Just read at MSNBC that a large U.S. spy satellite will hit Earth by the end of February or early March.
Better keep our hard hats ready???

Here is the article:

http://www.msnbc.msn.com/id/22857051/

CNN also has the story: http://www.cnn.com/2008/TECH/space/01/26/d...e.ap/index.html
And these guys observe all Sats:
http://www.satobs.org/seesat/Jan-2008/index.html#204

Of course there's the obligatory sensational AP headline Disabled spy satellite threatens Earth that sounds like a 1950's sci-fi movie.

It's interesting that as they go through the "history" of satellite reentry they seem to have missed Cosmos 954 which left a swath of radioactive debris over northern Canada in 1978. Give it time and I'm sure that will become part of all these stories.

Cosmos 954 was the first thing I thought of as well, Dan. Correct me if I'm wrong, but humanity seems to have survived...I'm still trying to figure out how to get rid of you all!!!

Hi, according Calsky it seems to be satellite "USA 193 / NROL-21 (2006-057A)" that failed to work. The link shows the momentary estimated time and location of the fall.

Here are the images of US-193 in orbit.

Credit John Locker of Great Britain.
He says that the solar wings that are so visible with other sats are not visible in his images

He thinks they failed to deploy

image us-193-1 is during September at a range of 340km
image us-193-2 is a high elevation morning pass in December at ~300km

Click to view attachment

Click to view attachment

cheers

Breaking: US Military to Shoot Down USA-193 Spy Satellite



http://ap.google.com/article/ALeqM5h7aoM2i...uPxPNwD8UQ7CEO0

I just saw that too. I'm dying to know the physics involved; i.e. mass and velocity of the impactor and other critical elements. Probably too classified for that to ever be released.

I think they are more interested in destroying secret instruments on board that could fall into the wrong hands than protecting the public. The destruction will create debris left in space, just like destruction of the Chinese Satalite.

All that debris will probably end up reentering faster than the original satellite would.

I'm more interested in whether the missile will actually hit the satellite.

"I think they are more interested in destroying secret instruments on board that could fall into the wrong hands than protecting the public. The destruction will create debris left in space, just like destruction of the Chinese Satalite. "

NASA TV carried the press conference this afternoon, 1:30 central time. NASA Admin Griffin was one of the panalists to provide info-backup and support for the 2 military briefers. They spent most of the briefing and Q&A session debunking such double-nonsense as is embedded in this quote.

Point 1: While they may be lying -- some people automatically assume the military will lie about anything as a matter of mere convenience -- they were absolutely categorical about the planned destruction of the satellite being for safety reasons, not for eliminating classified technology information.

Point 2: The debris will not be "left in space". The chinese satellite was at some 450-500 miles altitude. The satellite will be at 130 miles altitude or lower when targeted. You can do about 1 orbit at 85 miles. Mercury early missions orbited at 90 miles where you can do about a day. 130 miles up youi may last a couple weeks or so if you're large and dense.

The debris from the chinese satellite will all (except for stuff that's like dust) be in orbit for decades, up to a century or more for big chunks. It will slowly decay, passing THROUGH the most used low orbit altitudes including where all manned missions fly except lunar missions. Note that if you intercept and fragment (the phrase "shoot down" is so wrong it's "bad astronomy" bad) a sat at exactly 500 miles altitude, essentially all the fragments end up on orbits passing through that 500 mile intercept point. Some will have higher apogees, some will have lower perigees, some end up in elliptical orbits that cross through 500 miles altitude.

When you intercept and fragment a satellite at 130 miles altitude, the fragments end up in orbits passing through 130 miles. Many will have perigees lower than that and re-enter on the next orbit or in a few days. Some will still have a 130 mile perigee but have a higher apogee. They'll still re-enter in a few days, as the drag at perigee is what counts, and their mass-per-surface-area is greatly reduced, so the drag slows them faster. Essentially all the debris will be below altitudes anything normally orbits at and essentially all will re-enter in a month.

What they were extremely specific and emphatic about, including Administrator Griffin, is the hazard involving the hydrazene tank. The tank is big. 40 inches (1 meter) diameter, and full of hydrazine -- frozen hydrazine that was never used up as the satellite failed completely the first day on orbit. There's a lot that IS known about re-entry, particularly after the post Columbia studies. (I've held a small titanium tank from Columbia in my hands -- we were inspecting it for possible internal defects (existing pre-disaster) that other shuttle tanks might have.) Griffin said: The tank WILL survive entry intact. It WILL be full of hydrazine. LITTLE hydrazine will be lost due to heating and boil-off during entry. The tank will not remain sealed during entry and impact: fuel lines will be ripped from other hardware during satellite breakup. (approximate quote) It will cannonball into the ground and sit there, either cracked or intact but leaking as the hydrazine melts and evaporates. With average wind conditions, an area typically the size of 2 football stadiums will be exposed to health-endangering or lethal amounts of hydrazine fumes. They said that if it were not for the specific risk due to the tank, they would not have decided to carry out this operation.

