Falcon 9 explodes on launchpad

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During a standard prelaunch static test firing today a Falcon 9 rocket exploded on the launchpad.

Obviously, this will put a hold on all of SpaceX’s upcoming efforts.

  • Falcon Heavy: Since the explosion was almost certainly caused by a failure in the first stage, they will have to hold off that first Falcon Heavy demo launch scheduled for this fall, since it uses three first stages strapped together.
  • Reused Falcon 9: Similarly, the first launch of a recovered Falcon 9 first stage, also set for the fall, will likely have to be delayed until they determine what went wrong today.
  • Reused Dragon: NASA had indicated that one of the cargo missions to ISS next year would reuse a previously flown Dragon. Though this explosion has nothing to do specifically with Dragon, the capsule is launched with a Falcon 9, and thus cannot fly until this investigation is over.
  • Falcon 9: SpaceX had been attempting this year to up its launch rate to more than one per month. That will now not happen.
  • Red Dragon: SpaceX has said it plans to fly a test Dragon to Mars in 2018, the next launch window. While this explosion will delay the company’s plans over the next year, I expect SpaceX will not cancel that 2018 launch. They have enough time to investigate this failure and fix the cause without missing that window.
  • Elon Musk’s Mars speech: Finally, Musk is scheduled to make a major speech on September 26 at the International Aeronautical Congress (IAC) in Guadalajara, Mexico, outlining his company’s future plans to fly to Mars. He almost certainly will have to rewrite that speech.

This launchpad explosion is bad news for SpaceX but it is also very puzzling. I cannot remember the last time a rocket exploded on the launchpad during a static fire test. Failures have in recent years always occurred during the actual launch, when the rocket is flying and is thus exposed to large dynamic forces which can cause the engineering to go screwy. For a rocket to explode at the moment it ignites its engines suggests a very fundamental design fault, which seems unlikely considering the number of launches and static fires SpaceX has completed with the Falcon 9, including numerous prelaunch tests of the rocket’s first stage, both on the launchpad and at the company’s test facility in Texas prior to shipment to the launchpad.

Update: SpaceX has now said that the problem occurred near the rocket’s upper stage during fueling, prior to the actual ignition of the engines.

This news is both good and bad. The good news: It means that the failure had nothing to do with the much tested Merlin engines, which would have suggested a fundamental design flaw previously unseen. That is now clearly not the case. The bad news: The update suggests that the problem might be related to SpaceX’s high density, high pressure fueling, which by lowering the temperature of the tanks allows them to load more fuel and oxidizer. This novel approach, only introduced last year in order to give the rocket greater fuel capacity, might have a design problem that they had not anticipated.


  • Des

    It is most likely a fault in the rocket, but it is possible that a problem with Ground Equipment could have caused the explosion.

  • Jim Davis

    My understanding is that the problem occurred well before engine ignition.

  • Willi

    Oh, my, the payload was also destroyed.

  • Jim Davis: Do you have a link or source for this understanding?

  • Never mind. I have found the source and specific information and posted it as an update.

  • Kyle Kooy

    The weather didn’t look too great, I wonder if there was some atmospheric pressures that they didn’t account for, or maybe the rocket wasn’t grounded properly and some static in the air got it or something, looks like there’s a tornado warning out there.

  • Alex

    Maybe the common bulkhead, which separates LOX from RP-1, has failed by overlood, causing a rapid mixture of both and ignition. The second is the lightest rocket stage, in terms propellant mass fraction, ever built. Maybe too less robust. Why to hell did the make the test with the payload on board?

  • Alex asked, “Why to hell did the make the test with the payload on board?”

    For SpaceX it has been standard procedure to test fire the engines and the first stage in Texas, then ship it to the launch site where everything is assembled for one last dress rehearsal static fire test just prior to launch. That last test is actually no different than a planned launch abort, and if something goes wrong here it is the same as something going wrong during the actual countdown.

    It is possible they may change this procedure after this failure, but I think that would be a mistake. This failure was not because of the static fire test, it was because of some problem that was there already in the rocket. Moreover, to do this dress rehearsal countdown without the payload would cause enormous delays and cost increases, neither of which would accomplish anything.

  • brendan

    Oops! And here I thought the payload wasn’t on board… My bad!

  • Robert: nice reporting and analysis of a major event in commercial space. Thank you.

  • Alan Glenn

    I smell Russian hackers

  • Alex

    Mr. Zimmerman: Yes, SpaceX left payload at launcher for this wet dress rehearsal, because SpaceX has no real launch tower, only a strongback. Therefore, there a not able to retrieve the payload from vertical standing rocket and have to lower the whole launcher to horizontal and drive it back to workshop in order to remove satellite. That is the backside of saving a real launch tower (and money).

  • Dick Eagleson

    SpaceX doesn’t need a launch tower to handle comsats, cargo Dragons or most other payloads. These can all be integrated with the rocket horizontally, Russian-style. There is an existing tower at LC-39A that SpaceX will use, suitably modified, to do both Dragon 2 missions and launches of national security payloads that require vertical integration with the rocket. Horizontal integration is, in general, both faster and lower in cost than vertical integration.

    Comsats are designed to be “no-pref” about their integration orientation. Designing this way allows a given bird to ride uphill on any launcher. SpaceX and the Russian Proton default to horizontal integration. ULA and Arianespace do vertical integration.

    Sometimes SpaceX does its hot fire tests with the payload atop the rocket and sometimes without it. My understanding is that it’s up to the customer which way they want this done. If the test is done with the payload attached, it is not removed once the rocket is defueled, laid back down and transported back to the horizontal integration facility until the actual date of launch. Additional last-minute pressurized cargo items are sometimes added to Dragon capsules between the static fire and the launch, but this doesn’t require the Dragon to be detached from the rocket. For rockets hot-fired without their payloads, the payload is attached to the rocket after the hot-fire once it has been rolled back into the horizontal integration facility.

  • Alex

    Dick Eagleson: I am fully aware of all this. Please not, that Russian launcher are horizontally integrated but use also in addition complex launch towers, which allows access to different level to rocket and payload in vertical launch positions. I would never risk a payload for test firings, because outcome of test firing is much more uncertain as flight itself, otherwise it (test firing) would not needed. I am quite sure that SpaceX is going to adapt its procedure afterwards incident.

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