Friday, February 26, 2021

SpaceX Swaps “Suspect” Raptor, Retests in Under 48 Hrs

At the end of Wednesday's column on the SpaceX prototype elevator, I mentioned that on Tuesday they had static fired SN10 but that it apparently did something wrong because one of the three Raptor engines was swapped out Wednesday.  In a tweet, Elon Musk had said one was “suspect” and needed to be swapped out.  

Bearing in mind that SpaceX is intending these engines to be manufactured and used in numbers unprecedented for any rocket engine and you can understand how they might have a ready inventory and then test all three again.  The engines that were fired yesterday should have zero degradation from running for a couple of seconds, so put in the new one and test all three. 

That's what they did yesterday.  The test subjectively looked and sounded better to me, just based on seeing bunches of these static firings

For some reason, I couldn't get this to start at other than time = 0.  If you set the bar to 2:10 you should be less than 10 seconds before ignition. 

If you've seen any of the chatter about Elon Musk and the crypto currency called Dogecoin, you might appreciate the joke on the new Raptor waiting to be installed.

"A Raptor Engine labeled “Under Doge” (serial number unknown) was delivered to the Starship build site in Boca Chica just now, and Raptor SN56 (green nozzle) took its place on the Raptor van, presumably headed back to Hawthorne or Mcgregor.
@NASASpaceflight"  from Twitter user Jack Beyer.

Given how SpaceX turned around SN10 from a questionable static firing to an apparently successful firing within 48 hours, it might catch your attention that the SLS second static firing test (Green Run Test 2) has slipped out to NET Mar 16. (NET = No Earlier Than)  The SLS was test fired in January and aborted at 67 seconds over a "finicky" valve.  The valve was repaired and during further testing, another valve in the same section failed.  Replacing an engine on Starship took less than a day.  Replacing a valve on SLS will take three weeks. 

In any comparison like that, Starship is going to look better than SLS.  Starship has been designed to be worked on easily at this phase in its development when SpaceX uses the "test to failure, fix, repeat" mantra.  SLS has not been designed for any of the rapid turnaround features that Starship has.  Even SpaceX’s Falcon 9 rockets, the world-standard for reusable orbital-class boosters, would have a hard time challenging that engine swap turnaround.  My guess is that it would take less than a week to swap engines in the Falcon 9, too.   I think we've seen it before. 


  1. Well done, SpaceX!

    Designing for Serviceability is an art unto itself.

  2. Yaknow, it's almost like... SpaceX is trying to make a consumer product that is intended to be mass-manufactured rather than a carefully hand created one-of.

    SpaceX - Making Cadillacs instead of Rolls Royces, except the SpaceX Cadillacs will be so far superior to all the hand-made space-rolls it makes the space-rolls look like, well, 1960s architecture instead of a Spaceship of Tomorrow.

    1. Naw Beans, I will drop back 108 years for my comparison and state that SpaceX is not trying to build a Cadillac but a Ford. No other company is trying to crank out space craft like SpaceX and see a closer tie to Ford's development of the assembly line for automobile manufacture instead of the team built automobile. Elon want's mass manufactured, rapidly reusable space craft that afford access to outer space by many more that the government and elite few that have millions/billions of dollars to spend.

      While off the subject this reply, there are mounting calls for the cessation of the SLS program both from the Left and the Right. Maybe NASA can become to space flight what they have become to aviation providing research and early development.

    2. Yep. They're building a Model T for space.

    3. They're building a very high-class Model T.

      Just look at their Dragon capsule in comparison to the Orion or the Boeing CST100 whatever. Completely beautiful, flowing lines, careful craftsmanship, nothing to bump into or cut yourself on.

      Yes, a Ford. But a beautiful, strong, well-thought out, well designed Ford.

      Thus the Cadillac (old school Cadillac) comparison.

  3. CPAC Day 2 Live Stream

    ps. could you add CC to your blogroll?

  4. I live about 18 miles from their site in McGregor, Tx. We hear them testing several times a week. Would love know their schedule so I could position myself accordingly

  5. Will we have an engine named Sweet Polly Pureburn to go along with the Under Doge?