The intercept missile is an Aegis tactical ICBM (really IRBM) interceptor. It had to be modified to carry additional propellant to extend it's range up to the 130 mile (note.. I think they were using nautical miles) altitude. Software had to be specially modified to enable the intercept of this non-warhead like target in this non-warhead like trajectory. As a camoflauged test of an anti-sat system (which the moonbats will be screaming is the purpose of the operation), it's a hell of a lousy test.

Excellent summary Ed - the reporting has certainly been uniformly "Bad Astronomy" bad.

While this is definitely not a useful test of true anti satellite weaponry it is almost certainly a good test of the intercept guidance systems and I would be very surprised if this exercise was not being viewed by a very useful test by the military even though I do believe that the primary reason being given is genuine. Ignoring the pure military angle it is also a useful test of an if-all-else-fails mechanism for "safely" dealing with the de-orbit of potentially hazardous debris.

The one thing that surprises me about the whole situation is that this seems to imply that there is no self destruct capability on this satellite - I know nothing about spy sats but I would have expected them to have some self destruct capability and even a small charge located on or near the main fuel tank(s) would surely be a much more practical way of safing this thing than trying to hit it with a interceptor at a couple of km/sec.

For all we know, it might; I get the impression that they haven't been able to talk to it for quite some time, though. (Actually, after re-reading Ed's outstanding summary, they might have NEVER made contact with it).

On the other hand, most SVs seem to get boosted into "disposal" orbits at the end of their operational lifetimes or intentionally deorbited if they're low enough, so maybe there is no self-destruct system. Doesn't really seem that you'd want to carry explosives that might accidentally destroy the vehicle, either, and you really don't want to blow it up on-orbit & tick everyone off, esp. if you're trying to keep the entire thing very low-profile in the first place...

However, no idea how the Secret Squirrel crowd handles EOL with their toys.

I gather the spooks like to deorbit their birds, rather like the russians dispose of Progress supply barges.

The apparently semi informed discussion that I've seen on this bird is that is was in deep doo-doo when it was deployed from the delta 2 launch vehicle. <note.. this is not one of the big recon sats!.. not on a delta> The computer never booted or went into a locked up mode, safe modes never worked, apparently little or no panels etc deployed. Apparently was unresponsive and running out of power after only a few hours on orbit.

I was wondering why they'd design the thing with such a massive load of scary nasty hazmat in a re-entry survivable container, but I get it. In an optimum end-of-mission scenario, what little NH4 would be left would be vented, if not entirely consumed by the deorbit maneuver, and the whole thing goes splash somewhere remote.

Hopefully this will cause some fail-safe redesigns; if that tank was empty (or could confidently be expected to burn up), nobody'd be worried. As is, can't be doing last-minute mods to missiles & scrambling to get Navy ships into position in time to frag errant birds; that must've cost a fortune already, and the meter's stll running!

If this was launched on a Delta 2 it must have been more-or-less an "end of the line" item. In earlier programs such satellites have frequently been cobbled together from engineering test articles and similar that have been updated and flight rated. Might have some bearing on why it failed.

Highly doubtful

1. NRO hasn't used a west coast Delta II, there is no "end of the line" since there was no beginning
2. It could have been test or new type of spacecraft

That isn't a US practice. Adds more complexity and hazards to the spacecraft and reduces available mass

That is standard spacecraft design.

What do you think would happen to MSL or Phoenix if the upperstages didn't fire?

Ed,

Thanks for that thoughtful and knowledgeable analysis.

>>As a camouflaged test of an anti-sat system (which the moonbats will be screaming
>>is the purpose of the operation), it's a hell of a lousy test.

To me the more interesting question is whether success at what might be called a moderately challenging problem in orbital rendezvous tells us anything useful about the performance of systems intended to intercept unscheduled ballistic missiles.

Here is some amusing commentary on aspects of the story which are off-topic for umsf.com.

TTT

Understood. However, these vehicles are designed to land on Mars, so reentry into Earth's atmosphere, while still a risk, isn't part of the planned mission timeline. I don't know if there's a material that could be used to hold NH4 (nasty, corrosive stuff that it is) and also assuredly distintegrate at a safe altitude, but seems like it's something that should be thought about.

Titanium's wonderful stuff, but in this case it's too wonderful.

