Serenity UAV

A flight-worthy, security-hardened EDF tilt-rotor replica of the Firefly-class ship Serenity

"Can't stop the signal, and can't take the sky from me."

Isometric render of the Rev S assembly — port/bow/dorsal view. Predates the Rev S1g wing spar and Rev S4c nacelle geometry; re-render pending (see TODO.md §0.10).

Overview

Serenity UAV is a fully functional electric ducted fan (EDF) tilt-rotor aircraft engineered as an actual physical build of the Firefly-class transport Serenity (Joss Whedon, 2002) — every component here is fabricated or procured, not conceptual. Four canonical CF-PETG-printed hull sections carry two tilting EDF nacelles, a belly cargo bay with powered winch and clamshell doors, and an 8-node cooperative avionics architecture with PACE (Primary/Alternate/Contingency/Emergency) failover across every flight-critical function.

The design is held to the same rigor as a certifiable aircraft: real mass/CG/load budgets (no "TBD" specs), FAA/FCC/NIST/IEC standards vetting on every design decision with any effect beyond cosmetics, redundant power and control paths throughout, and a zero-trust security model — every onboard message is signed, authenticated, and logged to hardware-enforced non-executable storage — engineered to keep operating correctly inside a 500 W/m² RF field. Avionics, comms, and software are built for reuse across other UAV/UGV/USV platforms, not just this airframe. See AGENTS.md for the full authoritative project policy that governs every design decision in this repository.

Nominal Mission Profile Take off VTOL. Land vertically with cargo bay open and load and secure a 4″ × 3″ × 3″, 8 oz payload. Take off VTOL with payload. Fly into a 500 W/m² broadband RF environment. Lower and release the payload from the cargo bay onto a platform. Identify a 4″ × 3″ × 3″ payload on a moving platform. Synchronize flight with the platform. Attach the payload to the hoist and lift it from the platform. Pull the payload into the cargo bay and close the clamshells. Exit the hazardous environment and return to origin. Throughout the mission, the aircraft shall also: Identify, categorize, log, and report rogue or unauthorized C2 commands or malicious logic from any transmitter, authorized or not. Identify unauthorized or unsafe behavior from any onboard compute node. Isolate the affected node(s), gracefully fail over its functions, and log/report to ground control — all while maintaining safety of flight.

Specifications Parameter Value Length 24.0 in (609 mm) Wingspan 19.1 in (486 mm) Height 7.93 in (201.5 mm) AUW — Phases 5–10 (nacelles only) ~8.62 lbm (3,911 g) AUW — Phase 11 (full system) ~9.42 lbm (4,273 g) Payload capacity (minimum) 8.0 oz (226 g) in a 4″ × 3″ × 3″ bay Thrust — nacelles only (hover) 9.84 lbf (4,464 g) Thrust — Phase 11 rear EDF (cruise) ~2.81 lbf (1,275 g) net after RCS bleed T/W — nacelles only (hover) ≈ 1.14 (VTOL hover capable; margin corrected 2026-08-22, see TODO.md §0.10.1) T/W — Phase 11 (hover, nacelles only) ≈ 1.04 (rear EDF adds mass but is forward-thrust only) Compute 8× PocketBeagle 2 Industrial (AM6254), PACE failover Onboard buses CAN FD, MIL-STD-1553C, RS-485, Ethernet RSTP ring External comms Five C2 links: Wi-Fi 5 GHz, Zigbee 2.4 GHz, mLRS, SiK/MAVLink 915 MHz, 49 MHz AX.25 EMI design objective 500 W/m² RF field, correct operation Mass/thrust/T-W figures are the corrected 2026-08-22 baseline (the earlier 1.61 hover T/W used a stale 2,768 g AUW) and remain provisional until the bottom-up AUW ledger recompute closes — see current-specification/README.md and docs/WBS.md §0.10.1.

Project Status (2026-10-07)

Rev T, design and PCB layout. Nothing is fabricated or assembled; the physical build has not started. The path to first flight is in docs/FIRST_FLIGHT_READINESS.md; open work is in TODO.md, generated from the full record in WBS.md.

