# Solution Draft (Rev 03) — 8+ Hour Endurance

## Assessment Findings

| Old Component Solution | Weak Point | New Solution |
|------------------------|------------|-------------|
| Single 6S 33Ah battery (1001 Wh) | Only 3.5-4.7h endurance — insufficient for 8h target | 4× 6S 33Ah 350 Wh/kg packs (2930 Wh) or 2× 12S 33Ah (2930 Wh) |
| 10 kg MTOW | Cannot carry enough battery for 8h at current energy densities | Increase to 18 kg MTOW |
| 3.0m wingspan | L/D ≈ 15 at AR≈10; higher wing loading increases cruise power | Scale to 3.8-4.0m wingspan (AR≈14, L/D≈17) |
| S2 FG airframe (3m) | Good but limited battery capacity due to MTOW constraint | S2 FG airframe scaled to 4m; same material, radio transparency preserved |
| Motor + ESC (500W class) | Undersized for 18 kg platform | Scale to 700-800W motor + 60-80A ESC |
| ADTI 20L V1 nav camera (20MP APS-C) | 34 cm/px GSD at 2 km — too coarse for feature matching | ADTI 26S V1 (26MP APS-C, mech. shutter) + 35mm lens → 21.6 cm/px at 2 km |
| Viewpro A40 Pro AI camera (1080p, 40×) | 1080p limits FoV to 65×37m at max zoom from 2 km | Viewpro Z40K (4K, 20×) → 2.7 cm/px GSD, 103×58m FoV, 479g lighter |

## Product Solution Description

A scaled-up modular, radio-transparent electric fixed-wing reconnaissance UAV built with **S2 fiberglass/foam-core sandwich construction** and internal carbon fiber spar reinforcement. Wingspan increased to **3.8-4.0m** for better aerodynamic efficiency (L/D ≈ 17). MTOW raised to **18 kg** to accommodate **4× semi-solid battery packs** totaling ~2930 Wh. Disassembles into modular sections for pickup truck transport; 2 complete aircraft fit in a standard 6.5ft bed.

**Target performance**: 8-9 hours practical flight endurance, 18 kg MTOW, 3.8-4.0m wingspan. Camera payload: ADTI 26S V1 (26MP, mech. shutter, 21.6 cm/px at 2 km) for GPS-denied navigation + Viewpro Z40K (4K, 20× zoom, 2.7 cm/px at 2 km) for AI reconnaissance. Total payload 892g — 578g lighter than Draft 02.

```
┌──────────────────────────────────────────────────────────────────┐
│              SCALED-UP MODULAR AIRFRAME LAYOUT                   │
│                                                                  │
│  LEFT WING PANEL       FUSELAGE           RIGHT WING PANEL       │
│  (~1.9m span)         (~1.1m)             (~1.9m span)          │
│  ┌──────────────┐   ┌──────────────────┐   ┌──────────────┐     │
│  │ S2 FG skin   │   │ S2 FG skin       │   │ S2 FG skin   │     │
│  │ PVC foam core│◄─►│ Battery bay ×4   │◄─►│ PVC foam core│     │
│  │ CF spar cap  │   │ Payload bay      │   │ CF spar cap  │     │
│  │ (internal)   │   │ Motor (700W)     │   │ (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)      │
│                                                                  │
│  BATTERY BAY (4 packs, 2S2P wiring for 12S 66Ah):               │
│  ┌──────┐ ┌──────┐                                              │
│  │ 6S   │ │ 6S   │  Series pair A → 12S 33Ah                    │
│  │ 33Ah │ │ 33Ah │                                              │
│  └──────┘ └──────┘                                              │
│  ┌──────┐ ┌──────┐                                              │
│  │ 6S   │ │ 6S   │  Series pair B → 12S 33Ah                    │
│  │ 33Ah │ │ 33Ah │  Pairs A+B in parallel → 12S 66Ah            │
│  └──────┘ └──────┘                                              │
│  Total: 44.4V × 66Ah = 2930 Wh                                  │
└──────────────────────────────────────────────────────────────────┘

TRANSPORT CONFIGURATION (standard pickup truck, 6.5ft bed):
┌───────────────────────────────────────────────┐
│  Truck bed: 198cm × 130cm (between wells)      │
│  ┌────────────────────┐ ┌──────────────────┐  │
│  │ Plane 1 wings      │ │ Plane 2 wings    │  │
│  │ (2 × 190cm long)   │ │ (2 × 190cm)      │  │
│  │ stacked ~25cm      │ │ stacked ~25cm    │  │
│  ├────────────────────┤ ├──────────────────┤  │
│  │ Plane 1 fuselage   │ │ Plane 2 fuse.    │  │
│  │ (~110cm)           │ │ (~110cm)         │  │
│  └────────────────────┘ └──────────────────┘  │
│  Width per plane: ~35cm × 2 = 70cm            │
│  Total width: 70cm × 2 = 140cm > 130cm ⚠️     │
│  → Stack all 4 wings in one pile + 2 fuselages │
│    alongside: 190cm × 70cm + 110cm × 40cm     │
│    Total width: ~110cm < 130cm ✓               │
│  Total length: 190cm < 198cm ✓                 │
└───────────────────────────────────────────────┘
```

