Just been to see the movie. Visually very impressive. The depictions of zero G are masterful. Was wondering about the science.

What would be the interior temperature of an orbiting but (temporarily?) unmanned space station, with electrical systems in slumber mode? Power presumably derived from solar panels.

A plot device in this movie is that an astronaut makes her way from a space station in one orbit to one in another orbit. Assuming that the difference in orbit altitude (distance from Earth) is 50 km, what would be the difference in linear velocity? Do US and Soviet space stations orbit at the same altitude? Is there some sort of convention?

What is the tonnage of orbiting space junk? If an item exploded, what is the probability that shrapnel would strike another item?

Any other comments?

pesce.del.giorno said:

Just been to see the movie. Visually very impressive. The depictions of zero G are masterful. Was wondering about the science.

What would be the interior temperature of an orbiting but (temporarily?) unmanned space station, with electrical systems in slumber mode? Power presumably derived from solar panels.
——————-
It would depend on the surface area and thermal conductivity. It could go from extremely cold when shadowed by the earth to quite hot when in direct sunshine

A plot device in this movie is that an astronaut makes her way from a space station in one orbit to one in another orbit. Assuming that the difference in orbit altitude (distance from Earth) is 50 km, what would be the difference in linear velocity?
—————-
Dunno

Do US and Soviet space stations orbit at the same altitude?
———————-
Yes exactly the same altitude. (they are one and the same at present – ISS)

Is there some sort of convention? ——————— I think there is an authority that specifies orbital heights… I think…

What is the tonnage of orbiting space junk?
———————
Google

If an item exploded, what is the probability that shrapnel would strike another item? ————————— Not much. Space is huge, mind bogglingly huge…

each country is allocated space around the earth I believe

what would be the difference in linear velocity?
———————————————
Thats not important to the plot…

Mr Ironic said:

what would be the difference in linear velocity?
———————————————
Thats not important to the plot…

(SPOILER ALERT)

Well, the heroine makes her way from one space station to another and docks on it by modifying her velocity with a fire extinguisher. That wouldn’t be possible if the closing speed was very high.

if the difference was only 50km then the difference in speed would be bugger all. orbital velocity is measured from the centre of the earth so 50km added to the ~6300km radius of the earth + the orbit height.

http://cde.nwc.edu/SCI2108/course_documents/formulae/orbital_velocity.htm

and docks on it by modifying her velocity with a fire extinguisher.
—————————————————-

Really… She is outside the station with a fire exting…

How the fuck does that work in space?

How the fuck does that work in space?

mass goes one way astronaut goes t’other. i think newton worked that one out.

Not repeal gas…

A FIRE!

Don’t let the locals hear about it…

fire in space? easy fuel + oxidiser. reason why a gun will work in space. the potassium nitrate provides the oxygen.

you’d need to accelerate to travel up an orbit or you’d crash into the thing flying along above you. you’d not see by eye I reckon so the chances of even being hit by it is remote

to change orbit you need to do burns, either prograde or retograde, at specific points in your orbit. you can’t just do them anywhere.

fire in space? easy fuel + oxidiser.
————————————-

yeah as common as muck. CO2 must work a treat and must always be handy.

Ah well live and learn.

at specific points in your orbit. you can’t just do them anywhere.
————————————-

Ok. I’m listening. Why not?

the iss has co2 extinguishers.

http://news.discovery.com/space/history-of-space/firefighting-in-space-nasa-120210.htm

russian service modules use water based foam i think.

the burns would have to be timed so you meet your destination at the right time and place

ChrispenEvan said:

to change orbit you need to do burns, either prograde or retograde, at specific points in your orbit. you can’t just do them anywhere.

Indeed, it is rocket science.

well if you want a specific outcome then they have to be done at specific points. of course you can do any old thing at any old time but thats to get you to any old place you probably don’t want to go.

Um, since we are talking about a movie, I’d rather wait until I see it before commenting on the movie.

we’ve gone past the movie. i heard it had real astronauts giving advice and that it is pretty true to science.

ChrispenEvan said:

we’ve gone past the movie. i heard it had real astronauts giving advice and that it is pretty true to science.

—

so gravitas…

wookiemeister said:

you’d need to accelerate to travel up an orbit or you’d crash into the thing flying along above you. you’d not see by eye I reckon so the chances of even being hit by it is remote

You actually need to de-cellerate to go to a higher orbit.

