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SpaceX completes 33-engine static fire test today of Superheavy prototype #7

Two seconds after ignition
Today’s Superheavy static fire test

SpaceX today successfully completed a 7-second-long static fire test of 31 of 33 Raptor-2 engines at the base Superheavy #7. The test ran for its full duration, and it appears no damage occurred to the launchpad. One engine shut down prior to test, and one shut down prematurely during the test. If this had happened during launch, the booster would still have had enough energy to get Starship to its required velocity to reach orbit.

The company will now have to analyze the test to determine whether it was sufficient to proceed to a March orbital launch. Certainly they will roll the booster back to the assembly building to exchange out the two engines that misfired.

All in all, it appears an orbital test flight of Starship could occur sometime in the next two months, assuming the FAA gets out of the way and issues the launch license.

Propellant loading is underway, and a rough time estimate for the actual static fire test is now 3 pm (Central).

Musk has now confirmed in a tweet that they are going to proceed to the test. It now appears that they have almost completed propellant loading. It appears they have filled the oxygen tanks, but not the methane tanks, and will probably not fill the methane tanks entirely for the test itself.

Original post:
No specific schedule has been announced of SpaceX’s attempt today to complete the first full 33-engine static fire test in Boca Chica of its seventh prototype of Superheavy, but a live stream is available from I have embedded that live stream below.

The test will validate numerous systems, including the ground systems, the launchpad, the engines, and the systems for igniting all 33 in the proper sequence. Starship prototype #24 is not stacked on top of Superheavy in order to prevent any damage to it in case this test goes ugly. If so, SpaceX already has Superheavy prototype #9 ready to go in the nearby assembly building.

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  • geoffc

    If they fire successfully today, this is going to redefine what “epic” means.

    More engines than a N-1.

    More thrust than Shuttle/SLS/SaturnV/N-1.


  • geoffc

    And they fired right around 4:14PM EST. And it is still standing afterwards. Not sure if they fired all 33 but it looked good from the cameras.

    Woo! Hoo! Several seconds.

  • geoffc: Refresh your browser. I have updated the post to show the results, 31 of 33 fired as planned.

  • Patrick Underwood

    So, still most engines ever fired, and still (almost certainly) the most powerful rocket firing in history…

  • sippin_bourbon

    Most since N1, and no Foom, boom, bang.

    I will take it

  • Stephen Richter

    regarding damage to the launch pad, can super heavy initially fire at half thrust until the rocket has cleared the launch tower?

  • Patrick Underwood

    Stephen Richter, the stated thrust/weight is 1.5, halving the thrust would make it .75 so it wouldn’t leave the ground.

    They might take a few percent off for a few seconds, but I doubt that too. Probably hurts their payload numbers.

    Best to just ensure the GSE can handle it!

  • Ray Van Dune

    “regarding damage to the launch pad, can super heavy initially fire at half thrust until the rocket has cleared the launch tower?”

    In a word, no. With a thrust/weight ratio of 1.5 at full thrust, the acceleration of the Superheavy rocket would be 1/2 G. At half thrust there would be – 1/4 G, so you would just sit there and go nowhere!

    More to the point, if you reduce the thrust to where the ratio is just above 1.0., the rocket would climb, but much slower, giving the exhaust more time to do damage to the tower!

    In general, taking off with anything less than full thrust also wastes propellants, with the rocket spending more time working against gravity than it would if it used maximum thrust.

    Just think of it as gravity is stealing a constant ~10 meters per second of acceleration from the rocket. If you do anything to slow the acceleration of the rocket down, gravity will just have more time to steal acceleration from the total amount of acceleration your propellants can provide!

  • Sippin_bourbon

    I would have thought they would try a SH hop and catch first…

  • Doubting Thomas

    At one half g acceleration, give a T/W of 1.5, it will clear the 395 foot tower in about 7 seconds I think and will be traveling about 90 mph (~140 fps) at that point.

    16 seconds after launch, the stack will be moving greater than 175 mph at over 2,000 feet in the air.

    Of course, all these numbers are approximate (and low) since the acceleration of the stack will increase continually as the fuel burns making the T/W ratio higher as the weight of the stack decreases due to fuel expenditure.

  • Richard M

    I think the NSF guys are right: A March launch attempt is a real possibility now.

    I know we all get het up about the FAA license. The good news is, Shotwell says the FONSI mitigations are well in hand, so the remaining variable is whether the data from the static fire looked favorable – that data will have to be presented to the FAA with the application, after all. That doesn’t mean there won’t be bureaucratic fumbling, but right now it looks like SpaceX has done pretty much everything to make the application easy to approve.

