Author Topic: SpaceX: Merlin 1D thread  (Read 520763 times)

Offline cambrianera

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Re: SpaceX: Merlin 1D Updates thread
« Reply #460 on: 10/03/2012 09:08 pm »
@iamlucky 13
It seems to me that the manifold does taper around the circonference; right side is smaller, and we can't see behind.
About nozzle extension maybe (maybe!) they could change material; titanium is 50% lighter than niobium with not so smaller high temp strenght.
Oh to be young again. . .

Offline simonbp

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Re: SpaceX: Merlin 1D Updates thread
« Reply #461 on: 10/04/2012 12:47 am »
South Africa after 1977 was fully metric only, so this is the measument system environment in which Elon Musk grew up. He left South Africa in 1988. The default "ton" definition to someone who used only metric and very little English measurments would be the metric ton.

http://ukma.org.uk/south-african-experience

So the interpretation of metric ton for this tweet has a foundation.

Except there isn't such a thing as a "metric ton" of force, just a metric tonne of mass (1000 kg precisely). Force/mass confusion is a common deficiency of American engineers...

He almost certainly got the number from his engineers, most of whom are American, and would have expressed it in US short tons of force (2000 pounds-force), so the thrust is about 160,000 pounds-force or 711 kN.

Ed Kyle's estimate of the mass of v1.1 the upper stage is 78.1 tonnes = 86.1 short tons. So, what Elon's tweet really says is that the upper stage has a thrust/weight just less than one at ignition. That's all it needs to be, and you don't want it too much higher or the burnout acceleration will be too high for the crew.

Offline QuantumG

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Re: SpaceX: Merlin 1D Updates thread
« Reply #462 on: 10/04/2012 01:15 am »
Except there isn't such a thing as a "metric ton" of force, just a metric tonne of mass (1000 kg precisely). Force/mass confusion is a common deficiency of American engineers...

It's not a confusion, it's shorthand.. and it's not just American engineers.

Human spaceflight is basically just LARPing now.

Offline bocephus419

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Re: SpaceX: Merlin 1D Updates thread
« Reply #463 on: 10/04/2012 02:30 am »
Copied from the "general" thread:-
First picture of the Merlin 1D-Vac:

https://twitter.com/elonmusk/status/252528724602400768
Quote
Elon Musk ‏@elonmusk
Now test firing our most advanced engine, the Merlin 1D-Vac, at 80 tons of thrust. pic.twitter.com/HGK1joVQ

I asked in the general thread, but my question was buried in the big long argument about T-shirts...  ::)

...what's the big ring around the base of the nozzle? The regen manifold is visible separately above it, so I know it's not that.

This is a totally random uneducated guess, but would the ring make sense as a mounting point for a retractable nozzle?

While we're making uneducated guesses, I bet they chose to dump the turbo pump exhaust into the main nozzle in order to make it sleek enough to be retractable.  I don't see an exhaust nozzle in spacex's reusability video nor do I see where they would put one: http://spacex.com/multimedia/videos.php?id=2

Offline cambrianera

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Re: SpaceX: Merlin 1D Updates thread
« Reply #464 on: 10/04/2012 06:38 pm »
Except there isn't such a thing as a "metric ton" of force, just a metric tonne of mass (1000 kg precisely). Force/mass confusion is a common deficiency of American engineers...

It's not a confusion, it's shorthand.. and it's not just American engineers.


+1
Oh to be young again. . .

Offline cambrianera

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Re: SpaceX: Merlin 1D Updates thread
« Reply #465 on: 10/04/2012 07:08 pm »
While we're making uneducated guesses, I bet they chose to dump the turbo pump exhaust into the main nozzle in order to make it sleek enough to be retractable.  I don't see an exhaust nozzle in spacex's reusability video nor do I see where they would put one: http://spacex.com/multimedia/videos.php?id=2
Don't try to read too many details into that video, the vision behind it isn't less than 5 years in the future for the first stage and 8 for the second stage.
For example the squared configuration for first stage engines has already been surpassed.
My "uneducated" guess is SpaceX ducted the turbo pump exaust into the main nozzle to:
-Gain a little bit ISP (as MeekGee says, the duct seems insulated, but for enthalpy conservation, not for test issues)
-Have a "relatively" cold flow (like F1) to use something less exotic (and heavy) than Niobium
Oh to be young again. . .

