1.02 SSTO Fallacy?

[GarrisonChisholm]

Good morning. I'm still playing 1.02, partially because that's what I started on and want to see it through, and also partially in the hope that eventually the "Launcher" will update my game automatically- saving me the trouble of not goofing up the install again. The issue I have discovered is that it seems impossible to build an SSTO (SSTSpace, Yes) in v. 1.02 using the earliest practical technology.

I have followed SSTO guides, and with the classic combo of 2 Whiplash & 2 LV-45's I just cannot get there. I get to space and find myself just short of fuel, so I add some fuel...and find myself still short. I add a second pair of jets & more fuel, ...and again find I need more fuel. It seems no matter how I tweak and massage the weights, I reach space with only 1/2 the DV i need.

Is *this* addressed by the 1.03/4 atmosphere upgrade? Is there something fundamental I am missing?

Edited July 16, 2015 by GarrisonChisholm

[luizopiloto]

No, it got even worse in 1.0.4... Jet engines are very thirsty... and weak...

[GarrisonChisholm]

...well, phooey. :| ...I guess you simply have to wait for Rapiers then.

[Guest]

Pretty sure people made turbojet SSTOs back in 1.0.2. The drag in 1.0.2 was higher, though, so you either need more engines or a modified ascent profile to punch through the transonic barrier

[Korizan]

The Rapiers was my answer http://imgur.com/a/nmRu8 at 34 tons it appears to be the limit for dual engines before you have to upscale.

In 1.0.2 I had more rocket fuel in 1.0.4 I replaced a fair amount of rocket with normal fuel as others have said air breathing now consumes a lot of fuel.

This one is just a passenger shuttle which works for me, I am sure there are better ones but I find it is easier to move the cargo in expendable rockets.

I think to many agency's in RL are too hung up on an SSTO cargo carrier instead they should just make one for people and be done with it.

Edited July 16, 2015 by Korizan

[ZentroCatson]

The problem probably is that you are doing it wrong. A couple days back I made my first good SSTO, and I learned a lot out of it. First, your ascent profile. If kerbal engineer gives you ≈1.00 TWR with your jet engines, you should do a shallow ascent profile with about 15º pitch until 10 kilometers. Be aware, Scott Manley forgot one important thing in his SSTO guide. After 10 kilometers, your TWR reaches about 1.20. This is where you should flatten out even more, into an 10º climb. Then, accelerate until your jets are losing thrust. You should be moving at ≈1100 m/s at that time. As the thrust of a single jet reaches 175kn, turn on your rocket engines and start a climb. As your jets flame out, turn them off. Continue with a normal rocket climb and circularsie. I hope this helped you in your SSTO quest, good luck flying it !

[Scarecrow88]

Only today I was checking some of my old SSTO designs and discovered that none of them work with the new aerodynamics, so I set about designing a new one. Ended up with a simple ship that uses 2 turbo jets and a single LT-45, and it gets to orbit quite happily. I would suggest to the OP to try and keep it as simple as possible, keep the weight down, and learn what sort of ascent profile is required for a successful SSTO mission.

[Tarmenius]

Turbojet SSTOs were definitely doable in 1.0.2. In fact, all you really needed was a single Whiplash: Take a look at these examples

They key is to build as much speed as you can through at 10-12km. The ascent profile looks pretty different from pre-1.0 techniques.

[Red Iron Crown]

No, it got even worse in 1.0.4... Jet engines are very thirsty... and weak...

Payload fractions for SSTOs got higher in 1.0.4 versus 1.0.2. Air-breathing engines got thirstier, true, but this was outweighed by the reduced drag.

OP, Whiplashes plus a rocket engine is hardmode for SSTOs, they are much easier once you unlock Rapiers.

[SelectHalfling0]

I made a beautiful spaceplane in 1.0.2 (turbojets and regular rocket engines). It died in 1.0.4, and I can't get even one to orbit (after watching multiple tutorials).

[GarrisonChisholm]

Turbojet SSTOs were definitely doable in 1.0.2. In fact, all you really needed was a single Whiplash: Take a look at these examples

They key is to build as much speed as you can through at 10-12km. The ascent profile looks pretty different from pre-1.0 techniques.

Thank you Tarmenius! I wasn't aware of the bounty of examples available on the forum. I will be sure to search next time before I trouble anyone. And-

"OP, Whiplashes plus a rocket engine is hardmode for SSTOs, they are much easier once you unlock Rapiers."

Thank you RIC, this is the bit of solace I was hoping to find I think. Very kind of you. I'll keep trying, knowing there is a very narrow edge of success in the endeavor.

[RogalDorn]

My 1.02 SSTO works using t2 components can bring 8 tonnes into LKO and it works just fine in 1.04. It has to do less with your design and a lot more with your piloting ability. I level out at 10KM and don't turn on my rocket engines until about 20-23KM, I wait to fire the engines until velocity levels out and starts a slow decline. Then As soon as I get my Apoapsis up to 100KM I cut engines and circularize like normal. Works like a charm! As another tip it might help to manually transfer fuel from the back to the front of the ship the whole time it's running, or if you feel really froggy just disable the front-most fuel tank so fuel never comes out of it then use that as your reserve to do your orbital burn and your return trip.

Oh and Don't forget to play Protomen's remake of "Danger Zone" and "Magic Carpet Ride" the whole time, without it you would be doomed.

Edited July 16, 2015 by RogalDorn
additional content

[Tarmenius]

Thank you Tarmenius! I wasn't aware of the bounty of examples available on the forum. I will be sure to search next time before I trouble anyone.

Glad I could help! And most people around here aren't troubled by even the most frequently asked questions, so don't even worry. At worst, someone might point you toward an answer and roll their eyes, but this is generally a very helpful place.

