njxc500
Topic Author
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Uars Satellite, Reentry Hazard

Fri Sep 23, 2011 5:37 pm

For some reason the news of this satellite crashing to earth has caught my attention. They are saying they don't know when or where it's going to end up.

How would this be handled to avoid the debris from impacting commercial aircraft, since they say it will break apart into many pieces? What if it happens over a busy North Atlantic route, with only hours or minutes notice?

I know very little about reentry, but I think that once the altitude drops, the satellite will begin to slow down and fall faster, but they don't know when or where that will happen yet, but it's supposed to happen today.

Interesting.

http://www.washingtonpost.com/nation...s/2011/09/23/gIQA5VmiqK_story.html

http://www.n2yo.com/?s=21701
 
kalvado
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RE: Uars Satellite, Reentry Hazard

Fri Sep 23, 2011 8:01 pm

Chances of airliner being hit by these debris are low enough not to worry about it. Something like 1 in a million for worldwide fleet.
Chances of getting uncommanded dual engine shutdown on ETOPS route are probably on the same page, if not higher.
 
zanl188
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RE: Uars Satellite, Reentry Hazard

Fri Sep 23, 2011 8:08 pm

I'm guessing on the specs here but figure a 25 to 35 foot long satellite weighing, oh, 10 to 20 thousand pounds. Break it up into chunks at high altitude, then let the less dense pieces slow down and crash first while the denser stuff goes further downrange. The debris field will be approx. 500 miles long...

Basically they're depending on the "Big Sky" theory... But just in case I believe the FAA has issued an advisory for the effected areas.
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canoecarrier
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RE: Uars Satellite, Reentry Hazard

Fri Sep 23, 2011 9:59 pm

Quoting kalvado (Reply 1):
Chances of airliner being hit by these debris are low enough not to worry about it. Something like 1 in a million for worldwide fleet.

The chances are more likely many orders of magnitude larger than that. The chances of any one person getting hit by the debris are around 1 in 3,200. Meaning that a person would get hit, not you. If we're specifically talking about you there's a 1-in-21-trillion chance that will happen. I'd qualify this statement by saying that I bet there's a decent margin of error for that calculation based on the size of the object, the likelihood it will reenter over a populated area, and the population density of that area.

Since there's about 7 billion people on earth the chances would be much higher that any one person would be hit over the (and I'm being generous here) 1 million aircraft worldwide. I'm a hack with statistics but I'd bet the real chance of any one plane getting hit would be above 1 in 22 1/2 million.

Quoting njxc500 (Thread starter):
I know very little about reentry, but I think that once the altitude drops, the satellite will begin to slow down and fall faster, but they don't know when or where that will happen yet, but it's supposed to happen today.

Maybe, or maybe not. Earlier in the week they thought it could be as early as Wed. It's tough to estimate since a solar flare only takes 10 min to reach earth and that would inflate the earth's atmosphere, increase friction and it would re-enter earlier.

Quoting ZANL188 (Reply 2):
I'm guessing on the specs here but figure a 25 to 35 foot long satellite weighing, oh, 10 to 20 thousand pounds. Break it up into chunks at high altitude, then let the less dense pieces slow down and crash first while the denser stuff goes further downrange. The debris field will be approx. 500 miles long...

This was Mir de-orbiting. Pretty spectacular. http://www.youtube.com/watch?v=fVQd9Ejkbiw

In the meantime I'll be in my basement with my helmet on  Wink If you hear it's coming down, get outside with your camera. It will be memorable. I believe only one person has ever been hit with space debris.

http://www.zmescience.com/space/the-...orld-ever-to-get-hit-by-space-junk

Pretty safe.

[Edited 2011-09-23 15:03:09]
The beatings will continue until morale improves
 
Areopagus
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RE: Uars Satellite, Reentry Hazard

Fri Sep 23, 2011 10:09 pm

Skylab surprised the experts by sailing farther along track than predictions made as late as its last pass over the North Atlantic on its way to its expected rain-down zone over the Indian Ocean. It wasn't expected to hit Australia, but it did.
 
canoecarrier
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RE: Uars Satellite, Reentry Hazard

Fri Sep 23, 2011 10:21 pm

Quoting Areopagus (Reply 4):
Skylab surprised the experts by sailing farther along track than predictions made as late as its last pass over the North Atlantic on its way to its expected rain-down zone over the Indian Ocean. It wasn't expected to hit Australia, but it did

A little known fact about Skylab is that the Shire of Esperance issued the US a $400 AUD littering fine for debris that fell there that went unpaid for 30 years. Out of respect for our Aussie friends we should have just paid it rather than taking the whole thing as a joke.

