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Why Shoot Down a Satellite? Analyzing an Analysis
A reader, name withheld by request, writes "Writing in the IEEE Spectrum, James Oberg analyzes whether there was, in fact a significant risk to humans from the satellite which the US military shot down on 21 February, purportedly 'to head off the possibility of its splashing a half ton of toxic hydrazine fuel somewhere on Earth.' Previous experts had 'scoffed' at the rationale put forth, pointing out that there was trivial possibility that any significant amount of toxic fuel would make it to the ground intact. Oberg's analysis, titled 'the inside story,' purports to debunk this, and claims that indeed it's possible, and even likely, that there could be a danger to the ground. Unfortunately, the analysis is full of flaws and lack of rigor — indeed, lacking any sort of numerical reasoning. It seems to be too much repeating official 'spin,' and could have used a hefty dose of skepticism — and could also use a little bit of actual analysis using numbers, rather than handwaving." Read on for the rest of an interesting analysis of a topic that suddenly seems more complex.
The submitter continues:
"Here's the first number that Oberg should have quoted: 32 Megajoules per kilogram. That's orbital energy, which is how much energy has to be removed by ablation or otherwise dissipated for the hydrazine tank to enter the atmosphere and hit the ground undamaged. For reference, TNT holds about 4.6 MJ/kg.
Oberg quotes 'Hydrazine requires a tremendous amount of energy to go from solid to liquid.' This energy is known as the heat of fusion, and for hydrazine it is just a little under 400 kJ/kg. That's about 1% of the energy released by entry heating. Hardly a 'tremendous' amount of energy, compared to the entry energy that's nearly a hundred times greater.
Oberg goes on to quote 'There is a widespread notion that meteorites falling to Earth arrive red hot.' He is correct here. In fact, meteorites falling through the atmosphere typically explode, shattering into dozens or hundreds of pieces; something that occurs at the point when the dynamic pressure on the leading face exceeds the yield stress of the material. This occurs for meteoroids of all compositions, including nickle-iron meteorites that are far more robust than hydrazine tanks. If the atmospheric entry of meteorites is relevant, it hardly bolsters the case that a tank will enter intact (and if it's not relevent, why did Oberg bring it up?)
Furthermore, if you look at a typical nickle-iron meteorite, you'll see a surface pitted and mottled with holes ranging from the size of golf balls up to pits the size of baseballs. These are known as regmaglypts; they are the areas ablated away by the entry plasma. Even a single such ablation pit would, of course, destroy a hydrazine tank.
The second number Oberg should have quoted is a number called ballistic coefficient, the mass divided by the area of the tank. Basically, the smaller the ballistic coefficient, the less stressful the entry will be. Unfortunately, a full hydrazine tank has a very high ballistic coefficient. It is an empty tank, not a full one, that is likely to enter intact. Talking about empty film canisters, or even empty fuel tanks, making it intact through atmospheric entry is really about as relevant as talking about dropping a piece of paper on the floor.
The article contains a quote from Andrew Higgins, with a link to (purportedly) the research done that contains the quote. Unfortunately the link does not actually contain the quote used in the article; in fact, it seems to be mostly a discussion of a side issue. Let me emphasize this: Higgins did not say what he is quoted as saying in the place he was reported as saying it. This may merely be sloppy journalism — maybe he said it somewhere else — but I am again left with the question: if I can't even trust the simplest things he says that can be easily checked, why should I trust anything else?
In short, Oberg's article is poorly thought out, avoids even simple back-of-the-envelope calculations, and accepts uncritically information that should have been aggressively questioned. He concludes that a well-defined and thoroughly researched technological hazard assessment — of a kind that someday, for better or worse, will be needed again — has wound up buried in obscurity and obfuscation. This may be true, but no well defined nor thoroughly researched technological hazard assessment was anywhere in evidence. The analysis he gives in the article is buried in obscurity and obfuscation.
(apologies for posting as Anonymous Coward. I work in the field.)"
Oberg goes on to quote 'There is a widespread notion that meteorites falling to Earth arrive red hot.' He is correct here. In fact, meteorites falling through the atmosphere typically explode, shattering into dozens or hundreds of pieces; something that occurs at the point when the dynamic pressure on the leading face exceeds the yield stress of the material. This occurs for meteoroids of all compositions, including nickle-iron meteorites that are far more robust than hydrazine tanks. If the atmospheric entry of meteorites is relevant, it hardly bolsters the case that a tank will enter intact (and if it's not relevent, why did Oberg bring it up?)
Furthermore, if you look at a typical nickle-iron meteorite, you'll see a surface pitted and mottled with holes ranging from the size of golf balls up to pits the size of baseballs. These are known as regmaglypts; they are the areas ablated away by the entry plasma. Even a single such ablation pit would, of course, destroy a hydrazine tank.
