# Naked Science Forum

## Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Petrochemicals on 27/05/2019 08:59:26

Title: Minimum initial velocity to exit the galaxy is what ?
Post by: Petrochemicals on 27/05/2019 08:59:26
Whats the minimum velocity to exit the galaxy ? Given that  gravity assists greatly improve your velocity, and thusly energy, what minimum energy is required to get from your house to free movement beyond the attraction of the galaxy.

We are not talking solar sails nor any other propulsion after your initial velocity is attained.
Title: Re: Minimum initial velocity to exit the galaxy is what ?
Post by: evan_au on 27/05/2019 11:24:46
If you don't care about how long it takes, and you have a very accurate map of the position and velocity of passing stars, you could probably do it with the same velocity as New Horizons.

Of course, it would take many rotations of the galaxy (at about 250 Million years each) to build up enough gravity assists to reach the outer parts of the visible galaxy.

...or you could aim for a stellar stream as it passes through the disk of the galaxy, which would take you out of the disk of the galaxy...

I think you had better develop a fusion drive before you set out on this voyage! You will need it to position your spaceship for the next gravity-assist...
Title: Re: Minimum initial velocity to exit the galaxy is what ?
Post by: Bored chemist on 27/05/2019 11:53:52
Googling "escape velocity milky way" tells me that the escape velocity is 550 km/s.
However, if you use gravity assist then I'm not sure what the minimum start velocity is.
I suspect that you could start off with less than the energy needed to escape the earth, but pick up energy from slingshotting the moon (and earth) enough times to set out for infinity.

From the point of view of a distant observer watching you, this would be interesting.
You would "fall" up out of the gravity well of the milky way.