700 ton landing on Eve!

[Zosma Procyon]

After over a week of tinkering, and 4 days of testing in the sandbox, I finally got my 700 ton behemoth for returning Kerbals to Eve orbit safely down to the planet's surface, and almost back to orbit. Unfortunately I was about 300 m/s short, and the craft reentered the atmosphere, burned up, and the crew capsule splashed down. I'm going to add some more boosters, fuel, parachutes, and landing legs, but I think I've proven the concept works. Here are some highlight pictures.

This is after atmospheric insertion, with the drogue chutes partially open. Sorry for how dark it is, my target landing site in the Eve Highlands was on the night side.

And here the forward heat shield array, really only there to keep it from going end over end, has been jettisoned and the main chutes deployed. I don't actually know how many chutes I added, certainly more than 80. Still seems to need more.

Here the chutes are fully open.

Those heat shields feel uncomfortably close to the rocket.

The dark made it hard to see how high the rocket still was. But some of those heat shields made it to the ground, and provided a reference,

Touch Down! No explosions! Those come later.

Fast forward to daybreak.

Jettison the parachutes as they are no longer needed. I turned on the unbreakable joints and no crash damage cheats to stop this act of housecleaning from ruining this test.

Liftoff!

First drop tank depleted and jettisoned.

External booster bank depleted and jettisoned.

Good old Skippers.

If it had enough delta-v, this would be put into a low orbit and eventually rendezvous with a longer range craft to take the Kerbals home. But it didn't have enough delta-v.

Not bad for my first takeoff from Eve.

In summary I need more delta-v, parachutes, and maybe legs.

[Blaarkies]

Why don't you use the 3.75m parts? It will lead to less part count/complexity, and less atmospheric drag.

Anyway if this design works, it works  
To optimize, you can shed any unnecessary mass (like the monopropellent in the capsule...or even not use a capsule at all). Look at each stage's ratio of fuel to payload, maybe you can squeeze out a bit of extra dv that way

[Foxster]

3 hours ago, Zosma Procyon said:

In summary I need more delta-v, parachutes, and maybe legs.

I'd disagree - unless your aim is to make the biggest Eve lander you can. 

The exact opposite would do a better job - figuring out  how to remove stuff from that behemoth could remove up to 90% of the mass. A good start would be the elimination of all struts, which are a cause of huge drag on Eve - I've had the addition of just a single strut stop an Eve lander from making orbit. Then ditch all the extra junk , such as batteries, chutes, etc. Finally slimming the thing down so that you only use mk1-sized parts, because drag is biggest enemy on Eve. 

[Cpt Kerbalkrunch]

9 hours ago, Zosma Procyon said:

After over a week of tinkering, and 4 days of testing in the sandbox, I finally got my 700 ton behemoth for returning Kerbals to Eve orbit safely down to the planet's surface, and almost back to orbit. Unfortunately I was about 300 m/s short, and the craft reentered the atmosphere, burned up, and the crew capsule splashed down. I'm going to add some more boosters, fuel, parachutes, and landing legs, but I think I've proven the concept works. Here are some highlight pictures.

 

I'm pretty sure the concept of large Eve landers was proven long ago; though I couldn't say who was first or how many have done it. My own weighs 500 tons and gets back to orbit easily. It's fun to figure these things out on your own, so I'll make just a few suggestions if you're interested.

One: go into your settings menu and turn up your ambient lighting. Half your screenshots are kinda useless.

Two: if you're looking for suggestions of any kind, have your resource window open during screenshots and try to include as much info onscreen as you can.

Three: if you're going to make such a large Eve ascent vehicle, make it powerful. I would ditch the Skippers.

Four: You do realize that, unless this is for a challenge or just a personal goal, that you don't need to make an unpowered landing, right? At 500 tons, my lander only uses 15 chutes. You simply tap the gas just before touchdown for a (hopefully) gentle landing. I try to get under 6m/s.

