Forgot your password?
typodupeerror
The Military Space

US Claims Satellite Shoot-Down Success 616

Posted by CmdrTaco
from the hope-your-foil-hat-was-on-snug dept.
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?
This discussion has been archived. No new comments can be posted.

US Claims Satellite Shoot-Down Success

Comments Filter:
  • priorities? (Score:5, Informative)

    by Twisted Willie (1035374) on Thursday February 21, 2008 @09:47AM (#22501382)

    if it's this easy, wouldn't an international super power war pretty much immediately mean the downing of every satellite in orbit?
    If this super power war were to actually happen, somehow I don't think satellites dropping out of the sky would be my first concern.
  • Video (Score:5, Informative)

    by groovelator (994174) on Thursday February 21, 2008 @09:53AM (#22501426) Homepage
    A video [ksdk.com]... A great success! Huzzah!
  • by falcon5768 (629591) <Falcon5768@@@comcast...net> on Thursday February 21, 2008 @09:58AM (#22501472) Journal
    Except thats EXACTLY what they did... made the entire world think the US was in a arms race with China now. Even Conservative members of our government think this was a stupid move since it basically created a pissing match with China who now know our capabilities instead of having to guess at them.
  • by Macgruder (127971) <chandies.williamson@gma i l .com> on Thursday February 21, 2008 @09:58AM (#22501484)
    EXACT same thing? I beg to differ.

    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.
  • by Urban Garlic (447282) on Thursday February 21, 2008 @10:00AM (#22501494)
    I agree about the military posturing, but it's important to point out that China did not in fact do exactly the same thing -- the Chinese satellite was in a fairly stable polar orbit, so the debris cloud from that exercise will be an orbital hazard for hundreds of years. The American military at least had the decency to toast a decaying satellite, so the debris will re-enter sooner rather than later.
  • by atommota (1024887) on Thursday February 21, 2008 @10:00AM (#22501496)

    This was all a dickwaving scheme by the military who not too long ago was up in arms over China doing the EXACT same thing but being upfront about it being a test and not using a falling sat as a scheme to show off.
    People were pissed at China for shooting it in high orbit where the debris would cause problems. Most of usa193 will re-enter in 48 hours, with the remainder in 40 days. Big difference there. A satellite is falling, we may as well test a missile system on it. We already proved we could do it over two decades ago anyways. http://en.wikipedia.org/wiki/Solwind_P78-1 [wikipedia.org]
  • by nexuspal (720736) on Thursday February 21, 2008 @10:06AM (#22501570)
    All of our weapons, bombs in particular, are guided primarily by inertial guidance systems. They rely on GPS simply to increase accuracy, though the GPS updates take a significant amount of time relative to the distance the bomb has dropped. The weapon relies on the inertial guidance for most of it's trip, using the GPS to correct for errors that occure over time because of physical constraints inherent in the inertial guidance systems. With or without GPS they will still be deadly accurate.
  • by TripMaster Monkey (862126) on Thursday February 21, 2008 @10:10AM (#22501628)
    It still had a full load of hydrazine, which is poisonous.

    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.
  • by Binestar (28861) on Thursday February 21, 2008 @10:12AM (#22501652) Homepage
    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.

    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.
  • by Ihlosi (895663) on Thursday February 21, 2008 @10:14AM (#22501666)
    b)low orbit satellites like spy and GPS would be affected easily,

    GPS sats are 12600 km up, that's not exactly "low orbit".

  • by HawkinsD (267367) on Thursday February 21, 2008 @10:15AM (#22501682)
    I don't trust the government any more than you do, I suspect. But your assertion that the "hazards of the fuel where nil" seems incorrect.

    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.

  • by stoolpigeon (454276) * <bittercode@gmail> on Thursday February 21, 2008 @10:16AM (#22501702) Homepage Journal
    Nothing simply falls from the sky. The rate isn't alarming, you are just probably paying more attention. Military aviation is dangerous and has always been so. I can't think of a single cruise I did back in my time with the military that we didn't lose an aircraft and/or crew on board the ship. It's the nature of the job.
  • by danskal (878841) on Thursday February 21, 2008 @10:20AM (#22501736)
    It's much worse than that....

    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.
  • by thermowax (179226) on Thursday February 21, 2008 @10:21AM (#22501742)
    1. The US has shot down satellites before- in the 1980s. We've had this technology for a long time and everyone knows it. While there may be an element of dick-waving in this action, any nation with a developed intelligence infrastructure (or not, as it was in the press) has known for a long time that the US is capable of this.

    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.
  • by Binestar (28861) on Thursday February 21, 2008 @10:22AM (#22501750) Homepage
    As I said in an earlier post, Hydrazine may be dangerous, but it's also highly reactive and has a low boiling point (114C). During reentry the temperature would get so high that the hydrazine would boil, and rupture the hoses and piping system, not to mention rupture the tank it's stored in. Once that happens, since it's so reactive, it would burn up in a matter of seconds.

