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
Ongoing Tether Work Under NIAC Funding ¥
Objectives: Ð Ð Ð Ð
¥
Perform Technical & Economic Analysis of Tether Transport Systems Identify Technology Needs Develop Conceptual Design Solutions Prepare for Flight Experiments to Demonstrate Tether Transport Technology
Moon & Mars Orbiting Spinning Tether Transport (MMOSTT) Ð TUI Prime, Boeing/RSS sub Ð Ð Ð Ð
¥
Develop Design for a 2.4 km/s ÆV LEOðGTO Tether Boost Facility Develop & Simulate Methods for Tether-Payload Rendezvous Identify Near-Term Commercial and Scientific Applications 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 Boost Facility with a Mach 10-12 Hypersonic Airplane
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Summary of Advantages ¥ Tether Boost Facilities Can Provide a Fully-Reusable In-Space Propulsion Architecture Ð LEO ⇔ MEO/GTO Ð LEO ⇔ Lunar Surface Ð LEO ⇔ 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 days to Mars
¥ Reusable Infrastructure + Low Consumables Ä Lower Cost TUI/MMOSTT 3
Cislunar Tether Transport System ¥ ¥
ó Lunar Developed Orbital Architecture for Round Trip LEOó Surface Transport Whole System Mass < 27x Payload Mass Ð
¥ ¥
LEO Tether Boost Facility Mass = 10x Payload Mass, Lunar Tether Facility = 17x Payload
13 Payloads/Year Incremental Commercial Development Path Tether Boost Facility in Elliptical Earth Orbit
MinimumEnergy Lunar Transfer Orbit
Initial Payload Orbit
Lunavator in Low-Lunar Polar Orbit
Rapid Earth-Mars Transport ¥ ¥ ¥
Reusable Architecture for Round Trip Earth ó Mars Transport Rapid Transfer Times (90-130 days) Extended Launch Windows
¥
Currently Evaluating Architectures
146 Day Transfer 2.0 km/s tether tip speed
Ð All Tether Ð Tether/Chemical
Earth’s gravitational sphere of influence
Approach Year 2001 2003 2005 2007 2009 2011 2013 2016 2018
Window (days) Open Close 03/18/01 05/07/01 50 04/27/03 07/22/03 86 07/27/05 09/08/05 43 6 Oct comes closest 10 Nov comes closest 12/06/11 12/21/11 15 12/30/13 02/08/14 40 02/02/16 04/06/16 64 03/25/18 06/24/18 91
116 Day Transfer 2.5 km/s tether tip speed Window (days) Open Close 02/25/01 05/18/01 82 05/04/03 08/03/03 91 07/31/05 09/20/05 51 10/06/07 10/24/07 18 20 Nov comes closest 12/18/11 01/02/12 15 01/11/13 02/16/13 36 02/14/16 04/18/16 64 04/03/18 07/06/18 94
Sol
Mars’gravitational sphere of influence TUI/MMOSTT 5
Incremental Development Path 1. TORQUEª Experiment Ð Demonstrate Momentum-Exchange & Electrodynamic Reboost Ð Experiment Becomes Operational Facility for µSat Deployment
2. LEO ó GTO Tether Boost Facility Ð Initial Capability: 2,500 kg to GTO once per month Ð Modular Design: add additional components ð 5,000 kg, 7,500 kgÉ
3. LEO ó Lunar Tether Transport System Ð LEO ó GTO Facility Can also Send Payloads to Moon Ð Add Lunavator to Enable Round-Trip Transport to Lunar Surface
4. LEO ó Mars Tether Transport Ð 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 of Later Stages
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ðGTO Tether Boost Facility LEOð ¥ ¥
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 Launch Tether Mass: Grapple Assembly: Control Station Mass: Total Launch Mass: + Delta-IV Upper Stage for Ballast:
¥ ¥ ¥
8,275 kg 650 kg 11,500 kg 20,500 kg 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
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ðGTO Boost Facility LEOð ¥
TetherSim Numerical Simulation (10x real speed) ª
Ð Tether Dynamics, Orbital Mechanics
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ðGTO Boost Facility LEOð System Definition Task ¥ TUI & Boeing have developed System Requirements Document for Tether Boost Facility ¥ System Concept Definition Ð Identify key technologies Ð Mass and power budgets
¥ Technology Readiness Level Evaluation
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Tether Boost Facility Control Station ¥ ¥ ¥ ¥
