So why are we buying the Russian engines? "The engine has been used successfully 51 times on Atlas 3 and Atlas 5 missions since 2000" and " Defense Department estimates that losing the contract for Russian RD-180 engines would cost up to US $5 billion."
https://rt.com/usa/160932-russian-engines-space-us/
That's a good question. They are in fact much higher ISP (measure of fuel efficiency) than large US gas-generator engines like the F-1. Of course that comes at the expense of complexity and operating near the bleeding edge of failure. The Russian high pressure staged-combustion oxygen-rich engines like RD-180 are highly efficient, meaning they get more work out of a given amount of propellant than a less efficient engine would (meaning the rocket can be smaller overall for a given size payload capability than one requiring more fuel to do the same work using a less fuel-efficient engine like a lower pressure gas-generator design). The main reason though is simple-- price. The engines from Russia are cheaper than a US built engine would be, even a "simple" gas generator type. Also, a smaller rocket=cheaper rocket, therefore the more complex engine is rosy from that point of view too.
On the other hand, a lot of those advantages become less important if you start looking at having to build them domestically. The cheap price would DEFINITELY go away, and gearing up the tooling and know-how to build a US built version would NOT be cheap-- hence the $5 billion dollar price tag quoted above.
What's sad is that we SHOULD be developing these sorts of engines here, on our own, not funding a foreign power to do it... F-1 had a detailed and thorough "keep alive" program when it was shut down at the end of Apollo, where the technical information and a number of engines were actually stored carefully for possible revival of the engine at some point in time. F-1 has NEARLY been revived several times, including for the "Jarvis" space launcher proposed by Hughes after the Challenger disaster, using a pair of them for first stage propulsion on a shuttle ET-sized first stage, and a single J-2S for propulsion on an ET-diameter second stage, with a third "kick stage" for geosynchronous launches. Various proposals since then have also used F-1 at various times, and some work has been done, then stopped. Currently, Dynetics is working on reviving F-1 for their Pyrios LRB proposal for the advanced SLS booster competition. They've done some live fire tests of the turbopump gas generator and stuff, and redesigned the F-1, which was very complex for its day, into an engine with about 1/100th the parts count (lowering costs and reducing complexity), much simpler and more automated construction and assembly (lowering costs), and increasing the performance. They've switched to a channel wall nozzle design, much simpler and easier to fabricate than the old brazed steel tubular nozzle and combustion chamber design of the original F-1, with its thousands of hand-laid tubes brazed in one of the worlds largest autoclaves. They also did away with the film cooled nozzle extension of the original F-1, redesigning the complex turbopump exhaust manifold into a simple straight pipe, dumping the turbopump exhaust overboard at the exit plane of the engine nozzle (which is how it was done on early engines and rockets like Atlas, and the early Saturn I's using H-1 engines).
IMHO they'd do better to simply pay Dynetics to complete the F-1B and concurrently modify the Atlas V to use it instead, rather than trying to duplicate the RD-180 here. A barrel stretch of an existing rocket to contain extra propellant load is not a difficult thing to do, and an Atlas V phase 2 rocket using a pair of F-1B's and a core built on the larger Delta IV tooling, reapportioned for the different quantities of LOX and kerosene needed versus LOX/LH2 burned in the gas-generator RS-68's of Delta IV, would be an AWESOME space launcher (both for the AF AND NASA...)
Of course that makes too much sense so it won't happen... shame.
As for the quoted statement about Russian engines "not being reliable due to all the multiple chambers and complex plumbing"... that's UTTER HOGWASH. Completely nonsensical. During the mid-80's when we were struggling to get even 9 shuttle missions a year off the ground (highest number in a single year shuttle ever achieved IIRC), the Russians were launching Soyuz rockets (both manned and unmanned, each with 20 chambers in five main engines, and a four verniers on each core and a pair on each booster for directional control, so 32 chambers in all) with high regularity-- combined with other launchers they were using (Proton, etc) they were basically launching around 50 flights a year of all types... that's about ONE PER WEEK. The US has NEVER come close to this launch rate (this was the mid-80's, after all.) The Soviet Energia rocket used four advanced complex but non-reusable liquid hydrogen engines on the core (single chamber) and four strap-on kerosene fueled boosters (Zenits) each with a four-chambered LOX-rich, high pressure, staged combustion RD-170 powering it, for a total of 20 chambers burning at liftoff, and it flew successfully with zero failures of the booster itself.
A lot of this sort of mistaken ideas comes from the fact that the N-1 famously failed in all three of its launch attempts, but that was due to EXCEEDINGLY poor, virtually NONEXISTANT quality control and testing of individual engines (the NK-33's of the N-1 were built in groups of six, but only ONE was actually test fired-- if it passed, all the rest were 'certified to fly' with it... a cost cutting measure that proved disastrous. Plus, the flight control and engine control system used on N-1, the "Kord" system, was overly complex and susceptible to failures... it throttled engines for control rather than gimbaling them, and if an engine failed, it shut down the one on the opposite side to keep the thrust balanced and maintain control. This too proved disastrous. One of the test flights was lost due to foreign debris (probably a nut) being sucked into the high speed turbopump, causing an explosion and disintegration of the turbopump, perforating the propellant plumbing and igniting a fire. Another test flight suffered an engine failure and the Kord system subsequently shut down opposing engines, detected a fire, and shut them all down early in flight, allowing the N-1 to fall back unpowered onto the pad and explode, destroying the complex and killing workers underground. The last N-1 test lasted almost to first stage shutdown, but a few seconds early, engine failures and a fire caused the rocket to explode at altitude. Notice that these were all failures of SINGLE CHAMBER ENGINES operated in a cluster of 30, NOT a failure of a multiple-chamber engine like the RD-107/108 or RD-170 or RD-180.
Later! OL JR
Reason why it was thought to be pretty much impossible is the liquid oxygen being oxygen, tended to be a rather strong oxidizer. So the heated extremely oxygen rich exhaust out of the preburner tended to corrode/combust everything else downstream in the system; bearings, turbine blades, plumbing, etc. Consequently they tend to explode with very little warning if you did anything wrong in your design, as it's inherently much more touchy compared to using the kerosene (kerosene doesn't react with everything). So you tend to blow up a lot of test engines/ test stands before you manage to get it right. Of which they certainly blew up a lot of engines getting the technology right. But as a result they managed to get the highest performance kerosene/oxygen rocket engines ever created.