Stealth said:

wookiemeister said:

you’d need to accelerate to travel up an orbit or you’d crash into the thing flying along above you. you’d not see by eye I reckon so the chances of even being hit by it is remote

You actually need to de-cellerate to go to a higher orbit.

—-

Depending on direction…

well if you want a specific outcome then they have to be done at specific points.
————————————————————————

Yeah the human… that drives what computers cannot.

Yeah the human… that drives what computers cannot.

this may make sense to you but it doesn’t to me.

Yeah the human… that drives what computers cannot.

this may make sense to you but it doesn’t to me.
————————————

Yes.

Point selection is OK in trials but really needs some man management at the time and place of the event.

Yeah humans. (As in, no fucking chance of doing that shit with out an astronaut.)

Hope that helps.

so how are satellites boosted from leo to geo?

ChrispenEvan said:

so how are satellites boosted from leo to geo?

Rockets…

…or really big gings.

i just said we waliens were sensible stealth. don’t let the side down.

;-)

ChrispenEvan said:

so how are satellites boosted from leo to geo?

—

by boosters ;)

to change orbit you need to do burns, either prograde or retograde, at specific points in your orbit. you can’t just do them anywhere.

i should add that if you had oodles of fuel then you could “fly” your spaceship like they do in star wars etc. the above really applies to realistic spaceflight.

Stealth said:

wookiemeister said:

you’d need to accelerate to travel up an orbit or you’d crash into the thing flying along above you. you’d not see by eye I reckon so the chances of even being hit by it is remote

You actually need to de-cellerate to go to a higher orbit.

An orbital spaceflight (or orbital flight) is a spaceflight in which a spacecraft is placed on a trajectory where it could remain in space for at least one orbit. To do this around the Earth, it must be on a free trajectory which has an altitude at perigee (altitude at closest approach) above 100 kilometers (62 mi) (this is, by at least one convention, the boundary of space). To remain in orbit at this altitude requires an orbital speed of ~7.8 km/s. Orbital speed is slower for higher orbits, but attaining them requires higher delta-v.
http://en.wikipedia.org/wiki/Orbital_spaceflight

assuming that delta V means acceleration I stand by my original statement

>>100 kilometers (62 mi) (this is, by at least one convention, the boundary of space)

I think it was Arthur C Clarke who said that people think of outer space as being a long way away, when it’s basically an hour’s drive straight up.

the earth has a very thin sliver of atmosphere this is why its very important to safeguard its integrity

its provides protection from the sun’s radiation

provides protection from most bombardment from wandering rocks

provides the lifesupport for most life here

wookiemeister said:

Stealth said:

wookiemeister said:

you’d need to accelerate to travel up an orbit or you’d crash into the thing flying along above you. you’d not see by eye I reckon so the chances of even being hit by it is remote

You actually need to de-cellerate to go to a higher orbit.

An orbital spaceflight (or orbital flight) is a spaceflight in which a spacecraft is placed on a trajectory where it could remain in space for at least one orbit. To do this around the Earth, it must be on a free trajectory which has an altitude at perigee (altitude at closest approach) above 100 kilometers (62 mi) (this is, by at least one convention, the boundary of space). To remain in orbit at this altitude requires an orbital speed of ~7.8 km/s. Orbital speed is slower for higher orbits, but attaining them requires higher delta-v.
http://en.wikipedia.org/wiki/Orbital_spaceflight

assuming that delta V means acceleration I stand by my original statement

A Hohmann transfer use two impulses (from rockets) to move a satellite to a higher or lower orbit. When going to a higher orbit the first impulse does indeed increase the velocity of the satellite. When the satelllite reaches the required altitude then a second impulse also increases the velocity to circularise the orbit. But even though both impulses speed the satellite up, it must be remembered that the satellite loses velocity during the climb to the higher orbit. The sum total of the two impulses is smaller than the velocity lost during the climb so the satellite ends up with a lower orbital velocity. Overall negative work is done.

Stealth said:

wookiemeister said:

Stealth said:

You actually need to de-cellerate to go to a higher orbit.

