Analyzing Starship IFT-3: Successes, Challenges, and Improvements for Future Flights

SpaceX conducted its third integrated flight test (IFT-3) of the fully stacked Starship and Super Heavy rocket on March 14, 2024 from Starbase in Boca Chica, Texas. The launch aimed to build upon the progress of the first two tests by demonstrating key milestones such as full-duration Raptor engine burns, successful hot-staging, boost-back burns, in-space propellant transfer, and payload bay door operation. While the mission achieved several objectives, both the Super Heavy booster and Starship upper stage were lost during the final stages of the flight.

Super Heavy Booster Performance and Issues

The Super Heavy booster, powered by 33 Raptor engines, successfully lifted off and separated from the Starship upper stage. It then attempted a boost-back burn and flip maneuver to prepare for a soft water landing in the Gulf of Mexico. However, the booster experienced a loss of control prior to the landing burn initiation, likely due to issues with the control system and liquid oxygen inlet pressure in the engine turbopumps caused by a filter blockage. As a result, only 2 of the 13 engines needed for landing successfully reignited, leading to the booster’s breakup upon impact with the ocean surface at an altitude of 462 meters.

Starship Upper Stage Achievements and Challenges

The Starship upper stage successfully separated from the Super Heavy booster and achieved its intended suborbital trajectory. During the coast phase, Starship demonstrated the first test of its payload bay door operation in orbit and completed a cryogenic propellant transfer test, moving approximately ten tons of liquid oxygen from the header tank to the main tank.

However, Starship encountered attitude control problems during its coast phase, leading to high roll rates that could not be corrected, likely due to clogging of the roll control thrusters. This issue prevented the planned in-space burn of a sea-level Raptor engine. As Starship began its reentry into Earth’s atmosphere, the inability to maintain proper orientation caused the vehicle to enter sideways and engines first, exposing both the heat shielded and unprotected areas to much higher than anticipated heating. The spacecraft broke apart during reentry and was lost.

Starlink Connectivity Success

Despite the challenging reentry conditions that typically result in communication blackouts, Starship managed to maintain a live video feed through the Starlink network. This was accomplished using a series of ground stations along the vehicle’s trajectory and NASA’s Tracking and Data Relay Satellite (TDRS) system, marking a notable achievement during the IFT-3 mission.

Improvements and Fixes for Future Flights

Following the IFT-3 mission, SpaceX conducted a thorough investigation to identify the root causes of the Super Heavy booster’s loss of control and Starship’s attitude control issues during reentry. The company has implemented several hardware and software modifications to address these challenges in future flights:

1. Upgrades to the hardware inside the Super Heavy booster’s oxygen tanks to improve propellant filtration capabilities and prevent engine turbopump pressure loss.
2. Enhancements to the Raptor engine startup sequence and software to increase reliability during landing burn conditions.
3. Addition of more roll control thrusters on upcoming Starships to improve attitude control redundancy.
4. Upgrades to roll control thruster hardware for improved resilience against blockages that likely caused the loss of control during IFT-3’s reentry.

SpaceX is preparing for the fourth integrated flight test (IFT-4), which could occur as early as June 5, 2024, pending regulatory approval and the completion of the IFT-3 mishap investigation. The company has several Starship and Super Heavy vehicles in various stages of production, enabling a rapid iterative testing approach.

To achieve the ambitious goals set for the Starship program, including NASA’s Artemis missions and eventual Mars colonization, SpaceX will need to demonstrate consistent success in launching, recovering, and reusing both the Super Heavy booster and Starship upper stage. Overcoming the challenges encountered during IFT-3 and implementing the identified improvements will be critical in paving the way for future achievements in the realm of fully reusable heavy-lift spacecraft.

Reference: SpaceX press release