A critical test fired Saturday with the four main engines powering the first stage of NASA’s gigantic Space Launch System lunar rocket is the last major hurdle to the costly, often delayed launch of the fully mounted booster on an unmanned test flight late this year.
The upgraded Aerojet Rocketdyne RS-25 engines are bolted on top of the massive B-2 test rig at NASA’s Stennis Space Center in Mississippi and are expected to fire for eight minutes from approximately 5:00 p.m. EST, the same duration needed for an actual flight. .
Including shuttle flights and post-shuttle ground tests, RS-25 engines have been started more than 3,000 times to date and fired more than 18,000 minutes in total, but never four at a time and never with a missile the size of the SLS. The goal is to test the performance of the stage as a whole under flight conditions.
NASA
“This will be our first test of all four RS-25 engines fired simultaneously in this new Space Launch System configuration,” said Jeff Zotti, Aerojet Rocketdyne RS-25 Program Director. “We are all looking forward to seeing the nuclear phase of the world’s most powerful missile go off for the very first time.”
The flight version of the SLS will feature two 17-story Northrop Grumman strap-on solid fuel boosters, each generating 3.6 million pounds of thrust; the four RS-25s, generating 1.6 million pounds of thrust; a second stage on hydrogen; an Orion crew capsule and a flight system.
The missile weighs 5.75 million pounds, is 322 feet long, and generates 8.8 million pounds of thrust at launch, making it the most powerful operational missile in the world and the most powerful US missile ever. Even more powerful variants are planned by NASA for its Artemis lunar program, boosting launch thrust to a whopping 9.5 million pounds.
For Saturday’s so-called “green flight”, the 212-meter-high, 27.6-meter-wide first stage of the Boeing-operated SLS missile will be tested as a fully operational supercharger, loaded with 537,000 liters of liquid hydrogen and 196,000 liters of liquid oxygen for a scheduled test firing of 485 seconds.
With the stage locked all over the test bench, new state-of-the-art engine computers will slow the main engines down to 95% thrust for about a minute into the test. They will do the same during actual flight to reduce stress on the rocket as it passes through the area of maximum aerodynamic pressure.
The 7,775-pound engines, which previously helped power 21 shuttle launches, will also move hydraulically gimbal or at specific times to commanded positions to verify their ability to accurately steer the rocket as it climbs into space, both early in flight as later in flight. the ascent.
The engine nozzles have new insulation to protect them from the heat they will eventually experience from the nearby 5,000-degree solid rocket amplifier exhaust plumes.
NASA
During the ground shake test, sensors will monitor other voltages and voltages, temperatures, propellant flow rates, pressures and a variety of other parameters to ensure the rocket is ready for launch on the first Artemis lunar mission at the end of this year.
Equally important, the test will verify the performance of the missile’s complex flight computer system and software, along with pre-flight management and propulsion safety systems.
“The test is scheduled for 485 seconds,” said Julie Bassler, SLS principal stage manager at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “The stage is equipped with more than 1,400 sensors, including pressure, temperature, accelerometers and strain gauges.”
“With this hot fire, there is a lot of data, including how the avionics and software control and control are performing with the integrated core stage and engine propulsion system,” Bassler said, adding, at this core stage. So this is a huge milestone for us. “
John Shannon, Boeing SLS program manager, a former space shuttle flight director: “This is the most heavily instrumented vehicle we’ll ever fly. So we’re getting a huge amount of technical data.”
Assuming the green run test goes well and no major problems occur, NASA executives hope to ship the SLS stage to Kennedy Space Center by barge in February.
Once there, the podium will be attached two solid fuel boosters is currently being assembled or “stacked” on a mobile launch pad in the cavernous Vehicle Assembly Building. The already complete upper stage is mounted on top of the core and the missile is crowned by a Lockheed Martin Orion crew capsule and accompanying flight system.
The assembled missile and launch pad are then towed by a high-powered crawler transporter to pad 39B and readied for flight. Unlike SpaceX rockets and others in development, the SLS is not reusable and will destroy the first stage booster and its engines when released back into the atmosphere after the ascent to space.
NASA hopes to launch the rocket on its maiden flight by the end of this year and send the unmanned Orion capsule on a flight 40,000 miles past the moon and back. What happens next depends largely on how the Biden administration prioritizes space.
NASA
NASA is currently under a Trump administration schedule calling for the first piloted SLS-Orion flight – Artemis 2 – in 2023, followed by a moon landing with the third SLS rocket by the end of 2024.
But that scheme assumes funding to develop a new lunar lander. The program has not yet received the required budget of Congress, and it is not yet known what level of support the Biden administration will provide.
The SLS team, for its part, is optimistic that the first Artemis rocket will be ready for launch before the end of the year.
“This powerful rocket will enable us to support the agency and the deep space mission from the land to the moon and beyond,” said John Honeycutt, NASA SLS program manager at Marshall.
But it was a rocky road.
The development program is well above budget and at least two years behind schedule. NASA’s Inspector General reported last March that total SLS program costs were expected to rise above $ 18 billion by the time the Artemis 1 missile finally takes off.
The delays and high costs have sparked debate about the need for the SLS to transport astronauts to the moon, given the availability of less powerful but much cheaper SpaceX Falcon Heavy rockets and other heavy-lift boosters now in development. But NASA executives say the SLS is the only short-term rocket available that can accommodate the Orion crew capsule and other major components intended for the Artemis program.