Propulsion CEV

Propulsion Overview: 

Propulsion Overview Charles Vaughan AA420 Space Systems Design

Propulsion Mission Requirements: 

Propulsion Mission Requirements Propulsion Mission OptionsAttitude Control Propulsion - This is an important subsystem that we will come back to. For now, provide a mass budget, understand that it may interact with primary propulsion. You may choose to assume that the kick into interplanetary transfer trajectory comes from the launch vehicle or from spacecraft primary propulsion. Impulse requirements must be calculated (+/- 10%) by the Orbits Team Volume of the propellant tanks needs to be calculated (add 10% for ullage) Mid-course correction propulsion Lander propulsion (for scenario 3) Payload Team to define this system. Generally speaking high efficiency means low thrust

Propulsion Mission Options: 

Propulsion Mission Options Solid Rocket Motors - extensive flight history About 270 to 290 sec Isp Range from 0.90 to 0.95 Mass Fraction High Thrust, Single use, High heat flux http://www.astronautix.com/spaceflt.htm Cryogenic Bi-Propellant Thrusters - limited flight history About 460 sec Isp Range from 0.6 to 0.8 Mass Fraction H2 is not storable for more that 24 hours without significant thermal control hardware, H2 has very low density (about 4.4 lbm/ft3), O2 (sp. Gr. 1.14) Multiple Restarts possible but more limited than storable

Typical Solid Door-knob Motor: 

Typical Solid Door-knob Motor Thiokol STAR-37FM Gross Mass: 1,147 kg. Empty Mass: 81 kg. . Thrust(vac): 47.90 kN. Isp: 290 sec. Burn time: 63 sec. Diameter: 0.9 m. Length: 1.7 m. Status: In Production. Flown: 6. Propellant: 1067 kg of AP/HTPB/Al in 6Al-4V titanium case. The motor has been qualified for propellant offloading to 1,023 kg. Propellant mass fraction 0.929.

Pratt & Whitney RL-10: 

Pratt & Whitney RL-10 Characteristics Thrust: 20,800 -24,750 pounds Weight: 370 - 646 pounds Fuel: Liquid hydrogen/liquid oxygen Mixture Ratio: 5-to-1 to 6-to-1 Specific Impulse: 444.4 - 465.5 sec

Propulsion Mission Options (cont.): 

Propulsion Mission Options (cont.) Storable Bi-Propellant Thrusters - extensive flight history About 325 sec Isp Range from 0.80 to 0.90 Mass Fraction Thrust range from 10 N to 1000 N readily available Multiple restarts Monomethyl hydrazine (sp. gr. 0.88) or Hydrazine as fuel MON-3 (sp. gr. 1.45), N2O4 blend as oxidizer, leaches iron over time Mono-Propellant Thrusters - extensive flight history About 230 sec Isp steady state Range from 0.85 to 0.95 Mass Fraction Thrust range from 0.5 N to 400 N readily available Multiple restarts Hydrazine as fuel, (sp. gr. 1), Ir coated ceramic catalyst

Bipropellant Rocket Technology: 

Bipropellant Rocket Technology Red=Hot Gaseous Combustion Product OXIDIZER (N2O4) Optional Boundary Layer Film Cooling (FUEL) FUEL INLET Typical Performance: 280-325 lbf-sec/lbm Key Technologies: High temperature coatings/materials Combustion optimization/injector design Thermal design Typical fuel is Mono-Methyl Hydrazine (MMH) or Hydrazine (N2H4) Yellow=Cooler Gaseous Combustion Products

Bipropellant Engines: 

Bipropellant Engines

Hydrazine (N2H4) Rocket Technology: 

Hydrazine (N2H4) Rocket Technology Blue=Liquid N2H4 Red=Hot Gaseous N2, H2, NH3 Typical Performance: 220-235 lbf-sec/lbm Key Technologies: Catalyst bed design Injector design Thermal management

Monopropellant Hydrazine Rocket Engine Assemblies (REA’s): 

Monopropellant Hydrazine Rocket Engine Assemblies (REA’s) MR-103G 0.2 lbf REA MR-107B 30 lbf REA MR-106E 5.0 lbf REA MR-111C 1.0 lbf REA MR-104B 100 lbf REA MR-80 600 lbf REA

Propulsion Mission Options (cont.): 

