From Anton Fletcher
Jeff Hecht says space is still hard (18 July, p 24). Indeed. The engines currently used to launch rockets work on the same basic principles as the V2 rockets of 1944. In the 1960s, these principles were refined into the mighty F1 engines that powered the Saturn V rockets, followed by the more efficient and powerful Russian-designed NK33 engines.
These use what is called a closed cycle, in which all propellant contributes to thrust. No one has yet built a more successful closed cycle engine, due in part to the failure of any American company to replicate the highly complex metallurgy necessary. Kuznetzov in Russia is very unlikely to restart production, even given a NASA contract.
The issue with all these engines is that they operate at the extreme limits of the capabilities of the materials available. And we just aren’t building enough of them to enable the designs to be worked upon. It took over 100 years and the building of millions of machines to refine the modern piston engine, which has at least 10 times the power and longevity of those from the turn of the last century.
Droitwich, Worcestershire, UK