General Question Setting planet approach up for return

[Tomato3017]

Hello,

I've been gradually adding difficulty to each travel that I make in Orbiter. I know alot about orbiter and orbital mechanics that I didn't know months ago. I know how to travel to planets, do all the crazy aero stuff(other then aeroslinging) and stuff like that. I tend to use transx for plotting my trajectory to a planet then use IMFD's planet approach upon arriving.

Now that I told you where I am in terms of technicality, on to my question.

I always end up running out of fuel at the target planet while trying to align my plane(which is always way off) for a return trip. Is there any good way/best practice for aligning yourself on a planet approach for a return trip at the next launch window? I know transx works good for stuff like that but i'm still trying to grasp it and haven't been able to get slingshots and approaches to work that well yet.

Thanks in advance!

 

[Tommy]

I'm not aware of any way to do this with IMFD. If you are visiting a planet with an atmosphere, it may be possible to save wuite a bit of fuel using an aerodynamic plane change.

To do that, set Align planes to the Inc and LAN of the plane needed for the return. Then the goal is to bring the TTh down so that it reaches zero at the same time as TN does. If TN stops dropping, or begins to increase, it means you are turning to fast, and will come up "short". Of course you'll need some fuel to re-establish your orbit, but that can often be less than a traditional plane change can cost for PLC's larger than 10 to 15 degrees. This works very well on Mars. The thin atmo makes it a bit harder to turn, but you'll lose less speed than you would on Earth, and the lower orbital velocity for Mars means less fuel spent "rebuilding" your orbit.

Another way to save fuel is to figure out where your eject point will be, and burn Prograde there. raise your PeA as high as you want - but don't escape the planet. Then make your plane change at the node nearest your Ap, you'll be traveling much slower and will use quite a bit less fuel. Also, the velocity you gained doing this will be that much less velocity you need for the ejection, so there's no loss in raiseng the Ap if done correctly.

 

[Tomato3017]

I'm not aware of any way to do this with IMFD. If you are visiting a planet with an atmosphere, it may be possible to save wuite a bit of fuel using an aerodynamic plane change.

To do that, set Align planes to the Inc and LAN of the plane needed for the return. Then the goal is to bring the TTh down so that it reaches zero at the same time as TN does. If TN stops dropping, or begins to increase, it means you are turning to fast, and will come up "short". Of course you'll need some fuel to re-establish your orbit, but that can often be less than a traditional plane change can cost for PLC's larger than 10 to 15 degrees. This works very well on Mars. The thin atmo makes it a bit harder to turn, but you'll lose less speed than you would on Earth, and the lower orbital velocity for Mars means less fuel spent "rebuilding" your orbit.

Another way to save fuel is to figure out where your eject point will be, and burn Prograde there. raise your PeA as high as you want - but don't escape the planet. Then make your plane change at the node nearest your Ap, you'll be traveling much slower and will use quite a bit less fuel. Also, the velocity you gained doing this will be that much less velocity you need for the ejection, so there's no loss in raiseng the Ap if done correctly.

I have done that with the DGIV and the XR1 before. My problem is that i'm using the Perseus which is very hard to do aero plane changes with. That is why i'm wondering how to plan ahead so a much smaller plane change is required, if any.