Enlarge / A view into the maw of SN4, showing a single Raptor engine mounted inside.


For the first-time, a full-scale prototype of SpaceX’s Starship vehicle lit its engine on Tuesday evening. After ignition, it appeared that the Raptor rocket engine burned for about 4 seconds. At the end of this test at the South Texas Launch Site, the vehicle still stood. About 90 minutes after the test, SpaceX founder and chief engineer Elon Musk confirmed the test firing was good, saying, “Starship SN4 passed static fire.”

Tuesday night’s test, which took place at 8:57pm CT local time in Texas (01:57 UTC Wednesday), occurred eight days after a successful pressurization test of this Starship prototype, known as SN4. Engineers will now review the data before possibly performing another static fire test, or a small hop. Ultimately, if this vehicle survives additional testing, it may make a 150-meter hop above the scrubby Texas lowlands.

This test also took place less than a week after NASA awarded SpaceX a $135 million contract to develop Starship as a Lunar Lander—a vehicle for carrying cargo and crew from lunar orbit down to the surface, and back. Although Starship is the most ambitious of three landers NASA is considering as part of its Artemis Program, it is also the only one actively testing full-scale prototypes.

Last August SpaceX flew a stubby vehicle dubbed Starhopper with a single Raptor engine. The goal of this vehicle was to test basic plumbing for the Raptor engine, and to see if its flight could be controlled for a safe ascent and descent. Although the Starhopper made a hard landing, it survived this test, and SpaceX moved on to build full-scale prototype of Starship.

Since November 2019, the company has lost three full-scale Starship prototypes during cryogenic and pressure tests. The most recent failure came on April 3. SN4 is the first vehicle to survive pressure testing to advance to further work. Now it has taken the critical step of igniting at liftoff pressures—a stiff test given the challenges of working with super-chilled fuels at high pressure—and then safely shutting down.

SN5 waiting in the wings

The vehicle on the pad in Texas is not the full configuration of Starship, lacking a nose cone, flaps, and other features needed for flight. However, it includes the bulk of the vehicle, including its liquid methane and liquid oxygen tank structure. These propulsion guts are the most difficult parts of a rocket to control, and static fire testing them is the ultimate test.

As part of its fast, iterative design process, SpaceX has already stacked SN5, the next Starship prototype. It could very well fly higher than SN4, providing SpaceX engineers ever more data as they seek to understand their new, powerful rocketship.

Starship is the “upper stage” of a two-part, fully reusable launch system that SpaceX is developing. The company’s ultimatey goal is for the “Super Heavy” rocket to boost Starship into orbit, where this vehicle can either carry cargo to some destination or carry dozens of passengers.

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