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Archive 1

Article name

Should this article be at Merlin (rocket engine), sort of like Kestrel (rocket engine)? --NeuronExMachina 07:42, 18 Aug 2004 (UTC)

Done --Duk 20:19, 4 October 2005 (UTC)

Propose merger

I'd like to propose that Merlin 1B and Merlin 2 be merged into Merlin (rocket engine). The two child articles are very brief stubs, and not much outside information is available about the separate models. These models can adequately be covered as sections for the main Merlin article. If enough detail about one model becomes available in the future then it can be broken out. At this point the breakout just results in unnecessary clicking. --StuffOfInterest 17:21, 17 November 2006 (UTC)

Sounds good --Duk 17:29, 17 November 2006 (UTC)
Done. With the possible launch in a couple of days it seemed to prudent to get the cleanup done before the likely visitors show up. --StuffOfInterest 00:22, 18 January 2007 (UTC)

BFE = 27 Merlin 1C engines?

The following exchange is from an interview at http://www.washingtonpost.com/wp-dyn/content/discussion/2008/09/24/DI2008092402502.html

Urbana, Ill.: Right now you have two rockets based on the same first-stage engine (Merlin). To launch Falcon 9 Heavy, you'll need 27 of those engines to fire simultaneously. Do you have any plans to develop a larger engine in the future so that such clustering is not necessary?

Elon Musk: Yeah, I think there is an argument for a really really big Falcon engine or BFE, as we call it :)

That would be equal or greater to the thrust of 27 Merlin 1C engines. Would be exciting to see that fire! On the other hand, lots of small engines can give very high reliability. Google uses lots of small PC computers for their search service and it has never ever gone down.

91.107.42.12 (talk) 13:17, 28 September 2008 (UTC)

Merlin 2

Anyone know why the section on Merlin 2 was removed? Djd sd (talk) 04:39, 1 October 2008 (UTC)

I removed it because other than some vague hints three years ago, there aren't any sources for it. I just commented it out, looks like someone else deleted it. --Duk 05:20, 1 October 2008 (UTC)
Sounds like a good enough reason. With all the recent changes, I was having trouble figuring out who was doing what. Djd sd (talk) 07:25, 1 October 2008 (UTC)

Merlin Vacuum

Just received from SpaceX newsletter 

New Merlin Vacuum engine demonstrates highest efficiency for an American hydrocarbon rocket engine
McGregor, TX – (March 09, 2009) – Space Exploration Technologies Corp (SpaceX) successfully conducted a full mission duration firing of its new
Merlin Vacuum engine on March 7, at SpaceX's Test Facility in McGregor, Texas. The engine fired for a full six minutes, consuming 100,000 pounds
of liquid oxygen and rocket grade kerosene propellant.
The new engine, which powers the upper stage of SpaceX's Falcon 9 launch vehicle, demonstrated a vacuum specific impulse of 342 seconds – the
highest efficiency ever for an American hydrocarbon rocket engine. Thrust was measured at approximately 92,500 lb of force in vacuum conditions
and the engine remained thermally stable over the entire run.

Mchl (talk) 21:43, 10 March 2009 (UTC)

Yes, I just saw this also. A serviceable link for the information is spacex.com/press.php?page=20090310. N2e (talk) 22:25, 10 March 2009 (UTC)
Moved from article page: Xorsprite (talk) 03:31, 23 March 2009 (UTC) This figure disagrees with the "Engine specifications" section as published here http://en.wikipedia.org/wiki/Merlin_(rocket_engine)#Merlin_1C. Also this specific impulse of 342 s in a vacume does sound too high from what I've been reading making it even more efficient than the Soviet NK-33 (one of the highest specific impulse values of any engine for this type of fuel - LOX + Kerosene - and the Russians are still the world leaders) on the page http://en.wikipedia.org/wiki/Specific_impulse under "Figures for real engines" —Preceding unsigned comment added by Aremisasling (talk • contribs)
You are comparing apples to oranges. NK-33 is a first stage engine, so it is thrust optimized, not ISP optimized. The nozzles are shaped differently for one, the pumps are likely tuned differently for another. The Soyuz 2 upper stage engine RD-0124, also LOX/Kerosene staged combustion, has a vacuum specific impulse of 359 seconds. The Zenit upper stage RD-58M is a LOX/Kerosene engine using a gas generator cycle with a specific impulse of 353 seconds. Merlin Vacuum can also throttle thrust between 60-100% which saves fuel. Quasarstrider (talk) 16:24, 13 February 2010 (UTC)
First successful launch to orbit has raised "importance=mid"
--Mkouklis (talk) 14:10, 6 June 2010 (UTC)
With the Merlin Vacuum engine so much in the space news over the two days prior to the successful launch of Falcon 9 Dragon C1, due to the cracks in the Mvac nozzle and, ultimately, the decision to trim four feet of the nozzle off for the Dragon C1 launch two days after the cracks were discovered, I think the article would really benefit from a photo of the Mvac engine and nozzle, or maybe even a diagram comparing the Mvac with the standard Merlin 1C. N2e (talk) 15:53, 9 December 2010 (UTC)
How about these from Steve Jurvetson (License: CC 2.0): Merlin Vacuum engine bell, Merlin 1C, bell shrouded

