[ldpg]

I think the "Mars in 3" days comment is just for scale, not a serious proposal.

This is more about getting probes to whiz past other solar systems. As obviously, you can't stop the craft.

[stcredzero]

you can't stop the craft.

Zubrin and someone devised a way to use magsails to decelerate starships without using onboard fuel. That's magic, as you're not subject to the rocket equation. (Really, it was a failed attempt to develop a Bussard ramjet, but they figured out you'd never overcome the "friction" with the interstellar medium. So they were like, let's go with the friction!)