Engine problem prevented US moon rocket from debut
NASA has postponed today's August 29, 2022, maiden flight of its SLS lunar carrier rocket, and the Orion spacecraft around the Moon on the Artemis I unmanned mission. The vehicle was supposed to take off from Launch Pad 39B at the Kennedy Space Center in Cape Canaveral, Florida. The space agency called for a postponement of Artemis I at 08:35 EST (12:35 GMT) on Monday, August 29, 2022, following a malfunction in the bleed of the RS-25 engine serial number 2058 “engine 3”.
The engineers were unable to cool the engine circuit (chill down procedure), resorting to bleeding the propellant liquid hydrogen through the engine, and closing the other three. “Launch controllers continued to assess why a bleed test to place the RS-25 engines at the bottom of the core stage in the proper temperature range for takeoff was not successful and ran out of time on the launch. two-hour launch window,” according to a space agency statement.
History of Engine 2058
RS-25 "2058" was part of six shuttle missions, including the delivery of the U.S. Harmony node and Japanese Kibo laboratory for the International Space Station (STS-120 and STS-124), as well as the final flight of the orbiter Discovery (STS-133).
The 'megarocket ', as the SLS is informally called on social media, is a rocket measuring 98.26 meters in length, 8.41 meters in diameter, and 2,608,156 kg of mass at take-off. The mid-stage engines and the two auxiliary boosters produce 4,309,127.5 kgf of thrust. It is capable of carrying a payload of 86 tons to low Earth orbit or 27 tons to the Moon.
During engine bleeds, hydrogen passes through the engine to condition it for launch; this is done by increasing pressure in the center stage tanks to bleed some of the chilled propellants into the engines to bring them into the proper temperature range for ignition.
The cold fluid circuit serves to 'accustom' the pipes to the low temperature of the propellants, avoiding a thermal shock in the combustion chamber housing and in the gas outlet nozzle. Both the chamber and the nozzle are cooled by the propellant, preventing them from being damaged by the heat of ignition. The hydrogen that passes through the engine piping when it is running returns in the form of gas to the engine circuit and to the tank, helping to pressurize.
The team also discovered a line of ice on the connecting flange between the ICPS stage and the transition cone that connects it to the central stage. "This ice that formed was essentially air that was being cooled by the tank and that got trapped inside a fissure in the foam," the space agency later said. At first, engineers thought that the ice could indicate the presence of a crack in the tank, but it turned out to be just in the outer polyurethane insulating foam. “Flanges are connecting gaskets that work like a seam on a shirt, they are affixed to the top and bottom of the inter-tank section so that the two tanks can be connected to it,” NASA said. The team announced that the issue was resolved as the crack did not indicate a leak.
Prior to the postponement, the countdown was extended to an unplanned hold while the release team worked on a troubleshooting plan.
The launch team needs to troubleshoot the engine and will keep the rocket in its current configuration to collect data and assess what needs to be done. Both the rocket and spacecraft, installed on Launch Complex Platform 39B, remain stable, according to space agency officials. "The team couldn't get over the engine bleed that wasn't showing the right temperature and ultimately the launch director called a postponement for the day," said launch control communicator Derrol Nail. Nail said the next available launch opportunity would be on the 2nd, but it wasn't certain that NASA would take advantage of that opportunity. “We should wait and see what happens to the test data they are collecting now and the decision that should be made by the release team on what to do from here.”
Weather conditions remained 80% favorable for a launch early in the window. But several problems arose after the rocket began to be fueled after midnight. Offshore storms with lightning potential prevented the team from starting the supply process, which was supposed to start at midnight, for about an hour. The ban was lifted at 01:13 ET, and the process began to fill the rocket's center stage with liquid oxygen and hydrogen. The team stopped filling the hydrogen tank twice due to an initial leak as well as a pressure spike, but the process resumed and started later for the upper stage, or ICPS interim cryogenic propulsion stage.
Next Launch window
The next possible takeoff date for Artemis I is 12:48 EST (16:48 UTC) on Friday, September 2nd. This release window extends to 2:48 pm EST, 18:48 GMT. After September 5th, the next release window would be September 19, 2022.
After that, another launch window will open at 5:12 pm EST and close at 6:42 pm EST on Tuesday, September 5th. However, it is possible that an additional supply test will be required, which could mean further delays. The long intervals between launch windows are due to the Moon's position relative to Earth and also to the flight plan. The trajectory of the spacecraft whose electrical system depends on solar energy should not take it through an eclipse - the moon's shadow - for more than 90 minutes. Launch opportunities are also limited by the moon's position and lighting conditions on re-entry, among other considerations. If the space agency can't launch until September 5, its next attempt will likely be in October.
Engineers were also working to find out what caused an 11-minute delay in communications between the spacecraft and ground systems. The issue may have affected the start of the final countdown – the countdown that starts when there are 10 minutes left before takeoff.
The statement by the Head of NASA
Space agency administrator Bill Nelson addressed the delay shortly after the announcement, stressing that Artemis I is a test flight. “We won't release until everything is right,” Nelson said. “They have a problem with the fluids bled into an engine. And it demonstrates that this is a very complicated machine, a very complicated system, and all these things have to work. You don't 'light the candle' until you're ready to go.” “Light the candle” is slang for starting the engines. As an astronaut, Nelson was on the 24th space shuttle flight, on the Columbia shuttle mission STS-61C, as a guest of NASA (he was a senator at the time). The launch was delayed four times and the fifth attempt resulted in an impeccable mission.
Vice President Kamala Harris and husband Douglas Emhoff visited the Space Center to watch the launch. Appearances by celebrities such as Jack Black, Chris Evans and Keke Palmer and performances of Josh Groban and Herbie Hancock's "The Star-Spangled Banner" and the Philadelphia Orchestra's "America the Beautiful" and cellist Yo-Yo Ma were also planned as part of the program.
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