Offline newspacer

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Re: SpaceX: Merlin 1D Updates thread
« Reply #466 on: 10/04/2012 10:13 pm »
Don't read too much into the bottom of this picture. It is a setup for test. They can't test the actual nozzle because it would be super over expanded at sea level. The thing in the pic is probably a stub skirt for test.

Offline JBF

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Re: SpaceX: Merlin 1D Updates thread
« Reply #467 on: 10/05/2012 11:18 am »
Don't read too much into the bottom of this picture. It is a setup for test. They can't test the actual nozzle because it would be super over expanded at sea level. The thing in the pic is probably a stub skirt for test.

Remember they do have a vacuum chamber for testing these versions.
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Offline ugordan

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Re: SpaceX: Merlin 1D Updates thread
« Reply #468 on: 10/05/2012 11:25 am »
Remember they do have a vacuum chamber for testing these versions.

Not for MVac.

Offline JBF

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Re: SpaceX: Merlin 1D Updates thread
« Reply #469 on: 10/05/2012 01:15 pm »
Remember they do have a vacuum chamber for testing these versions.

Not for MVac.
[/quote

My mistake I was thinking of the dracos.  Heh I wonder how big a setup you would need to actually test an MVac. Heat dissipation alone would be tough.
"In principle, rocket engines are simple, but that’s the last place rocket engines are ever simple." Jeff Bezos

Offline iamlucky13

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Re: SpaceX: Merlin 1D Updates thread
« Reply #470 on: 10/05/2012 04:32 pm »
Don't read too much into the bottom of this picture. It is a setup for test. They can't test the actual nozzle because it would be super over expanded at sea level. The thing in the pic is probably a stub skirt for test.

It appears to be ended at the flange where the vacuum nozzle extension attaches, which I believe is consistent with past tests.

And just having a stub nozzle would not explain the large instrumented ring at the base or the apparently darker exhaust.

Although it surprised me as I said, I'm having trouble talking myself out of the conclusion they're dumping the turbo exhaust into nozzle and using something else for roll control.

@iamlucky 13
It seems to me that the manifold does taper around the circonference; right side is smaller, and we can't see behind.
About nozzle extension maybe (maybe!) they could change material; titanium is 50% lighter than niobium with not so smaller high temp strenght.

It's hard to tell with the shadowing. It may taper a bit, but not as significantly as the F-1 does. Again, this isn't critical, but one would expect a slower flow coming from the end of the manifold than the start, meaning uneven cooling, slight thrust imbalance, etc...but if it's easier to manufacture...

I also don't see the insulation.

By the way, I stumbled upon some really detailed images of how the nozzle of the F-1 is constructed here for comparison:
http://heroicrelics.org/info/f-1/f-1-thrust-chamber.html

Nothing really revealing, and obviously the brazed tubes in the F-1 are different than the Merlin's channel wall construction, but still gives some interesting details to compare and contrast.

Offline cambrianera

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Re: SpaceX: Merlin 1D Updates thread
« Reply #471 on: 10/05/2012 05:13 pm »
@iamlucky 13
sorry for the wording, I was not clear; the duct seems to me something like double wall (insulated), beefier in the middle and thinner on the flanges.
If you compare with F1, you see that flanges are bigger diameter than the duct (as normal for a single wall duct).
The double wall means also it's more difficult to see the taper.
About uneven distribution of flow I guess that sensors on duct are precisely to see temperature and flow.

Anyway I hope to see soon some more pics (or info).
Oh to be young again. . .

Offline Joffan

Re: SpaceX: Merlin 1D Updates thread
« Reply #472 on: 10/05/2012 05:32 pm »
Copied from the "general" thread:-
First picture of the Merlin 1D-Vac:

https://twitter.com/elonmusk/status/252528724602400768
Quote
Elon Musk ‏@elonmusk
Now test firing our most advanced engine, the Merlin 1D-Vac, at 80 tons of thrust. pic.twitter.com/HGK1joVQ

I asked in the general thread, but my question was buried in the big long argument about T-shirts...  ::)

...what's the big ring around the base of the nozzle? The regen manifold is visible separately above it, so I know it's not that.

