Question about Real Life Orbit vs. KSP Orbit??

[VincentMcConnell]

So if you watch the old Apollo videos or even the modern Shuttle ones, the launch begins and the engines don\'t shut down until the craft is in orbit. They keep burning and burning and when they shut down, BAM, orbit. In Kerbal, I always pitch over and continue burning until my Apokee is at my desired altitude, shut the engines down, wait until I reach it and then burn again, which puts me into orbit. This isn\'t how they do it in real life, I don\'t think...

Is there any way in Kerbal to launch and continue throttle until in near perfect orbit?

[NovaSilisko]

Actually, all of them had to do what we do - a circularisation burn after MECO. Although, I don\'t think the real ones are quite so drastic (not from a suborbital trajectory)

It\'s just a matter of timing your gravity turn so you end up horizontal as soon as you reach apoapsis, then continue burning until you reach a proper orbit.

[VincentMcConnell]

Actually, all of them had to do what we do - a circularisation burn after MECO. Although, I don\'t think the real ones are quite so drastic (not from a suborbital trajectory)

It\'s just a matter of timing your gravity turn so you end up horizontal as soon as you reach apoapsis, then continue burning until you reach a proper orbit.

Yeah, orbit is no problem at all for me anymore. I can get orbits within about 30 meters and the only reason I can\'t get closer is because the AP and PE shake around like crazy and make it hard to know when I have to use the RCS. I will try to devise a way to get into orbit on only one burn and then do the circularization once in Orbit.

[Kosmo-not]

Yeah, orbit is no problem at all for me anymore. I can get orbits within about 30 meters and the only reason I can\'t get closer is because the AP and PE shake around like crazy and make it hard to know when I have to use the RCS. I will try to devise a way to get into orbit on only one burn and then do the circularization once in Orbit.

What you want to do in that case is to either back off on the thrust (which I don\'t think is what you had in mind) or, with a higher apoapsis than your planned orbit altitude, pitch down below the horizon when you get to your orbit altitude to change your velocity direction vector onto the horizon.

*edit*

If you want a cool stock parts space shuttle experience, check out my Deimos II craft.

[VincentMcConnell]

What you want to do in that case is to either back off on the thrust (which I don\'t think is what you had in mind) or, with a higher apoapsis than your planned orbit altitude, pitch down below the horizon when you get to your orbit altitude to change your velocity direction vector onto the horizon.

*edit*

If you want a cool stock parts space shuttle experience, check out my Deimos II craft.

Rog. Giving it a test run now. Standby 1.

EDIT -

I did have some issues rolling it. I\'d disengage SAS to roll and the whole thing would pitch like crazy. I\'m adding some more powerful RCS but it doesn\'t seem to be a problem I can fix. It\'s preventing me from getting into orbit. I\'ll be working on it. Yep. This spacecraft can\'t execute rolls... Do you have any solutions?

[PakledHostage]

Something to keep in mind as well is that typical orbital speeds for Earth are on the order of 7500 m/s, while they\'re on the order of 2200 m/s for Kerbin (give or take). You need to fly a much more efficient trajectory to get into Earth orbit because real rockets have a lot less margin than our typical Kerbal rockets.

[softweir]

There are techniques for doing a burn-to-orbit launch, but they require very precisely pre-calculated flightpaths that are beyond us. So we make best use of our easy Kerbal universe with its tiny planet, and use a rule-of-thumb technique that wouldn\'t really work in the real world.

There are advantages to burn-to-orbit flightpaths. As PakledHostage said, they are the most fuel efficient. Another advantage is that they allow you to build your first-stage motors so that they can\'t be re-ignited after launch.

[Kosmo-not]

Rog. Giving it a test run now. Standby 1.

EDIT -

I did have some issues rolling it. I\'d disengage SAS to roll and the whole thing would pitch like crazy. I\'m adding some more powerful RCS but it doesn\'t seem to be a problem I can fix. It\'s preventing me from getting into orbit. I\'ll be working on it. Yep. This spacecraft can\'t execute rolls... Do you have any solutions?

I have just posted the Deimos II in the spacecraft exchange forum. You\'ll find some flight tips there.

Something to keep in mind as well is that typical orbital speeds for Earth are on the order of 7500 m/s, while they\'re on the order of 2200 m/s for Kerbin (give or take). You need to fly a much more efficient trajectory to get into Earth orbit because real rockets have a lot less margin than our typical Kerbal rockets.

Another interesting thing I have encountered is the delta-V loss getting to orbit. On Kerbin, it seems to be just over 50%, while on Earth it\'s around 20%.

[CobraA1]

Do you mean making any type of orbit, or a certain desired orbit?

I can certainly make an orbit in a single burn. It won\'t be pretty and it won\'t be up to any sort of specifications, but it\'s functional.

What I do is to turn my craft towards the horizon once I leave the atmosphere. Keep it burning long enough and keep it pointed at the horizon, and you\'ll make orbit. I don\'t even use RCS.

If you\'re talking about a certain desired orbit, then what\'s usually done is that NASA pre-computes the desired flight path via computers, and everything is planned ahead of time.

I suppose if you do it right and learn how to make corrections with the engines burning, you could get a certain orbit, but it may be tricky.

I\'ve attached an image (and the file) of my craft to this post. It\'s a stock parts craft that can make it to the Mun (and I made my first Mun landing today! Yay! And I got back safely too ), and it can also make a single burn orbit. Not a very good orbit, but good enough for a Mun mission.

[LambdaCactus]

I\'ve done this. The trick is to build more horizontal speed early, then reduce thrust as you approach your orbital altitude.

What I do:

[list type=decimal]

[li]Slowly start pitch-over at 10-15km, depending on the ship\'s speed and stability.[/li]

[li]Maintain a slow pitch-over, your thrust vector ('nose') should follow your prograde marker as it falls over toward the horizon. You\'ll want to time it so you\'re pretty much horizontal around 50-60km. You can aim higher, it depends how high you want to establish your orbit. Just remember you will keep burning and climb up to it by building horizontal velocity.[/li]

[li]When approaching horizontal attitude, reduce thrust so you\'re just pushing the Apoapsis ahead of you, perhaps gaining on it slowly, but not pushing it any further away.[/li]

[li]Keep adjusting your attitude to point at the horizon. Keep low thrust. As long as you keep apoapsis slightly ahead of you, you will be climbing. If you have a longer way to climb, you can push apoapsis further ahead: just don\'t let it get too far away from you, or you\'ll get too elliptical, and that means cuttiing the engines for a while.[/li]

[li]The trick to finish it off is to reduce thrust so you approach and hit apoapsis at your target altitude with zero thrust. Since you\'ve been burning horizontally the whole time and slowly gaining orbital speed, it should be pretty much circular when you get there. Check your periapsis and add a little burn if necessary.[/li]