Rescue a stranded Kerbal

[SpaceFaringOrBust]

First off my name is Stephen. I'm new here and in an emergency of sorts. I did an EVA and ran out of fuel. Now I have to go rescue my guy. How do I figure out the math needed to go rescue him?

Thanks in advance

 

[4x4cheesecake]

Welcome to the forum Stephen

I have a few ideas how to do rescue your Kerbal, but depending on your experience, this is going to be really tough.

First of all, a few things for clarification:

1) Your Kerbal is floating in space, while still on EVA (and no jetpack fuel) or is he inside a ship?
2) Is your Kerbal in a stable orbit?
3) Which celestial body is he orbiting?
4) Do you know how to rendevouz in space?
5) Do you play in career/science or sandbox mode? If you play in career/science mode: do you already unlocked external seats and cargo bays?

[bewing]

Just to rule it out: the Kerbal isn't on the surface of some celestial body?

And the Kerbal has used up every last drop of jetpack fuel? None left at all?

 

[Zhetaan]

14 hours ago, SpaceFaringOrBust said:

First off my name is Stephen. I'm new here and in an emergency of sorts. I did an EVA and ran out of fuel. Now I have to go rescue my guy. How do I figure out the math needed to go rescue him?

First off, welcome to the party, Stephen.

Second, have some of the punch, because this one is going to be tough.

I'm going to assume that you're in space and not on the surface of a celestial body:  if you are on the Mun or Minmus or some other place, then you can walk back to your craft; it can take some time but the jetpack is not necessary.

On the other hand, if you're in space, rescuing your Kerbal is less of a maths-intensive issue and more a matter of fine docking control.  Since you've managed to expend an entire jetpack's worth of fuel, I'll also guess that you have not yet learned the finer points of rendezvous and docking ... which means that most likely, the ship you exited for your EVA is not equipped to perform the rescue.

That's okay; it just means that you have a new mission.  Before you go much farther, it would be a good idea to go into the map view and see whether your Kerbal is going to fall into something's atmosphere.  If so, then it may not be possible to effect a rescue in time, and you may need to accept that.

Otherwise, I'm going to assume the worst case that your Kerbal came out of a single-seat command pod and the ship is now uncontrollable, but that both are in a stable orbit.  That's okay, too:  it means that you can do two rescue missions.  In the meantime, it gives you the time to learn how to complete those missions.

First, I'm going to give you a list of places to look for rendezvous and docking help.  You may need to build new ships in order to work on this--and if you need to do so, there's nothing wrong with starting a new sandbox save so that you don't also have to worry about funding your own training.

1. Scott Manley's 2014 Docking and Rendezvous Video
2. Orb8ter's 2017 (version 1.2) Rendezvous and Docking Tutorial Video
3. Lithobreaking Works's 2018 Rendezvous and Docking Tutorial Video

These are all YouTube videos; text-based tutorials (of varying age) are in the Tutorials sub-forum.  I am personally fond of tutorial campaign written by @Pecan called Exploring the System that was made for version 0.90, so it goes back quite a ways.  While I don't think the ascent vehicles in that campaign will work anymore, the docking trainers are a good design if you want to learn how to do it--and you will want to learn how to do it.

Once you understand the ideas behind rendezvous, docking, and fine manoeuvring in orbital space (this may take some time), you're ready for the more difficult part:  you need to learn how to dock with something that has no ability to control its own motion.

There are two ways to accomplish this.  The less desirable by far is to use a Klaw:  it will absolutely grab a Kerbal.  However, it will not put the Kerbal back inside the spacecraft, which means that rescue needs to include provisions to protect that Kerbal from re-entry.

The second is to try an unpowered docking procedure, with the caveat that rather than bringing a docking port to the Kerbal, you bring a ladder instead.  This requires extremely careful and slow motion, a rescue ship that is preferably perfectly balanced, and you will need to switch to the Kerbal while on final approach in order to use the Grab command when the ladder comes within reach of it.

It also requires a specially-designed rescue ship that either includes a probe core or two seats (make certain that one of them is empty!), RCS and monopropellant, and ideally as compact a design as possible so that you don't waste time trying to turn the long dimension about.

Aside from the fact that you won't have docking ports, rescuing the Kerbal is about as straightforward as regular rendezvous, aside from the aforementioned requirement to switch to the Kerbal while you approach so that you can use the Grab command.  After that, if you like, you can move to the abandoned spacecraft and rescue it, too.

 

I know I'm short on details, but I really can't provide more than a general procedure until and unless I can find out more about your specific circumstances.

Good luck!

[SpaceFaringOrBust]

20 hours ago, Zhetaan said:

I know I'm short on details, but I really can't provide more than a general procedure until and unless I can find out more about your specific circumstances.

Good luck!

 

You were nowhere near short on details. Thank you

Unfortunately, my kerbal was lost to Kerbin's atmosphere. He had too much of a retrograde orbit and after a few dozen orbits he entered the atmosphere.

Thank you for everyone's help. 

I believe I have become addicted to this game though. Makes sense though, I am currently in school to become an aerospace engineer.

[Aeroboi]

The math? You don't need any math for this mate.

While I'm sure you are already aware, Kerbals like ships are treated as vessels and can be targeted as a vessel in the map view.
That means that you can use a maneuver node to rendezvous with that Kerbal.

Pack some monopropellant and rcs in your rescue vessel and park next to the kerbal. Use the rescue ships rcs to rotate and translate so that the cockpit door is just in front of the Kerbals nose. If done properly you should be able to grab the ladder and get onboard.
Of course make sure there are 2 seats on the vessel. This is rudimental but you gonna be liquided if you forget this bit so I'm just saying.