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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 [email protected] www.tethers.com John Grant, Mike Bangham, Brian Tillotson The Boeing Company 5301 Bolsa Ave., Huntington Beach, CA 92647-2099 (714) 372-5391

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Tether Boost Facilities forIn-Space Transportation

Robert P. Hoyt, Robert L. ForwardTethers Unlimited, Inc.

1917 NE 143rd St., Seattle, WA 98125-3236+1-206-306-0400 fax -0537

[email protected] www.tethers.com

John Grant, Mike Bangham, Brian TillotsonThe Boeing Company

5301 Bolsa Ave., Huntington Beach, CA 92647-2099(714) 372-5391

TUI/MMOSTT 2

Ongoing Tether Work Under NIAC Funding

¥ Objectives:Ð Perform Technical & Economic Analysis of Tether Transport SystemsÐ Identify Technology NeedsÐ Develop Conceptual Design SolutionsÐ Prepare for Flight Experiments to Demonstrate Tether Transport

Technology

¥ Moon & Mars Orbiting Spinning Tether Transport (MMOSTT)Ð TUI Prime, Boeing/RSS sub

Ð Develop Design for a 2.4 km/s ÆV LEOððððGTO Tether Boost Facility

Ð Develop & Simulate Methods for Tether-Payload Rendezvous

Ð Identify Near-Term Commercial and Scientific Applications

Ð Investigate Cislunar, Mars, & other Tether Transport Architectures

¥ Hypersonic Airplane Space Tether Orbital Launch (HASTOL)Ð Boeing/RSS prime, TUI sub

Ð Design Launch Architecture Combining a ~7 km/s ÆV Tether BoostFacility with a Mach 10-12 Hypersonic Airplane

TUI/MMOSTT 3

Summary of Advantages¥ Tether Boost Facilities Can Provide a Fully-Reusable

In-Space Propulsion ArchitectureÐ LEO ⇔ MEO/GTO

Ð LEO ⇔ Lunar Surface

Ð LEO ⇔ Mars

Ð ETO Launch, in combination with Hypersonic Airplane/RLV

¥ Momentum Exchange + Electrodynamic Tether CanEnable Propellantless Propulsion Beyond LEO

¥ Rapid Transfer TimesÐ 5 days to Moon

Ð 90 days to Mars

¥ Reusable Infrastructure + Low Consumables ÄÄÄÄ Lower Cost

Lunavator inLow-LunarPolar Orbit

Tether BoostFacility inEllipticalEarth Orbit

Minimum-Energy LunarTransfer Orbit

Initial Payload Orbit

Cislunar Tether Transport System

¥ Developed Orbital Architecture for Round Trip LEOóóóóLunarSurface Transport

¥ Whole System Mass < 27x Payload MassÐ LEO Tether Boost Facility Mass = 10x Payload Mass, Lunar Tether Facility = 17x Payload

¥ 13 Payloads/Year

¥ Incremental Commercial Development Path

TUI/MMOSTT 5

Rapid Earth-Mars Transport

¥ Reusable Architecture for Round Trip Earth óóóó Mars Transport

¥ Rapid Transfer Times (90-130 days)

¥ Extended Launch Windows

¥ Currently Evaluating ArchitecturesÐ All Tether

Ð Tether/Chemical

Earth’s gravitationalsphere of influence

Sol

Mars’gravitationalsphere of influence

2.0 km/s tether tip speed 2.5 km/s tether tip speed

Approach Y e a r Open Close

Window ( d a y s ) Open Close

Window ( d a y s )

2001 0 3 / 1 8 / 0 1 0 5 / 0 7 / 0 1 5 0 0 2 / 2 5 / 0 1 0 5 / 1 8 / 0 1 8 22003 0 4 / 2 7 / 0 3 0 7 / 2 2 / 0 3 8 6 0 5 / 0 4 / 0 3 0 8 / 0 3 / 0 3 9 12005 0 7 / 2 7 / 0 5 0 9 / 0 8 / 0 5 4 3 0 7 / 3 1 / 0 5 0 9 / 2 0 / 0 5 5 12007 6 Oct comes closest - 1 0 / 0 6 / 0 7 1 0 / 2 4 / 0 7 1 82009 10 Nov comes closest - 20 Nov comes closest -2011 1 2 / 0 6 / 1 1 1 2 / 2 1 / 1 1 1 5 1 2 / 1 8 / 1 1 0 1 / 0 2 / 1 2 1 52013 1 2 / 3 0 / 1 3 0 2 / 0 8 / 1 4 4 0 0 1 / 1 1 / 1 3 0 2 / 1 6 / 1 3 3 62016 0 2 / 0 2 / 1 6 0 4 / 0 6 / 1 6 6 4 0 2 / 1 4 / 1 6 0 4 / 1 8 / 1 6 6 42018 0 3 / 2 5 / 1 8 0 6 / 2 4 / 1 8 9 1 0 4 / 0 3 / 1 8 0 7 / 0 6 / 1 8 9 4

