Reply to post: Re: Depressing

Ex-Soviet engines fingered after Antares ROCKET launch BLAST

cray74

Re: Depressing

"Forgive me for my ignorance, but it was always my understanding that the problems of the N1 were not caused by the NK33 as an individual engine, but the rediculously elaborate and subject-to-complex-vibrational-modes plumbing necessitated by trying to use THIRTY of them in a single stage"

Nope, not the complexity of the plumbing. 3 out of 4 N-1 failures can be traced to something involving a NK-33 engine, more or less.

The first N-1 to blow up had an NK-33 engine develop an unexpectedly strong combustion oscillation in its gas generator. This shook a propellant pipe loose from that one engine, leading to a fire fatal to the rocket. The Russians responded by adding fire extinguishers.

The second N-1 to blow up had an NK-33 shake loose a bolt inside its liquid oxygen line a few seconds into flight, which got into the liquid oxygen pump and made the engine unhappy. The engine control computer tried to shut down that engine, and did so. Along with 28 others. The N-1 fell back on the pad and made one of the largest, manmade non-nuclear explosions. Rather than tightening production standards (and loose bolts), the Russians added metal mesh filters to the oxygen lines.

The third N-1 to blow up did not have engine problems per se. It went into a roll and the engines didn't have enough oomph to damp the roll by gimbaling. Later N-1s would have dedicated roll control engines.

The fourth N-1 to blow up again sort of had engine problems, or plumbing problems - but it wasn't a result of all the pipes from the 30 engines interacting. When this N-1 reached Max-Q, it throttled back to lower structural stress by shutting down some engines. The snap-shut valves and fast-moving propellant caused a "water hammer" effect in the fuel lines. One engine blew up (its oxygen pump ruptured from the water hammer effect), and the N-1 came apart.

None of those exactly happened because of engine plumbing complexity, though at least one had a problem start in the plumbing and ruin an engine. On the flip side, 29 of the engines on each of those 3 flights worked pretty well until the rocket blew up. That's 87 good NK-33 engine firings, right? :)

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