An orbital spaceflight (or orbital flight) is a spaceflight in which a spacecraft is placed on a trajectory where it could remain in space for at least one orbit. To do this around the Earth, it must be on a free trajectory which has an altitude at perigee (altitude at closest approach) above 100 kilometers (62 mi) (this is, by at least one convention, the boundary of space). To remain in orbit at this altitude requires an orbital speed of ~7.8 km/s. Orbital speed is slower for higher orbits, but attaining them requires higher delta-v.
http://en.wikipedia.org/wiki/Orbital_spaceflight

assuming that delta V means acceleration I stand by my original statement

A Hohmann transfer use two impulses (from rockets) to move a satellite to a higher or lower orbit. When going to a higher orbit the first impulse does indeed increase the velocity of the satellite. When the satelllite reaches the required altitude then a second impulse also increases the velocity to circularise the orbit. But even though both impulses speed the satellite up, it must be remembered that the satellite loses velocity during the climb to the higher orbit. The sum total of the two impulses is smaller than the velocity lost during the climb so the satellite ends up with a lower orbital velocity. Overall negative work is done.

either way at a practical level it would be difficult to aim yourself at something you wouldn’t be able to see, 50km away even in direct line of sight would be impossible to judge.

you wouldn’t be able to see an object such as a spacecraft at 50 km against the sky

you wouldn’t be able to judge the speed of the spacecraft

you wouldn’t be able to see an object such as a spacecraft at 50 km against the sky
—————————-
I have seen orbiting spacecraft from the surface of the earth, which is a lot further than 50km and has all that atmosphere stuff to look through as well. Sure the lighting conditions need to be favourable…

Stealth said:

you wouldn’t be able to see an object such as a spacecraft at 50 km against the sky
—————————-
I have seen orbiting spacecraft from the surface of the earth, which is a lot further than 50km and has all that atmosphere stuff to look through as well. Sure the lighting conditions need to be favourable…

yes but you wouldn’t have known exactly what you were looking at, one piece of junk will exactly like another piece of junk at 50km

myth busted

Wookie Report is early tonight.

Oppp sorry. That was meant for chat.

Clock shifts disrupt sleep and reduce its efficiency. Effects on seasonal adaptation of the circadian rhythm can be severe and last for weeks. A 2008 study found that male suicide rates rise in the weeks after the spring transition. A 2008 Swedish study found that heart attacks were significantly more common the first three weekdays after the spring transition, and significantly less common the first weekday after the autumn transition. The government of Kazakhstan cited health complications due to clock shifts as a reason for abolishing DST in 2005.
http://preventdisease.com/news/12/031212_Daylight-Savings-Only-Benefits-The-Oil-and-Gas-Industry-Negatively-Impacts-Our-Health.shtml

my own feeling about DST is that it just sends people mad

i’d ban it on health grounds and just let people get up when they want

people have been brainwashed into thinking its some amazing time saving device

don’t fight the wookie force, once you allow its notions to wash over you everything seems clear

join ussssssssss

pesce.del.giorno said:

the heroine makes her way from one space station to another and docks on it by modifying her velocity with a fire extinguisher. That wouldn’t be possible if the closing speed was very high.

Sure, the fire extinguisher needs to be able to provide enough delta-vee at both ends of the transfer. So it needs to contain enough useful potential energy, and it needs to be able to release that energy with sufficient rapidity to generate the required momentum. However, the astronaut can also get a bit more momentum from the extinguisher by chucking it when it’s empty.

In a simple Hohmann transfer orbit (from one circular orbit to another), the second “burn” not only circularises the orbit, it also ensures that the speed of the transferring body is exactly equal to that of the destination body.

Stealth said:

A Hohmann transfer use two impulses (from rockets) to move a satellite to a higher or lower orbit. When going to a higher orbit the first impulse does indeed increase the velocity of the satellite. When the satellite reaches the required altitude then a second impulse also increases the velocity to circularise the orbit. But even though both impulses speed the satellite up, it must be remembered that the satellite loses velocity during the climb to the higher orbit. The sum total of the two impulses is smaller than the velocity lost during the climb so the satellite ends up with a lower orbital velocity. Overall negative work is done.

Indeed. A Hohmann transfer is the most energy-efficient way to do the transfer, but it’s not particularly intuitive to execute by eye. OTOH, the maths isn’t that hard, but you do need to have good figures for the start & destination orbits. Ideally, you want the radii of both orbits and preferably the orbital speeds, although the speeds are straight-forward to calculate from the radii. Still, I’d hate to have to do that stuff in my head; I hope the astronaut in the movie had access to a calculator.