The second number Oberg should have quoted is a number called ballistic coefficient, the mass divided by the area of the tank. Basically, the smaller the ballistic coefficient, the less stressful the entry will be. Unfortunately, a full hydrazine tank has a very high ballistic coefficient. It is an empty tank, not a full one, that is likely to enter intact. Talking about empty film canisters, or even empty fuel tanks, making it intact through atmospheric entry is really about as relevant as talking about dropping a piece of paper on the floor.
The article contains a quote from Andrew Higgins, with a link to (purportedly) the research done that contains the quote. Unfortunately the link does not actually contain the quote used in the article; in fact, it seems to be mostly a discussion of a side issue. Let me emphasize this: Higgins did not say what he is quoted as saying in the place he was reported as saying it. This may merely be sloppy journalism — maybe he said it somewhere else — but I am again left with the question: if I can't even trust the simplest things he says that can be easily checked, why should I trust anything else?
In short, Oberg's article is poorly thought out, avoids even simple back-of-the-envelope calculations, and accepts uncritically information that should have been aggressively questioned. He concludes that a well-defined and thoroughly researched technological hazard assessment — of a kind that someday, for better or worse, will be needed again — has wound up buried in obscurity and obfuscation. This may be true, but no well defined nor thoroughly researched technological hazard assessment was anywhere in evidence. The analysis he gives in the article is buried in obscurity and obfuscation.
(apologies for posting as Anonymous Coward. I work in the field.)"
To test our new weapons and show the Chinese how we roll.
The US shot down its satellite as a response to China shooting down their satellite making a region of space pretty darn dangerous.
It's just a cold war pissing contest. Trying to look for scientific explanations or a semblance of logic is futile.
No story here.
The submitter is debunking an article written in IEEE Spectrum, a civilian magazine. To debunk an article written by a non-expert says very little about whether a shoot-down was actually warranted.
Nice try on the anonymity, but there's your name on the Related Stories list with the original Firehose posting...
Some US General wanted to see if the word 'IMPRESSIVE' would be emblazoned across the sky when they hit it.
A learning experience is one of those things that say, 'You know that thing you just did? Don't do that.' - D. Adams
What was the risk of shooting it down? It seems close to "none." The missile used would surely have a mechanism to self-destruct in the event of a miss, and even if it didn't, I don't see how its falling could be any more dangerous than the hydrazine. Plus, it was probably a useful training exercise, should they ever need to shoot down a "really" dangerous satellite.
Of course, since it was done months ago, it's all hypothetical anyway.
Comment of the year
The reason we shot it down was because China had just shot down one of theirs in a weapons demonstration. China was using it as propaganda about how great they were. So we chopped them down a notch by showing them that we can do it as well. And not only that, we can do it from a mobile platform (i.e. a cruiser at sea), not just from a land based stationary platform. This was simply an international pissing match. Nothing more, nothing less.
We were all warned a long time ago that MS products sucked, remember the Magic 8 Ball said, "Outlook not so good"
Why are they making this out to be so hard to work out?
It's not like it's rocket science.... ....oh, wait...
If the satellite was left in the sky, it might still be around when the democrats get into office. That would be hard evidence of all the (domestic) spying that went on. A low-flying satellite would be able to provide some hi-res pics. I don't know much about orbits, but maybe it was an opportune time, and they weren't sure if they'd get another shot later. It also allowed us to flex some military might. There certainly isn't a constructive case for shooting it down.
[1] choose your conspiracy, there are plenty to go around - you're probably closer to the truth than this article, but you already knew that.
politicians are like babies' nappies: they should both be changed regularly and for the same reasons
the amount of hydrazine in there would have made a good substitute for a little suitcase neutron bomb. say, a half square mile or so.
no, Uncle just didn't want his special chips on eBay.
if this is supposed to be a new economy, how come they still want my old fashioned money?
Maybe I'm getting cynical in my old age, but I saw the whole thing as an excuse to demonstrate our capabilities.
If brevity is the soul of wit, then how does one explain Twitter?
From the link about why the satellite was no threat:
"The hydrazine tank is a 1-meter sphere containing about 400 liters of hydrazine. The stated hazard area is about 2 hectares, something like 1/10,000,000,000 of the area under the orbit," he adds. The potential for actual harm in unbelievably small. Which means the hydrazine rationale just doesn't hold up, literally not within orders of magnitude."
That's it for any analysis - the rest of the article was devoted to analyzing the political and military reasons why the explanation was bogus. And most of the analysis seemed to be delivered with substantial chips of the speakers shoulders. As for the numbers, while they may be *statistically* insignificant, that is pretty irrelevant next to the political consequences to a military that says "Yeah, we could have shot it down, but the odds were so small it wasn't worth the money. Our bad."
Then the "analysis" with the post - sounds good, until you get to the end: "Posted anonymously". Sorry, but that's a fail right there. He could be a 13year old in his Mom's basement, or Feynman blogging from the grave, but without attribution I just can't take it seriously.