It's likely a portion of this spaceship will be recovered if it breaks up over land.
The beatings will continue until morale improves
 
kalvado
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RE: Uars Satellite, Reentry Hazard

Sat Sep 24, 2011 1:10 am

Quoting canoecarrier (Reply 3):
. I'm a hack with statistics but I'd bet the real chance of any one plane getting hit would be above 1 in 22 1/2 million.

Unless you're in space junk insurance business, 1 in a million and 1 in 22 million are pretty much the same "not gonna happen" thing..
 
njxc500
Topic Author
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RE: Uars Satellite, Reentry Hazard

Sat Sep 24, 2011 2:03 am

NOTAM has been issued, NASA says 2 hours prior, they "may" be able to pinpoint the location within 5,000 AND Mount Cook Airlines (New Zealand)">NM.....


!FDC 1/2720 FDC .. SPECIAL NOTICE .. EFFECTIVE IMMEDIATELY UNTIL 1109252359 UTC. AIRCRAFT ARE ADVISED THAT A POTENTIAL HAZARD MAY OCCUR DUE TO REENTRY OF SATELLITE UARS INTO THE EARTH'S ATMOSPHERE. FAA IS WORKING WITH THE DEPARTMENT OF DEFENSE AND NASA TO ENSURE THE MOST CURRENT RE-ENTRY INFORMATION IS PROVIDED TO OPERATORS AS QUICKLY AS POSSIBLE. FURTHER NOTAMS WILL BE ISSUED IF SPECIFIC INFORMATION BECOMES AVAILABLE INDICATING A UNITED STATES AIRSPACE IMPACT. IN THE INTEREST OF FLIGHT SAFETY, AND Irtysh-Avia (Kazakhstan)">IT IS CRITICAL THAT ALL PILOTS/FLIGHT CREW MEMBERS REPORT ANY OBSERVED FALLING SPACE DEBRIS TO THE APPROPRIATE ATC FACILITY AND INCLUDE POSITION, ALTITUDE, TIME, AND DIRECTION OF DEBRIS OBSERVED. THE DOMESTIC EVENTS NETWORK /DEN/ TELEPHONE 202-493-5107, IS THE FAA COORDINATION FACILITY.
 
bohica
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RE: Uars Satellite, Reentry Hazard

Sat Sep 24, 2011 6:46 am

Quoting canoecarrier (Reply 5):
A little known fact about Skylab is that the Shire of Esperance issued the US a $400 AUD littering fine for debris that fell there that went unpaid for 30 years. Out of respect for our Aussie friends we should have just paid it rather than taking the whole thing as a joke.

Considering the way the US Government operates, it would cost the US taxpayer lots more than $400 to pay the fine.
 
MadameConcorde
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RE: Uars Satellite, Reentry Hazard

Sat Sep 24, 2011 7:39 am

Just came on Twitter

@NASA NASA
We can now confirm that #UARS is down! Debris fell to Earth between 11:23 p.m. EDT Friday, Sept. 23, and 1:09 a.m. EDT Sept. 24.

  


@NASA NASA
#UARS Update: Satellite confirmed to have penetrated the atmosphere over the Pacific Ocean. Precise time & location not yet known.

[Edited 2011-09-24 01:07:48]
There was a better way to fly it was called Concorde
 
Stealthz
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RE: Uars Satellite, Reentry Hazard

Fri Sep 30, 2011 12:24 am

Does NASA march to the beat of a different "Navigation" drummer??

I noticed this report of the UARS satellite re entry--

Quote:
The Joint Space Operations Center at Vandenberg Air Force Base in California has determined the satellite entered the atmosphere over the Pacific Ocean at 14.1 degrees south latitude and 189.8 degrees east longitude (170.2 west longitude)

Since when did the planet have an 189.8 degrees east longitude??
If your camera sends text messages, that could explain why your photos are rubbish!
 
rolfen
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RE: Uars Satellite, Reentry Hazard

Fri Nov 04, 2011 1:49 am

So a satellite is gonna crash somewhere on Earth, and they're like "don't worry, it'll probably fall on someone else's head"?
And it's not the first time... am I the only smelling something wrong here?
rolf
 
kalvado
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RE: Uars Satellite, Reentry Hazard

Fri Nov 04, 2011 2:27 am

Quoting rolfen (Reply 11):
And it's not the first time... am I the only smelling something wrong here?

