Return from Eve

[Khrissetti]

I have 3 Kerbals rolling around the coastline of Eve in a 3-man rover and now I'm getting transmissions to say that after a year on the Iodine gem they would quite like to come home. My plan is to put a craft on the surface to lift them up to orbit to transfer to a return craft.

The question is, what does a successful Eve-to-space lander look like? What sort of performance should I look for on Kerbin to prepare me for an Evian mission?

[Temstar]

I believe you need to be able to put out around 12,000m/s delta-v after lift off if you launch from sea level.

[bsalis]

The question is, what does a successful Eve-to-space lander look like?

I'm thinking your video card would like to know the answer as well. It will need all the help it can get.

[Ziff]

Well, it's easily more than twice the size of a rocket to get into Kerbin orbit. One trick to use that can use to save you about 2-4k delta-v is to land on high ground on eve. The taller mountains are around 9-11km in height.

[Qumefox]

Probably the only realistic way to get off Eve without resorting to cheater parts or other shenanigans is a hybrid plane/rocket. Fly the return craft as high in the atmo as possible, then shed the plane parts/atmo engines/mass and burn the rest of the way to orbit conventionally.

It's still going to be a rather large craft any way you go about it though.

[SLAMS]

Has anyone actually accomplished this?

[Qumefox]

Not that i'm aware of.. Not without it involving shenanigans anyway.

[trollmylove]

Not that i'm aware of.. Not without it involving shenanigans anyway.

i saw someone who made a craft capable of getting off eve into orbit but he just cheated it there. i'd like someone to take that design and do it legit.

[RoboRay]

You can build a craft capable of departing Eve... it's getting it from KSC to the surface of Eve that is problematic.

[olex]

I don't remember who it was, but someone on IRC made a ship capable of landing on Eve from Kerbin and then achieving stable orbit again, however not returning to Kerbin under own power. It used asparagus staging with aerospikes on outer stages and a single gimballed rocket in the center, and the initial launch vehicle was positively enormous.

[Temstar]

I'm planning an Apollo style Eve landing mission using all stock parts + the two docking mods. The interplanetary carrier is done (9,600L capacity, 7 nuke engines) and the test lander for a Duna + Ike landing is nearly ready too. If all goes well the Duna test mission will be carried out sometime late this week and results will be posted next week.

Assuming docking and everything else work I should be able to delivery a "big" lander to and from Eve. The only Eve lander I've seen though is one LV-T45 with 12 asparagus staging aerospikes with a total fuel load of 20,800L at full capacity. A lander of this size is probably too unwieldy even for the carrier I've got. A return mission may still be possible but will probably require tanker rocket(s) to arrive from Kerbin to refuel the lander and mothership waiting in LEO before a landing and return trip could be attempted.

[Ziff]

You can build a craft capable of departing Eve... it's getting it from KSC to the surface of Eve that is problematic.

The hard part is building a launch vessel capable of getting your Eve return vehicle to the planet. Not actually getting there. Also , you must be rather precise with your landing as well because you will want to land on the tallest mountain you can in order to shave as much delta-v as possible off the return trip. I can get my lander into orbit and back to Kerbin from a tall mountain, but not from the average surface height.

I don't remember who it was, but someone on IRC made a ship capable of landing on Eve from Kerbin and then achieving stable orbit again, however not returning to Kerbin under own power. It used asparagus staging with aerospikes on outer stages and a single gimballed rocket in the center, and the initial launch vehicle was positively enormous.

You pretty much have to use asparagus staging and aerospikes, there really is no other efficient way to do it.

[RoboRay]

The hard part is building a launch vessel capable of getting your Eve return vehicle to the planet.

Yeah, that's what I said. "From KSC" references the launch.

[JeanHavoc]

This thread is of some interest to me as I've selected Eve as a primary target of interest once I get through with Kerbin space. I see a lot of stuff dealing with landing there and the various issues with coming back home but I'm of a slightly different mind and I'm wondering if there's any good information regarding potentially flying by Eve and then returning to Kerbin rather than simply going into orbit. Moreover, I'm wondering if it might be possible to replicate what Mariner 10 did in the real world by flying past Eve on the way to Moho. I might, of course, be asking far too much of KSP - but I am curious as to what's possible here.

[swiftgates24]

Well it looks like a super-computer...well at least for me. As long as you can get into space and do the rest you should be fine. And you might have a problem...it's a 3 man lander right? How are you going to rescue 3 in one trip? You can have one on a ladder but you can only warp 1x. Trust me YOU DO NOT want to do a Eve-KSC miission in real time.

[Qumefox]

You can have one on a ladder but you can only warp 1x. Trust me YOU DO NOT want to do a Eve-KSC miission in real time.

Better hope the power doesn't go out... for a few years.

[Khrissetti]

Well it looks like a super-computer...well at least for me. As long as you can get into space and do the rest you should be fine. And you might have a problem...it's a 3 man lander right? How are you going to rescue 3 in one trip? You can have one on a ladder but you can only warp 1x. Trust me YOU DO NOT want to do a Eve-KSC miission in real time.

I have the Crew tank mod which can store up to 5 kerbals.

I've temporarily given up on the Adam IV until I can be bothereed. Next stop... Duna!

