IMFD Mid-course Corrections.

[pete.dakota]

I'm been flying a lot of AMSO lately. I'm trying to re-create certain missions with as much historic accuracy as possible. Yesterday I did a full Apollo 11 mission with all the major milestones (SIVB Shutdown, transposition and docking, LOS/AOS, lunar landing, splashdown etc...) only around 4 minutes behind the actual GET times from Apollo 11 By The Numebrs.

This was all made possible by using IMFD. It's a great tool. However, I'm not too sure which program I should be using for mid-course corrections. To be historically accurate I need to be able to set three parameters for the lunar encounter: PeA, PeT (GET for encounter in Map) and the angle to my chosen landing site. Simply using the Delta Velocities program causes major headaches, as changing one value changes all three of the encounter values. Which means I have to sit there for ages tweaking to get it all right.

Planet Approach seems like it should work, but gives me conflicting results between it and Map. Say, I would set Planet Approach reference to Moon and then set PeA to 96km, in Map it would say that my PeA will be 2.6M. I'm not sure which to trust.

I can and have been doing the corrections using Delta Velocities, but it is extremely time consuming, and I suspect there is an easier way. Is there?

 

[jarmonik]

Planet Approach seems like it should work, but gives me conflicting results between it and Map. Say, I would set Planet Approach reference to Moon and then set PeA to 96km, in Map it would say that my PeA will be 2.6M. I'm not sure which to trust.

I suppose that the Map is the one to trust. The Planet Approach program, like every other program, is using a conic approximation and it's only accurate when well within the gravity of the reference body. I have a new program under a work that doesn't suffer this kind of problems anymore. However, at a moment we have to deal with the accuracy problems.

Have you tried to follow the "Offset Procedure" when seting up trans lunar mid-course correction. There shoud be something about it in a manual of AMSO and initial offsets are listed in IMFD manual.

 

[pete.dakota]

I suppose that the Map is the one to trust. The Planet Approach program, like every other program, is using a conic approximation and it's only accurate when well within the gravity of the reference body. I have a new program under a work that doesn't suffer this kind of problems anymore. However, at a moment we have to deal with the accuracy problems.

Have you tried to follow the "Offset Procedure" when seting up trans lunar mid-course correction. There shoud be something about it in a manual of AMSO and initial offsets are listed in IMFD manual.

Offsetting is really only effective in the TLI burn set up. Once the burn is done, you are on a rough free return trajectory. I'm essentially looking for a tool within IMFD that allows me to enter the GET of the periapsis, the PeA and a 0.00 degree angle with the landing site. Just like how it can be done in Target Intercept, but for a mid-course correction, not the initial injection burn.

I'll try using Planet Approach and trusting the Map's values.

 

[reverend]

Sounds like a task for BaseApproach in Orbit-Insert mode?

 

[jarmonik]

Just like how it can be done in Target Intercept, but for a mid-course correction, not the initial injection burn.

Have you checked the Apollo11-MCC scenario that is distributed with IMFD 5.1 ?