1. Tether Boost Facilities for
In-Space Transportation
Robert P. Hoyt, Robert L. Forward
Tethers Unlimited, Inc.
1917 NE 143rd St., Seattle, WA 98125-3236
+1-206-306-0400 fax -0537
TU@tethers.com www.tethers.com
John Grant, Mike Bangham, Brian Tillotson
The Boeing Company
5301 Bolsa Ave., Huntington Beach, CA 92647-2099
(714) 372-5391

2. TUI/MMOSTT 2
NIAC Funded Tether Research
¥ Moon & Mars Orbiting Spinning Tether Transport (MMOSTT)
¥ Hypersonic Airplane Space Tether Orbital Launch (HASTOL)
¥ Objectives:
Ð Perform Technical & Economic Analysis of Tether Transport Systems
Ð Identify Technology Needs
Ð Develop Conceptual Design Solutions
Ð Prepare for Technology Development Efforts and Flight Experiments
to Demonstrate Tether Transport Technology

3. TUI/MMOSTT 3
Momentum-Exchange
Tether Boost Facility
¥ High-strength tether rotates around orbiting control station
¥ Tether picks payload up from lower orbit and tosses payload into higher orbit
¥ Tether facility gives some of its orbital momentum & energy to payload
¥ Tether facility orbit must be restored to enable it to toss additional payloads

4. TUI/MMOSTT 4
Electrodynamic Reboost
Magnetic Field
Thrust Current
Plasma Contactors
(Hollow Cathode,
FEA, Bare Wire)
¥ Power supply drives current
along tether
¥ Plasma contactors exchange
current with ionosphere
¥ Plasma waves close current
ÒloopÓ
¥ Current ÒpushesÓ against
geomagnetic field via JxB
Force

5. Momentum-Exchange/Electrodynamic-Reboost Tethers:
TUI/MMOSTT 5
Summary of Advantages
¥ Tether Boost Facilities Can Provide a Fully-Reusable In-Space
Propulsion Architecture
Ð LEO Û MEO/GTO
Ð LEO Û Lunar Surface
Ð LEO Û Mars
Ð ETO Launch, in combination with Hypersonic Airplane/RLV
¥ Momentum Exchange + Electrodynamic Tether Can Enable
Propellantless Propulsion Beyond LEO
¥ Rapid Transfer Times
Ð 5 days to Moon
Ð 90-130 days to Mars
¥ Operational Tether System Can Be Tested Before Use With High-
Value Payloads
¥ Reusable Infrastructure + Low Consumables
Þ Lower Cost

6. Cislunar Tether Transport System
¥ Developed Orbital Architecture for Round Trip LEOÛLunar
Surface Transport
¥ Whole System Launch Mass = 30x Payload Mass
Ð LEO Tether Boost Facility Mass = 13x Payload Mass, Lunar Tether Facility = 17x Payload
¥ 13 Payloads/Year
¥ Incremental Commercial Development Path
TUI/MMOSTT 6

7. Rapid Earth-Mars Transport
¥ Reusable Architecture for Round Trip Earth to Mars Transport
¥ Rapid Transfer Times (90-130 days)
INTERPLANETARY TRANSPORT USING
ROTATING TETHERS
Payload pick-up
Payload release Origin
TUI/MMOSTT 7
Escape
trajectory
Interplanetary
trajectory
Destination
Inbound
trajectory
Payload release
Payload capture
Patch point
Tapered tether
Loaded Tether
Center of mass
orbit
Tapered tether
Loaded Tether
Center of mass
orbit
Patch point
Earth’s gravitational
sphere of influence
Mars’ gravitational
sphere of influence
Sol

