U.S.A. In our previous interview with Dean M. Olson, M.D., M.S., M.S., director of the Division of Aerospace Medicine at the Wright State University Boonshoft School of Medicine, we discussed the impacts of space travel on human health. Given the many known and unknown risks of such missions on the human body, some scientists have proposed creating chambers of artificial gravity. These chambers would essentially create mini-gravity environments in space crafts, simulating the forces we feel on Earth. This would indeed have great implications for astronauts, their experiences in space and the future of space travel. Below, Dr. Olson discusses the principles behind this new technology and future consequences it may have.
In order to counter health problems, there have been discussions of artificial gravity chambers in spaceships. How exactly do these work? Are they a feasible concept? Would there be any consequences to creating gravity in this environment?
Dr. Dean M. Olson: Biologic experiments have revealed that cells have the ability to sense gravity, although no one has as of yet determined the exact mechanism. Many of the physiologic changes that take place in human beings in the microgravity environment are the result of the combined individual cellular responses to microgravity. On the earth, gravity pulls us and holds us to the ground and causes forces to be imparted on our bodies. Our bodies have evolved to resist and manage those forces and to function normally in that environment. Based on our current knowledge and technology, there are only two mechanisms to impart forces on astronauts as a simulation of gravity, those being a rotational environment or a linear acceleration environment. The rotational environment would employ centripetal forces to simulate gravity. This can be accomplished by having a mechanism within the spacecraft similar to a merry-go-round, where in the astronaut positions themselves with their head toward the center of rotation and their feet toward the outer edge of the centrifuge, as if they were laying on their back on the merry-go-round. As the centrifuge spins, the centrifugal forces would cause the astronaut to move away from the center of rotation toward the outer edge. If there were a wall on the outer edge of the merry-go-round where the astronaut could place their feet, as the centrifuge spins, centripetal forces would be imparted on the astronaut and cause physiologic forces somewhat similar to standing on earth with gravity. The amount of force imparted on the astronaut would be dependent upon the diameter of the centrifuge as well as the rate of spin of the centrifuge.
Instead of having a rotational mechanism inside the spacecraft, a variation of this would be to create a spacecraft design where the entire space craft itself rotates. This is similar to what Arthur C. Clarke and Stanley Kubrick proposed in their story 2001 a space Odyssey. There are variations of this design where the spacecraft could be tethered with a long wire or solid structure to a counterbalancing weight or other portion of a ship. In this case, the spacecraft, the wire, and the counterbalancing weight all spin with the center of rotation somewhere along the length of the wire. The space capsule would be designed such that the astronauts would stand with their heads pointed towards the center of rotation.
The second method of using linear acceleration to impart forces on astronauts to simulate gravity incorporates the linear thrust of a space craft. As an example, when we are driving an automobile and we press on the accelerator, the acceleration of the vehicle causes the back of the seat to push against us. In that case the car is imparting force upon us by pushing on our backs. In a similar fashion, a spacecraft could be designed such that, while in space in transit to another planet or moon, the engines continue to provide thrust. The astronaut would be positioned in line with the thrust i.e. their feet positioned toward the engine and their head toward the direction the spacecraft is moving. In this case the spacecraft would be continually accelerating. The spacecraft would then be imparting a force on the astronaut similar to the car imparting force on the driver.
We currently do not know how much gravity is needed to counteract the negative effects of microgravity. For instance: would artificial gravity need to be constant; what amount of gravity will be enough (1 g, 1/2g, 1/3g) and for how long each day; would a combination of traditional countermeasures and artificial gravity be adequate? Researchers are doing their best to look into these questions.
Both of these concepts have significant complications both in their engineering design, their physiologic effects, and their economic cost and subsequently neither provides an easy solution. Although these concepts are expensive, the question must be answered, “Is it harder to design and engineer a human being and their physiology or a spacecraft and its dynamic function?” It may be that in the distant future we would see a ship with one of these designs, but before that can happen, multiple parties will have to decide they are worth the investment.
Dean M. Olson, M.D., M.S., M.S., is the director of the Aerospace Medicine Residency Program and an assistant professor of community health in the Division of Aerospace Medicine at the Wright State University Boonshoft School of Medicine. Wright State University’s NASA-funded program is the oldest civilian aerospace medicine training program in the United States. Dr. Olson earned a master’s degree in engineering mechanics and astronautics from the University of Wisconsin in 1993. He earned his medical degree from Medical College of Wisconsin in 2000. He completed a residency in family medicine at St. Mary’s Family Practice in Colorado in 2003. He also earned a master’s degree in aerospace medicine and completed his residency in aerospace medicine from the Wright State University Boonshoft School of Medicine in 2012. He is certified by the American Board of Preventive Medicine in aerospace medicine.