In 2016, NASA deliberately set fire to an empty spacecraft after it left the ISS, creating the largest controlled fire experiment in space

There is an old saying that goes: don't play with fire. Well, apparently NASA responded by setting its own spacecraft on fire. In 2016, NASA ignited a fire inside the uncrewed Cygnus cargo spacecraft just after it had been undocked from the International Space Station, burning a fabric sample in what the agency called the largest fire ever intentionally set in space. The fire itself was a contained, deliberately triggered burn inside a purpose-built experiment module, a separate event from the spacecraft's eventual destruction. Cygnus was destroyed only afterward, and by a different process entirely: it burned up naturally, as planned all along, when it re-entered Earth's atmosphere at the end of its mission.

According to NASA's official statements, the experiment was done by engineers at NASA's Glenn Research Center and Orbital ATK in order to study flame propagation in microgravity, which is crucial information to keep astronauts safe when they are on long missions, including future journeys to Mars. There were no astronauts nearby. There was no need for sirens, and there was no rush to extinguish the fire. It was simply an unoccupied spacecraft that was destined to be burned in the atmosphere of the Earth.

Why torch a spacecraft in the first place


If your immediate response to this information is "hang on, but isn't fire the worst thing that can happen in space?" then you're correct. Fire has long been regarded as one of the worst dangers any spacecraft could face, because there is nowhere to run and no outside air to vent it out with. This is exactly why NASA needed hard facts rather than assumptions.

There has been no previous research on a fire of a significant size in orbit simplybecause doing so anywhere near a crew would have been far too dangerous. That's not to say fire in microgravity was a total unknown: according to NASA’s Glenn Research Center, engineers had run small-scale tests before, but the largest of them had only ever burned something about the size of an index card. That's all we knew about the behavior of fire in space after decades of space missions.

The material which was set ablaze during this experiment was a piece of cotton-fiberglass fabric approximately 0.4 by 1 meter. It was ignited using a hot wire after Cygnus drifted away from the ISS. Sensors and cameras were used to monitor the amount of oxygen, temperature, and changes in flame behavior.

The science behind the smoke

This was not some one-time gimmick but rather the start of NASA’s program called Saffire-I or the Spacecraft Fire Safety Demonstration, which ran a series of six experiments conducted over multiple Cygnus flights between 2014 and 2016. The program has since concluded: Saffire-VI, the sixth and final experiment in the series, wrapped up in January 2024 when its host Cygnus vehicle burned up during a planned reentry. Peer-reviewed articles from across the series showed that the way fire operates in zero gravity is very different from what we are familiar with in terms of forced hot-air movement upward to fuel the flame with fresh oxygen.

According to a 2019 study titled “Flame spread: Effects of microgravity and scale,” published in Combustion and Flame, by NASA scientist David L. Urban et al., this was the first instance when scientists had the chance to observe how a flame would spread within an actual space vehicle. The study compared this microgravity, forced-airflow flame spread, driven purely by the spacecraft's ventilation system, since there's no rising hot air to feed a flame without gravity, against the buoyant, gravity-driven flame spread we're used to seeing in ordinary fires on Earth. This is important information in terms of designing air ventilation systems, selecting materials for the cabin interior, and rewriting the emergency protocol for future spacecraft.

Why this matters

It would be very easy to classify this particular example as another cool experience from NASA history, skip this information, and never think about it again. However, it is important to mention that this particular experiment is a silent reminder of how sending people to Mars does not only mean developing new and powerful rockets. In fact, it means solving dozens of ordinary engineering problems, for example, what should be done in case the wire shorts in six months of space travel and no firefighting department can be called.

As mentioned by NASA itself, such experiments cannot be conducted in the presence of astronauts for obvious reasons, which is why the use of an empty cargo vessel, whose life was going to end in the atmosphere in any case, made sense as a test subject. As reported by Smithsonian Magazine, NASA experts have used mostly fire models and small space tests before this one, leaving significant gaps in understanding of the risk of fire in space.