Whoa! A close shave next year.

[EtherealN]

As a last resort, I can agree.

 

As for a second blast, my guess would be that figuring out what it's effect would be would be pretty much impossible - before the first blast you are dealing with a known quantity, but if it does break apart you need to do a LOT of calculations to figure out what you need to do. Basically a case of wanting to be sure you're not making it worse.

 

I also expect that the scenario might be different depending on the size and make of the asteroid. I'm also worried about one aspect which is whether we can fully figure out the effects of a blast for a newly discovered asteroid of unknown (or partially unknown) composition - if it "only" threatens to flatten New York a month down the line, it might be better to let it do exactly that (1 month should be time enough to get the people out, though property damage would of course be, excuse the pun, astronomical) than hit it and find out it (or significant parts of it) will instead slam some other place where you have no evacuation plans ready.

 

I don't have time to read the article right now, so perhaps this was already discussed in it (apologies in that case). To a great extent I expect this to depend a whole lot on exactly how much warning is received, how much information on the rock is available, and what the interception window is for the nuke(s). If our weapons and delivery systems are such that we can strike it when it's 2 months out and have a window for secondary strikes afterwards to take care of any spall, that's one thing. If our window to hit them is when they're just days out... Again though, I'll have to read the article later, so perhaps this has already been answered.

[Speed]

As a last resort, I can agree.

 

As for a second blast, my guess would be that figuring out what it's effect would be would be pretty much impossible - before the first blast you are dealing with a known quantity, but if it does break apart you need to do a LOT of calculations to figure out what you need to do. Basically a case of wanting to be sure you're not making it worse.

 

Keep in mind this is space. If you deflect an asteroid in any direction, odds are very, very high that the new direction does not intersect Earth, at least not for a very long time. You only need to give the rocks a push, and direction doesn't matter very much, in fact. With every push, you basically re-roll your thousands to one odds of impacting the earth. So, because the Earth is such an incredibly tiny target, you for the most part don't need to know what the effects will be beforehand. If you push a rock in a random direction with a significant velocity, it will most likely no longer pose a danger. I would think after a couple nukes, the amount of the original asteroid that will still hit earth ought to be down to almost nothing.

 

The problem is, I don't understand orbital mechanics very much. Never had any formal training in them. But it seems pretty clear to me- after the first nuke, anything left that would still hit Earth in this orbit is going to be travelling the same path as the original object. So all you need to do is keep nuking along the original orbit over a space of a few seconds, and there should be almost nothing left to hit Earth on this orbit. And, since space is so damned big, there will probably be nothing significant to hit Earth on future orbits, either.

 

And also, as this is an approach for small objects, what you've done, at the very worse, might be to transform a rock that would have hit the ocean, caused a massive (hundreds of meters) tsunami and a few years of global cooling, into a distributed string of Tunguska-style impacts that, most likely, wouldn't cause all that much damage. A swarm of smaller objects, too small to make it all the way to the ground, isn't that horrible. The classified military satellites the US and Russia put up to detect nuclear tests and explosions supposedly see kiloton-class asteroid explosions quite frequently. Scientists have been itching to get their hands on the data for years, but it's very sensitive information. The point is, small stuff ain't so bad, assuming it's truly small, like 10m or less. We could most likely live with a few Tunguska-sized impacts just fine too. What's really horrible is when a big object, like >250 meters across, makes it to the ground at orbital velocities.

Edited March 12, 2012 by Speed

[EtherealN]

But the target size thing depends a lot on when the weapon can be delivered. And expecting a uniform change in momentum is a bit on the enthusiastic side, imo - if it remains a single object, sure. If it doesn't - if it is a "rubble pile" - this might be different.

 

And of course, what if you changed it from a Tunguska over Paris to a string of impactors that walk across China? Also, assuming that they'll be too small to reach the ground is yet another thing I have a hard time understanding.

 

 

Being "small" does not mean it won't impact. The key factor in whether it'll burn/skyburst is what it's made of. Small things reach ground all the time.

 

And what would you prefer - a single 100 meter impactor north of Norilks, or a long chain of 10 meter impactors all over europe?

[Speed]

But the target size thing depends a lot on when the weapon can be delivered. And expecting a uniform change in momentum is a bit on the enthusiastic side, imo - if it remains a single object, sure. If it doesn't - if it is a "rubble pile" - this might be different.

