gps-denied-onboard/_standalone/UAV_frame_material/01_solution/solution_draft01.md

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