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In this Tweet (dated 11 Sept 2013) Peter de Selding reported that Gwynne Shotwell of SpaceX said:

SpaceX's Shotwell: We're building 7 Falcon 9 fairings/yr now, 15 in 2014, & 4 engines/week rising to at least 5/week by January.

But I was wondering what they mean by 'engine'. First thought is Merlin 1D since they need 10 per Falcon 9 launch (9 on the first stage, 1 on the second/upper stage). But 4/week is 208/year. 5/week is 260/year.

That is vaguely 20 to 26 cores a year, and they are clearly not anywhere close to using that many engines a year. At best they are aiming for 8 launches in 2014, and maybe one Heavy, which is only 80 to 108 engines in 2014.

At some point, stockpiling Merlin 1D's gets to be counter productive.

On the other hand, each Dragon has 4 quads of Draco thrusters, with a total of 18 Draco total on a Dragon. Dragonrider (manned Dragon) is reported to have 8 Super Draco thrusters. Which seem would be on top of the 18 regular Dracos.

In that manner, a single Dragon would need 18 engines, ignoring the launcher, and a manned Dragonrider would likely needed 26 engines.

In 2014 they are aiming at 3-4 Dragon flights, plus a pad abort (Of a Dragonrider config), which would mean 54-72 Draco's just for the CRS missions and 8 Super Dracos + 18 Dracos for the pad abort test. So about 98 non-Merlin engines just for the manifested Dragon flights.

If they aim for 8 Falcon 9 launches (all V1.1 so all Merlin 1D's) that is 80 Merlin 1Ds and possibly as many as 98 Draco/SuperDracos. That nets out around 178 engines used up in 2014.

If so, it is kind of cheesy to classify a Draco (90 lbs (not kilo-lbs, just simply 90 lbs) with a 145,000 lb thrust Merlin 1D or a 75,000 lb Super Draco.

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According to Aviation Week, it's 4 Merlin 1D engines per week. The same article says they're planning 12 Falcon 9 launches in 2014.

In October 2014, SpaceX announced they'd completed the 100th Merlin 1D. According to that article, build tempo was 4 engines per week at that point, and 80 Merlin 1Ds had flown by then.
This engine was slated to be flown on a flight in early 2015.

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    $\begingroup$ So 208 engines a year? 12 F9 launches only uses up 120 engines. Where do you STORE 88 engines, long term? They are not 'small'. $\endgroup$
    – geoffc
    Oct 21, 2013 at 17:29
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    $\begingroup$ According to their launch manifest, there's also a Falcon Heavy planned for next year, so they need 28 engines for that in the first quarter. $\endgroup$
    – Hobbes
    Oct 22, 2013 at 7:44
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    $\begingroup$ It's 1.5 m^2 per engine (x a few meters high), so they won't run out of room at their factory just yet. $\endgroup$
    – Hobbes
    Oct 22, 2013 at 11:56
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    $\begingroup$ How many are 'consumed' by testing? If I built engines, I sure would want to test them past the official operating specs to see how much tolerance they they have, what parts are the weakest, etc. $\endgroup$
    – user10509
    Oct 5, 2015 at 10:09
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    $\begingroup$ Add to that number the engines which failed to pass tests, engines destroyed in destructive tests, engines failed from moment one because they were used in "calibration runs" of the equipment and so on. I doubt they ever claimed they build 4 WORKING engines per week... $\endgroup$
    – SF.
    Apr 13, 2016 at 10:46
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Revisiting this question 4 years later, it seems clear that while they had this estimate of the engine build rate, they did not hit it.

There was an Instagram post of the 400th completed engine Dec 2017. So they clearly did not hit this run rate, nor sustain it if they meant Merlin engines.

However, in that interim they have launched 45 Falcon 9 flights, which consumed 450 engines. Except of course 4 of those missions (as of this writing) were reflown first stages, freeing up 36 engines. Some of the early landed vehicles, are thought to have had engines removed and used on other launches for testing reuse.

The change to successful reuse is likely a major change for SpaceX. No doubt they planned for it, expected it, but had to plan as well for a failure to achieve it, and thus build as if there is no tomorrow.

Conversely with 18 launches in 2017, and a clear push to increase that yet again in 2018 as well as multiple Falcon Heavy launches planned, the demand for engines may spike initially as enough Block 5 builds are completed to fill out the fleet. Falcon 9 - Block 5 is claimed to support very rapid reuse with minimal refurbishment, as the penultimate design based on experience from landing 20 stages, and reflying at least 4 (more every month!)

With the announcement that part of the business plan for Mars will be to fund the BFR/BFS development by moving all resources to BFR and away from Falcon 9, then moving all the business (launch of satellites, ISS missions, etc) to BFR once ready, we can assume that engine build rate will slow down (for Merlins, of course Raptors will scale up, especially since each BFR needs 31 and BFS needs 7).

It may be this was an aspirational goal to reach a build rate, but not necessarily run at that rate long term.

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  • $\begingroup$ A lot of SpaceX's & Elon's comments do indeed need to be taken with a grain of salt... $\endgroup$
    – marked-down
    Jan 5, 2018 at 18:20
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Some engines will be used on the grass hopper platforms.

Some engines will presumably fail during qualification/smoke (pun not intended*) testing.

Some engines will end up in the stock pile for future launches.

But I am guessing most of the remainder will be used for R&D testing, while improving the design [Merlin C => Merlin D & Merlin D => Merlin E(?)]

i.e., tweak design, build engine, test performance etc, compare with simulations, rinse and repeat.

*Pun kinda intended a little bit.

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    $\begingroup$ Would be great if you could provide references for your statements, expand and clean up your answer. Guesswork is okay, as long as there are enough sources and calculations to make it educated. $\endgroup$
    – Deer Hunter
    Jun 3, 2014 at 5:58

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