SpaceX Merlin 1C Engine

[kraisee]

Yes, Ed.   I'm trying to remember the last time anyone had a cryogenic engine suffer a catestrophic failure (i.e. the engine blows up) on a launcher?

I don't think there has been a case in quite a while of an engine going bad in such a way that it did or might have taken a neighbouring adjascent engine out too.

STS-93 came close perhaps when all those controllers shut down, but even that flew successfully in the end.

As long as the Merlin has been able to lean on the vast library of lessons learned previously in other engine development programs, Space-X should be in a pretty solid position.


I'm still curious about that rumour a while back about Space-X considering an F-1 class engine in the future.

Ross.

[William Barton]

edkyle99 - 19/11/2007  4:50 PM

William Barton - 19/11/2007  3:32 PM

Jim - 19/11/2007  4:16 PM

But on the converse, there aren't aircraft with more 4 engines.  27 engines is not good

So it seems as if we are approaching a principle that there's is a point of diminishing return in each direction. B-52 was designed with 8 engines 60 years ago, and my guess is because that's how many of the size engines they could make back then that it took for that size aircraft. I hazily remember there was a proposal decades back to re-engine the B-52 with 4 big turbofans. So what's the optimum number of engines to get realistic engine out capability on an LV (assuming engine out a T-0 means not launching)? Five?

When was the last time an engine on a space launch vehicle went "out" in a recoverable way anyway?  

Sea Launch Zenit early this year suffered an engine failure at T-0 essentially - the kind of engine-out failure that I doubt any launch vehicle could recover from.  The same could probably be said for last year's GSLV Vikas booster engine failure right off the pad and the Soyuz Foton failure a few years ago.  Before that there were two Proton second stage engine failures in 1999 due to "foreign particles".  Falcon 9 wouldn't have survived those failures since it only has one second stage engine.  

Before the Proton failures I think you have to go back to the AC-74 Atlas booster engine failure back in 1993, but that was about 75 Atlases ago.  That rocket suffered a failure that caused reduced thrust beginning about 25 seconds after liftoff.  Perhaps that would have been a recoverable failure for a Falcon 9, but that was one instance in 14 years.  There have probably been nearly 1,000 space launches worldwide since then.

 - Ed Kyle

How many launch vehicles are flying which could survive any sort of first-stage engine out event, no matter how benign? Other than the Shuttle, which has survived a few, I don't know. I don't know anything about Proton plumbing, and it's one of the few multi-engine launchers that could be cross-fed (if it is, I don't know). If the Zenit 3SL had been a 9-engine LV instead of a 1-engine LV, would it have fallen back through the hole? How reliable are commercial jet engines? Should we be building single-engine airliners?

[edkyle99]

William Barton - 19/11/2007  4:15 PM

How many launch vehicles are flying which could survive any sort of first-stage engine out event, no matter how benign? Other than the Shuttle, which has survived a few, I don't know. I don't know anything about Proton plumbing, and it's one of the few multi-engine launchers that could be cross-fed (if it is, I don't know). If the Zenit 3SL had been a 9-engine LV instead of a 1-engine LV, would it have fallen back through the hole?

Upon further review, I suppose that it would not have fallen back, since Zenit 3SL has a liftoff thrust to weight ratio greater than 1.55.  If it lost 1/9th of its liftoff thrust, if would still have had a very positive thrust to weight ratio of something like 1.39.  Whether it would make up for gravity losses and still make the planned orbit is another question.

Falcon 9 is shown as having a high liftoff T/W ratio like Zenit, so perhaps T-0 engine-out is the plan.  If so, SpaceX is giving up a lot of payload for the rare "save" result.

How reliable are commercial jet engines? Should we be building single-engine airliners?

Reliability is such that they went from three or four-engines to two-engines on trans-Atlantic routes a decade or two ago.  Jetliners are not often falling into the sea to the best of my knowledge, although the occasional engine-out does occur.

 - Ed Kyle

[Jim]

William Barton - 19/11/2007  5:15 PM

1.  How many launch vehicles are flying which could survive any sort of first-stage engine out event, no matter how benign? Other than the Shuttle, which has survived a few, I don't know.

2.   I don't know anything about Proton plumbing, and it's one of the few multi-engine launchers that could be cross-fed (if it is, I don't know).

