Author Topic: SpaceX: Merlin 1D thread  (Read 228262 times)

Offline Lars_J

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Re: SpaceX: Merlin 1D thread
« Reply #640 on: 03/24/2013 05:40 AM »
Regarding a hypothetical Merlin 1E, maybe someone remembers - were there any rumors about it before it was revealed?  If yes, how long before?

What? There have been no 1E rumors.

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Re: SpaceX: Merlin 1D thread
« Reply #641 on: 03/24/2013 07:14 AM »
Sorry - see Edit above...
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Offline mlindner

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Re: SpaceX: Merlin 1D thread
« Reply #642 on: 03/24/2013 07:54 AM »
I'm not sure how all this discussion about a non-existant Merlin 1E came about... There have been _zero_ rumors about a Merlin 1E so let's stop talking about something that we have heard _nothing_ about it even existing. This is even worse than talking about the MCT which we barely only know the acronym for (but not what the letters stand for).

More so it look like Merlin 2 has been abandoned as well, unlikely to happen. Raptor is no longer a cryogenic upper stage, but now a methane stage-agnostic high thrust engine. (It honestly appears the concepts for Merlin 2 (higher thrust Merlin 1) and Raptor (high ISP upper stage) have been combined into one engine under the name Raptor.) SpaceX obviously changes even what names refer to over time, so there is no point on latching on to a name that doesn't even exist yet (Merlin 1E)...
« Last Edit: 03/24/2013 07:57 AM by mlindner »

Offline spectre9

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Re: SpaceX: Merlin 1D thread
« Reply #643 on: 03/24/2013 08:22 AM »
Rocketdyne engines have been tested to failure and that information has been made public.

SpaceX can do what they like I guess. Sometimes the secrecy is a bit annoying.

Offline mlindner

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Re: SpaceX: Merlin 1D thread
« Reply #644 on: 03/24/2013 08:30 AM »
Rocketdyne engines have been tested to failure and that information has been made public.

SpaceX can do what they like I guess. Sometimes the secrecy is a bit annoying.

I asked a friend who interned at SpaceX McGregor last summer about if he had heard of them shrapnel testing any engines by testing them till they blew. He hadn't. That doesn't confirm or deny though, just a data point.
« Last Edit: 03/24/2013 08:31 AM by mlindner »

Offline Comga

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Re: SpaceX: Merlin 1D thread
« Reply #645 on: 03/24/2013 03:24 PM »
Regarding a hypothetical Merlin 1E, maybe someone remembers - were there any rumors about the 1D before it was revealed?  If yes, how long before?

What? There have been no 1E rumors.

Actually, it is the opposite of rumors about SpaceX developing another evolution of the Merlin 1D.  I haven't found it but do recall a statement from SpaceX or Musk himself that there would be NO Merlin 1E.  And we heard about the 1D way, way back in the days of Falcon 1.  The Falcon 1E was based on SpaceX moving from the Merlin 1C to the 1D.

(Sorry if I misinterpreted an earlier post of "1E" to mean the rocket, which was planned, rather than the engine, which has not been planned or announced. I try to be quite explicit above.)

Offline krytek

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Re: SpaceX: Merlin 1D thread
« Reply #646 on: 03/24/2013 03:40 PM »
Regarding a hypothetical Merlin 1E, maybe someone remembers - were there any rumors about the 1D before it was revealed?  If yes, how long before?

What? There have been no 1E rumors.


Actually, it is the opposite of rumors about SpaceX developing another evolution of the Merlin 1D.  I haven't found it but do recall a statement from SpaceX or Musk himself that there would be NO Merlin 1E.  And we heard about the 1D way, way back in the days of Falcon 1.  The Falcon 1E was based on SpaceX moving from the Merlin 1C to the 1D.

(Sorry if I misinterpreted an earlier post of "1E" to mean the rocket, which was planned, rather than the engine, which has not been planned or announced. I try to be quite explicit above.)
It was Gwynne Shotwell. She was directly asked about it, and the answer was that there will be no 1E.
Currenty the 'rumors' hint at a light hydrocabon staged combustion engine.

