stationary moon orbit up-down travel

[ximrm]

Let's say I have a stationary station in orbit(~2.9k km after wiki) and a mün-base directly below.

It should theoretically possible to just directly thrust into the sky and rendez-vous with the station.

It would make transfers a lot easier,without having to establish a phasing orbit etc. to eventually meet up with the station.

Or are there (m)any problems I did not think off?

Edited May 26, 2014 by ximrm

[kidolvski]

When you take off heading straight up, with your crew transfer vehicle, your orbital speed is not high enough to sustain an orbit around the Mün. Thats why people make gravity turns when taking of, with the purpose of achieving an orbit. The station is moving with enough orbital velocity to sustain an orbit. Therefore the relative orbital velocity between the transfer vehicle and the station, is the velocity that the station is travelling at, that is why it is not possible to burn straight up and dock.

That is what I mean.

Edited May 26, 2014 by kidolvski

[Laie]

You can't go stright up, because the Mun's rotation is moving you sideways. When trying to go straight up, you take that sideways motion with you. You will end up with an very eccentric orbit that slams back into the Mun a little east of your starting point.

You can plan an encounter with your station by goint "straight up", but that encounter will be a violent one. If you want to dock, you need to a) get to the right altitude and match the velocity of your station. The latter requires you to turn your eccentric orbit into a circular one, by adding a lot of eastward delta-V.

TL;DR: there are no straight lines in space.

[kidolvski]

If you made a huge elevator going up from your base to your station, just imagine it, you could, because the "cable" to which the elevator is connected would give you the needed orbital velocity. But I think that is very hard, if not impossible.

[Red Iron Crown]

Synchronous orbit around the Mun is not possible anyway; due to its slow rotation the orbit would have to be outside its SOI.

[ximrm]

Thank you for your wisdom.

[Tex_NL]

kidolvski, Laie and Red Iron Crown are correct in this not being possible. Straight up and down won't work and Mun has no stationary orbit.

But the idea itself is a valid one. If you place a station in a synchronous orbit at the correct angle, for example around Kerbin, you would be able to launch any time of day and end up right on its doorstep after you circularize your orbit.

[Kasuha]

You can have a station "levitating" above single point of Mun surface if you place it right outside Mun SOI on the Mun's orbit around Kerbin.

And yes you can then get to it by launching vertically, though there will still be some lateral velocity to kill.

Note it's a bit of cheat on game physics and the distance is large. Note also that going straight up uses more fuel than going in orbit first and then doing Hohmann transfer.

This does not work for most normal stationary orbits. Surface velocity is usually way smaller than orbital velocity in stable orbit so you have some catching up to do.