Space

SpaceX test fires Starship's Raptor engine for deep space burns

SpaceX test fires Starship's R...
Render of SpaceX's Starship undergoing stage separation
Render of SpaceX's Starship undergoing stage separation
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Render of SpaceX's Starship undergoing stage separation
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Render of SpaceX's Starship undergoing stage separation
SpaceX's Raptor engines, a sea level variant on the left and a vacuum variant on the right, featuring a much larger nozzle
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SpaceX's Raptor engines, a sea level variant on the left and a vacuum variant on the right, featuring a much larger nozzle

SpaceX has notched up another milestone in the development of Starship, fixing its Raptor Vacuum engine to the spacecraft and test-firing it for the first time. This marks another important step in the company's ongoing efforts to reach Mars, with this larger engine variant to perform the important role of propelling the massive vehicle once it reaches outer space.

Starship is SpaceX's next-generation vehicle designed to transport people and cargo to the Moon and Mars, and back in May the company successfully flew it to high-altitude and landed it for the first time. The Raptor engines that propelled this test flight are what are known as sea level variants, which feature smaller nozzles designed to safely eject the exhaust gas at the atmospheric pressures found at sea level, while generating thrust to lift the rocket off the ground.

SpaceX's Raptor engines, a sea level variant on the left and a vacuum variant on the right, featuring a much larger nozzle
SpaceX's Raptor engines, a sea level variant on the left and a vacuum variant on the right, featuring a much larger nozzle

Because there is negligible atmospheric pressure in the vacuum of space, the engine nozzles that perform this role can be much larger, and in turn generate far more thrust. Starship's upper stage will carry three sea level Raptor engines, along with three vacuum Raptor engines with much bigger nozzles, which SpaceX began testing last year.

The tests that took place over the weekend saw one of these vacuum Raptor engines integrated into the Starship and successfully test-fired for the first time.

The final iteration of Starship's lower stage, meanwhile, the Super Heavy rocket, will use close to 30 Raptor engines to lift 100 metric tonnes to Earth orbit, making it the most powerful launch vehicle ever developed. SpaceX CEO Elon Musk said over weekend that the first orbital launch for the next-gen spacecraft could take place as early as November, if the company can gain the necessary approvals from the Federal Aviation Administration.

Source: Twitter (SpaceX)

4 comments
4 comments
mystixa
"...the engine nozzles that perform this role can be much larger, and in turn generate far more thrust. "

This is incorrect.

Rocket nozzles focus the burning gasses backward. In the atmosphere there is air pressure outside the nozzle that also constrains those gasses. That effectively does some of the nozzles work for free without adding weight. Thats why as you watch a rocket launch you'll see the gas plume get wider as the rocket increases altitude.

Nozzles in space are larger because they no longer have the benefit of this free 'air nozzle'. So they need to have a larger area to do the same job. Without the larger nozzle a significant amount of thrust would be directed sideways instead of to the rear. The overall thrust of the engine is the same.
Eddy
I think we should stop wasting money on projected one way trips for humans to distant planets except possibly for Moon exploration from which we have proved we can return without wasting most of our lives in travel time.
joe46
why not use a "spike" nozzle design, isn't that meant to be more efficient in a vacuum ?
Spikev
The Hygiene engine could be an option for faster, low-weight propulsion if the concept proves to have the efficacy that is statistically indicated. However, it is unknown whether USA will permit this type of non-chemical propulsion to be used; Few details are available about the hygiene engines and the concept is still untested.