Hopefully nothing real bad on board - no huge amount of nuclear material mostly; any chemistry will burn on reentry.
Then it's just a chunk of metal falling in random spot. Pretty much on a same page as having a crashed plane fall on someones head, or meteorite crashing through the roof.
There are much better things to worry about.
 
rolfen
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RE: Uars Satellite, Reentry Hazard

Fri Nov 04, 2011 2:25 pm

Quoting kalvado (Reply 12):
There are much better things to worry about.

I'm really more worried about the principle of endangering lives in the name of science, accepting such risk and imposing it to people who did not have any say in it, in the name of science.
For me, science, no matter how advanced and important, does not justify endangering the life of one person, unless that person has voluntarily and willingly accepted that, which is obviously not the case.

I'm just under the impression that this was a risk that was knowingly taken when they designed and launched the satellite. The articles do not make it look at all like this unpredictability was an accident. It very much looks like they knew all along that the satellite was going to come back and crash "somewhere", yet it was launched, and this attitude is even starting to look like a trend, or the norm in space programs. That is the major difference between this case, and the case of a meteorite or an airplane, where it would be totally an accident, something that was either not supposed to happen at all, or over which there was no control since it's an act of nature, in the case of the meteorite.

What is happening to this satellite reminds me of the scandal that happened with a big auto manufacturer in the US, in the 60ies or 70ies, when they willingly decided not to recall cars with an ill-designed and dangerous fuel tank, because it was deemed that it would be cheaper to pay compensation to the victims than recall and fix the cars. It's a well known story but I unfortunately forgot much of the details.

Such an attitude is simply unacceptable. One could even argue that it's criminal. Now in this particular case, I know that the facts are much more blurry, the line is much thinner, and many things are debatable. Yet I see enough things to solidly suspect that something is, at least going in the wrong direction (figuratively speaking), which is why I spoke about "something smelling wrong".

Surely, there are more important things to worry about than being struck by a satellite part when odds are 1 in a billion (or something), but the possibility of people from this level getting away with knowingly endangering the life of random persons across the globe is, I think, a very valid thing to worry about, or, at least, to consider.

Quoting Areopagus (Reply 4):

Skylab surprised the experts by sailing farther along track than predictions made as late as its last pass over the North Atlantic on its way to its expected rain-down zone over the Indian Ocean. It wasn't expected to hit Australia, but it did.

If the Uars satellite was also expected to end up somewhere in the ocean, then I stand corrected. I still have a nagging feeling about this, I feel like this whole thing is treated a bit too casually. But I'm really glad to read such information. Thanks.

[Edited 2011-11-04 07:37:33]
rolf
 
kalvado
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RE: Uars Satellite, Reentry Hazard

Fri Nov 04, 2011 4:13 pm

Quoting rolfen (Reply 13):

I'm really more worried about the principle of endangering lives in the name of science, accepting such risk and imposing it to people who did not have any say in it, in the name of science.
For me, science, no matter how advanced and important, does not justify endangering the life of one person, unless that person has voluntarily and willingly accepted that, which is obviously not the case.

In most cases, satellites should be either moved to a parking orbit or controllably re-enter atmosphere to go down in southern Pacific. Such uncontrolled re-entries are result of on-board failure and loss of control.

As for the risk.. Do you accept the risk of a 747 falling on your roof after an on-board fire... all in the name of people getting their fresh dose of iCrap on time? That's much more risk for not so good reason.
 
MadameConcorde
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RE: Uars Satellite, Reentry Hazard

Fri Dec 16, 2011 8:18 pm

Now it will be Phobos-Grunt's turn to fall back to Earth. The satellite lost it and cannot go to Mars.

Russia's Mars Probe Will Crash to Earth in January

The agency said the unmanned Phobos-Ground spacecraft will plummet to Earth between Jan. 6 and Jan. 19, and the rough area of where the fragments could fall could only be calculated a few days ahead of its plunge.

As of now, it said only that the probe's fragments could rain down anywhere along a broad swath between 51.4 degrees north to 51.4 degrees south, which would include most of land surface.

http://abcnews.go.com/Technology/wir...arth-january-15168930#.Tuul8Vb-WAh

Not good!

 
There was a better way to fly it was called Concorde
 
jollo
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RE: Uars Satellite, Reentry Hazard

Sat Dec 17, 2011 8:33 pm

Quoting kalvado (Reply 14):
In most cases, satellites should be either moved to a parking orbit or controllably re-enter atmosphere to go down in southern Pacific. Such uncontrolled re-entries are result of on-board failure and loss of control.

