Building the better mousetr-...er, engine

Henry Spencer wrote:

"Current engines are (in my opinion) *nowhere* *near* fundamental
limits on
thrust/weight, even without magic materials like nanotube composites.
Improving that means lighter engines for the same thrust, or more
thrust
in the same package."

I just realized that I understand most of the different engine cooling
and pumping concepts, how rocket engines work, etc., but I don't know
what variables affect the mass of an engine, and how strong of an
influence they are.

So, where is there room for thrust/weight ratio improvement in
engines? Or rather, what are the variables that would affect the mass
of an engine of a given thrust rating?

Mike Miller, Materials Engineer

"Mike Miller" wrote in message
om...
Henry Spencer wrote:

"Current engines are (in my opinion) *nowhere* *near* fundamental
limits on
thrust/weight, even without magic materials like nanotube composites.
Improving that means lighter engines for the same thrust, or more
thrust
in the same package."

I just realized that I understand most of the different engine cooling
and pumping concepts, how rocket engines work, etc., but I don't know
what variables affect the mass of an engine, and how strong of an
influence they are.

So, where is there room for thrust/weight ratio improvement in
engines? Or rather, what are the variables that would affect the mass
of an engine of a given thrust rating?

Mike Miller, Materials Engineer

A complete redesign of the propellant handling system would be a good
start. About 2/3rds of the engine mass is not thrust chamber. That mass
is a maze of plumbing, turbine and pump rotor support systems, valves,
and controlers for all of it. The thrust chamber itself is almost an
afterthought
in terms of mass.

Redesigning the feed system would require going back to first principles.
Not "what is the most efficient turbine possible?", but "why does the
propellant
not want to enter the thrust chamber?". How can we get the propellant from
the 30 psi tank to the 3,000 psi chamber without all these subsystems?
Not "what is the most efficient way to build cooling passages?"but "how can
we build a thrust system with a minimum of cooling system complexity and
mass?".

Doing this without waving the laws of physics can be quite entertaining.
The solutions I have worked out require some independant evaluation
before rising to the level of newsgroup fodder.