The man developing the thing has a mission profile that will take you to Mars in about two weeks. Serious as a heart attack.
The spacecraft would accelerate halfway to it’s destination, go to a brief coast, turn the opposite direction, then kick in thrust again. Thrust is an acceleration, and it produces massive velocities. The spacecraft in this case would carry a great deal of fuel to do this, but not anything we couldn’t manage. Imagine a half-dozen liquid hydrogen tanks clustered around the ship, each about the size of a Shuttle external tank. You’d have to assemble the ship in orbit.
(Oh, BTW - that’s what we’ve done with ISS. Probably its greatest value, and not a small contribution to science and engineering.) :)