the reusable Eve lander

[Basilo1146]

I have never even attempted to make one, but I have accepted Iong ago that an Eve SSTO is, for all intents and purposes, impossible. However, upon seeing this post:

http://forum.kerbalspaceprogram.com/threads/89300-I-may-have-made-a-terrible-mistake

I had an idea. What if, instead of storing dV in stages that are discarded on the way up, we have a lander that can reach a suborbital trajectory that leaves the atmosphere and, once there, rendezvous with a tug of some sort that completes the rest of the orbital insertion. I haven't had the time to test this yet, and I doubt I have the skills, so if someone who is far better at this game than I would be willing to try this out, I would be very interested to see what happens.

Also, it's one in the morning so I think my ability to use grammar and form proper sentences has left me.

Edited August 7, 2014 by Basilo1146

[Maxwell Fern]

You'll have a similar problem since the tug would either be going way to fast for your lander, or would need to pack thousands of Delta-V to slow down to your suborbital trajectory, dock, and push everything back to an orbit.

I'm not even mentioning how complicated it would be to synchronize both ships to rendez-vous.

[Richy teh space man]

A stock Eve SSTO is probably impossible, however, using the balloons from Hooligans airship mod along with aerospikes it may just about be possible.

As for rendezvousing Maxwell is right, the orbital speeds required will mean there's a big difference in relative velocities.

[Basilo1146]

Yes, however, in that thread I linked, you will notice that they slowed down the tug to the same speed as the lander to allow rendezvous. Obviously, it is on a much smaller body, but the idea is the same.

Edited August 7, 2014 by Basilo1146

[Richy teh space man]

Much smaller body, a lot less gravity and therefore lower orbital velocity. I'm not saying it's impossible, but it would be very difficult to pull off.

[Kasuha]

Eve orbital speed at 100 km is over 3000 m/s and your single-staged ship will probably have hard time reaching more than 1000 m/s of orbital velocity so your orbital stage will need some 5000 m/s of dv to perform the maneuver. Apart of that it probably is technically possible, although very hard to do.

The best place to rendezvous would likely be at the apoapsis of the lifter. Orbital part can time its braking maneuver to meet it exactly there, but there are no suitable tools in KSP to allow you doing that reliably - you'd need to guess and have enough thrust to tune the meeting correctly. Then you need to dock really fast and burn back to orbit. Worth a try but I wouldn't probably want to do that oftern.

[EdFred]

Haven't run the numbers, but what would the dV need to be to burn straight up to put the apoapsis inside Gilly's SOI? If you hit Gilly's SOI while Gilly is at AP, you only need ~300dV (assuming you zero out your Eve orbital velocity) at capture to stay in Gilly's SOI.(~1000 at PE) Is that going to be less than the ~12000dV needed to end up in LEO?

Edited August 7, 2014 by EdFred

[Kasuha]

Haven't run the numbers, but what would the dV need to be to burn straight up to put the apoapsis inside Gilly's SOI? If you hit Gilly's SOI while Gilly is at AP, you only need ~300dV (assuming you zero out your Eve orbital velocity) at capture to stay in Gilly's SOI.(~1000 at PE) Is that going to be less than the ~12000dV needed to end up in LEO?

It is less spent dv if you get to orbit and then raise your apoapsis to Gilly than if you burn straight up from surface.

[Grover]

It is less spent dv if you get to orbit and then raise your apoapsis to Gilly than if you burn straight up from surface.

Not necessarily, since attaining an orbit will require energy spent to gain tangentenial velocity, which in the 'burn straight up' case, is not needed since all the tangentenial velocity is provided by Gilly for free (except the orbital insertion)

The amount of energy in a craft that is at an elliptic orbit is greater than thr energy of a craft at the same altitude, with the same apoapsis but on a sub-orbital velocity

[merendel]

Not necessarily, since attaining an orbit will require energy spent to gain tangentenial velocity, which in the 'burn straight up' case, is not needed since all the tangentenial velocity is provided by Gilly for free (except the orbital insertion)

The amount of energy in a craft that is at an elliptic orbit is greater than thr energy of a craft at the same altitude, with the same apoapsis but on a sub-orbital velocity

you wont be geting much free energy from gilly. it has such negligable gravity that your not going to get an apreciable gravity assist. While its true that you only need a few dV once your up that high to make sure you dont hit eve's atmosphere you spent a ton of dV just fighting gravity the whole way up there. The advantage of tangential velocity vs strait up is that gravity is not counteracting your thrust. the trick about orbits is literaly go fast enough that dispite falling you miss the ground.