"As God is my witness, I thought turkeys could fly." A. Carlson
I think they shot it down because they decided it was a good idea. What's the problem? The US is going to get criticized by someone for any choice it could possibly make, including doing nothing. This was probably the choice with the least uncertainty.
Goddamn it, it's spelled NICKEL. It's not hard you nerds.
Brand new, state of the art spy satellite stops working. Are you going to risk parts of it falling and being salvageable, or are you going to blow it up?
Oberg had an earlier analysis (March 2008) on the same topic in The Space Review that covers many of the same points with a little more detail than this article.
http://www.thespacereview.com/article/1073/1
Thank you for debunking the debunking of the debunking.
The opinions stated herein do not necessarily represent those of anybody at all. Deal with it.
Actually, if there's a conspiracy, its this whole business of hydrazine being supposedly unsafe. Since I've been using hydrazine scalp cream, I've regained a full head of hair and my private assets have significantly increased in size. It's only because George Bush wants everyone to go bald, that the satellite was shot down.
This is my sig.
So how about we cross the streams and seal the deal?
Is this on /. because it involves satelites, or because, the analysis is full of flaws and lack of rigor ... lacking any sort of numerical reasoning? Perhaps I should read TFA... :-)
It must have been something you assimilated. . . .
...money. Cheaper to shoot it down than to try anything else to intercept. This may include protecting sensitive intelligence-related equipment, in that a molten ball of slag is less damaging than a free-fallen transmitter in the wrong hands.
"It does not do to leave a live dragon out of your calculations, if you live near him." - J. R. R. Tolkien
Because its f'ing awesome! duh
Most 8 year olds I know are good at making up a pretext for getting what they want.
A: I really wanna shoot down a satellite!
B: You can't do that, it'll make you look like a violent war provocateur.
A: But! But! But! What if it was a dangerous satellite. Like it was going to kill everyone or something. And we had to shoot it down to save everyone! And it had racing stripes and a turret on top and played the A-Team theme song!
B: Well.... Okay, but only if it's a dangerous satellite.
A: Yay! Mom! Dad says we can shoot down a satellite!
C'mon... wouldn't you have wanted to blow it up if you had access to a missile?
That may be partially true, but the Chinese shot was way more difficult (albeit messy) than ours. We, of course, had no reason to get nearly as fancy as the Chinese did when they took theirs out and it would have been silly to even try (unless we just had a fancy satellite-killer that we just wanted to try). But, to the eyes of most of the world, I'd imagine you're right. They showed that they could do it, so we did too. Despite the fact that they were radically different shots and circumstances.
He's getting rather old, but he's a good mouse.
That would be bad.
Now before I get modded down, I be to remind whoever might read this that what I am saying is FACT. - bogaboga
Wasting taxpayer money, Fanning ego, puffing out nationalist chest, and generally being seen as barbarians had nothing to do with it?
- Minutus cantorum, minutus balorum, minutus carborata descendum pantorum.
If such a paper cannot tell why a shootdown was warranted, why waste time writing and printing it?
http://www.sff.net/people/geoffrey.landis/
http://mit.edu/aeroastro/www/people/landis/landis.html
You're at the Massachusetts Institute for Technology and can not practice simple internet privacy.
elle oh elle to you, good sir.
Why shoot down a satellite? Because
1. it's fun
2. we can
3. it makes a great firework
4. the US has not engineered sharks with lasers to blow up the satellite
5. it makes a great target for a missile test
He or she cites the figure of 32 MJ/ kg that must be dissipated, compares to the latent heat of fusion of hydrazine and assumes that this disparity means that the object could not have survived reetry. However, this assumption fails to account for the fact that most of the dissipated energy is absorbed by the ATMOSPHERE, not by the spacecraft.
See for instance, wikipedia:
"Since most of the hot gases are no longer in direct contact with the vehicle, the heat energy would stay in the shocked gas and simply move around the vehicle to later dissipate into the atmosphere."
1) It was nuclear powered. This could never be made public for obvious reasons.
Demonstrating weapons capability was secondary, we've been able to disable and destroy satellites for decades. Most impressively with lasers (not used in this case). The nations that need to know this already did.
Hydrazine was a cover story. Just like pegging Ivins with the anthrax stuff.
"Why sit down on a silly hot seat in AZ? Gay anal lanes".
/.
Ahhh, the joys of being at work on a typically slow Monday with no bosses in the office to catch you reading
She's built like a steak house, but she handles like a bistro....
I think it was for the same sort of reason that Bush announced the plans to go to Mars when China said they were doing manned Moon missions, even though the US has ignored that kind of thing for decades.
Aside from anything else, a Moon base would be the best place to launch a Mars bound rocket from.
A learning experience is one of those things that say, 'You know that thing you just did? Don't do that.' - D. Adams
I always think it would be better to keep it up there for spare parts when the space station is completed, seeing as the materials are already up there, anyone need a satelitte dish???