 

The uniformity of the momentum change doesn't matter so much, not when all it takes is ANY momentum change of sufficient magnitude and the thing will miss.

 

And of course, what if you changed it from a Tunguska over Paris to a string of impactors that walk across China? Also, assuming that they'll be too small to reach the ground is yet another thing I have a hard time understanding.

 

 

There are a few factors at play here.

 

The first is that a typical asteroid impact velocity is like 15 to 20 km/s. So it crosses into the densest portions of the atmosphere in a matter of seconds. It’s like hitting a brick wall. More scientifically, what happens is that a TREMENDOUSLY high pressure builds up on the front surface of the object, while the back surface is in a near vacuum, as the air can’t rush in fast enough. This pressure differential is enough force to shatter small asteroids. Obviously, the more rubble-pile-like an asteroid is, the less harzardous it is- a solid nickel-iron object will have an easier time surviving all the way to the ground, or low enough to cause a damaging airburst, than a rubble pile!!!

 

So, when the asteroid shatters, suddenly, the surface area increases to many millions of times greater than what it was before. Now, since the amount of energy shed to earth’s atmosphere is proportional to the surface area of the object being impacted by Earth’s atmosphere, and the density of earth’s atmosphere, in a fraction of a second, all of the objects orbital energy is converted into a large, super-heated volume of air, which explosively expands.

 

Now, the size of an object is important in two ways. The first is that, the bigger it is, the more resistant it is to breaking up, and the more likely it will make it all the way to the ground. The second factor is that the bigger it is, the less surface area it has per mass, as surface area is proportional to radius squared, while mass is proportional to radius cubed.

 

Now, usually, when an object explodes, some little chunks will usually still survive the explosion to make it to the ground intact. However, they make it to the ground at a tiny fraction of their orbital velocity, and very often, they make it to the ground at terminal velocity. Maybe, 500 km/h. These are only dangerous if they hit you on the head. Actual objects traveling at 20km/s carry the kinetic energy of nearly fifty times their weight in TNT. That picture of the destruction caused to the car, that was caused by a rock moving at terminal velocity. If it was an object moving at actual orbital velocity, it would have blown up the whole house (and probably the neighbors, too- that rock looks to be several kilograms).

 

Now, iron objects, yes, they can make it to the ground at orbital velocities a lot easier than rocky objects, but keep in mind, they are still subject to the fact that they have small masses and big surface areas. And the little ones still explode- haven’t you ever watched Meteorite Men? :) Even solid nickel-iron isn't much of a match for Earth's atmosphere at 20km/s.

 

And of course, I am still simplifying things a bit. Objects can and do make it to the ground with intermediate velocities. Such as whatever it was that hit South America a few years back and made that big pit. But they are not very destructive or dangerous. They don’t have to hit you on the head, they need to land right beside you, or hit you on the head ;)

 

Being "small" does not mean it won't impact. The key factor in whether it'll burn/skyburst is what it's made of. Small things reach ground all the time.

 

And what would you prefer - a single 100 meter impactor north of Norilks, or a long chain of 10 meter impactors all over europe?

As I understand it, 10 meter sized objects never, or almost never, survive to a low enough altitude for their airburst to cause any damage. They also only carry as much energy as a couple Hiroshima bombs. The object they detected a few years back right before it impacted, if I remember correctly, was a 5 meter wide object, and I was under the impression that no warning was issued because it was too small to be dangerous.

 

Also, based on the past history of our nuke monitoring satellites detecting, yearly, at least kiloton-class asteroid explosions, shows that these little objects hit the earth all the time, and yet we have no historical records of anything in this size class making it to the ground, or near the ground, with any significant destructive force left. The only historical record we DO have is of the Tunguska impactor, and that was like 30 meters wide, minimum, I think.

Edited March 12, 2012 by Speed

[EtherealN]

No time to deal with the whole thing (sorry), but the Kenya impactor was indeed less than 5 meters in diameter. This was however still enough to yield 2 kilotons if I remember right. And again, that's one object.

 

Warnings were not issued to the local people because the impact site was known and there was no-one there. But the event had made it's way all the way up to presidential level as well as international dissemination to other heads of states and relevant agencies to make sure no-one misunderstood the object as a nuke.

