The SSTO flying guide for dummies!

[Tidus Klein]

I've started this thread for all the sad little people (like my self) that can barley get a large SSTO in to low orbit, note that this is not going to be a guide to build an SSTO just a flying and tip and hint kind of thing.

Here is my questions

• What angle of attack do I need at each altitude (steep climb all the way or level out so high?
  
• What is the average TWR of the powered flight and rocket mode for a SSTO ( my average is 2.55 for flight and 1.11 for rocket.)
  
• What altitude is needed before rocket turn over? (personal I would like to be at 35,000 before I switch, my highest though is 21,000.)
  
• Is faster really better? how much speed is recommended? (my fastest so far is 1,300 m/s
  

Let me be clear here I could easily build a small ssto and orbit all day long, I'm looking for help in getting a fairly large cargo plane to the mun. (I will post images of the unfinished prototype later)

All help is welcome!

[cloudx]

How large are we talking about?

[Synapse]

From what I've read you just cover it in wings. Each wing has a "lift rating" so enough wings and you will take off. It doesn't even need to be aerodynamic at all.

[Palec]

I also had an issue with it but then I found perfect guide on this forum. I don't have his name but I copied it to my notes, hope it helps:

===

Flying it is very simple, just climb fast to 10-15km then level out, kill most of your vertical speed and gain velocity as high as possible. Climb slowly from 15k, preferrably within 10 degrees over the horizon, so that you can push the plane to the fastest possible speed without losing air. As you go faster, you get more air intake, allowing yourself to climb even higher without flameouts, allowing yourself to speed up more due to lesser drag. When air intake gets into 15-10% area, cut the throttle of the engine to 75% and continue to climb, that will cut air intake requirements significantly and will delay the flameout further. Cut the throttle further just before the switch if you can sustain the vertical speed with it. Also, don't forget to watch your prograde vector on the navball and pitch upwards: at high altitudes, nothing ever flies horizontally oriented as there is too little air to hold you. If you want to fly horizontally, find an angle of attack that will keep you there, which will be noticeably higher than horizon. When I'm saying "climb within 10 degrees" , that's your prograde marker, not your spaceplane orientation, which could be 30 degrees up even.

Ideally you should be going no slower than 1200-1500m/s and no lower than 25km at the point of switching to oxidizer. Return to full throttle upon switching to it, keep going almost horizontally while stabilizing yourself with RCS. It's best not to burn upwards, keep burning almost horizontally, maybe 20 degrees upwards if you insist on reducing little drag that is left at this point even faster. Getting extremely long trajectory to AP is better than getting up there with a steep trajectory as it will be a lot easier to circularize when you already have most of the orbital velocity needed. Ideally, you will only need a quite short push at AP to raise your PE over the surface and into low orbit.

===

[Tidus Klein]

Cloudx the best way I can say it with out pics is this way.

Take the B9 hyper sonic front stick the S2 sas wheel the S2 wide body intake adapter on it 4 or 5 wide body LFO tanks wide body 3.25 adapter then hook up two HL 2 M cargo bays and the wide tail ramp. (bty) I'm have 12 stock turbo jet engines on the B9 heavy wing and 2 saber Ms on the back cargo bay. In other words not crazy massive but rather big.

Lately I have been experimenting with engines and intakes on smaller craft and found that the Saber s intake with the stock turbo jet can get you to 31,000 and 1,600 m/s (with the throttle at like 1/10 max) before complete flame out

[Tidus Klein]

I also had an issue with it but then I found perfect guide on this forum. I don't have his name but I copied it to my notes, hope it helps:

===

Flying it is very simple, just climb fast to 10-15km then level out, kill most of your vertical speed and gain velocity as high as possible. Climb slowly from 15k, preferrably within 10 degrees over the horizon, so that you can push the plane to the fastest possible speed without losing air. As you go faster, you get more air intake, allowing yourself to climb even higher without flameouts, allowing yourself to speed up more due to lesser drag. When air intake gets into 15-10% area, cut the throttle of the engine to 75% and continue to climb, that will cut air intake requirements significantly and will delay the flameout further. Cut the throttle further just before the switch if you can sustain the vertical speed with it. Also, don't forget to watch your prograde vector on the navball and pitch upwards: at high altitudes, nothing ever flies horizontally oriented as there is too little air to hold you. If you want to fly horizontally, find an angle of attack that will keep you there, which will be noticeably higher than horizon. When I'm saying "climb within 10 degrees" , that's your prograde marker, not your spaceplane orientation, which could be 30 degrees up even.