Well, you're right, *should* is the right verb. ESA, for example, adheres to (AFAIK, self imposed) orbital junk limitation guidelines; NASA *should* as well, but not always has. UARS, for example, was decommissioned back in 2005, no maneuvering fuel left: no failure at all, it was well known that its reentry would be uncontrolled and only loosely predictable.

The reason is economic: safe decommissioning "costs" either in terms of less scientific payload, or of shorter operational life. Of course, choosing to forgo these costs only dumps them on someone else (as in someone having his roof smashed by debris), or on the future (in 2010 ISS itself had to maneuver clear of UARS).

Phobos-grunt is another story, of course: its uncontrolled reentry (alas, with a full load of hazardous chemicals and some reentry-capable components) will be the result of an accident.
 
kalvado
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RE: Uars Satellite, Reentry Hazard

Sat Dec 17, 2011 10:36 pm

Quoting jollo (Reply 16):
UARS, for example, was decommissioned back in 2005, no maneuvering fuel left: no failure at all, it was well known that its reentry would be uncontrolled and only loosely predictable.

Everything is not that simple.
http://www.usatoday.com/tech/science...ded-satellite-retrieval/50529710/1

Quote:
"UARS was originally conceived to be retrieved by the shuttle at the end of its mission. Due to changes in the shuttle program this was no longer an option," five NASA and contractor engineers from Goddard Space Flight Center in Greenbelt, Md., said in a UARS end-of-mission case study presented to the American Institute of Aeronautics and Astronautics in 2008.

So uncontrolled re-enry was not part of a plan as well. If shuttle problems would be predictable at the time of decommissioning, UARS would be left on higher orbit, so our grandchildren could deal with that in efficient way.
 
prebennorholm
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RE: Uars Satellite, Reentry Hazard

Sun Dec 18, 2011 4:00 am

Quoting rolfen (Reply 13):
I'm really more worried about the principle of endangering lives in the name of science, accepting such risk and imposing it to people who did not have any say in it, in the name of science.
For me, science, no matter how advanced and important, does not justify endangering the life of one person, unless that person has voluntarily and willingly accepted that, which is obviously not the case.

I see your worries. But our society doesn't work that way. It is based on accepting certain levels of risk exposed to totally innocent people. Otherwise a lot of things would never be permitted, certainly not flight. Same with cars, trains, and a lot of factories.

Talking about satellites falling uncontrolled to the ground, then it is a much smaller risk than the constant bombardment of our planet with meteors. We can do nothing about that.

That's not entirely true. Because we master space flight, then we have the technology to avoid the really big catastrophes. Examples:

A comet of some size may one day be heading to collision with Earth. It has the potential to instantly kill millions, and in addition pollute the atmosphere in such a way that it either triggers a world wide ice age or a runaway greenhouse effect, and that way destroying our whole culture. Due to space flight we have the technology to discover that risk years in advance, fly a nuclear bomb into the center of the comet and blow it apart.

Also an asteroid of some size may be heading for Earth, able to destroy a mega-city completely into a crater. That would be bad enough, but it might be much worse if it hit the middle of the Pacific Ocean since tsunamis as never seen before might destroy all coastal regions. Due to space flight we can land a rocket engine on it, and let it change its course a tiny fraction of a degree, but enough to make it miss collision with Earth.

The same way a helicopter may save the lives of people on a sinking ship one day, and it may crash on your head the next day. Life can never be total risk avoidance. It has to be clever risk management.

This thread is about the risk that debris hits one of 10-20,000 airliners. But what fragments make it without evaporating down to 30,000 feet, will also make it to the ground. Consequently the risk of hitting some of seven billion people on the ground is many thousand times worse.
Always keep your number of landings equal to your number of take-offs
 
jollo
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RE: Uars Satellite, Reentry Hazard

Sun Dec 18, 2011 9:34 pm

Quoting kalvado (Reply 17):
Everything is not that simple.

I am afraid that it *is* indeed that simple.

Retrieval by the Space Shuttle was, simply put, the most expensive controlled reentry method ever devised, and was used *only once* to land a scientific payload (LDEF, STS-32, 1990). Only 2 other comm sats, intended to be refurbished and relaunched, were ever retrieved (by a single mission, STS-51-A, 1983), but in that case the economics were justified by the reuse of the payload (at least officially: you can draw your own conclusions from the fact that the method was never used again) . I know there also has been SPAS-I, but it was a demo sat for RMS validation, released and retrieved within the same mission (STS-7, 1983), and the presence of a token scientific payload aboard was incidental.