I thought it might be some kind of stabilization (weighting/damping) for the stub nozzle due to the missing vacuum extension section. With some instruments to assess vibration embedded, as a further speculation.
Getting through max-Q for humanity becoming fully spacefaring

Offline MP99

Re: SpaceX: Merlin 1D Updates thread
« Reply #473 on: 10/05/2012 06:51 pm »
Copied from the "general" thread:-
First picture of the Merlin 1D-Vac:

https://twitter.com/elonmusk/status/252528724602400768
Quote
Elon Musk ‏@elonmusk
Now test firing our most advanced engine, the Merlin 1D-Vac, at 80 tons of thrust. pic.twitter.com/HGK1joVQ

I asked in the general thread, but my question was buried in the big long argument about T-shirts...  ::)

...what's the big ring around the base of the nozzle? The regen manifold is visible separately above it, so I know it's not that.

If you look in the background you will see a flex below the turbo pump.  Notice the dark streaks in the exhaust.  Compare it to the F-1 and the only conclusion is the turbo pump exhaust is pumped into the nozzle.

Isn't the turbo-pump exhaust shown at the left of the pic, rather than being diverted into the nozzle? This would need to remain separate if v1.1 us is going to use the same roll control as v1.0.

cheers, Martin

I could be wrong, been know to happen from time to time.

I thought the area I've surrounded in black was the gas generator exhaust.

cheers, Martin

Offline modemeagle

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Re: SpaceX: Merlin 1D Updates thread
« Reply #474 on: 10/05/2012 07:14 pm »
Copied from the "general" thread:-
First picture of the Merlin 1D-Vac:

https://twitter.com/elonmusk/status/252528724602400768
Quote
Elon Musk ‏@elonmusk
Now test firing our most advanced engine, the Merlin 1D-Vac, at 80 tons of thrust. pic.twitter.com/HGK1joVQ

I asked in the general thread, but my question was buried in the big long argument about T-shirts...  ::)

...what's the big ring around the base of the nozzle? The regen manifold is visible separately above it, so I know it's not that.

If you look in the background you will see a flex below the turbo pump.  Notice the dark streaks in the exhaust.  Compare it to the F-1 and the only conclusion is the turbo pump exhaust is pumped into the nozzle.

Isn't the turbo-pump exhaust shown at the left of the pic, rather than being diverted into the nozzle? This would need to remain separate if v1.1 us is going to use the same roll control as v1.0.

cheers, Martin

I could be wrong, been know to happen from time to time.

I thought the area I've surrounded in black was the gas generator exhaust.

cheers, Martin

Not sure what that is; angle would be off as it would produce roll.

Offline cambrianera

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Re: SpaceX: Merlin 1D Updates thread
« Reply #475 on: 10/05/2012 07:27 pm »
Modemeagle saw it correctly, the flex is under the GG-turbo pump assembly, in the right place for the exaust.
Oh to be young again. . .

Offline Hooperball

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Re: SpaceX: Merlin 1D Updates thread
« Reply #476 on: 10/05/2012 07:56 pm »
Flexible coupling (expansion joint) to allow for thermal expansion in the GG piping.

S

Offline Hooperball

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Re: SpaceX: Merlin 1D Updates thread
« Reply #477 on: 10/05/2012 08:02 pm »
GG gas is obviously being dumped into the nozzle extension which isn't present in this test.

S

Offline MP99

Re: SpaceX: Merlin 1D Updates thread
« Reply #478 on: 10/06/2012 02:27 am »
Modemeagle saw it correctly, the flex is under the GG-turbo pump assembly, in the right place for the exaust.

OK, thanks.

cheers, Martin

Offline MP99

Re: SpaceX: Merlin 1D Updates thread
« Reply #479 on: 10/06/2012 12:11 pm »
This sounds comparable to the J-2X, which does something similar, and has a pretty advanced Isp target for GG.

Is there any way to guess the Isp & thrust benefits on the kerolox M1D?

cheers, Martin

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