Table 1 provides the results of that collaboration. This single sheet of requirements formed the basic  specification for the valve design effort. This also became the list used in the selection of trade study  Figures of Merit (FOM) and weighting factors. Table 1. Valve Performance Requirements Hermetically Sealed Isolation Valve Performance Requirements Requirement General Detail Requirement Goals MediaInert Gas, Solvent, Propellant  CompatibilityWetted surface non-reactive with helium, nitrogen, argon, IPA,  hydrazine. MMH, NTO, kerosene, dimethylhydrazine, etc. Internal LeakageShall provide a leak-tight seal until actuatedInternal and external leak rate < 10-6sccs - Parent metal seal  is fractured during actuation. Pressure RatingMaximum Design Pressure and ability to be actuated over a range of pressuresMinimum operating pressure shall be 350 psig (2,400 kPa);  design shall be shown as extensible to up to 4500 psig (31,000  kPa). Actuation Time Low Response Time Response in less than 50 msec.  RepeatabilityActuations repeatable within a  narrow rangeRepeatable to within 10 msec. Actuator Force  MarginForce available from the  actuator should be significantly greater than required to  operate the valve All external inputs (e.g., heat, elec trical interference, vibrations,  or other external stimuli) must not cause the valve to actuate prematurely and actuator shall provide a required 100%  margin to these loads. APT and In Situ  TestingAbility to actuate individual  valve during testing without loss of sealThe valves shall withstand testing pressurized or  depressurized without loss of the hermetic seal. This will ensure individual valve functionality, which will significantly  mitigate mission risks and decrease overall unit cost. Particulate  generation Particulate generation shall be  minimizedParticulate can clog filters and plug components downstream;  must be minimized both in number and size. Largest passable  particulate is 0.5 micron. Construction and  End fittingsAll-welded fluid flow path This is a basic requirement of in-space propulsion system  components to limit the possible propellant leak paths.Mechanical fitting-type or O-ring seals cannot be used as  primary seals. Proposed valve uses a parent metal seal, which  is fractured during actuation, maintaining all welded fluid path. Development valves can be bolted, but must show path to all  welded design. Flow Rate and  DP PerformanceLow pressure drop/ High Flow  Coefficient/g507/g51/g3/g31/g3/g22/g3/g83/g86/g76/g68/g3(20kPa) @ 0.15 kg/s – from pyrovalve spec from  SDO. – typical of in-space propulsion systems InterfacesGeneral interface  requirements, valve designs shall be show extensibility to larger and smaller  requirements.¼” to ½”” inlet/outlet tube fittings.  Electrical connector or leads.  Mechanical mounting feet to allow for integration to spacecraft structure. Electrical  RequirementsTypical of in-space propulsion system electric limits.Power < 60 W, Voltage < 28 V, E < 1 Wh, Current > 2 amps.  Mass  Mass should be comparable to  existing pyrovalves.Mass should be less than 2.5 lbm (1.1kg).  ConstructionTo the extent possible, SLM  shall be used for this valveUsing SLM offers the opportunity to design new and complex  geometries to meet the performance requirements. Designs  that utilize SLM are required.    474