Starship succeeds on fourth flight test

In the days leading up to the Starship integrated flight test, there was a flurry of activity at SpaceX’s Starbase facility in Boca Chica, Texas. Teams meticulously prepared the Orbital Launch Pad, fueling systems, and the flight hardware itself – Booster 11 and Ship 29.

The booster, standing 71 meters tall and featuring 33 Raptor engines, underwent a static fire test on April 5th to verify the readiness of its propulsion system. Ship 29, the 50-meter-tall upper stage, also completed a series of engine tests, including a spin prime of all six Raptor engines on March 11th, followed by two static fires on March 25th and 27th.

As the launch date approached, road closures and evacuation procedures were implemented in the surrounding areas due to the increased hazard area around the launch site. The orbital tank farm, pre-chilling valves, and pumps were activated hours before the scheduled liftoff, preparing the complex systems for propellant loading.

During the countdown, a poll was conducted to verify that all systems were ready for flight. Once clearance was given, the meticulous process of loading liquid methane and liquid oxygen into the vehicles began. The ship was fueled first, followed by the booster approximately seven minutes later, as the current tank farm configuration allowed for faster booster fueling.

• Around T-19:40, the engines on both stages began to be chilled, preparing them for the cryogenic propellants.
• At T-3:20 for the Ship and T-2:50 for the Booster, the tanks were taken up to flight pressure, signaling the completion of the propellant loading phase.
• At T-30 seconds, the SpaceX launch director verified the final “GO” for launch.
• At T-10 seconds, the massive deluge system at the base of the Orbital Launch Pad was activated, firing water against the thrust of the engines to protect the launch infrastructure.

With all systems ready and the countdown proceeding smoothly, the stage was set for an exciting and pivotal flight test in the Starship program.

At liftoff, all 33 Raptor engines on Booster 11 ignited in a staged sequence, producing a combined thrust of 7,590 tons. One outer engine quickly shut down after liftoff, a phenomenon previously seen on the first Starship flight. Despite this minor setback, the massive vehicle continued its ascent, powered by the remaining 32 engines.

Ship 29, riding atop the booster, ignited its six Raptor engines at T+2:41 during the hot staging maneuver. This event separated the two stages while both sets of engines were still firing, allowing the ship to continue its journey independently.

After separation, Booster 11 initiated its boostback burn, firing ten additional engines to reorient itself for a controlled descent. This burn lasted over a minute, until T+3:52, when the hot staging ring was jettisoned just two seconds later at T+3:54. With the ring gone, the booster began its flip maneuver, positioning itself for the final landing burn.

At T+6:43, 13 of the booster’s Raptor engines reignited for the landing burn startup. However, only 12 of these engines successfully ignited, forcing the booster to compensate for the lower thrust. Despite this setback, Booster 11 executed a remarkable first – a soft splashdown in the Gulf of Mexico, marking a significant achievement for the SpaceX team.

Meanwhile, Ship 29 continued firing its engines until T+8:23, propelling it onto a near-orbital trajectory with a perigee just below Earth’s surface. After a 40-minute coast phase, the ship began its atmospheric reentry at T+47:25, subjecting it to intense heat and plasma formation.

During this critical phase, one of Ship 29’s forward flaps sustained extensive plasma damage, shedding large chunks of material. However, the vehicle’s control systems and remaining flap actuation allowed it to maintain stability and execute the signature “flip-and-burn” maneuver, transitioning from a horizontal orientation to a vertical one for a controlled descent.

Remarkably, despite the compromised forward flap and red-hot surfaces, Ship 29 was able to reignite its sea-level Raptor engines and softly touch down in the Indian Ocean, bringing the fourth Starship flight test to a successful conclusion – albeit with likely breakup after tipping over due to the sustained damage.