3 If the Zenit 3SL had been a 9-engine LV instead of a 1-engine LV, would it have fallen back through the hole?

4.   How reliable are commercial jet engines? Should we be building single-engine airliners?

1.  none

2.  not crossfed

3.  More than likely, especially if there is collateral damage.  Spacex Kevlar "shields" have not been tested

4.  Very, hence the ability of long range airliners to go from 4/3 to 2 engine  under ETOPS.  Also aircraft can glide.

[hop]

sitharus - 19/11/2007  1:42 PM

It's a matter of diminishing returns. Using many units of a small cheap engine lowers manufacturing costs, but it will generally raise integration and running costs.

The earlier suggestion of a 1 pump/multi-chamber (like the RD-170 and RD-107 families) development of the merlin seems like an interesting compromise.

Much of your production line can be common between different engines sizes (astronautix describes the RD-170 and 180 as being 70% common parts, and the development of the RD-180 was definitely cheap and quick compared to clean sheet designs), and you have less moving parts per engine. OTOH, you don't get the same engine out capabilities.

The other question is how far you take this. I'm not aware of any multi-chamber engine that uses more than 4 chambers.

The issue here is bootstrapping a LV business. You build one engine and get history on in. You use the crap out of it, taking it as far as you can to grow your business. If that means running 27 engines reliably - so be it.

Lets say you obsessively manage development(not so worried) and operations/dynamics(very worried - given past two launch attempts) to do this.

Lets also say you get a few working flights of Falcon 1 and Falcon 9. You then have very good motivation to move to a new engine with a proven vehicle to work from. And an equally good reason to have highly effective manufacturing, test, qualification, and launch operations to buy time allowing you to operate the Falcon 9 until you have the new engine/vehicle.

Space-X isn't Boeing or LockMart - they have to do 27 engines first stage heavy lift. The way people here are talking, sounds like predicting a failure like Korolev's N1 - not the same. Not easy, but not the same.

If the Falcon 1 does well third/fourth launch, they will have proven enough for Falcon 9. If they can launch a Falcon 9, they can get a heavy.

[Crispy]

to be fair, the N-1 didn't fail because it had so many engines. 30 engines made it harder, sure, but what really killed it was poorly designed and poorly tested hardware. Combine that with a ridiculously rushed program and it was always going to fail. What, specifically, are the issues that running 9 (let's start at the beginning) engines will throw up?

[meiza]

Aero313 already summarized those problems.
There's more hardware and that increases time spent before launch, and there are more things to go wrong both before and during flight.

[William Barton]

Jim - 19/11/2007  5:31 PM

William Barton - 19/11/2007  5:15 PM

1.  How many launch vehicles are flying which could survive any sort of first-stage engine out event, no matter how benign? Other than the Shuttle, which has survived a few, I don't know.

2.   I don't know anything about Proton plumbing, and it's one of the few multi-engine launchers that could be cross-fed (if it is, I don't know).

3 If the Zenit 3SL had been a 9-engine LV instead of a 1-engine LV, would it have fallen back through the hole?

4.   How reliable are commercial jet engines? Should we be building single-engine airliners?

1.  none

2.  not crossfed

3.  More than likely, especially if there is collateral damage.  Spacex Kevlar "shields" have not been tested

4.  Very, hence the ability of long range airliners to go from 4/3 to 2 engine  under ETOPS.  Also aircraft can glide.

Thanks for the info on one & two. That's what I suspected. As for three, I'm guessing SpaceX is hoping the shields are never tested during "rapid unscheduled disassembly." An for item four, I would hate to go through the experience of a dead stick landing in a modern commercial airliner with its fly-by-wire systems inoperative. Even with lots of nice ocean below.

Here's a question: was the 4 to 3 to 2 decrease in airliner engines driven by safety or cost concerns? I'd bet cost.

[wannamoonbase]

Given SpaceX's resources and experience base doing it with 9 or 27 small engines is their only option.  How the economics play-out will be interesting as it could effect the industry world wide.  Can you assemble rocket engines on an assembly line to reduce costs and still get the reliability required.

We may not know until we see if the F9 fly successfully, and more than once.  The F9 HLV would really be something to see lift off no matter how you feel about it.  That would set how many different kinds of records.

I think the examples of the N-1 are flawed because the Soviets never had a good enough grasp on systems integration to pull it off and workmanship and controls were never going to be good enough to control the beast.  

SpaceX's engine out argument is also flawed because they are throwing on so many engines they need an engine out option.

I am getting impatient and want to see some tests and rockets on the pad at this point.

[Lampyridae]

The R-7 used to boost with what, 20 engines and 12 verniers? I don't know how much plumbing was shared on those. The main problem seemed to be valve issues but once those got sorted out it seemed to be highly reliable. I have no idea whether any of them survived an engine-out to orbit though.

