Does the technology exist which could accelerate a nanoship to "one-fifth the speed of light", or perhaps more importantly, course-correct and slow it down as it nears its destination?
The numbers they are putting out are probably more than a little on the optimistic side, but the project is definitely a serious attempt and I'd love to see it succeed.
[0]: https://en.wikipedia.org/wiki/Spaceship_(cellular_automaton)