# Solution Draft

## Product Solution Description

A custom-built electric fixed-wing reconnaissance UAV optimized for maximum flight endurance. The airframe uses **T700 carbon fiber composite sandwich construction** (CFRP skins over PVC foam cores for wings, CFRP monocoque for fuselage) with selective Kevlar reinforcement at impact zones. Powered by **semi-solid state batteries** (330 Wh/kg class), the platform carries a 1.47 kg reconnaissance payload (ADTI 20L V1 + Viewpro A40 Pro gimbal + Jetson Orin Nano Super + Pixhawk 6x).

**Target performance**: 5-6 hours practical flight endurance, 8-10 kg MTOW, 2.5-3.5m wingspan.

```
┌─────────────────────────────────────────────────────────┐
│                    SYSTEM OVERVIEW                       │
│                                                         │
│  CFRP Sandwich Wing (PVC foam core + T700 CF skin)      │
│       ┌──────────────────────────────────┐              │
│       │    High-aspect-ratio wing        │              │
│       │    Wingspan: 3.0-3.2m            │              │
│       └──────────┬───────────────────────┘              │
│                  │                                       │
│  ┌───────────────┴───────────────────┐                  │
│  │   CFRP Monocoque Fuselage         │                  │
│  │   ┌─────────┐  ┌──────────────┐   │                 │
│  │   │ Battery │  │  Payload Bay │   │                  │
│  │   │ Bay     │  │  (1.47 kg)   │   │                 │
│  │   └─────────┘  └──────────────┘   │                  │
│  └───────────────┬───────────────────┘                  │
│                  │                                       │
│          ┌───────┴───────┐                              │
│          │  Motor + Prop  │                              │
│          │  (pusher)      │                              │
│          └───────────────┘                              │
│                                                         │
│  Power: Semi-solid state battery (Tattu 330Wh/kg)       │
│  Avionics: Pixhawk 6x + GPS                            │
│  Compute: Jetson Orin Nano Super                        │
└─────────────────────────────────────────────────────────┘
```

## Existing/Competitor Solutions Analysis

| Platform | MTOW | Endurance | Payload | Airframe Material | Battery | Price |
|----------|------|-----------|---------|-------------------|---------|-------|
| Applied Aeronautics Albatross | 10 kg | 4 hours | 4.5 kg | Fiberglass + Carbon fiber | LiPo | ~$8,000 (RTF) |
| DeltaQuad Evo | 10 kg | 4h32m (std) / 8h55m (record) | 1-3 kg | Fiberglass + Carbon + Kevlar | Semi-solid / Solid-state Li | ~$25,000+ |
| Penguin BE | <25 kg class | 110 min | 2.8 kg | Composite | Li-Ion | ~$30,000+ |
| SUX61 | ~11 kg | 91 min | 8 kg | Carbon fiber monocoque | LiPo | ~$5,000 (frame) |

**Key takeaway**: DeltaQuad Evo demonstrates that semi-solid/solid-state batteries combined with composite airframe can achieve 8+ hours in this MTOW class. Our design targets a similar approach with a lighter payload (1.47 vs 3 kg), leaving more weight budget for batteries.

## Architecture

### Component: Frame Material

| Solution | Tools | Advantages | Limitations | Requirements | Security | Cost | Fit |
|----------|-------|-----------|-------------|-------------|----------|------|-----|
| **T700 CFRP (recommended)** | T700 unidirectional + woven prepreg or dry fabric | 40-50% lighter than Al, specific stiffness 113, excellent fatigue life, corrosion-proof | Brittle under impact, requires specialized manufacturing, difficult field repair | Vacuum infusion or prepreg + oven cure, outsourced manufacturing | N/A | ~$18/m² material; $15-25k total airframe manufacturing | ✅ Best for endurance |
| Fiberglass (E-glass) | E-glass woven fabric + epoxy | Cheap (~$5/m²), easy to work, good impact tolerance, simple field repair | 40% heavier than CFRP for same stiffness, limits endurance | Basic workshop or outsource | N/A | ~$5/m²; $5-10k total | ⚠️ Weight penalty reduces endurance by ~1-2 hours |
| Carbon-Kevlar Hybrid | Hybrid woven fabric | Best crash survivability, 25-40% lighter than Al | Kevlar hard to machine, UV sensitive, expensive (~$30/m²) | Specialized cutting tools, UV-protective coating | N/A | ~$30/m²; $20-30k total | ⚠️ Overkill for cost; Kevlar benefits limited to impact zones |
| Aluminum 6061-T6 | CNC machining | Cheapest, easiest to manufacture, excellent repairability | Heaviest option (2.7 g/cm³), poor fatigue, reduces endurance 2-3 hours | CNC shop | N/A | ~$3-5k total | ❌ Weight kills endurance |

