Pistonless Dual Chamber Rocket Fuel Pump Steve Harrington, Ph.D. 7-21-03 Joint Propulsion Conference
LOX/Jet-A Pressure Fed Experiments What’s Next?… More Altitude!
The Problem is how to Maximize Mass Ratio while Maintaining Safety, Reliability and Affordability • For performance, a rocket must have large, lightweight propellant tanks • Pressure fed tanks are heavy and/or expensive and safety margins cost too much in terms of performance. • Turbopumps are expensive and require a massive engineering effort. • The solution is the The Dual Pistonless Pump • Simple to design and manufacture and with performance comparable to a turbopump and complexity and reliability comparable to a pressure fed system.
Outline • Discuss basic pump design concept • Introduce latest pump innovations • List pump advantages over turbopump and pressure fed systems. • Present pump test results including a static fire test • Derive calculation of pump thrust to weight ratio which show that a LOX/RP-1 pump has a T/W of over 700 • Prove weight savings over pressure fed tankage of over 80%
First Generation Design: • Drain the main tank at low pressure into a small pump chamber. • Pressurize the pump chamber and feed to the engine. • Run two in parallel, venting and filling one faster than the other is emptied More info at: www. rocketfuelpump.com
Second Generation Design: • Main chamber vents and fills quickly through multiple check valves. • One main chamber and one auxiliary chamber, less weight than two chambers of equal size • Pump fits in tank, simplified plumbing • Concentric design maintains balance. • Model has been built and tested (patent pending)
Advantages • Negligible chance of catastrophic failure. • Much lighter than pressure fed system at similar cost. • One to two orders of magnitude lower engineering, testing and manufacturing cost than turbopump. • Low weight, comparable to turbopump. • Quick startup, shutdown. No fuel used during spool up. • Can be run dry. No minimum fuel requirement. • Less than 10 moving parts. Inherent reliability. • Inexpensive materials and processes. • Mass producible and scalable, allows for redundant systems.
Failure mode: Propellant dump Major components: Check Valves Level Sensors Pressure vessels These parts are available off the shelf for low cost Control System inexpensive microprocessor Affordable and Reliable: Dual Pistonless Pump Pump prototype: 4 MPa, 1.2 kg/sec, 7 kg (600 psi,20 GPM
Failure mode: Explosion Complex system: Fluid Dynamics of rotor/stator Bearings Seals Cavitation Heat transfer Thermal shock Rotor dynamics Startup & Shut down Expensive and Difficult to Design and Build: Turbopumps
Pistonless Pump Development Issues • Currently uses slightly more gas than pressure fed system. Can use less with pressurant heating. • Not invented here. • No experience base, must be static tested and flown. • Requires different system optimization than pressure fed or turbopump systems: no sample problems in the book.
Pump Performance: • Pump performance close to target of 1.5 kg/sec at 4 Mpa (20 GPM, 600 psi) • Pressure fluctuations are minimal. • Pump performs better when running on Helium • Pump needs more testing with rocket engine and to be flown to prove design. Pump running on compressed air at room temperature, pumping water at 450 psi,20 GPM
Pistonless Pump Mass Calculation: Chamber Mass Spherical Chamber Volume and Diameter Combine Equations to get Chamber Mass as a function of flow rate Chamber Thickness in terms of fuel pressure and maximum stress
Assumptions: Auxiliary pump chamber is 1/4 the size of main pump chamber Valves and ullage add 25% to mass Total pump mass is 1.252 or 1.56 times main chamber mass 1/(1.56*1.5)=.43 Pistonless Pump Thrust to weight Ratio Calculation: Thrust for Ideal Expansion Pump thrust to weight
Typical Pump Thrust/Weight Calculations Assumptions: • Rocket Chamber Pressure 4 Mpa, (600 psi) • Pump cycle time 5 seconds. • Sea level Specific Impulse from Huang and Huzel , • Pump Chambers are 2219 aluminum, 350 MPa (50ksi) design yield strength, 2.8 specific gravity
Another Calculation: Mass Savings of Pump and Tank Over Pressure Fed Tank • Mass of pressure fed tank is proportional to volume and pressure • Mass of pump fed system is the mass of a lighter low pressure tank plus the mass of the pump • Tank Mass Savings: • 200 KPa tank is 1/10 the weight of a 2 MPa tank. Pump size,weight is less than 1/10 of that of pressure fed tank. • Pump chamber pressure is the same as pressure fed tank pressure, but the volume is much less.
Pump Mass is Negligible for Long Burn Times • The volume of the pump chamber is proportional to the flow rate times the cycle time • The volume of the tank is equal to the flow rate times the burn time. • Therefore the ratio of the pump chamber mass to the tank mass is equal to the ratio of the cycle time to the burn time if we put in a factor of 1.56 to account for the auxiliary chamber, valves etc. Pump volume ratio Tank pressure ratio
Mass Savings over Pressure Fed System 5 second cycle time and 300 KPa tank pressure 350,600,900 psi fuel pressure
Conclusions/ Future Plans • Pump weight and cost are low and it works as designed. • Next steps: • Static test and fly pump in student rocket with Flometric’s rocket technology. • Along with latest low cost engine designs, pump will make launch systems more safe, reliable and affordable. NASA Fastrac Beal BA 810 TRW Low Cost Pintle Engine Microcosm Scorpius