# Inspiration from GROK

Reason for using GenAI at this point was my main concern with a type of propulsion. I was thinking about a type of jet (as it is very safe) but I'm not a water mechnical engineer so I asked for inspirstion. I therefore gave Grok my latest ideas from week 2 and simply asked it

```
    I'm looking for a propulsion type
```

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As a fellow educator with a software engineering background, I appreciate how you're approaching this FabAcademy project by starting with user scenarios and non-functionals—it's a solid systems thinking mindset that aligns well with iterative design in a fabrication context. Since you're targeting a small, throwable, autonomous surface device like UWO, propulsion is key to balancing agility (for game modes), efficiency (for battery life in guidance/stealth), safety (soft impact, no sharp parts), and quiet operation (stealth/wildlife). Based on your requirements, I'll break down suitable propulsion types, drawing from common approaches in small autonomous surface vehicles (ASVs) and diver aids. I'll focus on options that are feasible to prototype in FabAcademy using accessible tools like 3D printing, laser cutting, and off-the-shelf electronics (e.g., motors from hobby suppliers).

### Key Considerations for Your Propulsion Choice
Before diving into types, here's a quick tip framework to evaluate them against your specs:
- **Safety**: Prioritize enclosed systems to avoid exposed blades that could cut skin or wildlife. Use soft materials (e.g., silicone shrouds) for impact zones.
- **Quietness**: Aim for <50 dB in stealth mode—electric systems with low RPM or ducting help. Test with a decibel app during prototypes.
- **Efficiency**: Calculate power draw; your energy needs (30 min high-speed game vs. 4h low-speed stealth) suggest a 200-500Wh battery pack, possibly with solar top-up for self-sufficiency. Use efficient motors to hit those runtimes.
- **Size/Throwable**: Keep it compact (e.g., <30cm diameter, <2kg) like a disc. Propulsion should integrate into a hydrodynamic hull.
- **Navigation Integration**: Pair with your awareness subsystem (e.g., via Arduino/ESP32 for control). Use PWM for speed/direction.
- **Fabrication Tips**: Start with CAD (e.g., Fusion 360) for hull/prop housing. 3D print prototypes in PETG for water resistance. Waterproof electronics with potting compound.
- **Testing**: Iterate in a pool—measure speed (aim 0.5-2 m/s), noise, and battery drain. Simulate geo-fencing with GPS modules like u-blox.

### Recommended Propulsion Types
I've compared viable options in a table below, based on their fit for UWO's modes (e.g., random evasion in games, slow stealth approaches). These are electric-driven for cleanliness (no pollution) and quietness, avoiding combustion engines. Water jets and ducted props stand out for safety and stealth.