116 Day Transfer146 Day Transfer

TUI/MMOSTT 6

Incremental Development Path

1. TORQUEª ExperimentÐ Demonstrate Momentum-Exchange & Electrodynamic Reboost

Ð Experiment Becomes Operational Facility for µSat Deployment

2. LEO óóóó GTO Tether Boost FacilityÐ Initial Capability: 2,500 kg to GTO once per month

Ð Modular Design: add additional components ðððð 5,000 kg, 7,500 kgÉ

3. LEO óóóó Lunar Tether Transport SystemÐ LEO óóóó GTO Facility Can also Send Payloads to Moon

Ð Add Lunavator to Enable Round-Trip Transport to Lunar Surface

4. LEO óóóó Mars Tether TransportÐ Tether Boost Facility Places Mars Payloads in Highly Elliptical Orbit

Ð Use Rocket for Trans-Mars Injection & Mars Capture

Ð Deploy Tether at Mars to Enable Round-Trip Transport Without Rockets

¥ Each Stage Generates Revenue to Fund Development ofLater Stages

TUI/MMOSTT 7

LEOððððGTO Tether Boost Facility

¥ Designed to Boost 2,500 kg payloads from LEO to GTO - Total ÆV = 2.4 km/s

¥ Operational Capability Can be Placed in LEO with One Delta-IV-H LaunchTether Mass: 8,275 kg

Grapple Assembly: 650 kg

Control Station Mass: 11,500 kg

Total Launch Mass: 20,500 kg

+ Delta-IV Upper Stage for Ballast: 3,490 kg

¥ Facility Orbit Resonant with Payload Orbit -> Frequent Rendezvous Opportunities

¥ Facility Can also Toss 500 kg payloads to Lunar Transfer Orbit

¥ Uses Electrodynamic Reboost to Enable Facility to Boost 1 Payload Per Month

TUI/MMOSTT 8

LEOððððGTO Boost Facility

¥ TetherSimª Numerical Simulation (10x real speed)Ð Tether Dynamics, Orbital Mechanics

TUI/MMOSTT 9

LEOððððGTO Boost FacilitySystem Definition Task

¥ TUI & Boeing have developed System RequirementsDocument for Tether Boost Facility

¥ System Concept DefinitionÐ Identify key technologies

Ð Mass and power budgets

¥ Technology Readiness Level Evaluation

TUI/MMOSTT 10

Tether Boost Facility

Control Station¥ Solar Arrays¥ Battery/Flywheel Power Storage¥ Command & Control¥ Tether Deployer

Tether (not shown to scale)

¥ Hoytether for Survivability¥ Spectra 2000¥ 75-100 km Long¥ Conducting Portion for

Electrodynamic Thrusting

Grapple Assembly¥ Power, Guidance¥ Grapple Mechanism¥ Small Tether Deployer

Payload AccommodationAssembly (PAA)¥ Maneuvering & Rendezvous Capability¥ Payload Apogee Kick Capability

Payload

Total Mass:ÊÊÊÊ 24,000 kgPayload Mass: 2,500 kg

TUI/MMOSTT 11

Control Station

Deployer Reel

Deployer Boom

Radiator Panel

Solar Panels

Electron Emitter

Upper StageFor Ballast

Power Module

Hoytether

TUI/MMOSTT 12

Modular Design

¥ Design Components for Modular Assembly¥ First Launch Gives 2.5 Ton ðððð GTO Operational

Capability¥ Second Launch Deploys Nearly Identical Facility

Hardware¥ Second Facility Boosts To Operational Orbit¥ Retract Tethers and Combine Facilities On-Orbit

Ð Parallel Power SuppliesÐ Run Tethers In Parallel

¥ Get 5 Ton ðððð GTO Capability¥ Add Additional Components to Increase Payload

Capability

Total Mass:ÊÊÊÊ 48,000 kgPayload Mass: 5,000 kg

TUI/MMOSTT 13

Grapple Assembly

Thruster

CONFIGURATION DRIVERS¥ Capture Options¥ System Rotation¥ Loads

Grapple Mechanism

2X Solar Array(can be stowed duringRendezvous & capture)

