NASA expert explains what the Gravity trailer gets wrong

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Sep 6, 2013, 3:05 PM EDT (Updated)

I usually try not to nitpick space movies, because they are entertainment, not documentaries, but when folks start heaping praise on a movie as the best space movie or most realistic, I feel the need to chime in.

In the first trailer for Gravity, the relative motion appears wrong based on my experience of flying the shuttle in Mission Control for 11 years. I worked here at the Johnson Space Center as a Guidance, Navigation and Control Officer (making sure the shuttle knew where it was, where it was going and how it was going to get there) as well as the Mission Ops liaison to the Orbiter Project (making sure the guys who were responsible for the shuttle hardware knew what the operations team was doing).

The way I am seeing it, the shuttle was wings level, payload bay up (Z), right wing into the orbital velocity vector (X direction of travel), nose in Y. The Micrometeoroid and Orbital Debris [MMOD] (though most were not really micro Meteoroid) impact puts it into a roll about Y with it still traveling in the velocity vector X, and why are the Forward and Aft reaction control jets not firing to damp the ramp since they were intact in the trailer? When the Remote Manipulator System (RMS, the Shuttle robotic arm) breaks, it was rolling and moving forward with the shuttle, but then with the camera and the Earth in the background the arm goes into a radial direction (Z) away from the earth (thus the opening rate between the shuttle and RMS making it seem like the shuttle is plunging down) with a tumble about the radial axis (now a roll about X).

Then they show her unstrapping from the tumbling RMS, which isn't going to change her velocity vector, since she was tumbling with the RMS, thus has the same motion and velocity as the RMS. Unstrapping doesn't arrest that rate. Maybe her EMU (space suit) had a SAFER (Simplified Aid for EVA Rescue) to arrest her rate, but it would be pretty limited propellant for her to then be able to get back to Clooney. All that MMOD and she doesn't take a leak seems highly unlikely given the big stuff is usually surrounded by lots of hypervelocity small stuff. And since Clooney was still in the debris field, how did he not get shredded when the shuttle did? Not to mention her freakout does a disservice to every female astronaut out there and would eat through her 6-8 hrs of metabolic suit O2 very quickly.

If it is just her and Clooney, assuming she somehow got back to him after being flung away on the RMS free floating trying to get to the space station without a vehicle, that seems unlikely, unless the two orbits just magically intersect at the exact right time for them to be anywhere near the ISS. For example, on STS-107, even if the crew knew about the damage, there was no way to get to the space station, because they were in two different orbital inclinations and the shuttle doesn’t have enough propellant for a plane change like that.

Rendezvous in space is a complicated ballet of orbital mechanics and Clooney’s MMU would have nowhere near the propellant to pull it off. Plus, they show her touching the solar arrays, which would be highly charged with potential energy (when we had to repair the solar array that failed to properly deploy every tool had to be protected for arcing and the crew had to be careful to not touch the array for electrocution, or suit damage), but I guess as you are zooming by at 17,500 mph it is grab the solar array or die.

I am all for an entertaining movie, but when I go into a Michael Bay Armageddon movie I know to turn the brain off. This one tries to pass itself off as something more than that, but to me, it is the same flash and sizzle with a pretty lax understanding of orbital mechanics and spaceflight operations. Europa Report, on the other hand, did a good job of spaceflight operations, though I am sure some folks may find that movie a little boring given that realistic space exploration is slow and methodical compared to Gravity.

So Gravity is a pass for me, and given the loss of the shuttle in the trailer, it hits a little too close to home.

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