    No Hydrazine would make it to the surface of the earth in that form.
  • by Majin Bubu (455010) on Thursday February 21, 2008 @10:25AM (#22501806)
    Video of the intercept and relevant Pentagon briefing at:
    http://www.liveleak.com/view?i=71c_1203596547 [liveleak.com]

    Like hitting a bullet with a bullet. Neat engineering feat.
  • by TheHawke (237817) <rchapin.pelicancoast@net> on Thursday February 21, 2008 @10:26AM (#22501810)
    Back in the 70's and 80's both sides had ASAT weapons available, or were in testing. The Soviet Union had their orbital satellite killer. Fired atop a Proton booster, it would make orbit and line up with it's target, close and detonate it's warhead, turning it into swiss cheese. The USAF had a more flexible ASAT missile that looked alot like a supersized Phoenix air to air missile. It was tested on one target with a spectacular skin-skin kill as a result before the politicals kicked in and put a moratorium in place to keep the peace. One upshot of the ASAT weapon is that it could hit targets on a moment's notice. The USSR killsat you could dodge, as long as you had the fuel to do it. Neither of these could hit the geosynchronous birds, they were tailored to go after recon and commsat snoopers.

    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]
  • by nazg00l (699217) on Thursday February 21, 2008 @10:35AM (#22501920)
    I call bullshit. I have worked with hydrazine quite a lot for my Ph.D. and it is nowhere near what you scare us with. It is toxic, sure, just like most of organic chemistry, but in high concentrations and on prolonged exposure. FYI, LD of 500 ppm is equal to 0,5% concentration. It doesn't smell that bad, compared to other small-molecule nitrogen compounds. As many have mentioned, during reentry all the material would have completely vaporized and burned (i.e. oxidised) far above ground level. Talk about pretexts.
  • by everphilski (877346) on Thursday February 21, 2008 @10:35AM (#22501922) Journal
    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.

    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.
  • by Shining Celebi (853093) on Thursday February 21, 2008 @10:37AM (#22501946) Homepage

    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.

    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.

  • by CmdrGravy (645153) on Thursday February 21, 2008 @10:40AM (#22501996) Homepage

    During reentry the temperature would get so high that the hydrazine would boil, and rupture the hoses and piping system, not to mention rupture the tank it's stored


    And you know this how exactly ?
  • Summary Info (Score:5, Informative)

    by JumboMessiah (316083) on Thursday February 21, 2008 @10:40AM (#22502002)
    Ship that took the shot:
        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)

    by ZonkerWilliam (953437) * on Thursday February 21, 2008 @10:43AM (#22502058) Journal

    wouldn't an international super power war pretty much immediately mean the downing of every satellite in orbit?
    Not really, most communication satellites are in geosynchronous orbit, 22,000 some odd miles out from LEO. Much harder and much longer to get there.
  • by stoolpigeon (454276) * <bittercode@gmail> on Thursday February 21, 2008 @10:46AM (#22502098) Homepage Journal
    The maximum ceiling is still unknown. There's a very good chance that the people modifying and firing the missile weren't sure how many shots it would take, now they know too. There's no substitute for real experience, and I think what information was given up was a decent trade off for what was gained.
  • by ArieKremen (733795) on Thursday February 21, 2008 @10:59AM (#22502282)
    Except the Chinese shot down a satellite that was in orbit ~460 mi above the earth, the US satellite's orbit was ~130mi.
  • by jandrese (485) <kensama@vt.edu> on Thursday February 21, 2008 @11:01AM (#22502300) Homepage Journal
    Hydrazine is highly corrosive (in addition to being highly toxic, mutagenic, carcinogenic, and flammable. About the only thing it isn't is radioactive) and wouldn't be stored in steel tanks. Even tiny amounts of it are dangerous to humans. What's more, because it's so nasty it's likely stored in a rather sturdy container. Hydrazine containers were some of the larger chunks that survived the Columbia accident for example. Hydrazine is one of the big reasons NASA tells you never to handle any shuttle/satellite debris you might find.
  • by Binestar (28861) on Thursday February 21, 2008 @11:01AM (#22502308) Homepage
    Some one correct me please.

    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.
  • by TripMaster Monkey (862126) on Thursday February 21, 2008 @11:03AM (#22502334)
    Completely different scenario, chuckles.

    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.
  • by Kadin2048 (468275) <.slashdot.kadin. .at. .xoxy.net.> on Thursday February 21, 2008 @11:13AM (#22502460) Homepage Journal
    I think you're maybe misunderstanding a little of how 'orbit' works. In order to go 'up' or 'down' in orbit, you really need to go faster or slower. That is to say, if you want to get into a higher orbit, you need to accelerate, and start moving faster around the Earth. You don't just push up perpendicular (normal [wolfram.com]) to the Earth's surface, that doesn't work. (Well, it will work temporarily, but it won't get you into a higher orbit. You'll just fall back down, because you're not escaping gravity. Remember, orbit is all about falling towards the Earth but moving fast enough to miss it, continuously.)

