Keep the shuttle flying: Fwd: Elon Musk says strut failure caused Falcon 9 explosion

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From: "Gary Johnson" <gjohnson144@comcast.net>
Date: July 21, 2015 at 10:06:03 PM CDT
To: "Gary Johnson" <gjohnson144@comcast.net>
Subject: FW: Elon Musk says strut failure caused Falcon 9 explosion

Elon Musk says strut failure caused Falcon 9 explosion
Musk called his explanation an "initial assessment" -- one that was most likely, but not certain.
By Brooks Hays   |   July 20, 2015 at 5:16 PM

| License Photo
HAWTHORNE, Calif., July 20 (UPI) -- SpaceX CEO Elon Musk is blaming the company's last rocket failure on a faulty steel strut. The collapsing steel strut, which holds up a helium bottle inside the Falcon 9 rocket, set off a chain reaction that ended in a violent explosion.
"One of those struts failed and was unable to hold the helium bottle down, and the helium bottle would have shot to the top of the tank at high speed," Musk told reporters in a teleconference call on Tuesday.
Musk called his explanation an "initial assessment" -- one that was most likely, but not certain.
The June 28 explosion was one of three consecutive failed attempts to land a reuseable rocket. It was also a letdown for those who had high hopes for the successful demonstration of reusable rocket technology.
After two close calls, the third attempt never happened. The Falcon 9 rocket was destroyed just a couple minutes into flight. SpaceX's last complete rocket failure occurred seven years ago.
Between then and now, Musk and his team had successfully launched 20 rockets in a row. Musk -- who pointed out that his company has grown from 500 to 4,000 employees over that time period -- acknowledged that his team may have gotten complacent.
But such an excuse was unacceptable, Musk insisted.
"It's just the fundamental nature of rocketry: A passing grade is 100 percent all the time," said Musk, the company's lead rocket designer.
SpaceX isn't scheduled to launch another ISS resupply rocket until September, giving the company time to order and test a new strut from a different supplier.

© 2015 United Press International, Inc. All Rights Reserved.

Musk: SpaceX rocket explosion: helium bottle broke free inside
By Scott Powers
contact the reporter

A steel strut holding a helium bottle in place inside the doomed Falcon 9 rocket broke, causing a chain reaction less than a second long that ended with the rocket exploding over Cape Canaveral June 26.
That's the preliminary assessment offered by SpaceX founder Elon Musk Monday afternoon in a teleconference explaining how the rocket explosion likely occurred, and what the company intends to do to fix it.
Musk said the fix should be easy -- a new kind of strut. He said that his company expects to be launching rockets from Cape Canaveral Air Force Station again within a few months, perhaps as soon as September.
The reason for the strut failure remains somewhat of a mystery because it was designed to handle five times as much force as it was experiencing at the time it failed, about two minutes after launch. The key pieces of rocket debris were not recovered.
Musk speculated that the alloy structure of the steel was not up to specifications, and said SpaceX's subsequent tests of other struts in inventory found others that appeared inadequate. He would not name the supplier that made the struts, but indicated a new supplier would be found.
Musk emphasized the theory is a preliminary finding and more investigation will be done.
He said SpaceX has informed its customers and the government of the theory and shared data, and they have agreed that the explanation makes sense. The explosion destroyed the $70 million rocket, its Dragon I capsule and 4,000 pounds of supplies that was headed to the International Space Station. None of it was insured.
SpaceX already has postponed its planned launches in August, but Musk said he was hopeful the delays would not be long.
Initially, SpaceX did not suspect strut failure, because they were rated to handle 10,000 pounds of load, but were experiencing just 2,000 pounds when something went wrong. All future struts going into the rockets will be individually tested, he said.
"At 3.2 Gs [of pressure] the strut holding down one of the helium bottles appears to have snapped. As a result, releasing a lot of helium into the upper-stage oxygen tank and causing a pressure event quite quickly," Musk said.
The whole event, from the instant that on-board monitors detected the first unusual noise to the point where the rocket had exploded enough that SpaceX lost all contact, was just .893 second, he said.
Musk said the capsule and its contents could have been saved had SpaceX loaded it with the same emergency software that it has designed for its astronaut-rated Dragon II capsules. He said there was no reason the software couldn't be on the cargo capsules, and it will be included on all future launches.
The Dragon capsule actually survived the explosion but was lost when it fell into the Atlantic Ocean, he said.
"If the software had initiated the parachute deployment, then the Dragon spacecraft would have survived," he said. "That was the frustrating thing. We could have saved Dragon if we had the software in there."
Helium bottles play crucial roles in SpaceX Falcon 9 rocket boosters. Several -- the number varies per launch -- are installed inside the liquid oxygen tanks of each stage, held in place by struts. As the rocket burns its oxygen and rocket fuel, the helium bottles discharge and replace those materials with helium, keeping the tanks pressurized.
In SpaceX's preliminary theory, when the strut in the upper stage broke, the helium bottle twisted loose. Because of the buoyancy of helium within a liquid oxygen core, the bottle shot to the top of the tank and discharged its contents. That over-pressurized the oxygen tank, causing it to rupture, and then the booster to explode.
Most of what was left of the second-stage booster fell into the ocean and sank to the bottom, Musk said. It has not been recovered, though he said SpaceX was planning to send a submersible down to see what could be salvaged. That debris on the bottom of the ocean could verify the preliminary findings.
For now, SpaceX is relying on telemetry it received from about 3,000 different sensors in the rockets. Among them were sound sensors that were able to precisely triangulate the point where the first unusual sound came from, and that appeared to be a breaking strut on one of the helium tanks.
"The best of what we know so far, this is an initial assessment, and further investigation may or may not reveal more over time," Musk said.
Copyright © 2015, Orlando Sentinel

