[mountn man]

I always love these "We can get there in X days things. Yes, and the object can wave at Mars as it goes flying by since there's no equivalent system in Mars orbit, or the object of your choice orbit, TO SLOW IT DOWN! :-)

[Bidimus1]

Torch ships are an old idea, but they only get thrust in 1 direction.

Ion Drive and Orion Drive (nuke external combustion engine) are also way to move at a high speed but can be used as breaking systems too.

Note the video says “no known reason we cant do this” of course this is not it has not been tested in the real world in the slightest. Mostly this is a pitch for funding and I guess trying to keep the “we can do it” view at NASA.