NASA - National Aeronautics and Space Administration

A test subject runs in a zero gravity simulator on Earth in the Exercise Countermeasures Laboratory at Glenn Research Center, Cleveland. (NASA Photo)
› View Larger Image Dryden Researcher Submits Winning Idea For Future Space Treadmills

NASA needs to improve its treadmills on Earth and in space and offered a prize to NASA researchers who could help with the technologies to make it happen.

Dryden researcher Christine Jutte answered this "NASA@Work Challenge" with a new technology, for which NASA awarded her an Innovation Award of $200. In a nutshell, Jutte proposes a new spring design that, unlike coil springs, maintains a constant force over a large deflection.

The NASA challenges are intended to find answers to research questions within NASA using a collaborative, problem solving, Web-based approach. Cash awards were offered to the researcher with the best solution for each of 20 posted challenges. The NASA@Work Challenge is one of the incentive programs developed by InnoCentive, a Waltham, Mass., company NASA has contracted to spark innovation through a series of challenges.

Gail P. Perusek of Glenn Research Center, Cleveland, is the Exercise Countermeasures project manager who issued the treadmill challenge. Perusek's project is part of NASA's International Space Station and Human Research project offices. She notified Jutte by e-mail.

Christine Jutte shows a prototype of her spring design. (Photo courtesy Christine Jutte)
› View Larger Image "Congratulations, Christine. Your contribution, 'Customized constant-force spring' stood out as an intriguing new avenue that we had not considered," Perusek wrote.

Jutte welcomed the news.

"I am excited to see that my previous research in nonlinear spring design is useful to this challenge. There are many applications out there that can be improved with non-traditional, customized springs; the fulfilling (and fun) part is discovering these applications," she said.

The new concept is a customized constant-force spring design and was judged the best idea for meeting the challenge of minimizing force fluctuations over a person's maximum gait displacement of 18 inches, while also minimizing mass, volume and power requirements. It replaces gravity so that someone exercising in a simulated zero gravity environment on Earth, such as on a horizontal suspension treadmill, or someone who is exercising without gravity in space would still feel the effects of gravity with every footstep taken on the treadmill.

To achieve the goal, Jutte suggested simulating gravity with the constant-force springs she developed. The springs, which look like flattened wires, would work by pushing the person toward the treadmill to feel the effects of gravity during exercise. The springs could be designed for each individual user to accommodate different sizes and weights and also so that it can simulate both gravity conditions on Earth as well as lunar gravity, which is one-sixth that of Earth.

Astronaut Edward Lu, Expedition 7 NASA ISS science officer and flight engineer, exercises on the station’s Treadmill Vibration Isolation System. (NASA Photo)
› View Larger Image Though some additional engineering could improve the function of the constant-force spring for use in space or zero gravity treadmills, a prototype for proof of concept showed the merit of Jutte's ideas. Coincidently, Jutte's doctoral thesis was on non-linear springs, including constant-force springs, and how to create them. It was on her work at the University of Michigan, where she also earned a mechanical engineering master's degree in the same area, that she based the foundation for her NASA challenge work.

Jutte said she was delighted when her doctoral work culminated in a computer program that created nontraditional spring designs from specifications provided by the user and algorithms to scale the springs for different applications.

Applications for the constant-force spring, or nonlinear springs in general, could go far beyond space treadmills to more terrestrial uses such as improving artificial implants and prosthetics since many biological materials have a nonlinear stiffness, she said. The springs might also help reduce injuries by making heavier objects feel almost weightless while a person performs a task. In that case, the springs are used to counterbalance the heavier object.  When using the same concept in machines, smaller motors can replace larger ones, potentially leading to energy savings.

Regardless of how it will be used, Jutte's constant-force spring was judged to be a new approach that merits further investigation.

Jay Levine
X-Press Editor