Kobrick_2005 Copyright © 2005 by Ryan L. Kobrick. Published by The Mars Society with permission
THE HUMAN SPACEFLIGHT TRAINING RECOMMENDATIONS AGAINST WEIGHTLESSNESS PROJECT (H-STRAW PROJECT) EXECUTIVE SUMMARY
Ryan L. Kobrick*, Dr. Sarita Dara, John Burley, and Stuart Gill *University of Colorado at Boulder, [email protected]
ABSTRACT
In any exploratory human space mission, the human element is the key design driver and therefore plays a pivotal role in the overall mission success. For the next generation of exploratory missions to the Moon, Mars, and beyond, one of the critical issues for mission success lies in overcoming the physiological limitations of prolonged exposure to microgravity. The aim of this project was to take a holistic approach to counter the key physiological problems and thereby combine “humans” and “technology” in order to push new frontiers. A training scheme was developed along with a novel conceptual training device called ViGAR (Virtual Gravity Artificial Reality), a pedal-powered audio-visual environment to provide sensory information that matches the effects of the pedal input while being subjected to artificial gravity created by the ViGAR’s centripetal motion. ViGAR could have multiple benefits including: cardiovascular and muscular conditioning; reduction of bone loss; sustained low artificial gravity conditions; and psychological benefits of re-coupling vestibular and visual information. The synergistic benefit of this technology will exceed the effects of addressing these problems separately and will provide the crew with and invaluable entertainment source and the possibility of a ‘virtual escape’ from the confinement of the spacecraft. Along with the conceptual design of ViGAR, a training scheme was outlined that simultaneously addressed the physiological and psychological problems associated with long duration spaceflight. This scheme used along with ViGAR could prove to be a design guide for future space missions beyond low Earth orbit and on to Mars.
The H-STRAW Project was a submission in the Human Missions Category for the European Space Agency’s 1st Aurora Student Design Contest in 2003 and was awarded a special jury prize at the final presentation round in Barcelona, Spain.
Keywords: Microgravity; Countermeasure; Artificial Gravity; Virtual Reality; Exercise
INTRODUCTION
For a crew to arrive at a destination such as Mars in a viable condition, they will have to counter effects of bone loss, muscle weakness, vestibular readjustment, cardiovascular deconditioning, profound metabolic and endocrine alterations, and altered sensory motor performance. They will also have to overcome the psychological stresses of sensory deprivation and monotonous lifestyles. These health risks increase with exposure time to the space environment and therefore pose great concern for long duration space flight within low Earth orbit as well as interplanetary missions. Moreover, the crew may have to be in a viable condition to live and work in, for example, the Martian gravity environment (0.38g) immediately after their arrival at their destination. For the next generation of human exploratory missions, the key to mission success lies in overcoming the physiological limitations of prolonged exposure to microgravity by means of effective countermeasures to ensure the long-term health maintenance of the astronauts.
Current evidence suggests that several countermeasures should be used simultaneously in order to maintain optimal functioning of the human body and limit adverse physiological change. The crew needs to follow a rigorous time-consuming countermeasures schedule while in orbit on a day-to-day basis. However, despite the use of existing countermeasures, there is evidence of continued muscle and bone deconditioning and post-flight problems such as orthostatic intolerance and decreased exercise capacity, indicating a need for crew rehabilitation upon return to Earth. The ISS crew spends up to 3 hours per day doing exercises and their post flight rehabilitation time is approximately equal to the time spent in space.
One of the systems most affected by microgravity is the musculoskeletal. Due to the sudden absence of mechanical load on the body, there appears to be a disuse osteoporosis of the bones and disuse atrophy of the muscles. Bone mineral density appears to decrease at an average rate of about 1% per month and begins within the first few days in space. Current flight studies indicate that the bone loss in weight-bearing bones is proportional to the length of flight and that bone loss occurs despite available countermeasures. The most severe losses occur between the second and fifth months in space. Recovery of bone mass upon return to earth may take up to two years. Likewise, the muscles begin to atrophy and become smaller and weaker. Calcium and phosphorous metabolism, which is closely linked to the musculoskeletal system, is also affected. Aerobic and to some degree resistive exercises have been the primary countermeasures against bone loss and muscle loss throughout the history of space flight, but have been only partially effective. All this has cast doubt on the effectiveness of exercise programs for musculoskeletal reconditioning. However, this has also revived the interest in artificial gravity.
The basic premise about artificial gravity is to replace a “zero-gravity environment” with a “gravity environment” and therefore minimize the microgravity induced physiological changes. There are ground-based studies, which support the benefits of centrifugation in both experimental animal models and humans. However most studies give a qualitative assessment. The benefits of artificial gravity are yet to be quantified by both ground based studies and space based research. Currently, in scientific literature, the focus is on an integrated approach, using both artificial gravity and exercise to combat microgravity-induced changes.
“Artificial Gravity is probably the best means to keep all the body’s systems functioning normally.” ~ Reinhold Ewald, ESA Cosmonaut, From Interview, July 11, 2003
THE H-STRAW PROJECT
The objective of the Human Spaceflight Training Recommendations Against Weightlessness Project (H-STRAW Project) is to take a holistic approach to counter the key physiological problems and thereby enable the “human” with “technology” so that they can together push the frontiers. In this proposal – two important aspects will be addressed: • Technical design of a new countermeasure device Virtual Gravity Artificial Reality (ViGAR) shall be described. • Ground based research proposal to determine the countermeasures training schedule with ViGAR will be outlined.