Merlin Injector

Is the Merlin still a Pintle injector?

I thought the Merlin 1 and 1A were pintles but they went to a Showerhead injector on the 1B, and there after.

Granted the press info is just a little confusing, but, I thought i would ask —Preceding unsigned comment added by 71.178.199.89 (talk) 22:04, 27 January 2011 (UTC)

Graphic of Merlin 1C available for Wikipedia?

This article could really use a good photo or diagram of a version 1C engine.  There are some good ones here:  "http://www.spacex.com/updates.php". SpaceX. 2007-12-10. Retrieved 2008-06-12. {{cite web}}: External link in |title= (help)

I am not familiar enough with Wikipedia image guidelines to know if we can use one of these, and under what size/limitation conditions, so will leave that for other more graphic-aware Wikipedians. N2e (talk) 02:32, 13 June 2008 (UTC)

Since the article has a photo now, and it's a Creative Commons image, I have disabled the {{Photo requested}} tag. If there are additional/better images needed, feel free to undo my actions. Avicennasis @ 05:06, 31 March 2010 (UTC)
Yes, this article requires a replacement for the years-obsolete Merlin 1A engine diagram used in the infobox. This should be a diagram or illustration rather than a photo. --IanOsgood (talk) 21:39, 30 March 2011 (UTC)

Potential table for comparison of engine version specs

I believe it might be time to consider expanding the Merlin 1C Engine specifications section of the article to become a more general Specifications section that would provide an historical comparison of the various important versions of the engine. (this Talk section is independent of who would do the work of creating such a table; just interested for now to see if other editors thinks such a table a good idea).

It would seem that the first flight Merlin, the Merlin 1A, as well as the now-flown Merlin 1C and Merlin Vacuum would be included, along with perhaps the under-development-but-not-yet-flown Merlin 1D. What do others think about this? N2e (talk) 16:11, 6 April 2011 (UTC)

Merlin 1D details

Quite a bit of new info on the Merlin 1D enhancements, much not already in the article, is in this press article published January 11th: [1] <ref name=nsdc20120111> {{cite news |last=Bergin|first=Chris |title=SpaceX to begin testing on Reusable Falcon 9 technology this year |url=http://www.nasaspaceflight.com/2012/01/spacex-testing-reusable-falcon-9-technology-this-year/ |accessdate=2012-01-13 |newspaper=NASA Spaceflight.com |date=2012-01-11}} </ref> Enjoy. N2e (talk) 05:43, 12 January 2012 (UTC)

 Done Finally got around to getting a bit of the detail from this source on Merlin 1D design worked into the article, along with a general copyedit of the 1D section. I'm guessing there will be a lot of 1D stuff published with the first Falcon 9 v1.1 flight in March 2013.

Comparison Chart?

In my opinion, it would be helpful to have a side by side comparison chart of the different versions of this engine to help show the advances made with each version. Can somebody tackle this? Ffejmopp (talk) 16:18, 4 July 2012 (UTC)

Merlin 1C thrust - wrong

It seems that the thrust numbers for Merlin IC are way too much in this article.

SpaceX was planning to make a "slightly upgraded Merlin IC engine" , slated for the Falcon 9 block II, and the numbers in spaceX website(and in this wikipedia page) are for this version of the engine. This engine however has never flown and will never fly, as SpaceX is jumping directly to Merlin 1D in Falcon 9 v1.1.

