Astronauts lose significant amounts of muscle mass during any prolonged stay in space. Despite spending 2-3 hours a day exercising in an attempt to keep the atrophy at bay, many still struggle with health problems caused by low gravity. A new paper and some further work done by Emanuele Pulvirenti of the University of Bristol’s Soft Robotics Lab and his colleagues, describe a new type of fabric-based exoskeleton that could potentially solve at least some of the musculoskeletal problems astronauts suffer from without dramatically affecting their movement.
Currently, to combat problems such as muscle, strength, and bone density loss, astronauts spend upwards of three hours a day doing exercises, including the Advanced Resistive Exercise Device (ARED), which attempt to mimic compound weightlifting, and the T2 (COLBERT) Treadmill, which has harnesses that hold the astronaut in place while running on it. Unfortunately, neither of these solutions seem to be consistently effective, with astronauts still experiencing significant strength loss even while using them.
Larger exoskeletons, on the other hand, are typically rather bulky and weigh a significant amount. That might not matter once the suit is actually on the ISS or the Moon, since the lower gravity eliminates a lot of the issues with heavy objects. But, they are also notoriously uncomfortable, making it less likely the astronauts would be able to function normally while wearing them.
ESA Astronaut Samantha Cristoforetti discusses how muslce loss affects astronauts. Credit – International Osteoporosis Foundation IOF YouTube Channel
Enter the R-HEXSuit. This is a custom designed flexible exosuit intended to be worn underneath clothing. It’s made of textiles combined with Bubble Artificial Muscles (BAMs). These pneumatic artificial muscles have plenty of advantages, including being light, inexpensive, and able to lift up to 1,000 times their weight. The suit they are integrated in is only 1.4kg, and has a unique ability to both provide assisted muscle power and resistance to force the astronauts to use force similar to how they would on Earth when doing everyday tasks.
The suit was designed (and hand sewn) by Dr. Pulvirenti, who apparently got some assistance from his grandmother with the sewing. Artificial muscles, which are composed of an outer nylon layer and an inner thermoplastic layer, can be expanded or contracted as necessary. They are sewn to other fabric components, such as a waistband and knee straps (in the resistive configuration).
To test the assistive version of the suit, the team traveled to the Exterres CRATER facility, which is the largest lunar simulation facility in the southern hemisphere. The suit itself was integrated into a spacesuit, and the researchers watched the biomechanics of test subjects moving about and carrying things on different types of lunar surfaces. The test was part of the “World’s Biggest Analog” mission where over 200 scientists ran lunar-focused missions while operating out of mission control in Austria.
User showing range of motion in the R-HEXSuit. Credit – E. Pulvirenti et al.
Prior to the research work on the assistive version, the resistive version underwent some testing at the Locomotion on Other Planets (L.O.O.P) facility at the University of Milan. There, the test subjects were harnessed to a vertical suspension system to simulate lunar gravity and provided a treadmill, so they could essentially pretend they were walking on the Moon. They found the resistive version of the suit increased the metabolic requirements of walking on the Moon to about what the requirements were for walking on the Earth. They also think that is representative of having the right kind of resistance to eliminate the detriments of the low-gravity environment, though they still need to do a longer-term follow-up story to prove that out fully.
The only downside of the exosuit seems to be its comfort, with users rating it only 3.1 out of 5 on a post-use survey. In particular they seemed unhappy with how the straps over their knees rubbed on their shins. But, according to the authors, that can be improved upon in the next round of design. Also, as of now, the resistive and assistive configurations are separate layouts, and they can’t easily be switched – but again, the authors hope to add that capability soon.
For now this R-HEXSuit is still a long way from being used in space. But its unique, lightweight, and unobtrusive design make it stand out from other potential space-based exoskeletons. If they manage to fix the comfort issues, and especially if they are able to switch from an assistive to resistive configuration, there’s a decent chance that some further evolution of this particular exosuit will see some use in space.
Learn More:
University of Bristol – Robotic exosuit trousers could boost astronauts’ movement in space missions
E. Pulvirenti et al. – A Resistive Soft Robotic Exosuit for Dynamic Body Loading in Hypogravity
UT – How Bubble Muscles Could Help Astronauts Get Their Space Legs
UT – To Help Trudge Through the Snow, the Chang’e-5 Recovery Team Wore Powered Exoskeletons