The weapons show off/play may be true. The "we" word sucks big time. There is only individuals and when they give up their responsiblity for an abstract "idea" - be it religion, country, political/ethnic association, they become victims for manipulation.
That's one symptom of total blindness to what is really going on causing great suffering. I love the "we had to defend our country in Vietnam"..... sure, follow the money, but that's a secret.
How bad?
http://www.chomsky.info/talks/20011103.htm
Why does everything the US is involved with have to be some kind of conspiracy? This was a good chance to test our technology and eliminate the possiblity of hazardous substances as well as large chunks of matter from hitting the ground. Why is this still an issue?
Please, no talk of shooting down satellites this week. I'd hate to have to switch back to cable to watch the rest of the Olympics!
I need trepanation like I need a hole in the head.
There are plenty of good reasons to question the timing and urgency of the U.S. decision to destroy US 193, but the last thing they needed to do was prove to China they could shoot down a satellite. Both the U.S. and Russia proved this capability many times over until they were satisfied they had it down back in the Cold War with the U.S. even shooting down a satellite with an F-15 in 1985 [http://www.spacedebate.org/evidence/1245/] (arguably a way cooler stunt than the sea-based shot).
The U.S. probably felt compelled to shoot it down because of its legal obligations under international space law to deal with potentially hazardous satellites (albeit a diminished risk and maybe not as urgent as they claimed). Its also very likely they were concerned that an intact satellite re-entering in an unfriendly region could compromise intelligence sources and methods. However, its not likely that they were doing this as a demonstration / warning shot to China or to test out new technology. They already have better methods for taking out a satellite if they wanted to and this shot was a one-time hack [http://www.spacedebate.org/evidence/3269].
I just love how someone can say "I work in the industry!", post as an AC, toss out a couple of buzzwords with no math to speak of, and scream "we're being lied to!". As the submitter of this story so clearly put it when posting his own "analysis":
Translation: "There is a conspiracy here! Trust no one! We're all being lied to!" If there's one thing I've learned over the years, there is nothing the government can say or do to convince someone who thinks like this.
Personally, I have little doubt that the satellite was shot down for exactly the official reason. We've had plenty of space junk hit the ground in recent years; as I remember, people were specifically warned not to handle debris from the space shuttle Columbia, because of concerns of hydrazine contamination. Clearly the shuttle's high ballistic coefficient didn't prevent that, did it? The hydrazine tank didn't have to reach the ground intact to cause concerns. And just imagine the headlines if nothing had been done, and debris from that spy satellite had eventually reached the ground. Russia still gets flack about the nuclear reactor debris that landed in Canada after the re-entry of COSMOS 954, and that was 30 years ago!
Of course, it was obviously an added bonus that the shoot-down was a nice demo of the military's capabilities. But if the U.S. military really wanted to test its ASAT technology, it would hardly need to hold a press conference beforehand, or issue a press release to China or Russia to inform them afterwards! China and Russia track our satellites the same as we do theirs. If one of our dead satellites conveniently "exploded", they would get the message quite clearly.
I tend to agree but would also add (speculatively of course) that the satellite was carrying highly sensitive equipment that couldn't be risked being discovered. Protecting people was a convenient excuse.
I don't see how you can claim that the Chinese shot was more difficult since the shot that the Chinese made was at a target at a greater distance, and a slower velocity. Also the point of the matter is that the United States used a mobile platform to launch. To me this would be a test to prove that we could shoot down an ICBM in route to a destination at a low orbit. Correct me if I am wrong but it seems to me that the farther the distance you have and the slower the velocity of the projectile, there is greater chance of correcting your trajectory.
It was a great test of hitting a target coming out of orbit.
Even the White House didn't play it as if it was highly necessary, but that there is a chance and they wanted to take the shot.
So, it was a good test of tracking and hitting an unstable satellite, even if it wasted a few million.
Those missiles don't last forever, so it's not like saving them for the 'Great War' really helps us out.
I thought it was mildly impressive the Bush administration said it was going to do something, and actually accomplished it, trivial or not.
Sure, maybe it was a little wag the dog, but it's was just one missile, they could not rule it out as a threat, it was a chance to try a real live falling satellite hit, and it worked flawlessly.
It's really not worth complaining about when Bush leaves you with so many other important topics that we should all be repeating in the we need accountability part of our brains.
Torture, spying, fake war, government and media working together under the guise of free press, likely election fraud, real estate and banking fraud,
Those are all ACTUAL crimes committed by the roaming forces of wealth pulling the strings from the democrats to the GOP to the media, which they own.
Send another one up and see if it happens again.
Donte Alistair Anderson Roberts - hi son!
Karma: Chameleon
Shooting down objects in high orbit requires a 2-stage attack - They're too difficult to hit directly in spite of your greater correction time. First, a carrier rocket is sent up to get as close as practical to the target. It then launches a kill-vehicle that will track and destroy the satellite.