Solar Arrays Battery/Flywheel Power Storage Command & Control Tether Deployer
Total Mass:ÊÊÊÊ 24,000 kg Payload Mass: 2,500 kg
Tether (not shown to scale) ¥ ¥ ¥ ¥
Hoytether for Survivability Spectra 2000 75-100 km Long Conducting Portion for Electrodynamic Thrusting
Payload Accommodation Assembly (PAA) ¥ Maneuvering & Rendezvous Capability ¥ Payload Apogee Kick Capability TUI/MMOSTT 10
Grapple Assembly ¥ Power, Guidance ¥ Grapple Mechanism ¥ Small Tether Deployer
Payload
Control Station Upper Stage For Ballast
Solar Panels
Radiator Panel
Deployer Reel Deployer Boom
Electron Emitter Power Module
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Hoytether
Modular Design ¥ Design Components for Modular Assembly ¥ First Launch Gives 2.5 Ton ð 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 Supplies Ð Run Tethers In Parallel ¥ Get 5 Ton ð GTO Capability ¥ Add Additional Components to Increase Payload Capability
Total Mass:ÊÊÊÊ 48,000 kg Payload Mass: 5,000 kg
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Grapple Assembly TETHER BOOM
CONFIGURATION DRIVERS ¥ Capture Options ¥ System Rotation ¥ Loads
SIZING PARAMETERS ¥ 1380 Watts ¥ 15.61 Square Meter Arrays ¥ 1.25 Meter Dia Capture Ring ¥ 50 Kg Batteries (Ni-H2)
Tracking Sensors
2X Solar Array (can be stowed during Rendezvous & capture)
Thruster
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7.5 METERS
Grapple Mechanism
Payload Accommodation Assembly Configuration Drivers ¥ Mimic Conventional Upper Stage Interfaces To Payload And Booster ¥ Track Grapple And Make Rendezvous Corrections ¥ Provide Circularization ÆV
Payload with PAA
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¥ ¥ ¥ ¥ ¥
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
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
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Initial Orbit
Operational Orbit
Tether Facility Reboost ¥
Use Electrodynamic Propulsion Near Perigee to Reboost Orbit Ð Collect electrons from ionosphere at one end of tether & emit electrons at other end of tether Ð Use power from batteries to push curent along tether Ð Current interacts with geomagnetic field to give JxB force Ð Vary current to generate net thrust
¥
To achieve Reboost in 30 days: Ð Solar Panel Power: Ð Power To ED Tether:
¥
150 kW 450 kW
Issues: Ð High Power, High Voltage (20 kV)
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Reboost Tuning ¥ ¥
Electrodynamic thrusting possible below 2000-2200 km Must control thrusting to achieve desired final orbit Ð Otherwise perigee raised too much
¥ ¥
Tether is rotating, so thrust direction varies Vary average thrust direction during perigee pass to boost apogee and keep perigee down
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Development Issues ¥ Automated Rendezvous & Capture Ð Time Window for Capture < 10 Seconds Ð High Accuracy Requirements
¥ Electrodynamic Tether Operation Ð High Power & Voltage Issues Ð Control of Tether Dynamics
¥ Traffic Control/Collision Avoidance ¥ Economic Analysis/Business Plan Ð Technology Risk Reduction Requirements Ð Incremental Commercial Development Path Ð Customer Acceptance TUI/MMOSTT 18
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 relative velocity for a brief time Ð Achieve rendezvous & docking within very short time frame Ð Minimize dynamic disturbance to tether system
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Rendezvous
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Rendezvous Method: Preparation ¥ Propagate tether orbit to obtain future tip position & velocity ¥ Propagate a Òvirtual payloadÓ backwards in time ¥ Real payload performs standard, slow rendezvous with Òvirtual payloadÓ ¥ During approach, payload performs corrections to account for propagator errors
