What if a spacecraft did not need a large engine or huge amounts of fuel to move through space? What if it could instead use the tiny push delivered by sunlight?
That is the idea behind light sails—ultra-thin sails that use the momentum of photons to produce thrust. Now, students at Cornell University have taken this technology a step further by testing extremely small, free-flying light sails designed to work with tiny spacecraft called ChipSats.
The student-led missions, called Alpha CubeSat and Sailing to the Stars, successfully demonstrated important technologies in low Earth orbit and aboard the International Space Station (ISS). The experiments could help make future spacecraft smaller, cheaper and potentially capable of exploring destinations far beyond Earth.
A spacecraft powered by light
Traditional spacecraft depend on chemical or electric propulsion systems to change their speed and direction. These systems require fuel, engines and supporting hardware, all of which add mass.
A light sail takes a completely different approach.
Sunlight is made of photons, tiny packets of electromagnetic energy. Although photons have no rest mass, they carry momentum. When they strike a reflective surface, they transfer a very small amount of momentum to it.
One photon provides an almost unnoticeable push. But a huge number of photons continuously hitting a large, lightweight sail can create a useful force.
Unlike a conventional rocket, a light sail does not need to carry propellant to produce this force. Over long periods, the continuous push from sunlight can gradually increase a spacecraft's velocity.
The Cornell experiments were designed around this principle.
A sail smaller than a pizza box
The sails developed by students in Cornell's Space Systems Design Studio (SSDS) are only slightly larger than a pizza box.
That might sound too small to be useful, but their real advantage comes from the spacecraft architecture surrounding them.
The sails can be folded using an origami-like design so they fit inside a CubeSat during launch. Once in space, they unfold and separate from the main spacecraft.
This creates a remarkably compact system.
Instead of carrying a large conventional spacecraft with the sail permanently attached, the tiny sail can become a free-flying spacecraft after deployment.
At the heart of this concept are ChipSats—extremely small spacecraft weighing only grams and small enough to fit in the palm of a hand.
These miniature spacecraft can provide communications, electronics and steering functions while adding very little mass.
Alpha CubeSat puts the technology into orbit
The first major experiment was Alpha CubeSat, a 1U CubeSat designed to deploy a light sail in low Earth orbit.
Alpha launched to the International Space Station in late 2025 aboard NG-23. After deployment into orbit, the spacecraft successfully released its light sail.
One of the most interesting achievements involved the tiny ChipSat carried by the system.
Using the TinyGS network, amateur radio operators around the world were able to communicate with the miniature spacecraft and receive information from it.
According to mission lead Joshua Umansky-Castro, the mission represented an important milestone because the tiny spacecraft transmitted complete data packets from orbit to the ground.
The ChipSat eventually stopped operating as atmospheric drag caused it to rapidly lose altitude. However, the CubeSat itself continued operating until it deorbited in May 2026.
During that time, Alpha confirmed that its sail deployment worked and also completed several additional technology demonstrations.
More than just a light sail
Alpha CubeSat carried several experimental technologies.
One demonstration tested a magnetorquer-only spin-stabilization algorithm. Magnetorquers use Earth's magnetic field to control spacecraft rotation, avoiding the need for conventional propulsion systems for certain attitude-control tasks.
The spacecraft also used commercial off-the-shelf avionics, showing that relatively inexpensive components can potentially be used for small space missions.
Another milestone was the first flight of a RockBLOCK Iridium modem in this type of application, providing satellite-based communications.
The spacecraft's chassis was also fully 3D-printed, demonstrating how additive manufacturing can simplify the construction of small spacecraft.
Perhaps the most unusual experiment involved holographic image message plaques sent into space.
Together, these demonstrations showed that a very small spacecraft can serve as a platform for testing multiple technologies without requiring the budget or infrastructure of a large satellite mission.
Six sails tested aboard the space station
The second experiment, Sailing to the Stars, approached the problem from a different angle.
Instead of immediately sending the sails into free flight, students tested the deployment of six light sails in the microgravity environment of the International Space Station.
The experiment launched aboard Crew-11 in late 2025.
The students recorded video and collected data from inertial measurement units (IMUs) to study exactly how the sails behaved while unfolding.
That information is important because deploying a lightweight, flexible structure in space is not as simple as opening an umbrella.
A sail can rotate, wobble, twist or interact with its deployment mechanism. Understanding these movements is essential before attempting more ambitious missions.
Spacecraft made like LEGO
The Sailing to the Stars team also tested two different CubeSat-scale deployment mechanisms.
Both designs were made almost entirely using 3D-printed modular components, described by the team as "CubeSat-LEGO."
The experimental systems used spin stabilization and even repurposed laptop hard-disk-drive reaction wheels to control their motion.
The systems were commanded using TV remote controls, highlighting the highly experimental and student-driven nature of the project.
By comparing the two deployment mechanisms, the team could determine which design produced more stable motion.
Those results can influence the design of future light-sail missions where reliable deployment will be critical.
A project built by students
Perhaps the most remarkable part of these missions is who built them.
The spacecraft were designed, assembled and tested by students at Cornell.
The original concept for Alpha CubeSat can be traced back to a high school student who proposed it through the Museum of Science Fiction's International CubeSat Design Competition.
Since 2016, more than 150 students have contributed to Cornell's spacecraft projects. According to the project team, more than half of those students later went on to internships or jobs in the aerospace industry.
For the students involved, the missions provided something difficult to replicate in a classroom: the experience of taking an idea from a concept on paper all the way to an actual spacecraft operating in space.
Could tiny sails eventually reach other worlds?
The successful experiments are only an early step.
Future ChipSat-sail missions could investigate active steering, orbit raising and laser propulsion.
Solar light sails could potentially use sunlight continuously to change their trajectories, while much more powerful lasers could provide an even stronger source of photon pressure.
This connects the technology to one of the most ambitious ideas in space exploration: sending tiny spacecraft to other star systems.
Projects such as Breakthrough Starshot have explored concepts in which extremely lightweight spacecraft could be pushed by powerful laser beams to a significant fraction of the speed of light.
At those speeds, tiny probes could theoretically travel to nearby stars within decades rather than the thousands of years required by conventional spacecraft.
That remains an enormous engineering challenge, and interstellar missions are far beyond what these Cornell experiments have demonstrated.
But the basic philosophy is already being tested: make spacecraft smaller, lighter and more efficient, and find ways to move them without carrying large amounts of fuel.
The Cornell missions show how far that philosophy can go—even when the spacecraft is small enough to fit in your hand.
From a high-school idea to student-built spacecraft operating in orbit, these experiments demonstrate that the future of space exploration may not always belong to enormous rockets and giant spacecraft.
Sometimes, the next step toward the stars may begin with a tiny satellite and a sail no bigger than a pizza box.
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