Hey guys, I was trying to find if anyone had specific details about what ever happened to the RL10-C engine concept. Mark Wade lists it as having entered operational service, but the one stage they listed it as being used on (the Delta III Upper stage) actually used the extendable nozzle version that is also used on the Delta IV upper stages. I’m trying to figure out if the concept ever really did make it into hardware, and if so, what its status is.
The reason I’m curious is because if it was fully developed, and especially if it could be brought back into production, it might have a lot of use in the commercial manned orbital spaceflight world. Unlike other RL-10 engines which tended to emphasize Isp (which makes perfect sense since most of them were intended to be used on GTO stages), the RL10-C only had 450s of Isp, but was supposed to have a whopping 50% higher thrust than most other variants (over 35klbf instead of the ~22klbf that most of the other variants have). It isn’t a perfect engine, it weighs almost as much as two of the RL10A-4-2’s that Atlas V’s currently use, and only puts out 3/4 the thrust of a two-engine combo. But since it does that in a single engine version, that would tend to make it more reliable (and a lot more compact). For an Atlas V 401 using the RL10-C, you might be able to close out the black zones without sacrificing any payload. Heck, it might make even Delta IVM man-rateable without having to sacrifice too much performance to close out its abort black zones.
It also might make a WBC based EDS stage more doable, as you could get a lot closer to the T/W ratio of the current EDS while still keeping a better mass ratio.
Anyway, the engine as I said isn’t perfect, and things can still be done without it, but if it was either on-the-shelf, or close, it might be worth reinvestigating. Especially with the potential change in markets that could be coming from what Bigelow is doing with Lockheed.
Anyhow, if anybody with contacts inside of Pratt and Whittney could forward a link to this to your friends, I’m really curious. It might not be a good idea, but then again…