SSTO question

[jaddbo]

my question is: is there some kind of a trick to building and flying SSTO's? I can never get them to work for me. they always crash or fall back to Kirbin or do not have enough thrust.

please help!

[Vanamonde]

They are probably the hardest thing to do in KSP. I've been playing this game for 2 years and still only have one design that worked reliably, and it could carry no cargo. That was before they introduced the Rapier engine, though. I should probably try again.

Anyway, hello and welcome to the forum.

[Pecan]

SSTO rockets are far less efficient than staged ones - that being the reason for staging!

As with all rockets it's vital to know your total deltaV - in addition to the 4500m/s generally necessary for launch-to-orbit you'll need to budget at least 200m/s for returning. A parachute-assisted powered landing appears to be most efficient; provide at least 200-400m/s deltaV and a couple of drogue parachutes. More deltaV may be required if you will be using the engines for controlling your landing more under power.

The KR-1x2, with enough fuel, solar panel, battery, etc. is capable of SSTOing a 10-tonne payload, de-orbiting, and powered landing.

[Clockwork_werewolf]

There are two keys to SSTO. Plane design and air intake.

The more intake you have per engine the more air you get at higher atmo and the longer you can fly with jets/rapiers in air mode. The higher you go in air breathing mode the faster and higher you are when you switch to expensive rocket mode. With 12 ram jets per engine (called air hogging ) you can sometimes get out of the atmo (but not with a similar PE) on air breathing alone.

Designing the plane is also important. Getting it to fly right in low and high atmo, not getting flameouts in the engines, adjusting angle with little atmo and other plane problems are hard.

As with all rockets it's vital to know your total deltaV

Not really, I've never used a deltaV readout and I've got 30 tons to orbit with SSTO's. It can help a lot with designs for rockets but on space planes it gets complicated due to skimming across the upper atmosphere for a while.

[Wanderfound]

my question is: is there some kind of a trick to building and flying SSTO's? I can never get them to work for me. they always crash or fall back to Kirbin or do not have enough thrust.

please help!

How to fly a spaceplane to orbit:

1) Get to 20,000m however you like. Around a 45 degree climb is probably most fuel efficient, but jet engines use so little fuel that it doesn't matter much. If the plane has enough power, I usually climb at 75 degrees or so just to get it done quickly.

2) When you get to 20,000m, level off and build some speed. You want to pile on as much horizontal velocity as possible while you make a slow ascent to 30,000m. Keep your angle of attack (the angle between where your nose is pointing and the direction in which the plane is actually moving, shown by the prograde marker when in surface mode) and climb rate low; by the time you hit 30,000m, they should both be around 10 or so. A low angle of attack reduces drag and helps your intakes work better. The low angle makes you climb slower, but that's okay; you need that time to get up to speed. As you go faster, the angle of attack required to maintain a given climb rate reduces, but as you go higher, the thinner air means that the angle of attack required to maintain a given climb rate increases. If you do it right, these two factors will roughly balance each other out and you should gain the necessary speed and altitude in a single smooth climb. However, a plane with some aerodynamic or piloting flaws may need to bounce up and down between 20,000 and 30,000m a couple of times while building speed before the final push.

3) Somewhere between 20,000m and 35,000m (exactly when depends on both plane and piloting), you'll start to run short of air. Don't switch to rockets immediately. If you've got multiple engines going, shut some down to concentrate the available oxygen into the ones you keep running. If you've already shut down as many as you can, throttle back a bit. You can dramatically increase your jet-only altitude by doing this, and once you get up to serious height the thin atmosphere means that you only need a tiny amount of thrust to accelerate.

4) Keep this going for as long as your plane and your patience can tolerate. A well-built and -flown plane should be able to get over Mach 4.5 and 30,000m in a single attempt on jets alone. Once you've wrung as much speed and altitude out of the jets as possible (you want at least Mach 4 and 30,000m), force the nose up to 45 degrees and light the rockets. If you have both jets and rockets, don't shut down the jets immediately; the thrust of the rockets will drive a ram-air effect that kicks the jets back into life for a while. Keep the rockets burning until your apoapsis exceeds 70,000m, then shut off and coast until it's time to circularise. Point prograde and close your intakes while coasting to minimise drag.

