Delta-v required to return from Mun

[MrSpaceCarrot]

The I'm Screwed. I landed with 736mps of delta-v and now i'm stuck i think. Or is it possible to get back with less?

[Snark]

Hello, and welcome to the forums! 

I've taken the liberty of splitting your post into a thread of its own, since the last one was pretty old.

19 hours ago, MrSpaceCarrot said:

The I'm Screwed. I landed with 736mps of delta-v and now i'm stuck i think. Or is it possible to get back with less?

No, that's not enough.  But there are options.

First, you do have enough to get into orbit around the Mun, so that's a good start.

Once you get to that point, you have a few possibilities.

One would be to send a rescue mission.  Send another ship that has an empty crew slot, which can rendezvous with your stranded ship in Mun orbit.  Then transfer the kerbal across and head home.

Another option would be to get out and push, i.e. use your kerbal's EVA thrusters to shove the ship in the right direction, and go back into the crew pod every time your EVA fuel gets low, so you have a refill.  Keep doing that and you can pick up a few hundred m/s of dV (slow and tedious, though).

Yet a third option would be to send the kerbal EVA, use their 600 m/s (!!!) of EVA propellant to take the kerbal to low Kerbin orbit, and rescue them there.

 

[Foxster]

Kerbals are biological rocket parts and just as disposable. 

[MrSpaceCarrot]

Thanks for the advice!!!!

I think i have a solution. I have a lander about 10 kms away from the rocket, (which btw is a prebuild stock "Munsplorer") and it has 3 crew slots.

What I did:

fly the munsplorer 5 kms closer then EVA jetpack the rest. so I got to the lander.

Now I have a rocket in orbit with more than enough fuel to get back to kerbin. All I need to do now is rendezvous. the problem is I've never done a successful one. For me they usually end in catastrophe and explosions (or just huge misses)

Also I wasted nearly all those 736mps of delta-v on the moving the munsplorer so no fuel left in that

Edited January 30, 2019 by MrSpaceCarrot

[Espatie]

Right, orbital rendezvous are somewhat tricky to learn, but not actually hard to do once you have the knack of it.

Firstly: is your current ascent vehicle directly or nearly underneath the orbit vehicles orbital path? If so, wait until it's almost overhead, and then launch directly into its orbit (same heading etc - use target in map view to find the orbital angle).

 

From there you're in a good position to follow one of the many tutorials on doing a rendezvous.

[Loren Pechtel]

How does the get out and push bit work, anyway?  In my experience the Kerbal's jetpack turns off when you try it.

And while a Kerbal's jetpack is capable of putting them on a return trajectory from Mun orbit it's not capable of circularizing once it's there, no picking them up from low Kerbin orbit unless you do a careful aerobrake (no heat shield and he's going to hit at 3000 m/s, considerable caution is advised!)

[Superfluous J]

24 minutes ago, Loren Pechtel said:

How does the get out and push bit work, anyway?  In my experience the Kerbal's jetpack turns off when you try it.

And while a Kerbal's jetpack is capable of putting them on a return trajectory from Mun orbit it's not capable of circularizing once it's there, no picking them up from low Kerbin orbit unless you do a careful aerobrake (no heat shield and he's going to hit at 3000 m/s, considerable caution is advised!)

You're missing the "push" part.

You get out of the capsule and push it. Forward at Pe to escape a body, backward at Ap to intersect an atmosphere.

It's really only good for those last few (dozen/hundred/depending on your patience and time frame) m/s when you run out of gas. You're not going to conduct a space program with it, just not have to do the occasional rescue mission.

Your first sentence says when you do push, the jetpack turns off? I've never experienced this and wonder if you're misreading the fact that you don't really change the trajectory that much. Space ships are much bigger than Kerbals so you have to push more. If the ship is 10x the mass of the Kerbal, you need to thrust 10x as long to get the same effect.

Edited January 31, 2019 by 5thHorseman

[bewing]

23 minutes ago, Loren Pechtel said:

How does the get out and push bit work, anyway?  In my experience the Kerbal's jetpack turns off when you try it.

You can't do it from a ladder. You line up the craft prograde and then bump yourself against the engine bell until you slide off. It doesn't work very well.

23 minutes ago, Loren Pechtel said:

And while a Kerbal's jetpack is capable of putting them on a return trajectory from Mun orbit it's not capable of circularizing once it's there, no picking them up from low Kerbin orbit unless you do a careful aerobrake (no heat shield and he's going to hit at 3000 m/s, considerable caution is advised!)

You don't circularize. You just lower your Ap enough to make a rendezvous practical.

 

[Loren Pechtel]

16 hours ago, bewing said:

You can't do it from a ladder. You line up the craft prograde and then bump yourself against the engine bell until you slide off. It doesn't work very well.

You don't circularize. You just lower your Ap enough to make a rendezvous practical.

 

I haven't tried it with an engine bell, just against the rear of the capsule (I had already dropped the empty booster so there would be a minimum weight to try to push.)  It didn't work.  It's been a long time since I've tried it, though.