[annallia]

I had something of the opposite experience (to those saying it is harder in 1.0.4)

I mean I was never really good at space planes most had at least a SRB assist it wasn't until 1.0.2 that I even gave serious effort to a true SSTO plane.

I did manage one that barely made it into space in 1.0.2 and then built a larger one (I do better with big, over engineered things...) which made it to space but wasn't all that much better than the little one.

In 1.0.4 however they both worked better, once I learned to fly them differently. Yeah they burned a little more liquid fuel but they reached orbit with a higher % of their base.

[rkman]

Is there something fundamental I am missing?

As the game matures it changes substantially wrt the details about what can be achieved by deploying specific technology.

[Edax]

Good morning. I'm still playing 1.02, partially because that's what I started on and want to see it through, and also partially in the hope that eventually the "Launcher" will update my game automatically- saving me the trouble of not goofing up the install again. The issue I have discovered is that it seems impossible to build an SSTO (SSTSpace, Yes) in v. 1.02 using the earliest practical technology.

I have followed SSTO guides, and with the classic combo of 2 Whiplash & 2 LV-45's I just cannot get there. I get to space and find myself just short of fuel, so I add some fuel...and find myself still short. I add a second pair of jets & more fuel, ...and again find I need more fuel. It seems no matter how I tweak and massage the weights, I reach space with only 1/2 the DV i need.

Is *this* addressed by the 1.03/4 atmosphere upgrade? Is there something fundamental I am missing?

Your engine ratios are wrong. In my experience, for an SSTO, you need more Turbojets then rocket engines. The turbojets are FAR FAR more efficient producing thrust and fuel efficiency. You'll want to squeeze as much thrust out of them as you can in the atmosphere, because nowhere else will you have a engine produce so much thrust for so little fuel. Having 2 Turbojets for every rocket engine is a good ratio to start with, but with heavier Spaceplanes, I've had as many as 13 turbojets and just 2 Poodle engines.

Think of the turbojets as the catapult that sends you into space, and the rocket engines merely there to help you limp into low orbit.

Edited July 16, 2015 by Edax

[Bloody_looser]

1.0.2 SSTOs were like flying sausages without wings and with OP turbojets. 1.0.4 definitely made SSTOs better.

[GoSlash27]

SSTOs were definitely do-able in 1.02, and they're a shade easier in 1.04, but things have changed since .90 and the old rules no longer apply.

Check this out:

http://forum.kerbalspaceprogram.com/threads/118728-Slashy-s-1-02-Spaceplane-recipe

Best,

-Slashy

[Guest]

Think of the turbojets as the catapult that sends you into space, and the rocket engines merely there to help you limp into low orbit.

What speed do you generally ignite the rockets at? I've found that I'm typically firing up the rockets at @ 1100~1200m/s, which means about half my delta-V must come from the rockets. Just curious because your analogy breaks down in my mind.

[mikegarrison]

The OP is discovering the classic problem of airplane engineering. More fuel means more lift and more thrust required, which means still more fuel is needed, ad infinitum. If your airplane is underperforming, adding more fuel is usually a very poor answer to the problem.

[Reddeyfish]

What speed do you generally ignite the rockets at? I've found that I'm typically firing up the rockets at @ 1100~1200m/s, which means about half my delta-V must come from the rockets. Just curious because your analogy breaks down in my mind.

yep; 1100-1200 m/s.

runway takeoff, then angle at 10-30 degrees above the horizon (exact angle depends on your jet TWR), once the jets start to lose air at around 18km / 1100 m/s, activate the rockets and pitch up if necessary.

[Edax]

What speed do you generally ignite the rockets at? I've found that I'm typically firing up the rockets at @ 1100~1200m/s, which means about half my delta-V must come from the rockets. Just curious because your analogy breaks down in my mind.

I generally ignite the rockets when the turbojets die. It's important to remember that the turbojets will send you far past terminal velocity, so that you'll be producing a lot of drag, so letting the turbojets wind down and letting your altitude climb higher into thinner air with the rockets engine off will save fuel. It's at 32000m that terminal velocity will no longer effect you in achieving orbit.

Edited July 16, 2015 by Edax

[Guest]

I generally ignite the rockets when the turbojets die. It's important to remember that the turbojets will send you far past terminal velocity, so that you'll be producing a lot of drag, so letting the turbojets wind down and letting your altitude climb higher into thinner air with the rockets engine off will save fuel. It's at 32000m that terminal velocity will no longer effect you in achieving orbit.

Interesting. I find that waiting until the turbojets die means I lose a lot of speed while they wind down, which the rockets then have to make up. Rocketing straight up or at an extreme angle means the same thing, essentially, because I have to use the rockets to make up all the horizontal velocity I'm missing. To each their own, I suppose.

[Red Iron Crown]

Interesting. I find that waiting until the turbojets die means I lose a lot of speed while they wind down, which the rockets then have to make up.

I have found that it is advantageous to ride the air-breathers as long as they are still raising apoapsis (which often means until they run out of air), even if that means losing speed as the craft climbs. You're still adding energy to the trajectory at a very favorable Isp.

[Edax]

Interesting. I find that waiting until the turbojets die means I lose a lot of speed while they wind down, which the rockets then have to make up. Rocketing straight up or at an extreme angle means the same thing, essentially, because I have to use the rockets to make up all the horizontal velocity I'm missing. To each their own, I suppose.

The trick to learn is that slowing down when surpassing terminal velocity is not a bad thing (unless you have a low twr). Trying to gain speed past terminal velocity means your fighting the atmosphere; wasting precious DeltaV. You can get away with this with turbojets because of their fuel efficiency, but when using rocket engines, every drop of fuel counts.