The US did not require that much sophistication. Since the satellite was on its way down, the attack was more akin to shooting down an ICBM when its location and velocity are both known well in advance.
1) the amount of hydrazine fuel contained was infinitesimal compared to the amount of hydrazine that spills on humans every year. The F-16 uses hydrazine in its EPU, and you can trivially find stories of people practically bathing in it as a result of EPU problems and fuel dumps. The effects are generally less than the horrific outcomes presented in the stories surrounding the shoot-down. The idea that the hydrazine presented any sort of real risk is absolutely bogus, something the articles dance around and just won't address directly.
2) the chance of the debris coming down in a populated area is very close to zero. Although underreported (see http://imca.repetti.net/metinfo/metstruck.html), there are no recorded instances of anyone being killed by anything falling from space. Now of course a 1000 lb fuel tank is much deadlier than a small stone, but 1000 lb objects have fallen from space before, and we didn't bother shooting them down (http://www.space.com/news/spacehistory/dangerous_reentries_000602.html).
3) last time I checked, when heat shields fail the aluminum structure generally fails almost immediately thereafter (http://www.columbiassacrifice.com/$A_reentry.htm). I am not aware of any unprotected structure reaching the ground intact (although that could be ignorance) but I am very much aware of many unprotected structures breaking into small parts under the same conditions. This includes tanks with frozen volatiles inside. The only really large pieces of debris to reach the ground were the insulated tanks from Skylab.
4) A nuclear reactor is MUCH more robust than this fuel tank, yet when Cosmos 954 fell to Earth it's 50 by 35 cm reactor shattered and spewed its contents over 600 km (http://gsc.nrcan.gc.ca/gamma/ml_e.php). Yes, the shaping is critical in terms of shock generation and aerodynamic loading, and it's definitely easier for a sphere to re-enter than a cylinder, but still... bologna.
5) the article Oberg's is based on claims ~8 gee loading. Again, bologna; that's what you get on a carefully controlled re-entry, uncontrolled will cause much greater loadings (again, http://www.columbiassacrifice.com/$A_reentry.htm)
6) The article links to several others that are essentially dismissive of the "publicity" cover-story angle as a conspiracy theory. However, we're talking about an administration who's history shows a well-recorded "shoot first" policy based on extremely inflated data. This case fits the pattern to a T, and I see no reason to believe it differs in any way.
I call BS. Sorry James, but the argument remains specious in my books.
Maury
Or, it's probably a combination of factors, and not just a dick-measuring competition.
Consider the following:
1. A very expensive intelligence satellite is stranded in low orbit, useless. Said satellite contains expensive, highly-classefied equipment; there's a finite chance that some of this equipment might reach the surface relatively intact (see Skylab, Columbia). Obviously, certain groups (China and Russia, especially) would love to get hold of anything that survived and analyze it. It would be nice to ensure that this equipment is rendered unusable and worthless.
2. The hydrazine tank mentioned. Yes, I know the odds of it hitting anything were very, very small... but not zero. And the public outcry had it hurt or killed anyone would have been loud and swift. The decision-makers probably figured it would be better to face the inevitable international grumbling by shooting down the satellite than to face the very small (but potentially devastating) risk of impact in a populated area.
3. The Navy ABM system is going operational, and someone realizes it has the capability to shoot down low satellites. Someone probably figured "hell, we have this satellite problem; it's going to reenter soon anyways so it's a nice convenient test target. We might as well try it while we have the chance". Besides, the additional cost is a drop in the proverbial bucket.
4. At the top levels, there probably was a bit of "let's show them" going on. But I suspect it was as much a coincidence as anything else, with #1 above leading the "rational" reasons list. The hydrazine tank story just made for the best PR.
The meek may inherit the earth, but the strong shall take the stars.
Dr. Landis implies that Andrew Higgins didn't say the quoted item.
In fact, it's easily found in the link given.
In the linked text, Higgins gives a hyperlink back to a previous letter which was in The Space Review which contains that very quote and in the context Oberg said.
Landis snipes at Oberg for poor journalism, but apparently can't follow a bloody hyperlink. Why, even Cowboy Neal could do that and on a bad day to boot.
Secondly, Landis is an expert in solar cells and solid state devices. He apparently also works on elements of spacecraft electrical power systems, lander design and operation and writes articles on a variety of subjects. Impressive, but not directly in the area.
On the other hand, Andrew Higgins is a principle investigator and an expert in the behavior of materials under extreme hypersonic conditions and computer simulation of the same. His work on materials and combustion in hypersonic ram accelerators leaves him very well equipped to comment on the dynamics of reentry and the behavior of spacecraft materials and fuels under such extreme conditions.
Landis seems to be using the very sloppy and misleading tactics that he accuses Oberg of. Pot. Kettle. Black.
