Manuever nodes and vastly different TWR

[xcorps]

Let's say I have a maneuver planned using an engine with a very high TWR, but not enough Dv to complete the burn. The next stage has a very low TWR (like an Ion thruster) and needs to burn several hundred Dv to complete the maneuver.

How should I approach this? Should I just plan the transfer as normal and burn it out, or should I let the orbit become elliptical and then plot a new maneuver?

Mechjeb.

Edited December 22, 2014 by xcorps

[Anquietas314]

If you're going for efficiency, let the orbit become elliptical (assuming the apoapsis isn't 30+ days away) and then make a new node at periapsis to complete the burn. If you're trying to get wherever as quickly as possible, just go straight to the ion engine and finish the burn.

[xcorps]

So burning through with the low TWR won't cause me to miss an injection?

[Anquietas314]

It really depends on where you're trying to go. Interplanetary missions really won't be affected much at all, neither will a trip to Minmus to be honest. Mun on the other hand orbits quickly enough that it could make you require a sizeable correction burn. If you're trying to do an orbital insertion, then you either let yourself go flying back off to deep space, or you use the ion drive.

[LethalDose]

It really depends on where you're trying to go. Interplanetary missions really won't be affected much at all, neither will a trip to Minmus to be honest. Mun on the other hand orbits quickly enough that it could make you require a sizeable correction burn. If you're trying to do an orbital insertion, then you either let yourself go flying back off to deep space, or you use the ion drive.

I think this is frankly your best advice.

The other option would be to transfer fuel from the upper stage to the lower stage. It'll probably reduce the total dV in the vessel, but the improvement in the precision of your burn could offset the losses. Obviously, this only works if both stages run on the same fuel.

[Anquietas314]

The other option would be to transfer fuel from the upper stage to the lower stage. It'll probably reduce the total dV in the vessel, but the improvement in the precision of your burn could offset the losses. Obviously, this only works if both stages run on the same fuel.

xcorps mentioned an ion thruster, so that would suggest it isn't an option.

[xcorps]

Thanks!

(10chars)

[LethalDose]

xcorps mentioned an ion thruster, so that would suggest it isn't an option.

Yes, I read his post, which is why I added the exception.

What he gave was an example, and what I provided was a more general (and potentially more useful) answer. Obviously, this situation occurs in vessels without ion thrusters.