 

If this one had been heading for New York, Paris or Moscow, you bet there would have been alerts. I know I'd prefer to know beforehand if I'm about to have a multiple kiloton explosion over my head - and of course, it wasn't known to be an airburster until after the fact. Again - small rocks make landfall all the time.

 

As for "only [...] a couple hiroshima bombs", a single Hiroshima bomb is still more than 50 thousand dead if it impacts the wrong place. Spray europe with that kind of stuff and there will be a lot more.

 

Again though, your historical records are guesses. We've never nuked an asteroid. You can't bring experience into account for something that has never happened, and nuking a 50 meter object of unknown composition is not known territory - and serial-nuking it even less so.

 

If the composition of the object is known and we know very well what's needed and what it'll do, it's fine as a last resort. But if there is any ambiguity and sufficient warning is had (or if the attempt has to be made very late in the trajectory due to the delivery system), accepting material destruction might be preferable to playing with unknowns.

[Speed]

Also, I once had someone ask me why the Space Shuttle or Soyuz doesn't explode, and how space junk can get to the ground. The answer is two-fold:

Stuff in orbit is moving much more slowly (8-9km/s)

MUCH MORE IMPORTANTLY:

The stuff in orbit always comes in at a very shallow angle. So stuff in orbit comes in gradually, shedding most of its orbital energy slowly, at high altitudes, over several minutes. Asteroids almost always come in at MUCH steeper angles, they dive into the dense portions of at atmosphere in a matter of seconds.

[Speed]

No time to deal with the whole thing (sorry), but the Kenya impactor was indeed less than 5 meters in diameter. This was however still enough to yield 2 kilotons if I remember right. And again, that's one object.

 

Warnings were not issued to the local people because the impact site was known and there was no-one there. But the event had made it's way all the way up to presidential level as well as international dissemination to other heads of states and relevant agencies to make sure no-one misunderstood the object as a nuke.

 

If this one had been heading for New York, Paris or Moscow, you bet there would have been alerts. I know I'd prefer to know beforehand if I'm about to have a multiple kiloton explosion over my head - and of course, it wasn't known to be an airburster until after the fact. Again - small rocks make landfall all the time.

 

As for "only [...] a couple hiroshima bombs", a single Hiroshima bomb is still more than 50 thousand dead if it impacts the wrong place. Spray europe with that kind of stuff and there will be a lot more.

 

Again though, your historical records are guesses. We've never nuked an asteroid. You can't bring experience into account for something that has never happened, and nuking a 50 meter object of unknown composition is not known territory - and serial-nuking it even less so.

 

If the composition of the object is known and we know very well what's needed and what it'll do, it's fine as a last resort. But if there is any ambiguity and sufficient warning is had (or if the attempt has to be made very late in the trajectory due to the delivery system), accepting material destruction might be preferable to playing with unknowns.

 

You need to read the whole thing when you get a chance, and before you reply any more. Sorry, but you do. You still saying things that are blatantly wrong, that you would understand if you read it.

[EtherealN]

You need to read the whole thing when you get a chance, and before you reply any more.

 

Yeah, I'll take that advice. :)

[Speed]

One thing I didn't mention, but is implicit, in that big post I made explaining the non-hazards of small objects, is that explosion altitude is a function of object size, too. The kiloton class explosions happen at like 100,000 feet. How is a 50 kiloton, non-nuclear explosion occurring 20 miles away supposed to be dangerous again? Maybe you'll have to replace the glass in your windows or suffer some hearing loss, I guess. If you're really lucky, a big chunk of the debris will survive and hit your house's roof a few minutes after the explosion, cold to the touch after falling through the sub-zero stratosphere for a few minutes. Then you will be able to sell the rock on Ebay for $100,000, and use $10,000 of that to repair your roof. If you get really, really lucky, it will hit something mobile like your car, and you will be able to sell the car on Ebay for $100,000 too!

Edited March 12, 2012 by Speed

[Pilotasso]

I just droped by to apologise for the tone of my messages yesterday. I have been inconsiderate torwards the data you provided and lashed out frustration from my RL here.

 

 

Sorry. :)

 

I think we've all been there. In fact, some of my replies to you were far too hostile and I had to edit them down, and even after that, I still ended up feeling like I had been a jerk.

