Space-based Hydrogen-Oxygen Hybrid Open/Closed Cycle Integrated Power and Thermal Management System

1. Space-based High-power
Generation Systems
For Space-based Strategic Defense
Initiative (SDI) Anti-ballistic Missile
System

2. Overview
• Background
• Closed-cycle Nuclear Power System Concept
• Open-cycle Nuclear Power System Concept
• Conventional Open-cycle Chemical Power System
Concept
• Hybrid-cycle Chemical Power System Concept
• Integrated Power –Thermal Management System
• High-power Density Turbogenerators
• Integrated generator-power conditioning system

3. Background
• Several SDI scenarios called for space-based
multi-megawatt power systems
• Not need frequent resupply
• Go from idle to full power very quickly
• Minimal impact on other platform systems
• Compact
• Lightweight
• Reliable
• Hardened from natural and artificial threats

4. Options
• No one concept satisfied all conditions
• Three concepts satisfied most
• Closed-cycle Nuclear Power System
• Open-cycle Nuclear Power System
• Open-cycle Chemical Power System

5. Closed-cycle Nuclear Power System
• Nuclear reactor energy source
• Electrical power generation techniques
– Dynamic: Brayton, Stirling, Rankine…Cycles
– Direct: Thermionic, Thermoelectric, AMTEC…
• Radiate waste heat to space
– Waste heat from power generation system
– Waste heat from mission-critical components
(sensors, computers and equipment)

6. Open-cycle Nuclear System Operation
• Nuclear reactor provides heat
energy for power generation
system to drive turbines or direct
energy conversion system
• Electricity from power generation
system powers equipment to
accomplish platform mission
• Power generation system radiates
waste heat to space at
temperature that will give
maximum efficiency
• Platform electrical equipment
radiates waste heat to space at
temperatures that will maximize
their efficiency
Nuclear
Reactor
Power
Generation
System
Radiate
Heat to
Space
Space
Platform
Electrical
Loads
Radiate
Heat to
Space
Heat
Electricity
Heat
Heat

7. Closed-cycle Nuclear System
Advantages & Disadvantages
Advantages
• No exhaust gases to
interfere with sensors or
cause undesired platform
motion
• Only reaction control
system (RCS) thrusters
need resupply
• Involves developing high
thermal capacity
survivable radiators for
applications in space
Disadvantages
• ~ 10 times heavier than
open-cycle concepts
• Safety and security issues
involved in launching
nuclear reactors into
space
• Safety and security issues
involved with reentry of
orbiting nuclear reactors

8. Open-cycle Nuclear Power System
• Nuclear reactor energy source
• Hydrogen stored on space platform
– Stored as a liquid (LH2) at about -420 F (-250 C)
• Minimize size of storage containers
• Maximize cooling capacity of hydrogen
– Coolant for mission-critical sensors, computers
and equipment on space platform
– Heated hydrogen powers turbines
• Exhaust hydrogen from turbines to space

9. Open-cycle Nuclear System Operation
• Pump increases the pressure of the
hydrogen and provides the energy to
move it through the rest of the system
• The temperature of the hydrogen
increases as it flows through the
Platform thermal Management System
cooling the Platform Electrical Loads
and the Generators.
• The hydrogen then flows through the
Nuclear Reactor further increasing its
temperature.
• The high temperature, high pressure
hydrogen then expands through the
Turbines providing the mechanical
energy to drive the Generators
• The Generators provide the electrical
energy for the Platform Electrical and
Electronic Components
• The hydrogen then exhausts to space
through thrust-cancelling nozzles.
Nuclear
Reactor
Platform
Thermal
Management
System
Platform
Electrical and
Electronic
Components
Electricity
Exhaust
to space
Heat
LH2
Pump
Generators Turbines

10. Open-cycle Nuclear System
Advantages & Disadvantages
Advantages
• ~1/10 Weight of closed-
cycle nuclear concept
• No products of
combustion in gases
exhausted to space
• Based on 1960s Nuclear
Engine for Rocket
Vehicular Application
(NERVA) technology
Disadvantages
• Resupply LH2 due to boil-
off and periodic system
readiness checks
• Hydrogen cloud can
interfere with some
sensors and systems
• Thrust imbalances from
nozzles can affect
platform stability and
control requiring more
reactants for RCS
thrusters

11. Open-cycle Chemical Power System
• Chemical Energy (Combustion) Power Source
• Hydrogen (LH2) stored on platform, coolant for
mission-critical components
• Liquid oxygen (LOX) stored on platform at about -
300 F (-180 C)
• Fuel-rich H2-O2 combustion provides hot
hydrogen and water-vapor to power turbines and
generators
• Exhaust hydrogen and water vapor from turbines
to space

12. Open-cycle Chemical System
Operation
• Pump increases the pressure of the hydrogen
and provides the energy to move it through the
rest of the system
• The temperature of the hydrogen increases as it
flows through the Platform Thermal
Management System cooling the Platform
Electrical Loads and the Generators.
• The hydrogen then flows into the Combustor
where hydrogen-rich combustion provides the
additional heat necessary to power the turbines
and generators.
• The high-temperature, high-pressure hydrogen
and steam then expand through the Turbines
providing the mechanical energy to drive the
Generators
• The Generators provide the electrical energy for
the Platform Electrical and Electronic
Components
• The hydrogen and steam then exhaust to space
through thrust-cancelling nozzles.
Combustor
Platform
Thermal
Management
System
Platform
Electrical and
Electronic
Components
Electricity
Exhaust
to space
Heat
LH2
Pump
Generators Turbines
Pump
LOX

