[FPSPACE] Space X launch failure details released

Peter Pesavento pjp961 at svol.net
Fri Jul 24 18:13:03 EDT 2015



JULY 20, 2015



On June 28, 2015, following a nominal liftoff, Falcon 9 experienced an
overpressure event in the upper stage liquid oxygen tank approximately 139
seconds into flight, resulting in loss of mission. This summary represents
an initial assessment, but further investigation may reveal more over time.

Prior to the mishap, the first stage of the vehicle, including all nine
Merlin 1D engines, operated nominally; the first stage actually continued to
power through the overpressure event on the second stage for several seconds
following the mishap.  In addition, the Dragon spacecraft not only survived
the second stage event, but also continued to communicate until the vehicle
dropped below the horizon and out of range.

SpaceX has led the investigation efforts with oversight from the FAA and
participation from NASA and the U.S. Air Force.  Review of the flight data
proved challenging both because of the volume of data -over 3,000 telemetry
channels as well as video and physical debris-and because the key events
happened very quickly. 

>From the first indication of an issue to loss of all telemetry was just
0.893 seconds.  Over the last few weeks, engineering teams have spent
thousands of hours going through the painstaking process of matching up data
across rocket systems down to the millisecond to understand that final 0.893
seconds prior to loss of telemetry.

At this time, the investigation remains ongoing, as SpaceX and the
investigation team continue analyzing  significant amounts of data and
conducting additional testing that must be completed in order to fully
validate these conclusions.  However,  given the currently available data,
we believe we have identified a potential cause.

Preliminary analysis suggests the overpressure event in the upper stage
liquid oxygen tank was initiated by a flawed piece of support hardware (a
"strut") inside the second stage.  Several hundred struts fly on every
Falcon 9 vehicle, with a cumulative flight history of several thousand. The
strut that we believe failed was designed and material certified to handle
10,000 lbs of force, but failed at 2,000 lbs, a five-fold difference.
Detailed close-out photos of stage construction show no visible flaws or
damage of any kind.

In the case of the CRS-7 mission, it appears that one of these supporting
pieces inside the second stage failed approximately 138 seconds into flight.
The pressurization system itself was performing nominally, but with the
failure of this strut, the helium system integrity was breached.  This
caused a high pressure event inside the second stage within less than one
second and the stage was no longer able to maintain its structural

Despite the fact that these struts have been used on all previous Falcon 9
flights and are certified to withstand well beyond the expected loads during
flight, SpaceX will no longer use these particular struts for flight
applications.  In addition, SpaceX will implement additional hardware
quality audits throughout the vehicle to further ensure all parts received
perform as expected per their certification documentation.

As noted above, these conclusions are preliminary.  Our investigation is
ongoing until we exonerate all other aspects of the vehicle, but at this
time, we expect to return to flight this fall and fly all the customers we
intended to fly in 2015 by end of year.  

While the CRS-7 loss is regrettable, this review process invariably will, in
the end, yield a safer and more reliable launch vehicle for all of our
customers, including NASA, the United States Air Force, and commercial
purchasers of launch services.  Critically, the vehicle will be even safer
as we begin to carry U.S. astronauts to the International Space Station in



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