[Kasuha]

Not necessarily, since attaining an orbit will require energy spent to gain tangentenial velocity, which in the 'burn straight up' case, is not needed since all the tangentenial velocity is provided by Gilly for free (except the orbital insertion)

The amount of energy in a craft that is at an elliptic orbit is greater than thr energy of a craft at the same altitude, with the same apoapsis but on a sub-orbital velocity

I don't know if your 'tangential velocity' has any practical meaning. An orbit is defined by two factors - ship energy (kinetic + potential) and eccentricity. To land on Gilly, you need to gain very specific energy and eccentricity, both of which correspond to Gilly's orbit. And to spend least fuel on giving your ship that energy, you need to use all available tricks of orbital mechanics - such as Oberth effect or the knowledge that change of an orbital parameter is best done from the opposite side of the orbit.

If you burn straight up, you're raising your apoapsis from a place which is way away from periapsis. That means you lose on Oberth effect because your ship is flying slowly and gravity is slowing it down further and that reduces the kinetic energy gain (Oberth effect) from your fuel. If you circularize first, not only you have lifted your periapsis from apoapsis with relative little energy lost on maneuver inefficiencies, but you can then continue lifting your apoapsis towards Gilly from the best place to do such maneuver - from periapsis. All of the energy your ship has when it is in orbit is conserved and you only add to it to lift it towards Gilly.

[EdFred]

Just for esses and gees last night, I took my Eve craft and tested. I obtained a 105km x 105km orbit, and had just under 1000dV remaining, which depending where Gilly is, might be enough to get an encounter. Gilly's PE=14,175,000m

By burning straight up with the exact same craft, I could only obtain a AP above Eve of just over 1,100,000m - and that wasn't even an orbit. Well, it was, with an eccentricity near 1, which means it's coming straight back down.

[MarvinKitFox]

Haven't run the numbers, but what would the dV need to be to burn straight up to put the apoapsis inside Gilly's SOI? If you hit Gilly's SOI while Gilly is at AP, you only need ~300dV (assuming you zero out your Eve orbital velocity) at capture to stay in Gilly's SOI.(~1000 at PE) Is that going to be less than the ~12000dV needed to end up in LEO?

powering straight up, to virtually infinite altitude (gilly is a good approximation of that)...

Take orbital velocity. Multiply by 1.4142135 (root 2).

Your delta-v will be this figure, plus air drag losses, plus gravity losses because your burn is not instantaneous.

i.e.

You need about 1350m/s MORE than going to orbit, plus whatever increased gravity loss you have due to burning straight up.

[EdFred]

See my last post

[metaphor]

It's certainly possible to do a suborbital rendezvous on Eve.

http://imgur.com/a/N18lK#25

From experience, I would say getting a higher apoapsis on the ascending vehicle and intercepting near the first time it gets above the atmosphere is better. Then you have more time to do your orbital maneuver (~3000 m/s of delta-v to slow down, 3000 to speed up again).

You'll still need about 6000 m/s of delta-v in a single stage to get above Eve's atmosphere from its highest point.

[magnemoe]

A stock Eve SSTO is probably impossible, however, using the balloons from Hooligans airship mod along with aerospikes it may just about be possible.

As for rendezvousing Maxwell is right, the orbital speeds required will mean there's a big difference in relative velocities.

Someone was able to make an Eve balloon SSTO, it was giantic, you will not use aerospikes as you are out of the atmosphere then you start them so you want an high ISP and TWR vacuum engine.

[Richy teh space man]

Someone was able to make an Eve balloon SSTO, it was giantic, you will not use aerospikes as you are out of the atmosphere then you start them so you want an high ISP and TWR vacuum engine.

That was probably the last one I made. I've since made a new one that is compatible with the current version of KSP, and just about works.

Edit: I'll upload the craft file at some point, just a bit busy atm

Edited August 11, 2014 by Richy teh space man