Helium is used to pressurize tanks and help push fuel into the engines. Without proper helium flow, the rocket cannot safely fly. Because the upper stage is hard to reach at the launchpad, NASA rolled the stacked rocket back into the Vehicle Assembly Building, the sky-scraping hangar where it was originally put together.
The pre-solicitation released this week is not a request for proposals from industry—it states that a draft Request for Proposals is forthcoming. Rather, it seeks feedback from industry and interested stakeholders about an "objectives and requirements" document that outlines the goals of the Mars mission.
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