It's also unlikely to be worth the trouble, since the turbine exhaust is pure
hydrogen, and reasonably warm, giving decent Isp. and you need a way to cool
your giant nozzle anyway.
On Jul 13, 2016, at 10:07 AM, Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
On Wed, 13 Jul 2016, David Gregory wrote:
Wrt to the expander, seems likely to apply best to an open expander type
where you would burn the turbine drive for a little extra ISP
Which is another thing that *ought* to qualify as "obvious to one skilled in
the art", since afterburning in the turbine-drive gas stream is not a new
idea -- see, e.g., the Manski paper in JP&P Sept/Oct 1998. Although Manski
talked about it mostly in the context of a gas-generator cycle, not an
expander cycle -- don't remember whether he explicitly mentioned applying it
to an expander -- that's not a big leap.
(His conclusion, incidentally, was that gas-generator with afterburning
looked competitive with staged combustion, maybe even slightly better if done
carefully. Its average Isp is a bit lower, but the pump hardware and gas
plumbing are lighter. An optimized system is a little complicated, because
you need multi-stage pumps to match pressures to needs.)
Henry