This year, the International Space Station celebrated 20 years of having a continuous human presence on it.
There have been 242 individuals from 19 countries who have made trips to the station, including the latest four who launched from Cape Canaveral on Sunday: Michael Hopkins, Victor Glover, Shannon Walker and Soichi Noguchi.
But what exactly is the International Space Station and what does it do?
Here’s a guide to key questions and facts about the ISS.
What purpose does the ISS serve?
Created in 1998 when government officials from 15 nations signed an agreement for its design, development and utilization, the main purpose of the ISS is to serve as a research laboratory for microgravity and space environment.
Experiments are conducted by crew members in fields such as biology, physics, astronomy and meteorology.
How was the ISS constructed?
Over a 13-year period from 1998-2011, different modules were launched into space and attached to each other in orbit by astronauts.
The initial module, named Zarya, was constructed in Moscow and launched into orbit from Kazakhstan on Nov. 20, 1998 by a Russian proton rocket.
Zarya was a module within the rocket, and then the outer edges of the rocket were shed once in space, leaving the module floating by itself.
A couple weeks later, on Dec. 4, 1998, another module named Unity was launched from Cape Canaveral in Florida, this time carrying six astronauts tasked with connecting Unity with Zarya in orbit.
That mission was successful to create an initial base, and in subsequent years, other modules were launched into orbit and connected.
As of now, there are 16 modules that comprise the ISS.
Click or tap here to learn more about how the ISS was made.
What are some notable facts about the ISS?
- The ISS weighs almost 400 tons.
- It’s about as wide as an American football field.
- It travels at 17,500 mph and can orbit the Earth every 90 minutes.
- There have been 396 spaceflights to the ISS.
- The ISS cost $150 billion to build.
- Operations of the ISS are primarily controlled by centers in Houston and Moscow.
How many people are on board the ISS?
With the addition of Hopkins, Glover, Walker and Noguchi, there are now seven astronauts aboard the ISS. The foursome joined American Kate Rubins and Russians Sergey Ryzhikov and Sergey Kud-Sverchkov, who were launched to the ISS from Kazakhstan on Oct. 14.
To learn more about the daily routines of the astronauts on the ISS, click or tap here.
Or check out how the astronauts do basic life functions on the ISS.
What is the future of the ISS?
The ISS is currently approved to operate through at least December 2024, although there’s a good chance it will be extended until the end of 2028, according to space.com.
However, as the saying goes, nothing lasts forever.
The ISS is aging -- and if it’s not eventually destroyed or taken down by humans, space obstacles might arise, according to space.com.