Advanced Question Earth -> Object orbiting Moon

[Cras]

So I have an object in orbit around the Moon. Sent it up there about a month sim time ago.

I now am looking to launch a manned vehicle to rendezvous with that object.

I have yet to convince myself of the best way to do this. And since I have future plans of sending vehicles to the Moon and returning them back to Earth not for a direct re-entry, but rather to rendezvous with a space station, this is a procedure I really want to have.

Have any of you developed a good method for this? A transfer into a very specific orbit so to facilitate a rendezvous? Right now I am looking at just putting myself into a really high lunar orbit then plane change. Not very fuel efficient, and not something that would work going from say the Moon to a LEO space station.

 

[garyw]

Why not combine the plane change with the TLI burn or as part of a mid course correction?

 

[Cras]

that would certainly be ideal I would think. I am unsure of the tools to perform it however. I was looking around too see if IMFD could do it, but I am not sure.

 

[Loru]

AFAIK IMFD has tool to enter any orbit you desired. It's either planet aproach or orbit insert - or you have to combine them both for that kind of manuever.

 

[Cras]

I ended up using a mix of IMFD and LTMFD to some very good results.

Actually used IMFD's target intercept program when in the Moon's SOI, and it to me on track. Then used LTMFD for the LOI. Was then a simple manner of setting up another burn of little dV using IMFD to finish the rendezvous.

 

[jedidia]

Plane change in mid-course correction will be more propellant-efficient than plane change in TLI burn. In general, if you want to rendevouz with an object orbiting another body, you need a two-plane transfer, unless you want to synchronize planes when you're already in orbit around the target body, which is again less efficient (general rule: plane change needs less DV the further you are from the body in question).

 

[flytandem]

Could be a fun challenge. Could you post the scenario with the object you have in lunar orbit?

 

[Cras]

Yeah no problem. When I get home I will post it.

---------- Post added 08-09-12 at 10:12 AM ---------- Previous post was 08-08-12 at 01:06 PM ----------

I stripped it down to just the target around the Moon. It was put into an orbit so that is passes over Brighton Beach. The mission was to launch from Earth, rendezvous with the Shuttle-A, transfer two crew members into it, then land both ships at Brighton Beach.

Flight was flown with an XR-2, modified to be less powerful, requiring a launch vehicle to get off Earth.

BEGIN_DESC
Shuttle A in orbit around the Moon.
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 61258.6632358026
END_ENVIRONMENT

BEGIN_FOCUS
  Ship SA-1
END_FOCUS

BEGIN_CAMERA
  TARGET SA-1
  MODE Cockpit
  FOV 50.19
END_CAMERA

BEGIN_PANEL
END_PANEL

BEGIN_SHIPS
SA-1:ShuttleA
  STATUS Orbiting Moon
  RPOS 1091845.35 1281142.01 736245.22
  RVEL -285.991 978.557 -1281.586
  AROT -160.66 36.54 -102.38
  AFCMODE 7
  PRPLEVEL 0:0.857008 1:0.990134
  NAVFREQ 0 0
  XPDR 0
  PODANGLE 3.1416 3.1416
  DOCKSTATE 0 0.0000
  AIRLOCK 0 0.0000
  GEAR 1 1.0000
  PAYLOAD MASS 0.0 0
END
END_SHIPS

 

[flytandem]

OK. So i figured a hohmann transfer to the moon at a time that allowed a Pe sitting at the axis (node) with the ship orbiting the moon would be a good start. Then an orbit insert but with high Ap and single plane change at Ap then usual rendezvous.

I set up a ship on the Earth and flew it into LEO in plane with the moon. The trick was when to leave to arrive with the Pe at a node.

I first placed myself in the shuttle around the moon and made a TransX plan for return to Earth with just negative prograde and no plane change or inward. I adjusted eject orientation and date of plan to find where the shuttle is already in plane with the plan. I figured if I could leave the moon at that time from that orbit and fall to Earth in plane with the moon then I should be able to do the reverse. Time knows no direction right? LOL It showed 61265.3

Then I glanced at IMFD Map and saw what the axis of the shuttle is and it appeared that somewhere about 61263 to 61265 give or take a couple days should be a good time to leave or arrive at the moon from the shuttle's orbit.

So I tweaked a maneuver to transfer to the moon and it turned out that I was near the end of a window. I didn't want to wait 14 days so I accepted it as is.

Here's the scenario of the ship ready to eject to the moon. I flew it and found that a MCC a day or two before arriving moon allowed a tiny 15 m/s burn to shift the node directly onto the Pe. After the first orbit insert the high Ap had a single 75 m/s plane change.

