Flight Question Landings on bodies with negligible atmospheres

[Matrix Aran]

Hi there. I'm trying to find a general set of guidelines for making a deorbit burn and eventualy a powered landing on bodies such as the moon or Mars.

I've been scouring through the search function trying to find posts addressing this, and while there are a great amount of really good tutorials covering landings in a particular vessel, or on a particular world, very often they don't delve into the methods behind the steps. And with different vessels sometimes something that worked perfectly fine for one tutorial ends up painfully difficult in practice.

Now up until now I'm quite capable of landing pretty much anywhere I want more or less by the seat of my pants. But this ends up leading to some unfortunate situations, such as coming in far too fast, or ending far too short of the landing zone. But the student in me says that there's got to be a much more analytical way to solve this problem, or at least a general set of rules of thumb that could help me look at a body, look at my vessel and be able to say: "I need to deorbit now, so fast at such an angle and brake now, keeping such and so speed above such and so a vertical speed." Or something like that.


Afterthought: I know Mars does have an atmosphere that can provide a significant amount of deceleration, however Mars in one particular case where I'd love to know in detail how to slow down when the atmosphere just won't cut it anymore.

 

[Cras]

I would suggest taking a look at DVTools MFD. It has tools and tutorials for landing on the Moon and Mars using instruments and with precision.

 

[Matrix Aran]

Thank you very much for this recommendation. While the procedures to get it to work were a bit confusing at first, this really is a very useful MFD for calculating deorbit burns for Mars and Earth, giving spot on re-entries which really reduce my workload. I've yet to try it with the moon though, and although the author warns of the experimental nature of the airless bodies calculator, it still looks rather solid, and if it can perform even half as well as the atmospheric calculator, it will be perfect for my uses.

Once again thank you for this sterling recommendation.

 

[Cras]

It does require IMFD, Aerobrake, and I think Basesync as well, but I love it.

I have used it on the Moon to great results. It gives you a solution to when to burn right over the base and you then fall down all the way. It is hard at first, and will require some familiarity with the procedure, and with what is expected, but it is a tremendous add-on, a must have in my book.

 

[boogabooga]

You can also try Lola MFD and watch what it does. It is VERY efficient at moon landings. Mars not so much.

 

[Tommy]

I should warn you that landing on Mar's moons is more like "docking" than it is "landing", due to the almost non-existent gravity.

 

[PhantomCruiser]

Yup, Deimos or Phobos "landing" are more like maneuvering in tight formation with a large rock. They do make for some good "fundamental" practices though.

 

[Matrix Aran]

Well for clarity's sake, I was thinking about moons with some consequential gravity (Luna, Europa, Io with something unmanned).

I've experimented with a few Phobos "landings", and I find it harder to not crack the landing gear on the XR2 on Phobos than anywhere else in the solar system, though that's not the particular problem I was interested in solving today.

 

[BruceJohnJennerLawso]

Look up the brighton beach tutorial in Go play in Space. Once youve sat through that, it should be no problem, although I wouldnt try the arrow first time. It can fall very quickly if you arent paying attention :lol:

 

[Matrix Aran]

I've got lunar landings well covered, as its quite easy to comfortable deorbit at a place of your choosing, and it much easier to perform braking burns to slow yourself down.

The problem I was having when I made this post was with bodies like Mars, that have atmospheres just thick enough to cause my ship to be incinerated with a lunar approach, but too thin to slow with just air resistance alone.

As its hard to turn retrograde in these situations, I wanted a way to calculate the time I needed to come to a stop with much better reliability than just guessing half of such and so number and working from there as I had in the past; all in an effort to save as much fuel as possible.

As for the Arrow, it can quite comfortably land itself pretty much anywhere with a beacon, so it's not too much of an issue. The XR5 on the other hand is a much different beast

And as for Phobos... Well I think the proper term should be docking with Phobos if you ask me, but I've cut down on landing gear strut replacements by about 400% in the last few weeks.