Two months after an initial test fire ended prematurely, NASA plans to re-ignite the core stage of the first Space Launch System rocket with a heavy lift on Thursday for an eight-minute burn to confirm it is ready to ship to it. Kennedy Space Center before launch. preparatory work.
The critical hot fire test is scheduled during a two-hour period beginning at 3:00 p.m. EDT (2:00 p.m. CDT; 1900 GMT) on the B-2 test rig at NASA’s Stennis Space Center in southern Mississippi.
If all goes to plan, the rocket’s four liquid-fired Aerojet Rocketdyne RS-25 engines will fire for about eight minutes, the same time they will fire when the Space Launch System is firing away from Kennedy Space Center.
Once the test firing is complete, ground crews inspect the Boeing-made nuclear stage, remove it from the firing stand, and place it on NASA’s Pegasus ship for shipment to the Florida launch site for attachment to the rocket’s two side-mounted solids . rocket boosters, upper stage and an Orion capsule that propels the SLS on a mission to the moon.
The fully assembled missile will be approximately 322 feet or 98 meters high. Earlier this month, NASA completed the stacking of the two Northrop Grumman-built 17-story solid rocket boosters at the Vehicle Assembly Building in Kennedy. The boosters will provide most of the 8.8 million pounds of thrust the SLS will produce at full power, more than any US missile in history.
The often-delayed Space Launch System is a centerpiece of NASA’s Artemis program, which aims to return astronauts to the moon. The SLS will launch Orion crew capsules with up to four astronauts on lunar expeditions, starting with the second SLS flight.
The first SLS / Orion mission, called Artemis 1, will not carry astronauts. The core stage being tested on Thursday is the same missile that will fly on Artemis 1.
NASA attempted to fire an eight-minute test with the SLS core stage on Jan. 16, but the four RS-25 engines stalled just over a minute after firing. Engineers found the cause of the premature failure in a hydraulic system parameter that triggered an overly conservative setting for the test, the final phase of a “Green Run” test and checkout campaign for the SLS core phase at Stennis.
The central stage hydraulics power actuators that spin the four RS-25 motors, or gimbal, to steer the missile after launch.
Managers want at least four minutes of run time on the RS-25 engines in the second hot fire test to gather enough data to build confidence in the rocket’s performance before shipping the stage to the Kennedy Space Center. But ideally, the test will run for the full 485 second scheduled duration.
The four RS-25 engines on the first SLS core stage are remnants of the space shuttle program. They all flew multiple shuttle launches, and engineers fitted the engines with new computers and software to fly on the Space Launch System, plus thermal insulation to protect the RS-25s from the overheated exhaust plume from the fixed boosters.
Three of the main engines launched on every shuttle flight, but four RS-25 engines had never been ignited together on the same rocket until the abbreviated test on January 16. The four engines generate about 1.6 million pounds of thrust at sea level and operate at slightly higher throttles than during the shuttle era.
Here’s a replay of the Space Launch System core stage’s first hotfire test, which was cut short to a scheduled eight-minute shooting just over a minute.
The missile and engines are safely disabled. NASA is planning a post-test media briefing tonight. Https://t.co/B639YAgQec pic.twitter.com/FXHuxAV7ok
– Spaceflight Now (@SpaceflightNow) January 16, 2021
Each RS-25 engine weighs approximately 7,800 pounds or 3.5 tons. Unlike the space shuttle, the SLS core stage is disposable and the motors are not reused.
NASA’s test team at Stennis will begin loading liquid hydrogen and liquid oxygen into the 65-meter rocket early Thursday. The cryogenic propellants are stored at minus 423 degrees Fahrenheit and minus 297 degrees Fahrenheit (minus 253 and minus 183 degrees Celsius).
Six propellants will be docked in the pivot bowl next to the B-2 test rig to feed more than 733,000 liters of propellants into the rocket, enough to fill 63 large tankers.
In addition to engine data, engineers will monitor how the missile’s flight computers, avionics, and hydraulic systems function during the hot fire test. More than 500 sensors collect information about temperatures, pressures, structural loads and other parameters.
Assuming the nuclear stage performs well on Thursday, NASA hopes to have the missile on Kennedy by the end of April.
NASA planned to run a second Green Run hot fire test last month, but managers have delayed firing the engine to investigate a trapped liquid oxygen that is causing the propellant to flow to one of the four RS. 25 engines.
Engineers repaired the valve and announced earlier this month that preparations for the second Green Run hot fire test had resumed.
The Green Run hot fire test has been delayed for more than six months since the SLS core phase arrived at Stennis in January 2020. A temporary break in work due to the COVID-19 pandemic initially delayed preparations for the test, and a series of hurricanes and tropical storms that hit the Gulf Coast last year also slowed work at the Stennis Space Center.
NASA was ordered by the Trump administration to land a crew near the south pole of the moon by the end of 2024. The Biden government has expressed support for the Artemis program but has not set a timetable for a manned moon landing mission.
The planning target for 2024 slipped away before the end of the Trump administration. Congress approved just a fraction of the funding that NASA had requested in fiscal year 2021 for the development of the Artemis program’s human-rated lunar landings.
Kathy Lueders, head of NASA’s human space flight directorate, said last month that the SLS Green Run delays were “very, very difficult.”
“This is the last stretch that we are waiting for us to go to the Cape to fly,” said Lueders. She said NASA still “hopes” to fly the first SLS rocket by the end of this year.
But it is more likely that the Artemis 1 test launch will not take place until early 2022. The Artemis 2 mission is scheduled to transport four astronauts around the moon by 2023, and NASA plans to launch the first elements of a mini space station called the Gateway in 2024.
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