Installing SAFER on Alexander Gerst. Credits: NASA

Installing SAFER on Alexander Gerst. Credits: NASA

Alexander and Reid have donned their SAFER units that are their backup if they ever lose grip of the International Space Station. The SAFER backpack (Simplified Aid For EVA Rescue) a jetpack that expells nitrogen jets to propel the astronauts back to safety. To keep weight and size down only a small amount of nitrogent propellant is stored, so the backpack is to be used in emergencies only. During their spacewalk the astronauts will move around by hand except Alexander who will also hitch a ride on the Space Station’s robotic arm.