By Dr. Gary L. Deel, Ph.D., J.D.
Faculty Director, School of Business, American Military University
This is the fourth article in a five-part series on the dynamics of human spaceflight systems for interplanetary and deep space missions.
In the last part, we discussed different kinds of propulsion systems that might be used to cross vast distances in space at reasonable periods of time. Now, we’ll look at the need to protect spacecraft from the harsh outer space environment and maintain temperatures that are comfortable for human crews.
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Many people think that space is empty. Actually space is teeming with lethal threats to life.
Radiation emitted by the Sun is a major concern. If astronauts are not adequately protected, radiation can cause significant adverse health effects, including mutations, tumors, and cancer. Earth‘s atmosphere shields us from most radiation, but even with this thick shield, we still need to be careful. We know the Sun’s rays can cause health problems. That is why we wear sunscreen when we’re outside. The same threat, however, is much more severe in space due to the lack of any protective atmospheric barrier. So protections need to be built into the hulls of a space station with layers that block and reflect or refract radiation.
Cosmic Rays Flying through Space at Tremendous Velocities Pose a Threat to Spacecraft
Cosmic rays are another significant consideration. They are atomic or subatomic particles that fly through space at tremendous velocities, most often propelled by cosmic events such as solar flares. While these rays are a threat only if their trajectories take them on a collision course with a spacecraft, some of these particles have as much kinetic energy as bullets fired from a high-powered rifle. So, although the actual risk of a collision may be low, the potential consequences of a collision could be disastrous.
This is why space stations need to be built with robust hull integrities and thick insulation to prevent a rupture caused by such a collision. A hole punched clean through a spacecraft would spell almost certain doom for any crew aboard.
Incidentally, cosmic rays are also one of the biggest challenges to the feasibility of inflatable space habitats discussed in part I of this series. Most materials that are thin and pliable enough to be folded up for launch and inflated in orbit are also far too flimsy to withstand the impact of cosmic rays. Research and development experts are currently exploring the use of new-age materials like Kevlar meshes to help with this problem, but they are far from solving the problem.
The Biggest Challenge of Temperature Control Is Not Keeping a Space Station Warm
Lastly, temperature control is an important consideration in space station design. Because space is so cold — many hundreds of degrees below zero — most laypeople assume that the biggest challenge of temperature control would be keeping a space station and its inhabitants warm. However, aerospace engineers know that the real problem is actually the opposite.
Most of the contents inside a typical spacecraft generate heat. This includes electrical components like motors, generators, and switches and, of course, humans. Additionally, unless the spacecraft is in the shade of a celestial body, it will be exposed to the uninhibited heat from the Sun. Our atmosphere insulates us from the Sun’s intense heat, but without an atmosphere the Sun is much hotter in space than on Earth.
When the U.S. space station Skylab was launched in the 1970s, a malfunction resulted in a loss of some heat shielding on the outside hull. Although engineers were able to act quickly and fix it, the Sun’s rays nearly fried the space station to the point where its electronics systems would have been damaged beyond repair, and any astronauts inside would have been cooked alive.
Unfortunately, evaporating heat on a spacecraft is also far more difficult than on Earth. Here, if it is too hot we can simply open a window and allow some ventilation by way of a breeze or fan to carry the hot air out and let the cooler air in; this is called heat transfer by convection. But space, while cold, is devoid of air, so convection is not an option. The only way for heat to evaporate in space is through radiation, which is a far less efficient means of heat transfer.
Thus, engineers need to carefully design heat evacuation systems for interplanetary space stations so that they can adequately evacuate excess heat and keep their equipment and occupants comfortable.
In the fifth and final part, we’ll explore the challenges of keeping spaceflight crews fed and hydrated during their missions.
About the Author
Dr. Gary Deel is a Faculty Director with the School of Business at American Military University. He holds a J.D. in Law and a Ph.D. in Hospitality/Business Management. Gary teaches human resources and employment law classes for American Military University, the University of Central Florida, Colorado State University and others.