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A_name

Eve Spaceplane Entry

Question

I’m currently designing an Eve spaceplane mission. I’m very excited for this mission and so far quite pleased with my craft. The mission profile looks like this:

 

1.      SSTO from Kerbin

2.      Refuel in LKO with fuel tanker (capable of Minmus refuel with ISRU if you’re not lazy like me)

3.      Fly to Eve and land

4.      Refuel on Eve with ISRU

5.      Staged ascent from Eve, with only the cockpit eventually making it back to Kerbin.

 

Anyway, I digress, none of this is too relevant to the question. My issue is that I cannot for the life of me reenter the plane on Eve. I will burn up every time seemingly regardless of my entry profile (shallow vs steep and several in-betweens). Are heat shields a must now? And how to put heat shields on a plane that’s supposed to SSTO from Kerbin without totally ruining the areo? Any help is appreciated.

 

I will say I’ve had lots of fun looking at the firework show each time I’ve blown up the 150-part plane during my tests!

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51 minutes ago, A_name said:

Are heat shields a must now?

Pretty much, unless you can pack some boosters on to slow you a lot slower than orbital speeds before you hit atmosphere.

Orbital velocity at Eve is around 3400ish for a low orbit, which is... ticklish without a heat shield.

51 minutes ago, A_name said:

And how to put heat shields on a plane that’s supposed to SSTO from Kerbin without totally ruining the areo?

My own solution to this problem is "don't use a plane."  :P

Or just give it an additional rocket stage that you fire and discard before entering Eve atmosphere, to slow you down to something manageable.  If your design is that you land with an empty fuel load, perhaps you don't need an extra stage and could just plan on arriving in Eve orbit with a full fuel load, so you could use the fuel to slow down for entry?

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1 hour ago, A_name said:

how to put heat shields on a plane that’s supposed to SSTO from Kerbin without totally ruining the areo? Any help is appreciated.

You could use an inflatable heatshield.

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1 hour ago, A_name said:

Anyway, I digress, none of this is too relevant to the question. My issue is that I cannot for the life of me reenter the plane on Eve. I will burn up every time seemingly regardless of my entry profile (shallow vs steep and several in-betweens). Are heat shields a must now? And how to put heat shields on a plane that’s supposed to SSTO from Kerbin without totally ruining the areo? Any help is appreciated.

Umm, how about sticking a big inflatable heatshield on the back and going in cheeks-end first? You'll probably need a shed-load of deployed airbrakes on the front of the craft to keep it pointed retrograde  during entry. 

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You just need 1000 to 1500 m/s of dV to burn retrograde to slow you down before you start Eve entry. If you're going to be doing Eve ISRU anyway, then you don't need to save any that you reached Eve with. Once you slow down, a planet with thick atmosphere is easier than one like Kerbin. The only reason you could be burning up is if you are trying to reenter with full orbital velocity. Slow down first, and come in with either a maximal drag or maximal lift attitude.

 

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I never wanna say something can't be done (cuz it's a good way to look like an idiot) but, if you're planning what I think you're planning, getting to the surface will be the easy part (which is saying something). The only reason to bring a spaceplane (other than looks or cool factor) is because you intend to take off like a spaceplane. I know you said you'll be staging (which you'll have to), but it still sounds like you'll be taking off horizontally. If this is the case, and you're playing stock, I'm not sure it's going work. It could be problems with my designs, but the only times I've made it back to orbit were because I launched straight up and got out of the soup as quick as possible. Even attempting any kind of gravity turn meant failure. Not only would I not make orbit, I usually couldn't leave the atmosphere at all. I've seen the arguments that spaceplanes should work well on Eve because you'll get great lift with your wings. I think just the opposite is true. It'll knock anything with high drag back to the surface. If a plane took off from sea level horizontally, I would be impressed if it reached 10km. IMO, vertical is the only way.

Apologies, if I've misread your intentions.

As for the descent itself, in my experience, anything not behind a heatshield at 50km will never see 40km. It just blows up.

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51 minutes ago, Cpt Kerbalkrunch said:

I never wanna say something can't be done (cuz it's a good way to look like an idiot) ...

I prefer to think you look like a distinguished but elderly scientist.

Maybe he will try what you think he will try because the challenge. Or maybe the spaceplane part of the mission is just until he lands on Eve.

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3 hours ago, Spricigo said:

Maybe he will try what you think he will try because the challenge. Or maybe the spaceplane part of the mission is just until he lands on Eve.

For the challenge of it, for the fun of it, or just because I want to, are all perfectly acceptable answers in KSP. Any of those would make sense to me. However, if @A_name is really gonna try the spaceplane-type ascent, I'd really like to see a pic. Even if it's just a rough draft, I'd be interested to see how he's gonna try for it.

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8 hours ago, A_name said:

 Are heat shields a must now? 

I don't think they are absolutely required, if you first slow to low Eve orbit, and then cool off before entering.

I have been toying with something similar (for no particular reason except to try). Through ample use of the KSP flight-simulator feature (i.e., alt F12, set orbit, revert) I convinced myself that that a light wing-loading space-plane can slow itself from low Eve orbit by pitching up 90° until the speed comes down to 2200m/s.  I don't have anything near a complete return vehicle yet, though.

