The Role of SAFER in EVA: Exploring Its Testing and Usage

The Simplified Aid For EVA Rescue (SAFER) backpack has played a crucial role in ensuring the safety and efficiency of Extravehicular Activities (EVAs) for astronauts. Originally developed to help rescue astronauts in the event they become untethered, SAFER has undergone extensive testing and has been utilized in several spacewalk missions.

SAFER's Purpose and Development

SAFER, a small jetpack attached to the astronaut's suit, was designed to provide a means of maneuvering and returning to the space station if an astronaut becomes untethered during a spacewalk. While the SAFER backpack has been used in a number of spacewalks, it has never been employed in a real emergency situation. Instead, its main purpose is to provide an additional layer of safety and mobility during EVAs.

Testing of SAFER

The SAFER backpack has undergone rigorous testing both in the laboratory and in space. Mark Lee, one of the astronauts who tested the SAFER, shared his insights at a post-mission press conference. He described how they conducted a series of nitrogen-jet tests to gather engineering data, perform translating and tumbling tests, and demonstrate precision maneuvering.

The Shuttle Mission Testing

During the STS-64 mission in 1994, astronauts took turns testing the rescue jetpack while floating untethered above the payload bay. The primary objective was to familiarize themselves with SAFER and to conduct a series of nitrogen-jet tests to gather critical data.

According to Lee, the initial test involved a familiarization maneuver followed by a gaseous nitrogen calibration. This step was crucial to ensure that the fuel used in space was comparable to what they had trained with on Earth. Once the calibration was successful, they continued to conduct optional maneuvers, including tumbling and stabilizing tests.

The Tethered Testing

A tethered test of SAFER was conducted in 2000 while the Shuttle was docked to the Space Station. In this test, astronauts Mark Lee and Carl Meade evaluated their ability to recover from tumbles. With astronaut Susan Helms operating the Shuttle's robotic arm, each man took turns standing in a mobile foot restraint on the end effector and tumbling their colleague. The tumbling was followed by the activation of SAFER’s automatic attitude-hold system, which stabilized the astronaut.

During one of these tests, Meade successfully stabilized Lee as he rolled at approximately two revolutions per minute, demonstrating the effectiveness of the SAFER in control and maneuvering. The astronauts also tested their ability to recharge SAFER from a gaseous nitrogen recharging unit located in the payload bay.

Additional SAFER Tests

Further tests of SAFER were conducted during the STS-92 mission. A short clip of the test can be viewed in a video starting at 13:30. These tests involved astronauts Jeff Wisoff and Mike Lopez-Alegria, who further evaluated the functionality and reliability of SAFER. These tests provided valuable data on the performance of the SAFER in various scenarios, ensuring that it met the stringent safety and operational requirements of spacewalks.

Conclusion

While the SAFER backpack has not been used in a real rescue scenario, its testing and utilization in spacewalks have been critical in enhancing the safety and efficiency of EVAs. Continued research and development of SAFER will ensure that astronauts have the tools necessary to carry out their missions with confidence and safety.