MontBlanc2012
Active member
- Joined
- Aug 13, 2017
- Messages
- 138
- Reaction score
- 26
- Points
- 28
Here (below) is a simple challenge designed to test your thinking about ways of making transfers from low lunar orbit to the Earth.
The scenario set out in the attached .scn file is as follows: A Delta Glider starts in a 20 x 20 km lunar orbit with a total 700 m/s of main fuel and 10 m/s of RCS. The challenge is to land anywhere on Earth. For the purpose of this exercise, achieving an Earth approach orbit with an Earth-centric periapsis < 70 km altitude constitutes a 'landing'.
Now, at first blush, this sounds simple enough - after all, it is one of the first 'missions' that budding Orbinauts will set themselves. However, Apollo-style Moon-Earth transfers typically require around 1,000 m/s of fuel. But in this challenge, the DeltaGlider starts with just over two-thirds that amount. In fact, the fuel needed to lunar escape from a 20 km parking orbit is 692 m/s - so, you have barely enough fuel to 'escape' from the Moon let alone set up a low perigee encounter.
Finding a Moon-Earth transfer solution that meets the rather restricted fuel constraints of this scenarion requires a little 'out of the box' thinking. As will all problems of this kind, the solution is quite simple once you frame the problem in the rightway; and devilishly hard if you don't. But once you know what you are doing, it's quite easy to set up in Orbiter using standard tools.
As a hint, you may find that TransX is not of much use in finding a solution.
For those that easily manage to find the solution, well done! - and you may wish to pay appropriate hommage to Messrs. Lagrange and Belbruno.
I'm happy to provide a solution upon request.
As for the challenge scenario itself, here it is:
And for those requiring a .scn file, see the attached .zip file.
The scenario set out in the attached .scn file is as follows: A Delta Glider starts in a 20 x 20 km lunar orbit with a total 700 m/s of main fuel and 10 m/s of RCS. The challenge is to land anywhere on Earth. For the purpose of this exercise, achieving an Earth approach orbit with an Earth-centric periapsis < 70 km altitude constitutes a 'landing'.
Now, at first blush, this sounds simple enough - after all, it is one of the first 'missions' that budding Orbinauts will set themselves. However, Apollo-style Moon-Earth transfers typically require around 1,000 m/s of fuel. But in this challenge, the DeltaGlider starts with just over two-thirds that amount. In fact, the fuel needed to lunar escape from a 20 km parking orbit is 692 m/s - so, you have barely enough fuel to 'escape' from the Moon let alone set up a low perigee encounter.
Finding a Moon-Earth transfer solution that meets the rather restricted fuel constraints of this scenarion requires a little 'out of the box' thinking. As will all problems of this kind, the solution is quite simple once you frame the problem in the rightway; and devilishly hard if you don't. But once you know what you are doing, it's quite easy to set up in Orbiter using standard tools.
As a hint, you may find that TransX is not of much use in finding a solution.
For those that easily manage to find the solution, well done! - and you may wish to pay appropriate hommage to Messrs. Lagrange and Belbruno.
I'm happy to provide a solution upon request.
As for the challenge scenario itself, here it is:
Code:
BEGIN_DESC
Delta Glider in a 20 x 20 km lunar orbit with a total 700 m/s of main fuel and RCS. The goal is to land anywhere on Earth. For the purpose of this exercise, achieving an Earth approach orbit with an Earth-centric periapsis < 70 km altitude constitutes a 'landing'.
END_DESC
BEGIN_ENVIRONMENT
System Sol
Date MJD 52006.7542552436
Help CurrentState_img
END_ENVIRONMENT
BEGIN_FOCUS
Ship GL-NT
END_FOCUS
BEGIN_CAMERA
TARGET GL-NT
MODE Cockpit
FOV 40.00
END_CAMERA
BEGIN_SHIPS
GL-NT:DeltaGlider
STATUS Orbiting Moon
RPOS 1677740.022 -137005.718 -506935.076
RVEL 477.7254 -65.8104 1598.8449
AROT 15.788 -10.126 42.772
AFCMODE 7
PRPLEVEL 0:0.015058 1:0.004584
NAVFREQ 0 0 0 0
XPDR 0
HOVERHOLD 0 1 0.0000e+000 0.0000e+000
AAP 0:0 0:0 0:0
END
END_SHIPS
And for those requiring a .scn file, see the attached .zip file.