Online cleonard

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Re: SpaceX: Merlin 1D thread
« Reply #647 on: 03/24/2013 05:41 PM »
Spacex seems to change the letter only when a rather large change is made to the engine.  There is a big change between the 1C and the 1D.  If SpaceX decides that a redesign is necessary, then we will see the 1E.  From what we have heard this is not yet the case so no 1E has been announced.

That doesn't mean that there are no changes going on.  I'd wager that there have been many incremental changes to the 1D design during the testing process. 

I do wonder if they have done any test to failures at over 100% thrust or just how long the engine will run at 100%. 

Offline Robotbeat

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Re: SpaceX: Merlin 1D thread
« Reply #648 on: 03/24/2013 05:50 PM »
I get the feeling their convention is that the number (Merlin 1c, d, etc, Falcon 9 v1.0, v1.1) is an indication of product class and heritage. This isn't that weird. Look at how much the RL-10 has changed or the AJ-10 over the decades. Incredibly different, same initial number and name.
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Online meekGee

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Re: SpaceX: Merlin 1D thread
« Reply #649 on: 03/24/2013 07:18 PM »
'sactly - that's all I said - that as they learn more about what post-flight engines look like, and as they get ready for F9R, there might be another revision, whether it's called "E" or not. Not exactly an earth shaking conditional prediction...

Any info on Raptor is irrelevant to this, since it's not replacing the Merlin anytime soon.

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Offline MP99

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Re: SpaceX: Merlin 1D thread
« Reply #650 on: 03/24/2013 07:28 PM »
Regarding a hypothetical Merlin 1E, maybe someone remembers - were there any rumors about the 1D before it was revealed?  If yes, how long before?

What? There have been no 1E rumors.
Actually, it is the opposite of rumors about SpaceX developing another evolution of the Merlin 1D.  I haven't found it but do recall a statement from SpaceX or Musk himself that there would be NO Merlin 1E.  And we heard about the 1D way, way back in the days of Falcon 1.  The Falcon 1E was based on SpaceX moving from the Merlin 1C to the 1D.

(Sorry if I misinterpreted an earlier post of "1E" to mean the rocket, which was planned, rather than the engine, which has not been planned or announced. I try to be quite explicit above.)

It was Gwynne Shotwell. She was directly asked about it, and the answer was that there will be no 1E.
Currenty the 'rumors' hint at a light hydrocabon staged combustion engine.

Clipped from http://www.aviationweek.com/aw/generic/story.jsp?id=news/awst/2011/08/08/AW_08_08_2011_p27-354586.xml&headline=SpaceX%20Plans%20To%20Be%20Top%20World%20Rocket%20Maker&channel=defense, Aug 2011:-

Quote
Revealing several new details of the 1D, Tom Mueller, propulsion engineering vice president, says the engine is designed to produce 155,000 lb. vacuum thrust and have a chamber pressure at “the sweet spot” of roughly 1,410 psia. “We’ve also increased the nozzle expansion ratio to 16 [compared with 14.5 on the Merlin 1C],” says Mueller, who adds that the initial engine “is doing better than we hoped.” The engine is designed for an Isp (specific impulse) of 310 sec. and has a thrust-to-weight ratio of 160:1. “We took structure off the engine to make it lighter. The engine we shipped [for test] to Texas was a development engine and hopefully the production engines will be even better,” he says.

The 1D design incorporates many lessons learned from the earlier Merlins and is of a simpler design with an increased fatigue life. “We’ve added the ability to throttle between 70% and 100%. Currently we have to shut off two engines during ascent, and on this we will be able to throttle them all,” he says. The development will also provide the basis for a 1D-Vac version intended for the second stage of the planned Falcon Heavy. “There are no plans to build a 1E. It’s going to be a 1D with the same turbopump.”
(My highlight)

Note, also, that Gwynne was mentioned in the earlier part of the same article.

cheers, Martin

Offline mlindner

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Offline MP99

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Re: SpaceX: Merlin 1D thread
« Reply #652 on: 03/24/2013 09:09 PM »
Clipped from http://www.aviationweek.com/aw/generic/story.jsp?id=news/awst/2011/08/08/AW_08_08_2011_p27-354586.xml&headline=SpaceX%20Plans%20To%20Be%20Top%20World%20Rocket%20Maker&channel=defense, Aug 2011:-

This URL is broken. Goes to "Page Not Found"

Yup, AvWeek only seem to put the articles up for a short while (presumably to advertise the magazines) before taking them down again.

