I need some serious Interplanetary Help

[James.Denholm]

I think you use the Orbital program to circulise your orbit and so on.

[Pirx]

GXE3, for Orbital and SlingShot see the end of this post

http://orbiter.dansteph.com/forum/index.php?topic=10894.msg172497#msg172497

then ask whatever is not clear about Orbital.

I may try to fly "Martian Bound VEEP" DGIV mission with IMFD and see if I would have any success with SlingShot. As I
have writen before SlingShot takes your current position and velocity as input. For a target trajectory you would
usually connect it with Course. For example (related to this particular mission), first you select a course from Saturn to
Jupiter. When near Jupiter (SOI), change Course to Target Intercept Src: Jupiter, TGT: Mars, REF: Sun, TEj: the time of
your closest approach to Jupiter. Connect SlingShot with Course, start varying TIn on Course and see if SlingShot
shows any acceptable solution ( e.g., one that does not go through Jupiter or require twice the fuel you
have ). You may find one, or not. The problem is that with IMFD you cannot plan the slingshot while still in orbit
around Saturn. Then you would have had more freedom in also choosing TIn for the Saturn-Jupiter leg.

[Pirx]

Somehow the Saturn-Mars journey (possibly via Jupiter) in 'Martian Bound VEEP' does not appeal to me. It seems to
require some very high (hyperbolic relative to Sun) speeds unless some cheating is done about DGIV O2 reserves. But
here is an interesting topic at M6:

http://orbit.m6.net/Forum/default.aspx?g=posts&t=19321

Earth - Venus slingshot - Mars - Earth

I have converted it to a DGIV scenario using IMFD v5 or v5.1:

Code: [Select]

BEGIN_DESC
Earth - Venus flyby - Mars - Earth
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 55550.5033311922
END_ENVIRONMENT

BEGIN_FOCUS
  Ship DGIV-VENUS01
END_FOCUS

BEGIN_CAMERA
  TARGET DGIV-VENUS01
  MODE Cockpit
  FOV 50.00
END_CAMERA

BEGIN_HUD
  TYPE Surface
END_HUD

BEGIN_MFD Left
  TYPE User
  MODE Interplanetary
  Scenario Old
  MapMFD V5
  Reference Auto
  Target none
  Center GravityRef
  Data 0 1 1e-006 1 0 0 0 0 1 0 0 0
  MassLimit 1e+020
  CMode 0
  Config 1 1 1 1 0 0
  ExtMode 0
  Periapis none
  END
  CorMFD V4
  Reference Sun
  Target Venus
  Source Earth
  ActiveProg 1 1
  DataA 0 3 0 0 0 0
  DataB 1 10 55551.50070446761 0 0 5.959131075278256 0 55688.88236368058 0
  DVProg 0 0 0 1
  AdvConf 0 0 1 0 0
  Guidance 0
  END
  EjectMFD V5
  Reference Auto
  Data 0 1 3 0 1 55531.66680966428 10
  Guidance 0
  END
  BaseAprMFD V2
  Reference Auto
  Target none
  Source none
  DataA 0 0 120000 0.10821 0.366519 1 1 55531.66680966428 55531.66680966428 0
  DataB 0 3 0 1 0 1
  END
  SlingMFD V4
  Reference Auto
  Source none
  Data 0 1 1 3 0 1 55531.66680966428 0
  END
  LaunchMFD V4
  Target None
  Data 0 1 1 3 0 1 0
  END
  CF1_DataA 1 1
  CF1_DataB 55550.5005318403 10 120000 1 5 150000
  CF1_SecTgt
  mfdShare -1
  mfdProgram 2
END_MFD

BEGIN_MFD Right
  TYPE User
  MODE Interplanetary
  Scenario Old
  MapMFD V5
  Reference Auto
  Target none
  Center GravityRef
  Data 0 1 1e-006 1 0 0 0 0 1 0 0 0
  MassLimit 1e+020
  CMode 0
  Config 1 1 1 1 0 0
  ExtMode 0
  Periapis none
  END
  CorMFD V4
  Reference Sun
  Target Mars
  Source Venus
  ActiveProg 1 1
  DataA 0 3 0 0 0 0
  DataB 1 100 55688.8825246065 0 0 1.60744564933409 0 55831.8687292477 0
  DVProg 0 0 0 1
  AdvConf 0 0 1 0 0
  Guidance 0
  END
  EjectMFD V5
  Reference Auto
  Data 0 1 3 0 1 55531.6669700115 10
  Guidance 0
  END
  BaseAprMFD V2
  Reference Auto
  Target none
  Source none
  DataA 0 0 120000 0.10821 0.366519 1 1 55531.6669700115 55531.6669700115 0
  DataB 0 3 0 1 0 1
  END
  SlingMFD V4
  Reference Auto
  Source none
  Data 0 1 1 3 0 1 55531.6669700115 0
  END
  LaunchMFD V4
  Target None
  Data 0 1 1 3 0 1 0
  END
  CF1_DataA 1 1
  CF1_DataB 55550.5005318403 10 120000 1 5 150000
  CF1_SecTgt
  mfdShare -1
  mfdProgram 2
END_MFD

