International Space Station — Zarya module launched

On 20 November 1998, a Russian Proton-K rocket launched the Zarya (meaning 'dawn') Functional Cargo Block from Baikonur Cosmodrome. Zarya was the first module of the International Space Station — a 19,323-kilogram cylinder built in Russia by the Khrunichev centre, but funded entirely by the United States under a post-Cold-War cooperation agreement.

Two weeks later, Space Shuttle Endeavour launched carrying the Unity connecting node. Astronauts performed three spacewalks over five days to connect the two modules, establishing the initial seed of what would grow into the largest structure humanity has ever assembled in space.

The ISS expanded module by module over the following 13 years, ultimately comprising 16 pressurised modules with a total mass of approximately 420,000 kilograms — the volume of a six-bedroom house, built by 15 nations at a cost estimated at $150 billion. Construction required 42 Shuttle flights, 37 Soyuz flights, and more than 1,500 hours of spacewalks.

The station has been continuously inhabited since 2 November 2000, hosting more than 270 people from 21 nations through its first 25 years of crewed occupation. It completes 15.5 orbits per day at roughly 408 km altitude, travelling at 7.66 km/s.

“The International Space Station is the most complex scientific and technological endeavour ever undertaken by the human race.”
— NASA Office of Inspector General· 2018 Report on ISS

Mission Data

Zarya launch

20 Nov 1998

Module mass

19,323 kg

Continuous habitation

Since 2 Nov 2000

Total station mass

~420,000 kg

Pressurised modules

Altitude

~408 km

Key Facts

Zarya was built in Russia but paid for entirely by the United States at a cost of $190 million — a post-Cold-War cooperation milestone
The ISS spans 109 metres end-to-end — roughly the length of an American football field — making it visible to the naked eye from Earth
Construction required 42 Shuttle flights, 37 Soyuz flights, and more than 1,500 hours of spacewalks over 13 years
Over 270 people from 20 nations have lived aboard the ISS; it has been continuously inhabited since 2 November 2000
The station generates about 84 kilowatts of electricity from eight solar array wings — enough to power 40 average homes

Why It Mattered

The ISS is the most expensive and complex structure ever built by humanity — and the most durable symbol of international cooperation in history. It has served as humanity's continuous off-world home for over 25 years, advancing science in microgravity biology, physics, and medicine.