US Claims Satellite Shoot-Down Success 616
Readers of Slashdot last valentines day will remember discussing US Plans to Shoot down a damaged spy satellite. An anonymous reader noted that the US is
reporting success last night, thus saving us from hydrazine exposure. Of course this makes me wonder- if it's this easy, wouldn't an international super power war pretty much immediately mean the downing of every satellite in orbit?
priorities? (Score:5, Informative)
Video (Score:5, Informative)
Comment removed (Score:2, Informative)
Re:Wasn't that the whole point (Score:3, Informative)
This was a known, failed satellite that was coming down in an unknown, possibly populated area. It still had a full load of hydrazine, which is poisonous. The satellite was already in a low orbit, and any debris from the missile impact would deorbit in a short period of time.
The Chinese shot a shut-down satellite that was in a stable orbit approx 528 miles up. They created over 4000 pieces of debris in the same orbit, half of them over 4 inches in size.
The only dick that's waving around here is you.
Re:Wasn't that the whole point (Score:5, Informative)
Re:Wasn't that the whole point (Score:5, Informative)
Yes they expect them to fall out of the sky... (Score:5, Informative)
Re:Wasn't that the whole point (Score:2, Informative)
Just need to reiterate: the danger from the hydrazine was essentially ZERO. Hydrazine is remarkably unstable. It would have been the first thing to be destroyed upon reentry, just as soon as the tank ruptured or a hose broke loose.
Re:Wasn't that the whole point (Score:4, Informative)
This is a cover story and nothing more. The hydrazine has a low boiling point (114C). The high temperatures from the satellite rentry would have boiled the hydrazine and caused fuel tank rupture LONG before the satellite hit the ground.
The reasons the military shot this down are simple:
#1: To remind China we can do it, and we're so sure we can do it we have no problems being put on the spot about doing it.
#2: This was a spy satellite, as such it has a lot of very secret very advanced tech, which since it *IS* a spy satellite often flies over land we don't control. The military did not want anything to be recovered by another country. The US has recovered satellites from the former Soviet Union, so we know how much can survive.
Re:"Pull!" [ratchet] [BANG] [ping!]... "Pull!" ... (Score:3, Informative)
GPS sats are 12600 km up, that's not exactly "low orbit".
Re:Wasn't that the whole point (Score:3, Informative)
Here's a material safety data sheet for hydrazine: http://www.sciencelab.com/xMSDS-Hydrazine-9924279 [sciencelab.com] (pdf). It is extremely nasty stuff. Note in particular the full-suit requirements, and the teensy-sized lethal exposure levels.
Hydrazine is one of those substances where if you can smell it, you're already dead.
So maybe this is just a little drama. Maybe there was a secret self-destruct device in the (totally secret) satellite, and they pushed the button just as the missile approached, thus guaranteeing a success.
But do NOT disrespect the hydrazine.
Re:In other conspiracy-related news... (Score:3, Informative)
Re:"Pull!" [ratchet] [BANG] [ping!]... "Pull!" ... (Score:5, Informative)
If you start blowing up sattelites in stable orbits, you are playing a kind of russian roulette that could start a chain reaction, destroying all satellites in a given orbit zone. The fragments of broken sattelites don't slow down, like on earth, nor is the chance that they come down to earth and burn up in the atmosphere particularly high (especially with high-altitude orbits). They will mostly start zinging around the earth in various orbits until they make contact with another satellite, causing more debris. Here, I use the word satellite in it's loosest sense: meaning a conventional communications satellite, or a space shuttle, or a space station, an astronaut on a spacewalk or even the moon itself.
This kind of event would make the orbits unusable for the foreseeable future - it is a real risk even without people blowing things up - and we don't yet have a good solution. Research is focussing on using things like aerogel to trap this kind of debris and bring it out of orbit. As long as you can take more debris out of orbit than is being created, you should be able to prevent a chain reaction. But for the moment there is no solution.
It's not about hydrazine- and it's not new. (Score:5, Informative)
2. The likelihood of the propellant tank making it to Earth in a populated area while still sufficiently intact to release hydrazine on impact is infinitesimal. The satellite was launched in 12/06, and represents the pinnacle (well, a year ago) of US spy satellite technology. There's plenty of good coverage in The Washington Post that supports both of these points.
Make no mistake about it, this is all about preventing the tech from falling into the wrong hands.
