From Bryn Glover, Kirkby Malzeard, North Yorkshire, UK
I see that Paul Bowden has planned out a journey to the TRAPPIST-1 system. If it were a round trip, it would take 15 years on board and 80 years on Earth. Paul doesn’t mention exotic sci-fi forms of propulsion, so I assume he envisages some sort of rocket motor capable of burning continuously for 15 years to provide his 1 g of acceleration (Letters, 6 June).
I can’t imagine how to calculate the mass of fuel that would be required or the size of the fuel tanks needed. The problem is that both quantities would be so enormous that the engines would need to be massively scaled up, with the consequence that ever more fuel would be needed. I think Paul has a long wait ahead of him.