Strong enough to maintain pressure on orbit, but weak enough to break apart on re-entry is probably a specification overlap that doesn't exist I would imagine.

Doug

I was thinking of something with a lower melting point than Ti that might have sufficient structural integrity; an alloy? If the tank is mounted on the exterior surface of the spacecraft, then it could get a favorable burnthrough at the right altitude. The main issue is getting the hazmat out of the tank well before it hits the ground.

One other idea is coating the exterior of the tank with something that might act as an accelerant during reentry to promote a burnthrough, sort of an anti-heat shield.

One of the most formidable obstacles, though, remains finding a material that is both resistant to NH4 and light enough to be used for this application. Any metallurgists in the house?

EDIT: CNN now reporting that the interception may cost as much as US$60 million; sounds like they're low-balling it to me, hopefully not. Lots of equipment modifications required per the article, lots of engineering support...

The problem is that there is NO good replacement for hydrazine.

Space storable, non-cryogenic propellants are pretty much all nasty. About the only one that isn't nasty doubled is CONCENTRATED hydrogen peroxide.
You can have a dual propellant system.. another hydrazine and an oxidizer like nitrogen tetroxide <gak! gag! croak!>... less total nasty stuff but twice as complicated a propulsion system.

I don't know anything that has a decent "bounce per ounce" that isn't nasty.

Well, it's good that the US has the capability and will expend the costs to mitigate the hydrazine hazard, particularly since it can fall on other countries as well as the US. It is nasty stuff. I commiserate with the Kazakhstan folks downrange of Baikonur when a Proton is having a bad day.

BTW, nprev, NH4 is ammonium, usually ionized, and in solution or compound. Not quite as nasty without another N.

Ahh, I'm chemically illiterate...I meant N2H4, of course, thanks, mchan!

Yeah, Ed, I'm not advocating trying to do without hydrazine; can't see any other practical alternatives either. What's needed is a way to dump the stuff safely from a dead bird, which implies a passive method, presumably triggered by reentry heating. Perhaps high-threshold (500 deg C)/high-volume bimetallic dump valves hooked directly to the tank, similar to what I proposed for on-orbit dead booster venting awhile back?

If the intercept is successful in mitigating the hazard material problem, then it could be used for future similar cases without incurring development costs of an on-board hazard reduction mechanism and the associated mass penalty. The incremental cost of the intercept would be expended only if the contingency actually occurred rather than adding the cost to the spacecraft in anticipation of the contingency.

The intercept option would not work for hazard from a re-entry immediately following a late launch failure. Not too bad if the impact zone is over water, but very crappy if over land.

I don't know if the US Navy, nor the DoD itself, would be happy about maintaining the Lake Erie and its support ships in a unique hardware & software configuration ready for extremely infrequent use in this way, though. The missile mods are one thing, but from what I've read the ships themselves will have to be de-modified in order to reestablish their core mission capabilities.

However, I guess they could conceivably refine the whole process into a portfolio of quick-reaction kit mods after the scramble to get US-193 handled is over & there's time to work out the logistics.

There is no need for this. This situation is rare. It is not worth the effort to mitigate this nonproblem

...NRO might see it differently, Jim; bet that they're just loving all this wonderful publicity...

Doubtful. Adding more penetrations to a tank that could jeopardize a mission would be frowned upon

I wouldn't advocate adding more penetrations to a tank; understand how difficult it can be to design those things to hold pressure & pass the structural integrity requirements. (The bimetallic valves I was thinking about would be on the main feed line before the pump & shut-off valve, making it effectively one penetration topologically).

I would, however, really like to know if there's some sort of substance out there that's safe to fly to coat the tanks with, something that might promote intense spot-heating during reentry. I don't know; maybe a layer of magnesium coated with plastic to keep the O2 out pre-launch, or even just a few strategically-placed patches of same?

One other thing about such "vent-patches" is that they might blow under some circumstances during a launch failure & dump the crap before it's anywhere close enough to habitable areas to cause problems.

1. It is still a propulsion system penetrations. Also Range safety wouldn't like like them since there is no insight or intentional control of them

2. Since the weight and range safety issues.

Some questions:

The intention is to break the space craft up in to many smaller pieces, increasing the likelihood of most of it disintegrating upon re-entry. Will this debris spread out after the impact producing dozens or possibly hundreds of re-entry "events" spread out over days maybe weeks?

I'm a bit amazed that anti-satellite missiles can be fired to such altitudes from the ground (sea) up. I remember that the US Air Force had anti-satellite missiles but these were fired from an F-15 fighter jet flying at maximum altitude...