## Existing/Competitor Solutions Analysis

| Platform | MTOW | Endurance | Battery | Wingspan | Material | RF Transparent | Transport | Price |
|----------|------|-----------|---------|----------|----------|---------------|-----------|-------|
| DeltaQuad Evo (standard) | 10 kg | 4h32m | 2× 22Ah semi-solid | 2.69m | CF+Kevlar+FG | Partial | Wing removable | $25,000+ |
| DeltaQuad Evo (record) | ~9 kg | **8h55m** | 2× Tulip Tech 450 Wh/kg | 2.69m | CF+Kevlar+FG | Partial | Wing removable | N/A (prototype batteries) |
| **YUAV Y37** | 17-20 kg | **8.5h** (1 kg payload) | 12S 60Ah semi-solid (~2700 Wh) | 3.7m | Full carbon | ❌ No | 138×55×45 cm | ~$15,000+ est. |
| NOCTUA (H2) | 20-25 kg | **10h** | Hydrogen fuel cell | 5.10m | CFRP | ❌ No | Field-portable | Academic |
| CW-80E (JOUAV) | >25 kg | 10-11h | Large electric | >4m | Composite | Unknown | Vehicle-mounted | $50,000+ |
| Albatross | 10 kg | 4h | LiPo | 3.0m | FG+CF | Partial | Removable wings | $4,800 RTF |
| **Our Draft 03** | **18 kg** | **8-9h target** | **4× 6S 33Ah 330+ Wh/kg** | **3.8-4.0m** | **S2 FG** | **✅ Yes** | **2 in pickup** | **$5,500-7,500** |

**Key insight**: YUAV Y37 proves that 8.5h at 17-20 kg MTOW with 3.7m wingspan and semi-solid batteries is achievable in production. Our design targets similar performance with S2 FG (heavier but radio transparent) offset by slightly longer wingspan for better L/D.

## Architecture

### Component: Frame Material

| Solution | Advantages | Limitations | Cost (per unit) | Fit |
|----------|-----------|-------------|----------------|-----|
| **S2 fiberglass skin + PVC foam core + internal CF spar (recommended)** | RF transparent, good impact tolerance, field repairable, proven at 3m scale | ~25-30% heavier than carbon at 4m scale; requires careful weight management | $600-1,200 materials | ✅ Only option that preserves RF transparency |
| Full carbon fiber (YUAV Y37 approach) | Lightest possible (~4-5 kg bare at 4m), best L/D | Blocks RF — GPS/telemetry degraded | $1,500-3,000 | ❌ Fails radio transparency |
| Carbon-Kevlar hybrid | Good crash survivability, lighter than FG | Partially blocks RF, expensive, hard to machine | $1,200-2,500 | ❌ RF compromise |
| S2 FG with Dyneema (UHMWPE) reinforcement | RF transparent, excellent impact resistance | Dyneema has poor compression strength, complex bonding | $800-1,500 | ⚠️ Complex but possible |

### Component: Wingspan & Aerodynamics

| Solution | L/D | Platform Weight | Endurance Impact | Transport | Fit |
|----------|-----|----------------|-----------------|-----------|-----|
| **3.8m wingspan (recommended for 2-in-pickup)** | ~17 | 6.5-7.5 kg | Baseline | 190cm half-wings fit 198cm bed ✓ | ✅ Best balance |
| 4.0m wingspan | ~17.5 | 7.0-8.0 kg | +3-5% | 200cm > 198cm; needs 3-section wing | ⚠️ Good but transport harder |
| 4.5m wingspan (single UAV transport) | ~18.5 | 8.0-9.5 kg | +8-12% | 225cm half-wings; 1 UAV per pickup | ⚠️ Maximum endurance, 1 plane only |
| 3.0m wingspan (Draft 02) | ~15 | 5.3 kg | Reference (3.5-4.7h) | 150cm easily fits | ❌ Insufficient for 8h |

**Recommendation**: 3.8m wingspan as primary design. Half-wings at 190cm fit within 198cm pickup bed length. AR ≈ 13.6, L/D ≈ 17. Optional detachable wingtips (+20cm per side = 4.2m total) for maximum endurance missions where single-UAV transport is acceptable.

### Component: Battery Configuration

| Solution | Total Energy | Weight | Wiring | Cost | Endurance (18 kg) | Fit |
|----------|-------------|--------|--------|------|-------------------|-----|
| **4× Tattu 6S 33Ah 350 Wh/kg (recommended)** | 2930 Wh | 8.86 kg | 2S2P → 12S 66Ah | ~$2,930 | **8-8.5h** | ✅ Best modularity, off-the-shelf |
| 2× Tattu 12S 33Ah 350 Wh/kg | 2930 Wh | 8.89 kg | 2P → 12S 66Ah | ~$3,800 | **8-8.5h** | ✅ Simpler wiring, same endurance |
| 1× Tattu 12S 76Ah 330 Wh/kg | 3374 Wh | 10.88 kg | Direct 12S | ~$4,300 | **8.5-9h** (needs 20 kg MTOW) | ⚠️ Best energy but requires 20 kg MTOW |
| 4× Xingto 6S 30Ah 370 Wh/kg | ~3280 Wh (est.) | ~8.9 kg (est.) | 2S2P → 12S 60Ah | ~$3,000-4,000 | **9-9.5h** | ⚠️ Higher density but less verified |
| Future: 4× 450 Wh/kg packs | ~4000 Wh | ~8.9 kg | 2S2P → 12S | $5,000-8,000 est. | **10-11h** | ⚠️ Not yet available at volume |