(Mild disclaimer. Andy Higgins is a friend going back to undergrad days (and believe me, it's been a while). I was mildly nettled that Landis invokes the name of an old friend and then becomes selectively blind when Andy gave the link to the very quoted item in the letter that Landis read.)
The headline in my rss tab was "Why Shoot Down a Satellite? Analyzing an Anal...".
This story is not what I expected to see.
Oh well, at least it's SFW,
ds
James Oberg has been known as a NASA/Government shill for ages. He takes every opportunity to voice 'his' expert opinion on UFO phenomena. Why should this be any different?
I actually believe that they put the satellite up just to shoot it down. Did anyone see what was actually on the spy sat? It just seemed all to convenient for me.
we didn't clutter up useful orbit space with a bunch of debris when we were done
Just how was that achieved?
you had me at #!
Why is anymore reason than that needed?
Hey -- stop drinking the Kool-Aid -- leave some for the rest of us.
Why is there an "insightful" mod and why isn't it "-1"? If I wanted insight, I wouldn't be reading
The US is going to get criticized by someone for any choice it could possibly make, including doing nothing.
This applies to much, much more than just satellite disposal.
Oberg goes on to quote 'There is a widespread notion that meteorites falling to Earth arrive red hot.' He is correct here. In fact, meteorites falling through the atmosphere typically explode, shattering into dozens or hundreds of pieces; something that occurs at the point when the dynamic pressure on the leading face exceeds the yield stress of the material. This occurs for meteoroids of all compositions, including nickle-iron meteorites that are far more robust than hydrazine tanks. If the atmospheric entry of meteorites is relevant, it hardly bolsters the case that a tank will enter intact (and if it's not relevent, why did Oberg bring it up?)
Perhaps he brings it up because that widespread notion is dead wrong. In fact, the parts of meteorites which make it all the way to the ground arrive quite cold, way below 'zero'. That's because of ablation. The outer part of the meteorite gets superheated by friction with the atmosphere, but before any significant portion of that heat can conduct to the inner part, the superheated part loses structural integrity and is torn away from the rest. However, the part torn away has, up until that moment, shielded the inner part from absorbing any direct friction heat.
Rinse and repeat. The end result is that whatever part does make it all the way to the ground is still at substantially the same temperature as it was when it entered the atmosphere.
Moderating "-1, Disagree" is simple censorship. Have the guts to post your opinion.
I don't understand this, so hopefully you can help me out. If you go through the effort of putting something into space, why not just send it to Mars? Do we gain anything from slowing it down and landing it on the Moon and then having to overcome the Moon's gravity? If you had a rocket already there, and you had to decide whether to send the rocket already on the Moon or to send a rocket on the Earth, then obviously the Moon is the better choice. But why take a rocket from the Earth just to put it on the Moon in order to send it to Mars?
Stop Global Warming!
Just say no to irreversible processes!
The US did not require that much sophistication. Since the satellite was on its way down, the attack was more akin to shooting down an ICBM when its location and velocity are both known well in advance.
Well if shooting down ICBM's was so fucking simple we'd already have a fully functional Star Wars implementation by now.
There are several advantages to launching from the moon.
Earth's Gravity well is pretty big. A spacecraft of any size capable of carrying a decently equipped mission, or even just some of the stuff needed, would be quite large. Getting it into space from the Surface of the Earth in one go would be prohibitively hard.
Launching it into low earth orbit a bit at a time sounds good, but then the assembled spacecraft still has to achieve 10.9km/sec to escape Earth's Gravity.
From the Moon escape velocity is just 2.4km/sec, so you can assemble the spacecraft either in orbit of the Moon, or on its surface, having had a much easier time sending smaller bits to the Moon, then launch from there. This means you can use either less fuel or have a much larger spacecraft.
A learning experience is one of those things that say, 'You know that thing you just did? Don't do that.' - D. Adams
Well if shooting down ICBM's was so fucking simple we'd already have a fully functional Star Wars implementation by now.
Shooting down ICBMs would be a helluva lot easier if we had as much notice about their intended positions and velocities as we had with USA-193. If only we would require ~1-month advanced notice before anyone lights one off.
He's getting rather old, but he's a good mouse.
Use a Third Party for revealing info.
Said satellite contains expensive, highly-classefied equipment
When will the world learn that open source is the way to go ? Security through obscurity really means you don't know exactly how much the enemy knows about you, which of course means you're that much more worried and uptight about it all. If all your cards are out in the open, you might not have the intel advantage, but you also don't have to worry about how much China or Russia knows. You can safely assume they know everything, and you can concentrate on beating them with pure skill and ingenuity. If you can't, then you deserve to fail.
-Billco, Fnarg.com
I wouldn't have known the submitter's name if I hadn't seen a "+5 insightful" with the man's name in the subject and his university in the body.
