On Monday, the International Space Station (ISS) completed 25 years since the first module was launched into space.
The Zarya module reached low-Earth orbit in November 1998 and was joined by the Unity module less than a month later.
In a quarter century, the orbital outpost has hosted 273 people from 21 countries, with visitors working on more than 3,000 research and educational investigations.
To mark the station’s 25th birthday, here are 11 frequently asked questions about the ISS:
How big is the ISS?
NASA described it as “bigger than a six-bedroom house.” The ISS actually measures 357 feet (108 meters) from end to end, which is about the size of an American football field. It includes six bedrooms, three bathrooms, a gym and several research facilities.
How fast is the ISS traveling?
The space station travels at a speed of about 17,500 mph (28,000 kph), orbiting Earth every 90 minutes. This means that the crew aboard the station experiences 16 sunrises and sunsets every day. Some of these have been captured in amazing time-lapse.
How long do astronauts stay on the station?
Astronauts typically stay for about six months, although some come for shorter periods while others stay longer. In October 2023, Frank Rubio returned to Earth after spending 371 days in space – the longest time spent in orbit by a NASA astronaut. Their mission was originally scheduled to last six months, but a problem with their spacecraft caused it to be extended to more than a year.
What is the maximum number of people who can be on the ISS at one time?
The station usually hosts about six people, but at times has as many as 13 people aboard. This usually occurs due to crew changes so does not usually last very long.
Where can you get the best views of Earth on the ISS?
Thanks to its seven windows, the station’s cupola module offers unparalleled views of Earth. This is where astronauts often go during their vacation. Some people grab a camera and record what they see. For example, French astronaut Thomas Pesquet always carefully researches which part of the world the ISS will pass through at any given time so he can get the best shots.
Has the station ever been in any danger?
Yes. With so much space junk orbiting Earth, there is always a risk that a piece of it will hit a facility. It’s out of the way most of the way, but if a large piece of debris appears to be coming its way, ground controllers can alter the orbit of the facility to stay away from it. In 2021, astronauts were ordered to briefly shelter in their spacecraft after a cloud of debris was believed to be heading toward it. Thankfully, the ISS escaped any damage and everyone onboard was able to carry on as usual.
Can you see ISS from Earth?
Yes, and you don’t even need binoculars or a telescope to see it. You just have to know when to look up. NASA has launched an app that will make it easier to see the station as it passes overhead at an altitude of about 250 miles.
How do astronauts use the bathroom?
Astronauts always say this is the question they are asked most. As you can imagine, such work cannot be done in the normal way due to microgravity conditions. To ensure mess-free trips to the bathroom, engineers have designed a special device that combines a suction tube for urine (which is filtered and recycled to drinking water) and a small container to collect solid waste. Uses space. Watch this explainer for a closer look at how the ISS toilet works.
Will the ISS remain in orbit for the next 25 years?
sadly not. Its aging design means it is becoming difficult and expensive to maintain. The current plan is to continue operating the ISS until 2030. Over the next year, NASA and its partners will carefully reduce the orbital facility to the point where most of it will burn up as it enters Earth’s atmosphere.
So, will it make for a long-term stay in space?
certainly not. NASA is already partnering with private companies to build new space stations where the ISS left off. One of those companies is SpaceX, which is working with Los Angeles-based startup Vast and could become the first to launch a new module as early as 2025. China also has taikonauts living on its own space station in low-Earth orbit, and NASA plans to build a base on the Moon for long-stay astronauts.