8. MXER Tethers Included in NASAÕs
TUI/MMOSTT 8
IISTP Process
¥ NIAC Funded MMOSTT and HASTOL efforts have resulted in
Momentum-Exchange/Electrodynamic Reboost Tethers being
considered in NASAÕs In-Space Integrated Space Transportation
Planning Process
¥ TUI & NASA/MSFC developed concept designs for Tether Boost
Facilities for 4 classes of missions
Ð Microsatellite
Ð 1 mt Payloads
Ð 5 mt Payloads
Ð 10 mt Payloads
¥ IISTP Process evaluated these designs in trade studies for several
different scientific missions
¥ ÒHigh-Risk/High PayoffÓ
¥ MXER Tethers scored well for several classes of missions
Ð High Performance metric

9. TUI/MMOSTT 9
Tether Architecture for
LEO-GTO-LTO-Mars Transport
¥ Tether facility serves as transport hub for multiple destinations
¥ Tether serves as a zero-propellant, reusable, high-Isp, high thrust
ÒThird StageÓ

10. TUI/MMOSTT 10
5mt Payload Tether Boost Facility
for In-Space Transportation Architecture
¥ Reusable In-Space Transportation
Infrastructure
¥ Payload Launched to 325 km LEO
¥ Tether Boosts Payload to Elliptical Orbit
¥ Tether Uses Electrodynamic Thrust to Reboost
Tether System Point Design:
¥ Boost 10,000 kg to GTO
¥ Boost 5,000 kg Vehicle to :
Ð Highly Elliptical Orbit (C3=-1.9)
Ð Lunar Transfer Trajectory
Ð Escape Via Lunar Swingby
¥ Tether Facility Launch Mass: 63 mt
Ð Deploy using 3 Delta-IV-H LVÕs
Ð Retain Delta Upper Stages for Ballast
Ð 200 kW EOL Power Supply for 1 Month Reboost
Analysis of Other Propulsion Technologies with
MX Tether Assist:
¥ Delta-II-Class LV Launches 5,000 kg Spacecraft
¥ Tether Boosts Spacecraft to C3Ê=Ê-1.9 km2/s2
¥ High-Thrust Propulsion Systems:
Ð Do Injection Burn at Perigee (570 km, 10.62 km/s)
¥ Low-Thrust Propulsion Systems:
Ð Use Lunar Swingby to Escape EarthÕs Gravity Well

11. Net Payoff: Reduced Launch Costs
To launch 5,000 kg to GTO:
¥ Using Rockets: Delta IVM+(4,2) or SeaLaunch
TUI/MMOSTT 11
~ $90M
¥ Using Rocket to LEO, Tether Boost to GTO:
Ð Delta II 7920 (~$45M) or Dnepr 1 (~$13M)
Ø1/2 to 1/7 the launch cost

12. TUI/MMOSTT 12
LEOðGTO Boost Facility
¥ Initial Facility Sized to Boost 2500 kg Payloads to GTO
¥ First Operational Capability Can Be Launched on 1 Delta IV-H
¥ Modular Design Enables Capability to be Increased
¥ Top Level Mission Requirements:
Requirement Value
2500 kg at IOC, can grow to follow
market
Payload Mass
Pickup orbit 300 km equatorial
Release orbit GTO
Release insertion error < Delta IV/Ariane 5
Payload environment < Delta IV/Ariane 5
Turnaround time 30 days
Mission life 10 years +
Collision avoidance 100% of tracked spacecraft
Operational orbit lifetime 15 days
Payload pickup reliability 99%

