Can I abandon my Kerbonaut in space?

My little Kerbonaut is currently circling the planet in a stable orbit, and seems to be having a grand ol' time with it. You should see the smile on his face. He's been circling now for what looks like 5 days, and is still smiling. Poor little guy doesn't know what I have in store for him.

I could bring him down. I mean, he does have some science for me that I need for the next upgrade, but that doesn't sound like as much fun. I'm pretty proud of the little guy for making orbit. Can I just leave him up there forever, or will he eventually die of starvation or something? And if I do leave him up there, and decide to one day retrieve him (dead or alive) can I dock with that and extract him and (more importantly) my science from the ship, even though it doesn't have any docking equipment?

Currently, resources such as oxygen, food, or other things necessary to sustain Kerbal life have not been implemented (except through mods). He won't even die of old age. Since you are in a stable orbit, your Kerbal is effectively immortal, so long as you don't touch him or his ship.

Getting him back will be a bit trickier; to get the science he has, you have to either transmit it (and lose some in the process), or land the ship in a survivable manner. If you just want the Kerbal himself back, landing will also work for that. You can also get another ship close by with extra room, and then EVA your Kerbonaut into the other ship. Even with docking, you can't transfer Kerbals, so to get him and leave the ship alone, EVA is your only option.

Just to note: docking is a whole other ball of wax. The easier way by far is to just land the ship.

Kerbals are currently immune to the ravages of:

• Hunger
• Thirst
• Intense G-Forces
• Boredom
• Spacesuit Rupture
• Sleep Deprivation
• Loneliness
• Catastrophic Bladder Malfunction

So, in short, you can leave him orbiting indefinitely. For science. You monster.

As to retriving him "eventually", you won't be able to dock if the ship doesn't have anything to dock with, but you might be able to get another ship close enough that your little kerbal can EVA over and enter the new ship.

When Asteroid Redirect Mission update will see the light, you will be able to dock. Kinda. You would need to grab that ship like you would grab an asteroid.

See forum post by Rowsdower, Kommunity Manager:

What is this Claw thing?

The Advanced Grappling Device, or “claw”, is your primary means of capturing an asteroid. The Claw works very much like a docking port, however, it doesn’t require a mate node to dock to. That means it can grab on to almost any object. Once grabbed on, you can even transfer fuel from the grabbed objects (provided they have any).

So, if your "eventually" will be long enough, you will be able to dock.