Today, November 2, marks two decades of continuous human presence aboard the International Space Station (ISS) in low-Earth orbit. Astronaut Bill Shepherd and cosmonauts Yuri Gidzenko and Sergei Krikalev flew into space on October 31, 2000, reaching the orbiting laboratory two days later.
The last 20 years have been an incredible achievement in terms of human endeavors and scientific research. There have been 244 people from 19 different countries in the space station, several of whom have visited multiple times. So far, over 3,000 scientific investigations have been conducted on the ISS by scientists from 108 countries. At any given time, there are about 250 experiments going on.
The ISS is the collaborative endeavor of 15 countries and took 42 assembly space flights to build, 37 of which were with the now-retired Space Shuttle program. The space station's truss length measures 109 meters (357.5 feet) and its mass is 419,725 kilograms (925,335 pounds). It is located at an altitude of about 410 kilometers (254 miles) from the ground.
At that altitude, the gravitational pull of the Earth is about 90 percent of what we experience on the ground. Astronauts and cosmonauts float because they are in freefall. The ISS moves at 7.66 kilometers per second (17,100 miles per hour) around the Earth, so it is constantly falling towards our planet, but also constantly missing. This motion creates what it is known as microgravity.
The space station, while it still has much to give, is showing its age. The Russian oxygen supply system recently hit a snag, and NASA is slowly substituting all the batteries, a process that started back in January 2017.
There are also more exciting plans beyond TLC for the ISS. NASA and its Russian counterpart Roscosmos are planning more year-long flights. The last one had Scott Kelly and Mikhail Kornienko in space for 340 days, from March 2015 to March 2016. The longest after that was Christina Koch’s 328-day residency, but this was due to a last-minute extension rather than a plan.
There are also discussions to have space tourists visit the ISS, as well as a Tom Cruise movie and reality TV show contestants. There have also been conversations about leaving some of the runnings of the space station to private companies as the focus of NASA shifts towards the Moon.
Fundings for continuous human presence in space have been guaranteed for the next decade. Hopefully, when it comes to retiring the ISS, we will have the proposed station, the Lunar Gateway, around the Moon.