SSTO Spaceplane with Nuclear

[m4rt14n]

Hi all,

Pretty new to KSP. I've gotten to Duna and back with multiple stage rockets in career mode. Right now I'm messing around with Spaceplane.

Boy it's hard. It's either:

a) veering off to left and right

spinning all over the place after taking off

c) not taking off until the end of runway.

Anyways, I've managed to get a SSTO to LKO and back. But I'm trying to see if anyone ever managed to get SSTO to Mun/Minmus/Duna without refuelling? My guess is you need to stick a nuclear engine in there and a turbojet to get off the ground. Do you put in a Aerospike to get to LKO first? Cos I've tried the Rapier and it wont even take off the landing strip..

Any ideas? Please no mod/cheats/clipping...

[bsalis]

2 turbojets, 2 RAPIERs, 1 LT-N.

I think that engine combo would be a good mix. Add as much fuel+oxy as they can lift to high altitude and ample air intakes and you should do fine.

[DeMatt]

If you're just trying to fly an SSTO to LKO, no worries about cargo or anything, a single Rapier can indeed carry a simple spaceplane into orbit. But you really need to take to heart the saying, "less is more".

This is a very basic SSTO. I did tweak the amount of monopropellant (in the cockpit, down to zero) and the amount of jet fuel (in the center Mk1 tank, down to 75 units) - right-click on a part in the hangar to adjust its stats if doable. Other than that, nice simple flight profile: turn on SAS on reaching the runway, Caps Lock to activate "fine" control, throttle to maximum, Space to start rolling. Rotate (pull up) around 90m/s, retract gear, 45-degree climb to about 15 km altitude, level more-or-less out and accelerate. Should hit about 25 km altitude by 1500 m/s speed before it switches to rockets, at which point pull up to 45 degrees and switch to map view to watch your apoapsis. Cut throttle once apoapsis reaches 75 km, then perform a circularization burn; that should leave you (depending on how much of your speed you were able to gain from jet mode versus rocket) with about 5% fuel remaining.

The above spaceplane only masses about eight tons on the runway. To be honest, that's about all one Rapier can be expected to lift. A one-turbojet/two-Rockomax-48-7S combination can probably lift more like ten or twelve tons.

Veering to either side on the runway probably has to do with your landing gear - make sure it's precisely vertical; also, use your SAS and let it keep you straight. Spinning out probably has more to do with overcontrolling; Caps Lock for "fine" control, and don't try to turn your nose far from your direction of flight. Being able to rotate depends on the plane being able to lift the nose, as opposed to pushing the tail down; building your plane canard-style (tail-first, instead of the conventional tail-rear) does wonders for that.

Edited January 17, 2014 by DeMatt
...got the tonnages way off.

[Silverchain]

My heavy (~16-17 tons on the runway) spaceplane/rovers have just enough in the tank to get to the Mun's surface and back with careful fuel management. They use a central LV-N and a pair of Turbojets (usually 2 ram and 8 radial intakes) and the flight profile is to climb to ~28km / 1600+ms-1 using jets (at which point they're really struggling) then switch on the nuke (which at that altitude is operating at full efficiency), point up to 30ish degrees, wait for the jets to cut out and fly the rest of the way on nuclear.

The key thing I found was positioning the long and unwieldy nuclear engine in such a way that it didn't get trashed on landing.

I've flown one to Duna but I used a fuel pod - haven't tried doing it using only the internal fuel, that's probably a one-way flight without some fancy gravity assists.

Edited January 17, 2014 by Silverchain

[wasmic]

I've seen someone who build a spaceplane that could get multiple tons of cargo to Laythe, and then return to Kerbin, in a single stage. The cargo was three wheeled hitchhikers and some fuel. The spaceplane was freakishly huge, four LV-N's and a massive amount of turbojets.

Oh, and I'd use a lot of ram air intakes, the radials become dead weight above 18 kilometers, so don't bother with them. Some people have build SSTOs that run on jets until they're 55 kilometers up. Myself, I've only ever managed to get 1 kerbal to orbit in an SSTO spacceplane.

