From Tony Marshallsay
You report ideas for laser-propelled interstellar craft (24 August, p 8). Almost 10 years ago you reported on a similar idea of spacecraft powered by beams of plasma (newscientist.com/article/dn6543). At the time, I noted that, apart from the issue of maintaining a narrow beam, there were two other problems.
First, all the research was done using ground-mounted lasers, but how would you keep an orbiting projector’s extremely narrow beam accurately aligned on a tiny dot a few billion kilometres away for years?
Secondly, this idea was all about getting the spacecraft there much faster than with a conventional rocket. But on arrival, how would it slow down to enter orbit?
Riyadh, Saudi Arabia