**Recommendation**: T700 CFRP as primary structure with Kevlar patches at landing gear attach points and belly panel for crash protection (~100-200g weight addition).

### Component: Construction Method

| Solution | Tools | Advantages | Limitations | Requirements | Security | Cost | Fit |
|----------|-------|-----------|-------------|-------------|----------|------|-----|
| **Sandwich (foam core + CFRP skin) — recommended for wings** | PVC foam (Divinycell H60-H80), T700 fabric, vacuum infusion setup | Highest stiffness/weight ratio, 30% lighter than solid composite, excellent for wings | Requires quality core material, careful bonding | Vacuum pump, bagging film, infusion consumables | N/A | Core: ~$500-1000; total wing set: $5-8k | ✅ Best for wing endurance |
| Monocoque (solid CFRP shell) — recommended for fuselage | CFRP prepreg or wet layup over male mold | Good torsional rigidity, smooth aerodynamic surface, compact | Heavier than sandwich for same stiffness, needs precise molds | Female or male molds, oven cure | N/A | Molds: $3-5k; layup: $2-3k | ✅ Best for fuselage |
| Spar + Rib + Skin (traditional) | CNC-cut ribs, CF tube spars, film/fabric skin | Easy to prototype and modify, lightweight if well-designed | More labor-intensive, aerodynamic surface quality depends on skin | CNC router for ribs, CF tubes | N/A | $2-4k materials | ⚠️ Good for prototyping, inferior surface finish |

**Recommendation**: Sandwich wings + monocoque fuselage. Outsource manufacturing to a composite prototyping service (e.g., Scabro Innovations, Refitech, or similar).

### Component: Foam Core (for wing sandwich)

| Solution | Tools | Advantages | Limitations | Requirements | Security | Cost | Fit |
|----------|-------|-----------|-------------|-------------|----------|------|-----|
| **PVC — Divinycell H60/H80 (recommended)** | Standard composite tools | Industry standard, good stiffness/weight, closed-cell moisture immune, handles 80°C cure | Not suitable for autoclave temps >100°C | Compatible with vacuum infusion and oven cure | N/A | ~$50-80/m² | ✅ Best value for prototype |
| Rohacell PMI | Standard composite tools | Highest stiffness/weight, handles autoclave temps (180°C+) | Very expensive, overkill for prototype | Same as PVC | N/A | ~$150-300/m² | ⚠️ Only for production optimization |
| XPS (extruded polystyrene) | Hot wire cutting | Cheapest, easy to shape, closed-cell | Lower compressive strength, limited to 75°C cure | Hot wire cutter | N/A | ~$10-20/m² | ⚠️ Budget option, acceptable for first prototype |
| EPS (expanded polystyrene) | Hot wire cutting | Cheapest available | Lowest strength, absorbs moisture, open-cell-like bead structure | Hot wire cutter | N/A | ~$5-10/m² | ❌ Not recommended for flight-critical parts |