    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.
  • by Goldenhawk (242867) on Thursday February 21, 2008 @11:29AM (#22502728) Homepage
    >Still wanna try to claim that tank would survive reentry?

    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.
  • by Kadin2048 (468275) <.slashdot.kadin. .at. .xoxy.net.> on Thursday February 21, 2008 @11:30AM (#22502760) Homepage Journal
    I'd also point out just as a followup to myself, that the assumption "when it was destroyed, pieces flew in all directions" is probably not a good one to make, either.

    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.
  • by avandesande (143899) on Thursday February 21, 2008 @11:39AM (#22502896) Journal
    Meteorites are still freezing cold in the center when they hit the earth, only the outside is heated.
    Maybe you should look at some of the photos of the skylab debris before making your assumptions.
  • by p_trekkie (597206) on Thursday February 21, 2008 @12:00PM (#22503172) Homepage
    Just to adding to your excellent explanation of orbital mechanics, this shootdown effort will not significantly affect the time it takes for the the pieces to come out of the sky regardless of what new velocity they have been given.

    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)

    by dyslexicbunny (940925) on Thursday February 21, 2008 @12:04PM (#22503234)
    I thought it was interesting looking through the international response to it.

    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.
  • by space_hippy (625619) on Thursday February 21, 2008 @12:17PM (#22503442)
    Hydrazine is not explosive. It is very reactive, but not explosive. People watch to many movies.

    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 .09kps for a space shuttle de-orbit velocity, but by no means a stable low earth orbit velocity. Shuttle information: http://spaceflight.nasa.gov/shuttle/reference/shutref/sts/requirements.html [nasa.gov]

    oh, I personally agree that the primary reason for the shoot was saber rattling. But the "stated" reason, hydrazine exposure, has merit, IMHO.
  • by stoolpigeon (454276) * <bittercode@gmail> on Thursday February 21, 2008 @12:21PM (#22503510) Homepage Journal
    This document http://www.ucsusa.org/global_security/space_weapons/a-history-of-asat-programs.html [ucsusa.org] has some good information, to my knowledge. It also reflects my understanding that programs like the almv program were stopped because of political considerations rather than technical problems. This article http://www.globalsecurity.org/space/systems/almv.htm [globalsecurity.org] seems to reflect the same.

    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.
  • by Anonymous Coward on Thursday February 21, 2008 @12:22PM (#22503530)
    In addition, even with a forward delta-V, the periapsis (lowest point of the orbit) would still be at the point where the collision occurred, so there would be plenty of atomspheric drag negative delta-V at that point to continue decaying the orbit of enhanced-velocity chunks as well.

  • by Deadstick (535032) on Thursday February 21, 2008 @12:56PM (#22504034)
    Excellent analysis. I'll just issue one minor carp about this:

    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

  • by workindev (607574) on Thursday February 21, 2008 @01:08PM (#22504214) Homepage

    First, can you provide a link that states this conclusively? Hydrazine propellant tanks are also made of steel, coated with titanium or other metals to prevent corrosion.

    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.
    Link [www.ctv.ca]: It was estimated to be carrying up to 450 kilograms of hazardous fuel called hydrazine, encased in a titanium tank.

    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.
  • by kels (9845) on Thursday February 21, 2008 @01:15PM (#22504310)
    Some better quality videos available directly from the Department of Defense [dodvclips.mil].
  • by wximagery95 (993253) on Thursday February 21, 2008 @02:04PM (#22505122)
    http://celestrak.com/events/Xichang-ASAT4.wmv [celestrak.com]

    Good model of the debris field caused by the China ASAT test. As you mention, "stuff" doesn't just fly everywhere.
  • by greyhueofdoubt (1159527) on Thursday February 21, 2008 @02:18PM (#22505360) Homepage Journal
    IWAHED (I work around hydrazine every day):

    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] ...Which is sturdy, but only meant to hold 485 PSIG. I'd say the wall thickness is probably between .060" to .080" to keep it light. I'm going to say that it might not be titanium, which is very sucseptible to hydrogen embrittlement.

    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
  • by Weaselmancer (533834) on Thursday February 21, 2008 @02:59PM (#22505964)

    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.

  • by nazg00l (699217) on Thursday February 21, 2008 @03:16PM (#22506186)
    Please note that the safe exposure limit refers to CONTINUOUS exposure, not to one-off contact. Acute toxicity levels are around 500 ppm, according to the same MSDS. Hell, benzene has exposure limits starting from around 1 ppm, and it was used as solvent for many years before being withdrawn due to cancerogenic - not short-term toxic - effects. Double hell, chlorine, the stuff used for disinfecting pool water, has EL of about 1 ppm, and when you smell chlorine bleach, you encounter dozens times more, and yet you live with perhaps watery eyes.
  • by bloobloo (957543) on Thursday February 21, 2008 @04:44PM (#22507476) Homepage
    Well fortunately this nerd is a chemical engineer who is working on an advanced metallurgy project so you're in luck. Aluminium melts at a cooler temperature than steel so that would be even more likely to go.

    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.

One small step for man, one giant stumble for mankind.

Working...