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SYFY WIRE Bad Astronomy

SpaceX Returns to Flight

By Phil Plait

Over the weekend—on Saturday—SpaceX launched a Falcon 9 into space, successfully completing its primary mission of deploying 10 Iridium communication satellites.

The secondary mission? To land the first stage booster on a drone ship in the Pacific. And that happened perfectly:

How cool is that? What happened is that after boosting the second stage toward orbit, the first stage flipped around, performed an engine burn to slow down, flipped again, deployed the steerable grid fins, then (after much shorter burns of the main engine and some help with cold jets for attitude control) landed smack dab in the center of the drone ship Just Read the Instructions (the barges are named after sentient ships in the science-fiction novels of Iain M. Banks).* This was the first successful landing of a booster in the Pacific Ocean; an earlier attempt in January 2016 came close, but one of the landing legs failed to lock, the booster fell over after the soft landing, and then exploded (and you want to click that link; the video is really something).

This mission was important, marking the return-to-flight status for SpaceX after an explosion during fueling of a Falcon 9 in September. SpaceX traced the cause of that to a liquid helium tank in the second stage.

As my colleague Eric Berger at Ars Technica writes, the helium tanks are mounted inside the liquid oxygen tanks; as the oxygen is used up during launch, helium is released to maintain pressure in the tank. However, the liner wrapping of the helium tanks under a carbon fiber coating appears to have buckled in the extreme cold environment, letting oxygen in between the coating and the tank itself. Liquid oxygen isn’t flammable, but when it contacted the much colder liquid helium tank, it froze and combusted, causing the explosion. To prevent this from happening again, they’re returning to their “flight proven configuration” of the tanks for now (an older setup with warmer helium), and in the future will change the fiber wrapping to prevent it from buckling.

Berger also has an interesting article about SpaceX’s finances; it lost quite a bit of money ($250+ million) in the 2015 accident where a rocket was lost on its way to the space station but still has ambitious plans for more than two dozen launches this year alone. That includes tests for the first crewed flight, and the first flight of the Falcon Heavy, its next-generation rocket that will be the most powerful rocket in the world … though Blue Origin has its goals of building some pretty big boosters as well.

This should be a pretty exciting year for space exploration. Let’s hope it all goes well. In the meantime, congratulations to SpaceX for getting the planet underneath them once again.

*Correction, Jan. 16, 2017: I originally had embedded the wrong video, it was from an earlier launch. Also, I said the carbon fiber wrapping had buckled, when it was the aluminum liner under the carbon fiber that buckled.

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