[barrenwaste]

There are multiple ways to go about getting to the mun and minmus. To get out further you either need a large ssto with plenty of extra fuel or ion engines and a slow burn. As for the mun and minmus, I prefer to use smaller sstos. I don't really like the rapier, myself, I prefer a combination of turbojets and small rocket engines or an atomic. I suggest you practice building normal planes that can achieve extreme speeds and altitude. If you do this you can get the ssto out of the atmosphere before you ever burn a rocket. I think that if you combine these elements you'll find you can get into a stable orbit with half you fuel and almost a full tank of oxi for your trip to the mun.

[Devinci]

If you take some of the weight or fly it better you can get to the Mun.

[Silverchain]

Oh, and I'd use a lot of ram air intakes, the radials become dead weight above 18 kilometers.

I don't find that to be the case - if I take one of my spaceplanes and strip the radial intakes off, it can't reach the same ceiling. There is a point at which adding radials doesn't produce a return, but I think it's higher than 18km. Might try some tests later. If there was an 18km boundary, perhaps something in the mechanics has changed since, or perhaps the extra storage capacity provided by the radial intakes helps somehow even if they aren't filling.

It's tricky to mount large numbers of ram intakes without it being unsightly - I've never really found a satisfactory looking way to attach them.

[barrenwaste]

@Silverchain & Wasmic

You can go much higher than 18k with radials.

[numerobis]

You need 2.5 radial intakes to make up for a ram intake, so you'll have 2.5x the mass and drag for your intakes, but they definitely work at all altitudes.

One ram intake per tonne of mass (or 2.5 radials) will let you just barely reach orbital velocity on turbojets alone.

With one turbojet per 15t it's fairly easy to get to upper elevations. That gives you TWR of 0.75 on liftoff, 1.5 at 1000 m/s (usually around 25km), and declining afterwards.

[Silverchain]

Cool, thanks for the information. You may imagine the light bulb going on over my head; I've been reading the descriptions backwards in the SPH, thinking the irrelevant stored amount was some strange multiplication factor for the intake area (which makes no sense at all) instead of just going off the intake area. I knew it didn't make any sense from the practical performance I understood well enough how they compared!

[SuperBigD60]

If you like SSTOs, FAR makes them a little simpler to build, IMO.

Though, they do get harder to fly (sort of, I might just suck as a pilot...actually, that's much more likely) and because all jets with FAR have very little thrust past mach 5, getting the plane to another SOI would probably get harder.

[capi3101]

a) veering off to left and right

Usually that's a sign that either your landing gear isn't on exactly perpendicular or you've got too much of a load on them. Check it again and consider adding additional wheels/struts. Or big rudders...

spinning all over the place after taking off

Set SAS on once you're heading down the runway. If that doesn't help, you might check the position of your center of lift; ideally you want it slightly behind the center of mass and at least in line with it horizontally (for more stability, you might want it slightly above the center of mass - though I can't say one way or the other what that'll do for your steering).

c) not taking off until the end of runway.

Put the back wheels relatively close to the center of mass longitudinally; that should help with that. Of course, if you're also having problems with tail strikes, going the distance on the runway is not necessarily a bad thing. Just make sure you don't hit those big spotlights on the end without an ejection system installed.

Now, so far I've had a successful one-man SSTO with a single turbojet and two 48-7S's, and that's about it. I haven't tried to go anywhere with that, but the design had two FL-T400 tanks and about 2,000 m/s of delta-V, so Mün and Minmus flybys would be in the realm of possibilities for it.

If you want to use nukes, I might suggest moving their fuel tanks forward far enough that the engine bells align with the turbojet exhaust. That'll move your center of mass forward a bit and probably stress those back wheels some more; not sure what other negative effects that might have, but it would reduce the chance of tail strike.

Edited January 17, 2014 by capi3101

[numerobis]

Cool, thanks for the information. You may imagine the light bulb going on over my head; I've been reading the descriptions backwards in the SPH, thinking the irrelevant stored amount was some strange multiplication factor for the intake area (which makes no sense at all) instead of just going off the intake area. I knew it didn't make any sense from the practical performance I understood well enough how they compared!

Perversely, capacity only matters if you have lots of air available: if the air intake produces more air in a physics timestep than fits in the capacity, the excess is lost. You can reduce the loss by reducing your max physics deltaT in the settings.

[theend3r]

http://forum.kerbalspaceprogram.com/threads/65397-SSTM-B-%28Single-Stage-To-Mun-and-Back%29

[kopapaka]

It's tricky to mount large numbers of ram intakes without it being unsightly - I've never really found a satisfactory looking way to attach them.