Anyone that watches Dr Who knows the Doctor has a ship that is smaller on the outside, and bigger on the inside.
Now I won't go into the specifics of how it works, since my version won't work like it. Same function though.
Mass manipulation tech: So you got this spaceship that looks small, but on the inside it's bigger.
How? I won't bother with the explanation of how, since that only ruins the fun.
But given that you can fit the ship inside your house without it sinking through the floor (inside it's at least as massive as your house), the mass of the inside is obviously reduced from what it is outside.
What are the applications of technology like this?
For:
Space Travel:
Earth Economies:
You have the floor ladies and gents. By the way, trolls like Duck and Phi may reply to this, but you're on my ignore list, so I won't see it anyway. Yet if you must do so for your fans, by all means do so.
As for everyone else who actually wants to put in a worthwhile response, you have the floor.