That's why I said "clipped from" (and only pasted sections that were quotes from Tom Mueller). Evernote is your friend.

(Actually, I have a love / hate relationship with Evernote, but this it's good for.)

cheers, Martin

Offline Nomadd

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Re: SpaceX: Merlin 1D thread
« Reply #653 on: 03/24/2013 09:41 PM »
 I wonder if "able to throttle them all" means "will throttle them all. Don't you get a better isp at full throttle?  Then again, all engines running would help engine out numbers some.

Offline LegendCJS

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Re: SpaceX: Merlin 1D thread
« Reply #654 on: 03/24/2013 10:09 PM »
I wonder if "able to throttle them all" means "will throttle them all. Don't you get a better isp at full throttle?  Then again, all engines running would help engine out numbers some.

It is possible to fly a more efficient trajectory by taking advantage of the continuous spectrum of thrust offered by throttle capability than to deal with step changes in thrust from turning engines off.  All throttling will at least be symmetrical to avoid differential thrust causing a torque that requires counter steering. 

If, in the past thrust levels went from 9 arbitrary units to 7 units by shutting two engines off, then with 70% throttle capability, they would only have to throttle the outer 8 to 75% while keeping the middle engine at 100% to achieve the same 7 arbitrary units of thrust, but this assumes that the throttle-able 1Ds provide the same thrust at full rating as the 1Cs, which we know isn't true. 

It all depends on the details, but 1Ds make a lot more thrust than 1Cs, and therefore probably all engines must throttle deeply to have the same acceleration limits on the rocket for the same payload as previous 1C powered flight.
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Online meekGee

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Re: SpaceX: Merlin 1D thread
« Reply #655 on: 03/25/2013 12:40 AM »
btw - is it even a given that when you throttle down, the ISP remains constant?

The requirement to throttle for landing is for a very brief maneuver, so ISP is not of prime importance.

So the solution might not be suitable for the long initial burn.

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Offline baldusi

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Re: SpaceX: Merlin 1D thread
« Reply #656 on: 03/25/2013 12:41 PM »
btw - is it even a given that when you throttle down, the ISP remains constant?

The requirement to throttle for landing is for a very brief maneuver, so ISP is not of prime importance.

So the solution might not be suitable for the long initial burn.
Quite difficult that you'd keep isp the same. Even the RD-180 loses some 3 to 5 seconds when throttling. And that's probably one of the most efficient engines ever.

Offline krytek

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Re: SpaceX: Merlin 1D thread
« Reply #657 on: 03/25/2013 12:56 PM »
btw - is it even a given that when you throttle down, the ISP remains constant?

The requirement to throttle for landing is for a very brief maneuver, so ISP is not of prime importance.

So the solution might not be suitable for the long initial burn.
Quite difficult that you'd keep isp the same. Even the RD-180 loses some 3 to 5 seconds when throttling. And that's probably one of the most efficient engines ever.
Yes but is Isp equal to fuel consumption?
Maybe the Isp drops but the engines use less fuel due to lower thrust.

Offline kevin-rf

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Re: SpaceX: Merlin 1D thread
« Reply #658 on: 03/25/2013 01:29 PM »
Yes but is Isp equal to fuel consumption?
Maybe the Isp drops but the engines use less fuel due to lower thrust.

Think of ISP has fuel efficiency.

Dropping the ISP is the same as saying your car dropped from 30 mpg to 20 mpg. You used more fuel to go the same distance.
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Offline baldusi

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Re: SpaceX: Merlin 1D thread
« Reply #659 on: 03/25/2013 01:33 PM »
Yes but is Isp equal to fuel consumption?
Maybe the Isp drops but the engines use less fuel due to lower thrust.

Think of ISP has fuel efficiency.

Dropping the ISP is the same as saying your car dropped from 30 mpg to 20 mpg. You used more fuel to go the same distance.

Technically, you used more propellent mass units per unit of thrust. You obviously use less propellant overall since you are throttling.

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