Flight Question Mars arrival planning

Marijn

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To plan my flights to Mars, I am using IMFD. This MFD requires a depart and an arrival date to provide a solution for the interplanetart transfer. To minimize fuel consumption, I am doing direct reentries without entering a parking orbit.

Sometimes, the periapsis happens to be close to Olympus base. Then I need to do a very aggresive aerobrake. More often, I arrive close to the base without enough anticipation to do a safe aerobrake. Then I have to go all the way around before landing.

I like to have some more control over the arrival situation. Since the arrival MJD can be set, I think I need to set this value in some calculated way so that the periapsis will be a set distance from the base.

But I am not sure how this is done. Any help is appreciated.
 

Thundersnook

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There is an option in IMFD called Base Approach, where you can set the option to direct reentry (or something like that) there you can Input your target Alt, and distance from the Base (And reentry-angle, set this to "0" if you are using your perigee for your calculations)


It gets best results when used in the SOI of the Body you want land on ... but unfortunately sometimes the solution it finds require a lot of fuel or it didn find an solution at all...


I'm curious if someone has a good suggestion for using the direct reentry module more effective :)


I guess you know the wonderful Tutorial of IMFD with Dimitris and David?
They're mentioning the Base-Approach there but I cant remember which Part it was ...



[ame="https://www.youtube.com/watch?v=btiYvWy-QeM"]Orbiter 2010 - [Part 1] IMFD Training with Dimitris - Earth to Moon - YouTube[/ame]
 

Marijn

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Hi Thunder,

I know the BaseApproach program. Indeed, you can set an anticipation angle in re-entry mode.

The problem seems to me, that when you are closing in on Mars anywhere near it's SOI, that you're already much to close to Mars to modify the trajectory in such a way that the prefered anticipation can be realized with subtle corrections to the trajectory. It will cost a whole lot of delta-v to seriously change the trajectory and solve the problem at that very late point in time. So it seems the BaseApproach program does it's job, but some more planning has to be done upfront for better results (less delta-v).

Let's say the PeA of a certain trajectory happens to be right over the base. That means you have to go all the way around. Mars rotates in 24 hours. So if we would aim for an anticipation of 180 degrees, it would have been better to arrive 12 hours earlier or later. Then, we only need to go around half an orbit. Right?

So if we would have departed from earth 12 hours earlier or later, we would arrive with an anticipation of 180 degrees. We could also depart at the same time, but then with a slightly shorter or longer total transfer duration to arrive 12 hours earlier or later.

This is how I envision the problem. Not sure if it's correct though. I have to experiment with it.

I guess you know the wonderful Tutorial of IMFD with Dimitris and David?
Yes, I've studies all of their videos in detail. Very helpful to get started with interplanetary transfers. I am not sure whether the 'Map Method' which they demonstrate is only solution to this problem. It's a bit tedious. The charm of IMFD's course program is that you need only two numbers and I think the problem can be mostly solved by changing these numbers a bit.
 

Thundersnook

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Yup, these are also exactly my thoughts and experiences on this topic too...
So I hope, that someone has a neat solution for this.

I'm no big fan of flying a mission to get the data to fly it properly again after that, so I hope there is a neat solution for this :thumbup:
 
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