**4-Battery Configuration Detail (2S2P)**:
- 2 series pairs: each pair = 2× 6S in series = 12S 33Ah (44.4V, 1465 Wh)
- 2 parallel pairs: both 12S pairs in parallel = 12S 66Ah (44.4V, 2930 Wh)
- Requires: 2× series adapters, 1× parallel bus bar, battery management for each pair
- Advantage: individual pack replacement if one degrades; modular packing for transport
- Disadvantage: more wiring complexity, more connectors (failure points)

**2-Battery Configuration (2P)**:
- 2× 12S 33Ah in parallel = 12S 66Ah (44.4V, 2930 Wh)
- Simpler wiring, fewer connectors
- Each pack heavier individually (4.4 kg) but fewer handling steps

### Component: Motor & Propulsion (scaled for 18 kg)

| Solution | Power | Weight | Efficiency | Cost | Fit |
|----------|-------|--------|-----------|------|-----|
| **T-Motor U8 Lite (recommended)** | 700W max, 200-300W cruise | ~250g | η ≈ 0.92 at cruise | ~$150 | ✅ Proven for this MTOW class |
| Dualsky XM6350EA | 800W max | ~280g | η ≈ 0.90 | ~$120 | ✅ Good budget option |
| SunnySky V4014 | 600W max | ~210g | η ≈ 0.91 | ~$90 | ⚠️ Borderline power margin |

Propeller: 16×10 or 17×10 folding (vs 13×8 in Draft 02). Larger prop = higher propulsive efficiency at lower RPM, critical for endurance.

ESC: 60-80A continuous rating (vs 40-60A in Draft 02).

### Component: Foam Core

Same as Draft 02 — PVC Divinycell H60 recommended. No change.

### Component: Wing-Fuselage Joint

Same aluminum spar joiner + pin lock concept as Draft 02, but scaled for larger wing loads:
- Spar tube: 25mm OD (vs 20mm) to handle higher bending moments
- Joiner: machined 7075-T6 aluminum (stronger than 6061-T6)
- Weight: ~0.35 kg per joint set (vs 0.2-0.3 in Draft 02)

### Component: Camera Payload (Upgraded for 2 km Altitude)

**GSD = (Sensor Width × Altitude) / (Focal Length × Image Width)**

#### Navigation Camera (GPS-Denied System)

| Solution | Sensor | Resolution | Weight (body+lens) | GSD at 2 km | FoV at 2 km | Cost | Fit |
|----------|--------|-----------|-------------------|-------------|-------------|------|-----|
| ADTI 20L V1 (Draft 02) | APS-C 23.2mm | 20MP (5456×3632) | ~271g (121g+150g) | 34 cm/px (25mm) | 1855×1235m | $480+lens | ❌ Too coarse at 2 km |
| **ADTI 26S V1 + 35mm (recommended)** | APS-C 23.4mm | 26MP (6192×4128) | **~172g** (122g+50g) | **21.6 cm/px** (35mm) | 1337×892m | **$1,890** | ✅ Best value: mech. shutter, light, good GSD |
| ADTI 61PRO + 50mm | FF 35.7mm | 61MP (9504×6336) | ~426g (276g+150g) | **15 cm/px** (50mm) | 1426×950m | $2,830 | ✅ Best GSD but +$940 over 26S |
| Sony ILX-LR1 + 50mm | FF 35.7mm | 61MP (9504×6336) | ~393g (243g+150g) | **15 cm/px** (50mm) | 1426×950m | $3,100 | ⚠️ Lightest 61MP, drone-native, most expensive |
| ADTI 36S + 50mm | FF 35.9mm | 36MP (7360×4912) | ~390g (240g+150g) | 19.5 cm/px (50mm) | 1434×957m | $1,600 | ❌ No mechanical shutter — rolling shutter distortion |

**Recommendation**: ADTI 26S V1 with 35mm fixed lens. Mechanical shutter eliminates rolling shutter distortion (critical for GPS-denied feature matching at speed). 21.6 cm/pixel GSD at 2 km is sufficient for terrain feature matching, road/building identification, and satellite image correlation. IMX571 back-illuminated sensor delivers excellent dynamic range. Lightest option at 172g. Upgrade to ADTI 61PRO (+$940, 15 cm/px) if finer GSD is needed.

