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Juan Suros

I read it the same way: 'The Merlin 2 will be a scale model of the F-1 class engine design we'd like to build in a few years.'

Holy cow! The only possible use for such an engine would be a 100Mg class payload lifter. BFR indeed.

I wonder how low they could get the cost of a pound to orbit with the Merlin 2 and F-1 class engines. Are there any figures out there?

Dave Gish

Well, now that there is a potential customer with 100-ton launch requirements, it makes sense to start thinking about a super heavy lift F-1 class engine. If Falcon and Falcon9 are a success, then this could lead to a credible 100-ton private (relatively cheap) launch capability, which could help to offset potential federal budget cuts in the future.


Largest active engine is the RD-170 at 1.7 million pounds thrust at 4 chambers. For SpaceX to have the largest single-chamber thruster that is not the F-1, then Merlin 2 should have greater thrust than RS-68, but less thrust than F-1. Using the RD-180 at 850,000 lbs thrust as the upper limit for Merlin 2 thrust is probably not correct. Musk's public comments probably indicate they are thinking of Merlin 2 as something between the 650,000 lbs of RS-68 and the 1.5 million lbs of F-1.

The TR107 was a pintle-injector LOX/RP engine with thrust rated at 1.1 million pounds. Northrop received about $40 million in NASA contracts up to FY05 to develop this engine for the now cancelled SLI. Northrop maybe thought that SpaceX had borrowed their Merlin 1 engine design from the TR107 engine.

I am just guessing, but SpaceX could continue the design work of the TR107, and call it the Merlin 2. This Merlin 2 would look very similar to both the Merlin 1 and the TR107, and they could ask for NASA/DOD contracts to develop it.

A Merlin 2 with 1.1 million lbs thrust, like the TR107, would give 3.6 meter diameter Falcon 9 vehicle a 33,000 lbs to LEO performance - similiar to Sea Launch Zenit or proposed Soyuz 3. They would price this between the $35 million Falcon 9 with 5 meter fairing and the $51 million version that does 33,000 lbs to LEO. This rocket would eliminate the need to learn parallel staging on the S5 version of the Falcon 9. There is probably not a large market for the 50,000 lb payload version of the Falcon 9 triple, but it looks nice in brochures and Air Force/NRO EELV customer briefings.

The 1.1 million lb thrust Merlin 2, similiar to the TR107, could be later integrated into a 7.2 meter or 8 meter diameter vehicle that offers 132,000 lbs to 330,000 lbs payload to LEO, with engine out capability on a 5-engine or 9-engine first-stage. For this new rocket, SpaceX would have to learn how to double the diameter of their Falcon 9 vehicle, to 7.2 meters or greater, just as they doubled the diameter of the Falcon 1 to become the Falcon 9. If you re-evaluate the Saturn V vehicle with a LOX/RP second-stage powered by a Merlin 2 (or TR107), an 8-meter diameter, a 5 Merlin 2 engine first-stage (i.e. 5.5 million lbs thrust), and no thrird-stage then you probably get a payload number around 176,000 lbs (i.e. 80 Metric tons).

Who is the customer? What is the market? The customer could just be a development contract for Merlin-2 engine development. For payloads, the customer for a 33,000 lb version of Falcon 9 is the same customer-base for Sea Launch and Ariane V - commercial launch of 10,000 lb class satellites to GEO, which the proposed Falcon 9 single can't do right now. The customer for a 60 metric ton to 130 metric ton launcher is the Air Force or anyone wanting to fly to the Moon or Mars. Space Adventures will fly a minimum of 2 paying passengers to the moon for $100 million each, which is a minimum of $200 million. I would think that many countries would pay $200 million to fly around the Moon, Venus, or Mars. I would guess that SpaceX could find a way to profitably launch a much more capable payload than Space Adventures is planning for well under $200 million if SpaceX ad this vehicle.

The cost of Merlin 2 engine development should be under $100 million, because SpaceX has the TR107 as a baseline. If it costs SpaceX $200 million total to develop an 80 metric ton payload vehicle, and a Merlin 2 engine to propel it, SpaceX would make a $50 million profit if the U.S. Air Force gave SpaceX a $250 million demo launch contract similar to the $250 million launch contract they gave to Boeing for the partially successful Delta IV Heavy launch demo (with only 25 ton capability). If SpaceX gets NASA or the Air Force to pay for the development on cost-plus contracts, then the economics are really in their favor.

If the Merlin 2 is the TR107, then the risk to return economics are not as bad as they might initially appear. For an investment of $100 million to $200 million in the Merlin 2, SpaceX might double their competitveness and the market of payloads that they are qualified to launch.

What do you think?

Daniel Schmelzer

Thanks for the very meaty response, anonymous. I'll have to review in detail, but I've since revised the link to Musk's update discussing Merlin 2. This is important, because it appears the F-1 class engine is really Merlin 3, not Merlin 2. Merlin 2 is merely a scale version of the F-1 class engine. In pertinent part...

