Engineers revised the refueling timeline for NASA’s giant Artemis moon rocket to correct the engine cooling problemMonday. The agency’s managers hope this opens the way on a long-awaited unmanned test flight,
NASA’s mission management team met Thursday to review launch preparations, the countdown timeline, and work to strengthen a seal where lines of liquid hydrogen feed propellant into the propulsion system pipes of the rocket.
Hopefully, engineers will begin pumping 750,000 gallons of cryogenic oxygen and hydrogen fuel into the two stages of the Space Launch System (SLS) rocket around 6:00 am EDT on Saturday,for take-off at 14:17, opening a two-hour window. Meteorologists predict a 60% chance of favorable weather conditions.
But the launch assumes engineers fix the problem that blocked Monday’s attempt, when the four main-stage RS-25 engines never reached the proper level of pre-flight cooling to condition them to the ultra-low temperatures of their propellants. of liquid oxygen and hydrogen.
Such conditioning is in part necessary to ensure that the bearings in the engine’s powerful turbopumps remain within tight operating tolerances when suddenly spinning to supply propellants to the combustion chamber, starting approximately six seconds before takeoff.
Conditioning is done by routing the propellant through the low and high pressure fuel pumps of the engine, a procedure known as “kickstart purge” which circulates cold liquid hydrogen through the lines. In the process, the liquid propellant expels, or “purges” the lines of hotter hydrogen, some of which may have turned into gas.
During Monday’s launch attempt, three of the engines nearly hit the minus 420 degrees Fahrenheit target on the hydrogen side, but engine No. 3 failed to exceed minus 380 degrees. Engineers suspect a faulty temperature sensor, because other measurements indicate good cooling
To be safe, they have revised the refueling timeline for the second launch attempt and will start the hydrogen kickstart purge earlier than expected, allowing more time for the propellant to cool the hardware. Later in the countdown, the hydrogen tank will be pressurized to flight levels, forcing more hydrogen through the lines to aid the cooling process.
A similar procedure was used last year prior to a main stage engine ignition test and there were no problems. The launch control software will be adjusted to ignore data from the suspect sensor.
If it works, the weather works together and no other problems occur, the countdown should finally hit zero, kicking off an unrivaled shocking spectacle since NASA’s legendary Saturn 5 moon rockets took the Apollo astronauts to the moon five decades ago.
Generating 8.8 million pounds of take-off thrust from two strap-on boosters and four shuttle-era engines, 15% more than the Saturn 5, the SLS rocket is the most powerful rocket ever built by NASA and its contractors.
After an eight-minute climb to an initial elliptical orbit, the central stage will fall and the upper stage SLS will push the unmanned Orion capsule and its European Space Agency-supplied service module onto a trajectory for a close lunar overflight the next. September. 8.
The service module’s engine will put the aircraft in a distant orbit around the moon and return it to Earth for landing in the Pacific Ocean, west of San Diego, on October 11 at around 2:10 pm EDT.
The primary objectives of the flight are to verify the performance of the SLS rocket and to test the Orion spacecraft in deep space. The top priority is testing its heat shield, which must withstand re-entry temperatures of up to 5,000 degrees Fahrenheit during the capsule’s high-speed return to Earth.
If Flight Artemis 1 goes well, NASA plans to launch four astronauts on a flight around the moon in 2024, followed by a landing near the moon’s south pole.when the first woman and the next man rise to the surface.
NASA plans annual flights to the lunar surface and visits to a small space station orbiting the moon to carry out long-term exploration and to test hardware and procedures that will be required for any flights to Mars.
While there are no such flights to the Red Planet at this point, NASA sees the moon as a critical first step towards achieving that long-range goal.
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