[ErnstStavroBlofeld]

Remember, the interstellar space is vastly composed of hydrogen. A proposal called an interstellar ramjet was to scoop this hydrogen and spit it out the back as thrust.

[mitch5501]

I remember reading about that way back.Unfortunately the scoops needed to be huge (miles across) due to the scarcity of atoms in sufficient numbers to produce thrust.

Another form of thrust I remember was along the lines of detonating a hydrogen bomb directly behind a suitably armor plated spacecraft.

[count-your-change]

Sounds good but it would take a very large scoop since there is about one hydrogen atom per cubic centimeter unless they are in one of the gas “clouds”.