BEGIN_PANEL
END_PANEL


BEGIN_SHIPS
ISS:ProjectAlpha_ISS
  STATUS Orbiting Earth
  RPOS 1616846.28 6137318.64 -2045448.23
  RVEL 7341.377 -2244.720 -798.560
  AROT 109.97 -9.67 80.03
  PRPLEVEL 0:1.000
  IDS 0:588 100 1:586 100 2:584 100 3:582 100 4:580 100
  NAVFREQ 0 0
  XPDR 466
END
Mir
  STATUS Orbiting Earth
  RPOS 5634095.11 223067.94 3634486.85
  RVEL -4231.182 392.529 6454.155
  AROT 0.10 -45.67 89.93
  IDS 0:540 100 1:542 100 2:544 100
  XPDR 482
END
Luna-OB1:Wheel
  STATUS Orbiting Moon
  RPOS 1988266.12 -1164554.24 8939.14
  RVEL 773.039 1265.188 2.596
  AROT 0.00 0.00 -49.69
  VROT 0.00 0.00 10.00
  IDS 0:560 100 1:564 100
  XPDR 494
END
DGIV-VENUS01:DeltagliderIV
  STATUS Landed Earth
  POS -80.6754710 28.5189110
  HEADING 66.55
  RCSMODE 0
  PRPLEVEL 0:1.000 1:1.000 2:0.983
  IDS 0:45 100
  NAVFREQ 0 0
  XPDR 0
  ;-------------------------- Skin parameters must contain directory name of skin (without space)
  MeshSkin spacetech
  ;-------------------------- Cargo payload must contain name of config file or "none".(see doc)
  CargoPayload DGIVMTKSSAT
  NOSECONE 1 1.00
  GEAR 1 1.00
  AllDoorsState 1 1.00 1 1.00 1 1.00 0 0.00 1 1.00 1 1.00 0 1 1.00
  But1Cockpit 0 0 0 2 2 2 0 2 2 2 2 2 2 2 2 1 1 2 1 1 1 5
  But2Cockpit 0 0 0 0 0 0 0 0 2 2 2 2 2 0 98 0 0 0 1 1 0 0
  TransEffect 0
  LifeBut1State 0 2 1 2 1 2 2 2 2 2 2 2 2 0 3
  LevelBatt 100.0000
  Emergency_power 10000.0000
  VoltageStartBus 0.0000
  VoltageGen1 96.2800
  VoltageGen2 96.2800
  VoltageGenBus 96.0000
  O2tankALevel 99.9931
  N2tankALevel 100.0000
  O2tankBLevel 100.0000
  N2tankBLevel 100.0000
  CabinO2Level 21.3841
  CabinCO2Level 350.0568
  CabinTempLevel 15.6389
  CabinPressure 14.6988
  CabinMoistLevel 42.0579
  CabinDustLevel 0.0002
  CabinO2Setting 21.4000
  CabinTempSetting 21.2000
  CabinPressSetting 14.7000
  AntennaTarget no_target
  O2ConsumptionSetting 5
  FuelConsumptionSetting 2
  MainenginePower 1
  ;------------------Crew parameters  UMMUCREW Function-Name-Age-CardiacPulse-WeightKg (fonction of Pilot must be:
Capt)
  NoOneOnBoard 0
  NoPilotOnBoard 0
  UMMUCREW Capt-Mike_Speedo-41-78-79
  UMMUCREW Eng-Frank_Turno-51-74-67
  UMMUCREW Clim-Phillip_LeDux-46-68-79
  UMMUCREW Spe-Christian_Stewart-29-78-75
  UMMUCREW Spe-Roger_King-26-77-66
  FailGearFailure 0
  FailGearCollapse 0
  FailLeftMainEngine 0
  FailRightMainEngine 0
  FailHoverEngine 0
  FailRcs 0
  FailSurfaceControl 0
  FailComputer 0
  FailComputerBlueScreen 0
  FailAutopilot 0
  FailExtRadiator 0
  FailAirbrake 0
  FailNoseCone 0
  FailCanopy 0
  FailAntenna 0
  FailLeftTurbo 0
  FailRightTurbo 0
  FailCargoDoor 0
  SpacesuitTimer 0
END
END_SHIPS