13. TUI/MMOSTT 13
Mass Properties Breakdown
LEO Control Station 10967 13267 2300
Thermal Control Subsys 1 15% 1104.5 1270.1 165.7
Cabling/Harnesses 33% 749.6 997.0 247.4
Structure 25% 2721.1 3401.3 680.3
Electr.Pwr. 4736.7 5409.6 673.0
PV array panels 1 1 13% 1782.9 1782.9 2014.6
Power Storage 1 1 15% 2860.5 2860.5 3289.5
PV array drive motors 8 2 13% 3.0 48.0 54.2
PMAD 1 2 13% 22.7 45.4 51.3
Downlink Comm Subsys 1.8 2.1 0.2
Downlink Transceiver 1 2 13% 0.7 1.4 1.56
Downlink antennae 2 1 13% 0.2 0.5 0.51
TFS Net Comm Subsys 1.8 2.1 0.2
Comm. antennae 2 1 13% 0.2 0.5 0.51
Transceiver 1 2 13% 0.7 1.4 1.6
C&DH 26.0 29.4 3.4
Computer 1 2 13% 13.0 26.0 29.4
TT&C 6.9 7.8 0.9
transponder 1 2 13% 3.5 6.9 7.8
ADCS 200.9 213.8 12.9
ED Tether Power Subsys 417.4 603.4 186.0
Plasma Contactor (FEAC) 1 2 25% 45.4 90.8 113.5
PMAD/PCUt 1 2 50% 163.3 326.6 489.9
Docking & I/C Subsys 0.5 0.54 0.04
Beacon 1 1 8% 0.5 0.5 0.54
Tether Deploy & Control 1000.0 1330.0 330.00
Tether reeling assembly 1 1 33% 1000.0 1000.0 1330.0
Mass
Margin
(kg)
Mass with
Contingency
(kg)
Mass with
no margin
(kg)
Unit
mass
(kg)
Mass
Contin
gency
Redun
dancy
Qty Control Station
Mass: 10,967 kg
Tether Mass:
8,274 kg
Grapple Mass:
650 kg
GLOW: 19,891 kg
Ð 15% margin w/in Delta
IV-H payload capacity
Expended Upper Stage
3,467 kg
On-Orbit Mass:
23,358 kg

14. TUI/MMOSTT 14
Tether Boost Facility
Control Station
¥ Solar Arrays, 137 kW @ BOL
¥ Battery/Flywheel Power Storage
¥ Command & Control
¥ Tether Deployer
¥ Thermal Management
Tether (not shown to scale)
¥ Hoytether for Survivability
¥ Spectra 2000
¥ 75-100 km Long
¥ Conducting Portion for
Electrodynamic Thrusting
Total Mass:ÊÊÊÊ 23,358 kg
Payload Mass: 2,500 kg
Grapple Assembly
¥ Power, Guidance
¥ Grapple Mechanism
¥ Small Tether Deployer
Payload Accommodation
Assembly (PAA)
¥ Maneuvering & Rendezvous Capability
¥ Payload Apogee Kick Capability
Payload

15. NIAC Efforts Have Developed
Improved Tether Analysis Tools
Tether System Design:
Ð Tapered tether design
TUI/MMOSTT 15
¥ Spectra 2000
Ð Orbital mechanics considerations to
determine facility mass required
Tether operation: TetherSimª
¥ Numerical Models for:
Ð Orbital mechanics
Ð Tether dynamics
Ð Electrodynamics
Ð Hollow Cathode & FEACs
Ð Geomagnetic Field (IGRF)
Ð Plasma Density (IRI)
Ð Neutral Density (MSIS Ô90)
Ð Thermal and aero drag models
Ð Endmass Dynamics
Ð Payload Capture/Release
¥ Interface to MatLab/Satellite Tool Kit

16. TUI/MMOSTT 16
LEOðGTO Boost Facility
¥ TetherSimª Numerical Simulation (10x real speed)
Ð Tether Dynamics, Orbital Mechanics

17. TUI/MMOSTT 17
Technology Readiness Level
¥ Boeing & TUI Performed TRL Analysis of MXER Tether
Technologies
¥ Many necessary components are already at high TRL
¥ TRL Analysis Indicates Areas for Future Work to Address:
Ð Power management subsystem
Ð Thermal control subsystem
¥ Higher power than previously flown systems
Ð Electrodynamic Propulsion Subsystem
¥ Plasma contactors
¥ Dynamics control
Ð Automated Rendezvous & Capture technologies
¥ Prediction & Guidance
¥ Grapple Assembly & Payload Adapter
Ð Some work ongoing in HASTOL Ph II effort
Ð Flight Control Software
Ð Traffic Control/Collision Avoidance