#### AI Camera (Reconnaissance — "Nice Shots" from 2 km)

| Solution | Sensor | Resolution | Zoom | Weight | GSD at 2 km (max zoom) | FoV at max zoom | Thermal | Cost | Fit |
|----------|--------|-----------|------|--------|----------------------|----------------|---------|------|-----|
| Viewpro A40 Pro (Draft 02) | 1/2.8" | 1080p (1920×1080) | 40× optical | 1074g | 3.4 cm/px | 65×37m | 640×512 | $2,999 | ⚠️ Good zoom but 1080p limits FoV |
| **Viewpro Z40K (recommended)** | 1/2.3" | **4K** (3840×2160) | 20× optical + 25× IA (4K) | **595g** | **2.7 cm/px** | **103×58m** | No | $2,999-4,879 | ✅ Better GSD, 2.5× wider FoV, 479g lighter |
| Viewpro Z40TIR | 1/2.3" | **4K** (3840×2160) | 20× optical + 40× IA (1080p) | ~700g est. | **2.7 cm/px** (4K) | 103×58m | 640×480 | ~$5,000 est. | ✅ Best of both: 4K + thermal |
| Viewpro A40T Pro | 1/2.8" | 1080p | 40× optical | ~1200g | 3.4 cm/px | 65×37m | 640×512 | $5,999 | ⚠️ Thermal + zoom but 1080p, heavy |

**Recommendation**: Viewpro Z40K. At 4K resolution with 20× optical zoom, it delivers **better GSD (2.7 vs 3.4 cm/px)** and **2.5× wider field of view** at max zoom than the A40 Pro at 1080p/40×. And it's **479g lighter** — weight that can go to battery or margin. If thermal is needed, step up to Z40TIR.

At 2.7 cm/pixel: vehicles clearly identifiable, human figures detectable, building details visible. At 20× wide end (53 cm/px): wide-area situational awareness covering ~2 km × 1.2 km.

#### Payload Weight Summary (Upgraded)

| Component | Draft 02/03 | Upgraded | Delta |
|-----------|-------------|---------|-------|
| Navigation camera (body+lens) | ADTI 20L + 25mm = 271g | ADTI 26S + 35mm = 172g | **-99g** |
| AI camera + gimbal | Viewpro A40 Pro = 1074g | Viewpro Z40K = 595g | **-479g** |
| Jetson Orin Nano Super | 60g | 60g | — |
| Pixhawk 6x + GPS | 65g | 65g | — |
| **Payload total** | **1470g** | **892g** | **-578g** |

**Net effect: 578g saved.** This frees ~191 Wh of battery capacity at 331 Wh/kg (~42 min extra endurance) or provides comfortable MTOW margin.

### Component: Alternative Power Sources Assessment

| Solution | Endurance | System Weight | Cost | Logistics | RF Compat. | Fit |
|----------|-----------|---------------|------|-----------|-----------|-----|
| **Semi-solid battery (primary)** | 8-9h | 8.9 kg | $2,930-3,800 | ✅ Charge from any outlet | ✅ S2 FG | ✅ Recommended |
| Solid-state 450 Wh/kg (upgrade path) | 10-11h | 8.9 kg (or lighter) | $5,000-8,000 est. | ✅ Same as above | ✅ S2 FG | ⚠️ Future upgrade |
| Hydrogen fuel cell | 15-17h | 9.8 kg (FC + tank) | $25,000-40,000 | ❌ H2 supply in field | ❌ Needs CFRP | ❌ Impractical |
| Solar + battery hybrid | +1h over battery alone | +0.5-1.0 kg panels | +$500-1,500 | ⚠️ Weather dependent | ⚠️ Panels on wing | ❌ Marginal gain |

## Weight Budget (18 kg MTOW, 3.8m Wingspan)

| Component | Weight (kg) | Notes |
|-----------|-------------|-------|
| Airframe (S2 FG sandwich + CF spar, 3.8m) | 5.5-6.5 | Scaled from 3m (3.8-4.5 kg) proportional to area |
| Wing joints (aluminum 7075) | 0.35 | Larger joiner for higher loads |
| Motor (700W) + ESC (80A) + folding prop 16" | 0.6 | Scaled up from Draft 02 |
| Wiring, connectors, battery bus | 0.45 | More wiring for 4-battery config |
| **Platform subtotal** | **6.9-7.9** | |
| Payload (ADTI 26S + Z40K + Jetson + Pixhawk + GPS) | 0.89 | Upgraded cameras — 578g lighter than Draft 02 payload |
| Battery (4× Tattu 6S 33Ah) | 8.86 | 4 × 2.216 kg |
| **Total** | **16.7-17.7** | |

Conservative: 7.9 + 0.89 + 8.86 = **17.65 kg** (well under 18 kg MTOW ✓).
Optimistic: 6.9 + 0.89 + 8.86 = **16.65 kg** (1.35 kg margin for accessories or extra battery).

