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| Credits: SpaceX |
From the July 20, 2015 press release:
“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 integrity.
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 2017.”
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SpaceX dixit:
“This will be the first flight test of SpaceX’s revolutionary new launch abort system, and the odds of encountering delays or issues are high. Fortunately the test doesn’t need to be perfect to be valuable—our primary objective is to capture as much data as possible as the data captured here will be key in preparing Crew Dragon for its first human missions in 2017.
A Pad Abort Test is a trial run for a spacecraft’s launch abort system (sometimes called a launch escape system). This system is designed to quickly get the crew and spacecraft away from the rocket in the event of a potential failure. It is similar to an ejection seat for a fighter pilot, but instead of ejecting the pilot out of the spacecraft, the entire spacecraft is “ejected” away from the launch vehicle.
Previous launch abort systems have been powered by a rocket tower mounted on top of the spacecraft. During an emergency, the tower would ignite and essentially pull the spacecraft to safety. This works well while the spacecraft is on the launch pad and for a few minutes into ascent, but once the vehicle reaches a certain altitude, the system is no longer useful and must be discarded. SpaceX’s launch abort system, however, is integrated directly into the spacecraft. This means Crew Dragon will have launch escape capability from the launch pad all the way to orbit.
Instead of a separate rocket tower mounted on top of the spacecraft, SpaceX’s launch abort system leverages eight SuperDraco rocket engines built into the walls of the Crew Dragon spacecraft. The SuperDracos are capable of producing 120,000 lbs of axial thrust in under a second, which results in transporting the Crew Dragon spacecraft nearly 100 meters (328 ft) in 2 seconds, and more than half a kilometer (1/3 mi) in just over 5 seconds.”
Credit: SpaceX
NASA dixit:
“After spending a month at the International Space Station, the U.S. unpiloted SpaceX Dragon cargo spacecraft was unberthed from the Earth-facing port of the Harmony module and released from the station’s Canadarm2 robotic arm Feb. 10 by Expedition 42 Flight Engineers Samantha Cristoforetti of the European Space Agency and Terry Virts of NASA, headed for a deorbit and parachute-assisted splashdown in the Pacific Ocean. Loaded with almost two tons of vital scientific experiments and station hardware, Dragon was aiming for a splashdown about 259 statute miles southwest of Long Beach, California, to complete the fifth commercial resupply mission to the station for SpaceX under its contract with NASA. Dragon was launched to the station atop the SpaceX Falcon 9 rocket from the Cape Canaveral Air Force Station, Florida, Jan. 10 and arrived at the station Jan. 12.”
Credit: NASA / SpaceX
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NASA dixit:
“SpaceX’s Falcon 9 rocket and its unpiloted Dragon cargo craft launched in pre-dawn darkness from the Cape Canaveral Air Force Station in Florida Jan. 10, bound on a two-day journey to deliver more than two tons of supplies and science experiments to the Expedition 42 crew aboard the International Space Station. About 10 minutes after launch, Dragon separated from the second stage of the Falcon 9 rocket and deployed its solar arrays to begin the rendezvous to reach the station on Jan. 12, where it will be grappled by station Commander Barry Wilmore of NASA and Flight Engineer Samantha Cristoforetti of the European Space Agency using the station’s Canadian-built robotic arm from the orbiting laboratory’s cupola. […]
Two days after its launch from the Cape Canaveral Air Force Station, Florida, the unpiloted U.S. SpaceX Dragon cargo craft arrived at the International Space Station Jan. 12 with more than two tons of supplies and science experiments for the Expedition 42 crew. The station crew grappled the Dragon supply ship with the station’s robotic arm and ground controllers at Mission Control, Houston maneuvered Dragon to the Earth-facing port of the station’s Harmony module, where it was installed and bolted into place for a month-long stay.”
Credit: NASA / SpaceX
NASA dixit:
“Filled with more than 3,700 pounds of hardware and critical science experiments, the SpaceX Dragon cargo craft left the International Space Station, headed for a deorbit and a parachute-assisted splashdown in the Pacific Ocean west of Baja California. Dragon arrived at the station on Sept. 23 on the fourth resupply mission to the outpost for the U.S. commercial firm. Dragon is the only cargo vehicle servicing the space station that can return cargo and scientific experiments back to Earth intact for researchers to retrieve for post-flight analysis.”
Credit: NASA
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