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Update UAV specifications and enhance performance metrics in the GPS-Denied system documentation. Refine acceptance criteria and clarify operational constraints for improved understanding.

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Oleksandr Bezdieniezhnykh
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# 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`
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# Solution Draft (Rev 02)
## Revised Constraints (vs Draft 01)
| Constraint | Draft 01 | Draft 02 |
|-----------|----------|----------|
| Cost per unit | $100k prototype | < $7k, target < $5k |
| Material | CFRP (T700) | S2 fiberglass (radio transparent) |
| Radio transparency | Not considered | Required — full RF transparency for GPS, telemetry, data links |
| Flight time | 5-6 hours target | Same if possible, can be less |
| Transport | Not specified | Disassembled fits in car trunk; 2 planes per pickup truck |
## Product Solution Description
A modular, radio-transparent electric fixed-wing reconnaissance UAV built with **S2 fiberglass/foam-core sandwich construction** with internal **carbon fiber spar reinforcement**. Designed for field deployment — disassembles into 3 sections (2 wing panels + fuselage) that fit in a car trunk, with 2 complete aircraft fitting in a standard pickup truck bed. Powered by semi-solid state batteries for maximum endurance.
**Target performance**: 3.5-5 hours practical flight endurance, 9-10 kg MTOW, ~3m wingspan, < $5k BOM per unit.
```
┌──────────────────────────────────────────────────────────────┐
│ MODULAR AIRFRAME LAYOUT │
│ │
│ LEFT WING PANEL FUSELAGE RIGHT WING PANEL │
│ (~1.5m span) (~1.0-1.1m) (~1.5m span) │
│ ┌──────────────┐ ┌──────────────┐ ┌──────────────┐ │
│ │ S2 FG skin │ │ S2 FG skin │ │ S2 FG skin │ │
│ │ PVC foam core│◄─►│ Battery bay │◄─►│ PVC foam core│ │
│ │ CF spar cap │ │ Payload bay │ │ CF spar cap │ │
│ │ (internal) │ │ Motor+ESC │ │ (internal) │ │
│ └──────────────┘ └──────────────┘ └──────────────┘ │
│ │
│ Wing-fuselage joint: aluminum spar joiner + 2 pin locks │
│ Assembly time target: < 10 minutes │
│ Material: S2 fiberglass = RF transparent (GPS/telemetry OK) │
│ Internal CF spar: minimal RF impact (narrow linear element) │
└──────────────────────────────────────────────────────────────┘
TRANSPORT CONFIGURATION (standard pickup truck, 6.5ft bed):
┌───────────────────────────────────────────┐
│ Truck bed: 198cm × 130cm (wheel wells) │
│ ┌──────────────────┐ ┌────────────────┐ │
│ │ Plane 1 wings │ │ Plane 2 wings │ │
│ │ (2 × 150cm long) │ │ (2 × 150cm) │ │
│ │ stacked ~20cm │ │ stacked ~20cm │ │
│ ├──────────────────┤ ├────────────────┤ │
│ │ Plane 1 fuselage │ │ Plane 2 fuse. │ │
│ │ (~110cm) │ │ (~110cm) │ │
│ └──────────────────┘ └────────────────┘ │
│ Total width: ~60cm × 2 = 120cm < 130cm ✓│
│ Total length: 150cm < 198cm ✓ │
└───────────────────────────────────────────┘
```
## Existing/Competitor Solutions Analysis
| Platform | MTOW | Endurance | Payload | Material | RF Transparent | Modular | Price |
|----------|------|-----------|---------|----------|---------------|---------|-------|
| Albatross (kit) | 10 kg | 4 hours | 4.5 kg | Fiberglass + CF | Partial | No (removable wings) | $1,500 kit |
| Albatross (RTF) | 10 kg | 4 hours | 4.5 kg | Fiberglass + CF | Partial | No | $4,800 |
| DeltaQuad Evo | 10 kg | 4.5h / 8.9h record | 1-3 kg | FG + CF + Kevlar | Partial | Wing removable | $25,000+ |
| Skywalker X8 | ~4 kg | 45-60 min | 1-2 kg | EPO foam | Yes | No | $489-598 |
| Mugin 2600 | 15 kg | 1.5-5h | 4 kg | Carbon fiber | No | Wing sections | $2,299+ |
**Key insight**: The Albatross kit at $1,500 proves that a 3m wingspan composite airframe is achievable at very low cost. Our target of < $5k per complete unit (with batteries) is realistic. No competitor offers the combination of radio transparency + modular transport + semi-solid batteries.
