After scrubbing a launch attempt of the Space Launch System rocket on Monday, NASA officials said they are working on a second attempt to fly the Artemis I mission on Saturday, Sept. 3.
NASA flight leaders halted the first launch attempt after failing to verify that one of the SLS rocket’s four main engines — engine No. 3 – Properly cooled to a temperature of -420 degrees Fahrenheit prior to ignition. The engines must be cooled to very low temperatures to cope with the injection of very cold liquid hydrogen and oxygen propellants.
Speaking at a press conference on Tuesday evening, NASA’s program manager for the SLS rocket, John Honeycutt, said his engineering team believed the engine had actually cooled from ambient temperature to near the required level, but had not been properly measured due to a faulty temperature sensor.
“The way the sensor behaves doesn’t match the physics of the situation,” Honeycutt said.
The problem for NASA is that the sensor cannot be easily replaced and would most likely have to be returned to the Vehicle Assembly Building at the Kennedy Space Center in Florida, a few miles from the launch pad. This would delay the launch of the rocket until at least October, and the space agency is beginning to worry about wear and tear on a rocket that has now been in the pipeline for nearly a full year.
Honeycutt said he is confident there was liquid hydrogen in engine No. 3 during Monday’s countdown and that other sensors, including pressure readings, indicated the engine was in an environment that would have cooled it properly. Therefore, he said, his team is working on a “flight plan” that would allow the rocket to launch without getting good data from the engine’s temperature sensor.
“We’ll look at all the other data we have and [will] use it to make an informed decision,” he said.
Accordingly, NASA’s current plan includes some work on the launch pad today, including the inspection of an area where there was a minor hydrogen leak during Monday’s countdown. If officials are satisfied with those inspections and their escape grounds for dealing with the faulty temperature sensor, the agency will begin a countdown on Thursday. On this timeline, tank operations would begin on Saturday morning, before the opening of a two-hour launch window at 2:17 p.m. ET (18:17 UTC). To give the launch team more time to work on the engine cooling issue, the process known as “conditioning” the engines would begin earlier in the countdown than Monday.
At Tuesday’s press conference, it was not immediately clear what the consequences would be of a launch with a hotter-than-normal main engine. From a physics standpoint, igniting super-cooled propellants in a hotter-than-expected engine would at least seriously damage the RS-25 engine’s turbo pump. Presumably, therefore, NASA would not launch the SLS rocket without much confidence in its flight reasons.
NASA has until September 5 to launch the booster before it has to be taken off the pad for renovation. As the September 3 launch date approaches, the space agency will closely monitor the weather forecast and fix technical issues. While thunderstorms often develop along the Florida coast during summer afternoons, Launch Weather Officer Mike Burger said onshore currents should be fairly strong this weekend. That should push the sea breeze further inland and potentially provide some opportunities to launch during the two-hour window. If weather hinders the attempt, NASA will make arrangements to attempt a September 5 launch.
Officials insisted during Tuesday’s press conference that they had confidence in a launch attempt. Although the space agency heavily promoted the first Artemis I launch attempt on Monday — the launch of an unmanned Orion spacecraft to the moon was celebrated with celebrity appearances, social media promotion and a visit by Vice President Kamala Harris to the Florida spaceport. – NASA has yet to complete a tank test of the vehicle.
Despite this, the space agency hopes it can fully fuel the rocket on Saturday and count down to T-0 without further problems.