Re:Wasn't that the whole point (Score:3, Informative)
No Hydrazine would make it to the surface of the earth in that form.
Video of the intercept (Score:5, Informative)
http://www.liveleak.com/view?i=71c_1203596547 [liveleak.com]
Like hitting a bullet with a bullet. Neat engineering feat.
Cold War News (IE, Old Hat) (Score:5, Informative)
USN's Standard SM-3 missiles are their new Black and Decker tools of fleet defense. They pulled a preproduction bird off the table, loaded a ASAT seeker on it and sent it on it's way.
A little bit more on the new theater missile interceptor;
http://www.globalsecurity.org/space/systems/sm3.htm [globalsecurity.org]
Re:Wasn't that the whole point (Score:5, Informative)
Re:Wasn't that the whole point (Score:5, Informative)
Not necessarily. If the hydrazine tank is parked in the center of the vehicle it's very probable that it could remain cold enough. You completely negate radiation and most likely convection depending on design, so you rely solely on conduction for heating. If you have a big, massive satellite that is densely packed it is conceivable that the center could remain cold, just like the Apollo modules kept three people comfortable for reentry. Also a big dense object like a satellite is likely to stay intact through re-entry with very little breakup.
Although I agree there is much more at stake than just hydrazine, and I think spy secrets alone would have been justification, there's no saying the hydrazine would be completely gone. There's multiple justifications for this shot, they just picked one to tell people.
Re:Wasn't that the whole point (Score:4, Informative)
Except a similar hydrazine tank on the Columbia did survive and the fuel was still liquid inside. Which is why it was believed by NASA this one would survive as well.
Personally, I think the risk was overblown (the chances of it affecting a populated area are slim, but better safe than sorry, I guess), but to say everything bad would have burned up on re-entry is unsubstantiated and probably wrong.
Re:Wasn't that the whole point (Score:3, Informative)
And you know this how exactly ?
Summary Info (Score:5, Informative)
USS Lake Erie [wikipedia.org]
Missle Used:
SM-3 [wikipedia.org] with kinetic interceptor [wikimedia.org]
Tracking was probably provided by the SBX [wikipedia.org] amongst other sensors.
Previous intercept videos of importance:
Japan Defence SM-3 test [dailymotion.com]
Prior shot from USS Lake Erie [youtube.com]
The propaganda that I find really funny is the DoD stating that it "nailed" [cnn.com] the fuel tank. C'mon, the impact probably released over 100 megajoules of energy. Were they really aiming for the "fuel tank" or just trying to hit the damn thing? With that much energy, who cares?
Big Dick waiving, yes. Technical success, yes. Political success, TBD.
On a side note, I was reading a story [bwcinet.com] written by a guy who was stationed at Thule AFB in Greenland where one of the first BMEWS (Ballistic Missle Early Warning System) Radars was deployed back in the late 50's early 60's. From a tech standpoint, it is quite fascinating what we could do back then with such limited technology and how it was accomplished. Read the intro through the epilog, I enjoyed it, so I'm passing it along...
Not every one, (Score:4, Informative)
Re:Wasn't that the whole point (Score:5, Informative)
Re:Wasn't that the whole point (Score:4, Informative)
Re:Wasn't that the whole point (Score:5, Informative)
Re:Wasn't that the whole point (Score:4, Informative)
Gravity. It's closer to earth than the Chinese satellite was, so the effects of gravity are greater. Also the effects of the extremely thin atmosphere also slow it down and allow gravity to affect it.
Re:Wasn't that the whole point (Score:5, Informative)
First, the Columbia hydrazine tank was part of the Columbia...a shuttle. The satellite tank was part of an object that was never designed to survive reentry.
Second, the hydrazine tank on the Columbia was shielded from the worst of the reentry temperatures. The Columbia didn't lose integrity and break up until well into the atmosphere.
Third, the tank was found ruptured.
There's nothing 'similar' about the two scenarios, and the Columbia tank ruptured anyway.
