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article image'Take me home' unit keeps astronauts from becoming lost in space

By Karen Graham     Dec 6, 2017 in Science
Watch enough science fiction movies and there will be a scene where an astronaut gets into trouble and ends up floating away into the vast reaches of space. But astronauts today have a "life jacket" that keeps that scenario from happening.
NASA has spent over half a century making sure that no human ever floats off into space. Various thruster systems have been developed to help astronauts save themselves in the event of an emergency.
To ensure the safety of those who walk in space, known as extravehicular activities (EVAs), a device called Simplified Aid For EVA Rescue (SAFER) is used. Essentially a "life jacket" for spacewalks, SAFER is a self-contained maneuvering unit that is worn like a backpack. The system relies on small nitrogen-jet thrusters to let an astronaut move around in space.
The standard system is the Simplified Aid For EVA Rescue (SAFER) unit. This is a simple U-shaped mod...
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 SAFER system and how it works
However, because of the SAFER unit's relatively small size, resulting in a limited amount of propellant being carried, the unit can only be used for a limited time. This is why SAFER is intended primarily for emergency rescue, and not as an alternative to tools such as tethers and safety grips as a means of getting around outside a spacecraft.
The SAFER unit is controlled by the astronaut using a hand controller attached to the front of the space suit. SAFER's propulsion, which is provided by 24 fixed-position thrusters that expel nitrogen gas, was first tested in 1994 by astronaut Mark Lee outside the Space Shuttle Discovery.
But what if the astronaut is disoriented or even unconscious? This is where not-for-profit research and development organization the Charles Stark Draper Laboratory, enters the picture. Their patented "take me home" system makes sure an astronaut using a SAFER rig gets home safely.
STS-60 mission to repair the Hubble Space Telescope.
STS-60 mission to repair the Hubble Space Telescope.
The system is similar to 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. But because there is no GPS in space, a different technology is used.
In this case, the sensors on the SAFER can detect movement, acceleration or a change in position relative to a fixed location, such as a spacecraft. Activation can be achieved by either the astronaut or remotely by another crew member or mission control, so even if a spacewalker is unconscious, the unit can still be activated.
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, eliminating the need for human assistance.
NASA astronaut  Clayton C. Anderson s  SAFER backpack is clearly visible near his rear end  attached...
NASA astronaut, Clayton C. Anderson's SAFER backpack is clearly visible near his rear end, attached below/on the side of his PLSS (Primary Life Support System). This was one of his six career spacewalks.
Training for using SAFER with Virtual Reality
While astronauts emphasize the beauty of spacel, it is also unforgiving. Astronauts have to go through extensive training, not only to prepare for the weightlessness of space, but also for the drastically modified rules of physics, and to a calmness and slowness that can at times fool us into a sense of safety.
To prepare astronauts for what it feels like to do a spacewalk, including the use of a SAFER system, NASA requires everyone go through their Virtual Reality Lab at the Johnson Space Center.
According to Tech Republic, "Virtual reality has matured and developed into a mission-critical training tool. NASA has pushed a number of different technologies to their limits to pull it off, without the glare of industry expectations or the pressure of packaging it into a consumer product."
NASA s Virtual Reality Lab at Johnson Space Center.
NASA's Virtual Reality Lab at Johnson Space Center.
Put on one of the Head-Mounted Displays (HMDs) and you're floating above the truss of the ISS. The Earth spins down below, and the moon is small and barely visible over your shoulder. The lab also has gloves with sensors, and when a user puts them on, they see the hands of an astronaut.
Dave Homan, founder of the Virtual Reality Lab, started out as an engineer in the 1990s and had developed simulations and graphics to support analysis for tasks like maneuvering the space shuttle's robotic arm. Basically, through Homan's technical expertise, VR brought together simulations and graphics NASA had been working on, saving valuable time in real-life scenarios.
Astronaut Terry Virts practices his Simplified Aid for EVA Rescue (SAFER) training aboard the Intern...
Astronaut Terry Virts practices his Simplified Aid for EVA Rescue (SAFER) training aboard the International Space Station.
"They could actually go through the entire EVA scenario, and work out what they meant by 'move me up' and 'move me down' and what coordinate system they were talking about," Homan said.
By 1994, the VR Lab introduced Simplified Aid for EVA Rescue (SAFER) training. Every astronaut is equipped with a jetpack, The astronauts who flew on STS-64 on the space shuttle Discovery — a mission that included the first untethered EVA in 10 years — trained with SAFER.
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