Seastead Specs Summary: 40x16 ft living area, ~36,000 lbs (16,330 kg) displacement, high-drag platform-like hull (tiny oil rig shape), primary speed 0.5-1 mph with solar-powered thrusters.
Assumptions: Seawater density ρ=1025 kg/m³. Drag model F_d = 0.5 ρ v² A C_d (C_d ~1.5-2.5 for bluff bodies/anchors). Seastead frontal area ~20-30 m² (est. for platform), effective C_d ~2.0 at low speeds. Power/thrust converted to force × velocity.
2 thrusters per side (4 total, 2.5m dia. low-speed submersible mixers). Differential thrust requires ≥1 working thruster per side for steering/control.
Setup: 2x 10m dia. sea anchors, long ropes via dinghy pulley system. Alternate pulling (one at a time) in calm conditions. Dinghy energy ignored per request.
Sea anchor drag F_d ≈ 0.5 ρ v² A C_d (A=78.5 m² for 10m dia., C_d=2.0 for parachute). Power P = F_d × v = 2000W → v ≈ (P / (0.5 ρ C_d A))^{1/3} ≈ 0.3 m/s (0.67 mph).
| Sea Anchor Size | Est. Drag Area (m²) | Est. Speed @2000W | Notes |
|---|---|---|---|
| 10m dia. | 78.5 | 0.67 mph | Huge; efficient but slow deploy. |
| 5m dia. (recommended) | 19.6 | 1.1 mph | More practical; balance size/speed. |
| 7m dia. | 38.5 | 0.85 mph | Good compromise. |
Cost & Weight (10m dia.): Custom fabric parafoil sea anchor ~$5,000-10,000 USD (scaled from yacht models like Ace/Sailrite; Jordan drogue equiv. $2k-4k smaller). Weight: 50-100 kg dry (nylon/PU fabric + stainless bridles/shackle). Buoyant collar optional (+20kg, $500).
Efficiency: Sea anchor drags ~10-20x water mass (low slip). Real speed 70-90% of ideal due to waves/oscillation.
Bottom anchors (e.g., plow/fluke) dragged on seabed. Winch pulls seastead forward.
Seabed drag ~2-5x hydrodynamic (friction/holding). F_hold ≈ 1000-3000N for 50-100kg anchors at low v. @2000W → 0.8-1.5 mph (faster than sea anchors due to lower slip, but depth-limited & seabed damage risk).
| Anchor Type | Est. Holding (low v) | Speed @2000W |
|---|---|---|
| 50kg Plow | 1500N | 1.2 mph |
| 100kg Fluke | 3000N | 0.9 mph (slower if stalls) |
Pros/Cons: Faster in shallows (<50ft); cheap ($500-2k/anchor). Risk: snags, anchor loss.
Normal: 1x motor for shore runs. Emergency: 3x (681 lbs / 3030N total thrust), powered via seastead cable.
Seastead drag @1 mph ~2000-4000N (high C_d). Thrust sustains 1.0-1.5 mph (thrust-to-weight 2%; low-speed regime).
Stack of 20 kites (6ft wide x 2ft = 1.1 m² each; total 22 m²). 2-string control for figure-8 (apparent wind boost).
| Angle | Est. Force | Est. Speed | Kites for 2 mph |
|---|---|---|---|
| Direct Downwind | 1-2 kN | 0.5-0.8 mph | 35-50 kites |
| 30° Off Downwind | 2-4 kN (figure-8) | 1.5-2.5 mph | 12-18 kites |
Force = 0.5 ρ_air (20mph=9m/s) × A × C_L (1.0-1.5). Apparent wind ×2-3 off-angle. Drag-matched speed.
Notes: >2 mph possible off-angle. Scale to 15 kites for ~2 mph @30°.
Towing: Friend's seastead (similar specs) → 0.3-0.6 mph (double drag).
Power Bridge: Rope + cable → double solar/batteries → thrusters @2x power → 1.2-1.8 mph.
1-2 thrusters (same side): Hold bow at 20-45° to wind. Net drift downwind + lateral → 0.2-0.7 mph toward rescue/port.
Solar sustains; no extra hardware. Test in sims for angles.
| Method | Est. Speed | Power Source | Feasibility |
|---|---|---|---|
| Thruster Redundancy | 0.5-1 mph | Solar | High |
| Sea Anchor Kedge | 0.7-1.1 mph | 2000W Winch | Medium |
| Bottom Anchor Kedge | 0.8-1.5 mph | 2000W Winch | Medium (shallow) |
| Dinghy Tow | 1.0-1.5 mph | Batteries | High |
| Kites (30°) | 1.5-2.5 mph | Wind | Medium-High |
| Peer Tow/Power | 0.3-1.8 mph | Solar/Batteries | High (w/ help) |
| Single Thruster + Wind | 0.2-0.7 mph | Solar/Wind | High |
Recommendations: Prioritize dinghy tow & kites (fastest/reliable). Test prototypes. All viable for emergencies to reach safety.