Anyway, hope some of this might help. If you want to make this work, you can. Plenty of people will tell you to just make it smaller, but I know how much fun it is to get such a huge ship back to orbit. And it's tremendously satisfying when you finally make it work. And work is the operative word. If you keep at it, you'll be successful. Just takes a lot of testing, and quite a bit of patience. Good luck, and hope all goes well.

[Human Person]

A problem many people have with EVE is not a lack of delta v, but a lack of thrust and therefore a long and inefficient ascent through the atmosphere. it's not just drag that costs you a lot, It's also fighting against the gravity. Keep in mind that every m/s of delta v spent in the vertical direction is lost, so you don't want to take forever to get "up", you want to get up fast so you can invest more of your delta v in horizontal velocity.

 

Edited January 10, 2018 by Physics Student

[purpleivan]

My big Eve lander was a bit on the portly side at 1,211 tons.

It was designed around the philosphy of beating gravity into submission with lots of thrust, while studiously ignoring the atmosphere that it tore through on its way to orbit.

But this was made back in the pre 1.0 days, when aerodynamics was not a real issue on Eve, which is good as it was about as slippery as a brick wrapped in sandpaper.

[wumpus]

2 hours ago, Physics Student said:

A problem many people have with EVE is not a lack of delta v, but a lack of thrust and therefore a long and inefficient ascent through the atmosphere. it's not just drag that costs you a lot, It's also fighting against the gravity. Keep in mind that every m/s of delta v spent in the vertical direction is lost, so you don't want to take forever to get "up", you want to get up fast so you can invest more of your delta v in horizontal velocity.

I know I've seen a Scott Manley video where he drives up a mountain with the return vessel.  I'd hate to think how many hours that took.  I'd much rather bring a large rocket than do a long drive in KSP.

[Snark]

Moving this excellent mission report to Mission Reports. 

[AngrybobH]

Eve is a huge technical challenge. I'm finding this out with my second ever eve return vehicle. It's much smaller than 700t but it's still giving me fits. I fall into the "just push harder" brute force method rather than finesse so MOAR dV and TWR is my answer. My main problem right now is how to get the thing from the KSC launchpad to eve's surface without exploding or summoning the kraken. I've solved the getting back to orbit with just putting more vectors(and some fuel) on it, which is my suggestion for the 700 tonner you are flying. Just push harder.

[Geschosskopf]

9 hours ago, Physics Student said:

A problem many people have with EVE is not a lack of delta v, but a lack of thrust and therefore a long and inefficient ascent through the atmosphere. it's not just drag that costs you a lot, It's also fighting against the gravity. Keep in mind that every m/s of delta v spent in the vertical direction is lost, so you don't want to take forever to get "up", you want to get up fast so you can invest more of your delta v in horizontal velocity.

But how fast is "too fast" at what altitude?  Drag increases with both air density and speed through it.  The more drag you have, the more thrust you need to reach a given speed.  The more thrust you need, the more fuel you burn.  But, as you say, the slower you go, the more fuel you burn fighting gravity.  At some point, however, those lines cross.  Below the intersection, you're too slow and use more fuel than you need to vs. gravity.  Above that point, you're too fast and burn more fuel than you need to vs. drag.

[KerikBalm]

This was my old 1 kerbal Eve lander:

All the legs and chutes would detach for ascent

a later version with detachable heat shields:

A later, towable 3 kerbal lander, complete with ladders. Some of the ladders stayed on for part of the ascent:

The docking port did burn up during reentry:

And the stages:

Spoiler

Ascent configuration, I modified this slightly by adding aerospike engines under the side drop tanks:

Drop tanks jettisoned, with fuel flow priority, these fuel lines aren't needed anymore (it is an older design). Also I would use autostrutting instead of those external struts if I was doing it over again.

Core stage:

Final stage:

I forget how much it massed, but it was far less than 700 tons, and it could take off from sea level