"Their rocket engines are high performance" No all contemporary Russian engines have a much higher Isp. Usually because they use high chamber pressures in the

"Their rocket engines are high performance" No all contemporary Russian engines have a much higher Isp. Usually because they use high chamber pressures in the 3000+ psi range. The merlin series runs a mere 1000 psi. It does win one performance metric of thrust to weight. Little surprise because they might give up 10% of thrust (err, whatever) by running at a lower pressure but obviously running a third of the chamber pressure the engine walls are going to be about a third the thickness and a third the mass, so its a huge win for thrust to weight, knock down the nominator by 10% and the denominator by a factor of 3 and you win. So they do hold a record in this category. Also lower pressures imply lower temps imply lower thermal load, lower heat shock, lower thermal distortion and thermal related stress on startup/shutdown. It inherently should always outperform a Russian engine WRT restart / reusability unless something has gone very wrong. Two things make engines un-reusable. One is simple runtime. It seems intuitively obvious that a 1000 psi turbopump is cheaper and more reliable than a 3000 psi turbopump, all things being equal. The other thing that kills reusability is thermal shock effects where need something to be "X" thick to handle the forces and pressures, but the exterior or one side heats up much faster than the inside creating enormous stresses. So low pressure means low temps