'Gravity': It's Not Rocket Science!

[Editor's note: Spoiler alert: If you haven't seen Gravity, this piece reveals some key parts of plot.]

The director of Gravity, Alfonso Cuaron, has admitted that the Oscar-contending film is not always scientifically accurate and that some liberties were taken to sustain the story. "This is not a documentary. It is a piece of fiction." Indeed, there are so many scientific inaccuracies in the film that the 10 listed below represent but a small faction of the whole: 

1. Gravity opens with George Clooney doing a very good impression of Buzz Lightyear orbiting around the Space Shuttle in his manned manoeuvring unit (MMU). The unit in question was used on the shuttle from 1983-1984. After the Challenger disaster, the MMU was deemed too risky for future use in extra-vehicular activities (EVAs). From that point onwards, the Canadarm and traditional, tethered EVAs fulfilled the tasks the MMU was designed for. 

2. Gravity depicts three astronauts working on EVA -- Kowalski, Stone and Shariff. Only once in the recorded history of the Shuttle have three astronauts gone EVA at the same time. This was during STS-49 in 1992, and only because of a very difficult satellite recovery. It is hardly a typical scenario. It would not happen during a Hubble Telescope repair mission.

3. Astronauts train together for years and know everything about each other, yet Kowalski asks questions of Stone about her personal life. By the time astronauts go on a mission together, they are already familiar with one another's domestic situation.

4. The plot of Gravity is based around Kowalski and Stone literally hopping between three spacecraft orbiting the earth, i.e. the Space Shuttle, ISS, and Tiangong-3 (with the latter not slated to launch for another five years). But Space is BIG and the three spacecraft are all at different orbital inclinations and altitudes. (An orbital inclination is the angle that a spaceship orbits the earth in relation to the equator). For instance, after the Space Shuttle and Hubble Telescope are destroyed, Stone and Kowalski tether together and set off for the International Space Station (ISS). To service the Hubble Telescope the Space Shuttle has to launch on a 28.5 degree orbital inclinational. In contrast, the ISS orbits on a 51.6 degree orbital inclination. The distances involved are truly massive and impossible to cover using a small manoeuvering unit.

5. In the first few minutes of the movie, communication with the ground is lost as the relay satellites are destroyed by the same debris field that damages the Space Shuttle. But this would not happen, because the NASA relay satellites used to communicate with the Shuttle are located in a geo-synchronous orbit (an orbit at which the speed is equal to the Earth's rotation making the object seem motionless from the ground). The supposed debris field is located at the 300-500 km altitude while the relay satellites are located almost 35,000 km away. If Gravity had got this fact correct, the astronauts would have lost contact with Houston, since EVA communication is relayed through the parent spacecraft. But they would have regained contact with Houston when they reached the ISS.

6. Early in the movie, we hear that the ISS was ordered to evacuate because of the debris heading its way. But as Kowalski and Stone are heading towards the ISS, Kowalski comments that the ISS must have been evacuated as one Soyuz is missing. This statement does not make sense, for if there are two Soyuz docked, there must be at least six crew members on the ISS. Under NASA regulations, there must always be enough seats to evacuate the station. Each Soyuz takes three astronauts, so both Soyuz should have left for Earth, not just one.

7. As Gravity depicts, Soyuz is fitted with four small soft landing engines that are designed to fire three metres above the ground. Stone uses the soft landing engines on the Soyuz to get to the Tiangong after she discovers Soyuz is out of fuel. Stone achieves this by setting the altitude on the Soyuz down to three metres. But this would not have worked -- because the soft landing engines are activated by a radar altitude system and this would be impossible to change.

8. Kowalski sacrifices himself to give Stone a chance of survival. But he didn't have to die. The movie shows Kowalski being pulled uncontrollably away from the ISS, even though, at that time, there would not have been any centrifugal force pulling him away because he was not moving in relation to the station. Kowalski should have been static in space and able to pull himself back towards Stone.

9. Gravity depicts Stone taking off her spacesuit inside the PIRS airlock. And the space suit she takes off has just one layer. But spacesuits have many layers, including a Maximum Absorbency Garment (MAG), a Thermal Control Undergarment, and a Liquid Cooling and Ventilation Garment (LCVG). Stone should have been wearing many layers of clothes. Moreover, when Stone goes on an EVA to remove the parachute she dons a Sokul spacesuit -- which is incapable of being used during EVAs and is only designed to keep the astronaut alive during ascent and re-entry.

10. The Simplified Aid for EVA Rescue (SAFER) is a device developed during the shuttle programme and used on the ISS for astronauts to use if they are separated from the ISS during EVAs. It is basically a simplified manned manoeuvring unit (MMU). Gravity is set around a fictitious Hubble Repair mission around the year 2013. As the SAFER is currently used for all EVAs on the ISS, it would follow that the SAFER would be used on the mission depicted in Gravity. And this would have avoided Stone's spinning scene because she could have used the SAFER to rectify the situation.

There are many more things that could be said about all inaccuracies in Gravity. My major concern -- as a 13-year-old with a strong interest in science -- is that the film will serve to decrease the scientific understanding of its viewers, including kids like me. A better movie would have seized the opportunity to promote knowledge through accuracy. Science is exciting. Space is exciting. There's just no need to make stuff up!