The real maximum thrust of Merlin 1C in the flown configurations has been in the range of 423kN(sl), 483kN(vac). --Hkultala (talk) 04:43, 12 October 2012 (UTC)

Merlin 1D thrust-to-weight ratio

I am trying to get my facts straight for a Wiki article about Thrust-to-weight ratio on the Dutch Wiki, part is a table with rocket engines. Because in the article about the Merlin (rocket engine) it is stated that the Merlin 1D has the highest thrust-to-weigh ratio (higher then the NK-33) but there is no source about the engine weight. I don't think the 1D weights the same as the 1C! According to the stated Thrust-to-weight ratio it should weight roughly 990 lbs. Do not get me wrong, I don't care which engine is the "best" I just want to know if someone has a reliable source for the engine weight of the Merlin 1D? Thanks --Felipe de Jong (talk) 16:07, 18 September 2012 (UTC)

I looked around the web a bit for this a few weeks ago and couldn't find anything. Maybe someone else will have better luck. — Gopher65talk 01:12, 13 October 2012 (UTC)

Fastrac

Is it true that the Merlin engine uses the same technology as NASA's (cancelled) Fastrac project? --NeuronExMachina 03:19, 5 Aug 2004 (UTC)

I don't know all of the details, but here's an article on Fastrac and one on TRW's Low Cost Pintle Engine (LCPE) for future reference. Both engines were designed at roughly the same time and Tom Mueller, now VP of Propulsion at SpaceX, was on (led?) the LCPE team for TRW. Because of this, I would expect that Merlin would look more like LCPE than Fastrac. The merlin engine has roughly the same thrust as Fastrac and about 1/10 the thrust of LCPE. I guess I wouldn't be surprised to see a SpaceX design that looks an awful lot like LCPE coming out in the future.Dschmelzer 17:42, 5 Aug 2004 (UTC)
There's some discussion on the a-rocket mailing list that indicates SpaceX may have associated the turbopump with the Fastrac design, but that it's actually a clean sheet design. This level of detail is well beyond my expertise though. Dschmelzer 19:27, 23 Aug 2004 (UTC)
"Is it true that the Merlin engine uses the same technology as NASA's (cancelled) Fastrac project?" No. The Fastrac turbopump is a different turbopump in its entirety. The Spacex turbopump was developed by Barber-Nichols under a clean sheet design program and the designs although being similar are entirely different. There is a picture of the FASTRAC turbopump here: http://www.gkllc.com/lit/gk-authored/AIAA-2007-5537_Hydrogen_Peroxide-Optimal_for_Turbomachinery_and_Power_Applications.pdf (page 15 section V)and here is a picture of the Merlin Turbopump here: http://images.spaceref.com/news/2003/05.09.03.spacex.merlin_turbopump.jpg
You speak as if there is a single version of the Merlin engine. Which version was the Barber-Nichols' turbopump for? Could be that the original Merlin used the fastrac turbopump and the turbopump from B-N is for a more advanced version of the Merlin, like the B or C. (The C, I know, used a different turbopump than the original). --71.38.170.27 (talk) 23:59, 10 November 2012 (UTC)

"Raptor" is not necessarily "Merlin"

There is a subsection in the article entitled "Raptor". However, there is nothing in the sources given for the Raptor engine that indicates that SpaceX has given, or will use, the "Merlin" designator to the Raptor concept. I suspect, therefore, that this section should be removed as 'out of scope'.

On a related note, recent SpaceX news has a very large new rocket engine, fueled by LOX/LH2, to operate on a very large launch vehicle designated the "MCT". I have added this info to the Falcon (rocket family) article about a day ago. Another well-intentioned copied that text (with citation) here today. I just deleted it as there is no indication in the sources I've read that the "MCT" will be called by the designator "Merlin". BTW, there is no indication in the sources that the "MCT" is what used to be the "Raptor" concept engine either. So until sources come out clarifying that info, Wikipedia editors ought not to speculate. Cheers. N2e (talk) 01:42, 19 October 2012 (UTC)

 Done With the recent (November 2012) SpaceX announcments about developing methane-based rocket engines, and with Raptor now explicitly identified as a LOX/methane engine, I have removed the Raptor section, and replaced it with a link in See also. N2e (talk) 23:57, 23 November 2012 (UTC)

Proposed move: Merlin (rocket engine family)

I am proposing a move of the article from Merlin (rocket engine) to Merlin (rocket engine family).