A good plane and pilot should be able to get the apoapsis to 70,000m with less than a minute of rocket power. Done properly, it requires very little fuel. But if you try to brute-force it from lower speeds and altitudes, the atmospheric drag is going to drain your oxidiser tanks before you get anywhere near orbit.

If you're having trouble with design rather than piloting, give http://forum.kerbalspaceprogram.com/threads/89092-Kerbodyne-Scattershot-a-simple-and-easy-to-fly-beginner-s-SSTO-spaceplane a try.

[jaddbo]

I have seen some air-hogging designs, and I do feel like it is cheating with that. I prefer non-air hogging designs.

thank you to everyone who replied, you guys are the best!

There are two keys to SSTO. Plane design and air intake.

The more intake you have per engine the more air you get at higher atmo and the longer you can fly with jets/rapiers in air mode. The higher you go in air breathing mode the faster and higher you are when you switch to expensive rocket mode. With 12 ram jets per engine (called air hogging ) you can sometimes get out of the atmo (but not with a similar PE) on air breathing alone.

[Wanderfound]

I have seen some air-hogging designs, and I do feel like it is cheating with that. I prefer non-air hogging designs.

Likewise.

Air-hogging is not necessary on a well-built plane. I generally limit myself to one nacelle/ramscoop combo per engine, and occasionally a couple of radials (largely unnecessary, but I like the way they look). Works just fine.

[Clockwork_werewolf]

Yea I try not to use air hogging and definitely don't use ram intakes on cubic struts shoved inside each other. I once made a plane this way and it was a bit insane what it could do. http://forum.kerbalspaceprogram.com/threads/68350-SSTO-intake-stacking-questions?p=950430#post950430 It got to the Mun and back without trying.

I think the big problem with the intakes is their mass. While the ram intake should have its intake multiplied by eight so it can be used in the high atmo (Skylon will be able to something like this) its mass is just a joke. 0.01 for an intake means why wouldn't you (apart form aesthetics and Roleplaying) stick 12 of them on a ship per engine? Its mass is less than 1% that of the jet engine. 12 rams are equal to just 10% the mass of the engine.

If each Ram intake had 8 times the intake but 60 times the mass then it would weight 0.48 (less than half the weight of an engine) but its increased drag (due to KSP's drag = mass x area) would mean that top speeds in the atmo would be reduced so that you couldn't get an out of atmo AP without rockets. Its worth noting the Skylons only has one intake for each engine and they are the width of the engines so my suggestion isn't unrealistic.

[Bilfr3d]

Air hoggin? I love it I hog all the airs... being around 20-40 units on air on my SSTOs... which still fail to make a full orbit.

[Tex_NL]

This is one of my most successful SSTO designs.

My Hammerhead does have multiple intakes but not to the level of air hogging. It can launch 4 Kerbals to LKO with ease. Vertical climb to 10 km to escape the worst of Kerbins soupy atmosphere. Them a slow steady climb to 30km (30% throttle) before switching engine modes.

It's also the plane I've successfully used for rescue missions multiple times.

[Pecan]

...Not really, I've never used a deltaV readout and I've got 30 tons to orbit with SSTO's. It can help a lot with designs for rockets but on space planes...

Well yes, "It can help a lot with designs for rockets", which is exactly what I said. The OP didn't say anything about spaceplanes, he asked about SSTOs.

[Clockwork_werewolf]

Well yes, "It can help a lot with designs for rockets", which is exactly what I said.

You said "As with all rockets it's vital to know your total deltaV".

Vital: adjective 1. absolutely necessary; essential.

As a delta-V readout is not essential I thought it worth mentioning that you don't need one as you stated.

As to flying the SSTO's I do see now that he was asking about building AND flying SSTO's. I read this as building flying SSTO's and as most people usually mean this I missed a beat. He did however go on to talk about air intakes which greatly suggests he was trying to make a plane SSTO.

