SpaceX successfully launched three Falcon 9 rockets in rapid-fire mode over the weekend, sending 67 Starlink satellites into orbit within three days of receiving approval from the Federal Aviation Administration to resume launches following a rare in-flight failure on July 11.
SpaceX began its return to flight by firing up 23 Starlink internet satellites from Kennedy Space Center early Saturday morning, followed by a second Starlink launch from Cape Canaveral Space Force Station early Sunday morning, which placed 23 more broadband relay stations into orbit. The third Falcon 9 launched a few hours later from Vandenberg Space Force Base in California.
All three flights went smoothly.
NASA expects Falcon 9s to launch a Northrop Grumman Cygnus supply ship to the International Space Station on Aug. 3, followed by a SpaceX Crew Dragon flight to ferry three space station astronauts and a Russian cosmonaut to the lab around Aug. 18.
The second stage designated for manned flight, known as Crew 9, will be tested in the coming days at a SpaceX facility near McGregor, Texas, to verify that the company's corrective actions do not have any unexpected consequences.
"There will be a second hot burn around July 30 to see what new modifications the vehicle will undergo as a result of the anomaly," Steve Stich, manager of NASA's Commercial Crew Program, said Friday.
"We've been following the FAA's investigation step by step. SpaceX has been very transparent and our teams have been cooperative with the investigation and have been following all the changes to that booster."
The space agency has not yet officially approved these flights, but the successful resumption of SpaceX's flight this weekend will undoubtedly play a role in the final decision.
Boeing engineers also had a busy weekend, with successful test flights of 27 maneuvering engines on the company's Boeing 737. The Starliner capsule is now docked with the International Space Station.
The tests confirmed the good performance of the reaction control system (RCS) thrusters, which had previously experienced problems. It also confirmed that known helium leaks in the capsule's propulsion system had remained stable and had not worsened.
The tests show that the thrusters will work well when the ship eventually returns to Earth.
"The one-pulse firings were designed to confirm the performance of each thruster," Boeing wrote in an update. "Between each firing, the team reviewed real-time data and all thrusters were performing at peak thrust values.
"The helium system also remained stable," the company said. "In addition, an RCS oxidation isolation valve that had previously not been fully seated was cycled multiple times during (Saturday's) test and is now operating normally."
The Starliner was launched on June 5 during the spacecraft's first manned test flight. The Starliner crew, Commander Barry "Butch" Wilmore and co-pilot Sunita Williams - he was originally expected to stay in space for about eight days.
The mission is now nearly two months into its journey as it troubleshoots the thruster and resolves five helium leaks, one of which was discovered before launch and four of which occurred during the capsule's rendezvous with the space station.
NASA is expected to conduct a large-scale evaluation survey later this week to review the test data and determine if the ship is ready to safely return Wilmore and Williams to Earth.
SpaceX and the Falcon 9 blamed the July 11 failure on a crack in a sensor line on the upper stage caused by a loose bracket and metal fatigue, which led to a liquid oxygen leak.
The leak in turn led to extremely low temperatures in the engine's lines, slowing the flow of a fluid needed to restart the power plant for a scheduled second "burn."
Instead, the engine suffered a "hard launch" that damaged multiple components, preventing the rocket from reaching its intended orbit. While the stage remained intact, the Starlinks it carried into space were released into a much lower-than-planned orbit and subsequently burned up in the atmosphere.
Sarah Walker, a senior manager at SpaceX, said Friday that the "sense line" was not needed and would simply be removed from the rockets downstream. She said the data it provided was available from other telemetry sources on the rocket.
As for crewed Crew Dragon flights, she added, the second stage engine only stalls once and the leak that derailed the Starlink launch would not have been a factor in a crewed flight. In any case, the fitting that leaked will be removed.
"I have tremendous confidence in the team, the integrated approach that NASA has taken in the response," said Nick Hague, co-pilot of Crew 9 and veteran of a Russian Soyuz launch abort. "And I look forward to getting on the rocket when the team decides it's time to go."
He said the crew was training at SpaceX headquarters in Hawthorne, California, the day after the Starlink launch anomaly. "And right from the beginning, they included us in the conversation and told us everything they knew."
The Federal Aviation Administration, which is responsible for launch licensing in the US, agreed with the analysis of the SpaceX failure, concluding that there were "no public safety concerns."
"This public safety decision means the Falcon 9 vehicle may return to service while the general investigation continues, provided all other licensing requirements are met," the FAA said in a statement.
In addition to providing an update on SpaceX's near-term plans for the Falcon 9, Walker also addressed an unexpected issue with pieces of the Crew Dragon fuselage that had survived the heat of atmospheric re-entry and made it to the ground.
The trunk section, equipped with solar cells, helps power the Crew Dragon in space and carries external space payloads to an unpressurized space environment.
For reentry, the hull is jettisoned. The crew capsule, equipped with a heat shield, then fires its braking rockets to fall out of orbit for a precisely targeted ocean splash. The hull remains in a low orbit and eventually makes an uncontrolled reentry.
Early in the program, engineers concluded that the entire trunk would be completely burned up on reentry. However, on several occasions, relatively large, charred chunks of trunk debris have survived reentry and fallen to the ground.
Returning Crew Dragon astronauts and recently launched Dragon cargo ships have all returned to landing sites off the coast of Florida, either in the Gulf of Mexico or the Atlantic Ocean.
Walker said SpaceX now plans to move all cargo and Crew Dragon splashdowns to the Pacific Ocean off the West Coast. Trunk sections will now be jettisoned after deorbit rocket firings, so they reenter the atmosphere at roughly the same altitude as the crew and cargo capsules - that is, far offshore.
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