Falcon Heavy static fire test delayed again


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It appears that the first static fire test of the Falcon Heavy has been delayed again from today to later in the week.

There is no word on why the delay, but all indications suggest that they are going through the process step-by-step with great care. As they find things that need addressing they are addressing them, and that only when all issues are resolved will they go forward.

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7 comments

  • ken anthony

    Probably shouldn’t speculate but I’m guessing it’s a software issue related to the ignition firing sequence? Or something else completely different (weaseling!)

    They got 27 engines that all need to be able to shut down in less than a second if some sensor tells them so?

  • ken anthony

    Also, each core has it’s own independent electronics that have to talk to the other two cores. It wouldn’t do for some cores to shut down while others keep going.

  • Dick Eagleson

    Slowly, slowly, catchy monkey.

  • Michael

    Again I have found some reasonable comments regarding the Falcon Heavy static fire. I am beginning to appreciate this web site.

    https://www.teslarati.com/whats-causing-spacex-falcon-heavy-delays/

    I have been thinking about ‘go-fever’ and your own money; seems to have a calming effect. But then again this is the first time a whole Falcon Heavy is test fired all up so I do not blame them in sneaking up on the thing with great caution.

    It will fly when it flies and us rubbernecks be darned.

  • Localfluff

    If it blows up on the pad, that would be fantastic fireworks. The Soviet Moon rocket N1 is said to have produced the biggest non-nuclear explosion ever (or up until it happened?) It had a mass of 2800 tons, Falcon Heavy 1400 tons, kerosene in both cases. So from the armchair entertainment perspective it is a win-win. Just push the button! :-)

  • ken anthony

    SpaceX will learn from the proceedings, and they will be better off for it (although maybe less so financially…).

    Let’s see… the financial cost of delay vs. the financial cost of blowing up on the pad. Gee, I wonder which costs more???

    With BFR, they should probably do grasshopper tests before going orbital. Any bets?

  • Edward

    ken anthony asked: “With BFR, they should probably do grasshopper tests before going orbital. Any bets?

    Maybe, and they should have a landing pad built for the first launch, too, so it would be easy to do. However, since they aren’t doing that with Falcon Heavy I will side with “orbit or bust.” Unfortunately, it will take a few years before we know who got it right.

    Michael,
    Thank you for that link. I never did the math before, so I never considered just how much the launch vehicle shrinks due to the thermal contraction from the cold propellants. From the article: “In the case of Falcon 9’s massive 45 meters (150 foot) tall first stage, the scale of this contraction can be on the order of several inches or more

    LOX freezes around 55 Kelvin (-218 C) and kerosene around 233 Kelvin (-40 C). SpaceX is loading these as cold as they can so that it is as dense as possible in order to get the most potential energy into the tanks as possible. The coefficient of thermal expansion for aluminum (probably different for Falcon’s alloy) is around 0.000021 mm per mm per degree K. Since I do not know the length of each of the propellant tanks, I will assume that the LOX tank is twice that of the kerosene tank (it holds over twice the weight of O2 as kerosene) the length of the 45 meter rocket. But first I will subtract off the 5-ish meters of the Merlin engines and their support structure.

    Each tank has two domes, which reduce the length that the tanks are part of the skin of the rocket by about the 3.66 m diameter of the rocket, so the LOX tank is about 24 meters of the rocket’s length. I recall that they share a dome, with insulation, so I removed the dome height only once.

    Assuming that ambient temperature is 300 K (just about room temperature), it looks to me that the LOX shortens the Falcon 9 by about 123 mm and the kerosene by about 17 mm. This is a total of about 5-1/2 inches.

    My guess is that SpaceX is looking very closely at the strains and stresses and the differences between rockets as they load the cold propellants into the three different rockets. These differences may not be the reason for the delays, but they are a potential problem with the cross-supports at the top of the first stage. Loading the propellants evenly may be much more important than I had thought.

    The next question on your mind is: “how much do the diameters of the tanks shrink due to the cold propellants?” For the LOX, 19 mm, and 5 mm for the kerosene tank. That is a stress and strain that needs to be accommodated at the interfaces of the tanks with the rest of the rocket’s skin and structure.

    Ain’t rocketry fun?

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