Problem on Designing a Lander Craft

[SonicControlre]

I wanted to build an Eve Lander capable on returning to orbit on its own. But the Mainsails on the bottom of the first ascent stage is too tall for my landing legs. I'm still bad at designing structural parts of my crafts, and would appreciate any help given.

 

 

 

P.S.: I'm new to the forum so I don't know many features of it. Will try to upload an picture of it when I know how to. (And perfecting the lander?)

[Dafni]

My first advice would be replacing the Mainsails with Aerospikes, as the are much smaller and should offer better performance too. But I never did a Eve return mission myself yet. Somebody with more experience will jump in, as I believe landing leg clearance will not be your only problem you'll have on the way back up from Eve surface.

 

Good luck!

 

And welcome to the forum!

Edited December 4, 2015 by Dafni

[GoSlash27]

41 minutes ago, SonicControlre said:

I wanted to build an Eve Lander capable on returning to orbit on its own. But the Mainsails on the bottom of the first ascent stage is too tall for my landing legs. I'm still bad at designing structural parts of my crafts, and would appreciate any help given.

 

 

 

P.S.: I'm new to the forum so I don't know many features of it. Will try to upload an picture of it when I know how to. (And perfecting the lander?)

SonicControlre,

As Dafne said, the bigger problem is that the Mainsail won't work on Eve, so you don't want to use it. Happily, that eliminates the problem with the lander legs

The Aerospike, Mammoth, and Vector are all good engines for Eve's brutal atmosphere. I think you'll find that anything that you can get back to orbit is going to be huge, so landing legs won't be part of the design.

 Best,

-Slashy

[RocketPropelledGiraffe]

I second the advice to think about Aerospikes and Vectors for the ascend. You want your final return stage as small and light as possible, especially for your first try you should work around the possible minimum - if you feel you require Mainsails you are propably trying to bring back too much stuff, so check if you cannot make it lighter.

For the landing leg design you can always work around with octagonal struts and radial decouplers - attach the radial decoupler where your legs are now, and connect down from there with struts and finally attach the legs to the struts. You can get as far down as you want and can also decopule the legs at launch so you don't have to carry the extra mass. As a side note, additionally to tweaking the legs make sure that your ladders reach all the way to the bottom, otherwise your EVA Kerbals will not get back into the lander...

That's really all there is to tell until we see some images to give more specific advice.

Edited December 4, 2015 by RocketPropelledGiraffe

[Snark]

A few things to bear in mind about an Eve return lander:

First, it's going to be big.  Really big, much bigger than any other lander you're used to.  So you're going to run into structural problems that you're not used to encountering.  For example, if you have radial tanks attached to your central stack (which seems likely, since you need to both pack enough dV to get back to orbit, and be squat enough that you don't tip over on landing), it's pretty easy for them to actually snap off when you land, causing your ship to tumble apart like a pile of jackstraws.  This can happen even if you land at only 4-5 m/s.  Or let's say you've got a Mammoth under you and you come down and land on that (no legs), since it has a nice high impact tolerance-- if you're not landing on a perfectly flat surface, your ship could actually slide off the engine and snap it off sideways.  So be prepared to put more struts on your craft than you're used to.

Parachutes are your friend.  They work really, really well on Eve, and you don't need to mess with drogues.  However, if you've got an enormous massive lander and it's falling fast and you pop the chutes all at once, the gee-forces have the potential to snap off bits of your ship, depending on how you have your design arranged.  You can work around this by tweaking your chutes so that they activate at slightly different heights above ground level, so they don't all go off at once.  (I like to attach my chutes to radial decouplers, so that I can pop 'em off after landing-- no point in lugging all that parachute mass back into orbit.  You can fit three of the radial chutes onto a single radial decoupler, if you mount 'em sideways.)

If you have a ship that's prone to self-disassembly on touchdown, consider using a brief burst of retro-thrust to slow just before impact.  A ship that falls apart when it hits ground at 5 m/s may do just fine at 3 m/s.

Be aware that the atmosphere on Eve is a real killer, the atmosphere losses on takeoff are huge.  Those first 10 km of altitude will eat up a stupidly large amount of your dV.  So if you have a ship that's borderline in terms of being able to get back to orbit, consider landing somewhere at higher elevation, rather than at sea level.  Taking off from 5000m instead of 0m makes a big difference.

Note that solar panels have much reduced output from Eve's surface; the atmosphere blocks a lot of sunlight. So make sure that you have enough electrical supply and/or storage.  If you're planning a mining operation (which needs lots of electrical power), fuel cells can come in really handy.

Eve isn't especially mountainous, but it's quite hilly and there's a high likelihood that you'll come down on a mild slope.  Perfectly flat landing sites are scarce, and Eve's high gravity makes even a mild slope a significantly bigger deal than it would be on Kerbin.  So be sure that you design your craft so that it can handle landing on a bit of a slope.  Tipping over is one concern, of course, but another big one has to do with having big huge landers:  if you land on a slope, the chance of encountering structural problems (such as sliding sideways off your engines and snapping them) gets bigger.  Bear in mind that the uphill side of your ship will hit the ground slightly before the downhill side, and will therefore take the brunt of the landing shock.

(Apropos of this, my most comical Eve mission failure:  I designed a ship that used the long skinny girders as landing gear, since they have a really high impact tolerance.  Needed to put two girders end-to-end so they'd be long enough to reach the ground past my Mammoths.  There were a dozen of these girder-legs around the rim of my lander, rotated slightly outward so that it had a "splayed" stance.  So I landed on a mild slope, touched down without a problem, settled down onto the slope.  Thought I was home free.  Then the weight of the ship came down on the downhill leg, bending it at the knee joint between the two girders.  It slowly bent... and bent... until the "foot" popped loose and the leg snapped straight and lifted the foot off the ground.  Which put the weight of the ship on the next legs, which did the same thing, bend, bend, pop.  Repeat this process, in agonizingly slow but gradually accelerating motion.  Pretty soon the entire ship is scuttling downhill like some sort of deranged three-hundred-ton space crab. Funniest thing I've ever seen in KSP.  Nothing I can do about it.  It keeps galloping down the hill for about two kilometers (really needed some music to accompany it, I'm thinking the Yakety Sax theme song from Benny Hill, or maybe something with banjos) until the slope finally levels out and the lander eases to a stop.  Unharmed, except for snapping off one of its twelve legs at the end of the run.  Which turns out to be the leg to which I had mounted all my ladder rungs, leaving my kerbalnaut stranded in his command pod with no way to get down to the surface to take a sample or plant a flag.  Oh well.)

Edited December 4, 2015 by Snark

[fourfa]

The Mainsail really isn't out of the question on Eve, even down to sea level.  Isp is poor below 5km, but its thrust and TWR are pretty good.

 

But a combination of Vector and Aerospikes is better, most likely narrower and lower-drag, and should be overall smaller and more efficient. Not to mention a lot easier to design landing gear around.

You might consider editing your thread title, since designing a lander craft for Eve is quite different than anything else in Kerbal.

[SonicControlre]

Ok; I just found out that there are questions and topics. Quite the silly me.

I appreciate the help given, by your guys. I'm currently working on decreasing the weight of my return lander, which is taking a lot of time.

Here is the link to the new topic forum: Help on a Eve Return Lander design

PS: Cookies for all of you.

PPS: I feel stupid answering my own question. Logic.

Edited December 4, 2015 by SonicControlre
Forgot PPS

[juanml82]

If you choose the Mammoth, it has a 20 m/s impact resistance, so with a little care, you might forget about landing legs and land directly on the engine