Propulsion Mission Options (cont.) Electrothermal Thrusters - extensive flight history About 300 sec Isp for Resistojets, 600 sec Isp for Arcjets Range from 0.85 to 0.95 Mass Fraction, usually part of a hydrazine ACS system Thrust about 0.25 N Multiple restarts Hydrazine as fuel, Ir coated ceramic catalyst 500 - 750 W power for Resistojets, 1.8 to 2.0 kW power for Arcjets Hall Thrusters - limited flight history About 2000 sec Isp Range from 0.80 to 0.90 Mass Fraction Thrust range from 0.025 N to 0.050 N Multiple restarts Xenon as fuel, use specific gravity of 3.5 (highly variable) 1.5 to 4.5 kW power

Electric Propulsion: 

Electric Propulsion Electrothermal Hydrazine Thruster Hydrazine Arcjets and Power Processing Unit High Power Ammonia Arcjet and Feed System Xenon Ion Engine Hall Thrusters Pulsed Plasma Thruster

Propulsion Mission Options (concl.): 

Propulsion Mission Options (concl.) Ion Thrusters - limited flight history DS-1 30 cm ion thruster may be the only currently qualified Range from 0.80 to 0.90 Mass Fraction Multiple restarts Xenon as fuel 2 kW power NSTAR Engine: 30 centimeters grid diameter 8 kg (thruster only) 3100 seconds Isp 20 to 92 mN of thrust

DS-1 Ion Propulsion System: 

DS-1 Ion Propulsion System

Goals for 420 Phase I: 

Goals for 420 Phase I Calculate required impulse for different scenarios with a fixed mass Trade different options and select propulsion technology (-ies) Calculate the system mass, iterate impulse if necessary Calculate the system volume State assumptions and ground rules

Building a System: 

Building a System Thruster: see Propulsion I lecture

Thruster Sources: 

Thruster Sources http://www.atlanticresearchcorp.com/docs/space.shtml http://www.rocket.com http://www.boeing.com/space/rdyne/flash.html http://www.pratt-whitney.com/ http://www.aerojet.com/

Add a Valve: 

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 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

Typical Solenoid Valve Cross-Section: 

Typical Solenoid Valve Cross-Section

Valve Sources: 

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

Add Propellant Lines: 

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

Group an Isolated Manifold: 

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

Latch Valve Cross Section: 

Latch Valve Cross Section

Typical Pyrovalve: 

Typical Pyrovalve

Isolation Valve Sources: 

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

Add a Propellant Tankwith isolation and filtration: 

Add a Propellant Tank with isolation and filtration Propellant Tanks may be either Ti or CRES, Ti is common Most propellant tanks have bladders, diaphragms, or surface tension propellant management devices Tanks are $$$$$ and long lead items (18 months and $100k to $2M are not uncommon) Outlet isolation valves are often pyro valves, sometimes latch valves Filters are often pressed sintered screen or wire Tanks can be difficult to clean Tanks require proof pressure verification and sometimes hydro-burst

Propellant Tank Sources: 

Propellant Tank Sources http://www.psi-pci.com/psi/Products.htm http://www.ardeinc.com/liquid.html

Add Service Connections: 

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

STEREO Schematic: 

STEREO Schematic MR-111C 1.0 lbf Rocket Engine Assemblies

Add a High Thrust Biprop Engine: 

Add a High Thrust Biprop Engine Check valves are added to reduce the opportunity for inadvertent propellant mixing Oxidizer often leaches iron so Ti is used for Ox system Valves on the thruster are similar solenoid or latching valves to monoprop thrusters ACS thrusters may also be biprop

Add a Pressurization System: 

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

Issues for Propulsion Systems: 

Issues for Propulsion Systems Loaded Propellant tanks are heavy and require substantial structural support As propellant tanks empty, Cg moves Propellant contacting surfaces must be assembled from clean parts in a clean room. All welded construction is most common. Valve events can propagate pressure waves. Such “water hammer” can have very high peaks Flow in one part of the system can decrease pressure in another part Systems are natural bubble traps Systems are natural dirt traps

Steps in Propulsion System Design: 

Steps in Propulsion System Design Select the propulsion type and define the system architecture Develop a system operational plan to support the mission Select components Calculate the system mass, power, volume Support system design detail development Tubing runs Cabling Support system analysis Plume impingement Power analysis Water Hammer analysis Thermal and Structural analysis