## Endurance Estimates

### Flight Physics Parameters
- Cruise speed: 17 m/s (optimized for endurance at this wing loading)
- L/D at cruise: 17 (conservative; L/D_max ≈ 19-20 for AR=13.6)
- Overall propulsive efficiency: η = 0.72 (motor 0.92 × prop 0.82 × ESC 0.95)

### Cruise Power Calculation
P_cruise = (W × g × V) / (L/D × η)
= (18 × 9.81 × 17) / (17 × 0.72)
= 3001.9 / 12.24 = **245W**
P_total = 245 + 30 (payload) = **275W**

### Endurance by Battery Configuration

| Config | Energy (Wh) | Usable 80% (Wh) | Theoretical (h) | Practical (h) | Conservative (h) |
|--------|------------|------------------|-----------------|---------------|------------------|
| 4× 6S 33Ah 330 Wh/kg | 2930 | 2344 | 10.7 | **8.5** | **7.5-8.0** |
| 2× 12S 33Ah 350 Wh/kg | 2930 | 2344 | 10.7 | **8.5** | **7.5-8.0** |
| 4× Xingto 370 Wh/kg (est.) | ~3280 | ~2624 | 11.9 | **9.5** | **8.5-9.0** |
| 1× 12S 76Ah 330 Wh/kg (20 kg MTOW) | 3374 | 2699 | 10.5* | **8.4** | **7.5-8.0** |
| Future 450 Wh/kg (est.) | ~4000 | ~3200 | 14.5 | **11.6** | **10-10.5** |

*Higher MTOW (20 kg) → higher cruise power (~300W) partially offsets larger battery.

**Practical** = with 80% DoD. **Conservative** = with additional 10% real-world margin (wind, maneuvers, non-optimal cruise).

### Cross-Validation Against Reference Platforms

| Reference | MTOW | Energy | Endurance | Wh/min | Our scaled |
|-----------|------|--------|-----------|--------|------------|
| DeltaQuad Evo (standard) | 10 kg | 976 Wh | 4.5h | 3.62 | — |
| DeltaQuad Evo (record) | ~9 kg | ~1800 Wh | 8.9h | 3.37 | — |
| YUAV Y37 | ~17 kg | 2700 Wh | 8.5h | 5.29 | Our 18 kg @ 2930 Wh: extrapolated **8.0-8.7h** |

The YUAV Y37 cross-check (full carbon, 3.7m) extrapolates to 8.0-8.7h for our S2 FG design at 18 kg with 2930 Wh, accounting for the ~10% aerodynamic penalty of fiberglass vs carbon. This confirms our calculated range.

### Comparison to Draft 02

| Parameter | Draft 02 | Draft 03 | Change |
|-----------|----------|----------|--------|
| MTOW | 10 kg | 18 kg | +80% |
| Wingspan | 3.0m | 3.8m | +27% |
| Battery weight | 3.2 kg | 8.86 kg | +177% |
| Battery energy | 1001 Wh | 2930 Wh | +193% |
| Cruise power | ~170W | ~275W | +62% |
| Practical endurance | 3.5-4.7h | **8-8.5h** | +80-140% |
| BOM cost | $2,800-4,500 | $5,500-7,500 | +67% |

## BOM Cost Estimate (Per Unit, 8h Config)

| Component | Low Est. | High Est. | Notes |
|-----------|----------|-----------|-------|
| S2 fiberglass fabric | $250 | $500 | ~14 m² at $15-30/m² (40% more than 3m) |
| PVC foam core (Divinycell H60) | $160 | $300 | Wing + fuselage + tail |
| Epoxy resin + hardener | $120 | $230 | ~3.5-4 kg resin |
| CF spar material (tube + UD tape) | $80 | $150 | Longer spars for 3.8m |
| Aluminum spar joiners 7075-T6 | $50 | $100 | Larger, machined |
| Vacuum bagging consumables | $40 | $80 | |
| Motor (T-Motor U8 Lite or equiv.) | $120 | $200 | 700W class |
| ESC (60-80A) | $60 | $120 | |
| Folding propeller (16×10) | $20 | $40 | |
| Servos (6× for larger surfaces) | $80 | $160 | |
| Wiring, connectors, battery bus | $80 | $150 | More complex 4-battery wiring |
| **Batteries (4× Tattu 6S 33Ah 350)** | **$2,930** | **$2,930** | Retail price |
| RC receiver | $30 | $80 | |
| Telemetry radio | $100 | $300 | |
| Transport case / padded bag | $80 | $200 | Larger for 190cm wings |
| **Subtotal (airframe + propulsion + battery)** | **$4,200** | **$5,540** | |
| Nav camera: ADTI 26S V1 + 35mm lens | $1,890 | $1,890 | 26MP APS-C, mech. shutter, 21.6 cm/px at 2 km |
| AI camera: Viewpro Z40K 4K gimbal | $2,999 | $4,879 | 4K 20× zoom, 2.7 cm/px at 2 km |
| Pixhawk 6x + GPS | $300 | $500 | |
| **Total BOM (complete unit)** | **$9,389** | **$12,809** | |

With 2× 12S 33Ah instead of 4× 6S: battery cost rises to ~$3,800 (+$870).
With Xingto 370 Wh/kg: battery cost est. ~$3,000-4,000 but better endurance.

**Per-unit cost at batch of 5+**: **$10,500-14,500** (including cameras, tooling amortization)
**Per-unit cost first prototype**: **$13,500-17,000** (includes tooling)

Optional upgrade: swap ADTI 26S → ADTI 61PRO (+$940/unit) for 15 cm/px GSD if finer nav resolution needed.

