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Transcript of Strategies for 3D Printing Advanced Hybrid Rocket Fuel Grains and Hybrid-Like Liquid Rocket...
© 2016 The Aerospace Corporation
Strategies for 3D Printing Advanced Hybrid Rocket Fuel
Grains and Hybrid-Like Liquid Rocket Motors
Jerry Fuller,
Space Science Applications Laboratory
The Aerospace Corporation
October 19, 2016
2
Basics: Major Rocket Propulsion Systems
(A) Liquid - most capable, expensive – Saturn 5, Shuttle Main Engine
(B) Solid - cheap and simple, most common – Tactical missiles,
Shuttle SRM Boosters
(C) Hybrid - safe, moderate expense, low performance (thrust,
efficiency), rarely used (Virgin Galactic - SpaceShip 1, 2)
Rockets are categorized by the phase states of their propellants.
These states have a great deal to do with how a rocket is used.
Oxidizer/
Fuel
Mixture
(Solid)
Oxidizer
(Liquid)
Fuel
(Solid)
Valve
Oxidizer
Fuel
Turbo-
pumps
(A) (B) (C)
3
Hybrid Rocket Characteristics
Typical Selling Points for Hybrid Rockets
Advocates Like to say Hybrids:
Have Medium Performance (ideally near liquids)
Are Easily Shipped - “Responsive”
Can be throttled, re-lit like liquids
Simple, safe and inexpensive
The truth is…
We can’t burn them fast enough (low thrust)
They are not as efficient as they should be
Oxidizer
Valve
Fuel
4
Fuel Grain Production – The Fundamental Problem
A Simplified Explanation of Casting
• Real castings often involve multiple ports, and stiffening webs
• Mandrels must be simple shapes
– No undercuts
– Little surface area
Mold or
Liner
Mandrel
Propellant
Grain
Port
5
How We Generally Think of Hybrid Rocket Combustion
Similar illustrations appear throughout hybrid rocket literature
• Generally we assume gas flow parallel to the fuel surface
• We accept that convection will be weak
• Burn rate is limited by how fast gases can diffuse across the Flame
Pyrolysis by Radiation and Weak Convection
Fuel Grain (often HTPB Rubber)
FlameSheetHead
End
Radiation (weak)
“Blowing” Conduction (weak)
Oxidizer Nozzle
End
6
Traditional Techniques to Improve Performance
The techniques used to improve performance have problems too
Wagon Wheel
Low mass fraction
Challenging Fabrication
Chunks and splinters
Swirl Injection
Effect dies out
Slicing and Stacking
Complex
Chunks
Paraffin (wax) as High Regression Rate fuel
Mechanically weak
Ejects unburned fuel (lowering Isp)
Patent US5339625 A
Patent US6601380 B2
8
Traditional versus Additive Manufactured Grain
Printing allows port shapes that dramatically increase performance
MJM Acrylic Fuel Grains
• Same
– Mass
– Dimensions
– Cross Section
• Helical shape forces
convection
• Creates 25% more
surface area
• More efficient
• Burns > Twice as Fast
AM fuel grains move from Radiation to Forced Convection
9
Printing Strategies
Several Ways to Take Advantage of AM
• Print the whole fuel grain
– Seamless, monolithic, strong
– ABS is as good as traditional HTPB, but…
• Friendlier Chemistry
– Stronger, Stiffer, Greener
– Recyclable scrap
• Print just the port, or port and shell
– Cast paraffin, HTPB or other fuels
– Use printed structures to manipulate oxidizer flow
• Turbulence – inducing features
• Swirl - inducing features
Printed ABS
Printed Paraffin
Printed
Turbulator/
Cast Paraffin
10
Printing Strategies (cont’d)
Several Ways to Take Advantage of AM
• Print multiple fuels at once
– MJM Acrylic/Paraffin
– FFF Multi-Head extruders and Mixing Extruders
• Print empty cells and fill with a solid or liquid fuel
– Extremely high regression rates are possible
– Very powerful fuels can be used
• Print empty containers and fill with cast composite
solid propellant
– Propellants like APCP can be cast as traditional
– May offer new grain shape opportunities to combine thrust
and efficiency
MJM Co-Printed
Acrylic/Paraffin
