1. Inputs on HPM EPS, SEP Stage Block II configuration, and comments on 10/2 presentation package
Tim Sarver-Verhey
10/1/2001

2. HPM Power System - Update
Power system performance & characteristics
2/16/2019
GRC/TRSV

3. CTM Power System - Update
Power system performance & characteristics
2/16/2019
GRC/TRSV

4. SEP Stage - Orbit Transfer Performance
Transfer from ISS orbit to 320, °
Assumed low-thrust spiral
Inclination change performed throughout spiral
Total Vehicle Mass
59.7 MT
36.3 MT fixed payload assumed (31.1 Chem load MT HPM dry mass)
16.3 MT for return trip: SEP Stage + Empty HPM
Propellant Mass
12.2 MT for out-bound
Trip Time
272 days out-bound
2/16/2019
GRC/TRSV

5. SEP Stage - System Summary
Thrusters
9 Gridded ion engines required
1 spare included
PPUs on deployed palette
PV Arrays
2 Square rigger wings employed
Array area = 2700 m2
Power produced = 450 kW
Assume 5 kW for system power
Power density = 167 W/m2
Arrays fixed on base palette
HPM/Base to fly solar inertial
Articulated Boom
20 m coilable main boom section
2 rigid segments to extend thruster reach
SEP System
“Dry” Mass = 11.2 MT
Includes 2 MT of xenon on-board
2/16/2019
GRC/TRSV
Mass Breakdown

6. SEP Stage - Detailed Mass Breakdown
Radiator area: 30.2 m2
Radiator area: 24.6 m2
2/16/2019
GRC/TRSV

7. Hybrid Propellant Module (HPM) Mass & Technology Summary
3939
Calculated Dry Mass
165
Dry Mass Margin
943
Shielding
1314
Structures
4,104
Dry Mass Target Mass
1,089
Propellant Management
305
Power
234
Thermal 42
Command/Control/Comm 12
Navigation/Attitude Control
Calculated Mass (kg)
Subsystem
HPM Advanced Technology Requirements
Integrated Flywheel Energy Storage System
- Combination energy storage and attitude control
Advanced Triple Junction Crystalline Solar Cells
>30% efficiency
Zero Boil-Off System
- Cryogenic propellant storage system (up to 10 years of storage without boil-off)
Integrated Primary Multifunction Structure & Meteoroid and Orbital Debris Shield
- Non-metallic hybrids to maximize radiation protection
Autonomous Operations including Rendezvous and Docking
On-Orbit Cryogenic Fluid Transfer
Lightweight Composite Cryogenic Propellant Storage Tanks
Graphitic Foams and Syntactic Metal Foams
Carbon-Carbon Composite Radiators
2/16/2019
GRC/TRSV

8. Crew Transfer Vehicle (CTV) Mass & Technology Summary
Technologies Currently Used in CTV
Advanced Triple Junction Crystalline Solar Cells
Provide >500 W/kg (blanket)
>30% efficiency or
Integrated Primary Multifunction Structure & Meteoroid and Orbital Debris Shield
Non-metallic hybrids to maximize radiation protection
Autonomous Operations including Rendezvous and Docking
Lightweight Composite Cryogenic Storage Tanks
Graphitic Foams and Syntactic Metal Foams
Carbon-Carbon Composite Radiators
Advanced ECLSS CO2 Removal System
5.5m
Graphic deleted
Mass of Full (CTV) = 5282 kg
2/16/2019
GRC/TRSV

9. Solar Electric Propulsion Module (SEP) Mass & Technology Summary
Photovoltaic Arrays: 2 square-rigger style wings (rad hard as possible)
Thin film cells, Array area = 2700 m2, Power produced = 450 kW
Thrusters: 8 Gridded Ion Engines, operating at 50 kW
Xenon, 3,300 s Isp, 2.0 N thrust per engine, 15 khours lifetime (Minimum)
Articulated boom for thrust vectoring
Base Palette containing
Extra Xenon for free-flying operation
Arrays mounts
Power processing
Reaction Control system
Attitude Control system
HPM docking & Fluid Transfer interfaces
Mass of Full (SEP) =11,000 kg
(includes 2000 KG of Xenon)
2/16/2019
GRC/TRSV

10. Overall Technology Summary
Key Technologies
Integrated flywheel energy storage system
Advanced triple junction crystalline solar cells
Zero Boil-Off (ZBO) system
Integrated primary multifunction structure, radiation & meteoroid and orbital debris shielding
Autonomous operations including rendezvous and docking
On-orbit cryogenic fluid transfer
Lightweight cryogenic propellant tanks
Graphitic foams and syntactic metal foams
Carbon-carbon composite radiators
High performance, high cycle life LH2/LOX main engine
Integrated GH2/GOX Reaction Control System (RCS)
Advanced ECLSS CO2 removal system
Large deployable thin film arrays
Gridded ion engines
HPM CTV CTM SEP
3-axis control possible axis control 3-axis control
> 40% eff > 40% eff > 40% eff % eff
Multistage NA NA NA
Also provides Also provides Also provides Yes
thermal radiation thermal
Insulation shielding insulation
MANS/AFF MANS/AFF MANS/AFF MANS/AFF
LH2/LO2/Xenon NA LH2/LO2/Xenon Xenon/GH2/GO2
Composite NA Aluminum Composite
YES YES YES YES
NA NA Starts NA
0.995 reliability
NA NA Yes YES
NA YES NA NA
NA NA NA W/m**2, rad res’t.
NA NA NA Hi-power, >15kh life
2/16/2019
GRC/TRSV

11. Summary & Forward Work
The HPM concept in the OASIS framework could reduce costs and enhance mission robustness across a wide spectrum of future space activities.
Economic sensitivities for NASA and commercial applications have indicated that inexpensive launch of propellant on the order of $1000/kg is the threshold for making a space based transportation infrastructure viable.
Solar Electric Propulsion technologies (high performance, radiation resistant arrays, long-lived high performance gridded ion engines, large deployable systems) present significant technology development challenges, which can be achieved with sufficient resources. Pat: folks here aren’t too comfortable having SEP called out as tall pole (yet again), in particular since many other elements of this program are little more than paper studies (launch vehicles and their costs, Gateway/OASIS, light-weight cryo-tanks, etc.) Can this statement be further revised so that SEP doesn’t appear to be the lone ‘bad guy’ for this mission?
Follow-on activities under RASC have been proposed for FY02:
Refined commercial and DOD applications
Increased detail assessments for other supporting concepts (SEP, CTM, CTV, etc)
Applications beyond the Earth-Moon system
2/16/2019
GRC/TRSV