Rationale: the article has emerged over time and has become an article not about any single rocket engine, but rather about an entire family of LOX/RP-1-propellant rocket engines all made by the same manufacturer. The three main engines in the series (Merlin 1A, Merlin 1C, and the Merlin 1D are substantially different rocket engine designs. For example,

- the Merlin 1D (650 kN (147,000 lbf)) has more than twice the thrust of the Merlin 1A (340 kN (77,000 lbf) of thrust), which means twice the mass flow rate of propellant, different injectors and nozzles, etc;
- the Merlin 1C uses an entirely different design of the nozzle cooling system (a regeneratively cooled nozzle and combustion chamber) while the Merlin 1A used an ablatively-cooled carbon fiber composite nozzle;
- Merlin is a manufacturer's name for a family of LOX/RP-1 engines, just as news reports are showing that SpaceX has planned a family of Raptor LOX/methane engines.
- The fact that the manufacturer chose to leave the lead-digit ("1") in the engine designator the same may have more to do with marketing, reducing perceived risk of change, and reduction of launch vehicle insurance rates than as an indicator of engine sameness.
  • SUPPORT — per nom rationale, as nom. N2e (talk) 13:16, 15 December 2012 (UTC)
  • Absolutely! I actually did the same thing to the Draco engine article when the Superdraco was released, although now I'm thinking that those two engines might be two different to be considered part of the same family. In that case we'll have to see as more information about the Superdraco is released, but the Merlins look like much more of a clear cut case to me. — Gopher65talk 14:07, 15 December 2012 (UTC)
 Done. No one objected after this had been here for a while, so I moved it. — Gopher65talk 21:27, 26 December 2012 (UTC)

Photo is outdated

The only photo/diagram in the article is of the smallest Merlin engine, a Merlin 1A. With the Merlin 1C being substantially more powerful and having now powered multiple flights, and the even greater thrust Merlin 1D having completed ground testing and scheduled for initial flights in 2013, I think the article would be improved by a better cross-section of Merline rocket engine graphics. I'm adding a {{reqimage}} tag. N2e (talk) 16:05, 5 December 2012 (UTC)

Indeed, this has been a problem for over four years! See previous comments. One idea: Steve Jurvetson is a SpaceX insider and amateur photographer who licenses all his photos under Creative Commons. Perhaps his SpaceX Flickr stream could yield a more recent Merlin photo. For example: A Merlin 1C on the factory floor. --IanOsgood (talk) 19:43, 5 December 2012 (UTC)
That is the same diagram, published a few months earlier. I presume it is the original. Perhaps we could import it for fair-use, since SpaceX is the author? --IanOsgood (talk) 05:01, 27 December 2012 (UTC)
Okay, that's good if a fair use rationale can allow it's use. I don't have any expertise in the Wiki-photo rulz game so generally leave that to other experts to help with. So if anyone believes fair use covers that diagram, I think it would be a really good diagram to have in the article, and Merlin 1C is so very different from Merlin 1A that the simple 1A graphic is a total misrepresentation. N2e (talk) 04:17, 28 December 2012 (UTC)

Editing by Barber Nichols

Apparently someone from Barber Nichols just went through the article and added a bunch of things saying they created the turbopump. Special:Contributions/184.96.79.5 Do we delete these or keep these? The information is unsourced. Ergzay (talk) 20:16, 25 March 2013 (UTC)

How do you know the IP (184.96.79.5) is from there? Although that is juicy info, we can't use primary sources. Tag it with {citation needed}. It's also not clear whether SpaceX designed their own pump for the Merlin-1D, since they tend to bring key technologies in-house. --IanOsgood (talk) 00:41, 26 March 2013 (UTC)


Thought this might be useful. The 70-100% throttling for Merlin D: http://www.nasaspaceflight.com/2012/06/spacex-merlin-1d-orbital-fire-aj-26-engine/ Davecporter (talk) 02:38, 8 March 2014 (UTC)

Rocket engine infobox

I'm not trying to be picky, but I feel the overall layout and content was better before the infobox was added. I don't really think the infobox is ready for primetime; it's used in only one other rocket engine article that I can see. And the content was changed; "sea level thrust" was changed to simply "thrust", and "vacuum thrust" became "thrust at altitude". I think the infobox itself needs more work before it should be added to the article, or at least before it is used to replace in-article information. Djd sd (talk) 09:35, 30 September 2008 (UTC)

