Eve Precision Landings

[Hagen von Tronje]

I recently shipped a few toys to Eve for my "colonists" (they are totally not stranded, they live there now ). I'd only landed on Eve once before, and it was a wild ride. Learning from that mistake, I simply sent additional aerobraking measures, to ensure I don't burn up on entry.

That worked fine, no problem there. But the issue I'm finding is that it's really quite difficult to land with precision. On a non-atmospheric body, precision landing is as easy as bringing your trajectory down low over the target, killing horizontal speed, then proceeding with a standard issue landing like you would any other day of the week. Duna's atmosphere doesn't seem to be much impediment to anything, and on Kerbin you really only care so much - after all, if you land 20km from KSC rather than 2km, who truly cares (unless it's a landing challenge, but that's on you).

Obviously that method isn't so great on Eve, since LEO is 3000m/s+, way more dV than I think most would like to spend, and you "aim" from 90km+. Aerobraking makes it difficult to aim, since the change in trajectory will be in largely outside your control. After are dozen or two attempts, I got within a few km of the landing zone, which is fine since I have ground vehicles; I got a little feel for it (else I would never have landed where I wanted), but it felt too much like luck.

Is there some secret to this? I found an old (2013) aerobrake landing chart giving Pe values to place over landing sites, but I have no reason to think the old values still apply. I've tossed around the idea of a "cargo plane" delivery system that could fly/glide to the destination after deorbiting, and while that sounds cool to make, it strikes me that there are some obvious payload limits and launching difficulties with such a craft.

Anyone mastered this and want to share?

Edited September 7, 2015 by Hagen von Tronje

[Kobymaru]

Yes, there's a secret and it's a mod called Trajectories:

It shows you the exact landing position, depending on your crafts AoA. Try landing with this one.

It has a few gotchas though:

- I think stock wings work

- Aerobrakes don't work

- The trajectory is plotted for the AoA in the settings (usually 0°) and not the current AoA

- It obviously can't know about staging events and deploying parachutes is not considered either.

Taking all that into account, I did succeed with a precision eve landing with this Mod. (Ok, precision might not be a 100% true, but I landend on the plane that I aimed for)

[Zephram Kerman]

You can get some control of trajectory by adding a little bit of lift. It doesn't need to be a space plane, but using a lifting body or fins will help you control your rate of descent. If you're coming up short, pull it up to get less drag. Going long? Pitch it down and hang on!

[purpletarget]

Old braking charts defintely won't work in 1.0 or later as the Aerodynamics was overhauled. As already said, lifting bodies and Airbrakes will give you a bit of control during a descent. It may take some trial an error though for now. There's some math, and I expect a new version of the charts will make the rounds eventually, but even that will be tricky since air drag has far more complex factors in the density and temp profile of planetary atmo's, and there's huge variability now based on your spaceship design...one one chart fits all solutions are probably going to be harder to come by.

[Hagen von Tronje]

Old braking charts defintely won't work in 1.0 or later as the Aerodynamics was overhauled. As already said, lifting bodies and Airbrakes will give you a bit of control during a descent. It may take some trial an error though for now. There's some math, and I expect a new version of the charts will make the rounds eventually, but even that will be tricky since air drag has far more complex factors in the density and temp profile of planetary atmo's, and there's huge variability now based on your spaceship design...one one chart fits all solutions are probably going to be harder to come by.

I suspected this might be the case. Guess this gives me some impetus to develop semi-glider Eve delivery systems!

[technion]

I spent hours basically doing this:

* Quicksave

* 900m/s deceleration burn

* Observe results

* Quickload

* 930m/s deceleration

* Repeat

[xebx]

I've been using mechjeb landing prediction and same small deceleration burn method from 100km orbit (at the opposite of the landing site), after a few tries i know where i should aim.

But Eve is big, precise landing or setting rendezvous for two crafts (for ex a science rover and a mainlander/reorbiter) is not easy, tests, patience and tools can help.

[Larsak]

I totally did not make your colonists explode....Mwehehehe...