Pistonless Dual Chamber Rocket Fuel Pump

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Pistonless Dual Chamber Rocket Fuel Pump

• Steve Harrington, Ph.D.
• 5-22-03

California Space Institute
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LOX/Jet-A Pressure Fed Design Working Well
Whats Next? More Altitude!
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The Problem is Mass Ratio How to Make a
Lightweight, Inexpensive Rocket with a Large Fuel
Capacity.

• 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 require massive engineering effort and
  are expensive.
• The solution is the The Dual Pistonless Pump
• Simple to design and manufacture and with
  performance comparable to a turbopump and
  complexity 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
• Derive calculation of pump thrust to weight ratio
  which show that a LOX/RP-1 pump has a T/W of over
  700

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First Generation Design

• Drain the main tank at low pressure into a small
  chamber.
• Pressurize the small 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
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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

• Much lighter than pressure fed system at similar
  cost.
• At one to two orders of magnitude lower
  engineering 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.
• Negligible chance of catastrophic failure.
• Scalable, allows for redundant systems.

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Engineering Cost Dual Pistonless Pump

• Check Valves
• Level Sensors
• Pressure vessels
• These parts are available off the shelf
• Control System (microprocessor or logic circuit)

Pump model made from industrial/consumer parts 4
MPa, 1.2 kg/sec, 7 kg
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Engineering cost Turbopumps

• Fluid Dynamics of rotor/stator
• Bearings
• Seals
• Cavitation
• Heat transfer
• Thermal shock
• Rotor dynamics
• Startup
• Shut down

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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
• Pressure spikes have been reduced.
• Pump chamber vents and pressurizes more quickly
  when running on Helium
• Pump needs to be tested with engine and flown to
  prove design.

Pump running on compressed air at room
temperature, pumping water.
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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 chamber is 1/4 the size of main chamber
• Valves and ullage add 25 to mass
• Total pump mass is 1.252 or1.56 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
• Pump cycle time 5 seconds.
• Sea level Specific Impulse from Huang and Huzel ,
  
• Pump Chambers are 2219 aluminum, 350 MPa 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 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
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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.
• Combine with low cost ablative engines and low
  cost vehicles for low cost access to space.

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