We try to avoid thinking about it, but spacecraft are machines that break down and eventually
fail.
Some can last for years, others decades, but in the end they’ll be gone forever.
Space agencies do consider how these missions will end, and put plans in place to wrap them
up when the time comes.
But sometimes they have no choice, and dead spacecraft return to Earth with no way of
controlling when and where it’s going to happen.
It’s fun to think about new projects, but not so much fun to think about how those projects
are going to end.
Space agencies do what they can to limit the impact of their dead spacecraft, but space
is a hostile and unpredictable place.
Mechanical problems, micrometeorite impacts, and software failures can cause even fully
functional spacecraft to go dark.
For the spacecraft out in deep space, it’s not that huge a problem.
One day you’re depending on it for pictures of Earth, or climate data, or a deeper view
into the Universe, and the next day that trusty spacecraft is offline, never to be heard from
again.
Time to launch a replacement.
There are amazing stories of spacecraft brought back from the brink of failure (mental note,
I should totally do an episode on that), but there are also examples of spacecraft that
just went silent.
In 2009, for example, two satellites actually smashed into each other.
The communications satellite Iridium 33 and the already deactivated Russian Cosmos-2251
just collided at a speed of 11 km/s at an altitude of 789 kilometers.
Obviously neither satellite survived, and about a quarter of the debris had burned up
in the Earth’s atmosphere by 2016.
For the vast majority of missions, operators use a graveyard orbit.
This is a region of space which is far enough away from common orbits that a spacecraft
put there isn’t likely to whack into another satellite.
Mission controllers use these orbits for geostationary satellites, for example, since the amount
of fuel required to de-orbit the spacecraft is just too large.
In general, a satellite will need about three-months of station keeping fuel to move out into this
graveyard orbit, so they make this decision when the satellite is nearly out of fuel.
Spacecraft closer to Earth are de-orbited into the atmosphere, where they mostly burn
up.
I say mostly, because larger chunks can survive going through the atmosphere and crashland
on Earth.
If the mission operator has any control over the spacecraft, they typically crash it into
a region of the Pacific Ocean known as the Spacecraft Cemetery.
Located about 3,900 kilometers southwest of New Zealand, it’s a region that’s as far
as possible from any human habitation.
Lots of room to dispose of old space stations, Progress cargo ships and other non-functional
spacecraft.
Down there, beneath 3 kilometers of water, you’ll find the remains of the Russian Mir
space station, more than 140 Russian resupply ships, European cargo ships, and more.
This will be the future home for the International Space Station.
At some point in the next couple of decades, NASA and the Russian Space Agency will finally
pull the plug on the ISS.
NASA and Russia recently announced their ongoing commitment to fund ISS until at least 2028.
Who knows how much longer they’ll keep it going.
Eventually, though, it’s headed for the Spacecraft Cemetery.
When the time comes, or if ISS ever needed to be evacuated, mission controllers will
fire the rockets on two Progress spacecraft on board, lowering its orbit into a perfect
flight path that brings it down into the South Pacific.
When it does come down, it’ll be the largest human built object ever crashed into Earth.
Chunks of it will absolutely survive the journey, so this has to be done right.
NASA’s Hubble Space Telescope is also eventually coming down.
If it doesn’t get any further boosts, it’s going to return to Earth uncontrolled some
time in the 2030s.
There are missions in the planning stages that could attach a booster rocket to the
aging telescope.
Then they have a choice.
Do they continue refurbishing it, and boost it into a higher orbit, or bring it down safely
like ISS and other satellites.
I’ll let you know when they’ve made a decision.
What about in deep space?
For the spacecraft on escape trajectories from the Solar System, there’s nothing you
can do.
Eventually the Pioneer and Voyager spacecraft are just going to run out of electricity coming
from their radioisotopic thermoelectric generators.
Controllers at NASA will shut down their instruments one by one, turning off the communication
gear.
Those spacecraft will just continue on, making their way for thousands, millions, and maybe
even billions of years.
Eventually the interstellar dust will wear them away to nothing.
Sometimes spacecraft are still sort of functional, but there’s a risk that they might contaminate
a world with their filthy Earth bacteria.
This was the case with NASA’s Galileo and Cassini spacecraft.
Galileo was launched to Jupiter in 1989, arriving at the giant planet in 1995.
Although it had problems with its main radio antenna, the mission was still successful,
observing Jupiter for longer and closer than any spacecraft we’d sent there before.
As the spacecraft started to run out of fuel, mission planners had to make a tough decision.
Should they leave it in orbit around Jupiter forever, risking the chance that it might
crash into one of its icy moons, potentially contaminating its surface with bacteria from
Earth.