Re:Wasn't that the whole point (Score:3, Informative)
Re:Wasn't that the whole point (Score:5, Informative)
The satellite that was shot down yesterday was very, very close to the Earth's atmosphere. It was only one rotation, maybe less, away from starting to graze it (which means that it would slow down and begin to reenter and burn up). If we assume that when it was destroyed, pieces flew in all directions, some of them would have ended up with a greater net orbital velocity at the end. These pieces aren't the ones that exploded *up* (normal to the surface of the Earth), though, they're the ones that exploded *forward* (in the direction of the satellite's motion). They picked up some velocity and would end up in a slightly higher orbit as a result. I suspect it's not much of a higher orbit, though -- if anything, it probably just means they'll take a little longer to hit the atmosphere than other parts. It's tough to say without doing any calculations, but I doubt you have enough Delta-V to push the pieces into a long-term stable orbit. (Unless maybe the rocket fuel detonated.) The difference in velocities between high, long-term stable orbits and low atmosphere-grazing orbits is pretty substantial.
The pieces that flew off in other directions aren't really a huge concern, because they all end up in the same or lower orbits. Plus because you've blasted the satellite into little pieces and thus increased its surface area tremendously, it'll start slowing down on hitting the atmosphere much more quickly, and the pieces will burn up more completely on their way down.
My understanding is that what the Chinese did was quite different. The satellite they shot at was way out in a stable orbit, and thus the pieces it was reduced to stayed there as well. So now instead of a dead satellite floating around in orbit that's relatively easy to track and avoid, you have a vast cloud of small debris. Not an improvement at all.
Re:Wasn't that the whole point (Score:5, Informative)
Absolutely I would claim that.
Hydrazine is a solid below about 1 deg C. This was a dead satellite. No heat, no power supplies. In other words, you have an insulated pressure vessel (fairly well-built) containing 1,000 lb of hydrazine ice at roughly -273 deg C. That's a LOT of thermal mass; the ice inside the tank would absorb a lot of the reentry heat, preventing the metal from melting for quite some time. Did you ever do that science experiment where you try to burn a paper cup containing water? Doesn't work until you boil off all the water. Same thing here, but we're talking about metal which is even more thermally conductive than paper.
Furthermore, a lot of the surrounding structure must ablate or melt away before the tank can be directly affected by the reentry.
Also, in case you want to compare a thousand-pound meteorite to this satellite: a satellite does not orbit as fast as your typical meteor reentry speed, so you cannot compare the reentry energy to a typical meteorite ablation rate.
If you need proof, consider that hydrazine tanks from the Space Shuttle Columbia accident DID impact in some Florida woods. They were NOT cold-soaked at absolute zero for two years - they were prepped for flight, heated, etc., and wrapped in far more spacecraft structure than this satellite. And they were not full, like these tanks were. That should demonstrate the reality of this risk.
Want to see a photo of a far smaller hydrazine tank, and some other unidentified tanks, AFTER they landed in Florida? http://www.io.com/~o_m/clfaq/s3.htm [io.com]
http://www.io.com/~o_m/clfaq/images/debris_shots/tank1.jpg [io.com]
http://www.io.com/~o_m/clfaq/images/debris_shots/tank2.jpg [io.com]
http://www.io.com/~o_m/clfaq/images/debris_shots/tank3.jpg [io.com]
Most interestingly, these bits of spacecraft look completely uncharred, unmelted, almost new except for a lack of paint.
Followup and oblig. car analogy (Score:5, Informative)
The way most anti-satellite and anti-ballistic-missile weapons work isn't by blowing up the target, it's basically by just positioning itself in front of the target, and letting physics do the rest. The satellite has a huge velocity in one direction, the missile a huge velocity in the other, they slam into each other -- wham -- target destroyed.
Imagining the satellite just blowing up, with pieces flying everywhere, isn't a good model for the interaction. Although it's not impossible for some pieces to end up with a greater forward velocity than the satellite originally had, conservation of momentum tells us that most of the combined mass is going to end up with a velocity substantially less than what the satellite had to begin with.
(Car analogy: A racecar is going around a track at some incredible speed, say 200MPH. You decide to kill it by taking another car, and driving it in the opposite direction, intercepting the racecar head-on. Without getting too deeply into the mechanics of the collision, the result when the two cars smash into each other is that most of the pieces are probably going to be going less than 200 MPH in the racecar's original direction. Assuming the car's fuel tank doesn't detonate and add a lot of energy to the system.)
So overall, I don't think there's much of a risk with a kinetic ASW that you're going to blast pieces into a substantially higher orbit than where the satellite was originally. If the satellite is already in a high stable orbit, you may have a big cloud of junk in space for a long time though.
Re:Wasn't that the whole point (Score:5, Informative)
Maybe you should look at some of the photos of the skylab debris before making your assumptions.