Area	State
Airframe	SCAD shells at Rev S baseline, carried into Rev T; STL re-exports pending after the TACCO 60 × 35 mm change; cargo-shell mesh defect open
Nacelles	50 mm Rev S4c is current; 64 mm tandem-EDF redesign (NAC-64-SERVO-01) with a servo-driven nozzle is designed and fit-closed, with pivot, CFD, mass, and bench gates open
Avionics PCBs	Pilot and TACCO placed with ERC 0 / DRC 0 before routing, on corrected 4.80 mm PB2 rails; routing and Gerbers open. Flight Engineer, Observer, and Commo Rev T need further PCB work
Buses	Fleet MIL-STD-1553C via the Holt HI-6138 on every Pilot and TACCO (2026-09-28)
Comms	mLRS on a bare STM32WLE5JC; Wi-Fi USB module selection is a fab blocker; Commo becomes one standalone node (Rev T, 2026-09-29)
Firmware	serenity-cn Phase 6 done; serenity-fc Phase 6 stub; Phase 7 open
Ground station	Skipper in design; ground-side radio loadout decision open
BOM	bom_revT published 2026-09-28; avionics rows lag the 2026-10 PCB changes
Build guide	Hand-drawn pre-Rev-T art; rebuild open (task 1.5.6)

Subsystems

Airframe Four-section CF-PETG printed hull (head, cargo, middle, rear) with high-lift wings, hollow-walled and foam-filled to the canonical Firefly outer mold line. Rev S1g gave the wing a fixed, bonded 20×16.3 mm carbon-fiber spar as its primary bending member, replacing the earlier rotating-shaft design. Airframe README →	Landing Gear Four corner legs pair a rigid CF-PETG post with spring and ductile wire braces, giving a deliberately progressive, field-replaceable failure mode rated for a 6 ft full-AUW drop. Landing Gear Analysis →
Nacelles Two tilting pods each carry a tandem 50 mm EDF pair behind an 11-fin stator, with a variable-area nozzle scheduled on measured tilt (0°–145° pivot) and driven by one sub-micro servo per pod. Rev S4c hollowed the pods (−179 g/pair) and added hinged ESC bays with flush access covers on a 4×90° motor pattern; a 64 mm tandem-EDF redesign is in progress. Nozzle-Drive Trade Study →	Powerplant Four nacelle EDFs give 9.84 lbf combined hover thrust at a T/W of ≈1.14, fed by a 6S LiPo through the EMI-hardened Flight Engineer power distribution board. Power Distribution →
Avionics Eight PocketBeagle 2 Industrial nodes in four PACE-redundant stacks handle flight control, comms, and payload functions, all with 5 kV galvanic isolation, TPM-backed signed logging, MIL-STD-1553C, and a standalone Commo radio node (Rev T), plus the Skipper ground control station. Avionics README →	Bow Sensor Suite The forward Observer node — camera, Time-of-Flight array, and an eye-safe laser indicator — in the nose pod handles obstacle avoidance and rough size/orientation sizing of the mission payload. Observer Board →
Cargo Handling — Observer A belly clamshell cargo bay with a powered winch and hoist loads/releases an 8 oz payload in flight, guided by the downward-facing Observer node for close-in 3D imaging of the payload. Cargo Winch Specification →

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Table of Contents

• Project Status
• Authoritative Project Instructions
• References
• License
• Attribution
  • Component License Map
  • What This License Covers
  • Patent Notice
  • Forensic Evidence Integrity Note

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Authoritative Project Instructions

The canonical workspace instructions and design policy are maintained in AGENTS.md. All contributors and automated tools (including AI assistants) shall follow the requirements and standards documented there (coding style, fabrication specs, licensing, and attribution). CLAUDE.md is a one-line pointer to the same file, kept for tooling that looks for that name.

The Nominal Mission Profile and Specifications above are the current design baseline. Full engineering detail for each subsystem lives in that subsystem's own README/doc — see the link on each card in Subsystems above. The narrative that used to live directly in this file (full Airframe/Powerplant/Avionics/Cargo Handling write-ups) is preserved verbatim, for historical reference, in archives/root-readme-deep-dive-2026-08-03/.