For all we know the moon may be as conscious as a poet or a realtor, and extremely weary of its monotonous round. - HLM
didn't you guys read the slashdot link yesterday? the world is flat and satellites are a hoax.
therefore, there must be an unknown conspiracy for the government to create a new hoax to destroy an old hoax, but we don't know what it is yet.
Are you joking? The SM-3 the US used is a four stage interceptor! Booster, main stage, dual pulse third stage, kill vehicle.
The submitter wrote:
I'm not sure why the submitter seems to have only partially quoted Oberg here (apparently out of context), and ignored the point Oberg was trying to make. Although meteorites entering the atmosphere generate a fireball, there seems to be ample evidence that the objects themselves remain cold even upon impact.
I'll cite a few articles here:
From this NASA page titled "Hot Meteors and Cold Meteorites," under the section titled "Meteorites Don't Pop Corn," we have this salient paragraph:
A slightly less assertive article on Howstuffworks is a little more reserved in its claims:
A more nuanced perspective is provided by this amateur astronomer who specializes in the study of meteors (specifically meteor spectroscopy). It's a short read, but a little too long to block quote here. Suffice it to say, there are numerous factors, including the composition and albedo (reflectivity) of the object, whether it was camping out in the Earth's shadow prior to impact (and for how long), the trajectory and velocity upon entering the atmosphere, etc.
Seems to me that the submitter is conflating two separate thoughts. Oberg brings up meteorites because they can and do impact the Earth while still cold, or only moderately warm. That's as far as the analogy goes -- he apparently wants to make the case that an object can remain cold enough that hydrazine fuel inside the container in question might not vaporize prior to impact. Whether we want to extend the analogy to the question of whether the container will shatter during re-entry is a question best asked of metallurgists or material scientists, and that I suspect depends entirely on the composition and manufacture of the fuel tank. (For that matter, whether a meteorite shatters upon re-entry would seem to be a function of the composition of the object, as well as the stresses it encounters -- and those stresses would be a function of speed and trajectory, as well as shape, would they not?)
This isn't an issue of 'security by obscurity' -- it's the double issue of protecting capabilities that might not yet be evident to an opponent, and of protecting the means of technical achievement of a capability even once the capability itself becomes known.
By the way, with an estimated population of 13.1 persons per square km under that satellite with a random reentry time, you'd get about 0.3 person inside that "hazard area". That's pretty small, but it's not zero and it doesn't look like the government's goal of less than 1/10,000. It's been said here already, but by the time it reaches Bush's desk it's boiled down to: 1) Could we make it worse? (NO) 2) Could we make it better? (MAYBE) Probabilities don't comfort victims or leaders.
(The numbers quoted above are accurate and come from a variety of sources, not all free.)
I have also heard - though don't quite believe - another reason that may have influenced it: the Air Force supposedly has recently become very interested in "smart crowbars" - orbital kinetic munitions.
And suddenly the Navy demonstrates ASAT capability.
Hasn't one of the ideological doctrines of the US Armed Forces, from day one, been that any rogue branch can be dealt with by the other two?
You're making me think. You won't like me when I'm thinking.
How much do you want to bet that someone scored a holy hell of a black-budget contract out of that demo? When trying to puzzle out the governments shadowier actions, never forget profit motive. Most of the guts of our government is public/private ventures these days.
In Capitalist America, bank robs you!
Actually the US Air FOrce shot down one back in 1985 using a kinetic weapon system
f all your cards are out in the open, you might not have the intel advantage, but you also don't have to worry about how much China or Russia knows. You can safely assume they know everything, and you can concentrate on beating them with pure skill and ingenuity. If you can't, then you deserve to fail.
Tell ya what. I will play a game of poker with you under these rules. You always show me your cards, and I will keep mine hidden. I admin I am a total n00b at poker.
I betcha, somehow, I will manage to win despite all of your skill.
See my journal for slashdot ID's by year. Mine created in 2005. http://slashdot.org/journal/289875/slashdot-ids-by-year
Exactly. Obviously, the best situation is for your opponent to not know your capabilities at all, since it's harder for him to defend against a complete unknown. But even if he does know your capabilities, hiding the technical details does two things: it still makes it harder for him to defend against (think missile guidance and electronic warfare), and it keeps that technology out of his hands so he can't use it against you.
Intelligence (and warfare) isn't a business competition, a school project, or a rec-league sport. Stuff like this can be literally life-or-death. Spending the extra money and effort to keep critical technology hidden can make a difference down the road and mean that more of your guys might make it home.
In war (and other serious, life/death situations), finding yourself in a fair fight means you screwed up somewhere.
The meek may inherit the earth, but the strong shall take the stars.
Since I've been using hydrazine scalp cream, I've regained a full head of hair and my private assets have significantly increased in size.
Just for the sake of anyone reading, "private assets" does not mean "genitals" in this context. It means "tumors".
The enemies of Democracy are
Forget the bus load of school kids, if it killed a single polar bear the liberals would be all over the president.