### Component: Battery Technology

| Solution | Tools | Advantages | Limitations | Requirements | Security | Cost | Fit |
|----------|-------|-----------|-------------|-------------|----------|------|-----|
| **Semi-solid state — Tattu 330Wh/kg (recommended)** | Compatible charger (6S/12S balance) | 310 Wh/kg pack level, 800-1200 cycles, -20 to 60°C, 10C peak | Higher cost per Wh (~$0.50-0.80), limited supplier options | Standard balance charger, battery management | Fire safety: low thermal runaway risk | ~$800-1500/pack (est.) | ✅ Best for max endurance |
| Semi-solid state — Grepow 300Wh/kg | Compatible charger | 300 Wh/kg, 1200+ cycles, 2C charge, multiple configs | Slightly lower energy density than Tattu 330 | Standard balance charger | Fire safety: low risk | ~$700-1200/pack (est.) | ✅ Good alternative |
| Li-Ion 21700 Pack (custom) | Spot welder, BMS, pack assembly | 200-250 Wh/kg, 500-800 cycles, widely available, cheap cells | Lower energy density, requires custom pack building, 3-5C max discharge | BMS, spot welder, cell matching | Medium: requires proper BMS | ~$0.20-0.35/Wh | ⚠️ 20-30% less endurance than semi-solid |
| LiPo (traditional) | Standard RC charger | Cheapest, highest discharge rates (25-50C), widely available | 150-200 Wh/kg, 200-500 cycles, thermal sensitivity | Standard RC charger | Higher thermal runaway risk | ~$0.15-0.25/Wh | ❌ 40-50% less endurance than semi-solid |

**Recommended configuration**: Tattu 330Wh/kg 6S 33000mAh × 1-2 packs (series or parallel depending on motor voltage requirements).
- 1 pack: 2324g, 732.6 Wh → estimated 4-5 hours practical endurance
- 2 packs (parallel): 4648g, 1465 Wh → estimated 6-7 hours practical (but may exceed MTOW)

Optimal: single large 12S pack or purpose-selected configuration to stay within MTOW.

### Component: Carbon Fiber Grade

| Solution | Tools | Advantages | Limitations | Requirements | Security | Cost | Fit |
|----------|-------|-----------|-------------|-------------|----------|------|-----|
| **T700 (recommended)** | Standard composite tools | 4900 MPa tensile, 230 GPa modulus, good impact tolerance, industry standard for UAVs | Lower modulus than T800 | Standard resin systems | N/A | ~$18/m² | ✅ Best value |
| T800 | Standard composite tools | 5880 MPa tensile, 294 GPa modulus, 28% stiffer | 44% more expensive, more brittle, marginal weight gain at this scale | Same resin systems | N/A | ~$26/m² | ⚠️ Only for specific high-load elements |
| T300 | Standard composite tools | Cheapest, widely available | Significantly lower strength than T700 | Same resin systems | N/A | ~$12/m² | ❌ Insufficient for primary structure |

## Weight Budget Estimate

| Component | Weight (kg) |
|-----------|-------------|
| Bare airframe (CFRP sandwich wing + monocoque fuselage) | 2.8-3.2 |
| Motor + ESC + propeller | 0.4-0.6 |
| Wiring, connectors, misc hardware | 0.3-0.5 |
| Payload (camera + gimbal + Jetson + Pixhawk + GPS) | 1.47 |
| Battery (semi-solid, target) | 3.0-3.5 |
| **Total estimated** | **8.0-9.3** |
| MTOW limit | 10.0 |
| **Margin** | **0.7-2.0** |

## Endurance Estimate

**Assumptions**:
- MTOW: 9.0 kg (mid-range estimate)
- Cruise speed: 17 m/s
- L/D ratio: ~15 (high-aspect-ratio wing)
- Propulsive efficiency: 0.85
- Battery: 3.2 kg semi-solid at 310 Wh/kg = 992 Wh
- Payload power: ~30W (Jetson 15-25W + camera/gimbal 10-15W)
- Cruise power: ~130W (aerodynamic) + 30W (payload) = ~160W total
- Battery reserve: 20%
- Usable energy: 992 × 0.80 = 794 Wh

**Theoretical endurance**: 992 / 160 = 6.2 hours
**Practical endurance (with reserve + real-world losses)**: 794 / 160 ≈ **5.0 hours**

**Range at cruise**: 5.0h × 17 m/s × 3.6 = **306 km**

This is conservative. Optimization of airfoil, wing loading, and propulsion system could push practical endurance to 5.5-6.0 hours.

