Ad Astra (2019)

Judderman

The Iceman cometh
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Sorry going on a tangent, and I haven't watched the film :whistle:! (I do know the basic story, though) But I'm curious what you mean here. I've seen other comments that, I think, talk about regarding this or related to it, but it's clear to me the people commenting didn't understand orbital mechanics. I think you mean something quite specific though, so could you expand?
Yeah that is odd. Debris can repeatedly orbit a planet. All orbits are repeating unless it is something slingshotting around and away. Or not?

Gravity is likely a more accurate film for the Physics. But I think Ad Astra had a poor plot, while gravity had a dreadful love story for plot.
 

Margaret Note Spelling

Try to get as far from the explosion as possible.
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It's also why the Pizza Express pizza "pollo ad astra" brings such an odd image to mind (a gigantic catapult in my case, and a lot of squawking). I've been unable to ascertain what impression they were hoping to give by the name.
The impression of someone linguistically confused on a fundamental level? I can take the concept of sending chickens into outer space, but to do it half in one language and half in another is a bit much.
 

Venusian Broon

Defending the SF genre with terminal intensity
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Yeah that is odd. Debris can repeatedly orbit a planet. All orbits are repeating unless it is something slingshotting around and away. Or not?
Essentially yes. In breaking something in orbit up, either some parts of it may gain enough velocity to escape and fly off into interplanetary space, some of it be may be slowed enough to hit the Earth's atmosphere and burn, and all the rest will go into elliptical orbits (probably) that will repeatedly orbit. And all these orbits should intersect approximately at the point that the breakage occured. They shouldn't all intersect at exactly the same time, I think, but if the explosion causes a normal distribution of velocities, say, to be added to the bits, then there should be a time when the maximum density of 'broken bits' does all come together.

I think Al Jackson is talking about the fact that all the things in orbit are far too close together for the film. And that Russian satellites are in different orbits to the American ones in real life. So even if a Russian satellite did break up, all those new orbits probably wouldn't really cross into Sandra Bullocks path...

...Anyway just a tad curious. Sorry about the aside! Back to something more related to the thread.

I did almost go to see Ad Astra, instead of going to see IT part 2, last week. As I quite enjoyed that, looks like I made a good choice.
 

Bagpuss

Shipwrecked & comatose - where's the mango juice?
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We like to think our new ideas are so unique, don't we? I literally once just added an N to the name Gale and came up with Galen for a character--and then met two actual Galens just months later, and watched Rogue One, and learned it was indeed an real name in circulation.
The name Galen was also used for a Technomage in the short-lived TV series Crusade in 1999. Which I would say beats you and Star Wars. Although, technically, the Greeks manage to beat everyone in naming since Galen of Pergamon was a Greek physician who lived and died in about 210AD. Nothing new under the sun. :)
 

Al Jackson

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Sorry going on a tangent, and I haven't watched the film :whistle:! (I do know the basic story, though) But I'm curious what you mean here. I've seen other comments that, I think, talk about regarding this or related to it, but it's clear to me the people commenting didn't understand orbital mechanics. I think you mean something quite specific though, so could you expand?
Once started the debris cloud will expand to a volume but that structure will follow a mean orbit around the Earth, however the Earth is not a sphere so the gravitational field will cause the orbit to precess so the cloud cannot , in one orbit , takes many orbits, to trace the track orbit of the firs event.
Show what they show , which supposedly happens every 90 min. could not by orbital mechanics happen.
Does not detract from the story tho.
 

Venusian Broon

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Once started the debris cloud will expand to a volume but that structure will follow a mean orbit around the Earth, however the Earth is not a sphere so the gravitational field will cause the orbit to precess so the cloud cannot , in one orbit , takes many orbits, to trace the track orbit of the firs event.
Show what they show , which supposedly happens every 90 min. could not by orbital mechanics happen.
Does not detract from the story tho.
Cheers Al. Thanks for that.

Of course Sandra and George are also precessing along with the debris field anyway, as are all objects in orbit, so we're not worried about the original orbit.

Instead there would need to be a significant change in precess dynamics between the debris cloud and them, I would imagine, otherwise they would just track each other and the 90 min collision timetable would probably hold up at first.

However I haven't done the mathematics of the difference between circular and (slightly more energetic) elliptical orbits wrt precession, so don't know and bow to my betters. :)

My guess would be that, given the initial collision, various factors will start to 'smear' out the debris field so that eventually this 90 min peak becomes irrelevant.
 

Al Jackson

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Cheers Al. Thanks for that.

Of course Sandra and George are also precessing along with the debris field anyway, as are all objects in orbit, so we're not worried about the original orbit.

Instead there would need to be a significant change in precess dynamics between the debris cloud and them, I would imagine, otherwise they would just track each other and the 90 min collision timetable would probably hold up at first.

However I haven't done the mathematics of the difference between circular and (slightly more energetic) elliptical orbits wrt precession, so don't know and bow to my betters. :)

My guess would be that, given the initial collision, various factors will start to 'smear' out the debris field so that eventually this 90 min peak becomes irrelevant.
To get technical , it looked, tho they did not quantify, that the inclination of the debris field had a different orbital inclination from the ISS, therefore the nodal regression rate is going to be different since it is a function of the orbital inclination.
The orbits of the Hubble, the ISS and the Tiangong in the film are not in this universe!
There would be no way an astronaut with a manned maneuvering unit could reach the ISS from Hubble Orbit.
The Tiangong still is not totally assembled , but still It will not be easily reachable from the ISS , it at all, with a Soyuz space craft.

I will note , somebody, back in 2013 wrote a entry for Gravity for Wikipedia that listed it as an 'Alternate Universe Science Fiction story', that is exactly what it is... but Wiki removed that qualification... some bone head moderator did not understand... I guess the movie should of had that in the lead in scrawl !

By the by, someone at JPL was technical for the film, he sent Cuarón 80 pages of 'fix-up' physics for the screen play, but it made the movie run a lot longer than 90 min , so it was not used.

I do know this ...I happened to have worked in manned space flight for 40 years... I knew people who worked ISS and some who knew the Soyuz and said the spacecraft interiors were dead to rights spot on.
 
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