"The next major engine development for SpaceX is the Merlin 2, where we will aim for a significant increase in thrust and chamber pressure. Merlin 2 will serve as an exact scale version of the F-1 class (>1,500,000 lb thrust) engine we intend to start developing in a few years. Target performance numbers will be released in the spring."

Daniel Schmelzer

So far, there is one ready customer for the 50,000 lb. to LEO market -- Bigelow Aerospace's BA330, fully loaded. I guess NASA or Bigelow would be the potential 260,000+ lb. to LEO market, but that market does seem rather speculative.

I agree that parallel staging is merely for brochures, as the Merline 2 engine becomes available on an uncertain timeline (i.e., parallel staging is a placeholder). As discussed above, the Merlin 2 is not the F1-class engine, so I figure it will be as big as necessary to put 50,000 lb. on orbit with 9 engines on the Falcon 9.

Musk doesn't strike me as the kind of guy who is angling for an engine development contract. He owns his engines and has assembled a top-notch development team for design. He isn't going to give up any control over his engines to the gov't and its various design bureaus! Musk is a resourceful guy and will find money elsewhere.

Nate Downes

I've run across a few interesting tidbits since this came out, so thought to share.

1) The Merlin-2 does borrow a lot of know-how on the Low Cost Pintle Engine, which the TR-107 is also based on, as the engineers who worked on the LCPE program are now split between both SpaceX and Northrup.

2) Pratt & Whitney/Rocketdyne have been defining a new engine based on the technologies they've gained as part of the RD-180 licensing program, called the AR-1000. It looks to be capable of 1.5 million lbf with an isp of 340.

3) Aerojet licensed the NK-33 from a Russian company, and now is producing an engine called the AJ-26. While at the moment it is using surplus NK-33's as a base, their future plans appear to include domestic production. What they have discovered is that the NK-33's systems were capable of far more performance than the original Soviet-era engineers thought possible, and can reach 140+% of rated performance. We're not talking RD-180 performance, but when you consider that this is with a single thrust chamber, single turbopump system with the best T/W ratio out of any other engine, sit up and take notice. Two of them would beat the TR-107, with better thrust, isp and T/W.

This is an exciting time to be in space, I feel like we're coming out of a long, 5 year deep sleep.


Nate "Downix" Downes,

If you read the below article from 2002 on the P&W AR-1000 engine competing with Aerojet's AJ-26-500 NK-33 derivative for the NASA SLI contracts in 2002, then you will see that we're actually coming out of a 10-year deep sleep.

The only change is that SpaceX did not exist in April 2002 when this article came out, and that the AJ-26/NK-33 was not baselined for a NASA launcher (i.e. Taurus II for COTS) yet.

The article's discussion of the AJAX hydrocarbon-engine joint venture between Aerojet and P&W suggests that they could work together versus competing for SLS. The Air Force RBS flyback booster program is already saying it will demo both the AJ-26 and the RD-180 so it will be interesting to see if Aerojet and P&W really compete or if they decide to cooperate.



I think that the P&W AR-1000 derivative of the RD-180 might already have lost the competition with the Aerojet AJ-26/NK-33 for the NASA SLS. The below recent RFI request for the Air Force RBS program is now specifiying a 300,000-lb to 500,000-lb thrust engine to replace the RD-180 which would eliminate the AR-1000 concept.

SpaceX has some interesting responses to this engine request if your read the "Q&A responses" section at the bottom.

I am speculating that P&W will collaborate with Aerojet and Teledyne-Brown for production of the AJ-26/NK-33 and that P&W will be satisfied that Aerojet not compete for NASA SLS sole-source contracts to P&W for the J-2X and SSME. Aerojet has rights to the LH2 RD-0120 so they could protest P&W sole-source contracts for SSME.

The single chamber RD-191 is a better (and more modern) engine than the 2-chamber RD-180, and P&W and the Air Force probably do not want to spend the time and money to develop the AR-1000 as a single chamber gimballed RD-180 when this work has already been done on the Aerojet AJ-26 and on the similar performance RD-191 (which P&W probably has rights to).

If you look at the politics of Russian engine manufacture, it never made sense to manufacture both the NK-33 and the RD-191 (because they have similar performance), so once NK-33 engines go out of stock in Russia, the Russians will just switch to the RD-191. It would also make sense for the RD-180 production for American rockets to go away and for the RD-191 to be used in the future Russian Rus-M launcher. Re-starting NK-33 production in Russia has never been a serious option, because the company and the engineers behind that engine have long retired or died. The RD-191 is in production, and it like the AJ-26, has the gimbals and recent successful test history that the NK-33 lacks.

This means that American Atlas V and Air Force RBS both need Aerojet's AJ-26 or they need a new Russian agreement to co-produce the RD-191. It makes a lot more sense for P&W and Aerojet to work together and manufacture the AJ-26 in Alabama.

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