Support strut probable cause of Falcon 9 failure
July 20, 2015 by Stephen Clark
Updated at 9 p.m. EDT with SpaceX statement
https://www.youtube.com/watch?feature=player_embedded&v=fTom8xVzFdo
A faulty support strut inside the Falcon 9 rocket's second stage liquid oxygen tank likely broke free during a June 28 space station resupply launch, destroying the booster minutes after liftoff in a cloud of debris over the Atlantic Ocean, SpaceX chief Elon Musk said Monday.
While noting the investigation into last month's failure is not complete, Musk told reporters Monday the evidence shows a weakened bracket holding a high-pressure helium vessel inside the Falcon 9's second stage is the likely culprit.
Several helium tanks, each pressurized to about 5,500 pounds per square inch, are mounted inside the rocket's second stage liquid oxygen tank. The helium is routed through the second stage's Merlin engine, where the helium warms up and injected into the rocket's propellant tanks to pressurize the stage as the launcher burns fuel, keeping the tanks structurally sound.
Musk said SpaceX engineers analyzing extensive telemetry data from the rocket, along with physical testing on the ground, concluded a support strut holding one of the helium tanks likely fractured near a bolt attach point.
The high-pressure helium tank, immersed inside the super-cold liquid oxygen, wanted to shoot to the top of the stage, similar to the way an inflated beach ball rises to the surface of a swimming pool, Musk said.
"It may seem sort of counterintuitive that, as the rocket's accelerating, that something immersed in the tank would actually want to go up more, but that's basically what happened," Musk said. "The buoyancy increases proprotionate to the G-loading. At approximately 3.2 Gs, this strut holding down one of the helium bottles appears to have snapped, and as a result, releasing a lot of helium into the upper stage oxygen tank and causing an over-pressure event quite quickly."
Musk said less than nine-tenths of a second passed from the first indication of a problem until the data link between the rocket and mission control cut off.
Telemetry logged from the June 28 launch showed a momentary drop in helium pressure, then a rise back to the system's starting pressure, Musk said, initially puzzling investigators probing the mishap.
One explanation for the data signature is that the tank broke free, introducing helium into the liquid oxygen tank until a kink in a feed line stopped the leak, allowing pressure in the helium system to rise again.
The failure occurred 2 minutes, 18 seconds after liftoff from Cape Canaveral, when the Falcon 9's nine first stage Merlin engines were still firing, according to a SpaceX statement released Monday. Because the second stage was not ignited, the propellant tanks were full, leaving little room to add high-pressure gas before rupturing the stage.
"Within the course of a second, this caused enough helium to be released, we believe, to over-pressurize the liquid oxygen tank in the upper stage," Musk said. "You don't really need to release a lot of helium because there's only about 2 percent gaseous volume in the stage because the upper stage propellant is not being consumed."
SpaceX engineers, who are working with NASA, the U.S. Air Force and the FAA in the investigation, have no other smoking gun on a source for last month's failure.
"There are just things that make (the strut explanation) more probable rather than less probable," Musk said, explaining a analysis method he called "acoustic triangulation."
"We've got microphones, technically accelerometers, at various points on the upper stage, and by looking at the exact timing of high-frequency events on the stage, we can, by acoustic triangulation, identify the location where the snap occurred or the breakage occurred via sound."
The evidence in the accelerometer data points to the helium tank support bracket. The strut came from a SpaceX supplier, which Musk refused to identify. He said the component, made mostly of steel, was about 2 feet long and an inch thick.
"The strut that we believe failed was designed in material certified to handle 10,000 pounds of force, but actually failed at 2,000 pounds force, which is a five-fold difference," Musk said in a conference call with reporters.
Photos of the strut taken before the launch showed no obvious sign of a flaw, and Musk said thousands of the brackets have flown on previous Falcon 9 missions without a problem. He said follow-up tests of thousands of similar struts since last month's crash revealed several units failed well below their 10,000 pounds force specification.
"We did some material analysis … and found there were problems with the grain structure of the steel," Musk said. "It hadn't been formed correctly, so we think that was the problem — a bad bolt that snuck through, that looked good, but wasn't actually good in the inside."
The rocket's first stage uses a similar pressurization system with the same type of tanks and support struts, according to Musk, who said the brackets will be pull-tested one-by-one before being installed on future launchers.
"No matter what something is certified to handle, we're not going to believe that," Musk said. "We're simply going to individually unit test every single strut."
A statement issued by SpaceX after Musk's press briefing said the company will "no longer use these particular struts for flight applications."
The Falcon 9 rocket disintegrated about 2 minutes, 18 seconds after liftoff from Cape Canaveral on June 28. Credit: Walter Scriptunas II/Scriptunas Images
The bracket suspected in the June 28 rocket failure would not have experienced the high loads it saw in flight during any of SpaceX's standard pre-launch tests, eliminating any chance of detecting the problem before liftoff. Because the rocket was rapidly accelerating at the point of the failure, the helium canister would have rapidly risen inside the full liquid oxygen tank — faster than under normal "1 G" conditions on the ground.
"One of those struts appears to have failed, and as a result, was unable to hold the bottle down, and so the helium bottle would have shot to the top of the tank at high speed because of the extreme buyoancy at the failure point of 3.2 Gs," Musk said. "Although we fire the stages on the ground, and we do a stage hold-down firing at the launch pad, the bouyancy force is only 1 G, of course, because we're not accelerating. So it would have passed through all of those tests without having an issue because it only sees high G-loading in flight."
It was not clear whether the errant helium bottle struck the outer wall of the liquid oxygen tank.
There is no way to test rocket stages on Earth to fully replicate flight conditions, Musk said.
"That would be the ultimate test, but there's no such physical thing that exists on the Earth to do that," Musk said. "One is forced, therefore, to do these things by proxy, and the proxy is sometimes inadequate as turns out to be the case here."
Despite the rocket's dramatic high-altitude anomaly, which left the launcher in shards of wreckage raining down to Earth, the SpaceX-built Dragon cargo capsule fastened to the top of the Falcon 9 survived the failure.
Musk said mission controllers received data from the unmanned supply ship, which was packed with more than 4,000 pounds of cargo for the International Space Station, until it passed over the horizon, just before its destructive impact downrange in the Atlantic Ocean.
The capsule's recovery parachutes, normally used to retrieve the spaceship after it departs the International Space Station, were not programmed to deploy after a launch mishap. SpaceX plans to install software on future cargo missions to allow the chutes to unfurl during a launch contingency, Musk said.
"We could have saved Dragon if we had the right software," Musk said.
NASA officials say the value of the cargo lost on the June 28 failure was about $110 million. The equipment was uninsured.
File photo of SpaceX founder and CEO Elon Musk. Credit: Gene Blevins/LA Daily News
The supplies included a docking adapter needed for future human-rated spaceships in development by Boeing and SpaceX to end NASA's sole reliance on Russian Soyuz ferry craft to rotate crews to and from the space station. A spacesuit, important parts for the space station's water filtration system, and an array of experiments also crashed with the Dragon spacecraft.
Musk said the next Falcon 9 launch will not occur before September, but SpaceX has not identified which payload in the rocket's crammed manifest will go next.
Before last month's failure, Falcon 9 rockets were scheduled to launch in August with the U.S.-French Jason 3 oceanography satellite and the SES 9 communications craft. The next Dragon logistics flight to the space station — the eighth in a 15-mission, approximately $2 billion contract with NASA — was supposed to blast off in early September.
SpaceX briefed customers on the tentative results of the failure investigation last week, and "none of them have indicated diminished faith" in the company, Musk said.
But the inevitable delays will cost privately-held SpaceX, which says it has a backlog of up to $7 billion, including all its contract options. SpaceX and rival Arianespace win the lion's share of commercial satellite launch business, and Musk's company received permission in May to compete with United Launch Alliance, a joint venture between Boeing and Lockheed Martin, for U.S. military launch contracts.
"The biggest penalty to SpaceX will be the delay of launch rate," Musk said. "It's sort of like an airline. If the flights don't take off, then you lose the revneue associated with that period. The lost revenue will be meaningful, in the hundreds of millions (of dollars) probably, because of the implied delays."
The additional testing prescribed to resolve the strut problem will increase the Falcon 9's production cost, Musk said, but should not affect the rocket's sales price. A Falcon 9 flight goes for approximately $61 million on the commercial market, according to information posted on SpaceX's website.
Musk admitted SpaceX may have become a "little bit complacent" after racking up more than 20 successful launches in a row, dating back to the company's earlier Falcon 1 rocket model. SpaceX's last total launch failure occurred in 2008, and the Falcon 9 itself was 18-for-18 going into the June 28 mission.
"We had some challenges there with the first Falcon 1 flights, and I think that instilled an extreme level of paranoia in the whole team," Musk said. "But seven years ago, which is when we had our last failure, the company was only about 500 people, and now we're 4,000 people. So the vast majority of the people at the company today had only ever seen success, and when you've only ever seen success, obviously you don't fear failure quite as much."
Musk sends a company-wide email before every launch, soliciting feedback from engineers who may be afraid to speak up to their mid-level managers about their concerns.
"The 20th time I send that email, it just seems like, 'There's Elon being paranoid again,'" Musk said. "It doesn't resonate with the same force, but I think now everyone at the company (realizes) the difficulties to get rockets to orbit successfully, and we'll be stronger for it."