BEGIN_ExtMFD
END
The left IMFD contains the Earth - Venus plan, the right one is set up for Venus - Mars. Execute the trip to Venus just
as if it were your final destination. Near Venus set the left IMFD to share its state with the right one (ID: 1) and select
Sling-shot program. Slave Sling-shot to Course (that would be the Venus-Mars course from the right IMFD). Correct
the trajectory as indicated by the left IMFD and fly by Venus on your way to Mars. From Mars return directly to the
Earth. It is doable and fun - I did it.

Note: There is no way to find or plan this sling-shot using IMFD. But if you have the parameters (Earth eject
time, Venus fly-by time, Mars arrival time) you can execute it using IMFD.

[GXE3]

Thanks

[James.Denholm]

Nice!

EDIT: I wonder when the next window for this type of launch will be...



Post Edited ( 03-17-08 00:03 )

[Pirx]

James.Denholm wrote:
EDIT: I wonder when the next window for this type of launch will be...

You should check the m6.net thread (link in my previous post)... once the forum recovers from its usual Sunday downtime.

What I remember (and I was slightly incorrect - now updated) was there was no other possibility using similar initial delta-V for 103 years or so (later dates were not checked) but with some increase of the delta-V budget there were more frequent windows.



Post Edited ( 03-17-08 20:33 )

[James.Denholm]

Whoooo... rare. I wonder if any space agencies will take advantage of the window...

Actually, it would be pretty funny if they all did. I mean, according to wikipedia,
http://en.wikipedia.org/wiki/List_of_space_agencies
there are about 47 that are still active (yes, I know, many can't launch even a firework yet, but that might change in 2
years...), and I suppose it would be pretty humorous if they all started crashing into each other (and yes, I do know that
the chances of that happening are minuscule).

[ar81]

I have a question.  How do I understand visually what a tangential transfer is.
Technically speaking you always have an ejection that is tangential to your current trajectory...
so I do not seem to understand what it is.

[Pirx]

Sorry, but what do you mean by "you always have an ejection that is tangential to your current trajectory"? If you mean the trajectory after the burn then, yes, it is tangential to itself

Here is an example of non-tangential transfer (Left: IMFD - Course - Target Intercept) and a tangential one (Right: IMFD - Course - Tangential Transfer)



As you can see, on the left the transfer trajectory (blue) is not tangential (not parallel at the intersection points) to either the source trajectory (Earth, green) or the target trajectory (Mars, yellow). The variables EjA and InA show the angle between the source and transfer trajectory at the ejection point and the angle between the transfer and target trajectory at the injection point.

On the right the transfer trajectory (blue) is tangential (parallel at the intersection points) to both the source trajectory (Earth, green) and the target trajectory (Mars, yellow). IMFD Tangential Transfer is essentially "Automated Transfer MFD". It calculates the hypothetical delta-V automatically, so that the transfer trajectory "just touches" the target trajectory. The point where this occurs is indicated by the white radius. The target position at the same time is indicated by the dashed yellow radius. Your goal is to modify TEj so that both the white and the dashed yellow line overlap.



Post Edited ( 06-10-08 20:47 )

[ar81]

If I understand it correctly, a tangential transfer minimizes the orbit insertion burn as it barely touches target orbit, so
it is like shuttle docking to MIR.

[GXE3]

I don't use Tangential Transfer when I'm using the DGIV. It's a waste of time. Target Intercept is easy and quick.



Post Edited ( 06-11-08 00:36 )

[GXE3]

How do you convert DV into the amount of fuel?



Post Edited ( 06-11-08 00:36 )

[Pirx]

ar81 wrote:
If I understand it correctly, a tangential transfer minimizes the orbit insertion burn as it barely touches target orbit, so it is like shuttle docking to MIR.

