NASA say defunct satellite due to plunge to earth

thecommander · 24-09-2011 1:55pm

And the video on here is of our old friend, the Chinese lantern.

http://www.space.com/13078-nasa-uars-satellite-falls-earth.html

Popoutman · 24-09-2011 11:32pm

Captain Chaos wrote: »

We can't even see the ISS pass over when it's in the Earth's shadow.

I can, and I have. It appears as about an 8th magnitude star for up to 2 minutes after going into shadow. I've been able to follow it with a hand-guided 6" Dob and a pair of 15x70 binos.

kraggy · 26-09-2011 2:47am

I've no real concept of orbit so can I ask a few questions?

1. Why did this fall to earth and other objects in Orbit are still up there? i.e. what force keeps stuff up there as opposed to falling back down here?

2. What force moves stuff along and around the world? What propels the satellites forward?

3. What would happen to a person if they were released into orbit from a shuttle with no suit or an astronaut's suit broke open?

Thanks.

FrostyJack · 26-09-2011 3:07am

kraggy wrote: »

I've no real concept of orbit so can I ask a few questions?

1. Why did this fall to earth and other objects in Orbit are still up there? i.e. what force keeps stuff up there as opposed to falling back down here?

2. What force moves stuff along and around the world? What propels the satellites forward?

3. What would happen to a person if they were released into orbit from a shuttle with no suit or an astronaut's suit broke open?

Thanks.

1. It drifted out of orbital velocity and there wasn't enough propellant left on board to put it back into a stable orbit. NASA decided to use what fuel was left to push it to Earth quicker to stop it hitting the likes of other satellites in the future. Orbital velocity is the velocity needed to achieve balance between gravity's pull on the satellite and the inertia of the satellite's motion, this is what keeps them up in space.

2. Gravity and velocity (as stated above). This gives more detail. http://science.howstuffworks.com/satellite3.htm

3. They would die very quickly. They would be exposed to vacuum conditions, so they wouldn't be able to breath. If somehow you were able to breath you would freeze to death in short time. Without the pressure suit the body would expand as well (because there is less pressure in space), but I think this is survivable.

jumpjack · 26-09-2011 6:46am

kraggy wrote: »

I've no real concept of orbit so can I ask a few questions?

1. Why did this fall to earth and other objects in Orbit are still up there? i.e. what force keeps stuff up there as opposed to falling back down here?

The rocket which launches a satellite gives it enough speed to acquire needed centrifugal acceleration to "balance" earth gravity. Then, no more engine is required,as in the vacuum the satellite can't be slowed down by air friction.

Actually, some molecules of air are still present at the satellite altitude (300 km), and after some years travelling at 30'000 km/h, the satellite is slowed down a bit; centrifugal force then becomes lower, hence gravity attacts more, hence satellite goes down more , it encounters more air molecules, which slow down it even more, so it goes down more....
At the end, it reenters atmosphere and burns up.

2. What force moves stuff along and around the world? What propels the satellites forward?

No force is needed if no friction is present.

3. What would happen to a person if they were released into orbit from a shuttle with no suit or an astronaut's suit broke open?

Various theories around: boiling blood, body explosion, immediate freezing,...

Peanut · 26-09-2011 8:43pm

kraggy wrote: »

2. What force moves stuff along and around the world? What propels the satellites forward?

It's not at all obvious where inertial force originates from. There's an interesting page on it here,

...Inertial reaction forces are instantaneous; there's no doubt whatsoever about that. When you push on something, it pushes back on you immediately. If they're caused chiefly by the most distant matter in the universe, how can that be?

Only three answers to this question seem to be available:

* Relativity notwithstanding, the force really is propagated instantaneously. The occurrence of so-called "non-local" interactions in quantum phenomena (reported even in the popular press of late) might make such a scheme seem plausible.

* Some sort of a local field, maybe not our A field, is really the cause of inertia.

* When you push on an object a gravitational disturbance goes propagating off into either the past or the future. Out there in the past or future the disturbance makes the distant matter in the universe wiggle. The wiggling stuff out there makes up the currents that cause disturbances to propagate from the past or the future back to the object. They all arrive from the past or future just in time to produce the inertial reaction force you feel.

...the least implausible explanation of the origin of inertia is gravitational disturbances that propagate to and from the distant future out there.

http://physics.fullerton.edu/~jimw/general/inertia/index.htm

emo72 · 26-09-2011 9:30pm

peanuts reply has just totally mindfecked me ^^^^^^^^^^^

i never ever gave a moments thought to inertia. now its gonna totally play on my mind. forever.

Peanut · 26-09-2011 10:23pm

Hahah

Sorry

How about we decide that stuff just moves mmmkay? :pac:

27-09-2011 9:34pm

UARS re-entry update video

http://www.nasa.gov/multimedia/videogallery/index.html?media_id=113411791

gbee · 28-09-2011 7:45am

Jake1 wrote: »

UARS re-entry update video

http://www.nasa.gov/multimedia/videogallery/index.html?media_id=113411791

Thanks, does this mean we must officially discount all the videos?

NASA say defunct satellite due to plunge to earth

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