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Musk Predicts Falcon 9 Return to Flight in Mid-December

By Doug Messier
Parabolic Arc
November 6, 2016
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SpaceX CEO Elon Musk told CNBC on Friday that investigators have found the root cause of the fire and explosion that destroyed a Falcon 9 booster on Sept. 1. The company expects to resume launches by the middle of December.

Musk, confirming earlier discussion about the investigation, said the failure involved liquid helium being loaded into bottles made of carbon composite materials within the liquid oxygen tank in the rocket’s upper stage. This created solid oxygen, which Musk previously said could have ignited with the carbon composite materials. However, he did not go into that level of detail in his CNBC comments.

“It’s never happened before in history, so that’s why it took us a while to sort it out,” Musk said, adding that SpaceX has been working with NASA, the U.S. Federal Aviation Administration and commercial customers on the accident investigation. “This was the toughest puzzle to solve that we’ve ever had to solve.”

…SpaceX’s last public statement about the accident investigation, published on its web site Oct. 28, said that the company had narrowed its focus to one of three helium bottles inside the liquid oxygen tank that burst, noting it was able to replicate the tank failure with helium loading conditions. “The root cause of the breach has not yet been confirmed,” the company said at the time.

Meanwhile, more details are emerging about safety concerns related to SpaceX’s plans for its Crew Dragon spacecraft, which is designed to fly NASA astronauts to the International Space Station beginning in 2017 or 2018.

Tom Stafford, chairman of the NASA International Space Station Advisory Committee, expressed concerns about SpaceX’s plans to fuel the rocket with the crew aboard Dragon and the company operating the launcher’s Merlin 1D engines “outside their design input conditions.”

Stafford wrote that the committee unanimously believes SpaceX’s plan to load astronauts aboard the Crew Dragon before fueling the Falcon 9 booster is counter to safe practices that have been in place for more than 50 years.

“Pump-fed chemical engines require a sufficient and consistent input pressure to reduce the likelihood of cavitation or unsteady flow operations. We are concerned that there may be insufficient precooling of the tank and plumbing with the current planned oxidizer fill scenario, and without recirculation there may be stratification of oxidizer temperature that will cause a variation in the input conditions to the oxidizer pump,” the letter read.

“In summary, we are deeply concerned about introducing the practice of fueling with the crew onboard, and about the lack of even a recirculation pump for oxidizer conditioning on Falcon 9,” the letter added.

The Wall Street Journal also reports that ISS Advisory Committee members had expressed concerns about the design of the booster at a meeting last week.

The Falcon 9 booster, according to industry officials, also is the only large rocket world-wide in decades with helium bottles installed inside its liquid-oxygen tanks. During launch, the helium inside the bottles is released into the tank to maintain pressure while the liquid oxygen is consumed….

At the same meeting, Joseph Cuzzupoli, a former senior NASA manager who worked on the agency’s Apollo, Gemini and space shuttle programs, also expressed misgivings about SpaceX’s plans and the lack of NASA response. “Are we in the dark on this whole thing?” he asked.

Mr. Cuzzupoli told the committee that installing helium containers within fuel tanks—which entails putting wiring, sensors and tubing inside a potentially explosive environment—is “very unusual in my world, in my experience.” Such designs, he said “have been a no-no ever since Apollo.”

In 1970, a spark from an exposed wire inside an oxygen tank caused a life-threatening fire on board Apollo 13, bound for the moon. The crew managed a safe return to Earth, but NASA changed designs to prevent a similar incident.

On Nov. 1, NASA released a statement sttessing the space agency’s rigorous review process for any vehicles flying astronauts.

“The agency has a rigorous review process, which the program is working through with each commercial crew partner,” the statement reads. “Consistent with that review process, NASA is continuing its evaluation of the SpaceX concept for fueling the Falcon 9 for commercial crew launches. The results of the company’s Sept. 1 mishap investigation will be incorporated into NASA’s evaluation.”


17 responses to “Musk Predicts Falcon 9 Return to Flight in Mid-December”

  1. savuporo says:

    Is that prediction based on similar science that planned Falcon Heavy launch in 2012?

  2. windbourne says:

    What does that have to do with this story? Absolutely NOTHING.
    This is stafford’s job to be concerned about astronauts.
    Personally, I am happy that he is doing it.
    However, as somebody else pointed out, NASA will likely have to make changes, since it is actually SAFER for the crew to be in the rocket prior to fueling. After all, once it is fueled, then really does not make sense to put ppl next to the rocket with no chance of getting out.

  3. Pete Zaitcev says:

    Cuzzupoli is a know-nothing moron. Every rocket engineer who knows anything always installs helium bottles into the LOX tank, because you can stuff more helium in there this way. Not only Falcon, but also Angara, CZ-5, and Antares are done this way. The difference is that nobody uses COPV and nobody pumps _liquid_ helium in there.

    • patb2009 says:

      LHe is hard to keep in the lox… The heat transfer boils it.

    • Jeff2Space says:

      The composite overwrap on the outside of the COPV isn’t completely pressure tight, so a bit of LOX seeps into the composite. The problem they experienced is that the (much colder) liquid helium inside the COPV cooled the LOX so much that it turned solid inside the composite. This was very bad since this now becomes an ignition point. Ever chomp down on wintergreen Lifesavers? That.

      The good news is that a process change on exactly how the tanks are filled will eliminate the problem by insuring that the COPV does not get so cold that solid oxygen forms.

  4. NewSpace Paleontologist says:

    I am a rocket engineer and I do not know that you always install the helium bottles in the lox tank. I am probably a moron.
    For all those blindly criticizing the ASAP and Stafford, I am interested in your qualifications to do so.
    How launch vehicles have you loaded?
    How many manned launch vehicles have you loaded?
    How many times have you been responsible for crew escape?
    How many times have you been a member of or testified before a incident committee?

  5. windbourne says:

    Actually, this could lead to the HE tanks getting some sort of a cover that prevents any possible mixing of LOX into the tank siding.
    So, that is not a bad thing.

    In addition, this might lead to safety changes since it makes sense for the crew to be in the capsule waiting while fueling is going on. I think that this will be seen as being much safer over the long haul, esp. since the capsule is rated to do a pad abort.

    It will be interesting to see how Musk plans to do abort system for BFR/BFS.

  6. publiusr says:

    Ironically, the Energiya hydrogen engines were less troublesome than the RD-17X series –and yet Glushko hated hydrogen.

    Musk wanted to avoid hydrogen for its cryogenic headaches–which the super-chilled LOX caused anyway.

    An interesting quote:

    “In most American designs, a gas-generator engine would dump the exhaust from the turbines overboard. In the case of the M-1, the resulting exhaust was relatively cool, and was instead directed into cooling pipes on the lower portion of the engine skirt. This meant that liquid hydrogen was needed for cooling only on the high-heat areas of the engine —the combustion chamber, nozzle and upper part of the skirt— reducing plumbing complexity considerably”

    Now M-1 was also to use helium to spool up the engines. Would not an LH2 tank interior be a little more friendly to a COPV?

    Then too, maybe we will have metal hydrogen fuel

  7. publiusr says:

    Not a libertarian. It’d take NASA to develop this. Musk and Bezos seem to want to avoid LH2. Sad, that.

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