© 2015 Spaceflight Now Inc.

Falcon 9 Failure Linked To Upper Stage Tank Strut
by Jeff Foust — July 20, 2015
The June 28 Falcon 9 failure, and resulting launch delays, will cause "meaningful" lost revenue for SpaceX, which Musk estimated in the hundreds of millions of dollars. Credit: NASA TV image
WASHINGTON — A strut in an upper stage propellant tank that failed at a fraction of its rated strength is the leading explanation for the June 28 loss of a SpaceX Falcon 9 rocket, the company's chief executive said July 20.
In a teleconference with reporters, Elon Musk said the preliminary conclusion of the three-week investigation was that a steel strut, designed to hold a bottle of helium in place within the upper stage's liquid oxygen tank, snapped while the first stage was still firing. That released enough helium gas to overpressurize the tank, causing it to burst and destroying the upper stage.
"The vast majority of the people at the company have only ever seen success," Musk said. "When you've only ever seen success, you don't fear failure quite as much."
"That's the best explanation we can think of right now," Musk said, emphasizing throughout the call the difficulty in identifying the cause of the failure and the preliminary nature of the conclusion. "So it's a really hard, hard failure mode."
Musk said that a strut failure was considered in the investigation but initially not thought likely. The strut is rated to handle up to 10,000 pounds of force, three times the calculated maximum loads, but failed at just one-fifth that rated amount. No other such struts, used hundreds of times, had experienced problems on previous launches, and tests of a small sample of the struts on the ground failed to show any problems. Photos taken of the interior of the tank during closeout of the stage also showed no signs of damage to the strut or errors in its assembly.
It was only after testing what Musk said were "thousands" of the struts did they find a few that failed at much lower forces that expected. "It was sort of a statistical thing," he said. A closer examination of the failed test struts turned up problems with the grain structure in the steel used in the struts.
The strut, which Musk described as being about 60 centimeters long and about 2.5 centimeters thick, is provided by an outside supplier that he declined to identify. SpaceX plans to use a different strut design on future launches, including a potential switch from steel to Inconel, and will likely buy the struts from a different supplier. They will also receive more thorough individual testing.
Musk declined to give a specific schedule for resuming flight, beyond saying the next launch would be no earlier than September. "We want to turn over every piece of data" to make sure they did not overlook anything, he said. The customer for that return-to-flight mission has not been identified.
Musk did say he briefed the company's customers last week about the preliminary results of the investigation. "They agree with our conclusions thus far," he said. "Every one of our customers has been supportive and none of them have indicated diminished faith in SpaceX."
"Meaningful" Losses, Falcon Heavy Delay
The failure itself, and resulting launch delays, will cause "meaningful" lost revenue for SpaceX, which Musk estimated in the hundreds of millions of dollars. He added that the first launch of the Falcon Heavy will be "deprioritized" as the company focuses on returning the Falcon 9 to flight. "We'll probably launch in the spring of next year," he said of the heavy-lift rocket the company has been developing for several years. That launch was previously scheduled for later this year.
The problem, though, should not affect the company's plans to develop a crewed version of the Dragon spacecraft by 2017. "It doesn't affect the critical path on our commercial crew timeline," Musk said. "The critical path is really the design and validation of Dragon 2."
Musk said that there was no evidence of problems with either the Falcon 9 first stage or the Dragon cargo spacecraft. He added the Dragon appeared to survive the vehicle's destruction and continued to communicate until it fell below the horizon, shortly before it hit the ocean. The vehicle's current software, though, didn't allow it to deploy its parachutes.
SpaceX plans to upgrade the software on the cargo version of the Dragon to include contingency modes to deploy parachutes in the event of such a launch failure, something the company was already planning for the crew version of the spacecraft. "We could have saved Dragon if we had the right software," Musk said.
He also suggested that the company's 4,000-person workforce, most of whom have joined the company since the failure of a Falcon 1 rocket nearly seven years ago, had become "complacent" during its string of successful launches. "The vast majority of the people at the company have only ever seen success," he said. "When you've only ever seen success, you don't fear failure quite as much."
"I think now everyone in the company appreciates just how difficult it is to get rockets to orbit successfully," he said. "I think we'll be stronger for it."

