On Mar 8, 2018, at 7:47 AM, Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
Robert Clark wrote:
But suppose we had a ceramic that had a melting point even higher than
the combustion temperatures? Then regenerative cooling would not be
needed and then like jet engines, rocket engines could operate for
thousands of hours, giving rockets reusability comparable to jet aircraft.
Modern jet engines use regenerative cooling *extensively*; in particular,
their turbine inlet temperatures routinely exceed the melting point (never
mind the maximum service temperature) of the turbine-blade materials. So the
idea that avoiding regenerative cooling is the magic that will confer long
operating life seems questionable.
By the way, conservatively-built rocket engines like the RL10A and the XCOR
engines already have reusability comparable to many jet engines (allowing for
the fact that one mission is hours of run time for a jet and minutes for a
rocket). The short useful lives of most large rocket engines have more to do
with their design philosophy (performance uber alles!) than with anything
inherent in rockets; jet engines designed the same way -- e.g. for cruise
missiles -- similarly have short lives and poor reliability.