Ideally you should be going no slower than 1200-1500m/s and no lower than 25km at the point of switching to oxidizer. Return to full throttle upon switching to it, keep going almost horizontally while stabilizing yourself with RCS. It's best not to burn upwards, keep burning almost horizontally, maybe 20 degrees upwards if you insist on reducing little drag that is left at this point even faster. Getting extremely long trajectory to AP is better than getting up there with a steep trajectory as it will be a lot easier to circularize when you already have most of the orbital velocity needed. Ideally, you will only need a quite short push at AP to raise your PE over the surface and into low orbit.

===

I to will save this, this is gold, that helps alot! I was going full throttle till 21,000 then vertical climb with rockets.

now all I need is the average TWR

If you all want to know what this is for, and a look at my first look here! http://forum.kerbalspaceprogram.com/showthread.php/38527-H-S-S-T-M-C-P-%28huge-single-stage-to-mun-cargo-plane-%29-AKA-operation-Space-whale

Edited July 10, 2013 by Tidus Klein

[Hippaforalkus]

I have been experimenting with SSTO spaceplanes for quite some time, and I have built a number of highly successful ones. There are two basic types: Pure rocket SSTO's, and hybrid jet/rocket SSTO's. In both cases, Mechjeb helps a lot.

I assume that you're trying to build a hybrid jet/rocket spaceplane. I have built such a spaceplane with a jet TWR of only 2.40, and a rocket TWR of only 1.07, and it flies like a dream. In theory, I could probably go lower and still get to orbit. Your spaceplane has extra TWR, which is always a good position to be in.

Jet engines are like SRB's, except they have controllable thrust and wickedly awesome specific impulse. The specific impulse is so amazingly high, in almost all cases, you need not worry about 'wasting' fuel with an inefficient ascent trajectory in the low atmosphere.

Recommended ascent trajectory:

To 8 Km - 10-20 degree ascent (If you are really hardcore and need to save jet fuel for some reason, fly it like a rocket at 70-80 degree ascent)

To 12 Km - Level out ascent slowly, to ~5 degree ascent. Make absolutely sure your green velocity indicator is near the horizon, but just slightly ascending.

To 20 Km - Maintain ~5 degree ascent and build crazy velocity.

To 25 Km - Begin shutting down your outermost jet engines to prevent asymmetric flameout. VERY carefully begin climbing again. Use the Mechjeb ascent guidance to slowly raise the nose of your aircraft. Do not fly manually. If you pitch up too violently, your aircraft will spin and likely fly apart. Try and go for 10-15 degree ascent.

To 35 Km - Your velocity should be nearing 2 Km/sec. If it is not, you needed to build more velocity from 12-25 Km. Your TWR will drop as you shut off engines; as soon as it drops below 1, fire your rockets. As you exit the (flyable) atmosphere, pitch up to 45 degrees.

In order to go this high on turbojets alone, use a stack bicoupler on the front of every engine assembly, with two ram air intakes per engine. If you can put more on elsewhere, even better.

I generally aim for an apoapsis around 180 Km. If all goes well, your rocket burn to establish apoapsis will last only a few seconds. Another short burn ( <400 Delta-V) as you reach Apoapsis will circularize your orbit, leaving you with thousands of additional delta-V for your exo-orbital mission.

I have not tried putting LV-N Atomic Rocket Motors on an SSTO spaceplane in lieu of ordinary liquid-fuel rockets, but they also have specific impulse analogous to that of jet engines. If you have a large enough spaceplane with a high enough rocket-fire altitude, the amount of fuel you require in order to do things goes WAY down, and the heaviest component of the plane would be the LV-N's.

Another word of advice - use a liquid fuel rocket with thrust-vectoring. Toroidal Aerospike Rockets are really only useful for pure rocket SSTO's, which need good specific impulse on the runway as well as during ascent.