Moulinsart

Moulinsart is Projet Sola's fourth prototype and the core aircraft of this EPFL student solar UAV project. It is designed to validate a long-endurance solar plane architecture while keeping the platform useful for aerodynamic studies, energy-management experiments and onboard technology testing.

Architecture Systems Validation

Rendering of Moulinsart, Projet Sola Prototype IV — platform render **Prototype IV**

endurance target 8 h

radio range 15 km

solar cells 44

target mass 3 kg

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Overall architecture

A solar aircraft shaped as a flying laboratory.

The prototype is designed as a complete system: lightweight structure, solar cells, battery storage, power-conversion electronics, flight controller and communication links. Each subsystem must remain accessible, replaceable and measurable so flight tests can lead to fast engineering iterations.

Wing-integrated solar cells to maximise exposed collection area.
Biocomposite and balsa structure to reduce mass without losing stiffness.
Onboard architecture built for measurement, diagnosis and iteration.

Feasibility model and aerodynamic baseline for Prototype IV — feasibility model / aerodynamic baseline

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Onboard systems

What makes Moulinsart measurable.

MPPT module used for solar power management

power / mppt

Extract usable power.

The MPPT tracks the solar panels' maximum power point to maintain useful efficiency despite changes in irradiance, aircraft attitude and electrical load.

Prototype IV avionics board and electronics production

control / avionics

Centralise flight data.

The flight controller aggregates sensor inputs, stabilises the aircraft and turns each test into an exploitable dataset for diagnosis and tuning.

Structural view of the Moulinsart fuselage

structure / fuselage

Carry systems without compromising endurance.

The airframe must preserve aerodynamic efficiency while leaving enough integration margin for batteries, boards, wiring, fixtures and future test payloads.

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Structural reading

xray mesh

A stylised view of the geometry that communicates the aircraft's internal logic without locking the presentation inside a third-party viewer.

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Field validation

Prototype IV flight test — flight test / solar cells removed

Validate progressively before full solar flight.

Validation is organised in steps to isolate risk: structural behaviour, stability, avionics, communication and finally solar integration. This avoids confusing an energy issue with an aerodynamic, control or structural issue.

Dimensions and feasibility model established.

Structural and electronic production moving toward consolidation.

Non-solar flights used to validate baseline behaviour.

Final target: long-endurance flight powered by solar cells.

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Why this prototype matters

Moulinsart concentrates the lessons of the previous prototypes.

The value of Prototype IV is not only its target performance. It is also the method behind it: design, measure, fly, understand and improve. The drone overview gives the key figures; this technical file explains the engineering logic behind those choices.