'Gravity' gets much of the science right

I love sci-fi movies but hate it when the science is needlessly trampled by the fiction. There are no such problems in Alfonso Cuarón's immersive science-fiction action thriller "Gravity". The film gets so much right, so little wrong and only gets the sci wrong when the fi demands it.

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Tools used by spacewalking astronauts
Tony Rice

I love sci-fi movies but hate it when the science is needlessly trampled by the fiction. There are no such problems in Alfonso Cuarón’s immersive science-fiction action thriller "Gravity". The film gets so much right, so little wrong and only gets the sci wrong when the fi demands it.

The characterization of Sandra Bullock's character as an expert at the job she was sent to do (repair the Hubble Space Telescope) though less than 100 percent prepared to step beyond that is spot on. Every astronaut who has worn a shuttle mission patch trains to land the orbiter in an emergency. Mission specialists aren't nearly as good at this as pilots and mission commanders. The veteran astronaut played by George Clooney also reminded me of every Apollo or early Shuttle era astronaut I've had the privilege to meet. Extremely confident, cool as a cucumber and full of stories.

The film's science advisor, Dr. Kevin Grazier, did a commendable job of ensuring the science was right. He teaches astronomy courses at UCLA and works at NASA's Jet Propulsion Laboratory on the Cassini/Huygens Mission team studying Saturn and Titan. Grazier also authored a series of "Science of" books on Dune and Battlestar Galactica. He drew on that to help the filmmakers get a lot of little things right:

  • Water droplets (surface tension) and fire (heat pushing out in all directions) as accurately shown as spherical in space.
  • Nausea is a very real problem for even the toughest astronauts, especially on their first flight.
  • The oversized tools used by Bullock's character in repairing Hubble Space Telescope (HST) are very accurate.
  • Instead of random dots on a black background, real constellations represented behind astronauts.
  • The accuracy of the Space Shuttle Orbiter, International Space Station (ISS) and Soyuz sets are impressive. Set decorators even got the make and model of laptops used aboard the ISS right. Yes, there are more than 60 of those ancient looking IBM/Lenovo ThinkPads on the ISS.
  • The spacesuits and helmets are remarkably accurate

It wasn't just the little nit-picky things that filmmakers got right. 

Significant plot points are based in real science. It's worth warning that there are spoilers beyond here.

The cascade of satellite destruction which provides the conflict for the story is a very real threat as the number of objects in Low Earth Orbit (LEO) increase. The problem was first proposed in 1978 by orbital debris expert Donald J. Kessler.

Kessler retired from NASA in 1996 but continues to study the problem of orbital debris and served as technical adviser on the Space Junk 3D film shown at the North Carolina Museum of Natural Sciences last year.

Clooney calculates the time remaining before the debris field reaches them at 90 minutes. This matches up nicely with the orbital period of objects in (LEO).

The Chinese Shenzhou capsule is essentially an upgraded version of the Russian Soyuz. Avionic technology was purchased from Russia in the mid-1990s. An astronaut familiar with one should be able to pilot the other.

The right debris hit triggering explosive charges to deploy the parachutes aboard the Soyuz on orbit seems possible.

Newton's 3rd law of motion is demonstrated well as Bullock's character turns a fire extinguisher into a rocket engine. She improves control as she moves the nozzle towards her center of gravity.

The retrorockets on Soyuz spacecraft used by Bullock's character to escape the ISS do exist and are used to cushion landing. They are seen again on the Shenzhou (see above).

Unlike American capsules which are designed for water landings, Shenzhou and the predecessor Soyuz capsules normally land on solid ground.

The one Soyuz water landing did not go well. In 1976, the crew of Soyuz 23 landed in a lake in blizzard conditions, the parachute filled with water and submerged the escape hatch. Cosmonauts waited 9 hours in frigid conditions for rescue.

As Bullock's character nearly gives up, her plan to reduce the oxygen in the cabin and just "go to sleep" is probably the least painful way to go.

Still, this is a work of fiction, not a documentary. Science must be sacrificed in the name of storytelling. It was mostly orbital mechanics that took one for the team:

Rendezvousing in orbit requires significantly more time and precision than was available in the movie, so shortcuts were required.

The ISS, HST (and visiting shuttle) and Tiangong 1 orbit the Earth on very different inclinations (28.5º, 51.6º and 42.8° respectively.) They are moving in very different directions as a result. Getting from one to the other is not as simple as changing lanes on Interstate 40 and requires significantly more time and precision than available in the film.

In reality, the ISS, HST and Tiangong are separated by 4,000+ miles and are below the horizon. Space, even Low Earth Orbit, is a big place, and translating that to a movie screen is really difficult.

The Manned Maneuvering Unit (MMU) Clooney's character jets around on in the opening scenes does exist but was used only on three early shuttle missions and not since 1984. You can see space flown MMUs today hanging above space-flown shuttle orbiters at the Air and Space Museum and Kennedy Space Center Visitor Complex.

The MMU was capable only of short bursts to move astronauts around the shuttle, not crossing distances portrayed in the film and certainly not in the time presented. But it was certainly a cool way to get Bullock and Clooney into the second act.

Overall I really enjoyed this movie, not just for the attention to detail but for its immersive approach to filming. I think I even caught the lady sitting in front of me gulping for air at a pivotal point.

The use of sound effects and most importantly, silence make a large contribution to the overall experience. I'll see it again and next time on an IMAX screen.

Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie. 


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