when fired open the valve 110 so that fluid such as the pressurized gaseous helium from the fluid supply system 192 e g helium source may flow from through the valve 110 into the ullage bottle 186 in this regard the valve 110 also includes at least a first wall or partition 146 which includes first and second sections 146 a 146 b again principally for redundancy between the first and second cavities 142 144 which breaks separates or otherwise ruptures upon firing of the triggers or initiators 172 a 172 b to open the valve 110 i e to remove the isolation between the first chamber 142 and the second chamber 144 for launch vehicle and spacecraft applications such initiation or firing typically occurs after the launch vehicle has separated from the spacecraft and associated upper stage the reaction control system 100 illustrated in fig5 6 being associated with such upper stage for purposes of allowing servicing of the pneumatic portion of the system 100 prior to launching of such a spacecraft e g on the launch pad the valve 110 includes a service port 160 which is associated with the second chamber 144 and which is used to pressurize and or depressurize the ullage bottle 186 a service port 150 of the valve 110 is associated with the first chamber 142 and is not.