bi-elliptic transfer to GKO

[codepoet]

Does anyone have experience of using a bi-ellptic transfer to get into GKO. In theory it shoiuld be more efficent that a Hohmann transfer, but I have not yet done the maths to see if it is worth the effort. Presumably it is really hard to get the timing right.

[Kasuha]

Bi-elliptic transfer is only worthwhile when semimajor axis of the target orbit is at least 12 times larger or smaller than the starting orbit's and still the saved delta-v is only marginal. There's no problem with timing. You raise your apoapsis as high as you are willing to go (because it takes time), brake/accelerate at that apoapsis to get the periapsis to the required height, then brake at periapsis to get apoapsis back to where you need it.

Theoretical optimum is so-called biparabolic transfer, where you raise your apoapsis just to the escape velocity, then go to the apoapsis at infinity, there perform burn of 0 dv to adjust the periapsis, and after returning from infinity to the periapsis brake again to adjust the apoapsis. The only downside of biparabolic transfer is that it takes infinite time.

[Wahgineer]

^ In layman's terms:

Your probably better off going with just the hohmann transfer (faster, easier to comprehend, less burns/maneuvers, etc). Or even better, launching into a suborbital trajectory, circularize your orbit, but don't stop burning, keep going until Apoapsis is at GKO, ride to Ap (or just before it), than circularize. Done, and in less time and with less maneuvers than the standard get-orbit-then-boost and/or bi-elliptic.

[Kasuha]

What's GKO anyway? GeoKerbal Orbit?

[capi3101]

If you're going for a geosynchronous orbit around Kerbin, use a Hohmann transfer. Apoapsis or periapsis doesn't matter - just pick one.

Right now I'm going for a heliosynchronous orbit as part of the Constellation Program Challenge and I'm using a bi-elliptic transfer. So far it's used maybe 2,500 m/s of delta-V (with the bulk of that needed to boost the probe's apoapsis up to Jool's orbit, the rest of it to lower the periapsis to the target zone). Haven't done the third burn yet, so I couldn't tell you if there will ultimately any delta-V savings or not.

I'm like Kashua; not sure which target you're talking about here.

[Traches]

Pretty much the only time it's worth doing a bi-elliptic transfer from kerbin is when you're going for a low orbit around the sun. Nothing else is far enough away.

Edited November 21, 2013 by Traches
i spel gud

[Xaiier]

Bi-elliptic transfer is only worthwhile when semimajor axis of the target orbit is at least 12 times larger or smaller than the starting orbit's and still the saved delta-v is only marginal. There's no problem with timing. You raise your apoapsis as high as you are willing to go (because it takes time), brake/accelerate at that apoapsis to get the periapsis to the required height, then brake at periapsis to get apoapsis back to where you need it.

Theoretical optimum is so-called biparabolic transfer, where you raise your apoapsis just to the escape velocity, then go to the apoapsis at infinity, there perform burn of 0 dv to adjust the periapsis, and after returning from infinity to the periapsis brake again to adjust the apoapsis. The only downside of biparabolic transfer is that it takes infinite time.

Dear Squad, please add an ∞X time acceleration so that we can play with relativistic concepts.