FWIW, the basic Hohmann transfer speed formula is w = v * sqrt(radius2 / radius1) where radius1 & radius 2 are the radii of the start & destination orbits, w is the speed of the transferring body after the 1st burn and v is the orbital speed of the start orbit. This formula works whether radius1 is less than or greater than radius2, so it can also be used to calculate the speed for the 2nd burn.

But the tricky part is getting the timing right for the initial burn. In an exact Hohmann transfer, both burns are tangential to your orbit (hence roughly at right angles to the direction you want to go), but I guess in practice you can modify the direction of the 2nd burn, presuming you have fuel / reaction mass to spare.

Just got back from seeing it.
Oh my it’s good, I’m quite drained now. The action sequences are mind-buggeringly good though as mentioned above the reality of the whole thing is a tad dubious. But it’s sooooo well done.

Haven’t read the comments of others, so possibly I’ll be repeating what’s already been said.

The basic premise for the film is so preposterous that it severely limited my enjoyment of the film.

If the Russians used a missile to blow up one of their own satellites, it would be a remarkable thing if a piece of debris hit another satellite. There would be no possibility of a “debris chain reaction” knocking out earth’s communications satellites (most of which, in any case, are in geostationary orbit, not low earth orbit with the ISS.) The energetics are just ridiculous. The thing is that this complication was completely unnecessary for the plot. They could have just said that the comms for the ISS and Shuttle were knocked out by debris from the explosion: unlikely but not impossible.

The ISS is never near the Hubble Space telescope. Different orbital plane, very different altitude.

If you were 100 miles from the Shenzhou, it would just look like a starlike dot, not an object with clear physical shape.

I can almost believe that scanning software or hardware used for medical imaging could be applied to astronomical applications. It could happen. But the person who develops the software or hardware won’t be a medico. They’ll be an engineer. And the person who goes spacewalking to do the upgrade on the HST will not be the engineer who designed it.

What the heck was Clooney’s character doing loops for at the start of the movie? Just wasting fuel? Having fun? And the Russian bouncing around on his tether? NASA doesn’t allow all that clowning around.

The thing is, with minor rewrites that did not cause significant change to the merits of the film, all of these problems could be eliminated.
I never really connected with the characters. The dialogue was not entirely naturalistic, and the exposition was clumsy.

The visuals are pretty, and some of the microgravity physics is good. Not enough to make up for the problems. Big disappointment.

Distribution of Space Debris (as of 2009)

http://www.dlr.de/en/desktopdefault.aspx/tabid-5170/8702_read-18916/

Ogmog said:

Distribution of Space Debris (as of 2009)

http://www.dlr.de/en/desktopdefault.aspx/tabid-5170/8702_read-18916/

space weather means a fair amount gets blown away

wookiemeister said:

Ogmog said:

Distribution of Space Debris (as of 2009)

http://www.dlr.de/en/desktopdefault.aspx/tabid-5170/8702_read-18916/

space weather means a fair amount gets blown away

NASA & The Weather Channel CONCERNING SPACE DEBRIS: http://bcove.me/7c7p3bdm
(Click “Enlarging Icon” to view full-screen)

For Deevs.

http://www.theverge.com/2013/10/7/4811336/neil-degrasse-tyson-isnt-falling-for-gravity

I quite agree there’s quite a lot technically incorrect with it but if you are able to put that aside it’s one of the better space moofies.

Neil deGrasse Tyson ‏@neiltyson 6 Oct

Mysteries of #Gravity: Why Bullock’s hair, in otherwise convincing zero-G scenes, did not float freely on her head.

Divine Angel said:

Neil deGrasse Tyson ‏@neiltyson 6 Oct

Mysteries of #Gravity: Why Bullock’s hair, in otherwise convincing zero-G scenes, did not float freely on her head.

Yep there’s a lot wrong with it. But it’s still one of the better spacey moofies I reckon. Well worth seeing in a 3D cinema.

Spiny Norman said:

Yep there’s a lot wrong with it. But it’s still one of the better spacey moofies I reckon. Well worth seeing in a 3D cinema.

There aren’t many movies that justify the expense of viewing on a 3D screen.