AbstractDuring each mission, the Delta IV launch vehicle (LV) is subjected to a rigorous flight readiness review process to ensure mission success. This process was derived from the flight-proven Delta II launch readiness review process. This disciplined process integrates functions from quality assurance, manufacturing, launch site processing, and engineering.The process consists of a series of reviews scheduled to validate and establish with a high degree of confidence that the LV and ground support equipment will perform reliably and meet mission objectives. Reviews are linked to key Delta IV launch milestones. The process progresses from production through post-launch data reviews and includes customers and independent assessment teams.During the flight readiness review process of a recent Delta IV mission, an independent review team from Analex Corporation presented results of simulations of the behavior of the second-stage cryogenic propellants. These results differed considerably from those Boeing and the Aerospace Corporation were showing at the time. Boeing then recommended that the launch team stand down until the discrepancy between analysis results was resolved.A team consisting of representatives from Boeing, the Air Force, the Aerospace Corporation, Flow Sciences, and Analex investigated this slosh behavior. During the investigation, it was concluded that the slosh behavior of the liquid hydrogen (LH2), during the second stage coast phase of flight, would not be constrained to the aft end of the tank and thus presented an increased mission risk. The presence of propellant in the tank forward dome at tank venting could lead to propellant ingestion into the vent/relief system and result in a thrust imbalance.This paper focuses on the team's investigative efforts and resolution of the issues associated with the sloshing, including the implementation of a pulse-settling approach for propellant management. Fig. 1 is a screen-shot from a simulation of the LH2 sloshing in the second-stage tank during a coast period.
The Boeing Delta IV launch vehicle—Pulse-settling approach for second-stage hydrogen propellant management
Acta Astronautica ; 61 , 1-6 ; 416-424
2007-01-01
9 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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