Getting the proper orbits - Need help!

[Sakai]

Hello!

I need help from you clever people! >.< I always have a problem when it comes to making a perfect orbit on kerbin from whenever I start off from the Launch Pad. I watched few videos on it but I still fail to slightly understand.

When am I suppose to tilt my spacecraft to what degree on the NavBall? What apoapsis and periapsis size is there suppose to be to make a perfect or at least GOOD orbit so I don't need to waste more fuel for extra fixing (that takes a lot of time for me) to make the orbit a proper orbit?

Thank you!

Edited October 30, 2014 by Sakai

[Jeff Bird]

Hello Sakai,

They easy way to get in to orbit is, straight up until 10,000m trying not to go faster than 250m/s, at 10,000m throttle up and slowly tilt over to 45 degrees, when the AP gets to 100km cut the engine, wait a moment, then make a node to circularize as best you can.

Edited October 30, 2014 by Jeff Bird

[Starman4308]

Hello!

I need help from you clever people! >.< I always have a problem when it comes to making a perfect orbit on kerbin from whenever I start off from the Launch Pad. I watched few videos on it but I still fail to slightly understand.

When am I suppose to tilt my spacecraft to what degree on the NavBall? What apoapsis and periapsis size is there suppose to be to make a perfect or at least GOOD orbit so I don't need to waste more fuel for extra fixing (that takes a lot of time for me) to make the orbit a proper orbit?

Thank you!

The orbit you should be trying to get to during ascent is Low Kerbin Orbit (LKO): which is roughly 70-90km apoapsis and periapsis. For most purposes, the lower, the better. Once you're in a parking orbit in LKO, you can go anywhere, and courtesy of the Oberth effect, it is often most efficient to start from the tightest orbit you can manage.

In order to get there, just pull a gravity turn (a simplistic one is to turn 45 degrees at 10 km; for more sophisticated turns, you might try watching how MechJeb does it), cut your engines you get apoapsis to ~75-80 km*, and make a maneuver node at apoapsis to circularize. It doesn't matter if your periapsis is inside Kerbin during ascent: you will bring that up when you reach apoapsis.

*If you're still deep in the soup, you might want to fire a bit more to account for loss of speed to atmospheric drag. Also, the higher the apoapsis, the more forgiving the process is for time to make and execute the node, plus the less chance you might accidentally dip back in the soup during the process.

Edited October 30, 2014 by Starman4308

[Scarecrow88]

The general rule of thumb seems to be that you need to do your gravity turn at 10,000m until your ship is tilted over 45 degrees i.e. half way between straight up and pointing at the horizon. Depending on your ship and it's rate of acceleration, you can either stay at this attitude until your apoapsis reaches the desired altitude, at which point you can cut your engines, coast up to apo, and then do your circularisation burn. For a slower accelerating ship, the alternative would be that if your apo isn't at the required altitude by the time your ship reaches 40,000m, turn a bit more so that your nose is 20 degrees above the horizon. This has the advantage of still pushing your apo up, but also increasing your horizontal speed more.

There is no best apo or peri for a perfect orbit, as the orbit height will be dependant on what your aims are for that particular flight, other than both need to be above 70,000m.

[Sakai]

Thank you everyone! that answered my question! ^^.

[xtoro]

Nobody mentioned that it's standard procedure to tilt towards the east.

[capi3101]

I fly a little differently; I still do my gravity turn - 45 degrees on 090 at 10,000 meters - but what I do is watch my time to apoapsis after that point. Once it gets to 45 seconds I start tilting more towards the horizon, and I try to keep it right there at 45 seconds for as long as I can. I usually at some point wind up flying horizontal - this has the benefit of raising my periapsis while I'm still in the ascent (i.e. both are going up simultaneously). What happens is that when you do finally call MECO and coast on up into space, your periapsis is already around 25-30k, which means the circularization burn generally takes less than 100 m/s of delta-V; I have on occasion had a circularization burn of less than 10 m/s.