## Testing Strategy

### Integration / Functional Tests
- Static load test: wing spar to 3× max flight load (verify no failure at 3g)
- Ground vibration test: verify no flutter modes within flight envelope
- Range/endurance test: fly at cruise speed until 20% battery reserve, measure actual endurance vs predicted
- Payload integration test: verify all electronics (Jetson, Pixhawk, camera, gimbal) function correctly with airframe vibration
- CG range test: verify stable flight across full CG envelope

### Non-Functional Tests
- Temperature endurance: ground soak at -10°C and +45°C, verify battery and avionics function
- Wind resistance: fly in 10-12 m/s sustained wind, verify controllability and endurance impact
- Hard landing test: drop from 1m at 2 m/s descent rate onto belly, verify structural integrity (Kevlar reinforcement zones)
- Battery cycle test: charge/discharge 50 cycles, verify capacity retention ≥95%
- EMI test: verify Jetson/camera does not interfere with GPS/telemetry

## References

1. UAVMODEL — Carbon Fiber Fixed Wing Drones: https://www.uavmodel.com/blogs/news/skyeye-sr260-fixed-wing-drone-2600mm-long-endurance-mapping-amp-inspection
2. SUX61 UAV Frame: https://aerojetparts.com/product/sux61-uav-frame-carbon-fiber-8kg-payload-91min-endurance/
3. FAI — Vanilla UAV Flight Duration Record: https://www.fai.org/vanilla-uav-flight-duration-record
4. Springer — EPS-Fiber-Reinforced Composite Wing Analysis (2024): https://link.springer.com/10.1007/s11029-024-10185-3
5. Grepow Semi-Solid Battery: https://www.grepow.com/semi-solid-state-battery/300wh-kg-series-high-energy-density-battery-pack.html
6. Tattu Semi-Solid Battery: https://tattuworld.com/semi-solid-state-battery/
7. Herewin Semi-Solid Guide (2026): https://www.herewinpower.com/blog/solid-state-drone-batteries-ultimate-guide/
8. Applied Aeronautics Albatross: https://www.appliedaeronautics.com/albatross-uav
9. KingRaysCarbon — CF vs Al: https://kingrayscarbon.com/carbon-fiber-vs-aluminum-for-drone-frames-which-performs-better/
10. Dronecarbon — Kevlar vs CF: https://www.dronecarbon.com/kevlar-vs-carbon-fiber_a9075.html
11. Herewin — LFP vs LiPo vs Semi-Solid (2026): https://www.herewinpower.com/blog/lfp-vs-lipo-vs-semi-solid-industrial-drone-batteries-2026-roi-safety-and-performance/
12. DeltaQuad Evo Specs: https://docs.deltaquad.com/gov/vehicle-specifications
13. DeltaQuad Evo 8h55m Record: https://uasweekly.com/2025/06/27/deltaquad-evo-sets-record-with-8-hour-flight-endurance-for-electric-vtol-uas-milestone/
14. T700 vs T800 Guide: https://www.carbonfibermaterial.com/t700-vs-t800-carbon-fiber-a-practical-guide-for-material-selection/
15. CFRP Manufacturing Comparison (Indonesian J. Aerospace): https://ejournal.brin.go.id/ijoa/article/view/286
16. Rohacell vs Foam Cores — Chem-Craft: https://chem-craft.com/blog/comparative-analysis-rohacell-vs-traditional-materials-in-composite-engineering/
17. Carbon-Kevlar Hybrid: https://ictmaterial.com/what-is-carbon-kevlar-hybrid-fabric-properties-and-use-cases/
18. Scabro Innovations — UAV Prototyping: https://scabroinnovations.com/diensten/composite-airframe-prototyping/
19. Tattu 330Wh/kg 6S Specs: https://www.tattuworld.com/semi-solid-state-battery/semi-solid-330wh-kg-33000mah-22-2v-10c-6s-battery.html
20. ASTM F3563-22: https://www.astm.org/f3563-22.html

## Related Artifacts
- AC Assessment: `_standalone/UAV_frame_material/00_research/UAV_frame_material/00_ac_assessment.md`