Since the launch of the first artificial Earth satellite, Sputnik 1, on October 4, 1957, we launched thousands of spacecraft into Earth orbit and beyond. A fraction of them are still functioning, but what happened to the vast majority of them? “The Curious Droid” published another informative video titled “What happens to old spacecraft?”
Some key points from the video:
The vast majority of old spacecraft are satellites
The life of an artificial satellite can range from a few days to decades. It depends on where they’re placed into the orbit and their power source. Although it is very thin, the Earth’s upper atmosphere puts some small amount of drag on any orbiting spacecraft. So, the higher the satellite’s orbit, the longer its orbital lifetime.
The oldest spacecraft still in orbit: United States’ Vanguard 1
Vanguard 1 was launched on March 17, 1958, becoming the fourth artificial Earth orbital satellite to be successfully launched (following Sputnik 1, Sputnik 2, and Explorer 1). Although communication with the satellite was lost in 1964, it is still in orbit along with its launcher and will remain so until 2198 (estimated). That means 240 years of orbital lifetime.
Vanguard 1 is the oldest human-made object still in orbit.
Most old spacecraft end up crashing back to Earth
Because of the atmospheric drag, as explained above, crashing back to Earth is the ultimate fate for almost everything orbiting our planet up to a few thousand kilometers.
During reentry, most of those old spacecraft end up burning up in the atmosphere. Still, the biggest and densest parts fall back to the Earth. To avoid them falling into the populated areas, there is a point designated as a “spacecraft cemetery” in the middle of the South Pacific Ocean, which is named “Point Nemo”. A lot of spacecraft, including the Soviet space station Mir, ended up there.
The International Space Station (ISS) will end up there too when it eventually be decommissioned.
There is a “graveyard orbit” for the higher satellites
Burning up in the Earth’s atmosphere isn’t the fate for the satellites in geosynchronous (see notes 1) and geostationary orbits. They are too far away to be affected by the atmosphere. Instead, their orbits are influenced by the gravitational pulls of the Earth, Sun, and Moon, and even by the solar winds. So, they still need some propellants to maintain their orbits.
Just before they run out of fuel, they get boosted to a higher orbit, which is called the “graveyard orbit”. It is some 300-kilometer higher than the geosynchronous orbit, which has a radius of 42,164 km (26,199 mi). Once there, they can stay out of the way of the functional satellites below.
Theoretically, they can stay there for millions of years. But, in reality, as mentioned above, their orbits are influenced by the gravitational pulls of the Earth, Sun, and Moon, and even by the solar winds. So, in the future, they well may become a problem, but not for the next thousands of years.
Some spacecraft, like Solar & Heliospheric Observatory (SOHO) are in Sun-centered orbit (heliocentric orbit). Some others ended up there accidentally, for example, the third stages of the Saturn V rockets carrying Apollo 8, 9, 10, 11, and 12 as well as the ascent stage of Apollo 10 Lunar module (it is the only once crewed spacecraft still in space).
Once in orbit around the Sun, they are like any other asteroid. They’ll stay there until they either collide with something else, or they are pulled by the gravity of a larger body or a planet.
Over the millions of years, the Solar radiation (charged particles from the Sun) will gradually break down their structure until they break up into small pieces.
Other planets and moons
The rovers and probes which landed on other planets and moons, like NASA’s recently-lost Opportunity rover or ESA’s Huygens lander which landed on Saturn’s largest moon, Titan on January 14, 2005, will stay there.
To prevent biological contamination of any of the moons of Saturn or Jupiter, some spacecraft are deliberately disposed of via a controlled fall, like NASA’s Cassini and Galileo spacecraft.
Out of the solar system
Currently, there are five spacecraft on their way out of the solar system: Pioneer 10, Pioneer 11, Voyager 1, Voyager 2, and New Horizons.
There are also some of the third stages of the launch vehicles and de-spin weights which were attached to the probes that were generally traveling in the same direction as the probes themselves.
Although they will be long dead, these five space probes could quite reasonably be expected to outlive the human race and even planet Earth itself.
- A geosynchronous orbit (sometimes abbreviated GSO) is an orbit around Earth of a satellite with an orbital period that matches Earth’s rotation on its axis, which takes one sidereal day (about 23 hours, 56 minutes, and 4 seconds). Circular Earth geosynchronous orbits have a radius of 42,164 km (26,199 mi). All Earth geosynchronous orbits, whether circular or elliptical, have the same semi-major axis.
- A geostationary equatorial orbit (GEO) is a circular geosynchronous orbit in the plane of the Earth’s equator with a radius of approximately 42,164 km (26,199 mi) (measured from the center of the Earth). A satellite in such an orbit is at an altitude of approximately 35,786 km (22,236 mi) above mean sea level. It maintains the same position relative to the Earth’s surface. If one could see a satellite in geostationary orbit, it would appear to hover at the same point in the sky – hence the name.