## Battery Upgrade Roadmap

| Timeline | Battery Technology | Energy Density (pack) | Endurance (18 kg platform) | Availability |
|----------|-------------------|----------------------|---------------------------|-------------|
| **Now (2025-2026)** | Tattu/Grepow semi-solid 350 Wh/kg | ~331 Wh/kg | **8-8.5h** | ✅ Off-the-shelf |
| **Now (2025-2026)** | Xingto semi-solid 370 Wh/kg | ~350 Wh/kg | **9-9.5h** | ✅ Available (limited) |
| **Near-term (2026-2027)** | Tulip Tech Ampera solid-state | ~430 Wh/kg | **10-11h** | ⚠️ Shipping to select partners |
| **Near-term (2026-2027)** | Amprius SA102 silicon-nanowire | ~430 Wh/kg | **10-11h** | ⚠️ Pilot production |
| **Future (2027-2028)** | Tulip Tech Enerza / Amprius 500 | ~475 Wh/kg | **11-12h** | ❓ Announced, not volume |

### Solid-State 450 Wh/kg Cost Impact

Solid-state batteries (Tulip Tech, Amprius) are not yet priced publicly — both sell on custom quotes to defense/aerospace customers. Industry estimates for 2025-2026 production cost: $800-1,000/kWh. With small-volume aerospace/defense retail markup (1.5-3×), estimated retail: $1,500-2,500/kWh.

| Battery | Pack Wh/kg | Total Energy | Endurance | Battery Cost | Total UAV BOM | Delta vs Baseline |
|---------|-----------|-------------|-----------|-------------|--------------|------------------|
| Tattu semi-solid (baseline) | ~331 | 2930 Wh | 8-8.5h | **$2,930** | ~$6,500 | — |
| Solid-state 450 (low est.) | ~430 | 3810 Wh | 10-11h | **$5,700** | ~$9,300 | **+$2,800 (+43%)** |
| Solid-state 450 (mid est.) | ~430 | 3810 Wh | 10-11h | **$7,600** | ~$11,200 | **+$4,700 (+72%)** |
| Solid-state 450 (defense premium) | ~430 | 3810 Wh | 10-11h | **$9,500** | ~$13,100 | **+$6,600 (+100%)** |

Prices should converge toward production cost ($800-1,000/kWh → low estimate above) as Amprius scales 1.8 GWh contract manufacturing capacity and Tulip Tech ramps with Dutch MoD backing through 2026-2027.

**Design for upgradability**: The battery bay should accommodate the same physical volume regardless of chemistry. Start with Tattu semi-solid at 8-8.5h for $2,930. When solid-state packs become available in compatible form factor, drop them in for 10-11h — no airframe changes needed, just a battery swap.

## Modular Transport Specifications

| Dimension | Value (3.8m) | Value (4.0m, 3-section) |
|-----------|-------------|------------------------|
| Wing panel length | 190 cm (half-span) | 170 cm outer + 60 cm center |
| Wing panel chord | 28-30 cm | 28-30 cm |
| Wing panel thickness | 4-5 cm | 4-5 cm |
| Fuselage length | 110 cm | 110 cm |
| Fuselage width/height | 18-22 cm | 18-22 cm |
| Assembly time | < 12 minutes | < 15 minutes |
| Disassembly time | < 7 minutes | < 10 minutes |

**Pickup truck (2 planes, 3.8m design)**: All wing panels stack in one pile (190×30×20 cm = 4 panels × 5cm). Fuselages alongside (110×22 cm × 2). Total footprint: 190×110 cm < 198×130 cm. ✅

**Car trunk (1 plane, 3.8m)**: Tight but possible in larger sedans/SUVs. Two wing panels (190cm) require fold-down rear seats or diagonal placement. Fuselage fits easily. ⚠️ Borderline for sedans; SUV or wagon preferred.

## Hydrogen Fuel Cell — Assessment (Not Recommended)

Investigated as requested. While hydrogen offers dramatically higher endurance (15-17h), it is **not recommended** for this application:

| Factor | Assessment |
|--------|-----------|
| Endurance | ✅ 15-17h theoretical with IE-SOAR 2.4 + 10.8L tank |
| System weight | ⚠️ ~9.8 kg (FC 4.8 + tank 4.2 + regulator 0.3 + buffer 0.5) — similar to 4-battery pack but higher complexity |
| Cost | ❌ $25,000-40,000 per unit (FC module alone est. $15-25k) |
| H2 logistics | ❌ Compressed hydrogen (350 bar) supply chain in eastern Ukraine = extremely difficult. Requires specialized transport, hazmat protocols, compressor equipment |
| Radio transparency | ❌ H2 platforms (NOCTUA, Doosan) use CFRP to save weight, conflicting with RF requirement |
| Reliability | ⚠️ Fuel cells have 1000h life but are sensitive to contaminants and temperature extremes |
| Practical recommendation | Revisit only if (1) hydrogen infrastructure develops in theater, (2) RF transparency requirement is relaxed, or (3) endurance requirement exceeds 12h |

