By Emily Groh and Nick Wallace
Physical fitness is important both in space and on Earth. Space fitness is vital because astronauts are more susceptible to health problems such as the accelerated loss of bone and muscle mass. Without gravity and the need to perform as they do on earth, muscles and bones weaken. Traditional aerobic and muscular resistance training exercises have not been effective in space.
To help develop improved exercise routines and equipment for crew members, the Human Health and Performance Program at the NASA Glenn Research Center (GRC) is constructing the Enhanced Zero Gravity Locomotion Simulator (eZLS) in association with the Cleveland Clinic Foundation (CCF). Along with the simulator, an analytical model is being developed to incorporate the physical dynamics of the eZLS, which will make it easier to study the effects of the treadmill on the human body.
So how do you simulate zero gravity here on earth? GRC engineers chose to build a truss superstructure to suspend both the simulation equipment and the astronauts. To ensure accuracy in the testing and analysis, OPTI Trilite heavy-duty 218 box truss was selected for the job. The lightweight spans, capable of loading in excess of 3,000 pounds, virtually guaranteed a zero-deflection, vibration-free platform from which to do the testing. A Finite Element Model (FEM) of the truss superstructure and custom components mounted to the structure were developed at GRC to verify that both static loading and dynamic frequency response of the system were adequate for safety and research requirements.
The entire job was designed in a highly collaborative effort involving engineers and designers at the GRC and CCF, the installing contractors and their engineers, and the Optikinetics American and British DesignLine teams. Without the use of Computer Aided Drafting (CAD) and the Internet, collaborating effectively and quickly would have been impossible just a few years ago.
The Trilite box truss design consisted of a 28-foot-long by 20-foot-wide by 20-foot-high structure and included highly customized components and mounting plates for NASA equipment. Thinking “outside the box" was the rule rather than the exception, ensuring the structure would not only fulfill the currently designed testing needs but also future testing procedures. The ability of Optikinetics to provide a full line of standard truss components and quickly fabricate custom parts for current and future add-ons are services few other manufacturers can provide.
The eZLS combines a treadmill that floats on a thin film of air and a supine suspension system that simulates a zero-gravity environment by completely offloading the weight of a human subjects head, torso, arms, and legs. The test subject is suspended horizontally so the body remains weightless, with respect to the running surface, until a controllable “gravity replacement load is applied to the body via a system of motors and cables that connect to a backpack harness worn by the test subject. The subject is suspended off the 20-foot-high freestanding Optikinetics truss superstructure.
The treadmills running surface is mounted vertically in a freestanding frame as if the subject were running against the wall. The eZLS is designed for ground-based experiments to gain insight into the forces acting on the body so that more efficient exercise prescriptions may be developed to help astronauts maintain a healthy fitness level. In addition to running and walking, the eZLS eventually will be able to simulate cycling, resistance training, and jumping exercises.
Prior to becoming a project at Glenn in February 2004, Zero Gravity Locomotion Simulators were developed at Penn State University and the CCF. Headed by world-renowned biomedical researcher Peter R. Cavanagh, Ph.D., the Center for Space Medicine was formed to combine the biomedical engineering efforts of CCF and GRC. Commenting on the significance of the eZLS, Project Lead Gail Perusek said, “This project presents a rare opportunity for GRC to work with human test subjects in a ground-based simulation. Also, this is the first National Space Biomedical Research Institute (NSBRI) research funded and conducted at GRC.
Improved exercise programs would greatly benefit astronauts who experience bone/muscle mass loss at alarming rates while in space. According to Perusek, despite 2 hours of exercise per day on the International Space Station, astronauts still lose from 1 to 1.5 percent of their bone mass per month - or 10 times the rate of loss in a postmenopausal woman. Studies published by NASA Johnson on www.nasa.gov reveal that astronauts can lose up to 20 percent muscle mass during a 5- to 11-day spaceflight. NASA researchers will continue to study both the short- and long-term effects of bone/muscle mass loss on the astronaut body once he/she returns to Earth.
Aside from space applications, experiments conducted using the eZLS may help medical researchers develop methods to help prevent osteoporosis in people living on Earth, as the mechanism of bone and muscle loss is similar. The eZLS will be used to support future missions related to the Vision for Space Exploration. Also, it may be used to help specify design requirements for the exercise equipment on the Crew Exploration Vehicle (CEV) and simulate planetary locomotion in partial gravity environments including the Moon and Mars.
Nick Wallace, CAD Designer at OPTI - The Americas, remarked, “Imagine that! I never thought that our work at Optikinetics might include biomedical applications here on earth, in space, or perhaps even on the moon! Just when you least expect it a completely unique application comes along that takes full advantage of the versatility of Optikinetics Trilite truss systems. OPTI and the space program - just imagine what could be next!
Emily Groh is part of the NASA Exploration Systems outreach group.
Nick Wallace is the Trilite CAD Designer for OPTI - The Americas.
For more information regarding NASA's Exercise Countermeasures Project, contact Gail Perusek, at [email protected].
Optikinetics Ltd. manufactures OPTI Trilite structural systems as well as OPTI Kinetics effects lighting products. For more information, contact Optikinetics at [email protected].