I've done some work on the infobox; resize image instead of 'thumb' image, added thrust(Vac) and thrust(SL). --Duk 15:12, 30 September 2008 (UTC)


Hello i wanted to ask if you wanted to update the engine info box with the weight stats for the engine look at http://en.wikipedia.org/wiki/Thrust-to-weight_ratio for the datas on this i have done the math and its right at 440 kgs about its not a big deal but nice to keep as much data as possible in the infobox

Fwskungen — Preceding unsigned comment added by 89.162.81.222 (talk) 19:46, 13 August 2014 (UTC)

SpaceX has manufactured the 100th Merlin 1D now

The 100th Merlin ID engine has come off the manufacturing line as of mid-October 2014. Here's the source. Includes "SpaceX is currently the largest private producer of rocket engines in the world." and "Engines are currently manufactured at a rate of four per week, projected to rise to five per week by the end of 2014."

Also includes this bit on the specific manufacturing process for the engine, a process with elements of mass production involved that have not been traditionally used in rocket engine production: "The production process begins with major engine components – injector, turbopump, gas generator, thrust chamber, valves and actuators – integrated with tubing, sensors, and other small components to form the major sub-assemblies of the engine. These sub-assemblies are put together to become the engine’s lower and upper assembly. Once the lower and upper assemblies are stacked and mated, the engine undergoes a series of quality checks prior to testing." N2e (talk) 17:29, 23 October 2014 (UTC)

Merlin 1D thrust-to-weight ratio record

The opinion "The engine's 160:1 thrust-to-weight ratio would be the highest ever achieved for a rocket engine" seems wrong. Just look at the old Soviet and Russian rocket engines:

  • RD-270 - thrust-to-weight ratio was 201:1
  • RD-253 - thrust-to-weight ratio was 172:1
  • RD-701 - thrust-to-weight ratio was 212:1

Shpankov (talk) 18:12, 26 June 2012 (UTC)

I've seen it stated explicitly once (I think), but most of the time it's just implied: the Merlin 1D has the best thrust to weight ratio of any rocket engine of its type, not any rocket engine ever made. Not sure about thrust-to-weight specifically, but I don't think it's physically possible for a kerosene engine to achieve the same level of efficiency as a straightup hydrogen/oxygen burning engine. Lower costs, ease of use and transport, and higher fuel density all play a role kerosene use. There are reasons it's used, but high efficiency isn't one of them. — Gopher65talk 21:04, 26 June 2012 (UTC)
I also suspect that the reason they've been calling it "record setting" is because Orbital Sciences claimed that their "new (wink wink, nudge nudge)" Russian built NK-33 engine was "record setting". The NK-33 has a thrust to weight ratio of 137:1, which (at the time it was originally built in the 1970s) was the highest T/W ratio for a RP-1 (kerosene) rocket engine. Compare that to the 160:1 of the Merlin 1D, and you can see where they got the idea that it was setting new records. Since Orbital's new Antares rocket will be in direct competition with the Falcon 9 v1.1, SpaceX probably thought it would be good press to say "see, our new rocket's engine is more efficient than their new rocket's engine!!1!1!eleven!!" The Merlin 1D is a neat engine, but any time you hear a company use the phrase "record setting" you know it is their PR department at work, not the engineers (even when it's... more true than it is in this case). — Gopher65talk 21:21, 26 June 2012 (UTC)
Huh. I'd also read 160:1 in the past, but the most recent press releases say 150:1. I've corrected this article and added a source. — Gopher65talk 21:48, 26 June 2012 (UTC)

I don't think it's physically possible for a kerosene engine to achieve the same level of efficiency

Just look at RD-701 description - this engine with ratio 212:1 had used the same propellant.

Anyway, the phrase The engine's 160:1 thrust-to-weight ratio would be the highest ever achieved for a rocket engine. is incorrect and need more specifics mentioned or should be removed. Otherwise it disorient journalists :)

Shpankov (talk) 21:56, 26 June 2012 (UTC)

Hmm, the article linked by you said With nine Merlins on the first stage, the Falcon 9 rocket will produce nearly 1.5 million pounds of thrust in a vacuum. An enhanced design makes the Merlin 1D the most efficient booster engine ever built, with a vacuum thrust-to-weight ratio exceeding 150. But both these parameters are lower than for RD-701.

