description Iterations The number of iterations one desires to run for the given scenario It
73. rt into other applications the Splash GUI does include it s own albeit limited capability to quickly examine these text files in a graphical environment Each of these text files and the Splash GUI interface for examining them is discussed below Splash Pattern Files Window AS one may imagine the splash pattern data file contains the impact locations longitude and latitude for each stage for each Assuming a scenario base filename of alpha the splash pattern data file will be named spash_spl out A crudely formatted graphical representation of this data may be viewed by selection Splash Pattern from the Output pull down menu at the top of the Splash GUI s main window Those who endeavor to import the data in the splash pattern file into other applications no doubt harbor a desire to know the exact formatting of the splash pattern file In tabular format the columns found with the splash pattern data file are as follows Column Description Run The iteration or run number While most runs include the randomization required of a Monte Carlo analysis it should be noted that the 0 run does not include any randomization In other words the 0 run is the nominal trajectory lLongitude Longitude of the 1 stage impact point in degrees A negative angle corresponds to West longitude lLatitude Latitude of the 1 stage impact point in degrees A negative angle corresponds to South latitude
74. s mass properties thrust curves or any other performance parameter These parameters are instead required as input from the user The user may obtain such data from other programs hand calculations actual test data a Ouija board or any other means the user deems up to the task Splash merely integrates the performance data and puts it in motion Thus the user will be required to independently provide the following data for each stage in no particular order e Gross vehicle geometric properties o Length o Nominal diameter and thus frontal area e Mass properties o Mass o Center of gravity as a function of mass o Moments of inertia at launch o Products of inertia at launch e Aerodynamic properties o Caas a function of Mach and AOA o Cb as a function of Mach and angle of attack AOA o Cn as a function of Mach and AOA o CP asa function of Mach and AOA e Fin information o Location number and dimensions e Propulsion system o Thrust time curve o Propellant mass o Sea level total impulse o Nozzle exit area e Recovery system o Conditions of deployment o Diameter o Sub sonic drag coefficient e Current launch site conditions o Longitude latitude and altitude o Barometric pressure and temperature o Wind speed and direction as a function of altitude This is not entirely true but it is close enough for the purposes of this discussion S Examples of such programs include but are not limited to ADAM AeroCFD AP98 D
75. s capability Splash is intended not just for the nominal trajectory analysis that most simulations are but also for splash pattern generation consistent FAA OST requirements This means that Splash can provide the data used to determine not just a nominal impact point but an impact zone complete with statistics to back up the likelihood of a vehicle impact in any given region No other simulation package available at a reasonable price offers this capability Splash provides more capability and tracks more variables than other consumer level simulation packages and thus provide data that comes closer to matching reality available today Splash s features include Wind effects weather cocking Earth modeled as a rotating oblate spheroid Gravitational effects that vary with altitude and latitude An altitude model that extends to 632 km above sea level ASL Clustering of up to 5 motors per vehicle stage Uncertainty analysis for 18 different vehicle scenario parameters To better illustrate what all this means imagine your typical rocket simulation The simulation will say that the rocket goes up and comes down in a certain location Question What are the odds that the actual rocket would impact the exact location specified Answer About zero So how close to the simulation specified location can you expect your rocket to land Most simulations will provide no insight as to the answer of that second question Splash provides a realisti
76. s during flight modeling Vehicle The vehicle s modeled by Splash are assumed to be perfectly rigid axisymmetric bodies of up to 3 stages The specific aspects of the vehicle model have been broken down into more logical more manageable pieces mass properties aerodynamics and propulsion Mass Properties The mass properties tracked by Splash are as follows length nominal diameter mass center of gravity and the moments and products of inertia Length diameter and mass are obviously straightforward in nature the center of gravity as well as the moments and products of inertia do warrant additional discussion however The center of gravity is assumed to lie on the vehicle s axis of symmetry It does however move fore and aft as a function of mass as defined by the user For those not familiar with the WGS 84 model it is the primary Earth model employed by the Global Positioning Satellite GPS system For more information see Department of Defense World Geodetic System 1984 National Imagery and Mapping Agency NIMA document number NIMA TR8350 2 This document is available to the public for download at http www nima mil The vehicle s local coordinate system is centered about the current center of mass and orientated similar to industry standard X forward Y port Z up A sketch illustrating the local vehicle coordinate system Aerodynamics Given Splash s assumption of an axisymmetric vehic
77. ure Pa or psi delta Atmospheric Pressure Change in local atmospheric pressure Pa or psi Body Elevation Angle theta Vehicle body angle with respect to horizontal deg delta Body Elevation Angle dtheta Change in vehicle body angle with respect to horizontal deg Dynamic Pressure Dynamic pressure at leading edge Pa or psi delta Dynamic Pressure Change in dynamic pressure at leading edge Pa or psi Flight Angle gamma Velocity vector angle with respect to horizontal deg delta Flight Angle dgamma Change in velocity vector angle with respect to horizontal deg Immediate Immediately evaluate test as true do not use the test in question Mach Number Vehicle Mach number delta Mach Number Change in vehicle Mach number Never Never evaluate test as true never stage deploy Time Current elapsed time since launch s delta Time Change in elapsed time s 7 Three bone fide tests are rarely required in the world of hobby rocketry two tests is usually enough to handle even the largest project Still the third test is provided to cater to the 1 ers out there The value of the parameter in question at the start of the current test is used as the baseline for all delta parameters I E a delta Time of 0 1 commands the simulation to Wait 0 1 second regardless of how much time has elapsed since the simulation started Sometimes referred to
78. xial force multiplier eee eect cetera 16 azimuth isein 14 15 27 31 48 55 B barometric Pressure ocooccoccconcnoncnnncnnnnanonnnono 13 33 A neiii ei 16 35 55 base file name 12 30 DaSe Pressures O 36 body elevation angle eee eeeeeeeeeeeee 43 OT 51 C Clyne 15 16 27 32 48 55 case tal iii 15 tte Eed EE 15 CATO cuore liada ae 32 55 A aot E E 16 55 center Of gravity eee 7 15 19 32 36 55 center Of Dreseure 15 32 36 55 center of pressure offeet 17 Clustered MOTOTS 0 0 eee eee eeeceeeceseceseesseesees 20 L EE 15 17 27 32 48 55 console application ooooonncnnccnocnconnconcconoconccnnos 29 coordinate system oe eee eee eee eeseeeteeeeeeeaee 39 A AEE E See center of pressure D E E 17 data DlockKS 0 cionado 30 density altitude oooconoccnncniccnnccnonnconocanoconoconocnnos 33 deployment ee ee cee canon noc nccnncnnnonno 15 43 deployment failure eee ceeeceeeeeeenees 32 TE EE 7 19 di ie de 55 56 dual deployment ooooccocccocononcncnconnnancnanocnocnnonnos 50 dynamic pressure oo eee eee cette cerns 44 55 E atb nee Ee EE EE H elevation oooooococononcncnnnnnnnns 14 15 27 31 48 55 EXECU O is 24 45 F ENK EE 15 O E 18 AT CAN ae 15 18 32 OS a A A 17 37 Ti Pht AN Be tai 27 48 G E 27 48 COM ia 18 19 e EE H gun launched ooooconoccnononononononnnconcnonoconocnncnnocnnos 31 H II EE 27 48 horizon detector oeiee ianiai es 43 I ignition delay oooocononoconoc

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