## Architecture
### Component: Frame Material
| Solution | Advantages | Limitations | Cost (per unit) | Fit |
|----------|-----------|-------------|----------------|-----|
| **S2 fiberglass skin + PVC foam core + internal CF spar (recommended)** | RF transparent skin, strong internal structure, good impact tolerance, easy to repair, $8-19/m² fabric | ~30-40% heavier than pure CFRP for equivalent stiffness | Fabric: $200-400; foam: $100-200; CF spar material: $50-100; resin: $80-150; total materials: $430-850 | ✅ Best balance of RF transparency, cost, repairability |
| E-glass fiberglass (instead of S2) | Cheapest glass option (~$3-5/m²), RF transparent, easy to work | 40% weaker than S2, requires thicker layup → heavier | Materials: $200-500 | ⚠️ Acceptable budget option, slightly heavier |
| Pure S2 fiberglass (no CF spar) | Maximum RF transparency, simplest construction | Insufficient wing stiffness at low weight, flutter risk | Materials: $300-600 | ❌ Stiffness deficit at acceptable weight |
| Pure CFRP (draft 01 approach) | Lightest, stiffest | Blocks RF — GPS/telemetry degraded, expensive | Materials: $800-1500 | ❌ Fails radio transparency requirement |
**Recommendation**: S2 fiberglass skin over PVC foam core with unidirectional carbon fiber spar caps (top and bottom of main spar, internal). The CF spar is a narrow linear element (~20-30mm wide per cap) inside the wing — negligible RF blockage. All external surfaces are S2 FG = fully radio transparent.
### Component: Construction Method
| Solution | Advantages | Limitations | Cost | Fit |
|----------|-----------|-------------|------|-----|
| **Vacuum-bagged foam sandwich (recommended)** | Good quality (53% stronger than hand layup), low tooling cost, reproducible | Requires vacuum pump + consumables | Equipment: $500 one-time; consumables: $50-100/unit | ✅ Best for low-cost production |
| Hand layup over foam core | Cheapest, simplest, no equipment needed | Lower quality (more voids), less consistent | Minimal equipment | ⚠️ Acceptable for prototypes only |
| Vacuum infusion | Best quality (71% stronger than hand layup) | More complex setup, higher consumable cost | Equipment: $1000+; consumables: $100-200/unit | ⚠️ Worth it at higher volume (>20 units) |
| Outsourced prepreg manufacturing | Highest quality | Expensive per unit at low volume | $2000-5000/airframe | ❌ Exceeds per-unit budget |
### Component: Foam Core
| Solution | Advantages | Limitations | Cost/m² | Fit |
|----------|-----------|-------------|---------|-----|
| **PVC Divinycell H60 (recommended)** | Good stiffness/weight, closed-cell, 80°C tolerant, industry standard | More expensive than XPS | $50-80/m² | ✅ Best value for production |
| XPS (extruded polystyrene) | Cheapest closed-cell, easy to shape with hot wire | Lower compressive strength, 75°C limit | $10-20/m² | ✅ Good budget alternative |
| EPS (expanded polystyrene) | Very cheap | Absorbs moisture, lowest strength | $5-10/m² | ⚠️ Only for non-critical areas |
### Component: Wing-Fuselage Joint (Modular Assembly)
| Solution | Advantages | Limitations | Cost | Fit |
|----------|-----------|-------------|------|-----|
| **Aluminum spar joiner + pin locks (recommended)** | Quick assembly (<5 min), proven in RC/UAV, high strength, replaceable | Adds ~100-150g per joint (200-300g total) | $30-60 machined aluminum parts | ✅ Simple, reliable, fast |
| 3D-printed spar connector with hinge | Very fast assembly (<2 min), lightweight | Lower strength, fatigue concerns, requires testing | $10-20 per set | ⚠️ Good for prototype, risky for production |
| Bolted flange joint | Very strong, proven in full-scale aviation | Heavier (~200g per joint), slower assembly (10+ min) | $20-40 | ⚠️ Over-engineered for this scale |
**Design**: Wing spar is a carbon fiber tube or C-channel running the full wing half-span. At the root, it slides into an aluminum joiner tube embedded in the fuselage. Secured with 2 quick-release pins (top and bottom). Electrical connections (servo leads) via a quick-disconnect plug at each wing root.
