Potential Dangers from Space Junk

 Perhaps you have heard that tens of thousands of objects orbit Earth. That includes all the many satellites that monitor our weather, help us study Earth’s resources, make communication possible, and allow countries to spy on each other. Much of what’s up there is space junk: spent upper rocket stages, dead satellites, and debris from collisions. NASA tracks more than 45,000 objects larger than four inches. More satellites and collision debris are added to that total every year.

Every object in Earth orbit will eventually fall back down. On average, a satellite or a piece of one falls out of orbit once a week. Most of the stuff will simply disintegrate due to friction with our atmosphere. But some will survive to reach the lower levels of our atmosphere or even to strike the ground. Larger and denser objects often survive atmospheric passage. And these pose the greatest danger. Not only are people on the ground at potential risk, so are airplanes.

Satellite rentery into Earth's atmosphere. Credit NASA/ESA/Bill Moede and Jesse Carpenter

One research paper estimated that by 2030, any given commercial airline flight will have a 1 in 1000 chance of being hit by a returning piece of space debris. At any given time, there are 12,000 to 14,000 commercial planes in the air. Collisions between airplanes and space junk seem almost inevitable.

The odds are even worse in areas of high airplane traffic. Ewan Wright and a group of researchers at the University of British Columbia in Vancouver, Canada, studied the possibility of such collision events. He stated, “There is a 26 percent chance of an uncontrolled space debris reentry in busy airspaces such as the Northeastern United States or Northern Europe each year.” The chances that the bit of space debris falling in high air traffic areas will actually hit a plane are quite small. But, as we launch more and more satellites each year, that risk will increase.

No one is suggesting that we should halt all satellite launches, but many researchers are urging that we start evaluating ways to mitigate the risks. "Aircraft can be affected by smaller pieces of debris. For example, airplanes flying through the ash of a volcano are risky because of the small particles," European Space Agency space debris system engineer Benjamin Virgili Bastida said. "Kind of a similar thing could happen with re-entering debris." Bastida and several colleagues published a paper in the Journal of Space Safety Engineering. The paper outlines the possible need to close airspace if there is a high potential of falling space debris.

None of the experts is suggesting that you stop taking airline flights. But they strongly express the need to study the problem and determine the best strategies for mitigating the dangers of returning space debris.

 

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. After it is published there, I post that same column to my blog page.

This is reprinted with permission from the Oklahoman and www.Oklahoman.com.

Living in Space Is Tough on Your Body

     Living in space, even just visiting for a few weeks or months, is tough. The environment out there can be deadly. Radiation will kill you slowly, and the lack of oxygen will kill you quickly. But those conditions can be mitigated. We build radiation protection into our spacecraft, and we carry oxygen, food, and water to keep us alive. But one dangerous aspect of space can’t be controlled: the lack of gravity. We currently have no effective artificial gravity.

You might have seen videos of astronauts floating and spinning in their spacecraft or sucking up blobs of water from mid-air. It may look like fun, but there are long-term consequences of living for extended periods with no gravity. 

Lack of gravity causes unexpected and sometimes bizarre changes in the human body. Astronauts who stay in space for too long develop puffy heads and bird-like, thin legs. On Earth, gravity pulls your bodily fluids down to your legs, but in space, that doesn’t occur. Your heart, for example, can more easily pump blood up to your head and away from your legs. As much as a gallon and a half more of various fluids can collect in and near an astronaut's head. Although that problem disappears rather quickly after returning to Earth’s gravity, NASA is working on ways to alleviate brain and eye strain during the time spent in space.

As their bodily fluids move toward the head of an astronaut, they can develop neuro-ocular syndrome. The optic nerve swells due to greater fluid pressure, causing the back of the eye to flatten. According to NASA, 70% of astronauts on the ISS experience some amount of swelling in the back of their eyes. This may cause blurry vision and the occasional headache. While glasses can help alleviate this, researchers are concerned about how this might affect astronauts on long-duration flights, such as a 1000-day trip to Mars.

An astronaut onboard teh ISS her eyes. Credit NASA

On Earth, your bones and muscles must constantly work to keep you upright against the pull of gravity. With a lack of gravity, that’s no longer necessary, and astronauts lose bone and muscle mass. NASA has developed exercises for astronauts to do while in space, and although the effect reverses itself once they return to Earth, doctors are again concerned about long flights to Mars.

In space, your heart doesn’t need to work so hard pumping blood “uphill” to your brain. As a result, the hearts of astronauts shrink a bit and become more spherical. Upon returning to Earth’s gravity, they can have difficulty maintaining normal blood pressure when standing. Again, this effect is reversed on Earth, but long flights to Mars may be quite problematic for returning astronauts.

As the head swells and more fluids enter the astronaut’s brain, it can shift a bit in their skull. This can lead to disorientation and issues with balance and coordination. That effect fades with time in a weightless environment.

I, for one, would be willing to deal with those issues for a chance to explore Mars, but NASA must consider the health and safety of its astronauts and is still seeking solutions to these problems.

 

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. After it is published there, I post that same column to my blog page.