The world’s tallest rocket, SpaceX’s Starship, is set to fly once more. The main uncertainty for this fourth flight is whether it’ll survive atmospheric re-entry, a possibility that has SpaceX CEO Elon Musk particularly worried.
The challenge of re-entry. During its previous flight, Starship reached its target speed for the first time and traveled halfway around the world on a suborbital trajectory. However, a blockage to the valves responsible for Starship's roll control caused the spacecraft to start spinning out of control.
As Starship re-entered the atmosphere at full speed over the Indian Ocean, it encountered significant friction with the air, resulting in spectacular images of the ship surrounded by plasma. However, due to the roll control issue, the body was fully exposed, and the spacecraft didn’t survive. Ship 28 disintegrated at an altitude of 40 miles.
Expectations for Flight 4. If everything goes according to plan, Ship 29’s flight is will take place on Thursday, June 6. The ship is equipped with additional roll-control thrusters to prevent further loss of control. However, Musk is unsure about whether Starship will be able to complete atmospheric re-entry.
SpaceX’s CEO has tweeted multiple times in recent weeks to lower expectations of complete success in the fourth test. Musk has emphasized the spacecraft’s heat shield: “Unless we make the heat shield relatively heavy… we will only discover the weak points by flying,” he posted on May 30.
Starship’s unique heat shield. Starship’s heat shield consists of thousands of very lightweight octagonal ceramic tiles bonded to a secondary containment material on the rocket’s steel body.
Unlike the shield on SpaceX’s Dragon spacecraft, which regularly carries astronauts to the International Space Station, Starship’s heat shield is designed to be reusable. Notably, it doesn't need to be serviced not every six months, as was the case with the space shuttle, but every few hours.
Tile reliability problems. The weakness of in design is that some tiles break loose and fall off with the sudden movements of rocket liftoff, stage separation, and spacecraft re-entry.
Musk has made it clear that the secondary material can’t survive the “loss of a single tile,” so each piece, especially those angled over the spacecraft’s aerodynamic surfaces, is inspected individually to ensure that it’s attached to the Starship.
The real goal of Flight 4. Since the reliability of the heat shield remains in question, the goal of this week’s flight isn’t to make it through re-entry and land into the ocean in one piece, but rather to withstand the heat of air friction for a longer period of time.
If Starship makes it through the most heated phase of re-entry, Flight 4 will be a success for SpaceX on its usual trial-and-error schedule. At 5,000 tons, Starship is the largest flying object ever created. Whether it can land and fly again the next day depends on whether those tiles hold up.
Image | SpaceX
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