Can't get SSTO to orbit.

[tbarcello]

Yes, that's what I mean. I've never had the overheating you describe.

My ascent profiles go like this.

1. Take-off and ascend to 9 km.
   
2. Build up speed to 1000-1050 m/s in level flight.
   
3. Ascend at 15 degrees. (10 degrees for low TWR, but yours has plenty)
   
4. Engage nukes at 18 km.
   
5. Should reach 1200+ m/s at 20 km.
   
6. Keep ascending at 15 degrees.
   
7. Turn prograde when AP is above 70 km.
   
8. Throttle down when AP is above 80 km and coast to circularization.
   

Yeah, many mentioned different hints in this thread, which i think helped me troubleshoot this. I'll test and report back tomorrow.

[Stoney3K]

Both,so far the most efficient SP SSTO's use both or only Rapiers (Rapiers give more thrust but also consume more fuel).It's also a bad idea to have an engine as dead weight while in the atmosphere but it is even worse if you have an engine on in the atmosphere with a bad surface ISP.

I prefer a combination of jets and rockets, because that allows you to use jet and rocket thrust together for the upper atmospheric ascent.

Jet thrust will start falling off at 18km but they will only flame out at over 25km (at which point a Rapier switches mode). If you only have jets or rapiers, they will give a minute amount of thrust which is only used to fight drag. That thrust increases with a higher Mach number.

Using rockets AND jets for that part of the atmosphere means the jet intakes get more air, the intake velocity is higher and you get more thrust from just your rockets. Overall this means a bigger kick than using either jets (which have very limited power at that altitude) or rockets (which have a bad Isp under 23km), resulting in a more constant acceleration during your ascent.

[Val]

I prefer a combination of jets and rockets, because that allows you to use jet and rocket thrust together for the upper atmospheric ascent.

Jet thrust will start falling off at 18km but they will only flame out at over 25km (at which point a Rapier switches mode). If you only have jets or rapiers, they will give a minute amount of thrust which is only used to fight drag. That thrust increases with a higher Mach number.

Using rockets AND jets for that part of the atmosphere means the jet intakes get more air, the intake velocity is higher and you get more thrust from just your rockets. Overall this means a bigger kick than using either jets (which have very limited power at that altitude) or rockets (which have a bad Isp under 23km), resulting in a more constant acceleration during your ascent.

While this is true for Jets and LFO rockets, things change when your vacuum engine is a nuke.

This (useless) SSTO I built for Is it even possible to make a <15t laythe roundtrip SSTO? gets much more dV to orbit with a pure air-breathing Rapier, than it does with a Jet. I can't explain why, but I'm guessing the higher thrust and top speed, makes up for the lower ISP.

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And I also believe Rapier and Nuke based Spaceplane SSTOs are the most efficient, at least according to the Stock Payload Fraction challenge. The top 2 Single Stage entries in the Air-Breathing category are Rapier+Nuke designs.

Edited September 2, 2015 by Val
Spaceplane

[Nich]

I have to agree with Val sounds like a broken cfg. Try removing the radiators they could be conducting heat into the engines. I am surprised your wings are not the first things to blow they look like 1200 degree airliner wings

[FyunchClick]

I am surprised your wings are not the first things to blow they look like 1200 degree airliner wings

They're pretty sturdy, I've put them on a huge 160 ton ssto plane and they never got a temp gauge either doing a powered mach 4.5 or during reentry after LKO.

From the excellent advise of both Val and GoSlashy27 and many others in different threads, I was able to figure out how to ssto and my third attempt was this huge MK3 based thing that gets to orbit with oodles of dV to spare (enough to get to low minmus orbit, and there to refuel for the trip out to Jool). It does so on just 6 rapiers, 4 whiplashes and 2 LV-Ns (who are just there for the interplanetary bit and hardly contribute at all to getting in orbit. Engine types/ratio suggested by goslashy27 btw, thanks it works like a charm.

My second successful SSTO was an R2 with four rapiers and two LV-Ns (one of which I could have probably dropped) for engines, with a cockpit, passenger cabin and the mk2 docking port as payload. It easily reaches orbit with 2 km/s of dV left in the tanks, and only uses a pair of Big-S delta wings and a pair of canards for lift. Less really is more.

Edited September 2, 2015 by FyunchClick

[tbarcello]

There. Got to orbit with 500 delta v. Useless to me, but pakin did it!

Thanks to everyone. I added just 1 more nuke and replaced precooler with tanks tanks. And that was it. I'm done, it's answered.