Newton's laws say that the momentum that goes out the
back, and the fuel here times the velocity of the fuel.
Balances the mass that goes forward, and the velocity out.
And in order to move something, very fast this way,
you've gotta send a lot of stuff out the back.
This is why when you look at a rocket, and here's a model, of,
NASA's next new big rocket, the space launch system, you
have, a lot of rocket and exhaust, and
relatively little material sent out into space.
This balance could be understood, by the fact that it takes a
lot of momentum going this way, to move a rocket fast this way.
If you want
V here to be big, keep these in balance.
This mass that goes out, has to be much larger than this mass here.