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Almost every rocket that has flown has had an anomaly. With thousands of components that must all work in perfect harmony for a mission to be successful, there will likely be one component that fails every now and then.

While witnessing an anomaly in spaceflight is not as incredible as it may seem, it does become unusual to see as the cadence of flights increases. It can almost be expected that the first launch of a new missile will end in failure sometime in flight. However, when a rocket that has been flying fast without any problems for more than seven years is unable to deliver its payload, the spaceflight industry takes notice.

On Thursday, July 11, at 10:35 PM EDT (Friday, July 12, at 2:35 UTC), Falcon 9 grounded after an upper stage failure caused the loss of the Merlin Vacuum (MVac) engine. The anomaly also resulted in the loss of the Starlink satellites on board after they failed to reach a stable orbit.

The Falcon 9 is an extremely reliable launch vehicle, with only four anomalies to date. Most of those failures occurred while it was in the early design stages of the Block 2 and Block 3 vehicle. The Falcon 9 Block 5 had 297 successful launches until Saturday’s 298th launch, making it one of the most reliable rockets flown sometime.

Falcon 9 Anomaly History

The first Falcon 9 in-flight failure occurred on June 28, 2015. After a nominal liftoff of Falcon 9 Block 2 of the CRS-7 mission, the liquid oxygen (LOX) tank on the second stage was over-pressurized and ruptured 139 seconds into flight. The rupture of the tank led to the destruction of the missile 11 seconds later. That mission was planned to resupply the International Space Station using SpaceX’s uncrewed Dragon capsule, which was separated from the rocket before crashing into the ocean and being lost.

This failure of NASA’s vehicle and payload led to NASA’s involvement in the investigation. It was found that the strut inside the second stage LOX tank failed to manage the forces it was expected to withstand. SpaceX solved this problem by replacing the faulty prop with a more robust version and by requiring more vehicle quality audits before departure for flight. After the failure, Falcon 9 had a 95 percent success rate and it took almost six months for the next mission to fly on December 21, 2015.

After the failure of CRS-7, routine launches returned and landings began to become successful for SpaceX. The first successful landing of an orbital rocket took place on the next launch, when the B1019 booster touched down back at SpaceX’s Landing Zone 1. Then, four launches after the failure, the first successful booster landed on top of a drone Of course I still love you occurred. SpaceX was collecting more launch and landing successes until September 1, 2016.

Nine months after CRS-7, Falcon 9 suffered another anomaly. AMOS-6 was planned to be the 29th launch of SpaceX’s Falcon 9. During refueling for a pre-flight static fire test, a casing inside the composite enveloped pressure vessel (COPV) tank buckled, causing propellant to collect under the casing, igniting a spark caused by friction. This caused an explosion that destroyed the entire vehicle. The AMOS-6 anomaly reduced Falcon 9 reliability to just under 90 percent. On January 14, 2017, SpaceX returned to flight just over four months after AMOS-6.

AMOS-6 Static Fire Anomaly. (Credit: SpaceX)

Recent Anomalies in the Space Flight Industry

Early in the development of a brand new missile, and even new iterations of operational missiles, it is almost expected to witness an anomaly. Many would-be start-ups and even government agencies have had failures in the first few launches of a brand new system. SpaceX has even begun to adopt a “fail fast, but iterate faster” approach to speeding up designs quickly. No rocket has as much of that idea behind it as SpaceX’s starship.

Every single one of Starship’s test flights, from the Starhopper to high-altitude suborbital ship hops to today’s near-orbital flights, was fast-paced. For example, it took the teams five tries to learn how to land the ship. As the flight tests progressed, however, SpaceX learned from its mistakes and quickly improved the vehicle in ways that would never have been foreseen if it was just a blueprint. Today, the Starship is not a reliable vehicle, but each integrated flight test exceeds the system requirements and succeeds in more and more of SpaceX’s goals. It may not be long before Starship is accepted as a reliable satellite launch vehicle.

The first flight of the Starship. (Credit: Max Evans for NSF)

There are many examples of space startups working to develop a rocket to achieve the success of a profitable space company. A company currently in this process is Firefly Aerospace with its Alpha rocket. Alpha has made five flights and has not had the best results. There was a failure on the first flight, a partial failure on the second and fourth flights, and two successes on the third and fifth flights. Holding tight to recent success, Firefly looks set to continue with another clean launch in October later this year. If all goes well, Firefly may already have passed the inflection point of success.

