International Space Station

The International Space Station is the most complex international scientific and engineering project in history and the largest structure humans have ever put into space. This high-flying satellite is a laboratory for new technologies and an observation platform for astronomical, geological, and environmental research. As a permanently occupied outpost in outer space, it serves as a stepping-stone for further space exploration. This includes Mars, which NASA is now stating is its goal for human space exploration.

The space station flies at an average altitude of 248 miles above Earth. It circles the globe every 90 minutes at a speed of about 17,500 mph. It takes the space station one and a half hours to fly around the planet, making 16 complete orbits a day. For those on board, the visual effect is spectacular. When they open the covers over the windows, the light can be so blinding that astronauts must reach for their sunglasses. But after 45 minutes of daylight, a dark line appears on the planet, dividing Earth into night and day. For a couple of seconds, the space station is bathed in a coppery light and then complete darkness. About 45 minutes later, and just as abruptly, the sun rises to fill the station with brilliant light again.

Five different space agencies representing 15 countries built the $100-billion International Space Station and continue to currently operate it as of 2016.

It was also planned to provide transportation, maintenance, and act as a staging base for possible future missions to the Moon, Mars and asteroids. The ISS provides a platform to conduct scientific research. Small unmanned spacecraft can provide platforms for zero gravity and exposure to space, but the space station offers a long-term environment where studies can be performed over periods that exceed the capabilities of manned spacecraft.

The ISS simplifies individual experiments by eliminating the need for separate rocket launches and research staff. The wide variety of research fields includes astrology, human research, space medicine, life science, physical science, space weather, and meteorology. Scientists on Earth have access to the crew's data and can modify experiments or launch new ones, which are benefits generally unavailable on unmanned spacecraft. Crews fly individual expeditions lasting several months, providing approximately 160-man-hours per week of labor with a crew of 6.

It takes a two-day journey dictated by speed and altitude to get to the space station. Before astronauts can get aboard the station, they first have to chase it down and pull alongside. To accomplish this, it needs 900 tons of solid rocket fuel and half a million gallons of liquid oxygen and liquid hydrogen to burn in the main engine.

The space station will be orbiting Earth for at least another five years, but probably much longer. Of the agencies that pay for it, only one agency has yet to finalize plans to keep it in orbit until 2020. Further moves are in place to keep the station flying until 2028.

For those who built the space station, and the thousands of support staff at agencies around the world, seeing its bright light shooting across the sky at night evokes feelings many others would be able to understand.