Shpankov (talk) 22:05, 26 June 2012 (UTC)

The RD-701 used liquid hydrogen as well as RP-1. It wasn't a pure kerosene engine. — Gopher65talk 23:08, 26 June 2012 (UTC)

In fact, it doesn't matter at all. In the Wiki article it is written highest ever achieved for a rocket engine. without explaining of engine type. Thus it's an incorrect info.

Shpankov (talk) 01:04, 27 June 2012 (UTC)

Yeah, that's clearly wrong. I've seen it in a few news articles too, but that doesn't make it any more right. — Gopher65talk 05:09, 27 June 2012 (UTC)

According astronautix.com those 3 engines mentioned have a much lower T/W ratio than the given numbers:

Who is right? — Preceding unsigned comment added by 87.223.90.34 (talk) 20:50, 21 July 2012 (UTC)

I found astronatix.com is a very poor source of Soviet engine specs. For RD-107 they claim dry mass of 410 kg (really 1190 kg) and specific impulse an unbelievable 326s (really 313s). ScalarField (talk) 20:08, 12 February 2015 (UTC)

There are a number of issues here.

First, you have to compare apples to apples. Merlin is an RP-1/LOX gas-generator cycle engine. It only makes sense to compare it to similar engines, such as perhaps the RD-107 family. RD-270 and RD-253 are staged combustion, and RD-701 is tri-propellant on top of that (mix of RP-1 and LH2 as fuel).

Second, T/W is not a meaningful efficiency metric, specific impulse is. You could consider T/W a metric of design efficiency for comparable designs, but ultimately it's specific impulse that shows how much delta-V you get from a set amount of fuel.

Third, SpaceX says Merlin's vacuum specific impulse is 309 seconds, while this article claims with a reference to their website it's 311. Has the number been revised down?

Fourth, where is the claim "The engine has the highest specific impulse ever achieved for a gas-generator cycle kerosene rocket engine" coming from? RD-107 family is gas-generator cycle kerosene, and they all have higher specific impulse than Merlin.

ScalarField (talk) 20:08, 12 February 2015 (UTC)

Merlin 1 bipropellant valve

This source shows the 2.7 kg (6 lb) bipropellant valve used for throttle control of the Merlin 1, and is spec'd to handle up to 1,500 pounds per square inch (10,000 kPa) of pressure in the fluid streams. It controls both the LOX and RP-1 fuel simultaneously from a single input. Quotation: "The Bi-Propellant Valve simultaneously meters liquid oxygen and RP-1 thru two separate channels using a single electromechanical actuator device for the SpaceX Merlin second-stage vacuum engine turbopump preburner."

The link is a primary source, so not as good as a secondary source for citation, so I'm not adding anything to the article at this time. But it does provide verifiable information about the nature of the throttle valve on the Merlin 1. Cheers. N2e (talk) 11:31, 21 April 2015 (UTC)

Based on the WP:PRIMARY policy, wouldn't it be acceptable to provide a factual statement that JASC manufactures the biprop valve? (I might just not understand the policy completely) It restricts any analysis or synthesis of primary sources, but from the information given on the JASC site it seems like a factual statement from it would still contribute to the article. Appable (talk) 17:03, 23 April 2015 (UTC)
Yeah, that's what the policy says. We can take things like specs from the SpaceX website, but we can't take interpretations from a primary website. So we can, say, list the thrust-to-weight ratio of a Merlin 1D from straight from SpaceX, but we can't use a statement like "this is the highest thrust to weight ratio of any RP-1 gas generator engine". The first is a factual statement by the manufacturer, the second is a interpretation by the manufacturer. The former is usable from a primary source, the latter is not. — Gopher65talk 04:37, 24 April 2015 (UTC)


Variants section

Hi. At the end of Variants section, it's written "this engine ... can be throttled between 60 and 100 percent". Does this percentage refers to the propellant? or is it some kind of rocket stage percent ? --Fotte (talk) 11:48, 8 June 2015 (UTC)

It means the amount of thrust it's producing. Which correlates fairly well with the fuel consumption (but not perfectly due to changes in burn efficiency at different thrust levels). Right now the Merlin 1D is throttled to about 75-80% of full thrust at most, because they've been running it in what we might think of as "safe mode" until they were sure it could survive full thrust. A very slightly modified version of the engine is due to debut in a few months (1D+) that will be rated to throttle over that full range. It will be regularly throttled to near 100% on standard missions. — Gopher65talk 13:19, 8 June 2015 (UTC)
I've always been under the presumption that the current engine is running at 100% throttle but only around 80% of its potential. Is the 1D currently actually throttled down below what they think the engine can do, or is it just not running quite as high as it could with minor changes? Appable (talk) 13:39, 8 June 2015 (UTC)