18. TUI/MMOSTT 18
20
12
8
4
0
ÆZ (m)
16
-10 0 10
ÆX (m)
Rendezvous
¥ Rapid AR&C Capability Needed
¥ Relative Motion is Mostly in Local Vertical
¥ Tether Deployment Can Extend Rendezvous
Window
¥ Additional Tether Deployment Under Braking Can Reduce Shock
Loads
Payload Capture Vehicle
descends towards Payload
PCV Deploys
More Tether PCV pays out tether
and Payload maneuvers
to dock with grapple
PCV engages
tether brake and
begins to lift payload
1
0.8
0.6
0.4
0.2
0
0 10 20
Load Level
30 40 50
0.1 s braking
5 s braking
10 s braking
20 s braking
Time (s)
30 s braking

19. Space Debris-Survivable Tether
¥ Micrometeoroids & Space Debris Will
Damage Tethers
¥ Solution approach: spread tether material
out in an open net structure with multiple
redundant load/current paths
TUI/MMOSTT 19
Primary
Lines
Secondary
Lines
(initially
unstressed)
0.2 to
10's of
meters
0.1- 1 meter
Severed
Primary
Line
Effects of
Damage
Localized
Secondary
Lines
Transfer
Load Around
Damaged
Section

20. TUI/MMOSTT 20
Proposed RETRIEVE Tether
Experiment
¥ Candidate Secondary
Experiment for XSS-11
¥ $800K in Initial Development
funds from AFRL
¥ Small ED tether system deorbits
µSat at end of mission
Ð Activated only after primary
mission completed
¥ Mass: (CBE+Uncertainty):
6.5 kg
¥ Demonstrate
Ð Controlled orbital maneuvering
with ED tether
Ð Long life tether
Ð Stabilization of tether dynamics

21. µTORQUE: MX Tether to Boost µSat to
¥ Microsatellite Tethered Orbit Raising QUalification Experiment
¥ Build Upon RETRIEVE to Create Low-Cost Demo of MXER tether technology
¥ Secondary payload on GEO Sat launch
¥ µTORQUE boost microsat payload to lunar transfer or escape
¥ 0.4 km/s boost to payload
¥ Mass-competitive with chemical rocket
TUI/MMOSTT 21
Lunar Transfer or Escape
Launch vehicle
places primary
payload into GTO
µTORQUE uses ED
drag to spin up tether
µTORQUE deploys tether &
microsat above stage
µTORQUE releases
payload into lunar
transfer/swingby

22. TUI/MMOSTT 22
µTORQUE on Delta IV
¥ Delta-IV Secondary Payload
¥ ~100 kg weight allocation
¥ Boost ~80kg microsat from
LEO to low-MEO

23. Momentum Exchange/Electrodynamic Reboost
NIAC Study
ProSEDS
TUI/MMOSTT 23
Tether Technology Roadmap
GRASP
Experiment
µTORQUE
Experiment
ED-LEO Tug
µPET
LEO Û GTO
Tether Boost Facility
ISS-Reboost
Terminator
Tetherª
Cislunar Tether
Transport System
ETO-Launch
Assist Tether
RETRIEVE
2001 2003 2005 2010 2013 2016 2025 2035

24. TUI/MMOSTT 24
Opportunities for NASA
Technology Development
¥ Expand AR&C Capabilities for Rapid Capture
¥ High Power & High Voltage Space Systems
¥ Electrodynamic Tether Physics
¥ Debris & Traffic Control Issues
¥ Conduct Low-Cost Flight Demo of Momentum-
Exchange Tether Boost
Modest NASA Investment in Technology
Development Will Enable Near-Term Space
Flight Demonstration

25. TUI/MMOSTT 25
Contributors
¥ Boeing/RSS - John Grant, Jim Martin, Harv Willenberg
¥ Boeing/Seattle - Brian Tillotson
¥ Boeing/Huntsville - Mike Bangham, Beth Fleming, John Blumer,
Ben Donohue, Ronnie Lajoie, Lee Huffman
¥ NASA/MSFC - Kirk Sorenson
¥ Gerald Nordley
¥ Chauncey Uphoff