While life outside the atmosphere can be difficult, there are unique benefits to be found in the microgravity environment that exists while orbiting Earth. Too often, this environment is associated with the dangerous effects of radiation, the hazards of orbital debris and the depleting effects of microgravity on bones and muscles. And though all of these dangers are intensely real, their presence also offers insights into specific countermeasures and glimpses of entirely new kinds of science.
Conceptually, it can be difficult to imagine the experience of weightlessness. The vast majority of human experience is grounded in the limited range of bodies moving at relatively low speeds, fairly close to Earth. If we simultaneously increase our speed and altitude, we can eventually achieve a balance known as an orbit. When orbiting Earth, the International Space Station is traveling at 17,500 miles per hour, at an altitude of about 220 miles. Because everything is moving at the same speed, all in a state of free-fall around Earth, objects appear weightless. When the station and its occupants are in this state, they are described as being in a microgravity environment.
Outside of the roughest simulations, however, the state of free-fall is ever-changing. Even at orbital altitudes, there is still some small degree of drag as the station interacts with the immeasurably thin layer of atmosphere found at that height. Additionally, because www.museumofflight.org of its design, the station’s structural components are often trying to move at different speeds; parts closer to Earth want to move more quickly than those farther away. The small, steady forces acting on the station caused by the differences in force are equal to about one-millionth of the gravity that we feel on Earth. The prefix ‘micro’ means onemillionth, thus the term “microgravity.”
Beyond the obvious engineering challenges, microgravity provides a unique experimental environment that allows for the exploration of processes that are difficult, if not impossible, to recreate on Earth. Some solutions to this problem include drop towers, aircraft flown in parabolic arcs, and sounding rockets. Unfortunately, these methods only provide a microgravity environment for a short period of time not ideal for most experiments. Typically, there are five research areas that benefit from this apparent reduction of gravity: biotechnology, combustion science, fluid physics, fundamental physics and materials science.
Biotechnology is the study of life sciences with the additional benefits of engineering and technology-based ideas and principles. In general, the term refers to the structures, tools and experiments that allow orbiting scientists to manufacture, manipulate and examine biological samples such as tissue cultures and cell growth experiments. It has been shown, for example, that protein crystals grown in space are not only larger and more three-dimensional, but are also more uniformly shaped, allowing for more efficient ordering. This means that for a protein-based medicine, the crystals would be more likely to match a chemical receptor, making the medicine more effective.
Concerned with all aspects of burning materials, combustion science covers a surprising range of topics. Combustion is usually a rapid, complex chemical reaction that releases energy in the form of light and heat. Because combustion accounts for approximately 85 percent of the world’s energy production, a better understanding of the processes involved can provide insight into more efficient power plants and other methods for conserving energy. And, because of the intense danger of a fire on board a spacecraft, a better understanding of combustion in microgravity can help to prevent fires and to design safer space vehicles.
The study of fluid physics provides information that affects other microgravity research such as combustion and materials science. A fluid is any material that flows in response to an applied force. Both liquids and gases are fluids. In the absence of Earth’s typical gravity, fluids are freed from buoyancy-driven flow. That means that lighter, less-dense molecules are not necessarily driven to the top of the fluid, as would occur in a pot of boiling water for example, but instead can be mixed and channeled in interesting ways.
In the same way, microgravity allows for a unique approach to studying fundamental physics, the basic laws that govern the physical properties of the universe at all scales. By removing these types of experiments from the gravity of a laboratory on Earth, scientists can test the physical properties of Earth itself, and the slight differences in Earth’s gravitational field and its effect on other scientific pursuits. Material science is the study of the formation, structure and properties of materials at different scales, from the atomic to the visible. Materials processes on Earth are subject to a number of gravity-driven phenomena, such as buoyancy and sedimentation. Freed from gravity, materials can be manipulated to produce unique combinations. On Earth, gravity would pull denser portions of the material towards the bottom, creating sedimentary layers. In microgravity, where buoyancy-driven convection is greatly reduced, scientists can experiment with materials that maintain a consistent mixture throughout, allowing for the potential creation of lighter, stronger materials with fewer structural imperfections.
Although humans in space will continue to face challenges to their health, comfort and safety, the scientific pursuits that take place in microgravity will help astronauts in orbit and, over time, humans on Earth. As NASA opens equipment racks on board the ISS to private companies, this research will only accelerate, opening our eyes to the full potential of science in space.
|14. Research in Space - October 25, 2007||1.74 MB|