It's a nightmare scenario. An unconscious astronaut on a spacewalk gone wrong floats off into deep space with no way to get back and no way for anyone to reach them. To prevent this from happening, engineering firm Charles Draper Laboratory has patented a "take me home" automatic rescue system that allows a disabled or disoriented astronaut to return to safety at the push of a button.

Watch enough science fiction and you're bound to see it – a scene where an astronaut on a spacewalk, due to accident or carelessness, floats off into the infiniteness of space. In real life, nothing like that has happened and NASA has spent over half a century making sure it doesn't by developing various thruster systems to help astronauts save themselves in the event of an emergency.

The standard system is the Simplified Aid For EVA Rescue (SAFER) unit. This is a simple U-shaped module that bolts on to the astronaut's life support pack. The large box on the bottom contains a bottle of pressurized nitrogen and the arms hold tiny thrusters. In the event of losing a handhold on during a spacewalk while untethered, a control unit on the chest allows the astronaut to jet back to safety.

The problem with this set up is that it isn't of any use if the astronaut is unconscious, confused, ill, or blinded. To overcome this, Draper has developed a system that acts like the automatic return on some upmarket drones, where the press of a button or a low battery charge causes the drone to stop whatever it's doing and return to base.

Funded by NASA, the "take me home" system is similar, but since there's no GPS in space it can be configured to work in a few different ways. Its sensors can detect movement, acceleration or a change in position relative to a fixed location, such as a spacecraft, and once activated – either by the astronaut or remotely by another crewmember or mission control – the navigation module can use dead reckoning, beacons, vision-aided navigation or a star-tracker system to calculate how to get the crewmember home, depending on the final system design. The system also takes into account time, oxygen consumption, and safety and clearance requirements to calculate a trajectory that will return the person to safety using the SAFER unit.

According to the patent, the system could carry out the rescue by itself by taking control of the thrusters, or it may provide the astronaut with visual, auditory, and sensory cues using sensors and a helmet display. It can also be programmed to handle a number of anticipated scenarios and act accordingly.

Draper says that the "take me home" technology could also find applications on Earth, aiding first responders, fire fighters, skydivers, and scuba divers in disorienting situations.

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