Gravity - SPOILERS; discussion of Earth orbit

Just saw Gravity. It's definitely a movie to see in the theater to really feel the immensity of the "setting". It was a really good movie. I didn't have a problem with suspension of disbelief during the movie, for the thrill of the story. But stepping out of it and talking about it as "science":

Would a space-walking astronaut really be flying around, (playing around), like that? That seemed very dangerous, not to mention a waste of resources for just playing around.

Would that many satellites be taken out that quickly by the debris of just one satellite? Space is HUUUUUUGE. Even with thousands of satellites in orbit, they are so small and the space between them is vast.

Would the Hubble telescope, the ISS, and the Tiagong really all be that close together in orbit? All that space to work in, and they're within visual range of the unaided eyeball?

Would it even be possible to find and retrieve anyone flung away from a space base like that? Again, space is huge, a person is so small, and the speed is pretty fast.

Bullgrit

Michael Bay was a consultant. This is why there are so many collisions and esplosions.

I can't comment much, as I haven't seen the movie.

The ISS orbits at a height of 230 miles above the surface of Earth.
The Hubble Telescope orbits at 347 miles.

So, leaving out other characteristics of their orbit for a moment, the closes these two can ever be is 117 miles apart. In actuality, I don't think they can even get that close, but I'd have to go look up the orbital parameters to be sure.

My main concern would be that most probable collisions would have such a high delta-V that the impact would occur too quickly to be visibly interesting, or reacted to except after the fact.

Aren't satellites often visible, if you know where to look, and the viewing conditions are good?

I'm finding these:

ISS:

Perigee 417 km (259 mi) AMSL[1]
Apogee 420 km (260 mi) AMSL[1]
Orbital inclination 51.65 degrees[1]
Average speed 7.66 kilometres per second (27,600 km/h; 17,100 mph)[1]

Hubble:

Type of orbit Near-circular low Earth orbit
Orbit height 559 km (347 mi)
Orbit period 96–97 minutes (14–15 periods per day)
Orbit velocity 7,500 m/s (25,000 ft/s)

Both from wikepedia.

Hurrah for consistency. Had to go to a Hubble site for the inclination:

inclined 28.5 degrees

Won't the main concern be the inclination and orbital velocity? I thought those were bigger components of the energy requirements to match orbits than the change in elevation.

Also, for a satellite that exploded, I'd expect that to disperse pretty quickly, making a wide but very sparse debris field.

Thx!

TomB

The differences in inclination are significant -- the equivalent of placing the actual objects thousands of miles apart (I've heard the analogy being the real world situation would be more akin to falling overboard from a ship in the Caribbean and having to swim to London for rescue).

Here's one good article about the science.

I suggest checking this article out (in addition to the reference from [MENTION=5868]Olgar Shiverstone[/MENTION] above).

As far as I understand it, the relative distances of the space stations and the Hubble were unrealistically close. A jet pack would not be able to navigate those distances effectively. The fire extinguisher trick probably wouldn't work. Also, Kowalski would not have been pulling her because there is (ironically) no gravity to pull him, so once his initial movement was stopped, he would have come back easily. No reason to dump him; you can't be a dead weight if you have no weight.

There's also a lot of dramatic conceit. It's awfully convenient that everything goes wrong at just the time it does, that the fuel runs out just as they reach the ISS, that the fire starts just when it does, that the pod lands in water, but right next to a shore with a nice calm sandy beach. Like all dramatic conceits, these things could happen, and real people have had similarly absurd coincidences, but after a few of these strung in a row there is a bit of eye-rolling from my seat.

And then there is a dose of sentiment. At least they justified the hallucination by the lack of oxygen, but I could have done without the whole "finding her spirituality" angle. Or at least, I don't think it needed to be so heavy-handed. Just tell the story, and let us decide what it means.

***

That being said, I also agree that the movie was tremendously entertaining, and that its flaws were small enough that I was still able to enjoy it. The visceral experience of being in space was quite impressive and well realized, and the central characters were easy to connect to. It is an excellent movie.

Ahnehnois said:

Kowalski would not have been pulling her because there is (ironically) no gravity to pull him, so once his initial movement was stopped, he would have come back easily. No reason to dump him; you can't be a dead weight if you have no weight.

Read more: http://www.enworld.org/forum/showth...ILERS-discussion-of-Earth-orbit#ixzz2h4z78G7E

Click to expand...

But he still has mass, which in that situation would have the same result as weight. Yes?

Stone and Kowalski were, indeed, extremely lucky throughout. Granted, it could be said they were very unlucky what with all the terrible catastrophes, but just not getting killed by the debris field *twice* was luck.

Bullgrit

Bullgrit said:

But he still has mass, which in that situation would have the same result as weight. Yes?

Click to expand...

No. He had momentum, but when he got caught in the lines, one of two things could happen. Either the line would break immediately, or his momentum would be stopped. There was no force that would cause him to keep pulling on the line once his momentum was stopped (which it was, he basically was not moving). As my reference above explains, the way this scene played out made sense from an Earth dweller's perspective, but is not accurate physics for the environment they were in.

Stone and Kowalski were, indeed, extremely lucky throughout. Granted, it could be said they were very unlucky what with all the terrible catastrophes, but just not getting killed by the debris field *twice* was luck.

Click to expand...

True, but that's mitigated to some extent by the other people that died, and by the fact that it's possible. It's clear that these people survived extreme odds, but that's why we're watching the movie in the first place.

It's also convenient that the people who died were nobodies while the two that survived were Big Hollywood Stars, though this is also mitigated by the fact that astronauts really are the cream of the crop, and they are likely to be exceptionally attractive and charismatic people.

Ahnehnois said:

No. He had momentum, but when he got caught in the lines, one of two things could happen. Either the line would break immediately, or his momentum would be stopped. There was no force that would cause him to keep pulling on the line once his momentum was stopped (which it was, he basically was not moving). As my reference above explains, the way this scene played out made sense from an Earth dweller's perspective, but is not accurate physics for the environment they were in.

Read more: http://www.enworld.org/forum/showth...ILERS-discussion-of-Earth-orbit#ixzz2h57L6Lhm

Click to expand...

At the point where Kowalski was "hanging" by the tether, Stone couldn't pull him in because pulling his mass toward her would pull against the tangled parachute cords holding them. That's what I'm talking about. But yeah, once he disconnected from the tether, he should have just "floated" there instead of slowly falling away.

* * *

When Stone removed her spacesuit, my first thought was, "Don't astronauts wear layers of stuff, with cooling systems built in?" But then when I saw Bullock in her undies, that thought was dismissed

Bullgrit

Neil deGrasse Tyson notes on the movie has made me decide not to see it.

[sblock]Sandra's hair not effected by gravity. Sandra is a MD and is repairing Hubble, plus a few other issues. See: http://www.nydailynews.com/entertai...tioned-famed-astrophysicist-article-1.1478430[/sblock]