### Component: Battery Technology
| Solution | Energy density | Endurance impact | Cycle life | Cost/pack | Fit |
|----------|---------------|-----------------|------------|-----------|-----|
| **Semi-solid Tattu 330Wh/kg 6S (recommended)** | 315 Wh/kg pack | Baseline (best) | 800-1200 | ~$800-1200 est. | ✅ Best endurance per $ |
| Semi-solid Grepow 300Wh/kg 6S | 280-300 Wh/kg pack | -5 to -10% | 1200+ | ~$700-1000 est. | ✅ Good alternative |
| Li-Ion 21700 custom pack (6S) | 200-220 Wh/kg pack | -25 to -35% | 500-800 | ~$200-400 | ⚠️ Budget option, significant endurance loss |
| LiPo 6S (standard RC) | 150-180 Wh/kg pack | -40 to -50% | 200-500 | ~$100-200 | ❌ Too much endurance loss |
## Weight Budget (S2 Fiberglass Build)
| Component | Weight (kg) | Notes |
|-----------|-------------|-------|
| Bare airframe (S2 FG sandwich + CF spar) | 3.8-4.5 | ~30% heavier than pure CFRP; Albatross FG+CF is 3.35 kg |
| Wing joints (aluminum) | 0.2-0.3 | Spar joiners + pins + quick-disconnect plugs |
| Motor + ESC + propeller | 0.4-0.6 | |
| Wiring, connectors, misc | 0.3-0.4 | |
| **Platform subtotal** | **4.7-5.8** | |
| Payload (camera + gimbal + Jetson + Pixhawk + GPS) | 1.47 | Fixed |
| Battery (semi-solid) | 2.7-3.8 | Remainder to MTOW |
| **Total (target MTOW 10 kg)** | **~10.0** | |
Conservative estimate: platform 5.3 kg + payload 1.47 kg + battery 3.2 kg = 9.97 kg.