## Solar Augmentation — Assessment (Not Recommended)

| Factor | Assessment |
|--------|-----------|
| Available wing area | ~0.7 m² usable upper surface |
| Solar power at altitude | ~35-40W average (Ukrainian latitude, 22% efficient flexible panels) |
| Endurance gain | +1.0-1.5h theoretical, but -0.5h from panel weight → net +0.5-1.0h |
| Cost | +$500-1,500 per unit for flexible panels |
| Complexity | Adds MPPT controller, fragile surface, weather dependency |
| Recommendation | Not worth the cost/complexity for ~1h marginal gain |

## Testing Strategy

### Integration / Functional Tests
- Static wing load test: 3× max flight load at spar joiner (verify no failure at 3g with 18 kg MTOW)
- Wing joint cycling: 100× assembly/disassembly, verify no wear (critical at higher loads)
- RF transparency test: measure GPS signal through airframe skin (target: < 3 dB attenuation)
- Assembly time test: verify < 12 minutes from transport case to flight-ready
- Battery wiring test: verify 2S2P balancing, measure voltage sag under load, test fail-safe (single pack disconnect)
- Range/endurance test: fly at cruise until 20% reserve, measure actual vs predicted
- Payload integration: electronics function under vibration at 18 kg flight loads

### Non-Functional Tests
- Transport test: load 2 planes in pickup, drive 100 km on mixed roads, verify no damage
- Hard landing test: belly landing at 2.5 m/s descent (higher than Draft 02 due to heavier aircraft)
- Field repair test: wing skin puncture → FG patch + epoxy → airworthy in < 30 minutes
- Temperature test: battery + avionics at -10°C and +45°C
- Battery endurance test: 50 charge/discharge cycles on 4-battery 2S2P config, verify balanced degradation
- CG test: verify stable CG across all battery configurations (4-battery, 3-battery partial, 2-battery emergency)
- Emergency flight test: verify aircraft can fly safely on 2 batteries (reduced endurance) if 1 series pair fails

## Production BOM: 5 UAVs From Scratch (8h Config)

### A. One-Time Equipment & Tooling

Same as Draft 02 base equipment: $3,335. Add:
| Item | Qty | Unit Price | Total | Notes |
|------|-----|-----------|-------|-------|
| Larger mold materials (4m wing + fuselage) | 1 set | $900 | $900 | MDF plugs + tooling epoxy for 3.8m molds |
| Aluminum spar joiner machining (7075, 12 sets) | 1 | $600 | $600 | Larger joiners, CNC outsourced |
| Battery parallel bus bar / wiring jig | 1 | $100 | $100 | For consistent 2S2P assembly |
| **Equipment & Tooling TOTAL** | | | **$4,935** | |

### B. Raw Materials (5 UAVs + 20% waste)

| Item | Qty (5 UAVs + margin) | Unit Price | Total |
|------|----------------------|-----------|-------|
| S2 fiberglass fabric 6oz | 100 yards | $12.50/yard | $1,250 |
| PVC foam Divinycell H60 10mm | 24 sheets | $40/sheet | $960 |
| Laminating epoxy resin | 6 gallons | $125/gal | $750 |
| Epoxy hardener | 3 gallons | $80/gal | $240 |
| Carbon fiber tube (spar, 25mm OD, 2.0m) | 12 | $35 each | $420 |
| Carbon fiber UD tape 25mm | 50 m | $5/m | $250 |
| Vacuum bagging consumables | — | — | $400 |
| Misc hardware | — | — | $250 |
| **Materials TOTAL (5 UAVs)** | | | **$4,520** |
| **Per UAV materials** | | | **~$904** |

### C. Electronics & Propulsion (per UAV × 5)

| Item | Per UAV | ×5 Total |
|------|---------|----------|
| Motor (T-Motor U8 Lite or equiv.) | $150 | $750 |
| ESC (80A) | $80 | $400 |
| Folding propeller 16×10 (2 per UAV) | $40 | $200 |
| Servos (6× digital metal gear) | $150 | $750 |
| Nav camera: ADTI 26S V1 + 35mm lens | $1,890 | $9,450 |
| AI camera: Viewpro Z40K 4K gimbal | $3,500 | $17,500 |
| Pixhawk 6X Mini + GPS | $380 | $1,900 |
| RC receiver (TBS Crossfire) | $60 | $300 |
| RFD900x telemetry | $170 air × 5 + $350 GCS | $1,200 |
| Power distribution + BEC | $30 | $150 |
| Wiring, connectors, battery bus | $80 | $400 |
| **Batteries: 4× Tattu 6S 33Ah 350 (per UAV)** | **$2,930** | **$14,650** |
| **Electronics TOTAL (5 UAVs)** | | **$47,650** |
| **Per UAV electronics** | | **~$9,530** |

### D. Summary

| Category | Total | Per UAV |
|----------|-------|---------|
| A. Equipment & Tooling | $4,935 | $987 |
| B. Raw Materials | $4,520 | $904 |
| C. Electronics & Propulsion | $47,650 | $9,530 |
| D. Consumables & Misc | $1,200 | $240 |
| E. Labor (est. same structure as Draft 02, +20%) | $19,176 | $3,835 |
| **GRAND TOTAL (5 UAVs)** | **$77,481** | |
| **Per UAV (all-in, with labor)** | | **$15,496** |
| **Per UAV (materials + electronics, no labor)** | | **$11,661** |

The cost increase vs Draft 02 ($6,502/unit) is driven by cameras (+$2,391/unit: ADTI 26S replaces ADTI 20L, Z40K replaces A40 Pro), batteries (+$2,200/unit), and larger airframe (+$250/unit). Optional: swap to ADTI 61PRO (+$940/unit) for 15 cm/px nav GSD.

