Testing High-Risk Systems in High Places
Sending a human outside of a spacecraft to explore the solar system is high-risk business. Designing a new spacesuit, which is essentially a personalized spacecraft for extravehicular activities (EVAs), or spacewalks, is a complex effort. So, how does one manage the risk of designing a complicated spacecraft?
One approach pursued by the NASA Johnson Space Center Exploration EVA team is to identify the high-risk subsystems, build them in advance of the entire spacesuit, and test them in the microgravity environment of the International Space Station. NASA learned through experience on space station that fluid motion in microgravity behaves differently than when in Earth’s gravity. For these reasons, the Thermal Control Loop (TCL), a major subsystem of the next-generation space suit — the Exploration Extravehicular Mobility Unit, or xEMU — is being built and tested on the orbiting laboratory. The xEMU is the spacesuit being designed for use on the Moon, and the TCL, which is part of the Portable Life Support System (PLSS), circulates cooling water throughout the xEMU to keep its electronics cool and the astronaut comfortable.
SERFE Team members collaborate during telework. Pictured, from left, are Adam Korona, David Westheimer, and Shonn
Everett. Credits: NASA
While in orbit, engineers in the Space Suit Systems Branch of the Crew and Thermal Systems Division will operate the experiment by conducting 25 simulated eight-hour spacewalks, circulating water that captures heat from the system electronics and a metabolic simulator of an astronaut. The waste heat will be rejected through the Spacesuit Water Membrane Evaporator into the station’s Vacuum Exhaust System. The plan is to conduct these simulated spacewalks over the course of a year to study the long-term performance of the system, which will mirror the use of the suit when it is operated during the lunar missions envisioned for the Artemis program.
The development effort of SERFE is teaching the xEMU team valuable lessons about the design, manufacture, assembly, and testing of water pumps, bladders, backplates, relief valves, and many other important design and control features that comprise a reliable exploration-class spacesuit cooling system.
SERFE Project Manager Ben Greene presents
a status on SERFE to laboratory visitors. Credits: NASA
On the ground, SERFE successfully completed a three week-long series of mock spacewalks while awaiting its slated Sept. 29 launch to space station aboard Northrop Grumman’s NG-14 cargo craft.Those simulated spacewalks allowed the team to gather baseline data from the experiment so that when SERFE is operating aboard station, team members will have experience with the telemetry beamed back to Earth. The team completed preparations and verifications to prove that SERFE is safe to fly and operate in low-Earth orbit on space station.
A Cygnus space
freighter in the grips of the Canadarm2 robotic arm. This fall, SERFE will head
to space station aboard Northrop Grumman’s CRS-14 cargo craft, named the S.S. Kalpana
Chawla in honor of the first woman of Indian descent to go to space. Credits:
NASA
Once in-orbit and flight operations commence, the SERFE flight unit will be commanded from a ground test station in the xEMU PLSS development lab. A second identical ground-based SERFE unit will operate simultaneously in the lab.
It is expected that the two SERFE units will provide comparative data to determine what, if any, effect fluid flow in microgravity has on the hardware’s performance. Once the test campaign is complete, SERFE will be returned to the ground and disassembled for valuable material science and water-quality evaluations, helping to ensure that xEMU will be the best possible suit system as NASA explores the solar system.