Re: Wasn't that the whole point (Score:5, Informative)
Orbits have a point of closest approach, which for the Earth is called perigee, and a point of farthest approach which as called apogee. Whenever an approximately circular orbit has a new velocity imparted, the orbit will become an ellipse. The counterintuitive thing about orbital mechanics is that the point where the velocity change occurred (in this case, where the missile hit) will not change on subsequent orbits.
Now assume a particle had an increased velocity because of the missile hit. It now has a "higher" orbit in that the point opposite the missile hit will be farther from the earth. However, its perigee is still the point where the missile hit. Atmospheric drag is significant at the satellite's current altitude, and thus it's velocity at that point will be reduced on every orbit, which will cause apogee to get lower and lower until the orbit is circular and it returns to the entire orbit decaying due to drag. This circularization time is small. Therefore, there is no concern about new orbital debris due to this satellite.
Anything that now has a reduced orbital velocity will only decay sooner, as its apogee is where the missile hit, and the perigee will be deeper in the atmosphere.
Re:in other news (Score:5, Informative)
Russia goes on about us using it as a cover for anti-satellite testing. As sh00z [slashdot.org] mentioned, it's an anti-missile missile. Then they ramble about how toxic fuel has crashed to Earth before and how they think it isn't a big deal. But since we didn't know where it would exactly land and don't have the luxury or using Siberia or Kazakhstan as a crash site, there could be enough risk of exposure to civilians as it was projected to hit North America. Besides, I'd like to hope we shoot for a higher safety standard than Russia. They do a lot of really cool things for really cheap
I found China's response is both hilarious and hypocritical. Their concern about security in space is a joke given that they hit a real satellite just last year. At 800 km against our 200 km! I think their test says more than ours in the international dick waving sense - plus a majority of their debris won't burn up within a week. I don't really see the two launches as apples to apples; more like China totaling a working 1993 Honda and the US totaling a 2007 BMW with a cracked engine block.
Odds are quite good that it was really just to destroy the top secret components on the satellite. Fair enough since it's our tech and we don't like giving it away. The environmental concern with the hydrazine happens to be convenient whether as a cover or for real legitimate concern - hydrazine is nasty stuff regardless. As for a weapons test, the missile couldn't hit a satellite in use. It really could only be useful as both a cruise phase interceptor test and a cold tracking (no infrared) sensor test. Besides, it's been known for years that the US can hit working satellites - no need to flip out over hitting a lame bird.
Re:Wasn't that the whole point (Score:4, Informative)
Net velocity for the two masses (satellite and the missile) probability somewhere around 1 kilometer per second, assuming the missile had a mass that was about half the satellites upon impact and they where traveling at roughly the same velocity, only in opposite vectors. 1kps is really slow for orbital velocities. For example the space shuttle has an orbital velocity around 7kps to obtain a stable low earth orbit. Not quite the
oh, I personally agree that the primary reason for the shoot was saber rattling. But the "stated" reason, hydrazine exposure, has merit, IMHO.
Re:Wasn't that the whole point (Score:4, Informative)
Of course we are talking about budgets and politics and there will be spin. Anyone who actually knows in high detail what has happened, is happening and what current capabilities exist, wont be posting here. I feel comfortable saying that the US military has successfully demonstrated that it has the capability to take down satellites in the past. I also feel comfortable with the idea that modifying an sm3 to do the same and then testing such is not a huge mistake because it gives away too much to the Chinese. But everyone is entitled to their opinion - I'm just sharing mine.
Re:Wasn't that the whole point (Score:1, Informative)
Re:Wasn't that the whole point (Score:5, Informative)
The satellite that was shot down yesterday was very, very close to the Earth's atmosphere. It was only one rotation, maybe less, away from starting to graze it
The satellite was never really out of the atmosphere, because as you go up in altitude, the atmosphere never really stops. The number of molecules per unit volume just gets smaller and smaller.
Every time a satellite hits a molecule, it loses a tiny amount of energy, and that lowers its orbit by a tiny amount. The lower the orbit gets, the more molecules get in the way, so the process gradually accelerates until the satellite "burns in".
At the high altitudes used by communications birds, the concentration of molecules is barely above that of deep space, which I believe is on the order of one per cubic meter, and it can take centuries for the decay process to get on a roll. At the other end of the scale, there is a tipping point around 150 miles up, where the satellite will be losing measurable altitude from one rev to the next, and reentry is imminent; that's where this satellite was yesterday.
