Starship, Super Heavy Complete Flight Test With Controlled Splashdowns

Hoping to speed up turnaround time between flight tests of its Starship-Super Heavy launch system, SpaceX asked the FAA to consider three potential endings for the Integrated Flight Test-4 mission that would not trigger a mandatory mishap investigation.

As it turned out, SpaceX did not need the waivers. Integrated Flight Test-4 (IFT-4), which took place on June 6 from Boca Chica Beach, Texas, completed a full-duration, 65-min. mission, with both the Super Heavy first stage and the Starship upper stage making controlled splashdowns in the ocean.

• Musk eyes booster touchdown on launchpad for next flight
• Starship steering fin was nearly severed

Despite losing one of its 33 methane-burning Raptor engines, Super Heavy released Starship in position to reach its intended trajectory, then separated and completed a successful flip maneuver, boostback burn and—for the first time—a landing burn. Twelve of the expected 13 Raptor engines fired for the landing burn, allowing the 233-ft.-tall vehicle to hover over its splashdown zone in the Gulf of Mexico before toppling over about 7 min. 30 sec. after launch.

To reduce its mass ahead of the landing burn, the Super Heavy jettisoned the vented hot-stage ring that protects the vehicle while engines on the still-attached upper stage ignite, pushing Starship away from the booster. SpaceX says it is working on a lighter-weight ring that will remain attached.

The booster’s performance spurred an emboldened Elon Musk, the founder, CEO and chief technology officer, to suggest that SpaceX could try to land the next Super Heavy on the launchpad. “I think we should try to catch the booster with the mechazilla arms next flight,” Musk wrote on the social media site X, referring to a pair of chopstick-like arms on the launch tower.

Meanwhile, Starship’s six Raptor engines fired to put the spacecraft into its intended slightly suborbital trajectory, 132 mi. above Earth. SpaceX chose the flight path to avoid the need for a deorbit burn on IFT-4, reducing public safety concerns as it continues to develop technologies for reliable reentry.

During its last flight test on March 14, Starship reached its intended trajectory but began to roll, resulting in an off-nominal reentry that caused higher-than-anticipated both protected and unprotected areas of the ship. It broke apart about 40 mi. over the Indian Ocean, bringing IFT-3 to an end 49 min. after liftoff.

The most likely cause of the attitude-control problem was clogging of valves responsible for roll control, SpaceX said. Additional roll-control thrusters and upgraded hardware to resist blockages were added for IFT-4.

The stainless-steel ship survived the near-3,000F reentry heat despite severe damage to at least one steering fin. Then, for the first time, Starship conducted a landing burn, setting the stage for a relatively soft splashdown in the Indian Ocean, about 3.7 mi. away from its intended target, ending IFT-4 at 9:55 a.m. EDT.

Future Starship vehicles will have their forward flaps shifted leeward to improve reliability and to ease manufacturing and delivery of payload to orbit, Musk noted.

For IFT-4, SpaceX tested one thin Starship heat shield tile and removed two tiles completely to measure reentry temperatures in those locations. Starship is covered with about 18,000 ceramic tiles to protect against reentry heating. “Despite loss of many tiles and a damaged flap, Starship made it all the way to a soft landing in the ocean,” Musk wrote.

“The ship would have failed on reentry if made of aluminum or carbon fiber, as they can’t take the heat,” he added. “Switching to ultra-hard, cold-rolled stainless steel for Starship is what led me to make Cybertruck out of it, too.”

Musk also founded and runs Tesla, which manufactures the Cybertruck electric vehicle.

SpaceX had asked the FAA not to require a mishap investigation, such as what followed its three previous flight tests, if Starship’s thermal shield failed due to high-heating, if the flap system was unable to provide sufficient control under high dynamic pressure or if Starship’s engine system failed during the landing burn. The FAA agreed that if one of these scenarios occurred, “an investigation will not be required, provided there was no serious injury or fatality, no damage to unrelated property and no debris outside designated hazard areas.”

SpaceX is looking to launch IFT-5 as early as mid-July.