TETHER BOOM

Tracking Sensors

7.5 METERS

SIZING PARAMETERS¥ 1380 Watts¥ 15.61 Square Meter Arrays¥ 1.25 Meter Dia Capture Ring¥ 50 Kg Batteries (Ni-H2)

TUI/MMOSTT 14

Payload Accommodation Assembly

Configuration Drivers¥ Mimic Conventional Upper Stage Interfaces

To Payload And Booster¥ Track Grapple And Make Rendezvous

Corrections¥ Provide Circularization ÆV

¥ 1.9 m Dia x 1 M Long¥ 12 Thrusters, 0.7 M Dia Fuel Tank¥ 2 Primary Batteries¥ Communications & Guidance Systems¥ 3 Reaction Wheels

Payload with PAA

TUI/MMOSTT 15

Tether Facility Deployment

¥ Launch Tether Facility on Delta-IV-H (20,500 kg to LEO)

Ð Retain 3490 kg Upper Stage for Ballast

¥ 250 km, 20¡ Initial Orbit

¥ Assemble Facility On-Orbit

¥ Deploy Tether Upwards

¥ Use Electrodynamic Thrust to:

Ð Torque Orbit to Equatorial Plane

Ð Boost Apogee

Ð Spin Up Tether

¥ ~8 Months to Operational Orbit

Initial Orbit

Operational Orbit

TUI/MMOSTT 16

Tether Facility Reboost

¥ Use Electrodynamic Propulsion NearPerigee to Reboost OrbitÐ Collect electrons from ionosphere at

one end of tether & emit electrons atother end of tether

Ð Use power from batteries to push curentalong tether

Ð Current interacts with geomagnetic fieldto give JxB force

Ð Vary current to generate net thrust

¥ To achieve Reboost in 30 days:Ð Solar Panel Power: 150 kWÐ Power To ED Tether: 450 kW

¥ Issues:

Ð High Power, High Voltage (20 kV)

TUI/MMOSTT 17

Reboost Tuning

¥ Electrodynamic thrusting possiblebelow 2000-2200 km

¥ Must control thrusting to achievedesired final orbitÐ Otherwise perigee raised too much

¥ Tether is rotating, so thrust directionvaries

¥ Vary average thrust direction duringperigee pass to boost apogee andkeep perigee down

TUI/MMOSTT 18

Development Issues

¥ Automated Rendezvous & CaptureÐ Time Window for Capture < 10 Seconds

Ð High Accuracy Requirements

¥ Electrodynamic Tether OperationÐ High Power & Voltage Issues

Ð Control of Tether Dynamics

¥ Traffic Control/Collision Avoidance

¥ Economic Analysis/Business PlanÐ Technology Risk Reduction Requirements

Ð Incremental Commercial Development Path

Ð Customer Acceptance

TUI/MMOSTT 19

Rendezvous

¥ Rapid Automated Rendezvous & Capture Needed

¥ Major Technology ÒTentpoleÓ

¥ Must Accomplish:Ð In advance, place payload on trajectory that will osculate with

tether tip trajectory

ÄPayload and grapple will be in proximity with zero relativevelocity for a brief time

Ð Achieve rendezvous & docking within very short time frame

Ð Minimize dynamic disturbance to tether system

TUI/MMOSTT 20

Rendezvous

TUI/MMOSTT 21

Rendezvous Method: Preparation

¥ Propagate tether orbit to obtain future tip position &velocity

¥ Propagate a Òvirtual payloadÓ backwards in time

¥ Real payload performs standard, slow rendezvouswith Òvirtual payloadÓ

¥ During approach, payload performs corrections toaccount for propagator errors

TUI/MMOSTT 22

Rendezvous: Payload Acquisition

¥ Rapid Automatic Rendezvous & Capture(AR&C) is a Key RequirementÐ Payload is in free-fall orbit

Ð Tether tip under 1-2 gees centrifugalacceleration

Ð Relative speed zero only momentarily

Ð 1 s @ 1 gee => 5 m & 10 m/s

¥ TUI Has Developed Methods for ExtendingRendezvous WindowÐ Grapple Assembly has small tether deployer

Ð At conjunction of payload and tether tip,grapple assembly deploys tether at lowtension

