The booster is fitted with a piece of foam called a "nozzle plug," which protects it from heat, dust, and moisture, and is designed to fall apart during ignition. That's what you see exploding in this video, filmed on June 28 at Orbital ATK's test facility in Promontory, Utah.
Last year, NASA also tested its boosters, in order to evaluate how well they could perform in high temperatures. The test depicted here looked at the opposite, how boosters could perform in cold temperatures (around 40 degrees Fahrenheit).
When ignited, temperatures inside the SLS reached 6,000 degrees Fahrenheit. The foggy ring seen on the outside is condensed water vapor, created because of a pressure difference between the motor gas and normal air outside.
At full capacity, the SLS exerts 9.2 million pounds of thrust, more than thirty times the thrust of a 747 jet. The boosters tested here are responsible for more than 75 percent of that power.
This test is part of a series NASA has done in order to ensure all parts of the SLS are ready for interplanetary space travel.
The first time we'll hopefully get to see it in action is 2018, when NASA plans to send the SLS with the Orian spacecraft on an uncrewed flight. This was the last booster test necessary before that journey.
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