IMFD IMFD to Moon's satellite

[PaulG]

The moon is a satellite around Earth and I've used IMFD quite successfully to get from the Earth to the Moon. But, what about using IMFD from the Moon to a satellite around the moon?

I'm having an issue here. I'm sitting at Brighton Beach on one of the pads. I set the IMFD parameters, setting target plane as the path. First, the injection angle (to the target) is nearly 180 ° meaning that when I approach the satellite I'm approaching it from the opposite direction. Why is IMFD doing that?

So, I switch the mode from Prograde to Retrograde, target plane as the path and now my injection angle is nearly 0 °. But as soon as I launch and start to head along the vector stated by IMFD the calculations start to go haywire and I no longer have a target vector.

Any ideas as to what is going on?

Thanks.

 

[Cras]

I am not sure, but you may be using IMFD out of bounds here.

I assume you want to rendezvous with a man-made satellite that is in orbit around the Moon. How I would go about, it use LaunchMFD to get me a launch heading. Then you launch. The Moon rotates so slow, that it may not pay to sit there and wait for it to fly over your loation. Rater, launch, and then make plane corrections as you are on your way up. Then use RendezvousMFD to set up the approach.

 

[PaulG]

Yeah, its easier that way, but not the most fuel efficient.

 

[Cras]

It depends on the pilot. If you use the first solution that is given to you by Rendezvou MFD, then yhea, you will use more fuel than you need to. These are only tools, you gotta know how to use them.

You want to be as fuel efficent as possible, you wait for up to a month until the thing flies right over your head, then fly straight up at it, and cut out any sort of plane corrections in the initial burn, the burns to dip the periapsis for rendezvous. Just aim for an orbit about 5k lower than the object, slightly behind it, and the rest is pretty basic stuff.

I am just not sure IMFD is able to be used in the manner you described. I have used it a few times before to meet up with the ISS in LEO, but not for when to launch. I used other tools to find out when and how to launch, and then use IMFD in orbit to sync up with the ISS.

 

[PaulG]

So, I don't understand why IMFD isn't working well. I'm almost positive (please correct me) that you can plan an IMFD path from Earth to ISS and certainly from earth to Moon, both are satellites of Earth. So, why not a satellite around the moon?

Again, IMFD can get me to target, its just I'm coming from the opposite direction.

 

[orbekler]

So, I don't understand why IMFD isn't working well. I'm almost positive (please correct me) that you can plan an IMFD path from Earth to ISS and certainly from earth to Moon, both are satellites of Earth. So, why not a satellite around the moon?

Again, IMFD can get me to target, its just I'm coming from the opposite direction.

Well, this is what I did for the Luna-OB1 from Brighton Beach:

Course target: Luna-OB1;
Surface Launch->Lunar Off-plane;
Set Target and TIn of Surface Launch = to Course Target and TIn;
Heading suggested of 46°.

As you can see EIn=~0°



Then it's a normal Off-Plane, you have to sync planes, so you can use the IMFD Orbital velocity match program, or the standard Sync MFD.

I didn't have problems with retrograde orbits, but if you did, you can always enable Course Offset->Vel. Frame->Retrograde (but it should not be that way).

 

[orbekler]

...So, I switch the mode from Prograde to Retrograde, target plane as the path and now my injection angle is nearly 0 °. But as soon as I launch and start to head along the vector stated by IMFD the calculations start to go haywire and I no longer have a target vector.

Any ideas as to what is going on?

Thanks.

Well, I just remind now that it happened something similar, but that was because I was almost in a polar orbit, and just with few degrees of uncertainty switched from prograde to retrograde, so Hto was messing up. But it wasn't a IMFD problem.

 

[PaulG]

Well, the satellite I have is in polar orbit. But, I've tried retrograde to Luna as well (to experiment) and the same wacky thing happened.

 

[dgatsoulis]

Can you post the scenario with the IMFD plan here, so we can reproduce the problem? Also which version of IMFD are you using?

 

[orbekler]

Well, the satellite I have is in polar orbit. But, I've tried retrograde to Luna as well (to experiment) and the same wacky thing happened.

I used the standard XR-2 on Brighton Beach, and it worked. However, the problem with polar orbit is that IMFD works only in Pro or Retro.

In the following example, the application was different, but the problem was the same you described: for some reason IMFD disrupted the HTO that few minutes before was perfect.


This is because I was very close to the polar orbit, let's say 89.9°, and due to uncertainty I shifted to 90.1° or so.

IMFD tried to force the Prograde, so I got the problem, that was clearly visible seeing the Map MFD (almost "vertical" orbit).

If you're staying, let's say, to the equator, and you got a satellite exactly at polar orbit, will be very difficult to get it with IMFD (don't know about TransX).

Dgatsoulis is right, post your Scenario.

