Spaceplane Apoapsis

[Agent]

I\'m new with KSP, so I haven\'t had much time to play around with the space planes. However, whenever I start leaving the atmosphere I know I have to raise the apoapsis (I think) so that it will create a circle around Kerbin. I remember from a video that to do this, at the right moment I need to start a steep climb upwards and it will work. When I do this it doesn\'t move. Any help would be appreciated.

[Dekker3D]

A space plane generally uses wings for lift and has more efficient, atmospheric-only engines. As you go higher, the atmosphere thins out. To achieve a true orbit, you\'ll -want- to be out of the atmosphere because otherwise it\'ll just slow your craft down and decay its orbit again, but a spaceplane generally can\'t manouver above the atmosphere.

To get an orbit with your spaceplane, put some traditional rocket engines on it.

[vexx32]

If you\'re going with atmospheric engines, they\'ll conk out at about 20km or a bit less. From there on, you have to use rocket engines to get you out of the atmosphere entirely.

[Agent]

Thanks for your help guys. I added a couple of rocket engines and it helped me make the orbit a bit bigger. However, I can\'t figure out why it happens that whenever my orbit is getting bigger and bigger at one point it just suddenly stops increasing and I end up reaching the apoapsis and I\'m screwed at that point. Any solutions for that?

[dogon11]

Thanks for your help guys. I added a couple of rocket engines and it helped me make the orbit a bit bigger. However, I can\'t figure out why it happens that whenever my orbit is getting bigger and bigger at one point it just suddenly stops increasing and I end up reaching the apoapsis and I\'m screwed at that point. Any solutions for that?

Possibly more fuel.

[Agent]

Possibly more fuel.

I don\'t think that\'s it. I loaded my plane up with 4 tanks of liquid fuel so I think that\'s sufficient.

[Vanamonde]

I\'m not exactly sure what your issue is, but are you aware that when changing orbit, you can\'t change your current altitude from where you are now; you can only change your future altitude from where you are now? In my little diagram the planet is the green blob and your ship is leaving the atmosphere at point A on the red path. No matter how much fuel you burn at point A, your orbit will always come back around to that low point at A. (Experts on this stuff: I know I\'m cutting corners on the explanation, but I\'m trying to keep it simple and clear.) Burning fuel at A does, however, raise the altitude of point B. Later when you get to point B, again you can\'t change its altitude from there, but burning fuel there will raise the altitude of point A, putting you on the yellow path. So reaching orbit always requires 2 burns: one to reach altitude, and one to keep you at that height.

If this isn\'t your issue, sorry if I sound like a know-it-all. I just like helping nice people on these boards when I can. Maybe you could post a screen shot of the map view of your flight?

[Agent]

Alright I attached a couple of pics to help clear it up.

In the first pic that\'s the point at which I begin to burn at a more steep angle to cause the orbit trajectory to go all the way around Kerbin.

In the second pic that\'s the point at which I fire up the engines near the apoapsis but it won\'t move at all.

[Guest butt head]

BWAHHAAHAHAHA you are trying to get a STABLE ORBIT IN THE ATMOSPHERE, LOW ATMOSPHERE TO ;P to get in to thin atmosphere you should get above 40k and out of atmosphere above 70k you need to get above 70k to get an orbit no mater what cus if your in the atmosphere then the air will slow you down wings or not

BIGGEST FAIL EVER.

[Vanamonde]

What are your altitude and attitude in the second picture? If you\'re still too low and/or trying to plow ahead rather than up, air resistence will be countering your thrust, you won\'t build up to orbital speed, and you\'re basically still just flying like an airplane, and that can\'t ever get out of atmo. (Which is basically what butt head just said, minus the gloating.)

I got a SSTO splaceplane to reach orbit (but not to land without blowing up ) by climbing to 6000m on jets, then standing it on its tail and transitioning to the liquid fuels. It was really just like flying a normal rocket ascent from there, except you get a headstart on speed and altitude. If you\'re not able to raise that apoapsis while climbing at 80 degrees or so, then I think the problem is not your flight plan, but the thrust/weight ratio of your ship while in rocket mode.

Hope this helps.

[vexx32]

Well, make sure the engines are oriented so that they\'re applying thrust along the direction of movement (basically, you want your engines to be pointing behind you if your ship is pointing where you are going).

It may be that the engines are not quite powerful enough to get you into a full orbit by burning only to get out of atmosphere and at apoapsis, if so just continue to make path corrections and don\'t cut the engines on the ascent to try and get a bit extra height.

The apoapsis won\'t move at all itself, what will happen is the orbit will slowly widen until the Periapsis appears on the other side of Kerbin.

[Endeavour]

If you use both jets and rockets, fly at around 30 above the horizon. When you are at around 14km, kick on the rockets and pitch up to 45 degrees. Shut off the jets at 20km. I would recommend using fuel lines to connect the fuel for the jets to the fuel for the rockets to get everything out of your spaceplane. Don\'t stop burning until you apoapsis is above 70km. Then wait until you are at the apoapsis and burn prograde until you are circular.

[dogon11]

I don\'t think that\'s it. I loaded my plane up with 4 tanks of liquid fuel so I think that\'s sufficient.

Which fuel? The airplane fuel, or the rocket uel?