December 4, 2020

SpaceX test-fires Starship prototype with three engines


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A view of the Starship SN8 prototype with three Raptor engines. Future Starship vehicles will have six Raptor engines, with three vacuum-rated engines with larger nozzles clustered around the three center engines optimized for sea level performance. Credit: Elon Musk/SpaceX

SpaceX fired three Raptor engines on a prototype of the company’s Starship vehicle Tuesday, accomplishing another milestone on the road toward testing of the methane-fueled rocket at higher altitudes.

The three Raptor engines ignited shortly after 4 a.m. EDT (3 a.m. CDT; 0800 GMT) Tuesday on a test stand at SpaceX’s Boca Chica development facility in South Texas. Webcasts of the testing showed the three engines briefly ignited with a flash of orange at the seaside complex.

Elon Musk, SpaceX’s founder and CEO, tweeted later Tuesday the engine firing, called a “static fire,” went according to plan.

“Data from 3 engine Starship static fire this morning looks good,” Musk tweeted. “Proceeding with nosecone mate.”

The test vehicle that fired up Tuesday morning is designated SN8. After additional testing, SpaceX aims to fly the prototype to an altitude of up to 50,000 feet, or 15 kilometers, higher than any Starship has flown before.

SpaceX flew two previous Starship test vehicles to 500 feet, or 150 meters, over the Boca Chica site Aug. 4 and Sept. 3. Those test flights were powered by a single methane-fueled Raptor engine.

The testing of the SN8 vehicle is the next step in SpaceX’s Starship development program, with three Raptor engines mounted at the base of the vehicle. The three throttleable Raptor engines, each capable of producing up to 500,000 pounds of thrust, will allow SpaceX to attempt more ambitious Starship test flights. The addition of fins will also aid in high-altitude, higher-speed flights.

Body flaps have already been installed on the SN8 test vehicle, and SpaceX teams at Boca Chica planned to add the stainless steel nose cone this week after the successful static fire test Tuesday. With the nose cone added, the Starship vehicle will reach a height of around 164 feet, or 50 meters.

The vehicle measures around 30 feet (9 meters) wide, about one-and-a-half times the diameter of a Boeing 747 jumbo jet.

A previous Starship test vehicle. Credit: SpaceX

Eventually, SpaceX will mount six Raptor engines at the base of future Starships. Three of the Raptors will be similar to the existing engine models flown to date, while three will be fitted with much larger nozzles.

The engine version with the nozzle extension is known as the Raptor Vacuum, or RVac. SpaceX recently announced on Twitter that the first RVac engine has shipped from the company’s headquarters and Raptor engine factory in Hawthorne, California, to a test site in McGregor, Texas, to begin a series of test-firings.

The RVac engine configuration is needed to power Starship launches into orbit.

The pace of Starship development has hastened in recent months as SpaceX builds out a sprawling production facility at Boca Chica, located just east of Brownsville, Texas, on the Gulf of Mexico near the U.S.-Mexico border.

Once operational, the Starship could carry more than 100 metric tons, or 220,000 pounds, of cargo to low Earth orbit, more than any rocket in the world. With life support systems and in-space refueling, Starship missions could eventually transport people to the moon, Mars, and other distant destinations.

Starship is central to the vision of Musk, who established the company with a mission of sending people to Mars. Future Starships could cruise to Mars with up to 100 people, Musk says.

Musk has emphasized SpaceX’s progress on production capabilities and ground infrastructure, allowing the company to rapidly build prototypes, test them, and introduce upgrades and modifications on follow-on vehicles.

SpaceX has started building parts of the first Super Heavy booster, which will be the first stage on the full-scale Starship vehicle. Starships like the vehicles currently undergoing testing will serve as the upper stage stacked on top of the Super Heavy.

Like the early Starship test flights, the first Super Heavy prototypes will fly to low altitudes with a subset of Raptor engines, beginning with two or four of the SpaceX-made powerplants, Musk said. The final Super Heavy design will have 28 Raptor engines.

For an orbital mission, the Starship will also need a heat shield for re-entry. The entire stack will stand around 394 feet (120 meters) tall, according to SpaceX’s website.

Both stages will come back to Earth for propulsive landings, much like the first stage on SpaceX’s partially reusable Falcon 9 rocket. That will make the Super Heavy and Starship fully reusable.

Artist’s illustration of SpaceX’s Starship on the lunar surface. Credit: SpaceX

While cautioning that his schedule predictions are “just guesses,” Musk said Oct. 16 that he is “80 to 90% confident that we will reach orbit with Starship next year.

“I’m 50% confident that we’ll be able to bring the ship and booster back,” Musk said in a discussion at the 23rd Annual International Mars Society Convention. “That’s more of a dicey situation. We’ll probably lose a few ships before we really get the atmospheric return and landing right.”

Musk said he believes SpaceX will be “doing high-volume flights probably in 2022, so a couple of years from now.”

“I’m trying to make sure that our rate of innovation increases, (and) it doesn’t decrease,” Musk said. “This is really essential. In fact, if we do not see something close to an exponential improvement in our rate of innovation, we will not reach Mars. A pure linear (rate of innovation) doesn’t get us there. I’ll be dead anyway before it gets there, if its pure linear. If it’s exponential … we could probably send an uncrewed mission (to Mars) in maybe four years.”

Musk said last year said the first orbital launch of Starship could happen in 2020. Despite the project’s fast rate of progress, SpaceX won’t meet that schedule.

Musk said Aug. 31 that SpaceX is not yet performing much development of the life support systems Starships will need to accommodate people. That will come after SpaceX can prove the vehicle can fly successfully.

SpaceX’s longer-term roadmap includes an in-orbit refueling capability to make trips to the moon possible. NASA selected SpaceX’s Starship vehicle in May as one of three contenders — alongside Blue Origin and Dynetics — for a human-rated lunar lander the space agency will fund for crewed moon missions later this decade.

The moon missions will require SpaceX to master in-orbit refueling between two Starships. Musk said he thinks SpaceX has a shot of accomplishing that in 2022.

When could SpaceX have a Starship prototype for a moon mission?

“Probably two or three years,” Musk said. “As soon as you’ve got orbital refilling, you can send significant payload to the moon — significant meaning 100 tons of useful payload at a shot.”

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Follow Stephen Clark on Twitter: @StephenClark1.


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