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 â€”over 3,000 telemetry channels as well as video and physical debrisâ€”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 â€śstrutâ€ť) 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.”
“The SpaceX CRS-7 Falcon 9 rocket lifts off from Space Launch Complex 40 at Cape Canaveral Air Force Station carrying a Dragon spacecraft on the seventh commercial resupply services mission to the International Space Station. Liftoff was at 10:21 a.m. EST. After liftoff, an anomaly occurred.”
“Following a nominal liftoff, Falcon 9 experienced a problem shortly before first stage shutdown, resulting in loss of mission. Preliminary analysis suggests the vehicle experienced an overpressure event in the upper stage liquid oxygen tank approximately 139 seconds into flight. Telemetry indicates first stage flight was nominal and that Dragon remained healthy for some period of time following separation. Our teams are reviewing data to determine root cause and we will be able to provide more information following a thorough fault tree analysis.”
NASA Administrator Statement on the Loss of SpaceX CRS-7
“We are disappointed in the loss of the latest SpaceX cargo resupply mission to the International Space Station. However, the astronauts are safe aboard the station and have sufficient supplies for the next several months. We will work closely with SpaceX to understand what happened, fix the problem and return to flight. The commercial cargo program was designed to accommodate loss of cargo vehicles. We will continue operation of the station in a safe and effective way as we continue to use it as our test bed for preparing for longer duration missions farther into the solar system.
A Progress vehicle is ready to launch July 3, followed in August by a Japanese HTV flight. Orbital ATK, our other commercial cargo partner, is moving ahead with plans for its next launch later this year.
SpaceX has demonstrated extraordinary capabilities in its first six cargo resupply missions to the station, and we know they can replicate that success. We will work with and support SpaceX to assess what happened, understand the specifics of the failure and correct it to move forward. This is a reminder that spaceflight is an incredible challenge, but we learn from each success and each setback. Today\’s launch attempt will not deter us from our ambitious human spaceflight program.”
Video credits: NASA
“[…] These landing attempts move us toward our goal of producing a fully and rapidly reusable rocket system, which will dramatically reduce the cost of space transport.A jumbo jet costs about the same as one of our Falcon 9 rockets, but airlines don’t junk a plane after a one-way trip from LA to New York. Yet when it comes to space travel, rockets fly only onceâ€”even though the rocket itself represents the majority of launch cost.
The Space Shuttle was technically reusable, but its giant fuel tank was discarded after each launch, and its side boosters parachuted into corrosive salt water every flight, beginning a long and involved process of retrieval and reprocessing. So, what if we could mitigate those factors by landing rockets gently and precisely on land? Refurbishment time and cost would be dramatically reduced.
Historically, most rockets have needed to use all of their available fuel in order to get their payload into space. SpaceX rockets were built from the beginning with reusability in mindâ€”they have enough built-in fuel margin to deliver a Dragon to the space station and return the first-stage to Earth. That extra fuel is needed to reignite the engines a few times to slow the rocket down and ultimately land the first stage after it has sent the spacecraft on its way.
In addition to extra fuel, weâ€™ve added a few critical features to our Falcon 9 first stage for reusabilityâ€™s sake. Our rocket has small, foldable heat-resistant wings called grid fins needed for steering the first-stage as it plummets from the edge of space through Earthâ€™s atmosphere, cold-gas thrusters on the top of the first-stage that are used to flip the rocket around as it begins its journey back to Earth, and strong but lightweight carbon fiber landing legs that deploy as it approaches touchdown. All of these systems, while built and programmed by humans, are totally automated once the rocket is launchedâ€”and are reacting and adjusting their behavior based on incoming, real-time data.
So, what have we learned from the most recent landing attempts?
The first attempt to land on a drone ship in the Atlantic was in January, and while we came close, the first stage prematurely ran out of the hydraulic fluid that is used to steer the small fins that help control the rocketâ€™s descent. The vehicle has now been equipped with much more of that critical fluid for steering purposes.
Our second attempt was in April, and we came close to sticking this landing. Check out this previously unreleased, longer video from our tracking camera. It shows the stageâ€™s descent through the atmosphere, when the vehicle is traveling faster than the speed of sound, all the way to touchdown.
That controlled descent was successful, but about 10 seconds before landing, a valve controlling the rocketâ€™s engine power (thrust) temporarily stopped responding to commands as quickly as it should have. As a result, it throttled down a few seconds later than commanded, andâ€”with the rocket weighing about 67,000 lbs and traveling nearly 200 mph at this pointâ€”a few seconds can be a very long time. With the throttle essentially stuck on â€śhighâ€ť and the engine firing longer than it was supposed to, the vehicle temporarily lost control and was unable to recover in time for landing, eventually tipping over.
Last-second tilt aside, the landing attempt happened pretty much exactly as planned. Shortly after stage separation (when the second stage leaves the first stage behind and goes on to carry Dragon to orbit), cold gas thrusters fired to flip the stage to reorient it for reentry. Then, three engines lit for a â€śboostback burnâ€ť that slows the rocket and brings it toward the landing site.
The engines then re-lit to slow the stage for reentry through Earthâ€™s atmosphere, and grid fins (this time with much more hydraulic fluid) extended to steer the lift produced by the stage. Our atmosphere is like molasses to an object traveling at Mach 4, and the grid fins are essential for landing with precision. The final landing burn ignited, and together the grid fins, cold gas thrusters and steerable engines controlled the vehicle, keeping the stage within 15 meters of its target trajectory throughout the landing burn. The vehicleâ€™s legs deployed just before it reached our drone ship, â€śJust Read the Instructionsâ€ť, where the stage landed within 10 meters of the target, albeit a bit too hard to stay upright.
Post-launch analysis has confirmed the throttle valve as the sole cause of this hard landing. The team has made changes to help prevent, and be able to rapidly recover from, similar issues for the next attempt, which will be on our next launchâ€”the eighth Falcon 9 and Dragon cargo mission to the space station, currently scheduled for this Sunday.
Even given everything weâ€™ve learned, the odds of succeeding on our third attempt to land on a drone ship (a new one named â€śOf Course I Still Love Youâ€ť) are uncertain, but tune in here this Sunday as we try to get one step closer toward a fully and rapidly reusable rocket.”
A tribute to Stanley Kubrick. To those of you who watched 2001: A Space Odyssey, this will look very familiar.
“This will be the first flight test of SpaceXâ€™s revolutionary new launch abort system, and the odds of encountering delays or issues are high. Fortunately the test doesnâ€™t need to be perfect to be valuableâ€”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 spacecraftâ€™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 â€śejectedâ€ť 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. SpaceXâ€™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, SpaceXâ€™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.”