Project Overview

In my first year at the Columbia Space Initiative, I worked to develop a passively activated nitrogen quick disconnect (QD) system for our launch vehicle, which resulted in a successful launch. This year, I am grateful to have been given an increased responsibility as the responsible engineer for an even more complex and performance increasing part, a cryogenic liquid oxygen (LOX) QD system. 

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While the nitrogen disconnect was necessary to allow abort, a LOX QD was not strictly needed due to dedicated abort valves. However, the lack of a LOX QD made the team’s life difficult in several ways. For one, it made our fill procedure much more clunky. To prepare for engine fire, the team first had to fill completely with LOX while keeping members at the pad wearing specialized cryogenic gear to disconnect the line when full. These team members would then have to store the line and the LOX dewar, before quickly retreating to a safe area before GN2 fill could begin. Not only was this a clunky system which added time and effort to our launch and test operations, this also allowed heavy amounts of boil off. Because LOX exists at cryogenic temperatures, once out of the dewar, much of the LOX would begin to immediately boil off in the tank through a vent valve. Calculations found that during a 17 minute period in which the COPV was filled, about 16 pounds of LOX would boil off. Our LOX tank last year was designed to hold 35 pounds of LOX, representing a 46% loss of oxidizer under nominal conditions. That loss of performance would be magnified due to an increase in ullage volume caused by the boil off, giving the nitrogen more space to expand into and decreasing the time spent at maximum operating pressure. This amount of performance loss was deemed unacceptable by the team, thus, development of a cryogenic, liquid oxygen quick-disconnect was considered necessary. Filling the tank through a QD would enable team members to retreat immediately during filling procedures, and would enable top-off of LOX to the vehicle during nitrogen fill, drastically reducing the effects of boil off, and decreasing the ullage volume in the tank.