[SNapple]

More to the point, what sort of lander can escape Jool?

[Temstar]

I did some research:

Take a Boeing 747-400, at maximum take off weight it's 396,890 kg. It's four Pratt & Whitney PW4062 turbofan generates 282 kN of thrust each for a total of 1182kN.

TWR for whole aircraft = 1182 / (396890 * 9.807) = 0.000307

Yet despite such a poor thrust to weight ratio compaired to our rockets (remember, recommended TWR for rockets at take off is around 2, and decreases as you climb) the 747 can take off no problem. How? It generates a lot of lift from those big wings.

A 747 at take off is flying in a 1G environment at 1 atmosphere pressure.

Our Eve spaceplace will be taking off in 1.7G at 5 atmosphere pressure. In that thick of an atmosphere even tiny wings of a winged rocket will be generating tremendous amount of lift. Therefore a rocket with small wings in the shape of an enlarged X-15 should be able to take off and slowly climb in the thick Eve atmosphere with very low level of rocket thrust. As the atmosphere thins out the thrust required to keep it aloft will be increasing as lift decreases, however this is compensated by the fact that the rocket plane is also becoming lighter by burning fuel and jettisoning empty tanks. As a matter of fact if we make it so we keep staging empty tanks we may be able to keep the same set of aerospike engine from lift off all the way to orbit.

[EndlessWaves]

Take a Boeing 747-400, at maximum take off weight it's 396,890 kg. It's four Pratt & Whitney PW4062 turbofan generates 282 kN of thrust each for a total of 1182kN.

TWR for whole aircraft = 1182 / (396890 * 9.807) = 0.000307

KSP weights are in tons so a 747 has a thrust of (1182/397)/9.81 = 0.29, it's perfectly possible to fly a plane with that on Kerbin, the difficulty is getting your ascent speed high enough that it's actually more efficient than sticking on three more engines and burning straight up.

[olex]

Yeah, that calculation is off by a factor of 10³, since kg is a base unit, and kN isn't. After converting everything into base units, we get 1182000 / (396890 * 9.807) = 0.304, which is a perfectly reasonable TWR for a plane. Only some highly maneuverable fighter jets have TWRs of >1, I think the russian SU-27 was one of the first ones capable of accelerating in vertical ascent.

[Temstar]

But the point is, if we use wings to generate lift as we take off from Eve's surface we should be able to get a spacecraft with very low TWR off the ground. If 0.3 TWR is possible on Kerbin/Earth than under 1.7G and 5 atmosphere pressure even lower TWR should be flyable. This very low TWR spacecraft would burn fuel at a very low rate compared to a 2 TWR Eve lander. The catch is this rocket plane would spend much longer to achieve orbit which results in greater gravity drag.

So the equation is:

Pure rocket Eve lander

• low gravity drag since it ascends vertically and quickly reaches orbit
  
• high air drag because it attempts to quickly punch through that very thick lower atmosphere
  

Rocket plane Eve lander

• high gravity drag since it ascends in depressed trajectory and takes much longer to reach orbit
  
• low air drag because it climbs out of the lower atmosphere slowly
  

The question is is the trade off worth it, my gut feeling says yes, seen as Eve's gravity is 70% greater but its sea level atmosphere pressure is 400% greater. To do a quick test I built two rockets attempting to put a small spacecraft into Kerbin orbit, one conventional rocket and one a horizontal take off rocket plane. I tried to make them both as efficient as possible to loft the spacecraft up into 75km orbit and compared the two rocket's weight at take off:

As expected, the pure rocket manages to launch the spacecraft with lower take off weight. But surprisingly the results were pretty close. Given that this test is conducted under 1G and 1 atmosphere pressure I'm seeing this as evidence to support that a smaller winged rocket on Eve would be able to loft the same payload as a larger conventional rocket. Seen as weight is a critical issue in lander design picking the right choice would make an enormous difference in size at take off from KSC.

To fly Pathfinder X-2, do the follow:

1. Throttle to full, stage to light the engine

2. glide on the runway until you reach about 90m/s, pull back on the pitch gently and nose up. Once you start to climb turn on ASAS and stage to jettison the landing gears

3. Nose up to 65 degree (do it while ASAS is on to be safe) and hold it there, let the rocket plane climb

4. Once the fuel in the side stages are gone (should be somewhere about 14,000m) stage to jettison all the spaceplane parts and convert to pure rocket mode

5. Burn to orbit as you would a normal rocket

Edited October 10, 2012 by Temstar

[SNapple]

Air-breathing engines.

Do they work on Eve? I haven't yet been able to play 0.17, so I won't know.

[melaus]

I know of three successful flights to eve and back with stock rockets (except for mechjeb). None of them used space planes though. Images below

http://imgur.com/a/HHPog

http://imgur.com/a/Z8GzJ

http://kerbalspaceprogram.com/forum/showthread.php/23491-EVE_M-(madness)-the-first-cpu-friendly-eve-return-design!-(-howto-fly)

Edited October 10, 2012 by melaus

[Qumefox]

Air-breathing engines.

Do they work on Eve? I haven't yet been able to play 0.17, so I won't know.

No, they don't.

http://kerbalspaceprogram.com/forum/showthread.php/23576-Do-Jets-Work-On-Eve