A propulsion idea for interstellar travel just gained a steering concept
Light sails have long been one of the most compelling concepts for reaching extreme distances in space. Instead of carrying heavy propellant, a sail could be pushed by light itself, especially by powerful lasers. The appeal is simple: for very long journeys, reducing onboard mass may be one of the few realistic paths to meaningful speed.
The problem has never just been movement. It has also been control. A sail that can be pushed is useful, but a sail that can be guided is far more valuable. New Scientist reports that researchers may now have taken a small but notable step toward that goal by developing tiny devices called metajets, which can use light not only to move but also to influence direction.
The work comes from researchers including Kaushik Kudtarkar at Texas A&M University. Their central insight is that light can do more than transfer momentum through reflection. By designing a structured material that refracts light in carefully controlled ways, they can generate forces in more than one direction at once.
How the metajet works
The device described in the report is a metasurface, an extremely thin material engineered to manipulate light. In this case, the researchers effectively reversed the usual framing. Instead of focusing only on how the material changes the light, they examined how the light changes the motion of the material.
The metajet is textured with a series of tiny pillars. The size and pattern of those structures determine how incoming light is steered as it passes through or interacts with the surface. Because momentum is exchanged in the process, changing the path of the light changes the force acting on the material itself.
That is what makes the concept interesting for steering. If the geometry of the surface can create different directional responses, then a light-driven object might be designed to do more than simply accelerate forward. It could potentially correct, orient, or maneuver without conventional moving parts.
The device itself is extraordinarily small, about 0.01 millimetres across according to the report. At that scale, the experiment is not a prototype for a starship sail. It is a proof of principle showing that engineered surfaces can convert illumination into controlled motion.
What the team demonstrated
To test the idea, the researchers placed the silicon device in water and shone a laser on it while tracking its movement under a microscope. The result was motion in two ways at once: the metajet both levitated and moved horizontally. New Scientist reports a maximum speed of around 0.07 millimetres per second.
Those numbers are modest, but they are not the real story. The significance is the combination of lift and lateral movement produced through surface design. In other words, the experiment shows controllable behavior emerging from the optical properties of the material itself.
Kudtarkar told New Scientist that now that the forces on the device are understood, researchers can change the metasurface design to steer it in whatever way they want. That is the kind of engineering statement that matters more than the raw speed figure. It suggests a design space rather than a one-off effect.
Why light-sail advocates should care
For light sails, steering is a central challenge. Sending a craft across enormous distances requires more than thrust. Tiny orientation errors can become massive navigational deviations over time. Any method that allows a sail to respond predictably to light pressure, especially without adding bulky control hardware, could become important.
The report notes that metasurfaces that change shape over time already exist. If that capability were combined with light-driven steering, future sails might actively alter how they respond to illumination. That could open the door to more precise handling during acceleration or course correction.
There is still a large gap between a microscopic demonstration in water and a full-scale space application. Space introduces vacuum conditions, extreme temperature swings, radiation, and the need for long-duration stability. The article does not claim those problems are solved. What it does suggest is that one piece of the puzzle, directional control through structured optical response, now has a more concrete experimental basis.
The implications reach beyond space
The researchers also see possible biomedical applications. New Scientist reports that such devices could potentially push drugs to specific locations. Lasers are already used in some contexts for targeted manipulation, but direct heating can damage sensitive molecules. In the metajet concept, the structured device rather than the payload would bear the direct optical interaction, potentially reducing that problem.
That dual-use character is common in advanced materials research. A concept developed in the context of ambitious space travel can turn out to be useful in medicine or microscale engineering. In both cases, the core capability is the same: turning carefully shaped light-matter interactions into controllable mechanical behavior.
The team is now looking to make the device work with different wavelengths of light, especially the broad spectrum of sunlight. That goal matters because a practical light sail may not always rely on a single highly controlled laser environment. Compatibility with sunlight would widen the possible architectures for future propulsion systems.
No one should confuse this with immediate interstellar travel. But it does represent the kind of enabling advance that big ideas often depend on. Spaceflight revolutions are built from small, specific breakthroughs in control, materials, and energy transfer. Metajets may be one of those building blocks: tiny structures that point toward a future in which sails pushed by light are not just fast, but steerable.
- Researchers built a tiny metasurface device that can levitate and move horizontally when hit by laser light.
- The result suggests light-driven objects could eventually be steered, not just pushed forward.
- The concept could matter for both interstellar light sails and targeted biomedical applications.
This article is based on reporting by New Scientist. Read the original article.
Originally published on newscientist.com
