A critical test firing on Saturday on the four main engines that power the first stage of NASA’s lunar space launch system is the last major hurdle before the costly launch of the fully assembled engine, often delayed later this year on a flight of unmanned testing.
Stuck on the spot above the massive B-2 test stand at NASA’s Stennis Space Center in Mississippi, the updated Aerojet Rocketdyne RS-25 engines are scheduled to take off for eight minutes, starting at 5:00 p.m. EST, the same time required for a effective flight. .
Including shuttle flights and post-shuttle ground tests, RS-25 engines have been started more than 3,000 times so far and have been triggered for more than 18,000 minutes, but never four at a time and never with a rocket the size of SLS. The goal is to test the performance of the stage as a whole in flight conditions.
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“This will be our first test to fire all four RS-25 engines simultaneously in this new Space Launch System configuration,” said Jeff Zotti, director of Aerojet Rocketdyne RS-25. “We are all looking forward to seeing for the first time the center stage of the most powerful missile in the world.”
The flight version of the SLS will include two 17-stage Northrop Grumman solid-fuel amplifiers, each generating £ 3.6 million; the four RS-25s, generating a total of £ 1.6 million; a second hydrogen-fed step; an Orion crew capsule and an emergency evacuation system.
The rocket will weigh 5.75 million pounds, have a height of 322 feet and generate 8.8 million pounds at takeoff, making it the most powerful operational rocket in the world and the most powerful American rocket ever built. . Even stronger variants are planned by NASA for its monthly program Artemis, pushing the takeoff momentum to a staggering 9.5 million pounds.
For Saturday’s so-called “green race”, the first stage of the 212-foot-tall, 27.6-foot-wide SLS rocket will be tested as a fully operational booster loaded with 537,000 gallons of liquid hydrogen and 196,000 gallons of liquid oxygen for a planned 485-second test.
With the stage locked on the test stand throughout, the new state-of-the-art motors will speed up the main engines by up to 95% in one minute of testing. They will do the same during an effective flight to reduce the missile’s tensions as it passes through the region of maximum aerodynamic pressure.
The £ 7,775 engines, which previously helped fuel 21 shuttle launches, will also be hydraulic gimbal or move to commanded positions at specified times to test their ability to accurately steer the missile. during the ascent into space, both at the beginning of the flight and later in the ascent.
The engine nozzles have new insulation to protect them from the heat they will eventually experience from the 5,000-degree solid booster exhaust panels.
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Throughout the ground shake test, sensors will monitor other loads and stresses, temperatures, fuel flows, pressures and a variety of other parameters to ensure the rocket is ready for launch on the first Artemis moon mission later this year. .
Equally important, the test will check the performance of the complex rocket flight computer system and software, along with safety systems and pre-flight fuel management.
“The test is scheduled for 485 seconds,” said Julie Bassler, SLS stage director at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “The stage is equipped with over 1,400 sensors, including pressure, temperature, accelerometers and manometers.”
“With this hot fire, there is a lot of data, including how the command and control of the avionics and software will work with the basic integrated system and the engine’s propulsion system,” Bassler said, adding: “This running test Green is the first time we are launching at this basic stage. So this is a huge stage for us. “
John Shannon, the former space shuttle flight director, told Boeing SLS program manager: “This is the most powerful vehicle we will ever fly. So we will get an extraordinary amount of engineering data.”
Assuming the ecological rolling test goes well and no major problems are encountered, NASA managers hope to send the SLS stage by barge to the Kennedy Space Center in February.
Once there, the stage will be attached to two solid fuel boosters being assembled, or “stacked”, on a mobile launch pad in the cavernous building of the vehicle assembly. The already complete upper stage will be mounted above the core, and the rocket will be covered by a Lockheed Martin Orion crew capsule and its emergency evacuation system.
The assembled rocket and its launch pad will then be transported to pad 39B by a powerful crawler and ready for flight. Unlike SpaceX missiles and others under development, the SLS is not reusable, and the first-stage amplifier and its engines will be destroyed when they fall into the atmosphere after ascending into space.
NASA hopes to launch the rocket on its original flight later this year, sending the unmanned Orion capsule on a flight 40,000 miles beyond the moon and back. What happens next will largely depend on how the Biden administration gives priority to space.
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NASA is currently working on a Trump administration program that calls for the first manned SLS-Orion flight – Artemis 2 – in 2023, followed by a monthly landing using the third SLS rocket by the end of 2024.
But that program requires funding to grow a new moon lander. The program has has not yet received the necessary budget from Congress and it is not yet known what level of support the Biden administration will provide.
In turn, the SLS team is optimistic, the first Artemis rocket will be ready for launch before the end of the year.
“This powerful rocket will put us in a position to be ready to support the agency and the country’s deep space mission to the moon and beyond,” said John Honeycutt, NASA SLS program manager at Marshall.
But it was a rocky road.
the development program far exceeds the budget and at least two years ago. NASA’s inspector general reported in March last year that he expected the total costs of the SLS program to rise to more than $ 18 billion by the time the Artemis 1 rocket takes off permanently.
Delays and high costs have led to debates about the need for SLS to transport astronauts to the moon, given the availability of less powerful but much less expensive SpaceX Falcon Heavy missiles and other high-weight boosters under development. However, NASA managers say that SLS is the only missile available in the short term, able to accommodate the Orion crew capsule and other large components provided for the Artemis program.