UARS was indeed intended to be retrieved by the Shuttle when it was designed back in the early eighties, when Shuttle launches were thought to become bi-monthly routine and costs to drop accordingly: the thinking was that a mission with a compatible orbit and an empty cargo hold would come up for sure, and the retrieval would have been virtually "for free" (just rendez-vous and EVA costs).

Alas, that launch frequency never materialized. The last time anyone mentioned UARS retrieval was in 2001, but after the Columbia disaster (2003) everybody knew it just never would happen. UARS last burn was done to lower its orbit, on its way to uncontrolled reentry and rendering de facto impossible an intercept by any Shuttle flight.

So uncontrolled re-entry was *the* plan at the time of decommissioning: not an accident at all. BTW, the article you link doesn't say otherwise.
 
jollo
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RE: Uars Satellite, Reentry Hazard

Mon Dec 19, 2011 12:59 pm

To be fair: letting UARS burn in the atmosphere was indeed an "orbital debris limitation" measure. Moreover, as of 2005, I doubt any other options where left: a burn up to a "graveyard" orbit would have been impossible (not planned for to begin with), and the best they could manage with the scant fuel remaining was an orbit-lowering maneuver (that did take another 6 years before actual re-entry).

NASA however is, in my opinion, "guilty" on two counts: 1) relying by design on a safe reentry method (Shuttle retrieval) based on both futuristic and optimistic assumptions and 2) once the feasibility of the original plan was in doubt (that is, before launch: the Challenger disaster had already occurred 5 years earlier), not re-planning for a controlled destructive re-entry, at the cost of limiting service life (or at least giving up some mission extensions).
 
kalvado
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Joined: Wed Mar 01, 2006 4:29 am

RE: Uars Satellite, Reentry Hazard

Mon Dec 19, 2011 3:41 pm

Quoting jollo (Reply 20):


NASA however is, in my opinion, "guilty" on two counts: 1) relying by design on a safe reentry method (Shuttle retrieval) based on both futuristic and optimistic assumptions and 2) once the feasibility of the original plan was in doubt (that is, before launch: the Challenger disaster had already occurred 5 years earlier), not re-planning for a controlled destructive re-entry, at the cost of limiting service life (or at least giving up some mission extensions).

Well, it is not clear to me if as-launched satellite had enough fuel for controlled de-orbit from a high orbit. After orbit-lowering burn, probably another 100-120 m/s (3-4% of satellite weight worth of fuel) would be needed for controlled re-entry, and that is a lot of fuel. I doubt UARS needed a lot of orbit corrections for the primary mission, so rejecting program extensions would not save too much for re-entry.
Fuel reserves should be determined during design stage, quite likely at the very beginning of Shuttle era, so by launch date options were to hope for the best or to re-design ($$$$$) and brake shuttle launch schedule. Compare with Hubble telescope, which was planned for launch in 1983 - ands actually launched a year before UARS. You have to design these things knowing quite well that it would be 5-10 years until launch, and another 10-20 years of operation.
Unlike communication satellites, where worn out electronic is a low-value scrap material, scientific instruments are more than likely one of a kind, and would be happily re-used - so return to earth was more or less meaningful.
Hindsight is always 20/20 - I doubt that at the time decisions were taken anyone thought "and I don't care where this damn thing would fall". It just that things did not work as planned.
And if you want to think ahead, there is another big scientific satellite from the same era without clear plan for end of the mission - Hubble telescope.
 
jollo
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RE: Uars Satellite, Reentry Hazard

Mon Dec 19, 2011 4:37 pm

Quoting kalvado (Reply 21):
Hindsight is always 20/20 -

   I agree, too easy to criticize decisions made 20 years ago, knowing how things actually played out...

Quoting kalvado (Reply 21):
I doubt that at the time decisions were taken anyone thought "and I don't care where this damn thing would fall".

I am sure, and I never intended to imply a negligent attitude. More of a "let's hope for the best" attitude, and there's no way to completely do away with that. Still, learning from past ... er... "less than optimal results" is the only way to get better eventually, and UARS wasn't the best planned end-of-mission ever (if anything, from a PR point of view).

Quoting kalvado (Reply 21):
And if you want to think ahead, there is another big scientific satellite from the same era without clear plan for end of the mission - Hubble telescope.

Swell! Let's do it! We've got a few years to keep ideas coming, and a robotic deorbit package (made possibile by SM4/STS-125) would be a *really* ground-breaking achievement.

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