Merlin 1D-Vac Isp corrected

The previous Vacuum Isp of 311s was likely the Merlin 1C value. The 340s value is found here [1] click on 'inside the interstage': the relevant bit: "SpaceX's Merlin vacuum engine has the highest vacuum specific impulse (isp)--a measure of engine efficiency--of any American liquid oxygen/kerosene engine with a vacuum isp of 340 seconds. The engine is housed inside the rocket's interstage."

It would seem that the sea level Isp of 282s is also incorrect, but I cannot find a reliable source for the correct value. I don't think spacex has ever released sea level Isp for merlin 1D. Most sources on the web confuse it with the 1C number.

It should be noted that a Vacuum Isp of 340s is very good for a gas generator cycle engine. Infact, this number is on par with the staged combusion RD-180 Vac Isp of 338s. Unless that number is incorrect as well.Rocketdude78 (talk) 18:17, 1 May 2015 (UTC)

In my personal list of rocket engine ISP/thrust, I have these values: Sea level: Merlin1C 266/556kN, Merlin1D 282/654 kN; Vacuum: Merlin1C 305/616kN, Merlin1D 309/741kN, Merlin1D-Vac 340/801kN, Merlin1C-Vac 342/411kN. Sadly, I don't have references; they may have been directly from SpaceX employees and thus not are not usable on Wikipedia. --IanOsgood (talk) 14:47, 3 May 2015 (UTC)
This article needs to better distinguish between Merlin-1D and Merlin-1D-Vac. I think the top info box is confusing the two: the first-stage Merlin-1D performance in vacuum should be stated separately from the second-stage Merlin-1D-Vac performance. --IanOsgood (talk) 18:01, 4 May 2015 (UTC)
The infobox should give the performance of the Merlin1D, NOT the Merlin1D-Vacuum. 282s at sea level and 311s in vacuum are the correct numbers. A(Ch) 07:58, 5 July 2015 (UTC)
Or, rather, more correct. An engine producing 6,672/9=740 kn vacuum with an Isp 311 will produce 670 kn sea level with Isp 282, close to the 655 from 5,885/9. 340 s Isp applies only to the M1D-V used on the second stage, the first stage engines will be around 310 s, as Tom Mueller suggested. A(Ch) 08:23, 5 July 2015 (UTC)


Sources

  1. ^ spacex.com/falcon9

Some more information about current Merlin 1D weight and thrust.

Tom Mueller in quora.com

The Merlin 1D weighs 1030 pounds, including the hydraulic steering (TVC) actuators. It makes 162,500 pounds of thrust in vacuum. that is nearly 158 thrust/weight. The new full thrust variant weighs the same and makes about 185,500 lbs force in vacuum. You can do the math! BTW, I believe most other engines don't include the thrust vector control actuators in their F/W numbers.

I suggest that we can do the following changes in the M1D infobox

  1. change vacuum thrust to 723kN (from 740kN)
  2. add the engine weight @ 1030 pounds (or 467kg) with a reference that it includes the hydraulic steering actuators
  3. change TWR to 162500/1030 = 158 (from 150)

Also, I think it would be prudent to have a separate infobox about M1d vac, positioned at the section that describes it. Its really the same engine, but tuned for vacuum use, sporting a different nozzle and having more thrust, TWR and isp.

Any and every feedback would be vastly appreciated, cheers..C:

--85.72.86.19 (talk) 20:46, 8 July 2015 (UTC)

Some new numbers coming in on the Merlin 1-D full thrust and the improved Merlin 1-D vacuum

From SpaceX website.

http://www.spacex.com/falcon9

New figures given:

1. Merlin 1D-Vac 

  thrust is now 934kN / 210.000lbf
  isp is now 348s
  burn time is now 397s

2. Merlin 1D full thrust numbers 

  SL thrust 756kN / 170.000lbf
  vac thrust 825kN / 185.500lbf
  burn time is now 162s

Could someone update the infoboxes? Also, I think that we need 2 things. 1. An infobox on Merlin Vacuum 2. A section describing the Merlin 1D Full Thrust.

Many thanks..

