Tomorrow morning’s launch attempt was originally meant to go ahead last Monday, until the space agency decided to hold off to allow more time to recover after Hurricane Nicole made landfall on the Florida coast late on November 9.
This delay was relatively minor compared to the one brought about by Hurricane Ian at the end of September, when NASA was forced to withdraw the SLS back from the launch pad to its assembly building to shelter from sustained wind speeds of up to 150 miles per hour.
The towering rocket is rated to withstand winds gusting up to 85 miles per hour — and with Nicole nowhere near as powerful as her predecessor, the space agency made the call to leave the rocket on the launch pad during the recent stormy weather.
However, NASA explained, giving the launch window on November 14 a miss was necessary to allow employees time to both attend to their families and homes around time of the hurricane, and perform inspections of the rocket before any blast-off attempt.
Prior to the recent run of disruptive weather, NASA had already made two attempts at getting the SLS to lift-off — the first on August 29 and the second on September 3.
The initial launch attempt was scrubbed after it appeared that 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 liquid hydrogen fuel line, meanwhile, brought the second go to a halt, despite engineers trying three times to troubleshoot the problem.
Both of these issues were reexamined in mid-September when NASA undertook a “cryogenic demonstration test”, which saw a practice tanking of the SLS’s core and interim stages with more than 730.000 gallons of liquid hydrogen fuel.
The space agency reported that “after encountering a hydrogen leak early in the loading process, engineers were able to troubleshoot the issue and proceed with the planned activities.”
These activities included revisiting the kick-start bleed test — in which a small amount of liquid hydrogen fuel is used to cool down the four RS-25 engines at the base of the rocket’s core stage to 423F (217C) — that threw up problems during the first launch attempt.
The purpose of this was to ensure that the engines are not unduly stressed when the supercool fuel is channelled into them properly at the time of launch.
Following the cryogenic demonstration test, NASA reported “all objectives [were] met” — leading to optimism that the SLS will be able to successfully lift-off in this latest attempt.