Author Topic: SpaceX: Merlin 1D thread  (Read 520302 times)

Offline cambrianera

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Re: SpaceX: Merlin 1D Updates thread
« Reply #480 on: 10/06/2012 01:19 pm »

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

cheers, Martin
Difficult crunch numbers, without hard design numbers for the engine.
But vacuum nozzle extension doesn't grow indefinitely for two reasons:
-obviously, mass of the extension grows
-second, friction increases on the increased surface
Dumping your gg exaust into the nozzle you can keep the high speed flow far from the wall, using an already slower, less energetic flow.
One hint is SpaceX already has numbers from two different nozzle extension configurations (the famous tin snip repair).
From that numbers they can evaluate the nozzle performance.
Anyway, I would not absolutely dismiss bocephus419 suggestion:
"they chose to dump the turbo pump exhaust into the main nozzle in order to make it sleek enough to be retractable"
Not going to bet on it, but possible.
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Offline simonbp

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Re: SpaceX: Merlin 1D Updates thread
« Reply #481 on: 10/06/2012 04:29 pm »
Would any of the changes make it easier or more difficult to to switch over to CH4? CH4 burns hotter, and so presumably have a higher chamber pressure per Newton of thrust.

Offline go4mars

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Re: SpaceX: Merlin 1D Updates thread
« Reply #482 on: 10/06/2012 05:32 pm »
If the gg exhaust can be actively controlled (which part(s) of the ring chamber manifold it goes through to the main chamber), it can act as a low mass thrust vectoring iris nozzle.  If most of the gg exhaust is directed to one port, for example, then it would very slightly change the thrust angle.  I mentioned that a few months ago.  But I agree that thermal expansion might be an additional reason for the segmented design.
« Last Edit: 10/06/2012 05:36 pm by go4mars »
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Offline Hooperball

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Re: SpaceX: Merlin 1D Updates thread
« Reply #483 on: 10/06/2012 06:19 pm »
How many stages are in the new Spacex built turbo-pump turbine? Its possible that part of the GG gas (before turbine nozzle) or a 1st stage or 2nd stage turbine bleed could be used for roll control while the lower pressure turbine exhaust is used for nozzle extension cooling. This could explain what looks like exhaust on the left in the picture.

How much thrust does the M1C tubo-pump exhaust produce? A couple thousand lbs? How much is needed for roll control on the second stage? A couple hundred?

I speculate the segmented "hot gas manifold"  could be the result of ease of manufacture but all the other plumbing appears to be smooth single segments. Its possible with this being a test article that the segments are shielding to more accurately measure thermal properties (piping surface temperatures and therefore pressures) in the smooth single piece hot gas manifold underneath without interrupting flow characteristics.

S

 


Online Comga

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Re: SpaceX: Merlin 1D Updates thread
« Reply #484 on: 10/08/2012 03:16 pm »
(snip)How much thrust does the M1C tubo-pump exhaust produce? A couple thousand lbs? How much is needed for roll control on the second stage? A couple hundred?
(snip)
S

Durring the second stage burn on yesterday's CRS-1 launch, the roll control seemed to be activated at about seven second intervals.  This was much more frequent, many more times, than on the three previous flights.  It would be interesting to see if this effects the implimentation of M1-D vac and second stage roll control.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Robotbeat

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Re: SpaceX: Merlin 1D Updates thread
« Reply #485 on: 10/08/2012 04:23 pm »
(snip)How much thrust does the M1C tubo-pump exhaust produce? A couple thousand lbs? How much is needed for roll control on the second stage? A couple hundred?
(snip)
S

Durring the second stage burn on yesterday's CRS-1 launch, the roll control seemed to be activated at about seven second intervals.  This was much more frequent, many more times, than on the three previous flights.  It would be interesting to see if this effects the implimentation of M1-D vac and second stage roll control.
I think it might be because there's a built-in biasing for when the roll control isn't engaged... In other words, it can only turn left hard, so they build in a bias towards the right, so if you want to go roughly straight, you have to turn left regularly (and if you want to go right, you just don't turn left). That way, they don't have to add another mechanism to make it turn right.

...and they perhaps increased the bias for this flight, allowing them a little greater control over the roll rate (in the biased direction).
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Online Comga

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Re: SpaceX: Merlin 1D Updates thread
« Reply #486 on: 10/11/2012 03:02 am »
Has anyone heard the number of starts that can be done by the Vacuum version of the Merlin 1D?
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline oldAtlas_Eguy

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Re: SpaceX: Merlin 1D Updates thread
« Reply #487 on: 10/18/2012 06:32 pm »
Has anyone heard the number of starts that can be done by the Vacuum version of the Merlin 1D?

The max capability other than the obvious of 2 is not known but a value of 3 has been speculated based on being able to do some missions that would need 3 burns.

Offline pechisbeque

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Re: SpaceX: Merlin 1D Updates thread
« Reply #488 on: 10/28/2012 09:26 pm »
Found this video on Facebook.

A short duration Merlin 1D Testing:
http://www.facebook.com/photo.php?v=10100751381781895

Offline mlindner

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Re: SpaceX: Merlin 1D Updates thread
« Reply #489 on: 10/29/2012 01:26 pm »
Has anyone heard the number of starts that can be done by the Vacuum version of the Merlin 1D?

The max capability other than the obvious of 2 is not known but a value of 3 has been speculated based on being able to do some missions that would need 3 burns.