## Risk Assessment

| Risk | Impact | Probability | Mitigation |
|------|--------|------------|-----------|
| S2 FG airframe heavier than estimated → MTOW exceeded | Reduced endurance | Medium | Build weight tracking into construction; accept 18.5 kg MTOW if needed |
| 4-battery wiring complexity → connector failure | Loss of power pair | Low | Redundant connectors; test fail-safe on 2 batteries; parallel bus bar design |
| Semi-solid battery supply disruption | Cannot build | Low | Multiple suppliers (Tattu, Grepow, Xingto) |
| L/D lower than 17 in practice | Endurance drops to 7-7.5h | Medium | Use Xingto 370 Wh/kg for margin; optimize airfoil selection (SD7037 or AG series) |
| Wing flutter at 3.8m span | Structural failure | Low | Ground vibration test; CF spar sized for 1.5× flutter speed margin |
| CG shift with 4 battery packs | Controllability | Low | Fixed battery bay positions; CG calculated for all configurations |

## References

1-34: See Draft 01 and Draft 02 references (all still applicable)

Additional sources:
35. DeltaQuad Evo 8h55m record: https://uasweekly.com/2025/06/27/deltaquad-evo-sets-record-with-8-hour-flight-endurance-for-electric-vtol-uas-milestone/
36. Tulip Tech batteries: https://tulip.tech/batteries/
37. DeltaQuad Evo specs: https://docs.deltaquad.com/tac/vehicle-specifications
38. DeltaQuad Evo performance calculator: https://evo.deltaquad.com/calc/
39. YUAV Y37 specs: https://www.airmobi.com/yuav-y37-a-new-standard-in-long-endurance-vtol-fixed-wing-uavs/
40. YUAV Y37 product page: https://www.airmobi.com/product/yuav-y37-3700mm-vtol-fixed-wing-uav-pnp/
41. Tattu 350 Wh/kg 6S 33Ah: https://tattuworld.com/semi-solid-state-battery/semi-solid-350wh-kg-33000mah-22-2v-10c-6s-battery.html
42. Tattu 350 Wh/kg 12S 33Ah: https://tattuworld.com/semi-solid-state-battery/semi-solid-350wh-kg-33000mah-44-4v-10c-12s-battery.html
43. Tattu 330 Wh/kg 12S 76Ah: https://tattuworld.com/semi-solid-state-battery/semi-solid-330wh-kg-76000mah-44-4v-10c-12s-battery.html
44. Xingto 370 Wh/kg battery: https://www.xtbattery.com/370wh/kg-42v-high-energy-density-6s-12s-14s-18s-30ah-semi-solid-state-drone-battery/
45. Amprius SA102 450 Wh/kg: https://amprius.com/the-all-new-amprius-500-wh-kg-battery-platform-is-here/
46. Amprius UAV selection: https://amprius.com/amprius-high-power-silicon-batteries-selected-by-esaero-to-power-next-generation-uavs/
47. NOCTUA hydrogen UAV: https://noctua.ethz.ch/technology
48. IE-SOAR 2.4 fuel cell: https://www.intelligent-energy.com/our-products/ie-soar-fuel-cells-for-uavs/ie-soar-2-4/
49. IE-SOAR specs (retail): https://shop.thebioniceye.co.uk/products/ie-soar-2-4kw-hydrogen-fuel-cell
50. Doosan DS30W specs: https://www.doosanmobility.com/en/products/drone-ds30
51. Cellen hydrogen refueling: https://cellenh2.com/reinventing-hydrogen-refueling-for-drones/
52. Tattu battery catalog (pricing): https://rcdrone.top/collections/tattu-semi-solid-state-battery
53. Tattu 76Ah pricing (FlexRC): https://flexrc.com/product/tattu-semi-solid-state-330wh-kg-76000mah-10c-44-4v-12s1p-lipo-battery-pack-with-qs12-s-plug/
54. JOUAV CW-80E: https://www.jouav.com/products/cw-80e.html
55. Discus 2b 4m glider: https://icare-rc.com/discus2b_4m.htm
56. Pickup bed dimensions: https://kevinsautos.com/faq/what-are-the-dimensions-of-a-65-foot-truck-bed.html
57. Tulip Tech Dutch MoD partnership: https://www.tulip.tech/news/

## Related Artifacts
- Previous drafts: `solution_draft01.md` (CFRP), `solution_draft02.md` (S2 FG, 3m, 10 kg)
- Research artifacts: `_standalone/UAV_frame_material/00_research/UAV_frame_material/`
