Gravity’s “Science” Problems

Jeff Foust discusses the issue over at The Space Review (spoiler warning for those who haven’t seen it). Also spoiler warning for people who read the rest of the post.

Look, I stand second to none at my annoyance at getting stupid things wrong in movies (stupid as in a complete defiance of physics as we know it in a way that doesn’t even usefully advance a plot), but this seems a little overwrought to me. No, ISS and Hubble (and the Chinese station) aren’t in the same orbital plane. But it wouldn’t defy physics for them to do so. In an alternate history, it might in fact have made sense to put the ISS at Hubble inclination (that was the original plan until the Russians were brought in in 1993), and for the Chinese station to co-orbit with both. It makes no more sense to complain about that than to complain that the movie shows Shuttles still flying.

15 thoughts on “Gravity’s “Science” Problems

  1. Larry J

    I saw the movie yesterday. If you’re willing and able to suspend disbelief on matters like the orbital mechanics being all wrong, then it’s an enjoyable movie. I enjoyed it enough to recommend to some of my coworkers.

    1. Bart

      You would think they would have consultants advising them on OM. Maybe, they did, but said “nah, that’d be too boring.” I guess it depends on how egregiously they got it wrong. If, e.g., they thrusted down to get back to Earth, I don’t know if I could stomach that.

      1. Larry J

        I guess it depends on how egregiously they got it wrong. If, e.g., they thrusted down to get back to Earth, I don’t know if I could stomach that.

        No, they didn’t do that but at the risk of spoilers, they did get a lot of the orbital mechanics wrong. From what I’ve read, they knowingly made these compromises in the name of the story. Believe me, I’ve seen far worse science errors in movies. Overall, I thought the movie was pretty enjoyable. I saw it in 3D but not on an IMAX screen. It isn’t playing at the Space and Rocket Center’s IMAX dome (that might be much for my wife to handle) and the nearest IMAX theater that is showing it is almost 17 miles from my home.

  2. Bart

    I haven’t seen it yet, and would probably only see it for the effects, to experience a simulated thrill of what it is like to be floating in orbit.

    One trailer I saw seemed to show Bullock spinning off into space, but her spin rate appeared to be slowing. I hope they didn’t violate conservation of angular momentum. That would really wreck the experience for me. ISS in the Hubble orbit I could deal with. Fundamental inaccuracy regarding the laws of physics, I could not.

    Has anyone out there seen it? How realistic is it?

    1. rickl

      Well, I’ve never been in space, but I thought it looked pretty realistic. A number of critics are comparing it to 2001: A Space Odyssey in that it permanently raises the bar for how spaceflight is depicted in movies. I agree.

      I saw it on Saturday night. What convinced me to see it wasn’t the movie critics’ reviews, but the high praise it’s been getting from space fans. These are people who know and understand the flaws, but like the movie anyway. Despite the inaccuracies, it’s head and shoulders above most Hollywood space movies. I also like that it depicts real-life spacecraft rather then fictional ones, with great attention to detail.

      If you decide to see it, you should absolutely, positively see it in IMAX 3D if at all possible. This movie was made for that format.

      1. M Puckett

        I think you addressed ISS at Hubble orbit. Would it be practical and desirable to move the Hubble to the same plane as the ISS to facilitate future servicing.

        1. Larry J

          Would it be desirable? Perhaps. Would it be practical? No. It’d take too much energy to move Hubble to ISS’s orbit. Even if you could attach a Centaur upper stage to the Hubble and fire it without causing damage, it wouldn’t be enough. You’d have to refuel the Centaur, probably several times, to have enough energy. If you use a ULA booster to put the Centaur in orbit and refueled it from SpaceX Falcon 9s, it’d still cost from several hundred million to over a billion dollars.

  3. Stephen Fleming

    As I said in my Twitter feed:

    Of course “Gravity” wasn’t scientifically accurate. If it were accurate, everyone would have died in the first five minutes. Creative license. That being said, although it wasn’t scientifically ACCURATE, it wasn’t scientifically INSULTING. And a great roller coaster ride.

    1. Bart

      LOL. I do get bored in movies where the good guys get through a few too many close calls, knowing as I do the geometric progression of the odds.

  4. Bruce Hoult

    There’s nothing inherently wrong in thrusting downwards to deorbit, especially if you’re in a hurry and have fuel to burn.

    Sure, thrusting backwards and waiting half an orbit is the most efficient, but its not the only way.

    Say you’re orbiting 400 km up, and atmosphere starts at around 100 km. If you can cover that distance in significantly less than an orbit — maybe an eighth of an orbit or so — then you can deorbit that way just fine. Let’s say 300 km in 10 minutes (600 seconds) or 500 m/s.

    If you’ve got that delta V available, at a thrust that lets you do it in a couple of minutes or less (half or even a quarter of a G) then yes you can deorbit by thrusting downwards.

  5. Bruce Hoult

    (ok, those numbers are a bit marginal as the slant distance will increase too fast. But 1000 m/s deltaV at 1 G or more will certainly work.)

  6. MfK

    I just saw it in 3D IMAX, and highly recommend it. There were far fewer errors than in Apollo 13 (both technical and historical, and one of the latter was absolutely libelous), and hardware detail was amazing. In fact, there was only one hardware error I spotted, and it was necessary for the story. It is a visual feast from beginning to end.

    One challenge to you all: tell me where you see the Face on Mars. It’s in there, no question about it.

  7. reader

    The movie is absolute junk. The button in second row third column on Shenzou control console says ‘General Shaos chicken’. How realistic is that ?

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