SpaceX’s Starship, the largest and most powerful rocket ever built, is supposed to land NASA astronauts on the surface of the moon in a couple of years.
Even more ambitiously, Elon Musk, who owns and runs SpaceX, has said that the company would send about five Starships to Mars next year — sans astronauts, but with Optimus robots built by his electric car company, Tesla.
The past two test flights of Starship have ended in explosive failures, and a third failure during the next launch, planned for Tuesday evening, would be embarrassing for SpaceX and Mr. Musk.
Mr. Musk, however, seems to relish taking on doubters. He plans to give a talk to SpaceX employees titled simply “The Road to Making Life Multiplanetary,” at 9 p.m. Eastern time. The talk had been scheduled for 1 p.m., but it was pushed back several times until Mr. Musk announced that it would be postponed until after the launch.
When is the launch and how can I watch it?
The launch window opens at 7:30 p.m. Eastern time for the ninth test flight of Starship to lift off from SpaceX’s Starbase site in South Texas. SpaceX will provide live coverage on its website beginning about 30 minutes before liftoff.
What happened during the last flights?
SpaceX takes pride in its “fail quickly and fix quickly” approach to rocket design, so it is not surprising that none of the eight test flights so far have worked perfectly. But the last two — flight seven in January and flight eight in March — were more disappointing. They could not repeat the successes of earlier test flights.
For both flights, the upper-stage vehicles, known as Starships, exploded during ascent. Showers of falling debris over the Atlantic Ocean surprised sky watchers in Caribbean countries and Florida, and disrupted air traffic in the region. No one was injured.
In contrast, the vehicles used in flights four, five and six made it into space, coasted halfway around the world, survived re-entry into the atmosphere and simulated landings in the Indian Ocean.
In flights seven and eight, both explosions occurred at about the same point in the flight, just before the second-stage engines cut off. But the causes were “distinctly different,” SpaceX said in an update last week.
For the seventh flight, SpaceX said that the probable cause was stronger than expected rhythmic oscillations. The vibrations caused leaks of propellant that caught fire.
Fixes intended to damp the vibrations worked during the eighth flight, SpaceX said.
However, during the eighth flight, a flash was seen near the bottom of the second-stage vehicle near one of the center engines. That engine then failed. Three other engines then shut down, and SpaceX lost control of the vehicle about nine and a half minutes after launch.
SpaceX said the most probable cause was a hardware failure in one of the engines “that resulted in inadvertent propellant mixing and ignition.”
While the upper-stage vehicles failed during the last two launches, the giant first-stage boosters, known as Super Heavy, each successfully returned to the launch site, where they were caught in midair by giant mechanical arms.
What will be different during this launch?
SpaceX performed more than 100 test firings of its Raptor engines, trying to understand what had failed. It made improvements to the design so that the next version of Raptor, which was already under development, would be more reliable.
This test will try to conduct tests that were left undone during the two previous flights. Those include deploying simulators of SpaceX’s next-generation Starlink internet satellites and tests of the spacecraft’s thermal protection system.
Instead of catching the Super Heavy booster this time, SpaceX has a different, more ambitious plan: It is reflying the booster from flight seven, hoping to demonstrate that its design is, indeed, reusable. SpaceX said a large majority of the hardware, including 29 of the 33 Raptor engines, were used during the earlier flight.
The booster will also attempt several experiments to make re-entry through the atmosphere more efficient. It will also test whether it can still perform a landing maneuver if one of the center engines shuts down and a different engine has to be used.
The booster will set itself down in the Gulf of Mexico.
Why did the F.A.A. approve the launch after two failures?
The F.A.A. approved the launch last week, saying it was satisfied that SpaceX had addressed the causes of the earlier mishaps and that the launch did not pose a danger to the public.
“The F.A.A. finds SpaceX meets all of the rigorous safety, environmental and other licensing requirements,” the agency said.
Kenneth Chang, a science reporter at The Times, covers NASA and the solar system, and research closer to Earth.
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