Feasibility of a Space Station with Artificial Gravity

The idea of Space Stations with artificial gravity has been one dreamed up by science fiction novelist for decades, but it has not been until the 21st century that mankind has been able to feasibly match this technology. We have successfully built a manned space station, the International Space Station (ISS), but the problem lies in the size of these stations, and the creation of artificial gravity. Numerous science fiction novels have massive space stations, such as the circular one seen in the film, "2001 A Space Odyssey", or the Battle Station in "Ender's Game". These massive space stations both are functional life support systems, but also benefit from artificial gravity. Both of these examples utilize the centripetal forces created by a rotating object to match the forces felt on earth, creating gravity. There are also many science fiction writers who imagine gravity being created by some object such as the gravity plating dreamed up in the Star Trek universe. Understanding that this is purely science fiction, and there is no current technology that creates or manipulates gravity, we have been able to match its effects through the use of centrifuges. This device is a spinning area that utilizing centripetal forces, just like the rotating of the space station in "2001 A Space Odyssey". On small scales, diamagnetism, the use of strong magnetic fields, has shown to produce similar forces comparable to Earth's gravity, but its application to humans is limited. Other ideas have been presented like mass collection, but again they are not feasible solutions to creating artificial gravity. A full scale space station, which benefits from artificial gravity, may be feasible through the rotation of the space station, but we first must overcome some major limitations. These include the human body, and its struggle with motion sickness as well as the sheer weight and cost of building, and then launching, these space stations.

"2001 A Space Odyssey" - Showing a circular spinning space station to create artifical gravity

Ender's Game and Artificial Gravity Space Stations

In the novel, "Ender's Game" by Orson Scott Card, there are multiple examples of space stations that utilize artificial gravity. A relatable example, from the book, is the Battle School compared to the ISS. This is a station orbiting Earth designed, and built, to train and evaluate children as future officers of the International Fleet, the defending and fighting force for planet Earth. This station holds hundreds of children, and instructors for years at a time with full life support systems in an artificial gravity environment. This is comparable to the ISS with the idea of an Earth orbiting station to support human life, but on a much larger scale (Card). According to NASA's website, the ISS holds an average of six people, and has only been visited by 215 individuals in its life span. That number is easily much less than the number of students at the Battle School. The most notable part of the Battle School is the changes in gravity between the main corridors, and the Battle Rooms. The Battle Room is a reduced gravity room, referenced as nullg in the book, where the students work as teams battling other students. Ender is introduced to this room early on by Colonel Graff, but it isn't until his first training session with Petra, in Salamander Squad, that he learns the reasoning behind the gravity changes. Petra explains the whole space station rotates, providing a centripetal force creating the artificial gravity. She uses the idea of a wheel hub to describe the Battle Station, where the Battle Rooms are the hub of which does not rotate. Since these rooms don't rotate they do not create the artificial gravity. Then the rest of the station rotates around these Battle Rooms. It can be deduced that the rest of the station matches Earth's gravity based on Ender's enrollment in a course for personal combat in Earth's gravity. If such as class exists on the station, the artificial gravity would have to match Earths to be an effective course. But, Card never addresses the main limitations that would affect such stations in our time. The physical limitations on the body, such as the effects associated with using centripetal forces to create artificial gravity, hinder the deployment of artificial gravity. Nor does he consider the limitations of getting a space station of that magnitude into space. Based on its size, it would require propulsion systems with capabilities far beyond our current technologies. These problems are discussed in more detail below in, "is it possible." Another example of artificial gravity discussed in the book, is enhanced gravity. This idea was first introduced by Petra in the Battle Room, but is not officially clarified until Ender gets to the asteroid Eros. When initially arriving at Eros, the ship is forced to land on a landing platform circling the asteroid. This is because the enhanced gravity was too much for the ship to overcome when it wanted to leave the asteroid. Mazer Rackham later informs Ender how humans can manipulate gravity following their reverse engineering of the technology from the buggers (Card).

Gavin Hood's film portrayal of Ender's Game - The Battle School

Is it possible?