## Endurance Estimate (S2 Fiberglass)
**Assumptions**:
- MTOW: 10 kg
- Platform weight: 5.3 kg (S2 FG airframe + motor + wiring + joints)
- Payload: 1.47 kg
- Battery: 3.23 kg semi-solid at 310 Wh/kg = 1001 Wh
- Cruise power: ~140W (slightly higher than CFRP due to heavier aircraft → higher induced drag)
- Payload power: ~30W (Jetson + camera + gimbal)
- Total system power: ~170W
- Battery reserve: 20%
- Usable energy: 1001 × 0.80 = 801 Wh
- Real-world efficiency factor: 0.75
**Theoretical endurance**: 1001 / 170 = 5.9 hours
**Practical endurance (with reserve)**: 801 / 170 ≈ **4.7 hours**
**Practical endurance (with reserve + real-world losses)**: 801 × 0.75 / 170 ≈ **3.5 hours**
**Comparison to Draft 01 (CFRP)**:
- Draft 01: 5.0 hours practical → Draft 02: 3.5-4.7 hours practical
- Endurance reduction: ~15-30% depending on conditions
- Still competitive with Albatross (4h with LiPo) when using semi-solid batteries
**With budget Li-Ion pack instead** (to stay under $5k):
- 3.23 kg Li-Ion at 210 Wh/kg = 678 Wh → usable 542 Wh
- Practical: 542 / 170 ≈ **3.2 hours** (reserve only) / **2.4 hours** (worst case)
## BOM Cost Estimate (Per Unit)
| Component | Low Est. | High Est. | Notes |
|-----------|----------|-----------|-------|
| S2 fiberglass fabric | $150 | $300 | ~8-10 m² at $15-30/m² |
| PVC foam core (Divinycell H60) | $100 | $200 | Wing + fuselage panels |
| Epoxy resin + hardener | $80 | $150 | ~2-3 kg resin |
| CF spar material (tube + UD tape) | $50 | $100 | Spar caps + tubes |
| Aluminum spar joiners (machined) | $30 | $60 | 2 joiner sets, batch machined |
| Vacuum bagging consumables | $30 | $60 | Bag, breather, peel ply, tape |
| Motor (brushless, ~500W) | $80 | $150 | |
| ESC (40-60A) | $40 | $80 | |
| Propeller (folding) | $15 | $30 | |
| Servos (4× ailerons + elevator + rudder) | $60 | $120 | |
| Wiring, connectors, hardware | $50 | $100 | |
| Semi-solid battery (Tattu 330Wh/kg 6S 33Ah) | $800 | $1,200 | Single pack |
| RC receiver | $30 | $80 | |
| Telemetry radio | $100 | $300 | |
| Transport case / padded bag | $50 | $150 | |
| **Subtotal (airframe + propulsion + battery)** | **$1,665** | **$3,080** | |
| Pixhawk 6x + GPS | $300 | $500 | If not already owned |
| **Total BOM (without mission payload)** | **$1,965** | **$3,580** | |
| **Total BOM (with Pixhawk, without mission payload)** | **$2,265** | **$4,080** | |
Manufacturing labor (per unit, assuming in-house build with molds amortized):
- First unit (mold making): +$2,000-3,000 tooling
- Subsequent units: ~$500-1,000 labor per airframe (8-16 hours assembly)
**Per-unit cost at batch of 5+**: **$2,800-4,500** (without mission payload) ✅ Under $5k target
**Per-unit cost at batch of 1 (first prototype)**: **$5,000-7,000** (includes tooling) ✅ Under $7k target
## Modular Transport Specifications
| Dimension | Value |
|-----------|-------|
| Wing panel length | ~1.50 m (half-span) |
| Wing panel chord | ~0.25-0.30 m |
| Wing panel thickness | ~0.04-0.05 m |
| Fuselage length | ~1.00-1.10 m |
| Fuselage width/height | ~0.15-0.20 m |
| Assembly time | < 10 minutes (target) |
| Disassembly time | < 5 minutes |
**Car trunk fit**: 3 sections (2 wings + fuselage) fit in standard sedan trunk (~120×80×45 cm). Wings stack flat, fuselage alongside. ✅
**Pickup truck (2 planes)**: Standard 6.5ft bed (198×130 cm between wheel wells). Each plane's longest component is 150 cm (< 198 cm bed length). Two planes side by side need ~120 cm width (< 130 cm between wheel wells). ✅
## Trade-off Summary: S2 Fiberglass vs CFRP
| Dimension | S2 Fiberglass (Draft 02) | CFRP (Draft 01) | Winner |
|-----------|--------------------------|-----------------|--------|
| RF transparency | ✅ Excellent — transparent to GPS, telemetry, data links | ❌ Blocks RF, requires external antennas | S2 FG |
| Cost per unit | $2,800-4,500 | $30,000-60,000 (prototype) | S2 FG |
| Endurance | 3.5-4.7 hours practical | 5.0 hours practical | CFRP (+15-30%) |
| Airframe weight | 3.8-4.5 kg bare | 2.8-3.2 kg bare | CFRP (-25%) |
| Impact resistance | Good (fiberglass is tough) | Poor (CFRP is brittle) | S2 FG |
| Field repairability | Easy (fiberglass patches, epoxy) | Difficult (specialized repair) | S2 FG |
| Manufacturing complexity | Low (basic vacuum bagging) | Medium-High (precise layup) | S2 FG |
| Transport / modularity | Same | Same | Tie |
**Conclusion**: S2 fiberglass is the clear choice given the revised constraints. The 15-30% endurance reduction vs CFRP is offset by radio transparency (critical for the mission), 10x lower cost, and significantly easier manufacturing and field repair.
