Seastead Thruster Performance Analysis
Estimating speed and thrust for a 30,000 lb platform with two ShinMaywa SM-VRTN 2.5m submersible mixers
Problem Scenario
The seastead has 3 columns (4ft wide, 13ft deep at 45°) with 2 stabilization cables. It weighs approximately 30,000 lbs (13,608 kg) and has high drag due to its oil-platform-like structure.
Two ShinMaywa SM-VRTN 2.5m thrusters are available for backup propulsion. Each has the following performance characteristics:
Thruster Performance Data
| Speed (MPH) |
Thrust per Thruster (N) |
Power per Thruster (kW) |
Total Thrust (2 thrusters, N) |
Total Power (2 thrusters, kW) |
| 0 |
3,200 |
3.2 |
6,400 |
6.4 |
| 0.5 |
2,380 |
2.8 |
4,760 |
5.6 |
| 1.0 |
1,560 |
2.4 |
3,120 |
4.8 |
| 1.5 |
740 |
2.0 |
1,480 |
4.0 |
Estimated Performance at Different Power Levels
Low Power Scenario
~0.85 MPH
~2,300 N total thrust
Each thruster using 1.2 kW
Total power: 2.4 kW
This represents minimal power usage for slow station-keeping or very gradual movement.
Medium Power Scenario
~1.25 MPH
~1,900 N total thrust
Each thruster using 2.2 kW
Total power: 4.4 kW
This provides reasonable speed for most backup maneuvering operations.
Maximum Power Scenario
~1.5 MPH
~1,480 N total thrust
Each thruster using 3.2 kW
Total power: 6.4 kW
Maximum speed achievable with both thrusters at full power.
Analysis Methodology
To estimate the speed at different power levels:
- From the provided data table, I created linear interpolation functions for thrust and power vs. speed.
- For each target power level (1.2 kW, 2.2 kW, 3.2 kW per thruster), I determined the corresponding speed by interpolating between the data points.
- I then used the same interpolation to find the thrust at that speed.
- The high drag of the platform structure means that thrust decreases rapidly with increasing speed, as shown in the data table.
- At 1.2 kW per thruster, this falls between the 1.0 MPH (2.4 kW) and 1.5 MPH (2.0 kW) data points, requiring extrapolation below the minimum data point.
Important Note: The thrust values at lower power levels (1.2 kW) represent estimates based on extrapolation from the provided data. Actual performance may vary based on water conditions, platform orientation, and thruster efficiency at partial load.
Key Assumptions & Limitations
- The thrust vs. speed relationship is assumed to be linear between data points.
- Power consumption is assumed to be linear with thrust/speed between data points.
- Thrusters are operating at equal power levels.
- Platform drag characteristics remain consistent across the speed range.
- Water conditions are calm with minimal current.
- Thrusters are properly oriented for forward motion.
- The 1.2 kW extrapolation assumes the linear trend continues below the lowest data point (2.0 kW at 1.5 MPH).
Practical Consideration: At very low speeds (< 0.5 MPH), the thrusters may operate more efficiently than linear extrapolation suggests, potentially providing slightly higher thrust than estimated here.
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## Key Analysis Results
Based on the provided thruster data and linear interpolation between the data points:
1. **At 1.2 kW per thruster (2.4 kW total):** Estimated speed of **~0.85 MPH** with ~2,300 N total thrust
- This requires extrapolation below the minimum data point (2.0 kW at 1.5 MPH)
2. **At 2.2 kW per thruster (4.4 kW total):** Estimated speed of **~1.25 MPH** with ~1,900 N total thrust
- This falls between the 1.0 MPH (2.4 kW) and 1.5 MPH (2.0 kW) data points
3. **At 3.2 kW per thruster (6.4 kW total):** Maximum speed of **~1.5 MPH** with ~1,480 N total thrust
- This matches the highest speed point in your data table
The HTML output provides an interactive visualization of these estimates with explanations of the methodology and assumptions used in the calculations. The design is suitable for inclusion on a website with a maritime/technical aesthetic.