An optimized system is a little complicated, because you need multi-stagepumps to match pressures to needs.
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