The European Space Agency (ESA) is the latest government agency to build and launch a brand new rocket with Ariane 6. Ariane 6’s inaugural flight went smoothly up to an hour and 14 minutes into the flight. Ariane 6 successfully entered a circular orbit and deployed most of the 11 payloads on board. The auxiliary propulsion system (APU) then failed, causing the planned third orbital burn to fail. Even after many years and billions of dollars invested in development, it is common for a small anomaly to cause a partial failure of the entire mission.

The first launch of Ariane 6 (Credit: ESA)

Another government The agency that went through this problem and eventually succeeded is the Japan Aerospace Exploration Agency (JAXA), Japan’s space agency. The agency had a few problems with its new H3 rocket, which debuted last year. After TF1’s first test flight in March 2023 failed due to a second-stage engine failure, JAXA took just under a year to prepare for the next H3 flight. On the second flight, H3 successfully reached the planned sun-synchronous orbit and deployed its satellites. Then, just over four months later, the first determined flight was a complete success.

Rocket Lab follows a similar path to the other aforementioned private companies. On Rocket Lab’s Electron’s first flight, it successfully survived stage separation and path separation. However, due to a software failure that caused the telemetry feed to be lost, the flight termination system was activated – ending the mission. After this launch, the Electron successfully flew to its 13th flight. This flight failed during the second stage burn due to a faulty wire that broke the electrical connection to the engine’s turbopumps.

Visible sparks at the anomaly point during Rocket Lab’s 41st launch. (Credit: Rocket Lab)

Then, on Electron’s 20th mission, the second stage shut down early due to an igniter failure. The failure of the igniter caused the thrust vector control system to malfunction, diverting the missile from its intended trajectory. Another 20 missions went smoothly until Electron’s 41st mission. Electron failed to reach orbit due to an arc that shorted out, causing Rutherford’s upper stage engine to lose thrust. After Rocket Lab’s failure, it took just under three months to get the Electron back into the sky. Rocket Lab is now up to 50 launches and has a 92 percent success rate.

Blue Origin’s New Shepard suborbital rocket has successfully launched 24 times. However, during the NS-23 mission, a failure was caused by the BE-3 main engine, which activated the capsule’s launch rescue system. The Blue Origin booster, Queue 3, who was flying his ninth mission, structurally damaged due to the BE-3PM engine temperature rise not accounted for by the booster. Fortunately, there were no crew members on board the capsule and only commercial cargo. The launch recovery system worked as intended and returned the payloads back to Earth safely. New Shepard has achieved a 96 percent success rate over 25 missions with only one failure. It will take more than 15 months for New Shepard to return to flight after NS-23 halts Blue Origin operations.

Shepard’s new anomaly in the NS-23 mission. (Credit: Blue Origin)

Falcon 9 returns to flight

Falcon 9 will return from its short hiatus with the Starlink Group 10-4 mission. The launch is scheduled to take place from SLC-40 at the Cape Canaveral Space Force Station on Saturday, July 27, at 00:13 EDT (4:13 UTC). The FAA announced on July 25 that the anomaly did not affect public safety. That doesn’t mean the investigation is over, but it does mean SpaceX can resume Falcon 9 launches.

SpaceX revealed that the problem was most likely caused by a crack that developed in a “sense line” during the first second stage burn. The sensor line is responsible for checking the pressure in the second stage of the LOX tank. When the second stage burn began, there was too much cryogenic LOX flowing through the MVac engine and it had overcooled so much that the engine was overpressurized. This probably resulted in an explosion terminating the burn and causing a loss of attitude control. SpaceX mentioned that the sensor connected to the sensor line is not used by the flight safety system and other systems make the sensor redundant. Therefore, SpaceX’s plan moving forward is to remove the damaged sensor line and sensor from the vehicle.

Thanks to the pace we’ve been able to launch, we’re able to collect unprecedented levels of flight data and are ready to quickly return to flight as soon as Saturday, July 27 → https://t.co/DvO0z1NbUm

— SpaceX (@SpaceX) July 25, 2024

It is an anomaly in itself that SpaceX could bring the Falcon 9 back online in less than 14 days after a second stage failure. With 355 missions and only four failures in 14 years of operation, the Falcon 9 is one of the most reliable rockets ever flown with a 99 percent success rate.

(Main image: Falcon 9 launch from SLC-40 at Cape Canaveral Space Force Station. Credit: Max Evans for NSF)