1.10.2024

WASHINGTON — SpaceX is suspending launches of its Falcon 9 rocket after a problem with the deorbit burn of the upper stage on a crewed launch Sept. 28, the second upper stage anomaly in less than three months for the rocket.

SpaceX said in a social media post early Sept. 29 that the upper stage “experienced an off-nominal deorbit burn” during the Crew-9 mission that launched Sept. 28. “As a result, the second stage safely landed in the ocean, but outside of the targeted area.”

The company did not provide additional details on the incident but said that it would halt Falcon 9 launches for the time being. “We will resume launching after we better understand root cause.”

The burn is designed to target the reentry of the upper stage, disposing of the stage over an unpopulated region of the South Pacific Ocean to both avoid leaving the stage in orbit, where it would pose an orbital debris risk, and to prevent an uncontrolled reentry. The targeted reentry location, based on airspace and marine hazard notices, was east of New Zealand.

The incident is the second problem involving the upper stage of the Falcon 9 in less than three months. On a Starlink launch late July 11, the single Merlin engine in the upper stage malfunctioned when reigniting on a second burn to circularlize its orbit. The satellites were deployed, but in low orbits that resulted in the satellites soon reentering.

An investigation concluded that the engine suffered a liquid oxygen leak created by a crack in a sense line for a pressure sensor. The leak resulted in “excessive cooling of engine components” including those that deliver ignition fluid to the engine. That caused the engine to suffer a hard start when it reignited, damaging the engine and causing a loss of attitude control.

On that July launch, the liquid oxygen leak was seen in video of the first burn of the upper stage as ice built up on engine components. There was no sign of similar ice buildup or other anomalous behavior of the stage during the Crew-9 launch, and neither SpaceX nor NASA mentioned any issues with the rocket during a post-launch press conference.

It is unclear how long SpaceX would pause Falcon 9 launches. The July incident halted Falcon 9 launches for 15 days, with the rocket returning to flight early July 27. SpaceX also halted launches for two days in late August after a booster was lost when it tipped over and exploded upon landing on a droneship in the Atlantic Ocean.

In both earlier cases, SpaceX needed approval from the Federal Aviation Administration to resume launches either after completing a mishap investigation or receiving a public safety determination from the agency that the incident did not pose any risk to the general public. The FAA did not immediately respond to questions on the incident early Sept. 29.

The anomaly comes as SpaceX is preparing for two time-sensitive launches in the coming weeks. One Falcon 9 is scheduled to launch as soon as Oct. 7 carrying the European Space Agency’s Hera asteroid mission. A Falcon Heavy, whose upper stage is similar to the Falcon 9, is scheduled to launch NASA’s Europa Clipper spacecraft no earlier than Oct. 10. Both missions have launch windows that run through late October.

Quelle: SN

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SpaceX grounds its Falcon rocket fleet after upper stage misfire

SpaceX’s Falcon rocket fleet was grounded for the third time in three months after a second stage problem occurred Saturday following the successful launch of a Dragon Capsule carrying two crew to the International Space Station. The suspension in flights comes as the company prepares to launch two solar system exploration missions in October with narrow launch windows.

SpaceX said the Falcon 9 second stage that launched NASA’s Crew 9 mission failed to correctly perform a firing of its Merlin Vacuum engine less than 30 minutes after releasing Dragon Freedom into a planned 117×128 mile (189×206 km) orbit.

The engine firing is designed to prevent the rocket body from becoming space debris by driving the stage into the atmosphere for a destructive reentry. Any debris was supposed to fall harmlessly into the ocean in an area previously identified in warnings to mariners and aviators.

“Falcon 9’s second stage was disposed in the ocean as planned, but experienced an off-nominal deorbit burn,” SpaceX said in a social media post, shortly after midnight EDT on Sunday. “As a result, the second stage safely landed in the ocean, but outside of the targeted area.”

The mishap is likely to prompt an investigation from the Federal Aviation Administration (FAA) which oversees the company’s launch licenses. SpaceX is currently in dispute with the FAA over fines related to Falcon 9 activities at Kennedy Space Center and delays gaining authorization for the fifth test flight of its Starship vehicle from Starbase in Texas.

Spaceflight Now reached out to the FAA for comment but had not yet received a response, with the FAA’s offices closed for the weekend.

Debris from the rocket stage should have fallen in a stretch of the Pacific Ocean that started east of New Zealand, but probably ended up falling further downrange, but still south of the Equator, according to Jonathan McDowell, an astrophysicist and tracker of space launches and satellites.

“The most likely failure mode that still results in reentry is a slight underburn,” he said in a post on X, formerly known as Twitter. “So you expect the entry to be further along… but not by too much.”

McDowell told Spaceflight Now he estimates the deorbit burn should have occurred around 1:55 p.m. EDT (1755 UTC) as the craft passed over Yemen. If everything had gone to plan, reentry would have happened about 35 minutes later.

SpaceX was scheduled to launch 20 satellites for OneWeb from its West Coast launch pad at Vandenberg Space Force Base late Sunday night local time but that mission was put on hold, along with a Starlink delivery mission from Cape Canaveral originally planned for Wednesday.

“We will resume launching after we better understand root cause [of the problem],” SpaceX said in its statement.

This will be the third grounding of the Falcon 9 fleet in three months. An upper stage problem resulted in the loss of 20 Starlink satellites on July 11. Flights resumed 15 days later after the company determined the cause of a liquid oxygen leak and came up with a quick fix. A shorter suspension of just three days came when a Falcon 9 first stage made a crash landing on the deck of SpaceX’s drone ship after an otherwise successful launch on August 28. The company has not disclosed the cause of that mishap.

The grounding of the Falcon fleet will be of particular concern to NASA and the European Space Agency (ESA) which had launches of solar system exploration missions planned within days of each other in early October.

On October 7 a Falcon 9 is scheduled to launch from Cape Canaveral with ESA’s Hera mission to study the Didymos binary asteroid system that was impacted by the DART mission in September 2022. It’s launch window runs until October 27.

Then on October 10, a Falcon Heavy, which uses the same second stage as the Falcon 9, is due to launch NASA’s Europa Clipper on a mission to explore one of Jupiter’s most intriguing moons. The Falcon Heavy will need all its performance for the $5 billion mission and two burns of the rocket’s second stage will be required.

The spacecraft will be released from the rocket at a velocity of approximately 25,000 mph (40,200 km per hour), the fastest speed ever achieved by a Falcon upper stage. The launch window for Europa Clipper closes on October 30.

Quelle: SN