© 2015 SpaceNews, Inc. All rights reserved.

Faulty Support Strut Likely Caused SpaceX Falcon 9 Rocket Failure: Elon Musk
by Ken Kremer on July 21, 2015
The SpaceX Falcon 9 rocket and Dragon cargo spaceship dazzled in the moments after liftoff from Cape Canaveral, Florida, on June 28, 2015 but were soon doomed to a sudden catastrophic destruction barely two minutes later in the inset photo (left). Composite image includes up close launch photo taken from pad camera set at Space Launch Complex 40 at Cape Canaveral and mid-air explosion photo taken from the roof of the Vehicle Assembly Building (VAB) at NASA's Kennedy Space Center, Florida as rocket was streaking to the International Space Station (ISS) on CRS-7 cargo resupply mission. Credit: Ken Kremer/kenkremer.com
The in-flight failure of a critical support strut inside the second stage liquid oxygen tank holding a high pressure helium tank in the Falcon 9 rocket, is the likely cause of the failed SpaceX launch three weeks ago on June 28, revealed SpaceX CEO and chief designer Elon Musk during a briefing for reporters held today, July 20, to explain why the critical cargo delivery run for NASA to the space station suddenly turned into a total disaster after a promising start.
The commercial booster and its cargo Dragon payload were unexpectedly destroyed by an overpressure event 139 seconds after a picture perfect blastoff from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida on June 28 at 10:21 a.m. EDT.
Musk emphasized that the failure analysis is still "preliminary" and an "initial assessment" based on the investigation thus far. SpaceX has led the investigation efforts under the oversight of the FAA with participation from prime customers NASA and the U.S. Air Force.
The root cause appears to be that the second stage strut holding the high pressure helium tank inside the 2nd stage broke at a bolt – far below its design specification and thereby allowing the tank to break free and swing away.
"The strut that we believe failed was designed and certified to handle 10,000 lbs of force, but failed at 2,000 lbs, a five-fold difference," Musk explained.
"During acceleration of the rocket to 3.2 G's, the strut holding down the helium tank failed. Helium was released, causing the over pressurization event."
To date no other issues have been identified as possible failure modes, Musk elaborated.
The helium tanks are pressurized to 5500 psi and were breached during the over pressurization. The purpose of the helium tanks is to pressurize the first and second stage propellant tanks.
SpaceX Falcon 9 rocket explodes about 2 minutes after liftoff from Cape Canaveral Air Force Station in Florida on June 28, 2015. Credit: Ken Kremer/kenkremer.com
"We tested several hundred struts. On the outside they looked normal. But inside there was a problem," Musk explained
"Detailed close-out photos of stage construction show no visible flaws or damage of any kind," according to a SpaceX statement.
The struts are produced by an outside vendor that Musk would not identify. He added that in the future, SpaceX will likely choose a different vendor to manufacture the struts.
He said the struts were made from a type of stainless steel and would also likely be redesigned.
"The material of construction will be changed to Inconel," Musk told me in response to a question.
Hundreds of the original type struts have been used to date on the first and second stages of the Falcon 9 with no issues. In the future, they will also be independently certified for use, by an outside contractor instead of the vendor.
The nine first stage Merlin 1D engines of the Falcon 9 were still firing nominally during the start of the mishap, said Musk. The first stage had nearly completed its planned firing duration when the explosion took place.
"The event happened very quickly, within 0.893 seconds," Musk stated, from the first indication of an issue to loss of all telemetry.
"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," noted SpaceX in a statement.
https://www.youtube.com/watch?feature=player_embedded&v=79fl8GgLKxA
Video caption: Launch video of the CRS-7 launch on June 28, 2015 from a remote camera placed at Launch Complex 40. The launch would fail around two minutes later. Credit: Alex Polimeni/Spaceflight Now