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Rendezvous: Payload Acquisition ¥ Rapid Automatic Rendezvous & Capture (AR&C) is a Key Requirement
Ð Grapple Assembly has small tether deployer Ð At conjunction of payload and tether tip, grapple assembly deploys tether at low tension ¥ 1 km tether gives 10s @ 2 gees Ð Grapple and payload ÒfloatÓ in free fall together for 5-10 seconds Ð Payload maneuvers to dock with grapple Ð Grapple applies brake to tether gradually to minimize tether tension excursion TUI/MMOSTT 22
PCV pays out tether and Payload maneuvers to dock with grapple
PCV engages tether brake and begins to lift payload
10 ÆZ Separation (m)
¥ TUI Has Developed Methods for Extending Rendezvous Window
PCV Deploys More Tether
Payload Capture Vehicle descends towards Payload
Payload Capture Vehicle Releases Tethered Grapple
5
0 ÆX -5
-5
12-Second AR&C Window
0
5
10
Grapple Acquires Payload and PCV Halts Tether Deployment
15
20
Time (s) 1 Tip Middle Facility
0.8 Load Level
Ð Payload is in free-fall orbit Ð Tether tip under 1-2 gees centrifugal acceleration Ð Relative speed zero only momentarily Ð 1 s @ 1 gee => 5 m & 10 m/s
0.6
0.4
0.2
0 0
400
800
1200 Time (s)
1600
2000
Momentum Exchange/Electrodynamic Reboost Tether Technology Roadmap Lunavator
Mars-Earth Rapid Interplanetary Tether Transport
ðMoon/Mars LEOð Tether Boost Facility LEO ð GTO Tether Boost Facility
Operational: ¥ Transfer pay loads to lunar surface ¥ Creates Round-Trip LEOLunar Capability
TORQUE High Altitude Tether GRASP Operational: ¥ Lunar pay load transfer ¥ Boost Mars payloads to pre-TMI orbit Operational: ¥ GEO Sat deployment ¥ Modular Design
GRASP Demonstration: ¥ Spinning tether dynamics ¥ ED reboost/torque ¥ Payload catch/toss Operational: ¥ µSat Deployment
Demonstration: ¥ Rapid AR&C
2001
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Demonstration: ¥ Grapple deployment ¥ AR&C w/ tether
2003
2005
2010
2013
2016
2025
2035
Potential Low-Cost Demo of Fast AR&C ¥
¥
TUI & LLNL Planning Rapid Grapple Rendezvous And Secure Pickup (GRASP) Demo LLNL Has In Operation: Ð Air Rail and Air Table Ð Cold Gas Jet Stabilized and Propelled Microsat Test Vehicle on Air Ball on Air Puck (5DOF) Ð Automatic Grapple Mechanism Ð Fully Autonomous Acquisition, Tracking, Rendezvous and Capture Sensors and Software
¥ ¥
LLNL Has Demonstrated AR&C of Stationary Target in ~40 s TUI/LLNL Wish to Demonstrate AR&C of Moving Target in <10 s
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Potential Technology Development Experiments ¥ High-Altitude Tether (HAT)-GRASP Ð Deploy Tether Below High-Altitude Balloon Ð Launch Payload On Small Sounding Rocket Ð Payload Maneuvers + Rendezvous with Tether
¥ TORQUE - Tether Orbit Raising Qualification Experiment(s) Ð Ð Ð Ð Ð Ð
Deploy Hanging Tether AR&C w/ Hanging Tether Electrodynamic Spin-Up of Tether Controlled Toss of Payload Electrodynamic Reboost of Facility Repeated Boosting of Commercial & Scientific µSats
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Opportunities for NASA Technology 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 Mission Architecture Studies
Modest NASA Investment in Technology Development Will Enable Near-Term Space Flight Demonstration TUI/MMOSTT 26
Plans for Second Year of Study ¥ Costing/Economic Analysis ¥ Technology Maturity Assessment Ä 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 transportation system ¥ Evaluate modular construction approaches ¥ Tether dynamics and rendezvous studies
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Acknowledgements ¥ ¥ ¥ ¥ ¥ ¥
Boeing/RSS - John Grant, Jim Martin, Harv Willenberg Boeing/Seattle - Brian Tillotson Boeing/Huntsville - Mike Bangham, Beth Fleming, Bill Klus, John Blumer, Ben Donohue NASA/MSFC - Kirk Sorenson Gerald Nordley Chauncey Uphoff
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