 

[PaulG]

Hi. Thanks. I've uploaded the scenario.

It seems as though its due to the extreme inclination. When I used this same scenario and dropped it to 50°, it worked like a charm.

 

[dgatsoulis]

Hi. Thanks. I've uploaded the scenario.

It seems as though its due to the extreme inclination. When I used this same scenario and dropped it to 50°, it worked like a charm.

You are at least one week away from a direct ascent.

You can dock to the target in two ways. Either wait for the "groundtrack" of the sattelitte, to pass over your launch site, or launch far away from the moon (but still in orbit) and align the planes when needed.

BEGIN_SHIPS
Ramorant:DeltagliderIV
  STATUS Landed Moon
  BASE Brighton Beach:2
  POS -33.4450608 41.1217129
  HEADING 59.83
  RCSMODE 2
  PRPLEVEL 0:1.000000 1:1.000000 2:0.983333
  IDS 0:45 100
  NAVFREQ 486 542
  XPDR 0
  ;-------------------------- Skin parameters must contain directory name of skin (without space) 
  MeshSkin ClassicDG
  ;-------------------------- Cargo payload must contain name of config file or "none".(see doc) 
  CargoPayload none
  NOSECONE 0 0.00
  GEAR 1 1.00
  AllDoorsState 0 0.00 0 0.00 0 0.00 0 0.00 0 0.00 0 0.00 0 0 0.00
  But1Cockpit 0 0 0 2 2 2 1 2 2 2 2 2 2 2 2 1 1 2 1 1 1 3
  But2Cockpit 0 0 0 0 1 0 0 0 2 2 2 2 0 0 1 0 0 0 2 2 0 0
  TransEffect -1
  LifeBut1State 0 2 1 2 1 2 2 2 2 2 2 2 2 0 3
  LevelBatt 127.2193
  Emergency_power 10000.0000
  VoltageStartBus 0.0000
  VoltageGen1 96.4824
  VoltageGen2 98.7331
  VoltageGenBus 96.4824
  O2tankALevel 0.0000
  N2tankALevel 99.9998
  O2tankBLevel 66.7800
  N2tankBLevel 100.0000
  CabinO2Level 21.3826
  CabinCO2Level 600.0000
  CabinTempLevel 21.2000
  CabinPressure 14.7000
  CabinMoistLevel 36.0000
  CabinDustLevel 0.0001
  CabinO2Setting 21.4000
  CabinTempSetting 21.2000
  CabinPressSetting 14.7000
  AntennaTarget Brighton_Beach
  O2ConsumptionSetting 1
  FuelConsumptionSetting 1
  MainenginePower 1
  ;------------------Crew parameters  UMMUCREW Function-Name-Age-CardiacPulse-WeightKg (fonction of Pilot must be: Capt) 
  NoOneOnBoard 0
  NoPilotOnBoard 0
  UMMUCREW Capt-Paul_Gerst-41-108-77
  UMMUCREW Chem-Mike_Hintz-35-102-91
  UMMUCREW -Frank_Bundesmann-22-99-91
  UMMUCREW Sci-Hugh_Bestellen-44-82-91
  UMMUCREW Eng-Craig_Shiler-28-107-91
  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
  UCGO @@0,1,0,0,@@1,1,0,0,@@2,1,0,0,@@3,1,0,0,
END
CRG-01:DGIVMTKSSAT
  STATUS Orbiting Moon
  RPOS -680283.02 7299068.91 4508977.11
  RVEL -156.020 -401.984 620.524
  AROT -15.94 -73.73 163.70
  AFCMODE 7
  NAVFREQ 0 0
  PowerUpStep 6
END
END_SHIPS

 

[PaulG]

Hi. Thanks. Yes, I'm aware of the options. However, one of the benefits of IMFD is to find the "least expensive" route to a target. In this case, for some reason, it won't do that. I'm just trying to understand what it is that is prohibiting. In Prograde mode it works fine, but approaches the target from the opposite direction (EIn 180°). The only way I see that IMFD calculates a near zero EIn is in retrograde mode. But, once flying on the vector suggested by IMFD, the calculations seem to "go wonky".

 

[PaulG]

Ok. Issue has been resolved. Here is what I learned.

IMFD from the moon doesn't appear to work in retrograde mode. Don't know why, but it doesn't. But, I figured the work around.

Set the course to the satellite in prograde mode (standard), set the target angle to as close to 180° as possible. Then, instead of flying along the vector suggested, fly 180° opposite. The program will recalculate, flip and work perfectly with an incoming angle near 0°.

Alternatively, if you can't do the math in your head, set it up for Retrograde and adjust as close as possible to 0°. Then, hover, point in the direction, set the program to prograde and go. Same thing will happen.

Perfect result, perfect course, minimal fuel usage.