The blastoff of the Dragon CRS-7 cargo mission for NASA was the first failure of the SpaceX Falcon 9 rocket after 18 straight successes and the firms first launch mishap since the failure of a Falcon 1 in 2008.
The SpaceX CRS-7 Dragon was loaded with over 4,000 pounds (1987 kg) of research experiments, an EVA spacesuit, water filtration equipment, spare parts, gear, computer equipment, high pressure tanks of oxygen and nitrogen supply gases, food, water and clothing for the astronaut and cosmonaut crews comprising Expeditions 44 and 45.
Umbilicals away and detaching from SpaceX Falcon 9 launch from Cape Canaveral, Florida, on June 28, 2015 that was doomed to disaster soon thereafter. Credit: Ken Kremer/kenkremer.com
The Dragon cargo freighter survived the explosion but was destroyed when it impacted the Atlantic Ocean.
"But the Dragon might have been saved if the parachutes had been deployed," said Musk.
Unfortunately the software required to deploy the parachute was not loaded onboard.
"The new software required to deploy the parachutes will be included on all future Dragons, V1 and V2," said Musk, referring to the cargo and crew versions of the SpaceX Dragon spaceship.
SpaceX Falcon 9 rocket and Dragon resupply spaceship explode about 2 minutes after liftoff from Cape Canaveral Air Force Station in Florida on June 28, 2015. Credit: Ken Kremer/kenkremer.com
The NASA cargo was valued at about $110 million. The launch itself was not insured.
The investigation board is reviewing data from over 3,000 telemetry channels as well as video and physical debris, he noted.
The next launch of a Falcon 9 will be postponed at least a few months until "no earlier than September" Musk indicated.
Two Falcon 9 launches had been set for August from Vandenberg AFB and Cape Canaveral. And the next launch to the ISS had been slated for September on the Dragon CRS-8 mission.
Musk said the next payload to be launched aboard a Falcon 9 has yet to be determined.
Starting in 2017, the Falcon 9 will launch astronauts to the ISS aboard the Crew Dragon.
Overall CRS-7 was the seventh SpaceX commercial resupply services mission and the eighth trip by a Dragon spacecraft to the station since 2012.
CRS-7 marked the company's seventh operational resupply mission to the ISS under a $1.6 Billion contract with NASA to deliver 20,000 kg (44,000 pounds) of cargo to the station during a dozen Dragon cargo spacecraft flights through 2016 under NASA's original Commercial Resupply Services (CRS) contract.