In other words, the satellite was on the way down because it was getting lower in the atmosphere, not "close to it".
rj
Re:Wasn't that the whole point (Score:3, Informative)
Second, even if the tank didn't melt, it would still undergo structural failure at some point due to the terrific pressure hydrazine would generate at those temperatures. And as soon as the containment failed, the hydrazine would begin to decompose. Since it is a monopropellant, it wouldn't need the presence of another gas for this reaction to commence, and the entire tankful would break down in short order.
That was just the first link that came up on a Google News search.
And you don't know what temperature the hydrazine fuel would reach inside the tank. Remember, the tank is heavily insulated to protect it against the extreme temperatures it would be subjected to during orbit.
Re:Video of the intercept (Score:5, Informative)
HD Modeling of the Chinese ASAT test ... (Score:5, Informative)
Good model of the debris field caused by the China ASAT test. As you mention, "stuff" doesn't just fly everywhere.
Re:Wasn't that the whole point (Score:5, Informative)
It's not as bad as they make it out to be. Ocean water is corrosive; alcohol is toxic; many solvents are mutagenic; lighter fluid is flammable. All of those things are stored in tanks.
Hydrazine is corrosive, but so are most things that are stored in stainless steel containers (although chlorides are typically not stored in stainless steel, it causes cracks). The hydrazine tank on the F-16 is stainless through and through, as are the tubes and hoses that it would utilize if the epu is fired. Here's a picture of the F-16 epu tank:
http://www.advpack.com/custom_shipping_cases/custom_cases.html [advpack.com]
It's the cylinder in the second case down. For reference, the tank is about 3.5-4 feet long. I'd say it holds about 15 gallons or so. That tank IS pretty heavy-duty, as you mentioned; it typically survives a crash. However, the tank and associate hardware, when filled, weigh upwards of 150 pounds, which would be unacceptable for a satellite that did not have to endure frequent landings or a crash. It is very likely that the hydrazine tank on the spy sat is nearly identical to this one...
http://www.psi-pci.com/images/80200.jpg [psi-pci.com]
I doubt that it would have made it to the surface. Even if it did hit a house, it would probably only do as much damage as an equally-sized and massed device would. Ke=1/2mv^2 and all that.
I personally know of at least one person here on base who's been exposed to hydrazine, and he's fine.
-b
Something to keep in mind (Score:5, Informative)
It is known that the velocity of the missile will taper off as it gains altitude due to gravity and because it's a kinetic kill vehicle that means it's effectiveness is a function of the closing velocity between the warhead and the target.
Remember - orbital speeds are fantastic. [wikipedia.org] If we could simply lob a brick in front of the orbital path a satellite - the closing velocity would still be massive.
Most of the kinetic heave-ho that will kill the satellite is probably coming from the satellite itself.
Re:Wasn't that the whole point (Score:2, Informative)
Re:Wasn't that the whole point (Score:3, Informative)
Hydrazine is a liquid so it would not be stored under pressure. Given that there would be a 1 bar differential pressure maximum between the inside and the outside of the bottle in space before using any fuel, the tank would NOT need to be designed as a pressure vessel under PV codes. And if it was relieved with a valve or bursting disc, then there wouldn't be any left once it reached the ground anyway!
The temperature that an object travelling through the atmosphere reaches can be calculated using the Bernoulli equation. An LEO satellite is travelling approximately 7 km/s when in orbit. Let us work out how hot it would reach at that speed at sea level. For conservative purposes, we will disregard the additional speed it would pick up from conversion from potential energy.
Air impacting the surface of the satellite will be (from the satellite's reference frame) be decelerated from 7 km/s to 0. This is a kinetic energy change of (7000^2)/2 = 24 500 000 J/kg, or 24.5 MJ/kg. Air has a heat capacity of approximately 1 kJ / kg K. Therefore the front of the satellite will be exposed to a temperature of around 24 500 C, assuming 0 C air for simplicity.
If only 6% of the kinetic energy that the satellite had *before it started falling and moving faster* is absorbed by the satellite it would be sufficient to melt steel. Not to mention that any temperature rise will boil the hydrazine and probably burst the tank anyway.
I don't know what the inversion point is for hydrazine, but above a certain temperature, evaporative cooling becomes heating due to the weirdness that is the Joule Thompson effect. So I wouldn't rely on that either.