## Testing Strategy
### Integration / Functional Tests
- Static wing load test: 3× max flight load at spar joiner (verify no failure at 3g)
- Wing joint cycling: 100× assembly/disassembly, verify no wear or looseness
- RF transparency test: measure GPS signal strength through airframe skin vs free-air (target: < 3 dB attenuation)
- Assembly time test: verify < 10 minutes from transport case to flight-ready
- Range/endurance test: fly at cruise until 20% reserve, measure actual vs predicted
- Payload integration test: all electronics function under vibration
### Non-Functional Tests
- Transport test: load 2 planes in pickup truck, drive 100 km on mixed roads, verify no damage
- Hard landing test: belly landing at 2 m/s descent, verify structural integrity
- Field repair test: simulate wing skin puncture, repair with FG patch + epoxy, verify airworthy in < 30 minutes
- Temperature test: battery + avionics function at -10°C and +45°C
- Battery cycle test: 50 charge/discharge cycles, verify ≥95% capacity retention
## Production BOM: 5 UAVs From Scratch
### A. One-Time Equipment & Tooling
| Item | Qty | Unit Price | Total | Notes |
|------|-----|-----------|-------|-------|
| **Composite Workshop Equipment** | | | | |
| Vacuum pump (6 CFM 2-stage) | 1 | $280 | $280 | VIOT or equivalent |
| Vacuum bagging starter kit (gauges, tubing, valves, connectors) | 1 | $150 | $150 | |
| Digital scale (0.1g precision, 5 kg capacity) | 1 | $50 | $50 | For resin mixing |
| Mixing cups, squeegees, rollers, brushes set | 1 | $80 | $80 | |
| Large work table (4×8 ft plywood + sawhorses) | 1 | $150 | $150 | |
| Self-healing cutting mat (4×8 ft) | 1 | $80 | $80 | |
| **Foam Cutting** | | | | |
| CNC hot wire foam cutter (4-axis, DIY kit) | 1 | $350 | $350 | Vortex-RC or similar |
| **Mold Making** | | | | |
| MDF sheets for plugs (4×8 ft × ¾") | 4 | $45 | $180 | Wing + fuselage plugs |
| Tooling epoxy + fiberglass for female molds | 1 | $600 | $600 | 2× wing mold halves + fuselage molds |
| Mold release agent (PVA + wax) | 1 | $60 | $60 | |
| Filler / fairing compound | 1 | $80 | $80 | For plug finishing |
| Sandpaper assortment (80-600 grit) | 1 | $40 | $40 | |
| **Metal Work** | | | | |
| Aluminum spar joiner machining (batch of 12 sets) | 1 | $400 | $400 | CNC outsourced, 10 sets + 2 spare |
| **PPE & Ventilation** | | | | |
| Respirator (half-face, organic vapor + P100) | 2 | $40 | $80 | 1 per worker |
| Nitrile gloves (box of 200) | 2 | $25 | $50 | |
| Safety glasses | 3 | $10 | $30 | |
| Portable fume extractor / fan | 1 | $120 | $120 | |
| **Hand & Power Tools** | | | | |
| Drill + mixing paddle | 1 | $80 | $80 | |
| Jigsaw | 1 | $60 | $60 | |
| Rotary tool (Dremel) | 1 | $50 | $50 | |
| Heat gun | 1 | $35 | $35 | |
| Scissors, utility knives, rulers, clamps | 1 | $80 | $80 | Assorted set |
| **Charging & Testing** | | | | |