AmericaSpace
For a nation that explores
July 20th, 2015
Failed Strut Doomed CRS-7 Mission; No Falcon 9 Launches Before September, Says Elon Musk
By Ben Evans
The nine plumes of the Merlin 1D engines flare as the vehicle disintegrates. Photo Credit: Alan Walters/AmericaSpace
Three weeks after the catastrophic loss of a Falcon 9 v1.1 booster, which exploded just 139 seconds after leaving Space Launch Complex (SLC)-40 at Cape Canaveral Air Force Station, Fla.—dooming the seventh dedicated Dragon cargo ship, bound for the International Space Station (ISS)—SpaceX CEO Elon Musk described the status of his company's ongoing investigation on Monday, 20 July, and revealed that a failed helium tank strut appeared to be the root cause. Over the past weeks, engineering teams have spent thousands of hours matching up data across Falcon 9 v1.1 systems down to the millisecond, in order to properly understand the event which befell their vehicle, within a period of just 0.893 seconds, prior to loss of telemetry. In summarizing the developments, Mr. Musk noted that the accident occurred rapidly, that software modifications might have saved its precious Dragon payload and that the failure is not expected to impair SpaceX's goal of launching its first Commercial Crew missions from 2017 onwards. At the same time, he added that the Hawthorne, Calif.-based launch services company does not expect to fly another Falcon 9 v1.1 until September 2015 at the soonest.
As described in a previous AmericaSpace article, the loss of the CRS-7 mission on 28 June shattered an impressive track record of 18 successful launches by SpaceX since June 2010, which have delivered a wide range of payloads into low-Earth orbit, Geostationary Transfer Orbit (GTO) and further afield, to the L2 Lagrange Point. Thirteen successful missions have been flown by the upgraded Falcon 9 v1.1 since September 2013. This variant of the two-stage booster benefits from the enhanced Merlin 1D powerplant—whose nine first-stage engines are capable of 1.3 million pounds (590,000 kg) of propulsive yield and whose restartable Merlin 1D Vacuum second-stage engine generates 180,000 pounds (81,600 kg) of thrust—and can deliver up to 28,990 pounds (13,150 kg) into low-Earth orbit and up to 10,690 pounds (4,850 kg) into GTO. Key payloads launched successfully to date by the v1.1 have included four ISS-bound Dragons, the Deep Space Climate Observatory (DSCOVR) to the L2 Lagrange Point and six telecommunications satellites into Geostationary Transfer Orbits at an approximate altitude of 22,300 miles (35,600 km).
First-stage flight of the CRS-7 mission appeared nominal, with catastrophe striking the Falcon 9 v1.1 abruptly. Photo Credit: Alan Walters/AmericaSpace
However, the heart was torn from SpaceX on 28 June, when the 14th Falcon 9 v1.1 vanished into a fireball, just 139 seconds after liftoff, dooming not only the CRS-7 Dragon cargo ship—the seventh dedicated mission under the terms of a $1.6 billion Commercial Resupply Services contract with NASA, signed back in December 2008—but also the first of two critical International Docking Adapters (IDA-1). These adapters, the second of which remains earmarked to fly aboard the CRS-9 Dragon mission, were intended to be installed onto the forward-facing and space-facing (or "zenith") ports of the space station's Harmony node, thereby providing primary and backup docking interfaces for Boeing's CST-100 and SpaceX's own Dragon V-2 piloted vehicles from mid-2017 onwards. It is understood that IDA-2 will now be repurposed for the former IDA-1 role, whilst a set of structural spares will be used as the basis for the construction of IDA-3 to fulfil the original IDA-2 role. Although it is expected that IDA-3 will ride a Falcon 9 v1.1 uphill, it remains to be seen when that launch will now take place.
Speaking earlier today, in a media teleconference, SpaceX CEO Elon Musk explained that a support strut—measuring about 2 feet (60 cm) in length and about an inch (2.5 cm) in thickness at its widest point—appeared to be the root cause of the failure. Developed by a supplier which Mr. Musk refused to name, the strut's role was to support one of the composite over-wrapped helium tanks in the Falcon 9 v1.1's second stage. Designed to handle up to 10,000 pounds (4,530 kg) of force, the strut actually failed at just 2,000 pounds (900 kg), barely a fifth of its rated strength, catastrophically releasing helium into the second stage Liquid Oxygen (LOX) tank at about 3.2 G. "The pressurization system itself was performing nominally, but with the failure of this strut, the helium system integrity was breached," SpaceX explained in a news release Monday evening. "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." It is understood that the struts will no longer be used on future missions and that SpaceX plans to "implement additional hardware quality audits throughout the vehicle" to ensure that "all parts received perform as expected per their certification documentation".
Subsequent inspection of pre-flight images of the strut revealed no apparent trace of damage. "No evidence of assembly errors in the strut in hi-res closeout photos taken before launch," Mr. Musk stressed, adding that SpaceX engineers will now move toward individual testing of the struts. He noted that the accident unfolded rapidly, with the first indication of a problem through to the structural breakup spanning just 0.893 seconds, and described the circumstances of the CRS-7 accident as a "really odd failure mode".
Within a matter of seconds, the Falcon 9 v1.1 was reduced to debris, plunging back to Earth. Photo Credit: Alan Walters/AmericaSpace
These findings are in keeping with early speculation on 28 June, which highlighted that first-stage performance was entirely nominal and that the CRS-7 Dragon spacecraft continued to communicate, until it passed over the horizon after the failure. Mr. Musk pointed out that, in spite of no other issues with the launch, SpaceX was looking at other issues, admitting that the company may have become complacent in recent years. "Rockets are a fundamentally difficult thing," he explained, adding that no further Falcon 9 v1.1 launches are anticipated before September 2015 at the earliest, with the maiden flight of the mammoth Falcon Heavy—which, when operational, carries the potential to deliver up to 117,000 pounds (53,000 kg) into low-Earth orbit and up to 46,700 pounds (21,200 kg) into Geostationary Transfer Orbit—pushed back to no sooner than March 2016.
This is an intense pity, for SpaceX accomplished five flawless Falcon 9 v1.1 missions in the first four months of 2015, together with the highly successful Pad Abort Test (PAT) of its crewed Dragon vehicle in May. The company has delivered a pair of Dragons—CRS-5 in January and CRS-6 in April—to restock the ISS, despatched the DSCOVR spacecraft to the L2 Lagrange Point in February and lofted the Eutelsat 115 West B, ABS-3A and TurkmenÄlem52E/MonacoSat communications satellites into Geostationary Transfer Orbit in March and April. Had the loss of CRS-7 not occurred, as many as eight more missions were timetabled for the second half of 2015, including a further two Dragons to deliver the Bigelow Expandable Activity Module (BEAM) and the IDA-2 docking adapter to the space station, together with the Jason-3 ocean surface altimetry mission, several commercial payloads and the maiden voyage of the Falcon Heavy.
In spite of the disappointment, Mr. Musk does not expect the CRS-7 loss to significantly impact the Commercial Crew timeline, describing it as being "not on the critical path", and kindling some hope that SpaceX may still be in a position to launch its first uncrewed Dragon as soon as the fall of 2016 and a piloted mission several months later. He added that had the "right software" been aboard CRS-7, the Dragon and its payload might have been salvaged. "The Dragon spacecraft not only survived the second-stage event," a subsequent SpaceX news release stated, "but also continued to communicate until the vehicle dropped below the horizon and out of range."
Software to permit the deployment of parachutes in the event of a launch failure will be included aboard the CRS-8 Dragon mission, which was originally scheduled for early September, but whose target date presently remains in flux. Although Mr. Musk hinted at a No Earlier Than (NET) target of September for the next Falcon 9 v1.1 mission—with no information yet on whether it will carry Jason-3, CRS-8 or another payload—he was adamant that precise return-to-flight dates would only be issued after all data had been fully analyzed and properly understood. What is clear, though, is that lost revenues from this failure are expected to be "meaningful", stretching into the hundreds of millions of dollars. "Our investigation is ongoing until we exonerate all other aspects of the vehicle," SpaceX stressed, "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."

The author would like to express thanks to AmericaSpace's Michael Galindo, for his support in the preparation of this article.

