A nitrogen cold jet thruster system called SAFER (Simplified Aid For EVA Rescue) is part of the US EVA suit ensemble. If a crewperson gets loose they can fly back using SAFER.
SAFER is not used in the normal course of an EVA. There is no other propulsive system on a US EVA suit.
SAFER was deemed necessary for the ISS era because either the Shuttle would not be present at the ISS during the EVA, or even if present, would take considerable time to undock and prepare to chase down the free-floating crewperson.
This photograph shows SAFER being tested for the first time on shuttle mission STS-64.
The system is flown by the use of a single hand controller instead of the usual one translational / one rotational hand controller scheme. The user selects between rotational and translational modes via a switch on the hand controller module. However, the controller has four degrees of freedom in either mode, with pitch commands being available in translational mode, and X translation being available in rotational mode. An attitude hold mode is available to automatically stop undesired rotations.
Procedures for the use of SAFER are found in the ISS EVA Checklist.
- EV ExtraVehicular
- GCA Ground Controlled Approach
- HCM Hand Controller Module
- IV IntraVehicular
- WVS Wireless Vision System
Additional detailed information about the SAFER system is available here.