I'm not set-up to run the full Calc,
but it's a virtual certainty that, in
heating the bellows of the shuttles'
external tank, there will be thermo-
dynamic harmonics imposed within
the confines of the tank.
This's so be-cause the LOX will un-
dergo a periodic TempK variation
as it passes into and out of the pro-
posed heated bellows.
The thermodynamic harmonics that
will be set-up will occur as a function
of the LOS flow-rate and the Geom-
etry of the external tank, and be man-
ifested as pressure-harmonics, 'within'
the tank [be-cause the LOX will ex-
pand within the heated bellows and
rapidly-compress upon exiting the
heated bellows -- and the resultant
harmonics will take on a "life" of their
own, flowing while there remains LOX
in the external tank.
I don't know how powerful these
thermodynamic harmonics will be,
but they'll definitely be in-there.
It's =Necessary= to assure that no
destructive resonances will occur over
the course of the 'normal' LOX flow-
It's a Difficult Problem to resolve be-
cause these thermodynamic [pressure-
wave] harmonics resulting from the
heating of the bellows will definitely
also interact with any resonances that
occur due to 'normal' lift-off vibrations,
and also with Shuttle attitude changes.
[The harmonics will have the qualities
of a non-controlled "gyroscope".]
It is possible that combining-res-
onances can stress the enternal
tank like a "water hammer" phen-
omenon, and do so destructively.
I regret that I've insufficient data to
run the full Calc, but want to give
folks at NASA this heads-up.
If I were involved, I'd demand an
physical modeling of the proposed
heating of the bellows -- a model
of the tank, with the proposed heat-
ed section of the fuel line, on a vib-
ration-table, all closely-monitored
[If I've misinterpreted the NPR
News Reports I've heard, and
the heating is only on during the
filling of the external tank -- that
"the bellows" is not a fuel-line that's
active during lift-off -- then please
Forgive my wanting to give folks
a heads-up. I feel I Must be-cause
of the work I've done with respect
k. p. collins