85.72.73.49 (talk) 10:23, 21 September 2015 (UTC)

  • Thanks! I agree with points 1 and 2, but I'd love to hear other editor's opinions. Alternatively, for M1D Full Thrust, it could be a subsection of the M1D (since it's basically an uprated and modified M1D). I updated the infobox but haven't done any work on the M1D section yet, so that will likely require major revisions (or, as you suggest, a new section).
  • Does anyone else have an opinion on this? Would love to hear ideas. Appable (talk) 14:46, 21 September 2015 (UTC)
Great on finding the new data, 85.72.73.4. Definitely want to use it to update the article.
We should be careful not to throw out all the old data. Since Wikipedia is not just about the present, but also notable history, we should be certain to retain the old/former sourced specs, as they were correct for the initial version (2013 through June 2015 at least, and maybe also for the one remaining Falcon 9 v1.1 mission, Jason.
In other words, the new data should be added to describe the new "full-thrust" Merlin 1D, but the old data on the (non full thrust???, don't know the name) engine used in 2013-2015 should also be kept in the article. Cheers. N2e (talk) 23:54, 22 September 2015 (UTC)
I'm 85.72.73.49. and 85.72.86.19 in the thread above). I agree, here is what I think we need.
0. Lede
1. History: a short section explaining how the merlin came to be, its base on the TWR experience from Tom Mueller etc.
2. Design: the basic design of the engine
3. Variants
a. 1A
b. 1B
c. 1C
d. 1D
e. 1D Full Thrust
4. Merlin Vacuum
a. 1C vac
b. 1D vac
c. 1D Full Thrust vac
4. Production
5. Future variants (talking about the cancelled Merlin2.
Regarding infoboxes, it would be nice to have
1. M1-D FT at the lede
2. M1-C at 3c
3. M1-D at 3d
4. M1-D FT vac at 4c
what do you think guys? cheers..C: Dante 80 (talk) 02:24, 23 September 2015 (UTC)

Merlin 1D Vac Isp

Vac Isp is currently listed as 348 s, but clicking on the citation shows that the 348 is the Isp for the Merlin Vacuum engine. The extended nozzle of the Vacuum version drastically changes how the engine performs and it seems disingenuous to have it listed for the base 1D engine. There is a source in the article showing that it is actually 311 s.

I'm going to change it for now, let me know if there was reason the information was set up this way. — Preceding unsigned comment added by 2601:900:8200:29B0:A460:CF76:847A:8726 (talk) 09:58, 11 May 2016 (UTC)

The reason i changed it to 348s is because the figure is for Vacuum Isp and this article contains both vacuum and standard versions. Perhaps we can put both Isp? Hammer5000 (talk) 10:05, 12 May 2016 (UTC)

Merlin Vacuum Engine infobox

There should be an infobox for the Merlin Vacuum Engine. It's substantially different. Currently the infobox is using the thrust value for the sea level thrust of the Merlin 1D and the vacuum thrust of the Vacuum engine rather than the Vacuum thrust of the non-Vacuum engine. The Vacuum thurst is 914 kN not 934 kN. Ergzay (talk) 13:48, 14 May 2016 (UTC)

A new source on the Merlin engine

—N2e (talk) 12:55, 16 January 2013 (UTC)

Those links no longer work, but the article is archived at http://web.archive.org/web/20130115011750/http://tuts.pinehead.tv/2013/01/14/under-the-hood-with-the-spacex-merlin-engine/ and check out Mueller's Livescribe at https://www.youtube.com/watch?v=vVQyZn-VtXU AliShug (talk) 16:40, 6 October 2016 (UTC)

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Etymology

Two unsourced assertions about the origin of the Merlin name (a bird or a legendary character) were competing under an "Etymology" section. I removed the whole section until one of the theories is sourced. — JFG talk 23:33, 12 February 2018 (UTC)

Design could mention gimballing details

What angles can it slew, and how fast ? Are the TVC actuators hydraulic ? - Rod57 (talk) 00:36, 5 March 2018 (UTC)

Throttling capability (2019)

SpaceX updated their Falcon 9 user guide. Among other changes they gave us minimal thrust values in table 2-1. They are 57% and 64% for sea-level and vacuum version, respectively, worse than performance claims we have for the same type of engine in the article. Does that mean they decided to not throttle them down that much any more? Or did they change the engines? --mfb (talk) 08:09, 16 January 2019 (UTC)

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