Copyright © 2015 AmericaSpace - All Rights Reserved

Failure of One Metal Strut Seemed to Doom SpaceX Falcon 9 Rocket
By KENNETH CHANG
JULY 20, 2015
Kenneth Chang
The SpaceX Falcon 9 rocket broke apart after launch on June 28. John Raoux/Associated Press
The snapping of a single strip of metal holding a part in place appears to have doomed an unmanned cargo rocket headed to the International Space Station last month, a preliminary investigation has found.
Space Exploration Technologies Corporation, or SpaceX, of Hawthorne, Calif., is one of the companies that NASA is relying on to take cargo — and, in a few years, astronauts — to the space station. It had had a string of 18 successful flights for its Falcon 9 rocket, a remarkable success rate for a new rocket design.
But on June 28, a Falcon 9 destined for the space station disintegrated less than three minutes after liftoff from the Cape Canaveral Air Force Station in Florida. The rocket was carrying more than 4,000 pounds of supplies, equipment and experiments, including 30 from students.
"I think to some degree, the company as a whole became maybe a little bit complacent," Elon Musk, the chief executive of SpaceX, said Monday during a telephone news conference.
Video of the launching suggested that the problem occurred in the midsection of the rocket, and that the first-stage engines continued to fire normally even as the rocket began to fall apart.
Falcon 9 Rocket Explodes
Shortly after liftoff on Sunday, a SpaceX Falcon 9 blew up. The rocket carried a cargo ship bound for the International Space Station.
By Reuters on June 28, 2015. Watch in Times Video »
Only 0.893 seconds elapsed between the first indication of trouble and the last data sent back from the rocket.
Engineering analysis indicated that the problem started with a metal strut, two feet long and one inch thick, that was holding down a helium bottle within the second-stage liquid oxygen tank. The strut failed at 2,000 pounds of force when it should have been able to withstand 10,000 pounds, Mr. Musk said.
The unrestrained bottle broke free, releasing the helium inside, and the added pressure caused the oxygen tank to break apart, leading to the disintegration of the rocket, Mr. Musk said.
"This is somewhat speculative, but that's the best explanation we can think of right now," Mr. Musk said.
Each Falcon 9 contains hundreds of such struts, and only after testing a large number of them did the company find a few that did not meet the requirements. Mr. Musk said the company would redesign the struts and in the future would individually test them.
He said the company would also take the time to review its production and operations to check for other issues that might have been "near misses" so far, even if they did not lead to disaster.
The Dragon capsule on top of the rocket that was carrying the equipment and supplies fared better. It continued to send back its status until disappearing over the horizon. Had its parachutes deployed, it would have survived, Mr. Musk said, and in future launches, instructions to deploy parachutes in such circumstances will be added to its programming.
The next Falcon 9 flight will be no sooner than September, Mr. Musk said. The inaugural flight of SpaceX's much larger Falcon Heavy rocket will also be delayed, from later this year to next spring, he said.
The SpaceX mishap was the third loss of a cargo ship headed to the space station in the last year. A cargo rocket built by the Orbital Sciences Corporation of Dulles, Va., exploded just after liftoff from a launching pad in Virginia in October, and a Russian supply ship in April spun out of control because of a problem with the rocket's upper stage.
A Russian supply rocket successfully launched to the space station the week after the SpaceX failure, and the astronauts on the space station have sufficient supplies for months. Three astronauts are set to launch to the space station on a Russian Soyuz rocket on Wednesday to bring the size of the crew back to six.

A version of this article appears in print on July 21, 2015, on page A18 of the New York edition with the headline: Failure of One Metal Strut Seemed to Doom Rocket.
© 2015 The New York Times Company

Faulty metal brace likely doomed SpaceX Falcon rocket, Musk says

By Irene Klotz
.
View photo
An unmanned SpaceX Falcon 9 rocket explodes after liftoff from Cape Canaveral, Florida, June 28, 2015. …
By Irene Klotz
CAPE CANAVERAL, Fla (Reuters) - A faulty metal brace in an unmanned SpaceX Falcon 9 rocket likely triggered the explosion that destroyed the booster minutes after liftoff from Florida last month, company chief Elon Musk said on Monday.
The June 28 accident, which destroyed a load of cargo destined for the International Space Station, was the third botched resupply run within eight months. An Orbital ATK rocket explosion claimed a Cygnus cargo ship in October and a Russian Progress freighter failed to reach orbit in April.
SpaceX founder and Chief Executive Musk said Falcon rocket flights will not resume until September at the earliest. The company also plans to delay the debut flight of its heavy-lift Falcon rocket from this year to spring 2016.
A defective brace, or strut, holding a bottle of helium in the Falcon 9 needed to pressurize the upper-stage engine's liquid oxygen tank, was the most likely cause of last month's accident, Musk said.
He said the strut, from a vendor he declined to identify, was built from steel certified to withstand 10,000 pounds (4,536 kg) of force but apparently failed at 2,000 pounds (907 kg) of force, Musk said.
"It looks like the key strut that holds down one of the helium bottles failed. As a result, the helium bottle would have shot to the top of the tank at high speed," Musk told reporters on a conference call.
"It failed five times below its nominal strength, which is pretty crazy," he said.
SpaceX not only intends to buy new struts, most likely from a different vendor, but test each one prior to installation in the rocket's tanks, Musk said.
SpaceX had successfully flown its Falcon 9 rocket 18 times since its debut in 2010 before the June 28 failure. During those flights, thousands of similar struts apparently worked with no issues.
"We have been able to replicate the failure by taking a huge sample, essentially thousands of these struts, and pulling them. We found a few that failed far below their certificated level. That's what led us to think that there was one just far below its rated capability that happened to be at the wrong place at the wrong time," Musk said.
The results are preliminary, he added.
In addition to the bad strut, SpaceX is looking for other issues that may have caused or contributed to the accident, as well as any potential problems that could affect future flights.
"This is the first time we've had a failure in seven years, so I think to some degree the company as a whole became maybe a little bit complacent," Musk said.
The company has a backlog of more than 50 rocket launches, worth about $5 billion, for commercial companies, NASA and other agencies.
(Reporting by Irene Klotz; Editing by Tom Brown)

Copyright © 2015 Reuters Limited. All rights reserved.

Failed strut caused SpaceX rocket blast: CEO Elon Musk
By Kerry Sheridan

.

Miami (AFP) - The explosion last month of SpaceX's Falcon 9 rocket was caused by a failed support piece, or strut, that allowed a helium bottle to burst free inside the rocket's liquid oxygen tank, CEO Elon Musk said.
"One of those struts broke free during flight," Musk told reporters on a conference call to discuss the June 28 blast on what was supposed to be a routine cargo mission to the International Space Station.
"So the helium bottle would have shot to the top of the tank at high speed."
Musk noted that the findings are the preliminary results of a weekslong investigation by the California-based company.
The accident caused NASA to lose $110 million in equipment bound for the astronauts living in orbit, a US space agency spokesman told Congress earlier this month.
"Several hundred struts fly on every Falcon 9 vehicle, with a cumulative flight history of several thousand," SpaceX said in a statement.
View gallery

The SpaceX Falcon 9 rocket lifts off from space launch complex 40 at Cape Canaveral, Florida with a …
"The strut that we believe failed was designed and material certified to handle 10,000 lbs (4,500 kilograms) 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."
The struts in question are each two feet (60 centimeters) long and an inch thick, and were furnished to SpaceX by an outside supplier.
"We are not going to use these particular struts in the future," Musk said, adding that the company plans to begin individually testing each strut ahead of future launches.
Musk said SpaceX would return to flight with the Falcon 9 "no sooner than September."
He also said the problem is not expected to delay the company's goal of sending astronauts to space aboard its Dragon spaceship within the next two years.
View gallery

Elon Musk, the billionaire cofounder of PayPal who also heads Tesla Motors, said SpaceX had had a se …
Musk, the billionaire cofounder of PayPal who also heads Tesla Motors, said that SpaceX had had a seven-year record of safety in flight until the accident happened.
He admitted that SpaceX may have become "a little bit complacent," and that the blast offered an "important lesson" for the future.
The explosion happened just over two minutes after the rocket blasted off from Cape Canaveral, Florida.
The rocket failure was the third in a series of cargo disasters in the past eight months.
In October, US company Orbital's Antares rocket exploded after launch from Virginia, and in April, Russia lost contact with its Progress cargo ship shortly after liftoff.