Printed Cell Structure
for Liquids
11
Printing Strategies (cont’d)
Several Ways to Take Advantage of AM
• Print hollow fuel grain
• Use cast propellants
– Less expensive (currently)
– Print flow management features
• Swirl, turbulence…
– Include oxidizers to make new APCP motors
• ABS extrusion temperature too hot for Ammonium
Perchlorate
• May be able to have higher thrust, longer burn
Printed ABS/
Cast Paraffin
12
Performance Characterization of Hybrid Rocket Fuel Grains with Complex Port Geometries Fabricated Using Rapid Prototyping Technology
D. Armold, E. Boyer, B. McKnight, J. D. DeSain, J. K. Fuller, K. K. Kuo, and T. Curtiss
International Journal of Energetic Materials and Chemical Propulsion, Vol.13, 2014
0.1
1.0
40 50 60 70 80 90 100
Acrylic Correlation
Straight-Port
ST-SW 1/8 tpi
ST-SW 1/4 tpi
ST-SW 1/2 tpi
Reg
ress
ion
Rate
(m
m/s
)
Oxidizer Mass Flux (kg/m2-s)
150
Hot-Fire Test Results – Acrylic MJM
Increased regression rate through printed features
13
Performance Characterization of Hybrid Rocket Fuel Grains with Complex Port Geometries Fabricated Using Rapid Prototyping Technology
D. Armold, E. Boyer, B. McKnight, J. D. DeSain, J. K. Fuller, K. K. Kuo, and T. Curtiss
International Journal of Energetic Materials and Chemical Propulsion, Vol.13, 2014
0.9
1.0
2.0
3.0
50 60 70 80 90 100
Paraffin CorrelationSPTRB 1/2 tpiST-SW 1/8tpi
ST-SW 1/4 tpiST-SW 1/2 tpiSwept HC 1/4 tpiLg Swept HC 1/4 tpi
Reg
ress
ion
Rate
(m
m/s
)
Oxidizer Mass Flux (kg/m2-s)
150
Hot-Fire Test Results – Paraffin MJM
Increased regression rate through printed features
14
Performance Characterization of Hybrid Rocket Fuel Grains with Complex Port Geometries Fabricated Using Rapid Prototyping Technology
D. Armold, E. Boyer, B. McKnight, J. D. DeSain, J. K. Fuller, K. K. Kuo, and T. Curtiss
International Journal of Energetic Materials and Chemical Propulsion, Vol.13, 2014
2.0
3.0
4.0
40 50 60 70 80 90 100
Paraffin CorrelationSP ParaffinSP Par80%/Al20%
1-V TRB Paraffin (1/4 tpi)3-V TRB Paraffin (1/4 tpi)1-V TRB Par80%/Al20% (1/4 tpi)
Reg
ress
ion
Rate
(m
m/s
)
Oxidizer Mass Flux (kg/m2-s)
1.4150
Hot-Fire Test Results (cont’d)
Increased regression rate through printed features
15
Test Results- Effects of Pre-Heating
Testing of Hybird Rocket Fuel Grains at Elevated Temperatures with Swirl Patterns Fabricated Using Rapid Prototyping Technology
Brendan R. McKnight, Derrick Armold2, J. Eric Boyer3, and Kenneth K. Kuo4
John D. DeSain5, Jerome K. Fuller6, Brian B. Brady7, and Thomas J. Curtiss8
50th AIAA Joint Propulsion Conference
Significant Increase in Regression Rate without Drop in Isp
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
40 50 60 70 80 90 100 200
Paraffin CorrelationCast Paraffin SP 22CLg Swept HC 22C (1/4 tpi)Lg Swept HC 50C (1/4 tpi)Cast Paraffin SP 35CCast Paraffin SP 55C
Reg
ress
ion
Ra
te, m
m/s
Oxidizer Mass Flux, kg/(m^2-s)
AM enables faster burning, more efficient paraffin grains
16
Combing Printed and Cast Propellants
Significant Increase in Regression Rate without Drop in Isp
Hollow AM grains with flow management features
AM hollow grains
• Provide Containment,
Structure
• Allow heating (energy
efficient, faster burn)
• Provide Flow Management
Features (Turbulators, etc.)
• Leave the port-positive in
place or melt it awayPour (cast)
Almost Any
Propellant
Almost
Any Port
Shape
17
Combing Printed and Cast Propellants (cont’d)
Significant Increase in Regression Rate without Drop in Isp
Hollow AM grains with flow management features
AM hollow grains accept propellants that
are hard to “print” like APCP (ammonium
perchlorate composite propellant):
• Ammonium Perchlorate and some
energetic additives degrade at FDM/FFF
temperatures
• Crosslinked, Thermoset, HTPB (if you
must)
• Mechanically weak propellants (paraffin,
etc.)
