An unmanned Cygnus cargo ship left the International Space Station today, and then NASA set it on fire. At 4:55 pm EDT, ground control activated the Saffire-I experiment in the hold of the Orbital ATK Cygnus Pressurized Cargo Module as it drifted away from the station, triggering the largest fire ever started in space. The controlled burn inside an insulated container is part of a study to learn more about the nature of fire in zero gravity and improve spacecraft safety.

The Cygnus spacecraft, which had been docked with the station since March 26, was filled with rubbish and after separating from the ISS at 9:30 am EDT was maneuvered to a safe distance away by a robotic arm before it fired its thrusters to send it on a trajectory that will see it burn up over the South Pacific in about 8 days.

This departure would normally have been the end of the Cygnus CRS-6 mission, but NASA is taking the opportunity on this and two subsequent Cygnus flights to carry out fire safety experiments. The space agency says that with more long-duration manned flights planned for the future, fire has become a significant hazard, so more needs to be known about how things burn on a large scale in space.

 The pre-flight Saffire-I lit by green LEDs as it was during flight. (Credit: NASA)

In the Spacecraft Fire Experiment (Saffire)-I experiment, a 40 x 100 cm (16 x 39 in) length of cotton-fiberglass material blend was set alight inside of an enclosure by means of a radio signal that activated a hot wire and started a fan to blow air in from the hold. As the material strip caught and burned avionics and cameras recorded the nature and spread of the flames inside the experimental unit and transmitted the results back to Earth.

NASA says that it will continue to monitor the burning until the Cygnus burns up on about June 24.

The video below shows the Cygnus CRS-6 leaving the space station.

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