I forget where I heard it, but I remember either reading or hearing from a friend who interned at SpaceX that they can restart regular Merlins up to 6-7 times.
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Offline MP99

Re: SpaceX: Merlin 1D Updates thread
« Reply #490 on: 10/29/2012 06:17 pm »
Has anyone heard the number of starts that can be done by the Vacuum version of the Merlin 1D?

The max capability other than the obvious of 2 is not known but a value of 3 has been speculated based on being able to do some missions that would need 3 burns.

I forget where I heard it, but I remember either reading or hearing from a friend who interned at SpaceX that they can restart regular Merlins up to 6-7 times.

Does that perhaps mean they can be ground started 6-7 times during their lifetime, including tests at McGregor?

M1C doesn't restart at all, and I don't think we've heard a number that high for Merlin Vac, either??

cheers, Martin

Offline Robotbeat

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Re: SpaceX: Merlin 1D Updates thread
« Reply #491 on: 10/29/2012 08:43 pm »
Has anyone heard the number of starts that can be done by the Vacuum version of the Merlin 1D?

The max capability other than the obvious of 2 is not known but a value of 3 has been speculated based on being able to do some missions that would need 3 burns.

I forget where I heard it, but I remember either reading or hearing from a friend who interned at SpaceX that they can restart regular Merlins up to 6-7 times.

Does that perhaps mean they can be ground started 6-7 times during their lifetime, including tests at McGregor?

M1C doesn't restart at all, and I don't think we've heard a number that high for Merlin Vac, either??

cheers, Martin
Merlin 1C can supposedly last for about 10 flight durations.
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Offline IRobot

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Re: SpaceX: Merlin 1D Updates thread
« Reply #492 on: 10/29/2012 11:44 pm »
Side question: what deteriorates between engine restarts? And how hard is to reset it to original conditions if they start reusing them?

Offline Robotbeat

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Re: SpaceX: Merlin 1D Updates thread
« Reply #493 on: 10/30/2012 12:26 am »
Side question: what deteriorates between engine restarts? And how hard is to reset it to original conditions if they start reusing them?
They already reuse them. They fire each engine at least three times before launch.

Merlin 1D is made for greater reuse.
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Offline guckyfan

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Re: SpaceX: Merlin 1D Updates thread
« Reply #494 on: 10/30/2012 06:28 am »
Side question: what deteriorates between engine restarts? And how hard is to reset it to original conditions if they start reusing them?
They already reuse them. They fire each engine at least three times before launch.

Merlin 1D is made for greater reuse.

I believe you speak of different things. I rephase the question I believe IRobot tried to ask, if you don't mind.

What capability of an engine is required for several restarts in one flight? What is required to reset that ability to max before launch after several test burns have been done?

This is unrelated or only losely related to the question on reusability or total burn time.

Offline Crispy

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Re: SpaceX: Merlin 1D Updates thread
« Reply #495 on: 10/30/2012 11:32 am »
What capability of an engine is required for several restarts in one flight? What is required to reset that ability to max before launch after several test burns have been done?
Ignition charges.

Offline guckyfan

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Re: SpaceX: Merlin 1D Updates thread
« Reply #496 on: 10/30/2012 12:21 pm »
What capability of an engine is required for several restarts in one flight? What is required to reset that ability to max before launch after several test burns have been done?
Ignition charges.

Thanks. So there is a number of charges on the engine and each restart consumes one.

Offline IRobot

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Re: SpaceX: Merlin 1D Updates thread
« Reply #497 on: 10/30/2012 12:54 pm »
That's it? Nothing deteriorates? So when an engine fails to start, what happened? Can another attempt be made, provided there are more ignition charges?

Offline john smith 19

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Re: SpaceX: Merlin 1D Updates thread
« Reply #498 on: 10/30/2012 01:07 pm »
What capability of an engine is required for several restarts in one flight? What is required to reset that ability to max before launch after several test burns have been done?

This paper
http://www.ulalaunch.com/site/docs/publications/IVF-Space-2012.pdf
on this thread

http://forum.nasaspaceflight.com/index.php?topic=29757.90

Discusses the sort of issues.

I don't know if Merlin uses uses pyrotechnics (starter cartridges) or pyrophors (liquid that burns on contact with O2) but both would be poor choices for a reusable design. The obvious choice would be a "spark assisted ignitor" IE a spark plug fed by a small LOX/HC flow like a miniature rocket engine in the chamber.

Note the results of the ULA work were that the *real* limit on re-starts was set by how much He was available to do tank re-pressurisation. This would probably apply to the Spacex upper stage as well. Spacex described their stage designs as "Semi-pressure stabilised" so tank pressure before engine start is probably quite important and RP1 is a liquid so simply pumping some heat into the tank to vaporise it won't work like LH2 (at least not at any *reasonable* temperature you'd want to use). You *could* tap some of the GG exhaust and if you got the water out you'd have roughly CO2 which would be a gas at these temps and AFAIK have a *much* lower density than any RP1 vapor.

OTOH were they to switch to a fuel that was a cryogen like LO2 they could use a system like the ULA integrated fluids approach. With pressurisation, propellant settling and power generation taken care of you can have as many starts as needed till you run *completely* out of propellants.

Good enough for Mars? IDK but certainly for escape burns to the Moon.
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Offline Crispy

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Re: SpaceX: Merlin 1D Updates thread
« Reply #499 on: 10/30/2012 01:18 pm »
The publicly available information is for the 1C, which uses pyrophor (triethylaluminium-triethylborane). I can't find anything on the 1D.

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