Sort of. [She needs to keep in mind that not everyone is as intimately familiar with all of this as she is. Okay, just explain it naturally, Sheryl.] There isn't any friction in space, right? So there's nothing to stop something's inertia. Once something starts moving in space, it doesn't stop-- it'll keep going forever.

You need to spend energy and fuel to slow it back down again. If you want to bring a ship to a complete stop, you need to use as much energy as you originally spent getting it going.

It's pretty impractical.