In this article at AvLeak, there’s discussion of an Aerojet LOX/Kero booster engine project called HC Boost (emphasis mine) :
Dubbed HC Boost, the technology development program is aimed at providing an improved, home-grown alternative to the Russian RD-180, the only other viable current-production hydrocarbon rocket engine. Unlike the RD-180, however, the US engine would be designed to be re-usable for up to 100 missions, have up to 15% better performance and would operate for up to 50 missions between engine overhauls.
Now, the RD-180 is a very high performance engine. It’s combustion chamber pressures are actually quite a bit higher than the SSME. When you combine this with the statements in this paragraph (my emphasis again):
The last US-designed and produced hydrocarbon engine was the Rocketdyne RS-27, based on 1960s technology and now out of production. The HC Boost engine, on the other hand, is expected to have higher operability, faster turn time, a longer-life thrust chamber, turbopumps and a new design nozzle.
It really does seem to suggest that they might be talking about thrust augmented nozzles. By going with nozzle thrust augmentation, you could get that same high lift-off thrust, and good sea-level Isp without requiring anywhere near as high of a chamber pressure. Which would necessarily lead to less demand on the thrust chamber and pumps.
A similar engine concept I’ve talked about with a few friends in the propulsion business is if you took the Merlin-1C upgrade that’s been hinted at by SpaceX, and applied that extra pump power they’re looking at creating to providing higher flow, lower pressure propellants to a TAN section (say by diverting some of that extra high pressure flow into some sort of a jet pump), you’d be able to get away with a much larger expansion ratio nozzle (with good sea-level Isp), while also nearly doubling the thrust. I really like the idea of a Falcon 1f that can put say 5000lb of payload into LEO for little more than the cost of a Falcon 1e….It’s a powerful concept, though I would understand if for now a company like SpaceX is focusing on getting Falcon-1 and -9 flying reliably first. First get it working and working reliably, then add the afterburners…
Which reminds me, I need to go back and do a more detailed article on some of the additional concepts and technical information I’ve found about Thrust Augmented Nozzles at some point.