Bob Truax put a heat exchanger at the nozzle exit to extract wasted heat
albeit for a different end use but the concept was still valid.
Ken
On Thu, Feb 9, 2023 at 9:34 PM Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
On Fri, 10 Feb 2023, Rocket Pavitra wrote:
...Expanders suffer from a limit to how much thrust they can produce
because of the square cube law with the walls of the nozzle. ~300kN
It can go much higher, given clever design. Pratt & Whitney (builders of
the original expander-cycle engine, the RL10) proposed a "split expander"
cycle -- some of the fuel goes direct to the chamber, bypassing the
cooling jacket, and hence can be pumped to a lower pressure -- for the
RL200, their bid for the J-2 engine (200klbf, ~900kN). Much later, they
proposed a variant of this cycle at 600klbf (~2.7MN).
Also, there was some successful experimental work on putting a heat
exchanger in the chamber (!) to add more pump power.
Henry