ViGAR is designed to provide an integrated countermeasure for the space crew. It would provide periodic gravity environment as well as exercise, by means of a short arm centrifuge coupled with a variable load bicycle. ViGAR will be a test bed for variable gravity research for a variety of configurations and a complete configuration for a TransHab-like module (short for Transit Habitat) has been investigated. It will also be a tool to make the quantitative assessment about the “Gravity Dose” requirements in terms of the amount of gravitational load and the frequency of such an exposure, that is required to maintain physiological conditioning in space.
Before recommending the training schedule on ViGAR for use by the space crew, it is important to validate the training schedule by ground based research. It is for this reason the ground research proposal has been developed.
The H-STRAW project first outlines the documented physiological responses of the human body to microgravity exposure. The key elements are considered to be: • Bone changes • Reduction of muscle mass • Neurosensory changes • Cardiovascular changes • Fluid and electrolyte loss and hormonal changes • Hematology (red blood cell) changes
Their interrelationship is shown graphically in Figure 1 and the existing countermeasures and techniques are tabulated for comparison. From this information, it is clear that there is a strong need for a more effective strategy of countermeasures for long duration spaceflight, especially if the crew will be required to function in a gravity environment immediately after exposure to microgravity.
The technical design of the ViGAR device follows, outlining the physical principles of centrifugation and artificial gravity. Anthropometric data is used to arrive at dimensions for the ergonomics and a centrifuge design is proposed for an inflatable habitat module based on TransHab. For the configuration suggested, a rotational rate of 10rpm would provide the user with an artificial gravity level of between 0.2g and 0.5g (where Earth gravity is defined to be 1g and Martian gravity is 0.38g). The virtual reality (VR) element of the proposal is also explained, along with some details of intended usage, hardware and the psychological benefits desired. Some additional information about possible ViGAR extras and assembly strategies is provided in brief.
Given the current dearth of knowledge regarding the effects of human centrifugation, especially as a countermeasure to microgravity, a proposal is outlined for a ground-based training development program. Bed-rest with a head-down tilt is suggested, being the standard groundbased analog for microgravity. The study is designed to reveal the necessary duration and frequency of centrifugation using ViGAR in order that crew health can be effectively maintained. Figures 2 shows a CAD view of the motor and gear assembly of ViGAR and Figure 3 showns a CAD view of ViGAR in the TransHab-like module.
“Including VR in an exercise device would be a great encouragement for using it.” ~ Robert Thirsk, CSA Astronaut, From Interview, July 11, 2003
CONCLUSION
The technical design proposal was developed taking into consideration both the human requirements as well as those for integrating ViGAR into a TransHab-like module. Figure 4 shows the main ring with two armatures, and Figure 5 shows the armature on the central rotating point. Many possible developments are considered, as well as some of the potential hurdles and difficulties. The simultaneous ground-based research will define the training schedules for the astronauts on this device. Once operational, ViGAR will be an ideal test bed for variable gravity research and may eventually prove to be a novel combined countermeasures device that could help in countering the physiological and psychological effects of long duration space flight. Figure 6 shows a full view of the modified TransHab with ViGAR in the upper floor.
The ground research proposal was developed in close conjunction with the technical design of ViGAR. The results of this study will tell us whether or nor artificial gravity is useful for reversing the changes of microgravity induced deconditioning. And also help us identify the best combination of exercise (aerobic, anaerobic or mixed) and artificial gravity. The results of this study will be broad in scope and would be useful for defining other countermeasure schedule for future space travelers. It would also be useful for earth based clinical applications for the treatment of bed-ridden patients with artificial gravity and also for osteoporosis.
The project attempts to remain within the confines of technologies that are near-term or in an early stage of development, rather than in the domain of hypothetical possibilities. All of the key elements of the space segment design and the ground-based program are within the scope of today’s capabilities. Of course, additional advancements in the fields of VR, engineering, physiology or space-medicine could be incorporated by modification or refinement of the proposal. The fundamental point is that an interdisciplinary approach to the problem of countermeasure design is one that can yield strong results. As an international student team with expertise in mechanical and aerospace engineering, physics, physiology and aerospace medicine, we hope that this will be a valuable proposal, and demonstrate our belief in interdisciplinary thinking and intercultural cooperation.
“If I could add one thing to the Space Station, it would be one very large module… because I think there would be a lot of important research that could be done that could help us get out of low earth orbit and move on to flying towards Mars… What you could do with this is build a human centrifuge… Something that would allow you, while exercising, to experience… a centripetal force to test whether or not that [activity] would help prevent bone loss or help with vestibular problems that astronauts sometimes have on re-entry… This is an important question because say you are flying to Mars and you are weightless for 7 months, … as soon as you hit the ground you need to be ready to go do something… and if you have to spend a few days readapting that may not be a very good thing.” Edward Lu, NASA Astronaut, From the International Space Station, June 24, 2003
ACKNOWLEDGEMENTS
We the authors of the H-STRAW project would like to thank the following for their advice and feedback during the design process.
Professor Nikolai Tolyarenko: International Space University Professor Hugh Hill: International Space University Robert Thirsk: CSA Astronaut Reinhold Ewald: ESA Astronaut Jaret Matthews: Fellow MSS 2003 Student (CAD drawings of ViGAR and module) Peter H. Diamandis: X PRIZE Foundation & Zero Gravity Corporation
REFERENCES
“Calories Burned During Exercise.” NutriStategy, 29 Jun. 2003
Figure 1: ViGAR configuration for a TransHab-like Module Figure 2: CAD view of Motor and gear assembly of ViGAR Figure 3: CAD view of ViGAR in TransHab-like Module Figure 4: Main ring with two armatures Figure 5: Armature on central rotation point Figure 6: Full view of modified TransHab with ViGAR in upper floor