[Pecan]

Vital: adjective 1. absolutely necessary; essential.

Yep, you win; knowing your total deltaV is not absolutely essential, therefore not vital.

And, for the record, I too think the OP was originally asking about aircraft and certainly went on to do so. That doesn't alter the fact that it's wrong to equate Single Stage To Orbit with 'spaceplane' and I was, specifically, talking about SSTO rockets. People also mistakenly talk about 'SSTO to xxx planet/moon', which is just senseless (as is lugging wings across the system to anywhere except Laythe). The more that people incorrectly conflate terms, the more reason there is to correct them ;-0

To wit: i) spaceplanes do not have to go to orbit in a single stage even though most do, ii) rockets can SSTO quite easily even though most don't, iii) if you want to 'SSTO' to another planet or moon the most sensible thing to do is stage all that useless jet and wing mass once you've got to orbit.

[Clockwork_werewolf]

Yea I've more than once wondered whether to enter a Rocket SSTO into a SSTO showcase/competition and that was with the old mainsails being the best T/W engines (aside from batteries of 48-7S's) . Rocket SSTO's certainly need more time than people seem to give them. I think there is an aesthetic beauty to (some) space planes that gets them all the attention.

[Hodo]

Yep, you win; knowing your total deltaV is not absolutely essential, therefore not vital.

And, for the record, I too think the OP was originally asking about aircraft and certainly went on to do so. That doesn't alter the fact that it's wrong to equate Single Stage To Orbit with 'spaceplane' and I was, specifically, talking about SSTO rockets. People also mistakenly talk about 'SSTO to xxx planet/moon', which is just senseless (as is lugging wings across the system to anywhere except Laythe). The more that people incorrectly conflate terms, the more reason there is to correct them ;-0

To wit: i) spaceplanes do not have to go to orbit in a single stage even though most do, ii) rockets can SSTO quite easily even though most don't, iii) if you want to 'SSTO' to another planet or moon the most sensible thing to do is stage all that useless jet and wing mass once you've got to orbit.

I would have to argue this.

If you plan on returning with that craft or go to any planet with an atmosphere wings are useful. At the very least a lifting body design is a must. I have sent SSTO space planes to Duna, Ike, and even Moho. I have recovered all of them. And I can say the wings were useful, or more than useful on Duna and on recovering the craft back at the KSC. Were the wings useful on Ike or Moho, not really, but the craft was designed to land VTOL on most worlds anyway. The wings helped because I had the VTOL engines set out away from the centerline of the craft to give it a wider thrust base for stability.

Wings are never useless unless you don't plan on bringing the craft back. In that case just slap your kerbals in a can and launch them on their one way mission to where ever they maybe headed.

And argueing the point about SSTO rockets is a pretty moot point due to the fact that in real life most rockets are staged because of the large delta velocities required to achieve orbit.

Kerbin-2.3km/s Earth-9.4km/s

Kerbin-69.1km Earth-180km Atmosphere height

While I build SSTO space planes and rockets in stock kerbin all the time, I am hard pressed to get one functional design in Realism Overhaul with the RSS correct scale Earth.

[SRV Ron]

SSTO with rockets is most useful for small probes to orbit although it is possible to reach Mun or Minmus with one. While a large single stage can also reach low orbit, it is more efficient if you two stage them with the payload. Turbojet engines can also be used although you don't have to use them as a aircraft. Examples below.

This will do Mun orbit and return if flown carefully. At staging, you should be doing close to 2,400 m/sec at 38,000 meters, the flameout point of the turbojet.

Flameout;

The turbojet booster is recoverable.

All rocket SSTO for a satellite;

More practicable

[Pecan]

...Wings are never useless unless you don't plan on bringing the craft back...

Wings are excess mass in vacuum.

Excess mass is bad.

SSTO your Moho ship by all means, then decouple all that useless excess mass before your transfer. Redock when you come back and want to land. Carry one docking port the rest of the way or a pair of wings, engine(s), etc. that are useless; you do the maths.