Yes, it is possible to create a space station that can support human life with artificial gravity, but it will not be done any time in the near future. The problem with building a space station on a basic level is size and weight. According to Fulton, a partner of NASA, it costs NASA approximately $2,431 per pound, using current multinational launch vehicles, to get equipment into Low Earth Orbit (LEO), which is the orbit the ISS resides. According to NASA, the ISS alone weight 924,739 pounds costing over 2.2 billion dollars just to get it into LEO, not including the price of development and maintenance. To get a space station anywhere near the size of the Battle School into orbit, it would cost unattainable amounts of money that no nation would be able to afford, let alone would want to invest in. Then there is the problem with artificial gravity. We have long used machines that enhance gravity for applications such as fighter pilot training to simulate high G turns. These machines are known as centrifuges, but to this day there has not been a human application of one, in space, to match Earth's gravity. In 2014, NASA received a proposal for a gravitational biology lab to test the effects of artificial gravity that would be sent to the ISS. This lab was only big enough for small organisms, primarily fruit flies, and its applications for human trials are few and far between. These kind of experiments could eventually lead to centrifuges that humans could use, but there are a whole range of problems associated with that. The reason artificial gravity is sought after, according to Popular Mechanics, is due to the effects of reduced gravity on the body, mostly considering bone and muscle deterioration. This comes from the lack of the everyday stress associated with gravity, a big reason our muscles, and bone marrow are so dense. But, in a centrifuge the occupants are spun at a speed where the centripetal acceleration builds a force towards the outside of the centrifuge, essentially forcing its occupants into the walls of the device. This force simulates gravity, but due to natural inner ear function, humans become dizzy and light headed when spun at speeds required to get anywhere near Earth's gravity. This is due to blood pooling in the person's feet rather than making it to the brain. Imagine constantly suffering from motion sickness and dizziness, it's not a good environment for anyone let along in a stressful environment like space. NASA has developed a solution for this through the use of psychological training. As successful as this is, it is only good for relieving the motion sickness associated with the space station slowing falling back towards Earth. There are many NASA funded development programs for motion sickness relief, including a nasal spray. These programs are still in development, and have not yielded any successful results. On top of this it is known that the larger the centrifuge the slower it must spin, to simulate Earth's gravity, and vice versa for a small centrifuge. The problem with this is when considering a space station that matches the sizes in "Ender's Game", the engineering would be a limiting factor. From this engineering standpoint, making objects rotate is incredibly complex, especially at that scale. There are benefits of reduced gravity, such as a decreased need for complex bearings, but it is important to understand that there is still gravitational pull from nearby planets even in orbit. The ISS must boost itself throughout the year to keep itself from being pulled back into the Earth's atmosphere. Structurally it is difficult to account for the forces associated with a massive spinning object as well as the gravity from nearby planets. To overcome the drop in altitude over time, just like the ISS, the station would require the small fuel burns, which is near impossible to do while the station is rotating. Then finally, to make the station even slightly feasible, the weight would have to be significantly dropped by the development of ultra-lightweight materials. The materials engineering field has a lot of potential to be very lucrative, but there are no feasible developments in material sciences allowing for such lightweight materials needed to build a space station of the size in "Ender's Game", while being financially economical.

Creating Artificial Gravity on the ISS Using Centripetal Force

The Future

There are numerous science fiction portrayals of space stations and artificial gravity, and it is by no means impossible. The problem is the sheer size of a space station paralleling these science fiction novels such as "Ender's Game", as well as the limitations of the human body. Currently, the only future prospects of space stations are expanding the ISS. That being said it will never reach a comparable size to the Battle Station, nor will it be able to sustain anywhere near the same number of people. The materials needed, that would be light enough to allow for the launch of stations of this size, are just not currently possible. And, current materials are far too heavy when considering financial constraints. As for artificial gravity, a senior writer at space.com says, the only advances are the use of centrifuges to help combat the muscle and bone deterioration associated with reduced gravity. These would only be used periodically, and there are no plans to use them to create a sustained artificial gravity environment on a space station. There has been work with diamagnetism, to create a magnetic field strong enough to match Earth's gravity, but its application requires vast amounts of energy not possible today on a space station. Dr. Charles Vuille, Associate Professor of Physics at ERAU, discussed artificial gravity, and the possibility of creating it using mass collection, or opposing electric charge on space suits and the stations. He noted that mass collection could be applied similarly to Star Trek, with their gravity plates, but the application of these masses would only yield light variations in gravity. On top of that, it is just more weight to get into space, again hitting the financial constraint. The opposing electric charges is similar to the idea of diamagnetism, but again the power required to run such a device is not possible. On top of that, the problem arises of how to keep these charges away from sensitive electronics, another engineering nightmare.

Overall, if a nation had the ambition to build a space station resembling the size of the Battle Station, while employing artificial gravity, they could do it. It would require unheard of amounts of money to get that weight into LEO, and the artificial gravity would have to be produced by the spinning of the space station. Problems like keeping the station in orbit, with small burns, would require the station to be stationary, no longer spinning, during the burn time. The problems with motion sickness is the only weak link, which has the possibility of being solved in the coming years. For now it would have to be combated with NASA's psychological training.

References

Card, Orson Scott. Ender's Game. Tor, 1985. Print.

"Facts and Figures." International Space Station. NASA. Web. 27 Jan. 2015. <http://www.nasa.gov/mission_pages/station/main/onthestation/facts_and_figures.html#.VMhFdf54pXt>.

Feltman, Rachel. "Why Don't We Have Artificial Gravity?" Popular Mechanics. 3 Mar. 2013. Web. 27 Jan. 2015. <http://www.popularmechanics.com/science/space/rockets/why-dont-we-have-artificial-gravity-15425569>.

Figliozzi, Gianine. "Lights, Camera, Artificial Gravity! The Premiere of NASA's Fruit Fly Lab."NASA.gov. 12 Dec. 2014. Web. 27 Jan. 2015. <http://www.nasa.gov/mission_pages/station/research/news/fruit_fly_lab01/#.VMgfNf54pXs>.

Harm, Deborah. "About the Preflight Adaptation and Virtual Reality Training Laboratory."NASA.gov. Web. 28 Jan. 2015. <http://www.nasa.gov/centers/johnson/slsd/about/divisions/hacd/laboratories/pavrt_laboratory.html>.

Hsu, Jeremy. "New Artificial Gravity Tests in Space Could Help Astronauts." Space.com. 12 May 2010. Web. 27 Jan. 2015. <http://www.space.com/8384-artificial-gravity-tests-space-astronauts.html>.

"NASA Signs Agreement to Develop Nasal Spray for Motion Sickness." NASA.gov. 12 Oct. 2012. Web. 28 Jan. 2015. <http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-361_NASA_Motion_Sickness_Nasal_Spray.html>.

"Space Transportation Costs: Trends in Price Per Pound to Orbit 1990-2000." Fultron, 6 Sept. 2002. Web. 27 Jan. 2015. <http://www.futron.com/upload/wysiwyg/Resources/Whitepapers/Space_Transportation_Costs_Trends_0902.pdf>.