I also searched for other's previous attempts and found that Brad Whistance posted a video of a mission very similar to your plans.   You might (or might not) want to see what he did for inspiration, and then do it in your own style.

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10 hours ago, Snark said:

Orbital velocity at Eve is around 3400ish for a low orbit, which is...

And just to reiterate, that is from LOW orbit, meaning you've already presumably used your engines (or less likely, aerobraking) to get into such an orbit.  If you're trying to go straight from an Eve flyby to reentry, the velocity is going to be a lot higher.  Every time I have tried that, every unshielded part goes poof pretty quickly.  

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Ignore the people saying it can't be done. It's possible, though tricky, and it feels incredibly cool when you do. A checklist of things you need to remember:

1. Use parts with the highest possible thermal tolerances, all the way across the board, but especially if they're either on the underside or near a leading edge. Mk3 stuff is ideal for this purpose.

2. Enter unloaded. You're planning to use ISRU so you should be close to that anyway. This will save you having ridiculously overbuilt wings on takeoff.

3. Don't enter directly from a flyby. You will explode if you try. Instead, insert yourself into an atmosphere-skimming Eve orbit -- 100x100 puts you just barely above it. I use a burn to do so because it saves piles of playtime, and given your flight plan you should be able to do so easily as well.

4. Only drop your periapsis just a bit; 80km is more than enough.

5. You must be able to maintain a high angle of attack (45 degrees+). This means that your craft needs to be controllable even when all your aerodynamic surfaces are stalled out. Heavy duty RCS is very useful here (and can in fact be muscular enough to act as landing engines on e.g. Minmus).

6. You need to be able to bring it back to conventional flight once you're down below about 1.5km/s. Again, heavy duty RCS is helpful. Between this & #5 you also need very careful attention to your aerodynamic design; try and make it just barely stable for maximum agility.

7. Be prepared for lots of explosions in the testing stage.

 

Oh, and a horizontal Eve launch to orbit is plenty possible too. The nice thing about a spaceplane takeoff on Eve is that you can ignore the TWR > 1 requirement of a vertical launch and instead pack a larger amount of fuel until you jettison your wings. I generally build so that I get rid of them once my Eve TWR has hit around 1.5, pitching to vertical as I do, somewhere around 8km for a sea level launch. From that altitude and with the speed already accumulated you could proceed to orbit on a single stage, potentially, but I've found a two-stage approach works much better.

 

Edited by foamyesque

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2 hours ago, foamyesque said:

Ignore the people saying it can be done.

I thought that was the whole point of asking, to know how it can be done. >8]

@A_name as you can see thee answer are either "yes, if you are coming at full speed from interplanetary space" or "not if you first slow down to a more sensible speed". How feasible is that for your situation depends on your actual craft and mission design.

Same for the how to attach a heatshield without ruining aerodynamics if you decide to do so. Personally I'd try something along the lines of a inflatable heatshield 'sandwich' and some nosecones and fairings to keep things aerodynamic.

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21 minutes ago, foamyesque said:

Heatshields are for the weak :mad:

Arguable. But convenient, nonetheless.

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4 hours ago, foamyesque said:

a horizontal Eve launch to orbit is plenty possible too. The nice thing about a spaceplane takeoff on Eve is that you can ignore the TWR > 1 requirement of a vertical launch and instead pack a larger amount of fuel until you jettison your wings. I generally build so that I get rid of them once my Eve TWR has hit around 1.5, pitching to vertical as I do, somewhere around 8km for a sea level launch. From that altitude and with the speed already accumulated you could proceed to orbit on a single stage, potentially, but I've found a two-stage approach works much better.

 

This is what interests me most. If you wanna put something on the surface, you can put it on the surface. The trick is usually whether or not you can take what you put on the surface and bring it back to orbit. From sea-level is even tougher. To do so with a horizontal takeoff, I think, adds a whole new level of difficulty. Do you still have your screenshots? Of the ascent itself, I mean. I'm coming to love going to Eve almost as much as I hate it, and soon I expect the balance will tilt in the right direction. Mostly because I intend to keep going back until it's as routine as anywhere else. I don't put wings on anything unless I have to, and I know it's not the subject of the thread, but a successful horizontal takeoff definitely has my interest.

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Unfortunately, my full screenshots of the ascent profile are lost. Peculiarly, the Mammoth engine powering it is generating much less thrust than it used to, which means I can't even refly the mission to demo for you. Gotta rebuild the entire vehicle.

 

That's gonna be a pain.

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29 minutes ago, foamyesque said:

Unfortunately, my full screenshots of the ascent profile are lost. Peculiarly, the Mammoth engine powering it is generating much less thrust than it used to, which means I can't even refly the mission to demo for you. Gotta rebuild the entire vehicle.

 

That's gonna be a pain.

No problem. I used the Mammoth on my last rocket, too. Wanted to send 2 Kerbals, no drilling, and it worked, but not with much to spare. I plan to send a spaceplane eventually (as part of my overall goal of conquering the purple devil), but I intended to land and takeoff vertically. I would love to do a true horizontal takeoff, though. I would be absurdly pleased with myself. So, if you succeed with your new design (and you remember this thread), throw up a post. Eve keeps drawing me back for some reason.

Edited by Cpt Kerbalkrunch

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