Firing a missile to 200 km altitude isn't that difficult (after all the Germans did it back in 1942). Launching from an aircraft at 50,000 feet does help, but the reason ASAT was aircraft-borne was mainly for the flexibility and quick-reaction capability. An aircraft can launch almost anywhere in the wrld and in any direction.

Maybe...but the prime intent per Ed's analysis of the intercept is to rupture that full hydrazine tank on-orbit so that it's not a hazard after impact.

Do we have any idea what the debris field will be like and how long it will persist in orbit? The satellite is almost out of orbit anyway but the energy of a missile strike will surely boost the orbit of a lot of the debris?

http://spaceweather.com/ (19. Feb) reports that rumor has it that the US Navy may make its first attempt to hit USA 193 this Wednesday evening as the satellite passes over the Pacific Ocean. Because of Ted Molczan has drawn attention to a NOTAM issued by the US Government that might point to a possible ASAT attempt on USA 193 on Feb 21, between 2:30 and 5:00 UTC.

If they hit exactly the tank with the hydrazine, at that great combined speed, I would think the missile (without a warhead) penetrates the tank and maybe other parts entirely without larger impact on the orbit of the rest of the satellite.

As we all know it's all about mass and velocity. If that impactor arcs up and strikes the satellite at a high velocity opposite to the direction of travel then it will indeed impact the orbit of the doomed satellite. I suspect that this is part of the plan, or if not it has been calculated for. Not knowing the impactor mass and it's expected impact velocity it would be difficult for us to even pencil it out here, but the orbital effect will be significant (with a small number on the mass side of the equation, but a very large multiplier on the velocity side.)

Wondering why Michael Griffin is so prominent in all these public statements. Hey - I have an idea. Maybe he's thinking this offers a way to avoid HST's eventual reentry violating NASA debris footprint rules, and a lot cheaper than developing a (probably still one-off at that point) robotic module for controlled deorbit.

The impactor's velocity is not really part of the "equation", it could be zero. The bulk of the energy is from the satellite. The velocity differences are on the order of several km/sec.
The impactor just has to get in the path of the satellite at the right time. Sort of like throwing up a baseball glove to knock down a fly ball.

I get your point, but come on now there is no such thing as a zero velocity except with respect to another body. If the velocity is zero with respect to the satellite then there will be no damage (and no impact for that matter). Even if the impactor is moving in the same direction of travel, albeit slower, its momentum must be factored in to the final momentum of the system after the impact. And in every instance I can imagine, the result will be greater decay in the orbit of the satellite and it's fragments.

Didn't say with respect to the satellite , I was referring with respect to the earth (basically hovering)

http://www.space.com/news/080219-satellite-shootdown.html

The collision between the fired missile and the satellite would not only break the massive hunk of metal into pieces but would also speed up its tumble through Earth's atmosphere.

"If you want to bring something down, you slow it down. You apply a force on it which results in it being slowed down and decrease in its orbit," Carrico told SPACE.com. "Right at that point where they want to engage [the satellite] is at the edge of the atmosphere, so you're bringing it down faster."


I believe that was the point I was trying to make above.

Time and location of this first shot down attempt is well chosen. There's a graphic here (text in German) that show roughly the orbit(s) (in orange) after the possible hit. The most part of the following two orbits are over the sea and the rest good enough for military secrets. The large green colored circle shows the area where the satellite (or debris) can be seen from the ground.

The force that is going to bring down the fragments is drag, not the impact. The fragments have a lower ballistic coefficent

I believe the space.com story doesn't mean the impact will bring down the fragments, it will lower the perigee so it runs into the denser atmosphere much sooner. Hence the "speed up its tumble through Earth's atmosphere". It's inevitable the fragments will be robbed of some energy by the impact in addition to increased drag due to fragmentation you mention.

I know this is a stupid question and I'm sure I should know the answer myself but I'm having trouble getting my head around it. Lower orbits have a higher orbital velocity than higher orbits so if this exercise is (as seems likely) going to be a head on collision then it will slow down the whole satellite and probably seriously slow down quite a lot of the debris. Ignoring drag which I fully accept will act much more effectively on the resulting impact compromised debris why doesn't this deceleration cause the whole thing to end up in a higher orbit?

Because this event will take away from the total energy of the satellite. Higher orbits have higher total angular momentum, but a lower kinetic energy. If you very gradually take away energy from an orbiting satellite (say in a circular orbit via air drag), it will actually be speeding up a bit because the orbit will effectively remain circular and just the radius will decrease. Overall, it still loses energy because the gravitational potential energy drops off more rapidly than the kinetic energy is increasing.

It's a bit counterintuitive, but true. A lower orbit is a higher speed one, yet one with a lower angular momentum. In our solar system, the majority of the energy is carried by the outer planets, not inner ones.