Researchers report that, in a parabolic-flight microgravity test, a laser was able to accelerate ultralight graphene aerogels to speeds and distances that exceeded what the same setup achieved under Earth’s gravity. The experiment took place during the European Space Agency’s 86th parabolic flight campaign in May 2025, and the results, now published in a peer-reviewed study, provide a controlled comparison of laser-driven aerogel motion in reduced gravity versus standard conditions. If the effect scales, it could open a path toward fuel-free propulsion for small spacecraft, though significant questions about the driving mechanism and long-duration performance remain unanswered.
What the parabolic flight proved
The central finding is straightforward but striking: graphene aerogels traveled roughly 50 mm in about 0.05 seconds and hit a peak velocity of approximately 1.7 m/s when illuminated by a laser during microgravity phases of the flight, according to the Advanced Science study. Those numbers represent a sharp jump over ground-based benchmarks, where the same materials move far less under identical laser power because gravity pins them down. The study reports quantified performance comparisons between microgravity and 1 g conditions, providing a benchmark dataset for this class of laser-driven aerogel motion.
During the campaign, the team mounted centimeter-scale aerogel samples in a vacuum chamber aboard the aircraft and fired a continuous-wave laser across their surface while high-speed cameras tracked the motion frame by frame. As detailed in a Phys.org report, the researchers synchronized laser operation with the microgravity windows to capture how the aerogels responded when the pull of gravity was briefly minimized. The resulting trajectories showed repeatable accelerations along the laser axis; the authors report they controlled for aircraft vibration and other disturbances in their analysis.
The aerogels themselves were fabricated using directional freezing techniques that create aligned internal microstructures, a design choice intended to maximize the interaction between laser light and the material’s surface. Separate ground-based testing reported thrust values of roughly 36 micronewtons under specific conditions using laser power up to approximately 3.5 W, according to a Materials & Design paper that documented the fabrication and vacuum-chamber performance of these aerogels. That thrust is tiny by conventional rocket standards, but for an object weighing fractions of a gram, it translates into meaningful acceleration.
The parabolic flight campaign itself involved an aircraft flying repeated arcs that produce roughly 20 to 22 seconds of reduced gravity per parabola. ESA’s parabolic flight program describes g-level fluctuations on the order of plus or minus 0.05 g at around 1 Hz during these low-gravity windows, which means the test environment is not perfectly weightless. That residual jitter is small enough to demonstrate the basic effect but large enough to complicate precise force measurements, a limitation the paper discusses when interpreting the parabolic-flight results against 1 g control measurements.
Years of groundwork before the flight
The May 2025 experiment did not appear out of nowhere. It built on at least five years of incremental lab and drop-tower work aimed at understanding how thin graphene structures respond to light. According to ESA, earlier tests dropped a roughly 3 mm graphene sail inside a 100 m tower in Bremen under vacuum and microgravity conditions. ESA reported that a 1 W laser produced accelerations up to approximately 1 m/s² in those trials, suggesting that even modest optical power could impart measurable thrust to ultralight carbon membranes.
Separately, microgravity and vacuum tests at the ZARM drop tower used roughly 3 mm graphene micromembrane sails supported by grids, with blue and red lasers at powers around 0.1 W. The discrepancy between the 0.1 W figure cited in that Acta Astronautica study and the 1 W figure cited by ESA for the Bremen tests has not been fully reconciled in public documentation, and readers should treat the two as describing different experimental setups rather than directly comparable measurements. Both, however, point to a consistent trend: the lighter and more thermally responsive the graphene structure, the more dramatically it reacts to even low-power illumination.
Pre-flight development also included synthesis of graphene inks and aerogels, characterization through SEM and Raman spectroscopy, and multiple lab propulsion measurement configurations including quartz tube setups, pendulum rigs, and thermal vacuum chambers, as documented in a Khalifa University thesis. That body of preparatory work helped the team refine aerogel density, porosity, and thickness in ways that balanced mechanical robustness with extreme lightness, giving them confidence that the samples would survive handling and launch while still responding strongly to laser input.
By the time the 86th campaign began, the researchers had already completed extensive bench testing to calibrate their cameras, align the laser optics, and verify that any observed motion was not an artifact of thermal convection or stray air currents. The parabolic flight, in that sense, served less as an exploratory shot in the dark and more as a carefully staged validation of hypotheses formed on the ground.
What remains uncertain
The biggest open question is what exactly pushes the aerogel. Simple radiation pressure, the momentum carried by photons bouncing off a surface, accounts for only a fraction of the observed thrust. A frequently cited preprint on graphene propulsion argues the mechanism goes beyond radiation pressure and involves light-to-heat-to-gas interaction effects, where the laser heats the material and causes outgassing or thermal interactions with residual gas molecules. That explanation aligns with the concept of photophoretic force, in which a heated solid interacts with ambient gas to generate thrust by creating temperature gradients around its surface.
The distinction matters enormously for space applications. If the thrust depends primarily on residual gas, it would weaken or vanish in the hard vacuum of deep space. If some portion is purely photonic or driven by material outgassing from the aerogel itself, the effect could persist in orbit, at least until the volatile content is exhausted. The parabolic flight data alone cannot settle this question because the aircraft cabin, even when evacuated around the sample, does not replicate the pressure environment of low Earth orbit. No orbital or International Space Station tests of graphene aerogel propulsion are described in the literature cited by the team or in the sources referenced here.
There is also no publicly available raw sensor data or unprocessed video from the ESA 86th campaign beyond what appears in the Advanced Science paper and accompanying summaries. Independent verification would require access to flight logs, detailed environmental readings, or replication aboard a different platform such as a sounding rocket or cubesat. The short duration of each microgravity window, roughly 20 seconds per parabola, further limits the ability to probe long-term stability, cumulative heating, or potential degradation of the aerogel structure under sustained illumination.
Another unresolved issue is scalability. The experiments so far involve millimeter- to centimeter-scale samples with masses in the milligram range. Extrapolating from those results to meter-scale sails or gram-scale spacecraft is nontrivial. Larger structures may not heat uniformly, could buckle under small perturbations, and might interact differently with surrounding gas or plasma. The directional freezing technique that works well for small aerogels may also prove challenging to apply consistently over much larger areas without introducing defects that change the propulsion behavior.
Where the research could lead
Despite the uncertainties, the parabolic flight results underscore why graphene aerogels remain attractive for futuristic propulsion concepts. Their combination of extreme lightness, high thermal conductivity, and tunable porosity allows engineers to tailor how they absorb and reradiate energy. In principle, a swarm of tiny spacecraft equipped with such aerogels could surf beams from ground-based or orbital lasers, maneuvering without onboard propellant. Even if the dominant mechanism turns out to be photophoretic and therefore limited to regions with some ambient gas, applications could still emerge for very high-altitude Earth missions, complementing efforts such as NASA’s work on photophoretic concepts for the mesosphere.
For now, the field sits at an exploratory stage where each new experiment clarifies one piece of the puzzle while raising fresh questions. The 86th parabolic flight campaign has shown that laser-driven graphene aerogels behave more dramatically in microgravity than under 1 g, and it has provided a quantitative benchmark for future studies. Turning that benchmark into a practical propulsion system will require deeper understanding of the underlying physics, more realistic vacuum testing, and eventually, trials in orbit where the interplay between light, material, and near-perfect vacuum can be observed over much longer timescales.
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*This article was researched with the help of AI, with human editors creating the final content.
