From David Coker, Ledbury, Herefordshire, UK
Paul Marks asserts that Russia's workhorse spacecraft, Soyuz, has 20 engines (20 January, p 24). It depends what you mean by “engine”. Soyuz , but many describe these as parts of five rocket motors, each with one set of pumps feeding fuel to four combustion chambers. By this definition, the Falcon 9 first stage already has more engines than the Soyuz.