| Battery charger (6S/12S balance, 1000W) | 1 | $200 | $200 | |
| Multimeter | 1 | $30 | $30 | |
| Servo tester | 1 | $15 | $15 | |
| **Software & Design** | | | | |
| CAD/CAM (FreeCAD / OpenVSP — free) | — | $0 | $0 | Open source |
| Hot wire CNC software (included with cutter) | — | $0 | $0 | |
| | | | | |
| **EQUIPMENT & TOOLING TOTAL** | | | **$3,335** | |
### B. Raw Materials (for 5 UAVs + 20% waste margin)
Material quantities per UAV:
- Wing skin area: ~1.6 m² planform × 2 (top+bottom) × 2 layers = ~6.4 m² S2 fabric
- Fuselage skin: ~0.6 m² × 2 layers = ~1.2 m²
- Tail surfaces: ~0.3 m² × 2 layers = ~0.6 m²
- Total S2 fabric per UAV: ~8.2 m² → with waste: ~10 m²
- Foam core per UAV: ~2.5 m² (wings + tail)
- Resin per UAV: ~2.5 kg (fabric weight × 1:1 ratio + extra)
| Item | Qty (5 UAVs + margin) | Unit Price | Total | Notes |
|------|----------------------|-----------|-------|-------|
| **Structural Materials** | | | | |
| S2 fiberglass fabric 6oz (30" wide) | 70 yards (~64 m) | $12.50/yard | $875 | ~10 m² per UAV × 5 + waste |
| PVC foam Divinycell H60 10mm (1.22×0.81m sheets) | 16 sheets | $40/sheet | $640 | ~2.5 m² per UAV × 5 + waste |
| Laminating epoxy resin (West System 105 or equiv) | 4 gallons | $125/gal | $500 | ~2.5 kg resin per UAV |
| Epoxy hardener | 2 gallons | $80/gal | $160 | |
| Carbon fiber tube (spar, 20mm OD, 1.5m) | 12 | $25 each | $300 | 2 per UAV + spare |
| Carbon fiber UD tape (spar caps, 25mm wide) | 30 m | $5/m | $150 | 5m per UAV + spare |
| **Vacuum Bagging Consumables** | | | | |
| Vacuum bag film (5m × 1.5m rolls) | 6 rolls | $20/roll | $120 | ~1 roll per UAV + spare |
| Peel ply fabric | 20 yards | $5/yard | $100 | |
| Breather cloth | 20 yards | $4/yard | $80 | |
| Sealant tape | 6 rolls | $12/roll | $72 | |
| **Hardware (per 5 UAVs)** | | | | |
| Aluminum spar joiners | (included in tooling) | — | $0 | Batch machined above |
| Quick-release pins (stainless) | 20 | $3 each | $60 | 4 per UAV |
| Quick-disconnect electrical plugs | 10 | $8 each | $80 | 2 per UAV (wing roots) |
| Misc hardware (bolts, nuts, hinges, control horns) | 5 sets | $30/set | $150 | |
| | | | | |
| **RAW MATERIALS TOTAL (5 UAVs)** | | | **$3,287** | |
| **Per UAV materials** | | | **~$657** | |
### C. Electronics & Propulsion (per UAV × 5)
| Item | Qty/UAV | Unit Price | Per UAV | ×5 Total | Notes |
|------|---------|-----------|---------|----------|-------|
| Motor (brushless ~500W, e.g. Dualsky XM5050EA) | 1 | $90 | $90 | $450 | Fixed-wing optimized |
| ESC (40-60A, BLHeli) | 1 | $50 | $50 | $250 | |
| Folding propeller (13×8 or similar) | 2 | $15 | $30 | $150 | 1 spare per UAV |
| Servos (digital metal gear, 15-20 kg·cm) | 5 | $25 | $125 | $625 | 2× aileron + elevator + rudder + flap/spare |
| Pixhawk 6X Mini + GPS | 1 | $380 | $380 | $1,900 | |
| RC receiver (long range, e.g. TBS Crossfire) | 1 | $60 | $60 | $300 | |