  • Concerned

    Ray Van Dune said: “At half thrust there would be – 1/4 G, so you would just sit there and go nowhere!”

    You would only sit there if the launch clamps were still in place. If not, you’d be going somewhere alright.

  • Edward

    Concerned wrote: “You would only sit there if the launch clamps were still in place. If not, you’d be going somewhere alright.

    Ray Van Dune‘s comment was that there would not be enough thrust to get off the pad, not enough by a factor of 1/4G. The full up Starship configuration, with propellants, weighs about 11 million pounds, and the Raptor engines would provide around 16 million pounds for liftoff. Half thrust would result in only 8 million pounds attempting to lift 11 million pounds, and that is three million short of what is needed to lift off the pad, even without clamps. The thrust to weight ratio is not enough with half thrust.

    I agree with Ray that a slower liftoff would give more time for acoustic and thermal damage to the pad and tower. Perhaps they are designed for minimal damage, but it is counterproductive to push it.

    Also, Doubting Thomas‘s calculations are similar to ones that I did a few months ago. I think that I noted back then that zero to 90 mph in seven seconds is a nice sports car.

  • John

    That was cool!

    Better to have the engines shut down than kabooming.

    33 remote chances of a kaboom can add up.

    Likely the analysis will determine the ‘why’ of the shutdowns and if it could be an issue that would effect more engines on a longer burn. It’s not necessarily the engine itself, there’s presumably a ton of upstream plumbing, pumps, wiring, sensors, etc.

  • Jeff Wright

    The gap in the still marks the engine that was down? Its counterpart would have to be directly opposite and center engines not running to explain the break in that curtain of flame-what you need to examine a KORD type test?

  • Ray Van Dune

    It is a common mistake to think that a thrust /weight ratio of 1.5 means that the rocket will accelerate at 1.5 G.

    No, gravity “steals” 1.0 G all day long, so you will only accelerate at 0.5 G. Thus at half thrust, a ratio of 0.75, you will make lots of heat and noise, but no progress upward.

  • Doubting Thomas

    Edward – Didn’t see your post but great analogy. Hoping next month will be magic.

  • Edward

    Doubting Thomas,
    You wrote: “Didn’t see your post but great analogy.

    That’s OK, and thanks. I forgot about it until I saw yours, so why shouldn’t everyone else have forgotten about it, too? Besides, we should all be reminded of how quickly Starship should rise. The Saturn V was much slower, about 1/4 G, but the Space Shuttle was about as fast as Starship should be.

    Next month should be spectacular, no matter what happens.

    Performing this test without straps to hold it down, as they do with the Falcon 9 booster tests, tells me that one of two things went on here. Either they beefed up the pad hold-downs and the base of the booster 7 so that the lighter rocket would stay on the pad, OR they did not bring the engines up to full thrust.

    If, during launch, one engine quits, it is not necessary to shut down the engine on the opposite position. The torque resulting from the imbalanced thrust (less thrust on the side with the failed engine) can be countered by steering the central engines to compensate for the torque, thus the rocket would not pinwheel out of control and would continue to have most of its thrust.

    It is unlikely that an engine will explode or cause an explosion, as happened to the Soviet’s N1 rocket. The engine controllers are programmed to shut down engines before they get into an explosive condition. However, the N1 engine controller was not well programmed to handle engine-out circumstances, and tended to cause the N1 to explode rather than prevent explosions. During one launch, an engine on the N1 had a problem, but instead of shutting down just that engine, the controller shut down all but a single engine; so the N1 fell back to the pad and exploded in a spectacular way. This test suggests that SpaceX’s engine controller is programmed better.

  • Jeff Wright

    Ah–that was the milk stool leg as the gap—I can’t see anything on that flip phone.

  • Trent Castanaveras

    Edward said: “Either they beefed up the pad hold-downs and the base of the booster 7 so that the lighter rocket would stay on the pad, OR they did not bring the engines up to full thrust.”

    Good catch!

  • Richard M

    Good news: It looks like the new fondag concrete base under the Orbital Launch Mount held up well. Zack Golden: “There was a lot of debris raining down during yesterday’s static fire. It appears all of the concrete that was blown away came from outside of the perimeter of the new Fondag RS pad under the OLM. Aerial photos will hopefully be available tomorrow.”

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