Author Topic: Reignitable RD-191? (Read 2917 times)

Nilof · « **on:** 07/24/2015 04:32 pm »

Afaik the RD-191 is not designed to be reignited. Does anyone know if it could be modified to reliably do so?

If it could reliably reignite, its large throttle range and reasonable size would arguably make it the best engine for vertically landing heavy first stages.

baldusi · « **Reply #1 on:** 07/24/2015 05:05 pm »

Quote from: Nilof on 07/24/2015 04:32 pm

Afaik the RD-191 is not designed to be reignited. Does anyone know if it could be modified to reliably do so?

If it could reliably reignite, its large throttle range and reasonable size would arguably make it the best engine for vertically landing heavy first stages.

Anatoly Zak does says that there was a proposal for an upper stage version, the RD-191V. But it was an air startable version. I guess it wouldn't be impossible to restart, since it is designed for 10 starts. But the SSME experience shows that being air startable is not nearly the same as restartable. I remember how some engines needed to have their combustion chamber and cooling channels filed with water before start up. So restarting will depend heavily on the start up sequence.

Damon Hill · « **Reply #2 on:** 07/24/2015 06:08 pm »

What is the throttling range of the RD-191?

Nilof · « **Reply #3 on:** 07/24/2015 06:30 pm »

Quote from: Damon Hill on 07/24/2015 06:08 pm

What is the throttling range of the RD-191?

27% - 105%.

By comparison, the merlin only has a 70% - 100% throttle range. The RD-191 minimum thrust is almost as low as the Merlin's even though it is has more than twice the liftoff thrust.

asmi · « **Reply #4 on:** 07/24/2015 07:55 pm »

If my memory serves me, there were fire tests of RD-0124 with laser ignition system, which is claimed to allow multiple restarts. Similar system could theoretically be used on any other ORSC KeroLOx engine (RD-0124 is itself ORSC engine). However existing engines from RD-1xx family use TEB capsules for start-up, which are mechanically destroyed during ignition process, and therefore obviously these engines can't have inflight restarts. However engines are designed to allow replacing these capsules for engine re-use (and for testing - each and every RD-1xx engine built undergoes live fire test as part of QA). One of RD-170 engines went through 20+ (don't remember exact number) firings without any issues.

baldusi · « **Reply #5 on:** 07/24/2015 11:14 pm »

Adding start up cartridges is usually not such a big problem. The RD-0110 has ablative felt ribs on the main combustion chamber to avoid start up instabilities. That's a problem. RS-25 I can't remember but I believe that it ended up with water inside (besides the tremendous expenditure of the chill down sequence and the need for head pressure to start again). Those are issues. But adding start up cartridges is a long tradition. I remember the XLR81 as being on of the first ones.