| RFD900x telemetry pair (shared GCS unit) | 1 air + 0.2 GCS | $170 (air) | $170 | $850 + $350 GCS = $1,200 | 1 GCS module shared |
| Power distribution board + BEC | 1 | $25 | $25 | $125 | |
| Wiring, connectors (XT90, JST, servo ext.) | 1 set | $40 | $40 | $200 | |
| Semi-solid battery (Tattu 330Wh/kg 6S 33Ah) | 1 | $732 | $732 | $3,660 | |
| | | | | | |
| **ELECTRONICS TOTAL (5 UAVs)** | | | | **$8,910** | |
| **Per UAV electronics** | | | **~$1,702** | | Excl. shared GCS telemetry |
### D. Consumables & Misc (for 5 UAVs)
| Item | Total | Notes |
|------|-------|-------|
| Transport bags / padded cases (per UAV) | $300 | $60 × 5 (padded wing bags + fuselage bag) |
| Battery charger cables + adapters | $50 | |
| Field repair kit (S2 FG patches, epoxy sachets, sandpaper) | $150 | $30 × 5 |
| Spare hardware kit (pins, bolts, servo horns) | $100 | |
| Shipping / freight (materials + components) | $400 | Estimate |
| **CONSUMABLES TOTAL** | **$1,000** | |
### E. Labor
| Role | People | Duration | Rate | Total | Notes |
|------|--------|----------|------|-------|-------|
| Mold making + setup (one-time) | 2 | 3 weeks | $30/hr | $7,200 | 2 people × 40h/wk × 3 wk |
| Airframe layup + cure (per UAV) | 2 | 3 days | $30/hr | $2,880 | 2 people × 8h × 3 days × 5 UAVs |
| Post-cure trim, finish, assembly | 1 | 2 days | $30/hr | $2,400 | 1 person × 8h × 2 days × 5 |
| Electronics integration + wiring | 1 | 1.5 days | $35/hr | $2,100 | 1 person × 8h × 1.5 days × 5 |
| QA, testing, calibration | 1 | 1 day | $35/hr | $1,400 | 1 person × 8h × 1 day × 5 |
| **LABOR TOTAL** | | | | **$15,980** | |
| **Per UAV labor** | | | | **~$2,516** | Including amortized mold making |
### F. Production Summary — Total Investment for 5 UAVs
| Category | Total | Per UAV |
|----------|-------|---------|
| A. Equipment & Tooling (one-time) | $3,335 | $667 |
| B. Raw Materials | $3,287 | $657 |
| C. Electronics & Propulsion | $8,910 | $1,782 |
| D. Consumables & Misc | $1,000 | $200 |
| E. Labor | $15,980 | $3,196 |
| | | |
| **GRAND TOTAL (5 UAVs)** | **$32,512** | |
| **Per UAV (all-in, including labor)** | | **$6,502** |
| **Per UAV (materials + electronics only, no labor)** | | **$3,306** |
### G. Cost Optimization Options
| Optimization | Savings/UAV | Impact |
|-------------|-------------|--------|
| Use XPS foam instead of Divinycell H60 | -$90 | Slightly lower stiffness, acceptable for prototype |
| Use E-glass instead of S2 glass | -$100 | ~40% weaker, needs thicker layup → ~200g heavier |
| Use Li-Ion 21700 pack instead of Tattu semi-solid | -$400 | Endurance drops from 3.5-4.7h to 2.4-3.2h |
| Self-machine spar joiners (manual lathe) | -$50 | Requires metalworking skill |
| Use cheaper servos ($15 each) | -$50 | Lower torque, shorter lifespan |
| **Aggressive budget build** | **-$690** | **$2,616/UAV materials only** |