• Novel grain shapes realized through AM
could allow almost any thrust profile Some Traditional Port Cast
Propellant Shapes and their
Thrust Profiles
18
Combing Printed and Cast Propellants (cont’d)
Significant Increase in Regression Rate without Drop in Isp
Hollow AM grains with flow management features
0
50
100
150
200
250
300
350
400
450
0 2 4 6 8 10 12 14
ABS / Paraffin with Integrated 3-Fin Turbulator and GOX
Pre Tank Post Tank Chamber Temp
19
Combing Printed and Cast Propellants (cont’d)
Significant Increase in Regression Rate without Drop in Isp
Hollow AM grains with flow management features
20
Large Printers are Now Capable of Launch Vehicle Size
SEEMECNC’S “PARTDADDY”
PHOTO COURTESY OF SEEMECNC
• New, large format printers (industrial robots) eliminate
size constraints for some fuels (CF/ABS) - VERY large
prints are possible
• Large enclosed printers can print 154Kg (340lb) ABS
• Delta printers have stationary build platforms, enabling
very large prints
A LARGE FFF PRINTER BASED ON INDUSTRIAL ROBOTS
PHOTO COURTESY LOCKHEED MARTIN CORPORATION.
AN ENCLOSED CARTESIAN FFF PRINTER WITH A HEATED
BUILD VOLUME
PHOTO COURTESY OF COSINE ADDITIVE, INC.
Print size – no longer a limitation
21
Large Printers are Now Capable of Launch Vehicle Size
2-SEAT CAR BEING PRINTED ON BAAM
PHOTO COURTESY OF CINCINNATI INC.
• Cincinnati Inc’s BAAM, billed as Largest AM
• Print envelope 20 x 7.75 x 6 feet
• Carbon Fiber filled ABS material
(probably capable of CF/Nylon)
Print size – no longer a limitation
BAAM PRINTER, PHOTO COURTESY OF CINCINNATI INC.
23
Liquid-Enhanced Hybrid and Hybrid-Like Liquid Motors
• Adding small amounts of liquid fuel
– Increases combustion temperature, further increasing regression rate for
the solid fuels
– Increases solid fuel surface area as liquids are consumed
• Adding large amounts of liquid fuel
– Moves us toward a simpler liquid motor
– Allows less expensive, more easily obtained fuels to be used
– Will need significant research
24
Hybrid-Like Liquid MotorsRemoving Turbopumps = Removing a Major Cost
• Can Liquid Motors be made like
Hybrids?
• Expensive, highly refined
“Rocket fuels” like RP1 are
unnecessary
– RP-1 used to lubricate pumps
(typically no pumps on hybrids)
– Jet A (commonly available
kerosene)
– “Bunker Fuel” (Alkane lengths of
C= 12 – 70)
– Biofuels
Oxidizer
Fuel
Turbo-
pumps
Fuel
Management
Structures
Fuel
25
Fuel Metering Strategies
• Tapered Port Wall
• Stacked Cones
• Spiral
• Enhanced Hybrid (small amounts of liquid)
C) Liquid-Enhanced
Hybrid
B) SpiralA) Stacked Cone
26
Post Combustion Chamber Pressure
Analogous to thrust, increases with added kerosene
Adding kerosene significantly increases burn rate over solid ABS
(blowout)
27
Liquid Fuel Passive Metering Example:Triple Canted Helix + Tapered Port Wall
Liquid Fuel Pours
Into Port as Port
Wall Regresses
Thin Port Wall (top)
Burns-Through First
28
Liquid Fuel Passive Metering Example (cont’d):Triple Canted Helix, Tapered Port Wall
Burned and Unburned Specimen
(50mm diameter)
Cut-away showing Canted Spiral
and Tapered Port Wall
31
Conclusion (and Caveats)
• Novel port shapes and design features are possible though AM
• Regression rate (Thrust) can be Doubled
• Specific Impulse (Efficiency) can also be increased
• Launch-vehicle–size fuel grains are within reach
• Inexpensive liquid motors may be possible
• A small amount of liquid fuel can enhance Hybrids
• Entirely new concepts like heated paraffin motors are enabled
• These things are true for SMALL motors
• Nobody knows how to passively control the flow of liquid fuel yet
• More work is needed, especially at larger scales
32
Acknowledgements:
• The Aerospace Corporation
– John DeSain, Brian Brady, Andrea Hsu, Tom Curtis, Cody Shaw, Kevin Dorman
– The Aerospace Corporation’s Independent Research and Development
program.
• Pennsylvania State University