"Richard Schumacher" wrote in message ...

The important point is that propellant is cheap, cheap, cheap, and loss of a launcher is as expensive as all hell.

Best reliability calls for a completely reuseable single stage launcher, with engines of such a size and number that, if at any
time one of them must be shut down, the others throttle up to compensate, and you just keep going.

This is not obvious.

In a world where engines explode upon failure, having exactly one engine per stage is best.

In a world where there are finite development dollars, and those dollars can buy reliability, having
one TYPE of engine per vehicle is best.

It has been suggested to me in private email that the correct answer to this delima is to have one engine
FAMILY, but with multiple engine sizes per family.


The "reusable" part means that you can get all of the design and manufacturing errors out of every flight article before it goes
into service. This also means that, in service, the chances of a catastrophic engine failure are negligible.

I dunno. Seems to me that airplanes occasionaly suffer failure despite their resability, and it's not clear why
repeated testing makes catastrophic failure preferencially less likely than any other type.