BEGIN_DESC
Orbiter saved state at T = 690
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 61258.7718168139
END_ENVIRONMENT

BEGIN_FOCUS
  Ship GL-01
END_FOCUS

BEGIN_CAMERA
  TARGET GL-01
  MODE Cockpit
  FOV 50.19
END_CAMERA

BEGIN_HUD
  TYPE Orbit
  REF AUTO
END_HUD

BEGIN_MFD Left
  TYPE User
  MODE TransX
  Ship  GL-01
  FNumber 2
  Int 0
  Orbit True
  Vector  -540983.296661 494276.573149 6544013.187
  Vector  -7743.73281431 -409.118766793 -598.828496664
  Double  3.98600439969e+014
  Double  61258.727397
  Handle Earth
  Handle NULL
  Handle Moon
Select Target
 0 Moon
Autoplan
0 0
Plan type
0 0
Plan
0 0
Plan
0 0
Plan
0 0
Select Minor
 0 None
Manoeuvre mode
0 1
Base Orbit
0 0
Prograde vel.
 3  3124.23058924
Man. date
 5  61258.8238519
Outward vel.
 0  0
Ch. plane vel.
 6  0
Intercept with
0 0
Orbits to Icept
0 0
Graph projection
0 0
Scale to view
0 0
Advanced
0 0
Finvars
  Finish BaseFunction
  Int 0
  Orbit True
  Vector  -315937521.994 -29468897.1113 -185372582.952
  Vector  753.507674961 71.4192780185 456.412786902
  Double  4.90279493298e+012
  Double  61258.5023002
  Handle Moon
  Handle NULL
  Handle SA-1
Select Target
 0 SA-1
Autoplan
0 0
Plan type
0 1
Plan
0 0
Plan
0 -1
Plan
0 0
Select Minor
 0 None
Manoeuvre mode
0 0
Base Orbit
0 0
Prograde vel.
 0  0
Man. date
 0  61258.7718155
Outward vel.
 0  0
Ch. plane vel.
 0  0
Intercept with
0 0
Orbits to Icept
0 0
Graph projection
0 0
Scale to view
0 0
Advanced
0 0
Finvars
  Finish BaseFunction
END_MFD

BEGIN_MFD Right
  TYPE User
  MODE TransX
END_MFD

BEGIN_SHIPS
GL-01:DeltaGlider
  STATUS Orbiting Earth
  RPOS 6535763.12 255134.58 -630313.94
  RVEL 723.931 647.751 7733.256
  AROT 6.19 -1.33 -3.70
  VROT 0.00 0.07 0.00
  RCSMODE 2
  AFCMODE 7
  PRPLEVEL 0:0.579274 1:0.989132
  NAVFREQ 402 94 0 0
  XPDR 0
  TRIM 1.000000
  AAP 0:0 0:0 0:0
END
SA-1:ShuttleA
  STATUS Orbiting Moon
  RPOS -756214.65 457531.33 -1624128.83
  RVEL -759.919 -1437.609 -60.095
  AROT -132.76 38.02 94.70
  AFCMODE 7
  PRPLEVEL 0:0.857008 1:0.989253
  NAVFREQ 0 0
  XPDR 0
  PODANGLE 3.1416 3.1416
  DOCKSTATE 0 0.0000
  AIRLOCK 0 0.0000
  GEAR 1 1.0000
  PAYLOAD MASS 0.0 0
END
END_SHIPS

BEGIN_VistaBoost
END

 

[Gerdih]

Tried and done it from a default orbit when you create a vessel witht the scenario editor to Luna-OB1 all with IMFD exept the docking.

I've used a delta glider
First I've done a target intercept with target plane, target = moon.
Second I've used the planet approach to set the arrival to an orbit of 85º of inc. the inclination of Luna-OB1 varied while the travel so many little corrections have been done.
Third when arriving to the moon -> target intercept tgt = Luna-OB1 with target plane. when I arrived to the node I eliminated the program and I set a delta velocity one to do the orbit insertion while correcting some inclination.
After the orbit insert I was 200 kilometers away from Luna-OB1 in a same orbit but with an error of 3º of inc.

Then I've used great Lola and I've docked in less than an hour (orbiter time). Propellant used = 4.57k

---------- Post added 08-18-12 at 01:28 PM ---------- Previous post was 08-17-12 at 07:51 PM ----------

Done it with a Delta Glider at moon orbit with an inclination of 20º equ. and 288.4 of LAN

Using LunarTransferMFD setting the fly-by LAN and Inc. the same as the orbiting delta glider. This way I have obtained better results, orbital insertion with any errors exept that I set it with an inclination of 19 instead of 20 and 286 of LAN due to the difficult of doing a transfer that could give the optimal result. Any midcourse corrections nor plane changes done while travelling to the moon.

After the orbital insertion used Lola to dock, this one have been longer than the travel in the other post.

Propellant used 3.28k