After exhaustively analyzing the data from its first attempt to launch the Artemis I unmanned lunar mission, NASA rescheduled the launch for this Saturday (3), starting at 15:17 (GMT). O Sidereal Messenger broadcasts live, starting at 3 pm, and the flight window will last for two hours.
Some problems marked the original effort, last Monday (29), which ended up interrupted with the timer stopped at T-40 minutes for the launch. During the refueling of the giant SLS rocket, small leaks of liquid hydrogen, fuel used by the two stages of the rocket, were detected, but nothing that impacted safety, the availability of propellant or the complete fueling of the vehicle.
What actually interrupted the count was a difficulty in cooling one of the engines of the first stage. To handle the ultracooled propellants, these four RS-25 engines (the same ones used on the space shuttle) need to be cooled down to -251°C before ignition. The cooling procedure is carried out by flowing liquid hydrogen through the engine, which technicians call bleeding.
During this activity, on the countdown, engineering sensors installed to monitor this indicated that Engine 3 was not cooling properly. (In fact, the agency later revealed that the four sensors indicated temperatures above the expected, but in three of the engines, very close to ideal; only in engine 3 the temperature indication was too high.) After carrying out procedures to try to solve the case (which even involved shutting off the bleed on engines 1, 2 and 4, letting only hydrogen flow into engine 3), the American space agency decided to play it safe and postpone the launch.
Since then, teams have worked day and night to understand what was happening. Small adjustments were also made on platform 39B at the Kennedy Space Center in Florida to prevent subtle leaks detected on the first attempt. And the conclusion that NASA has come to is that the engineering sensors that were giving a false reading, and the engines were in fact cooled to the ideal temperature. During a press conference held on Thursday (1st), the American space agency showed great confidence in this, based on other sensor data and a detailed analysis of the physical process involved in the cooling of the engines – which, moreover, are very well characterized. , after three decades of experience with them during the space shuttle program (1981-2011).
Of course, solving these initial snags is no guarantee of success for Saturday. Other technical issues may appear in the resumption of the countdown, as well as difficulties with the weather. But the weather forecast suggests good conditions for the effort. The estimate by Space Force meteorologists is that the window opens at 3:17 pm with a 60% chance of a green light for launch. As the window advances, which closes at 5:17 pm, the probability rises to 80%.
With the change of date, however, there are changes in the profile of the lunar mission, which will take an unmanned capsule (but with two dummies) to a distant lunar retrograde orbit (which will make the Orion launched on the Artemis I mission the vehicle destined to transport humans. which has flown the furthest to date, reaching nearly half a million kilometers from Earth). Originally planned to last 42 days if the launch had taken place on Monday, it is now expected to last 37 days if it departs on Saturday. At the end, Orion will make a landing in the Pacific Ocean, aided by parachutes.
If all goes well, NASA hopes to launch a similar rocket and capsule again in 2024, this time transporting the first humans to the vicinity of the Moon since the Apollo 17 mission, carried out by the same space agency in December 1972.
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