Thermal radiation carries momentum too. Graphene-assisted control of infrared emission opens a distinct question: can a useful, controllable recoil be engineered?
Conceptual radiation balance · no Metric Flight emitter built
Equal opposing emission lobes cancel their lateral momenta in this idealized example.
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A steered emission peak is only part of the answer.
To predict recoil, integrate escaping radiation over every direction and wavelength. Symmetric lobes can cancel sideways momentum even when their individual peaks move.
A demonstrated optical ingredient
A 2024 experiment used a graphene-integrated metasurface to change the emission angle in a narrow infrared band around 6.61 μm. The measured tuning was about 16°; larger ranges were numerical design predictions. It demonstrated controllable thermal emission, not a measured spacecraft propulsion system.
What produces the recoil
The force depends on the vector sum of escaping photon momentum. If equal powers leave in exactly opposite directions, their momentum contributions cancel. If the full emission pattern is asymmetric, a net recoil can result. Nearby reflectors, other device surfaces and the environment must be included in the balance.
The heat has to come from somewhere
An onboard thermal emitter needs a heat source or stored energy. Electrical power, absorbed sunlight or existing waste heat could be candidates in a specified architecture. None is unlimited. A system that uses waste heat must also preserve the spacecraft’s thermal requirements, and gate control adds its own electrical budget.
A hard power scale
The upper bound for perfectly collimated escaping radiation is P/c: 100 W corresponds to about 0.334 μN. Broad angular emission or cancellation lowers the useful component. This makes precision torque or tiny force adjustments more plausible targets than high thrust. That is a research inference, not a demonstrated graphene application.
Our next modeling question
Build a measured angular and spectral emission map for each control state, then calculate the total force and torque. Include the back surface and support. Only after that budget predicts a resolvable signal should a mechanical test be designed. Temperature changes during switching must be distinguished from a true change in directionality.
QUESTIONS THAT MATTER
Can it use the spacecraft’s waste heat?
Possibly, if an architecture preserves thermal management while producing useful net radiative momentum. The directionality, temperature, emitting area and control power need a mission-specific calculation.
Does infrared radiation count as an exhaust?
It carries energy and momentum away, although it is not expelled material propellant. This distinction is essential when describing a propellant-free device.
FOLLOW THE EVIDENCE
Go to the original work.
These are independent publications. They are not Metric Flight results or endorsements.
Joel Siegel; Shinho Kim; Margaret Fortman; Chenghao Wan; Mikhail A. Kats; Philip W. C. Hon; Luke Sweatlock; Min Seok Jang; Victor Watson Brar · Nature Communications 15, 3376
Measured angular control in a narrow infrared band. No spacecraft thrust was demonstrated.