The latest set of space-fire experiments has blazed up aboard the private Cygnus cargo spacecraft.

Mission controllers on the ground ignited NASA's Spacecraft Fire Experiment II (Saffire-II) today (Nov. 21), shortly after the uncrewed Cygnus departed the International Space Station (ISS) following a monthlong stay.

The three-part Saffire program is investigating how fires spread in microgravity and aims to help researchers design safer spacecraft down the road. Saffire-I burned a piece of cotton-fiberglass cloth 1.3 feet wide by 3.3 feet long (0.4 by 1 meter) on June 14 aboard a different Cygnus, in what NASA officials described as the largest fire ever intentionally set in space.

Saffire-II adds to the data by igniting a variety of different materials, NASA officials said.

"The nine samples in the experiment kit include a cotton-fiberglass blend, Nomex and the same acrylic glass that is used for spacecraft windows," they wrote in a description of Saffire-II.

Saffire-II's samples are relatively small; each measures 2 inches wide by 12 inches long (5 by 30 centimeters). The final set of experiments, Saffire-III, will ignite a large-scale fire, similar to the one lit during Saffire-I, when its time comes during a future mission, NASA officials said.

All three Saffire experiments fly aboard the robotic Cygnus vehicle, which is built by Virginia-based aerospace company Orbital ATK.

An Orbital ATK Cygnus cargo ship departs the International Space Station on Nov. 21, 2016 in this video from a station camera.
An Orbital ATK Cygnus cargo ship departs the International Space Station on Nov. 21, 2016 in this video from a station camera.
Credit: NASA TV

This particular Cygnus arrived at the ISS on Oct. 23, loaded up with a variety of supplies, hardware and science gear. The spacecraft departed today and is scheduled to remain in orbit until Sunday (Nov. 27), when it will be steered toward a fiery death in Earth's atmosphere. (Unlike SpaceX's Dragon cargo capsule, Cygnus is designed to be disposable.)

The Saffire program is managed by NASA's Advanced Exploration Systems division.

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