SpaceX is aiming to return to flight on January 8th, as the company has officially determined what caused one of its Falcon 9 rockets to explode on a Florida launch pad this past September. In an online update this morning,
SpaceX detailed the source of the rocket failure — a complex process
that involved broken carbon fibers causing super cold oxygen to ignite.
The company says it has identified all of the “credible causes” that may
have been responsible for this combustible interplay of materials, and
corrective actions have been taken to make sure the same accident
doesn’t happen again.
SpaceX was forced to ground all of its vehicles after the
accident, which happened in Cape Canaveral, Florida on the morning of
September 1st. The failure occurred as the Falcon 9 was being being
fueled for an upcoming static fire test — a routine procedure SpaceX
does before launch to see if the rocket’s engines are working properly.
During fueling, the Falcon 9 exploded in a huge fireball, leading to the
destruction of the rocket and the communications satellite it was
supposed to carry into space.
Video of the event
revealed that the explosion began toward the top of the rocket, and
SpaceX later narrowed down the source of the problem to the vehicle’s
upper oxygen tank. That’s the tank that stores the super cold liquid
oxygen propellant needed for the engine in the second stage, or the top
portion of the vehicle. Along with liquid oxygen, the tank also houses
three smaller vessels that store really cold helium. They’re called
COPVs, for composite overwrapped pressure vessels, and they’re
responsible for pressurizing the tank during flight; the helium from
these vessels fills the empty space left behind by the oxygen when it
leaves the tank. It seems that the materials used for these helium
pressure vessels may have had a bad reaction with the oxygen in the
tank.
The vessels are made up of an aluminum liner surrounded
by a carbon fiber composite material. SpaceX was able to recover some of
the debris from the accident, and the company found something strange
about the COPVs. Something had caused the vessels’ aluminum liners to
scrunch up, creating buckles in the material. The most likely scenario,
according to SpaceX, is that some of the liquid oxygen in the tank
pooled into these buckles and got trapped there. Then, some of the
carbon fibers wrapping the helium vessel may have snapped, causing
friction that ignited the trapped oxygen. Additionally, the helium in
these vessels is incredibly cold too — so cold that it may have caused
the pooled liquid oxygen to turn into a solid. And solid oxygen has an
even greater chance of combusting due to friction.
The process more or less matches CEO Elon Musk’s explanations
for the failure last year. SpaceX says its accident investigation team —
which collaborated with the Federal Aviation Administration, NASA, the
National Transportation Safety Board, and the US Air Force — poured over
3,000 channels of data to figure out what happened. That may seem like a
lot of information, but the timeline of the accident was incredibly
brief. From the first sign of trouble to the loss of the vehicle, the
entire event lasted just 93 milliseconds. A week after the accident,
Musk said that the failure was shaping up to be the “most difficult and complex” one
the company has ever had, noting that there was no apparent heat source
for the explosion. In the end, SpaceX identified a number of possible
causes for the failure, all of which involved the pooled oxygen
scenario.
Now that the most likely cause for the failure has been
identified, SpaceX says it is implementing a number of short- and
long-term changes to avoid a similar situation in the future. For one,
SpaceX is going to load warmer helium into the pressure vessels,
apparently to avoid turning any of the liquid oxygen into a solid.
Additionally, the company will also return to a previous way of loading
helium that’s been shown to be successful before. As for the long-term,
SpaceX says it will be creating a new design that prevents the helium
vessels from buckling, though the company did not specify what those
design changes will be. It’s still unclear exactly what caused the
buckling in the first place.
With its accident investigation over, SpaceX’s next
planned launch is less than a week away. The flight will put 10 small
probes into orbit for satellite operator Iridium. The launch will take
place from SpaceX’s site at Vandenberg Air Force Base in California,
though an exact time for the flight has yet to be announced. If the
flight does occur this weekend, it will be a remarkably short turnaround
for the company. It took SpaceX six months to return to flight after
one of its rockets exploded during launch in June 2015.
Source : TheVerge
0 komentar:
Post a Comment