For a transfer between two circular (or close to circular) trajectories - yes. Then Tangential Transfer = Hohmann Transfer. As a matter of fact Tangential Transfer is very useful for rendezvous with other ships/orbital stations. If the source and/or target trajectories are highly eccentric ellipses, sometimes a better solution may be found. But Tangential Transfer would still be close.

GXE3 wrote:
How do you convert DV into the amount of fuel?

From Tsiolkovsky's rocket equation

M1 = M2 * exp(dV / Isp)
M2 = M1 - Mf

where

M1 - the mass of the ship before the burn
M2 - the mass of the ship after the burn
Mf - the mass of fuel burned
dV - delta-V
Isp - the specific impulse, in m/s (= Isp in seconds multiplied by g = 9.806 m/s^2)

Mf = M1 (1 - exp(- dV / Isp))

For dV significantly smaller ( > 10 times ) than Isp

Mf ~ M1 * dV/Isp

Isp can be calculated from the engine thrust (kN) divided by the fuel mass flow (kg/s). Both are displayed on DGIV middle panel. For DGIV "Moon" configuration Isp is 44000 m/s or (divided by g) =  4487 s. This is about 10 times what the current bipropellant rocket engines are capable of achieving.

Edit: Oh, and of course, if the calculation gives you Mf bigger than what you actually have, this means you cannot achieve the desired delta-V.



Post Edited ( 06-11-08 09:45 )

[ar81]

GXE3 wrote:
I don't use Tangential Transfer when I'm using the DGIV. It's a waste of time. Target Intercept is easy and quick.

IMFD has:
Planar intercept - Good for Earth to Moon/Sun to planets/central body to moons
Off plane - Most direct route (not necessarily more fuel efficient)
Tangential transfer - Minimizes delta V

[ar81]

Thanks Pirx.  I just uploaded the new version of IMFD and included what you posted on Tangential transfers.  Credits
are there, of course.  Keep up the good work!

[GXE3]

Pirx wrote:

ar81 wrote:
If I understand it correctly, a tangential transfer minimizes the orbit insertion burn as it barely touches target orbit, so
it is like shuttle docking to MIR.

For a transfer between two circular (or close to circular) trajectories - yes. Then Tangential Transfer = Hohmann
Transfer. As a matter of fact Tangential Transfer is very useful for rendezvous with other ships/orbital stations. If the
source and/or target trajectories are highly eccentric ellipses, sometimes a better solution may be found. But
Tangential Transfer would still be close.

GXE3 wrote:
How do you convert DV into the amount of fuel?

From Tsiolkovsky's rocket equation

M1 = M2 * exp(dV / Isp)
M2 = M1 - Mf

where

M1 - the mass of the ship before the burn
M2 - the mass of the ship after the burn
Mf - the mass of fuel burned
dV - delta-V
Isp - the specific impulse, in m/s (= Isp in seconds multiplied by g = 9.806 m/s^2)

Mf = M1 (1 - exp(- dV / Isp))

For dV significantly smaller ( > 10 times ) than Isp

Mf ~ M1 * dV/Isp

Isp can be calculated from the engine thrust (kN) divided by the fuel mass flow (kg/s). Both are displayed on DGIV
middle panel. For DGIV "Moon" configuration Isp is 44000 m/s or (divided by g) =  4487 s. This is about 10
times what the current bipropellant rocket engines are capable of achieving.

Edit: Oh, and of course, if the calculation gives you Mf bigger than what you actually have, this means you
cannot achieve the desired delta-V.

What does exp stand for?

[Pirx]

GXE3 wrote:
What does exp stand for?

exp is the exponential function
http://en.wikipedia.org/wiki/Exponential_function

For the record, this function is not available in the DGIV calculator ( D8 ).



Post Edited ( 06-20-08 20:22 )

[GXE3]

I sorry Pirx. That was a very stupid question. After a wrote the reply, I looked on my calculator and saw "EXP". :D

[Pirx]

That's OK. I am used to hearing how terrible the highschool education nowadays is

[GXE3]

I've been having trouble ejecting at the right time using the IMFD. Sometimes, the ejection times I set make the IMFD
reenter earth instead of ejecting out of earth. How do I fix this?

[Pirx]

Should not happen, if you choose your ejection time right. If you switch Orbit-Eject to Realtime and then back to Off-
axis, IMFD usually comes with a close to optimal TEj. You can tweak it slightly for some additional fuel economy.

[GXE3]

Ok. I think I was just getting confused between Realtime and Off-Axis.