Copyright © 2015 Agence France Presse. All rights reserved.

SpaceX Rocket Explosion Likely Caused by Faulty Strut, Elon Musk Says
by Mike Wall, Space.com Senior Writer   |   July 20, 2015 03:53pm ET

A SpaceX Falcon 9 rocket disintegrated shortly after launching from Cape Canaveral Air Force Station in Florida on June 28, 2015. SpaceX has traced the failure to a faulty strut on the rocket's second stage, CEO Elon Musk said on July 20.
Credit: NASA TV View full size image
The disintegration of a SpaceX Falcon 9 rocket shortly after it launched on a space station resupply mission for NASA last month was most likely caused by a faulty strut inside the booster's upper stage, company CEO and founder Elon Musk said Monday (July 20).
SpaceX investigators believe the explosion of the Falcon 9 rocket on June 28 during a launch to the International Space Station occurred because a steel strut holding down a bottle of high-pressure helium snapped during ascent. This failure allowed the bottle to shoot to the top of the booster's upper-stage liquid-oxygen tank at high speed, causing a rapid "overpressure event" that destroyed the rocket, Musk told reporters during a teleconference. (Somewhat counterintuitively, buoyancy increases with g-forces during a launch, explaining why the bottle would travel up, Musk said.)
Every Falcon 9 launches with hundreds of such struts aboard, Musk said. Both stages of the two-stage rocket harbor many bottles that store helium at cryogenic temperatures. During flight, this helium flows to the engines, where it is warmed; the substance is then recirculated to the booster's liquid-oxygen and fuel tanks to repressurize and structurally stabilize them, compensating for the volume of fuel and oxidizer lost during flight. [The Falcon 9 Explosion in Slow Motion (Video)]
The roughly 2-foot-long (0.6 meters) struts hold these bottles in place. Each strut is certified to withstand about 10,000 lbs. (4,500 kilograms) of force. Based on when the explosion happened — less than 3 minutes after liftoff — the strut in question apparently broke under a load of less than 2,000 lbs. (900 kg), Musk said.
"It's not something that should have ever failed at this force level," he said. The strut "would appear to be incorrectly made, but there was no visible way of telling that from the outside."
SpaceX sources these struts from an outside company and will probably change suppliers now, Musk added. In addition, SpaceX plans to individually test and certify every strut that will fly, to ensure that no faulty ones make it on board, he said.
This assessment of the Falcon 9 rocket failure is preliminary rather than definitive, Musk said, stressing that the investigation of the mishap is ongoing.
Still, he added, "right now, there doesn't seem to be any other explanation that could make sense."
The Falcon 9 launched from Florida's Cape Canaveral Air Force Station on June 28 carrying SpaceX's robotic Dragon space capsule on the company's seventh contracted cargo mission to the space station. SpaceX holds a $1.6 billion NASA deal to make at least 12 such flights; the first six missions had all been completely successful.
The explosion did not destroy Dragon, and the capsule continued sending data back to mission control until it disappeared over the horizon, Musk said. The company has retrieved some pieces of floating Dragon debris from the Atlantic Ocean, but most of the capsule is apparently sitting on the seafloor. SpaceX aims to send a robotic submarine to the presumed crash site soon in an attempt to locate the spacecraft.
Dragon would almost certainly have survived the incident intact if its onboard software had been geared to allow parachute deployment so early in the flight, Musk added. (Dragon cargo capsules make parachute-aided ocean splashdowns after completing their missions.) [The Rockets and Spaceships of SpaceX (Photos)]
"That is probably the saddest thing about this, is that, if there was just a bit of different software, Dragon would have made it," Musk said, adding that such software will be installed in time for the next cargo mission.
However, when that next flight will take place is unclear at the moment. The next SpaceX launch will come no earlier than September, Musk said, and he's not sure what the payload will be when the company returns to flight.
The delay and decrease in flight rate resulting from the mishap will probably end up costing SpaceX hundreds of millions of dollars, Musk added. In addition, the ongoing focus on the Falcon 9 will likely push the highly anticipated first flight of the company's huge Falcon Heavy booster into spring 2016 at the earliest.
SpaceX is also developing a manned version of Dragon, which NASA will use (along with Boeing's CST-100 capsule) to fly astronauts to and from the space station. The manned version of Dragon, which is equipped with an escape system to get the capsule out of harm's way during a launch emergency, would have survived the June 28 accident, Musk said, adding that he doesn't anticipate any delays in the crew-carrying spacecraft's development. (NASA wants the two private astronaut taxis to be up and running by 2017.)
The June 28 Falcon 9 explosion was the third failure of a robotic cargo mission to the space station in less than a year. In October 2014, Orbital ATK's Antares rocket blew up seconds after lifting off, ending the company's third resupply run for NASA under a $1.9 billion deal. And in May, Russia's Progress 59 spacecraft fell back to Earth without reaching the space station, victimized by a problem with the third stage of its Soyuz rocket.
"Each one of these failure modes has been quite different," Elon Musk said. "It just goes to show — rockets are a fundamentally difficult thing."

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