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Gravity: Space Movie
The Truth Behind Gravity's Space Science
In Gravity, we're presented with a survival drama when Sandra Bullock’s character, Dr. Ryan Stone, is thrown into a free-fall after space debris collides with equipment during a spacewalk (or EVA — Extra Vehicular Activity, in NASA-speak).
Since the launch of the 58cm Soviet Sputnik satellite in 1957, hundreds of satellites have made their way into the hostile environment of space — and some have come down in a fiery ball of flames, but many linger up there and may pose a risk for future space operations. Space agencies actively track debris — anything from non-functional satellites to rocket parts, and even the odd spanner lost by an astronaut.
About half of the active 1,000 satellites in space are owned by the U.S., with Russia and China owning about 100 each. However, this only represents about 4% of the total number of man-made objects in orbit.
Most of the large pieces of debris are in orbits that can be calculated, so when agencies plan launches, they can ensure that the most likely collisions are avoided. But it doesn’t always go according to plan.
On more than one occasion, the International Space Station has had to fire its rocket engines to avoid a piece of space junk that could have threatened the orbiting lab.
In the movie, a small piece of rock kicks off the plot, but how realistic is that? Can something so small cause significant damage in space? In short: yes.
To put it into perspective, the ISS orbits at 28,164 kilometers per hour — so fast that scientists usually measure it as about 7.8 kilometers, per second, or 23 times the speed of sound. That means that even a small collision with a fragment of space junk would pose a huge risk, as it would hit the ISS faster than a bullet fired from a high calibre rifle.
A pivotal moment in the film is when Bullock's character is thrown into space after the impact. It's unlikely that mission control would lose contact with an astronaut without the loss of the shuttle, so that was a necessary plot device to convince viewers that radio communications were interrupted. While everything that followed the hit is plausible, the hit itself is unlikely. NASA teams on Earth are obsessive about safety, and constantly monitor astronauts, especially when they are on an EVA.
That doesn’t mean that space travel is without danger — though astronauts are put through a rigorous training program to ensure that they don’t panic when things go pear-shaped, numerous astronauts have died on the launch pad, after launch and during re-entry. The movie pays homage to astronaut Virgil “Gus” Grissom, whose Liberty Bell 7 spacecraft sunk on splashdown, when the hatch door blew off prematurely.
Going to space not only changes your perspective on the world below, but it also alters your body physiologically. Astronauts who return from trips to the ISS are carried out on specially-made seats after touchdown; the lack of gravity in space weakens the body, so once they’re back on Earth, their muscles require time to acclimatize to the weight on their bones.
The fact that Dr. Stone survives in the movie is unsurprising — it follows a regular script for the genre that harks back to Stanley Kubrick’s 2001: A Space Odyssey through to Apollo 13. The heroes must survive.
And that’s where movies differ from reality — in real life, the danger is unlikely, but if something should happen to go wrong, there isn’t always a happy ending. Sometimes, despite years of planning by the best brains in the business, an astronaut’s words can send chills down the spines of engineers at mission control:
“Houston, we have a problem.”