¥ 1 km tether gives 10s @ 2 gees

Ð Grapple and payload ÒfloatÓ in free falltogether for 5-10 seconds

Ð Payload maneuvers to dock with grapple

Ð Grapple applies brake to tether gradually tominimize tether tension excursion

Payload Capture Vehicledescends towards Payload

PCV DeploysMore Tether PCV pays out tether

and Payload maneuversto dock with grapple

PCV engagestether brake and begins to lift payload

-5

0

5

10

-5 0

Se

pa

ratio

n (

m)

5 10 15 20

Grapple Acquires Payload and PCV Halts Tether Deployment

ÆZ

Time (s)

ÆX

Payload Capture VehicleReleases Tethered Grapple

12-Second AR&C Window

0

0.2

0.4

0.6

0.8

1

0 400 800

Lo

ad

Le

vel

1200 1600 2000

TipMiddleFacility

Time (s)

TUI/MMOSTT 23

Momentum Exchange/Electrodynamic ReboostTether Technology Roadmap

GRASP

High AltitudeTether GRASP

TORQUE

LEOððððMoon/MarsTether Boost Facility

LunavatorMars-Earth Rapid

Interplanetary TetherTransport

LEO ðððð GTOTether Boost Facility

2001 2003 2005 201620132010 20352025

Demonstration:¥ Rapid AR&C

Demonstration:¥ Grapple deployment¥ AR&C w/ tether

Demonstration:¥ Spinning tether

dynamics¥ ED reboost/torque¥ Payload catch/tossOperational:¥ µSat Deployment

Operational:¥ GEO Sat deployment¥ Modular Design

Operational:¥ Lunar payload transfer¥ Boost Mars payloads to

pre-TMI orbit

Operational:¥ Transfer payloads to lunar

surface¥ Creates Round-Trip LEO-

Lunar Capability

TUI/MMOSTT 24

Potential Low-Cost Demoof Fast AR&C

¥ TUI & LLNL Planning RapidGrapple Rendezvous AndSecure Pickup (GRASP) Demo

¥ LLNL Has In Operation:Ð Air Rail and Air Table

Ð Cold Gas Jet Stabilized andPropelled Microsat Test Vehicleon Air Ball on Air Puck (5DOF)

Ð Automatic Grapple Mechanism

Ð Fully Autonomous Acquisition,Tracking, Rendezvous andCapture Sensors and Software

¥ LLNL Has Demonstrated AR&Cof Stationary Target in ~40 s

¥ TUI/LLNL Wish to DemonstrateAR&C of Moving Target in <10 s

TUI/MMOSTT 25

Potential TechnologyDevelopment Experiments

¥ High-Altitude Tether (HAT)-GRASPÐ Deploy Tether Below High-Altitude BalloonÐ Launch Payload On Small Sounding RocketÐ Payload Maneuvers + Rendezvous with Tether

¥ TORQUE - Tether Orbit Raising Qualification Experiment(s)Ð Deploy Hanging Tether

Ð AR&C w/ Hanging Tether

Ð Electrodynamic Spin-Up of Tether

Ð Controlled Toss of Payload

Ð Electrodynamic Reboost of Facility

Ð Repeated Boosting of Commercial &Scientific µSats

TUI/MMOSTT 26

Opportunities for NASATechnology Development

¥ Expand AR&C Capabilities for Rapid Capture (GRASP)

¥ High Power & High Voltage Space Systems

¥ Electrodynamic Tether Physics

¥ Debris & Traffic Control Issues

¥ Include Tether Options in HEDS & Other MissionArchitecture Studies

Modest NASA Investment in TechnologyDevelopment Will Enable Near-Term SpaceFlight Demonstration

TUI/MMOSTT 27

Plans for Second Year of Study

¥ Costing/Economic Analysis

¥ Technology Maturity AssessmentÄ Focus Technology Development Plans

¥ System Design for:Ð TORQUE Technology Demonstration

Ä Boost Station sized for µSat payloads

¥ Architectures for using tethers in a Mars transportationsystem

¥ Evaluate modular construction approaches

¥ Tether dynamics and rendezvous studies

TUI/MMOSTT 28

Acknowledgements

¥ Boeing/RSS - John Grant, Jim Martin, Harv Willenberg

¥ Boeing/Seattle - Brian Tillotson

¥ Boeing/Huntsville - Mike Bangham, Beth Fleming, Bill Klus, JohnBlumer, Ben Donohue

¥ NASA/MSFC - Kirk Sorenson

¥ Gerald Nordley

¥ Chauncey Uphoff