Or should they crash it early, removing that future risk.
In the end, they decided to smash Galileo into Jupiter, on September 21, 2003.
As it passed into the cloud tops, atmospheric friction tore the spacecraft into fiery pieces
which rained down into the planet.
And as you probably recall, NASA made the same decision just a few months ago, when
they de-orbited the Cassini spacecraft into Saturn.
Again, NASA was concerned that Cassini might eventually crash into one of Saturn’s icy
moons, like Enceladus, infecting the world with bacteria from Earth.
On September 15, 2017, Cassini, which had served us so well, exploring the Saturnian
system, and uncovering so many mysteries about the planet’s formation, rings and moons,
was crashed into Saturn’s cloud tops.
This will be the fate for any other spacecraft sent into orbit around any of the giant planets.
So, prepare yourself emotionally for the loss of Juno, the Europa Clipper, and whatever
gets sent back to Saturn in the future.
We’ve talked about planning for the end of several missions, but sometimes missions
end in unplanned ways, and spacecraft come crashing back to Earth totally uncontrolled.
This is going to be happening shortly, and I’ll get into that, but first I’d like
to thank:
John Rowell Brett O'Malley
Jeremy Costella
And the rest of our 796 patrons for their generous support.
If you love what we’re doing and want to get in on the action, head over to patreon.com/universetoday.
It’s best to be organized, and carefully plan for the end of your mission, but sometimes
those details just get away from you.
Spacecraft return to Earth and you can’t control when and where it’s going to happen.
The Earth’s atmosphere destroys anything on an uncontrolled descent, but sometimes
larger chunks can survive re-entry and crash into the planet.
Perhaps the most famous example of this was NASA’s Skylab mission, which occurred on
July 11, 1979.
Although they couldn’t de-orbit the station, they could change its orientation to aim it
at a less populated area.
They hoped to strike the open ocean off the coast of Africa, and calculated that the chance
hitting a human was 1 in 152.
But it didn’t burn up as quickly as NASA was expecting, and smashed into Australia
about 480 km southeast of Perth.
Over the years, several spacecraft have re-entered the Earth’s atmosphere, including several
chunks from Apollo missions, Russian spacecraft, and dead satellites.
The most recent ones I can remember vividly were the Russian Fobos-Grunt mission, which
was supposed to retrieve a sample from the Martian Moon Phobos, and instead failed to
reach its transfer trajectory and was trapped in low Earth orbit.
It eventually came down in the Pacific Ocean off the coast of Chile in 2012.
And back in 2011, NASA’s Upper Atmosphere Research Satellite came down uncontrolled,
also into the Pacific Ocean.
It was pretty nerve wracking to watch the position of the satellite update as it made
its way towards my location on Vancouver Island.
Wonder what that felt like?
Sound like fun?
Good news, you’re going to experience it for yourself shortly.
That’s because the Chinese Tiangong-1 space station, which was launched in 2011 is going
to be coming back down some time in the next few months, uncontrolled.
The station was used for 6 different space missions over the next few years, but it broke
down in 2016.
And now, as the station ploughs through more and more of the Earth’s atmosphere, it’s
slowly losing altitude.
It already lost about 50 km of altitude in 2017, and now’s it’s a matter of when
and where it’s going to come back to Earth - some time in early 2018, from January to
March depending on various simulations.
According to Chinese officials, the station is expected to reenter the atmosphere somewhere
between 43-degrees north and south latitudes.
So, pretty much anywhere in the middle of the planet.
When it does come back through the atmosphere, most of it will burn up, but chunks will survive
long enough to reach the surface.
It should make a spectacular streak through the sky as it burns up.
Although the chances of a spacecraft actually crashing into a city is pretty low, it’s
a little unnerving to know it’s overhead and coming down soon.
As we get closer, and controllers can see that it’s about to come down, I’m sure
there’ll be websites that’ll let you track the position in real time.
And if any debris does actually come down in your area, contact the authorities and
stay away, there are all kinds of toxic chemicals on board that you don’t want to anywhere
near to.
As we launch more satellites and learn to live in space, we’re going to need to be
more careful about what happens with our dead spacecraft.
Unless we’re careful, we’ll pollute the Solar System with wreckage and material that’ll
haunt future generations as they travel from world to world.
I know it’s sad to think about these missions.
Which ones do you already miss, or will you be saddest to see go in the future?
Let me know your thoughts in the comments.
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In our next episode, we’ll talk about the potential for life on icy worlds out there
in the Milky Way.
There could be orders of magnitude more of them than rocky worlds like Earth.
That’s where we should be searching.