NASA has now made two tries at getting the Artemis I mission off of the ground — the first on August 29 and the second on September 3. The initial launch attempt was scrubbed after it appeared one of the rocket’s four main engines was too hot during engine bleed tests. This issue, however, was later traced to a misleading reading from a “bad sensor”. A persistent leak in the hydrogen fuel line, meanwhile, brought the second go to a halt, despite engineers trying three times to troubleshoot the problem.
To try and ensure the next Artemis launch attempt goes ahead without a hitch, NASA is conducting a “cryogenic demonstration test” this Wednesday.
This procedure will allow them to check that they can indeed successfully fuel the core and interim stage of the 322-foot-tall SLS rocket with a full super-cooled propellant load of more than 730,000 gallons of liquid hydrogen and oxygen — a feat the space agency managed in neither previous launch attempt.
Tom Whitmeyer, NASA deputy associate administrator for Common Exploration Systems Development, said that, this time, they will be doing a “kinder, gentler kind of loading operation”.
He told the Orlando Sentinel: “We’re going to lower the pressure a little bit at the beginning of the chill-down procedures, up through the transition to fast fill, and we think that will really help with the pressure and temperature transitions in the system.”
Alongside checking the so-called “tanking” process can be completed smoothly, the demo will also allow NASA engineers to revisit the issue which occurred around the kick-start bleed test during the first launch.
This test involves using some of the liquid hydrogen fuel to cool down the four RS-25 engines at the base of the rocket’s core stage to a nippy 423F (217C).
The purpose of this is to ensure that the engines are not unduly stressed when the supercool fuel is channelled into them properly at the time of launch.
The cryogenic demonstration is scheduled to begin at 7.15am ET (12.15pm BST) and run for just under eight hours.
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A potential further complication comes as a result of the “flight termination system” (FTS) — which allows NASA to safely self-destruct the rocket in the event of a serious problem after lift-off.
NASA’s current agreement with the Eastern Range (through whose airspace the rocket will be flying) calls for the batteries on the FTS to be checked after 25 days on the launch pad.
Such checks require that the rocket be rolled back to the Vehicle Assembly Building — however, NASA is seeking a waiver to allow the SLS to stay in launch position.
Artemis mission manager Mike Sarafin told the Orlando Sentinel: “All of the dates that we talked about are for planning purposes. We have to plan ahead.
“We have to have a marker that we’ve asked the team to work for, for a whole host of reasons, and those dates that I provided are all pending—and pending the decision from the Range.
“That said, we are internally marching ahead.”