### H. Minimum Viable Team
| Role | Count | Skills Required | Commitment |
|------|-------|----------------|------------|
| Composite fabricator | 1-2 | Fiberglass layup, vacuum bagging, mold making | Full-time during build (8 weeks) |
| Electronics/avionics tech | 1 | Soldering, Pixhawk configuration, wiring | Part-time (can overlap with fabricator) |
| **Minimum: 2 people for 8 weeks** | | | |
**Timeline for 5 UAVs**:
- Week 1-3: Mold making (CNC foam plugs → fiberglass female molds)
- Week 4-5: First 2 airframes layup + cure + trim
- Week 5-6: Next 3 airframes layup + cure + trim
- Week 6-7: Electronics integration all 5 units
- Week 7-8: Testing, calibration, flight testing
- **Total: ~8 weeks with 2 people**
### I. Minimal Absolute Cost (No Labor Accounted)
If labor is free (owner-operators building their own):
| Category | Total | Per UAV |
|----------|-------|---------|
| Equipment & Tooling | $3,335 | $667 |
| Raw Materials | $3,287 | $657 |
| Electronics & Propulsion | $8,910 | $1,782 |
| Consumables & Misc | $1,000 | $200 |
| **TOTAL (5 UAVs, no labor)** | **$16,532** | |
| **Per UAV (no labor)** | | **$3,306** |
**Absolute minimum per UAV** (with budget optimizations from Section G): **~$2,616**
## References
1-20: See Draft 01 references (all still applicable)
Additional sources:
21. S-Glass vs E-Glass comparison: https://wiki-science.blog/s-glass-vs-e-glass-key-differences
22. Reinforcement Fiber Reference: https://explorecomposites.com/materials-library/fiber-ref/
23. S-Glass vs Carbon Fiber: https://carbonfiberfriend.com/s-glass-vs-carbon-fiber/
24. RF Attenuation by composite materials: https://www.rocketryforum.com/threads/rf-attenuation-by-body-tube-nosecone.186634/
25. Russian foamplast UAV (max radio transparency): https://bulgarianmilitary.com/2023/10/15/russia-unveils-foamplast-fpv-uav-with-max-radio-transparency/
26. Albatross UAV Kit: https://store.appliedaeronautics.com/albatross-uav-kit/
27. UAV spar connector development: https://www.konelson.net/home/spar-connector-development
28. Scabro Innovations UAV prototyping: https://scabroinnovations.com/diensten/composite-airframe-prototyping/
29. Tattu 330Wh/kg 6S pricing — GenStattu: https://genstattu.com/tattu-semi-solid-state-330wh-kg-33000mah-10c-22-2v-6s1p-g-tech-lipo-battery-pack-with-xt90-s-plug/
30. Pixhawk 6X pricing — Holybro: https://holybro.com/products/pixhawk-6x-rev3
31. RFD900x pricing — DrUAV: https://druav.com/products/rfdesign-rfd900x
32. Composite workshop setup — Fibre Glast: https://www.fibreglast.com/blogs/learning-center/setting-up-a-composite-shop
33. CNC hot wire foam cutter — Vortex-RC: https://www.vortex-rc.com/product/4-axis-diy-hot-wire-cnc-for-rc-hobbyists-aeromodellers-and-designers/
34. Composite mold making — Canuck Engineering: https://www.canuckengineering.com/capabilities/composite-molds/