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References

• Design conversation: claude.ai/share/a1e3900e-d2bf-4690-ba63-25178e7de666
• Latest design revision BOM: current-specification/bom_revT.json (Rev T, 2026-09-28)

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License

Licensed by Steve Griffing, PE(CSE), CISSP-ISSEP, CPP, according to what each file produces:

• Hardware — and any code that defines, creates or renders hardware (OpenSCAD, KiCad files and scripts, FreeCAD, Blender, G-code/slicer profiles, and tools that write or render meshes/CAD/PCB) — CERN-OHL-W 2.0 (SPDX CERN-OHL-W-2.0). Full text: LICENSE (root) / LICENSES/CERN-OHL-W 2.0.
• Code whose end result is software or firmware (firmware, device trees, ground software, analysis/verification/CI tools) — MIT (SPDX MIT). Full text: LICENSES/MIT.
• Documents (Markdown, text, specifications, build guides, and all images — SVG, PNG, JPG, WebP, including renders produced by hardware tools) — CC BY-SA 4.0 (SPDX CC-BY-SA-4.0). Full text: LICENSES/CC-BY-SA 4.0.

See docs/attribution_and_licensing.md for the full policy, the per-subsystem LICENSE federation map, and the CERN-OHL-W "Available Component" treatment of upstream canonical-reference geometry. Revision T, September 2026.

Attribution

"Serenity Tiltrotor Drone Project — hardware CERN-OHL-W 2.0, software MIT, docs CC BY-SA 4.0, based on: · Serenity Firefly-class hull by misubisu (thingiverse.com/thing:7330462, CC BY-SA 4.0) · Variable-area EDF nozzle by BamJr (thingiverse.com/thing:2991269, CC BY 4.0) Include a link to the applicable license and indicate if changes were made."

Component License Map

Component	Original Author	Source	License	Derivative Notes
Hull	misubisu	thingiverse.com/thing:7330462	CC BY-SA 4.0 (Available Component under CERN-OHL-W 2.0)	Scaled to 24 in, hollowed to 0.079 in (2.0 mm) CF-PETG shell, foam-filled
Nozzle mechanism concept	BamJr	thingiverse.com/thing:2991269	CC BY 4.0	Iris petal concept reference; all Rev O/P/Q nozzle geometry original
Design (hardware/CAD/PCB)	This project	—	CERN-OHL-W 2.0	All original work: PCBs, mechanical/CAD, wiring
Design (docs/code/scripts)	This project	—	CC BY-SA 4.0	Firmware spec, tooling, build guides, this document

What This License Covers

Covered under CERN-OHL-W 2.0 (hardware):

• 3D-printable hull, nacelle, and nozzle design files (STL/SCAD/FCStd)
• PCB schematics and Gerber files for Pilot, TACCO, Flight Engineer, Commo, and Observer
• Circuit diagrams, pinout tables, and wiring specifications
• Mechanical drawings and assembly specifications
• Any derived hardware shall carry CERN-OHL-W 2.0 (or a compatible license) and attribute all upstream authors

Covered under CC BY-SA 4.0 (documentation, code, scripts, non-hardware drawings):

• Firmware architecture specifications and algorithm descriptions
• This design document in all its revisions (A–R and beyond)
• Build automation/tooling scripts and non-hardware SVG diagrams
• Any derived works shall carry CC BY-SA 4.0 and attribute all upstream authors

Not covered / separate terms:

• Third-party commercial components (EDFs, ESCs, PocketBeagle 2, etc.) — their own terms
• SiK radio firmware — GPL-3.0
• ArduPilot / QGroundControl — GPL-3.0
• tpm2-tools / tpm2-tss — BSD-2
• CPLD Verilog write-blocker firmware — separately MIT licensed
• Proprietary flight controller firmware (your compiled code) — your terms
• FAA/ICAO regulatory compliance is YOUR responsibility as operator

Patent Notice

This license does NOT grant rights to any patents held by component manufacturers or the design authors. The design uses standard open hardware interfaces (CAN FD, Ethernet, SDIO, SPI, I²C, MAVLink). If you commercialise products based on this design, conduct your own freedom-to-operate analysis. The write-blocker CPLD design implements append-only log enforcement consistent with log data protection principles in NIST SP 800-92 §4.4.2 [REF-NIST-004]; no patent claims are made on the implementation.

Forensic Evidence Integrity Note

The write-blocker and NX enforcement hardware described in this design are intended to support operational log integrity, not forensic evidence collection. They implement log data protection principles consistent with NIST SP 800-92 §4.4.2 [REF-NIST-004]. They are NOT certified forensic tools under NIST CFTT (Computer Forensics Tool Testing) Program specifications or SWGDE (Scientific Working Group on Digital Evidence) standards. Do not use this design as the sole mechanism for evidence preservation in legal proceedings without independent verification of the implementation against your jurisdiction's evidence handling requirements.