Skyhooks / Space Tethers
Interactive Skyhook Demo
Zoom → Launch → Capture → Transfer
Note: visualization is conceptual and not to scale. Use as a demo / investor explainer.
Concept
- A long rotating tether with a counterweight transfers momentum to vehicles. The tip moves slower than orbital speed at the bottom and faster at the top, enabling “free” velocity boost ≈ 2× tether rotation speed.
- Multiple passes per day over the same ground track support frequent “catch & release”. Use a drogue/drone line at the tip to simplify docking windows.
Why it matters
- Reduces required rocket Δv and propellant fraction by ~84–96% for interplanetary transfers when paired Earth↔Mars, per widely circulated analyses.
- Establishes an orbital energy battery: inbound payloads add momentum; outbound payloads draw it. Top-up with small electric/chemical station-keeping if needed.
- Travel time Earth↔Mars can drop from ~9 months to ~3–5 months with relay tethers and optimized windows.
Challenges & mitigations
- Atmospheric heating: minimum periapsis ~80–150 km; design tip hardware for short, high-Mach passes; use protective fairings and ablatives.
- Tip rendezvous: only ~60–90 s windows; use a 1 km guide line with an autonomous nav drone to enlarge the capture envelope.
- Debris & micrometeoroids: use a multi-strand, webbed tether for cut tolerance; continuous health monitoring with distributed fiber optics.
- Materials: high-performance UHMWPE / aramids / HM-carbon; safety factors validated via subscale on-orbit demos.
YC-phase deliverables (90 days)
- Dynamics sim: tip velocity, window geometry, thermal loads
- Lab tether: 5–10 m multi-strand sample; cut-through + fatigue tests
- Tip capture demo: drone + line rendezvous in high-speed test rig
- CubeSat concept: SRP/drag, attitude control, optical fiducials
Technical References — Space Tethers & Skyhooks
- Tethers in Space Handbook (3rd Ed.)
Comprehensive NASA/JPL reference on tether dynamics, materials, electrodynamics, and mission concepts.
- NASA Tether Transportation System Study (1998)
Analyzes mass ratios, Δv exchange, and orbital infrastructure feasibility for momentum-exchange tethers.
- Johnson et al., Dynamics and Control of Space Tethers
Foundational work on tether vibration modes, attitude stability, and feedback control algorithms.
- MDPI Aerospace: Application of Tether Technology (Special Issue)
Recent peer-reviewed studies on electrodynamic tethers, de-orbit systems, and energy harvesting.
- Li et al., Dynamics Modeling and Analysis of Looped Space Tether (2022)
Explores looped tether architectures, stress distribution, and deployment mechanics.
- High-Strength Fiber Research — Zylon, PBO, Dyneema, CNTs
Material-science data relevant to tensile strength, creep resistance, and radiation tolerance in tether strands.