If it hit some barren waste land and they found a dead elk within a mile of it, there would be hell to pay.
That sound right, once, of course, you have the industrial infrastructure in place to build major (by weight) components from indigenous materials on the Moon. In the near term that ain't gonna happen. Wait several decades (or more) and maybe it does, but not until after someone makes it to Mars on a more direct flight.
Sure, and in fact, if this was an ASAT test, it would be a competence failure in the Bush Administration even greater than the Iraq debacle. The fact is that this is limited in comparison to real-world war-oriented ASAT scenarios, and was an easy shot as far as that field goes.
As a demonstration ("See? The ABM program isn't so bad!") it might also be useful...
LedgerSMB: Open source Accounting/ERP
I have a great deal of respect for Jim O , but he knows that he and I differ in our opinions regarding the destruction of 193. As one of those observers who followed this bird through 2007 and as the unfortunate soul who was , seemingly , the only person to obtain high power images of it on a number of occassions , I formed my own opinion , based on what I saw and the fact that there was no way the Pentagon was going to allow this satellite to fall any lower , let alone , re -enter. Its quite simple , at 300 km I could see the basic outline of the satellite using back yard equipment.At 200 km I would have seen "much" more detail had I had the opportunity. If I could do that , then the opposition , using much more expensive kit , and adaptive optics would have been able to discriminate the exact shape and proportions of the spacecraft , from which it could then glean a great deal of intelligence. ( See my recent images of Persona ) As I stated back in mid December 2007 "The Pentagon will not allow this bird to come much lower and will probably destroy it on orbit." Those words were , at the time , met with derision but proved to be correct. The chances of the tank making ground in tact in a densly populated area were infinitesimal. We will probably never know the truth , but for my part , I'm convinced that the toxic ice cube theory was simply fabricated to mask the real reasons for the satellite's destruction. More details on both Persona and USA 193 at http://satcom.website.orange.co.uk/
dick-measuring competition?
People compete at measuring dicks? Really?
This begs the question: Who do they measure?
I just pooped your party.
Why shoot down a satellite?
Because shooting it up would cost more
(ducks)
I'm sure the submitter had a reason to want to post this anonymously. He made a mistake, but his intention was clear
Actually, it's not at all clear that he did make a mistake; the semi-anonymousness may have been by intention. He may have not wanted his name up at the the top level, but had no reason not to have his identity accessible to anybody who wanted to take the time to drill down.
--- .sig
If I weren't an Anonymous Coward, this would be my
why engineers are not making satellites returning or recycling themselves outter in the space?
just like wall-e.....hahahaha......
finally
humans' killing humans
we make our own graveyard...
Look carefully at the size of it. It was not just a spy sat. It had other uses.
Spy satellites are pretty damn big. Remember that the resolution of what you can see on the ground is proportional to the size of the optical element. So the bigger they are, the better they see.
So "looking at the size" alone won't tell you it's not a spy satellite.
5. Congress made them set the fire control system, missiles, and software back to that before the operation. So nobody can even reasonably claim it's provocative.
Almost, but remember that for the satellite to come down and not leave a debris field, it has to have entered the atmosphere. At that point, you have all sorts of aerodynamic effects that lead to a non-perfect trajectory. This is especially true since there is no active controller on board.
When a satellite comes down, it has a landing ellipse with Gaussian probability (whose distribution you can find through Monte Carlo analysis). Your kill vehicle is mechanically simpler than those used to shoot down something in orbit, but requires much more sophisticated guidance and control.
"Higgins did not say what he is quoted as saying in the place he was reported as saying it. This may merely be sloppy journalism -- maybe he said it somewhere else."
Now, you just posted to say that he did not say it in the article referenced by the link that Oberg posted, but instead said it in a different place, one that could have been found with a bit of clicking around.
You are agreeing with the article you're disagreeing with. The original article says "maybe he said it somewhere else" and you're saying "he said it somewhere else."
At the very most, the substance of your critique seems to be "Well, what he said was correct, but I vehemently disagree with the tone in which he said it."
I used to work on satelite recovery equipment. Specifically pingers that were attached to the frame of the satelite, so that when they crashed into the sea, they could be located and retrieved. What made it thru the atmosphere to the earth's surface was typically no more than the frame, but there was always hope that the recording media would make it. Satelites never made it back nearly intact, which is what it would take for the hydrazine tank to be a hazard. This could easily be found out with a little research. So, yes, hydrazine tank hazard is BS of military stupidity level and size.
wake up and hold your nose
Thanks for the thoughtful critiques and suggestions, it'll take me a little time to work through them and engage specific messages. But the story is flaring up again in half a dozen spots across the WWW. // Jim O
this world's tallest [known]
semi-retired rocket scientist
rcamans, the last US satellite I know of that required sea recovery was in 1975, and before that, lots and lots had made it back intact. Can you share more detailed memories so we can see if you really were where you say?