| Propulsion Type | Description | Pros for UWO | Cons for UWO | Efficiency & Runtime Fit | Fabrication Feasibility | Examples/Implementation Tips |
|-----------------|-------------|--------------|--------------|---------------------------|--------------------------|------------------------------|
| Water Jet (Pump Jet) | Uses a small electric pump (e.g., bilge pump) to suck in water and expel it through a nozzle for thrust. Vectored jets allow direction changes via servo-steered nozzles. | - Safe: No exposed blades, soft impact.<br>- Quiet: Low vibration/noise in stealth (use shrouded nozzles).<br>- Agile: Good for random movements in games or following swimmers.<br>- Minimal above-water profile: Submerged intake. | - Less efficient at very low speeds (e.g., stealth creep).<br>- Needs intake filtering to avoid debris clogs in open water. | High: Low power draw at cruise (e.g., 10-20W for 1 m/s). Supports 2-4h modes; add solar panels for recharge.   | High: Use off-the-shelf 12V bilge pumps (e.g., Rule 400GPH, ~$20). 3D print nozzles/housing. Control with MOSFET for variable speed. | Blue Robotics-inspired jets for ASVs. For UWO, mount 2-3 jets for omnidirectional control (e.g., like a holonomic robot). Test vectoring with cheap servos. |
| Ducted Propeller/Thruster | Enclosed propeller in a tube (duct) driven by a brushless motor. Similar to underwater drone thrusters. | - Safe: Duct guards blades, low shock risk (seal motor well).<br>- Quiet: Ducting reduces noise by 10-20 dB.<br>- Versatile: Reversible for forward/backward; multiple units for turning.<br>- Self-righting aid: Thrust can flip it upright. | - Slightly noisier than jets at high speed (game mode).<br>- Higher drag if not streamlined. | Medium-High: Efficient at variable speeds (e.g., 5-15W). Hits your runtimes with a 3S LiPo battery. Optimize with larger, slower-spinning props for quiet.   | Medium-High: Buy Blue Robotics T100/T200 thrusters (~$100 each) or DIY with hobby brushless motors (e.g., 2212 KV1400) and 3D-printed ducts/props. Waterproof with epoxy. | Used in reef-mapping USVs. For UWO, use 2-4 thrusters in a disc hull (like a quadcopter layout but underwater). Integrate with IMU for stability. |
| Biomimetic Fin/Oscillating | Flexible fin (like a fish tail) oscillated by a servo or linear actuator. | - Very Quiet: Mimics natural movement, ideal for wildlife/stealth.<br>- Safe: Soft silicone fin, no hard parts.<br>- Low Profile: Fin below water, easy accessory attach (e.g., duck disguise). | - Less agile for fast games (max speed ~0.5 m/s).<br>- Complex control for random paths. | High: Low power (5-10W), excellent for long stealth (4h+).   | Medium: Laser-cut fin from silicone sheet, attach to servo. Simple code for oscillation patterns. | Robotic fish prototypes. Start with a single caudal fin for propulsion; add side fins for steering. Great for your software skills—program wave patterns in Python/Arduino. |
| RIM-Driven Propeller | Propeller blades on a ring motor (no central shaft). | - Compact/Throwable: Fits in small disc form.<br>- Quiet: Reduced cavitation noise.<br>- Safe: Can enclose fully. | - Expensive/harder to source.<br>- Less common for variable speed. | Medium: Similar to ducted, but higher efficiency at constant speeds. | Low-Medium: Advanced; 3D print ring with embedded coils if ambitious, or adapt hobby parts. | MIT micro-AUV designs. Best as a stretch goal if basic props work.  |

### My Top Recommendation
Go with **water jet propulsion** as your baseline—it's the sweet spot for safety, quietness, and agility in UWO's mixed modes. It's inspired by recreational diver propulsion vehicles (DPVs) but scaled down for surface use.  In game mode, vectored jets enable quick dodges; in stealth, run at low flow for silence. Pair it with your navigation subsystem: Use ultrasonic sensors for swimmer detection (e.g., HC-SR04 waterproofed) and GPS (e.g., NEO-6M) for paths. For energy, integrate a flexible solar panel on top (disguised as a duck back) to trickle-charge during floats.

### Next Steps & Tips
1. **Prototype Quickly**: Sketch in paper, then CAD a simple disc hull with jet mounts. Test a single jet in a bucket for thrust/noise.
2. **Software Angle**: Leverage your expertise—write modular code for modes (e.g., PID for distance keeping). Simulate in Python (use libraries like numpy for path planning) before hardware.
3. **Safety Iteration**: Add bump sensors (e.g., soft switches) to stop on impact. Ensure IP67 sealing for electrics.
4. **Battery Math**: For 30 min game at 50W draw, need ~25Wh capacity—feasible with 18650 cells. Monitor with a BMS module.
5. **FabAcademy Alignment**: Check the schedule (e.g., electronics production week for motor drivers, 3D printing for housings). Document failures—great for your final presentation.

If this sparks ideas or you need specifics (e.g., code snippets for control, part lists), share more details like your budget or preferred tools!