SpaceX will begin building a third prototype of its Starship reusable launch vehicle destined to be tested in space.
CEO Elon Musk said construction of this version of Starship -- given the designation "SN1" -- should be finished and ready for testing by June at the earliest based on the current development schedule. SN1 is designed for high-altitudes and testing in low Earth orbit (LEO), which is the Earth-centered orbit with an altitude of 2,000 km or less. It will be built at the company's Texas facility.
The announcement of the next major phase in the development of Starship was made after a successful test-to-failure Tuesday of a header tank that withstood a maximum pressure level of 8.5 bar before failing. The result easily exceeded the 6 bar pressure rating required for an orbital flight test of Starship. It also matched the required standard for a human-rated spacecraft, which is 8.5 bar.
SpaceX previously tested pressure levels for this tank at both room temperature and at cryo, or the extremely cold levels more closely resembling conditions the vehicle will encounter in space. Musk said the deep cold actually increases the resilience of Starship components made out of steel.
Starship will be protected by a stainless steel exterior surface, which Musk said will cut cost while also providing log-lasting durability and re-usability. Starship will eventually replace the company's Falcon series of launch vehicles.
Musk tweeted the results of that intentional test-to-destruction just a few hours after it was completed. He said SpaceX's upgraded production and integration techniques enabled the tank to survive pressures almost 20% greater than the minimum Starship will need to perform orbital launches.
Musk pointed out the tank reached a maximum sustained pressure of 7.1 bar (103 psi), which is 18% more than the operating pressure (6 bar/87 psi) he says Starship prototypes will need to begin orbital test flights. At 7.1 bar, the test tank withstood a massive 20,000 metric tons (45 million lbf) of force spread out over its interior surfaces.
In its fully operational form, Starship will have a diameter of 30 feet (9 meters) and will stand 160 feet tall (50 m). It will be a fully reusable spacecraft powered by six methane/oxygen-propellant Raptor engines. Total Starship thrust is about 2,600,000 lbf.
Starship will become the primary SpaceX orbital vehicle. It will replace the current Falcon 9 launch vehicle and Dragon 2 fleet. In November 2019, Musk estimated the cost for a Starship launch might be as low as $2 million.