A detailed look at SpaceX’s Raptor engine

Please consider donating to Behind the Black, by giving either a one-time contribution or a regular subscription, as outlined in the tip jar below. Your support will allow me to continue covering science and culture as I have for the past twenty years, independent and free from any outside influence.


Regular readers can support Behind The Black with a contribution via paypal:

Or with a subscription with regular donations from your Paypal or credit card account:


If Paypal doesn't work for you, you can support Behind The Black directly by sending your donation by check, payable to Robert Zimmerman, to
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652

Link here. This story confirms for me a thought I had had while I watched Elon Musk’s talk last week outlining his proposed Interplanetary Transport System: SpaceX is still a good long way from actually building this rocket, since they have barely begun developing the rocket engine. They have made excellent progress in engine development, but they have a lot to do, with many pitfalls certain.

I therefore think that the company will be relying on its Falcon 9 and Falcon Heavy rockets, with their Merlin engines, for many more years to come.



  • Cotour

    51 engines?

    Man that seems to be a lot of potential for complexity /malfunction.

  • Localfluff

    Cotour, F9-004 in 2012 lost one of its 8 first stage engines, but compensated for it to still deliver its primary cargo to the ISS. With 42 engines in the first stage, several engines can be lost without risking the mission. They haven’t had any serious engine problem risking an explosion. And I think there are economic arguments for mass producing hundreds of raptors instead of a handful gigantic engines.

    They’ve successfully test fired the raptor and built an interplanetary fuel tank. That’s pretty good progress, not far behind the SLS. Musk has previously said that they give priority to “the Mars project” instead of trying to make the F9 upper stage reusable. And that when the first F9 failed, they canceled work on Falcon Heavy until the problem was solved. The Falcon system was maybe just a pioneer for the Mars project and has a phase out plan. Someone suggested that there will likely be a less than super sized Raptor rocket replacing F9 in a few years.

    It is interesting how SpaceX goes brute force. Just larger engines, more engines, more fuel, larger rocket, even more fuel. And going to Mars in 3 months with propulsive landing. Does this really hold up in the rocket equation?

  • PeterF

    The sub-scale 1MN has already been tested and now just needs to be scaled up to produce a full scale Raptor. Perhaps this (operational) prototype can be reproduced for use in other applications? I can see an economic opportunity for SpaceX building engines for other companies…
    Do we know of any other companies that are currently having difficulty developing their own engines? A 225 klbf methane fueled engine would be relatively light and safe enough to sling under an aircraft for sub-orbital operations… Could SpaceX make a profit supplying hardware to other companies that are not attempting direct competition?

    With 42 engines in the first stage, I would be surprised if they all performed flawlessly during ANY launch. If they are built with a robust safety margin, shutdown of even several to balance the thrust could be compensated for by throttling up the remaining operating engines and extending the burn time. (Using the fuel that would have been burned in the malfunctioning engines)

    (In “The Martian”, they shut down the Ascent Vehicle boost according to the calculated mission profile MECO time even though they could tell it’s velocity and altitude were out of tolerance. Why wouldn’t they just let it keep burning till it ran out of fuel? At that point they already new they missed the window, what more did they have to lose?)

  • wodun

    They can get a lot done with the FH. Maybe they will even use Raptor for their 2nd stages before building the ICT.

  • Tom Billings

    “Does this really hold up in the rocket equation?”

    Yup! As long as the frackers keep bringing up cheap methane, or the clathrate drillers do, then the physical numbers will work. The fiscal numbers? Not even Elon knows for sure, as he keeps reiterating.

  • Tom Billings

    “They can get a lot done with the FH. Maybe they will even use Raptor for their 2nd stages before building the ICT.”

    Elon has said he will be focusing their engineering talent on ITS, instead of the upper stage for FH the Air Force wants so much. Yes, FH and Falcon 9 will continue to be the breadwinners in the family for at least 10 more years, and *somebody* has to bring in the revenue in that timeframe.

    Remember that not only are the operational people a resource that needs continuing development, and the engineering talent doing development, but Elon hinted at another resource as well. His own time. He spends less time on SpaceX than he’d like, already. To divide his time further, with another stage to develop, seems to be something he has decided not to do. The AF may yet find ways to change his mind, but these will be crucial years for development, at the same time he has mentioned the time he wants to spend with his kids.

    Elon is finding his own limits, as well as whatever limits there are to Raptors.

Leave a Reply

Your email address will not be published. Required fields are marked *