13. Open-cycle Chemical System
Advantages & Disadvantages
Advantages
• ~1/10 Weight of closed-cycle
nuclear concept
• Does not have the safety and
security issues associated with
nuclear power system
concepts
Disadvantages
• Resupply LH2 and LOX due to
boil-off and periodic system
readiness checks
• Hydrogen and water vapor
cloud can interfere with some
sensors and systems
• Water vapor can damage
some mission-critical systems
• Thrust imbalances from
nozzles can affect platform
stability and control requiring
more reactants for RCS
thrusters

14. Hybrid Chemical Power System
• Chemical Energy (Combustion) Power Source
• Hydrogen (LH2) stored on space platform, coolant for mission-
critical components
• Liquid oxygen (LOX) stored on platform at about -300 F (-180 C)
• ~10% of H2 from thermal management system diverted to
combustor/heat exchanger
• Ideally stoichiometric H2-O2 combustion heats pure hydrogen to
power turbines and generators
• Exhaust pure hydrogen from turbines to space
• Pure hydrogen to power turbines condenses water vapor from H2-
O2 combustion
• Condensed water stored as a liquid on the space platform

15. Hybrid Chemical System Operation
• Pump increases the pressure of the hydrogen and
provides the energy to move it through the rest of
the system
• The temperature of the hydrogen increases as it
flows through the Platform Thermal Management
System, cooling the Platform Electrical Loads and
the Generators.
• ~10% of the hydrogen then flows into the high
temperature end of a combined
combustor/counter-flow heat exchanger where
ideally stoichiometric H2-O2 combustion heats the
pure hydrogen to power the turbines and
generators.
• The remaining pure hydrogen then flows into the
low temperature end of the combined
combustor/heat exchanger absorbing heat from the
stoichiometric H2-O2, as it condenses the water
vapor from the combustion
• The pure hydrogen at high-temperature, high-
pressure then expand through the Turbines
providing the mechanical energy to drive the
Generators
• The Generators provide the electrical energy for the
Platform Electrical and Electronic Components
• The pure hydrogen then exhausts to space through
thrust-cancelling nozzles.
Combustor/
Heat
Exchanger
Platform
Thermal
Management
System
Platform
Electrical and
Electronic
Components
Electricity
Exhaust
to space
Heat
LH2
Pump
Generators Turbines
LOX
Pump
H2O

16. Hybrid Chemical System
Advantages & Disadvantages
Advantages
• No products of combustion
in exhaust plume
• Does not have the safety
and security issues
associated with nuclear
power system concepts
• Involves evolutionary, not
revolutionary, advances in
existing technologies
Disadvantages
• Resupply LH2 and LOX due
to boil-off and periodic
system readiness checks
• Heavier than open-cycle
chemical system
• More complex than open-
cycle chemical system
• Thrust imbalances from
nozzles can affect platform
stability and control
requiring more reactants for
RCS thrusters

17. System of Choice
• Open-cycle Chemical Power Systems
– Minimum mass
– Minimum system complexity
– Rapid start capability
– Lowest risk technology, compared to nuclear
systems)
• Hybrid Chemical Power System identified as
an “enabling technology” and the system-of-
choice

18. Additional Contributions
• Power generation system required large 24 stage
axial flow turbines
– Weight of axial turbine stages Diameter2
– Turbine stage diameters increase in size with each
successive stage
• Key component required very high voltage DC
power (100 kVDC)
• Equipment to provide 100 kVDC (transformers
and power-conditioning devices) can weigh as
much as the turbines and generators combined

19. Solution to Turbine Size and Weight
• Ljungström Turbine
• Gasses flow through stages
radially from the center of the
disks
• Counter-rotating turbine disks
• Four times the energy
conversion per stage as axial
turbines
• Six stages instead of twenty-
four
• Torque from counter-rotating
disks naturally cancel each
other
RotationRotation
H2 Flow
H2 Flow

20. Solution to Power Conditioning Issues
• Teamed with electrical
engineer coworkers to
configure:
– Four 25 kV generators
connected in series
– Full-wave rectification to get
direct current
– Arranging phases to minimize
ripple < 2%
• Result: US Patent 4,780,659
• Satisfied electrical power
and quality requirements
without transformers and
power conditioning3

21. Conclusions
• Developed or employed enabling technologies for the customer
• Devised chemical energy power source with no products of
combustion in exhaust plume
– Advantages of open-cycle nuclear system (no products of combustion)
– Advantages of chemical system (non-nuclear power source)
• Selected high-power density Ljungström
– 4X Energy conversion per stage than axial turbines
– Counter-rotating rotors naturally cancel torque
• Teamed-up with electrical engineering coworkers to devise
integrated power generation-power conditioning concept to
provide 100 kVC with less than 1% ripple
– No transformers
– No power conditioning equipment to provide high voltage DC with less
than 2% ripple

22. References
1. Open-Cycle Chemical Power and Thermal Management
System With Combustion Product-free Effluent, G. S.
Hosford, K. Weber, Sundstrand Corporation, Rockford, IL;
R. Giellis, Martin Marietta Aerospace, Denver, CO. AIAA
Thermophysics, Plasmadynamics and Lasers Conference,
June 27-29, 1988, San Antonio, Texas
2. Hydrogen-Oxygen Thruster With No Products of
Combustion in Exhaust Plume, Gregory S. Hosford, Ken
Clodfelter, Sundstrand Advanced Technology Group,
Rockford, IL, AIAA/SAE/ASME/ASEE 23rd Joint Propulsion
Conference, June 29-July 2, 1987/San Diego, Ca.
3. Patent 4,780,659 - High-Power, High-Voltage Direct
Current Power Source, Madan L. Bansal, Alexander
Krinickas, Jr., Figure 2