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DBDude t1_j9ut6me wrote

Reply to comment by Adeldor in After Vulcan comes online, ULA plans to dramatically increase launch cadence by OutlandishnessOk2452

I wonder why they had so many problems with that engine, slipping the deadline again and again. Really, it's yet another oxygen-rich staged combustion engine, even simpler than the dual-chamber RD-180 it replaces. The Raptor is doing fine, and it's a much more complicated engine to engineer (full flow staged combustion).

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Adeldor t1_j9v0dbc wrote

I can only speculate. Possibilities that come to mind (which might not be popular):

  • Inefficient/interfering management

  • Insufficient expertise among employees

  • Customer "moving the goalposts"

  • A design quirk making realization difficult

I'm sure there are other possibilities.

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MT_Kinetic_Mountain t1_j9v1u30 wrote

I think there was some talk about BO trying to renegotiate a better deal for the engines or something? Take with a large table spoon of salt because I think I'd heard it on reddit.

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DBDude t1_j9v50b0 wrote

I did hear rumblings about inefficient management being related to why Bezos quit Amazon to be more involved in BO.

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mfb- t1_j9x4851 wrote

> The Raptor is doing fine

Most landing failures were linked to the engines not starting up properly. The recent static fire was done with 31/33 because two engines had issues. Compared to a landing this is less critical during a launch because of the large redundancy, but they clearly need to work on that for routine flights.

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DBDude t1_j9yf6e0 wrote

That was in testing. This thing does have a very complicated startup.

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mfb- t1_j9ykv8u wrote

The most recent test still had issues with two engines.

It's a complicated engine, but that doesn't mean issues are not issues any more.

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DBDude t1_j9z1jov wrote

My point is that the Soviets mastered this design almost 50 years ago, yet BO is having problems doing it just with a different fuel. Nobody's ever mastered full-flow staged combustion (didn't go beyond testing), yet SpaceX appears further along with that than BE-4, in about the same amount of time. My bet is that it's mostly management issues.

Edit: New news: ULA is having problems qualifying one of the engines for flight because it keeps pumping out too much oxygen. You'd think BO would at least have something like this right before they shipped, but apparently the engines had only minimal testing.

I like SpaceX, but I don't want them being the only cheap, reusable medium+ launch service out there. BO needs to get its act together.

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asssuber t1_j9v5wdd wrote

Raptor isn't doing that fine. You had many failing during starship's fights (not always the engine fault, but still) and 2 failing in the latest static fire. IIRC it also started development before the BE-4 (well before if you count when it was still supposed to burn hydrogen, but not much development was happening then). And let's not talk about deadlines, we all know that in the space industry they are just optimistic targets.

The RD-180 is a Russian engine, they have experience with oxygen-rich stage combustion, not the USA. AFAIK BE-4 will be the first oxygen-rich staged combustion engine made in USA to be flown (if we ignore that a full flow staged combustion engine also has an oxygen-rich side).

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DBDude t1_j9vjhn5 wrote

They lit 31 engines, a world record. The last time someone tried 30 they blew up four rockets in a row, the second one destroying the launch facility.

>IIRC it also started development before the BE-4

They were kind of playing around with ideas before BE-4, but real design didn't start until around the same time.

>if we ignore that a full flow staged combustion engine also has an oxygen-rich side

We'd have to. It's amazing to me that a modern company absolutely flush with cash is having serious issues designing roughly a methane variant of what's just a dual-chamber version of what was at the time a 25+ year-old engine. Something's been very wrong at BO. I'm just hoping now that Bezos is actively involved they can clean up their act.

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asssuber t1_j9wgqvt wrote

> They lit 31 engines, a world record.

They lit 32 engines, one shut down during the (short) static fire.

> The last time someone tried 30 they blew up four rockets in a row, the second one destroying the launch facility.

N1 is a very low standard to compare against. It's engines could not even be test fired prior to being mounted in the rocket, much less had a chance to do a full static fire like SH. Those were also the first staged combustion engines ever made, oxygen-rich on top. And the failures had more to do with the rocket than the engines themselves.

On the other end a very high standard of reliability is given by SpaceX itself. SpaceX flew Falcon Heavy five times, each firing 27 engines (plus the upper stage one) and it was 100% successful with no Merlin having a problem in any of the flights. 27 is almost the same as 30, the phantasm of N1 was slayed by SpaceX itself already.

Raptor is clearly immature and problematic if you compare it with Merlin, RD-180, Vulcan-2, etc. We have seen it's engine-rich exhaust several times and they are still tweaking the film-cooling for optimal performance, and might have other problems they haven't spoken.

Given ULA's more stringent standards (they aren't expecting to lose/scrap several test vehicles, going through dozens of engines like Spacex. They don't have engine-out capability to shrug off a few bad engines like SH), I do not see BE-4 as being less fine than Raptor.

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