Lightsail propulsion for very high speed space travel
Design Proposed
Lightsail prototype device and experimental characterization platform. a, Microscope image of the fabricated 50- nm-thick lightsail prototype device based on a spring-supported silicon nitride membrane. b, The operating principle of the common-path interferometer with high immunity to ambient noise. The unmodulated (DC) probe laser beam is split into two beams (−1 and +1) using a diffractive beam splitter (DBS) and subsequently focused onto the microscope’s image plane. This results in two closely spaced, nearly diffraction-limited spots, with one positioned on the pad and the other on a reference area (silicon nitride on silicon substrate). The reflected laser beam undergoes phase modulation corresponding to the pad’s out-of-plane motion at frequency f. c, Microscope image of the detection and reference beams on the sample plane. d, Measured timeresolved pad displacement bandpass-filtered around the drive frequency. The motion is in phase with the incident drive signal, confirming operation in the quasi-static regime. e, The experimental setup comprises three parts: an excitation path with a pump laser beam from an Ar-ion laser (514 nm) modulated in intensity using feedback-controlled acousto-optic modulator (AOM), a detection path based on a common-path interferometer with a probe laser beam from a stabilized He-Ne laser (633 nm), and a vacuum stage with ultra-high vacuum (5×10-9 mbar) on an inverted microscope platform containing the lightsail prototype. The drive frequency is set to 4 kHz, below the fundamental resonance of the lightsail at 9.4 kHz. Collimation of the excitation beam on the pad is achieved by focusing the beam onto the back-focal plane of the objective, with its incidence angle controlled by a linear translation stage
Details about LightSail
Light sail propulsion uses radiation pressure from light—either sunlight or powerful laser beams—to push a lightweight, ultra-thin sail. The momentum of photons (light particles) imparts a tiny force on the sail, gradually accelerating it over time. Unlike conventional rockets, which rely on fuel, light sails achieve propulsion purely through the transfer of momentum from photons.
- Solar Sails: Utilize sunlight as the propulsion source. Since sunlight is weaker than lasers, solar sails accelerate more slowly and are mainly useful within the Solar System.
- Laser-driven Lightsails: Use high-powered lasers focused on the sail from Earth or space-based stations, enabling rapid acceleration to a significant fraction of the speed of light. This method is being explored for interstellar travel, such as in the Breakthrough Starshot initiative.
More Details
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Materials: Light sails must be ultra-thin, lightweight, and highly reflective. Current research explores materials like silicon nitride membranes, which provide high reflectance and thermal stability.
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Acceleration: A powerful laser beam, typically in the megawatt per square centimeter range, can push a light sail to relativistic speeds (a significant fraction of the speed of light).
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Challenges: Stability, beam alignment, heat dissipation, and potential damage from space dust are major concerns that need to be addressed before practical implementation.
It can be used in
- Interstellar Exploration: Light sails could send small probes to nearby exoplanets, such as Proxima Centauri b, within decades instead of centuries.
- Fast Space Missions: These sails could provide rapid travel within the Solar System, reducing transit times for exploration missions to Mars, the outer planets, and even asteroids.
- Satellite Maneuvering: Light sails could be used for small adjustments in orbit without requiring fuel, extending satellite lifespans.
- Space Debris Removal: The technology could potentially help deorbit defunct satellites or space debris.
Sources & citation
Michaeli, L., Gao, R., Kelzenberg, M.D. et al. Direct radiation pressure measurements for lightsail membranes. Nat. Photon. (2025). https://doi.org/10.1038/s41566-024-01605-w