1. Schematics and Valves Reference info

2. Fundamentals -- Monoprop Blowdown System

3. Fundamentals -- Regulated Monoprop System

4. Typical Prop System Safety Features (CONTOUR)

5. Add a Valve Usually solenoid valves (sometimes torque motor valves may be used) Most often series dual seat Seats may be metal or elastomer May be sliding fit or S-spring type Ti is available, but CRES (corrosion resistant steel) is most common Most valves have small integral inlet filters Consume 10 to 45 watts continuously when open Valve to thruster seal is usually a qualified O- ring face or gland seal Trapped volume from valve seat to thruster inlet is the “dribble volume” that exhausts after valve is closed

6. Typical Solenoid Valve Cross-Section

7. Valve Sources http://www.moog.com/Space/SpacecraftFluid/ http://www.valvetech.net/products.html http://www.vacco.com/space2.html

8. Add Propellant Lines Propellant lines may be CRES or Ti. Bipropellant systems are usually Ti because oxidizer leaches iron out of CRES. Standard seamless tubing in several wall thicknesses is available Fittings are rarely used, most systems are welded with orbital arc welding I design layouts clearance must be left for weld head Tubing diameter is sized to minimize system pressure drop quarter-inch and 3/8 inch are common outer diameters In a system layout, provisions must be made to support tubing

9. Group an Isolated Manifold Thrusters may be chosen for a manifold group by function, for redundancy or by location Isolation valves are often latch valves, but can also be pyro valves Valve material usually is selected to be the same as tubing material Pyro valves generate particulates and must have downstream filters Latch valves usually have integral inlet filters Latch valves are $$$$ Manifolds generate coupled pressure effects

10. Latch Valve Cross Section

11. Typical Pyrovalve

12. Isolation Valve Sources http://www.moog.com/Space/SpacecraftFluid/ http://www.vacco.com/space2.html http:www.conaxfl.com

13. Add Service Connections Service valves allow filling the propellant tank, evacuating and bleeding-in the system and adding pressurant Usually simple, light-weight, quarter-turn shut off valves to connect to fueling system Usually are flown with caps in place Service inlets in system may be gravity determined low points or highpoints Service valves are usually on the outside of the vehicle

15. STEREO Schematic MR-111C 1.0 lbf Rocket Engine Assemblies P L S Filter Service Valve Latching Valve Solenoid Valve Pressure Transducer KEY Orifice Cryo Joint

16. Add a Pressurization System Pressurant tank (He or N2) is usually very high pressure (3000 to 5000 psia) Often a composite over-wrapped tank is used Regulators are $$$$$ Regulators are sensitive to contamination Regulators are often less reliable than other components Check valves are usually employed on the pressurization inlet as well as the propellant outlet of the tank for the same reason O>O> O>O> O>O> O>O>