Suppose you are an astronaut forgotten in the middle of nowhere, between our solar system and proxima centauri's. Now, you are out of fuel. I heard that with some kind of movements, someone in free space can actually acquire velocity, i.e. accelerate. Kind of like when you played swing as kid, acquiring more velocity with swinging legs back and forth. My first question is:
What is the maximum acceleration from one such optimal movement?
Then, is there a limit to the attainable speed through repeating such movements frenetically?
Finally, as a bonus, how much time to get back to earth with optimal trajectory?
Sorry for the question list but I think they are linked.
Newtonian as well as curved spacetime answers are appreciated and welcome.