Sea dragon and Big Dumb Booster.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
There are problems with scaling up engines in fact. The larger the
engine gets the more chance there is of 'combustion instability'.
This phenomena has killed one or two Russian programs outright, and
set back some others. Note the Russians are not noted for their
cluelessness in space launch vehicles.

Basically the combustion chamber resonates and sets up some kind of
oscillation with the fuel feeds. The engine frequently fails at that
point. Annoyingly, right before they fail, they apparently can have
greatly improved performance(!) ;-(

The smaller the engine is, the less chance there is of meeting it,
but quite small engines can meet it also; although much more rarely
as they oscillate at higher frequencies which tend to damp out.

Another annoying feature of these instabilities is that they
don't alway's occur and are difficult to test out.

This is one of the reasons that clustered engines are used.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

This is the legendary POGO phenomena. It may be possible to avoid these
problems with advanced computer modelling techniques. This is something
that those industrious Russians just did not have. During the early 60's,
when most of the development was being done, the US didn't have them
either.

Would it be possible to introduce damping of some kind? Maybe some kind of
spring damping system? Many previous BDB studies found that combustion
instabilities were reduced by keeping the feed pressures several atm higher
than the combustion chamber pressures.

Anyway, I'm no rocket scientist. If we manufacture clustered engines by
the thousand, then we might still retain the cost advantage. The amount of
R&D that would need to be pumped into a costly new engine development
program, means that it is probably best if we steer clear of engines that
might develop POGO problems.

On the other hand, some computer models may allow us to anticipate POGO
problems and therefor, allow us to design much larger engines.

Tony

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