Illustrated SSTO guide for 1.0.x

[nestor_d]

So, as we all have noticed by now, SSTOs have gotten kind of difficult in version 1.0. I think I have been relatively successful at creating them, so I decided to make this guide, hope it helps

The part about the flight plan is also here in video form:

Also, you can check this KerbalX hangar, where I've put all the successful SSTOs I've managed to create http://kerbalx.com/hangars/2183

Edited June 1, 2015 by nestor_d

[ThrillBird]

Interesting! Though I have one question, what altitudes are we talking about when you mention "middle atmosphere" (section 4)? Is it like 10-20 km, or what?

[nestor_d]

Yeah, around that. I don't remember the exact altitudes, but if it's any help, the colours I used in the drawing correspond to the colours in the altitude indicator on your user interface in KSP, so the colours should be enough to know the exact altitudes. I think the middle atmosphere starts a little lower though, around 8km, but as I said, I don't remember exactly

[surge]

There's quite a few grammar mistakes in this. I can't cut 'n paste them for you because you presented it as an image, but maybe you should proof read it (many are just missing words).

Also, the 'moar intakes' thing has always been a common, but dubious recommendation, more so now that drag is somewhat more realistic. While modifying one of my SSTOs for KSP v1.0, I had to remove all the extra intakes to get it into orbit. I personally use the mantra 'drag is everything', but you've already covered drag well enough.

Otherwise, nice to see a fairly good SSTO tutorial for 1.0 - it's a difficult topic.

[Mister Dilsby]

I love the ascent profile graphic--but yeah, 'moar intakes' just isn't correct since 1.x. I have never had a successful SSTO design that used more than one ram intake per turboramjet (I tend not to use RAPIERS, those might be different), and I have never fixed an UNSUCESSFUL design by adding intakes beyond 1/engine.

Agree with @surge also on "drag is everything" -- while the key to SSTO in 0.90 may have been "get all the air you can and fly higher", the key in 1.x seems to be "get all the thrust you can and go faster" -- so optimal wing area is MUCH reduced. You just need enough wing to lift at low thrust in the thick atmosphere. By the time you get to the middle and mach 1 you will have so much thrust you barely need wings at all, and when you enter the high atmosphere at 1200 m/s the wings are mostly useless anyway.

Note, IRL, THIS is what the wings on a high-altitude supersonic interceptor look like:

Anyway, this is a good guide and I appreciate you taking on the work. Hopefully there are some good comments here so you will be able to make it even better.

[nestor_d]

Yeah, I've recently noticed all the typos, I will fix it soon. Regarding the intakes thing, all this really came from trial and error, but I had three suborbital spaceplanes that turned into SSTOs by doing nothing more than adding a few radial intakes. It might have been coincidence, but I do think the extra air helped.

- - - Updated - - -

I think I may have found the problem with the MOAR intakes thing. Two of the three spaceplanes I fixed by adding radial intakes had less than 1 RAM intake per RAPIER. It might be that you just need at least a 1:1 ratio or the equivalent, so if your design didn't allow for exactly one intake per engine maybe compensating with radials helps. I will definitely take this into account for the revised version.

[surge]

Ah yes, the F-104 starfighter a.k.a. "the widowmaker", named for it's T-tail design and extremely small camber/low lift wings that tended to kill people at subsonic speeds. A perfect example of the yanks outdoing the kerbals

Joking aside, that photo doesn't show it but those wings are very thin - maybe about 20cm at the chord root. That's how important drag is IRL.

Pity the wings in KSP are all barnyard doors still, but that's 1/2 the fun isn't it.

@nestor_d I notice that you seem to be tending towards really large planes... you may want to take into account that there is a fairly large difference in building philosophy between small and large, namely 'drag is everything' for small ones, but it doesn't matter so much when your plane is already a giant brick and you just need every little bit of power you can get.

Continue to play around with it and inform us of your findings. I will continue to do so too, but my space program is focused on other things at the moment.

Edited May 28, 2015 by surge
new post while i was proofreading