That being said, Armadillo's lander hopped all over the place, banging and spewing bits of itself everywhere for 3 flights in a row (with different engines of course). So maybe the idea would hold for F9?

[Lampyridae]

...my point being that rocket motors can be built to be rugged. Armadillo and F9 are in totally different leagues.

[Jim]

Lampyridae - 20/11/2007  8:33 PM

The R-7 used to boost with what, 20 engines and 12 verniers? ?[/QUOTE}

only 5 engines.  Each engine has 4 nozzles.  No need to further expand this part of the thread.  This has been shown over and over

[sitharus]

Lampyridae - 21/11/2007  1:33 PM

The R-7 used to boost with what, 20 engines and 12 verniers? I don't know how much plumbing was shared on those. The main problem seemed to be valve issues but once those got sorted out it seemed to be highly reliable. I have no idea whether any of them survived an engine-out to orbit though.

That depends on how you look at it. R7/Soyuz first stage uses 5 sets of turbopumps driving 20 main chambers/nozzles and 12 verniers. Since the four chambers are powered by one set of pumps it can be considered to be a single engine. Also, each set of pumps has its own dedicated tanks, so the plumbing for each engine is independent. Falcon 9 will have one set of tanks driving 9 turbopumps powering 9 chambers.

[Frediiiie]

Falcon 1 flights 3 & 4 are evidently to be merlin 1c engines to give some flight time to that engine before Falcon 9 flies.

[Chris-A]

M-1C Flight qualification for Falcon 1
http://www.spacex.com/press.php?page=37

Falcon 1 configuration:
- 78,000 lbs at sea level, and 90,000 in vacuum
- Isp 301 seconds in vacuum.

“In the coming weeks we’ll begin qualifying Merlin for the higher thrust and performance levels required by our Falcon 9 rocket, keeping us on track for delivering the first Falcon 9 vehicle to Cape Canaveral by year end.” - Elon

Cool pic :cool:

[Frediiiie]

They also said in this post that they are gearing up to build 1 engine a week.
This is up from the "1 every two weeks" they had said earlier.

[Patchouli]

There was one vehicle that could handle an engine out at any moment in flight that was both Saturn vehicles they both had first stage engine out capability.

The Saturn V did reach orbit a few times after loosing as many as two engines off the second stage.
Falcon 9 should be best compared with the Saturn IB which had 8 H-1 engines .

The N1 first stage wasn't properly tested and the Soviets didn't have kevlar jackets for their engines or computer health monitoring on the level we have today.

The kevlar shields on F9 will be ground tested extensively before it flies.
Spacex has the benefit of a test stand something the N1 designers never had.

If the engines have anti explosion shielding and control computer are up to the task Falcon 9 would likely be able to handle a Zeint type failure of one engine and still complete the mission or atleast perform a safe abort.

Lastly remember the shuttle was saved numerous times by it's health monitoring systems they're partly why the SSME is so reliable despite being a combined cycle engine which historically were very ill behaved and fickle machines.

The Russians blew up a lot of RD170s before they got it right and I think even it uses a lot of health monitoring though I could be wrong.

The Merlin 1C is not a combined cycle engine like the NK-15 used on the N-1.

It's closest relatives are actually the LEM descent engine and the H1 off the Saturn I-B
It's a turbopump cycle pintle injector engine a very simple and reliable design.

Comparing Merlin to the NK-15 would be unfair even silly as one engine operates well within the limits of it's materials and the other operates right on the edge of what it's construction  materials can handle.

It would be like saying all piston engines are very prone to exploding because top fuelers often explode.

To make the difference stresses easy to understand you could compare the Merlin 1C to an F1 racing engine and the NK-15 to a topfuel dragster engine.

As for the existence of two engine airliners it has little to do with safety and everything to do with costs plus cleaner aerodynamics.

1. We just simply have large engines today which didn't exist a few decades ago.

2. We now know how to keep an aircraft under control despite the tenancy of the asymmetric thrust from having one engine operating to make the aircraft yaw which was from what I read a very difficult issue to resolve.

3. The reliability of jet engines have increased greatly over the years so you're a lot less likely to end up having to deal with 2 but it still happens.

[Jim]

Patchouli - 17/3/2008  3:45 PM

There was one vehicle that could handle an engine out at any moment in flight that was both Saturn vehicles they both had first stage engine out capability.

Incorrect.  It could not handle losing one at T+0

[Patchouli]

I thought the Saturn performed a post ignition hold down before letting the vehicle go during launch making such a failure at T+0 just a mission abort where you just simply cut the thrust?