Pistonless Dual Chamber Rocket Fuel Pump

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Pistonless Dual Chamber Rocket Fuel Pump

• Steve Harrington, Ph.D.
• 7-21-03

Joint Propulsion Conference
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LOX/Jet-A Pressure Fed Experiments
Whats Next? More Altitude!
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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.

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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

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First Generation Design

1. Drain the main tank at low pressure into a small
   pump chamber.
2. Pressurize the pump chamber and feed to the
   engine.
3. Run two in parallel, venting and filling one
   faster than the other is emptied

More info at www. rocketfuelpump.com
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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)

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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.

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Affordable and Reliable Dual Pistonless Pump

• 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

Pump prototype 4 MPa, 1.2 kg/sec, 7 kg (600
psi,20 GPM
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Expensive and Difficult to Design and Build
Turbopumps

• Failure mode Explosion
• Complex system
• Fluid Dynamics of rotor/stator
• Bearings
• Seals
• Cavitation
• Heat transfer
• Thermal shock
• Rotor dynamics
• Startup Shut down

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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.

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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
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Pump Static Test Results
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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
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Pistonless Pump Thrust to weight Ratio
Calculation

• 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/(1.561.5).43

Thrust for Ideal Expansion
Pump thrust to weight
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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

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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.

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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
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Mass Savings over Pressure Fed System
5 second cycle time and 300 KPa tank
pressure 350,600,900 psi fuel pressure
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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
  Flometrics rocket technology.
• Along with latest low cost engine designs, pump
  will make launch systems more safe, reliable and
  affordable.

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