 

I hear ya. Its ok now, ta? :)

 

Edited March 12, 2012 by Pilotasso

[Speed]

If this one had been heading for New York, Paris or Moscow, you bet there would have been alerts. I know I'd prefer to know beforehand if I'm about to have a multiple kiloton explosion over my head - and of course, it wasn't known to be an airburster until after the fact. Again - small rocks make landfall all the time.

 

BEEP! BEEP! BEEP! BEEP! BEEEEEEEEEEEP!

...

SCIENTISTS AT THE JET PROPULSION LABRATORY IN PASADENA CALIFORNIA HAVE DISCOVERED A SMALL ASTERIOD ON AN IMMINENT COLLISION COURSE WITH THE LA BASIN. THE OBJECT IS EXPECTED TO EXPLODE OVER THE LOS ANGELES AREA IN 2 HOURS WITH THE EXPLOSIVE FORCE OF 15 KILOTONS OF TNT.

 

***Several screams erupt. Everyone starts running for the door, frantically calling the school to get their kids, etc. They miss the remainder of the message:***

 

HOWEVER, THE EXPLOSION IS EXPECTED TO OCCUR BETWEEN 75,000 TO 150,000 FEET, AND WILL NOT BE A DANGER TO THE PUBLIC, AS THESE EVENTS OCCUR QUITE FREQUENTLY AND NO ONE IN RECORDED HISTORY HAS EVER BEEN KILLED BY AN ASTEROID. HOWEVER, PLEASE STAY INDOORS AT A LOWER FLOOR OF YOUR HOUSE FOR SEVERAL MINUTES AFTER THE EXPLOSION, AS SCIENTIST EXPECT ROCKY DEBRIS WILL IMPACT THE GROUND ONE TO THREE MINUTES AFTER THE EXPLOSION AT TERMINAL AIR VELOCITIES. AFTER FIVE MINUTES, YOU MAY COME OUTSIDE AND SEE IF YOU ARE LUCKY AND HAVE ANY SPACE ROCKS IN YOUR YARD THAT YOU CAN SELL ON EBAY.

...

BEEP! BEEP! BEEEEEEEEP!!!!

 

***In the background, frantic screams can be heard. Gunfire erupts as someone shoots another for their car so they can flee town. In the distance, more gunfire, squeeling brakes, and crunches of glass and metal can be heard.***

Edited March 12, 2012 by Speed

[EtherealN]

4.6. :)

 

But aside from that, funny :D

[Speed]

Here's an interesting article on the Peruvian impact I perviously mentioned (I called it the "south american" impact:

http://en.wikipedia.org/wiki/Carancas_impact_event

 

It was probably a 3 meter class object, and it didn't fully explode- instead, it was able to aerobrake way most of its energy- perhaps it came in more slowly, and/or at an angle. Wikipedia thinks the high altitude of the impact site was a contributing factor:

Reported details about the event, such as water boiling in the muddy crater for ten minutes from the heat of the impact, presented a problem for experts. Because the impact site is at a high altitude of more than 3,800 m (12,467 ft), the meteoroid may not have been slowed down as much as it ordinarily would have been by passage through the Earth’s denser lower atmosphere, and kinetic energy at impact may have been unusually high for a terrestrial impact of an object of this size and mass. Most larger meteorites are cold in their bulk mass when they land on Earth, since their heated outer layers ablate from the objects before impacting.[13] It was later confirmed that the meteorite had high degrees of iron and possessed magnetic properties common to similar metallic objects, which contributed to its capacity to retain heat during atmospheric entry.[20]

 

This is what it did to the ground:

 

That could easily kill a few folks if it occurred in a metropolitan area, but far more people would die in a the panic caused by a last-minute public warning. Now, if you knew about it a long time beforehand, time enough to get a sane response from the public, things might be different, but the fact is, these objects are too numerous and too faint to really be tracked right now. There's not many scopes out there dedicated to finding and tracking asteroids. AND it's rare that these things cause any significant danger to people on the ground in the first place.

 

So with the smaller objects, even if they don't explode, their surface area to mass ratio is so high that that will not hit the ground at orbital velocities. MAYBE supersonic velocities, and most likely, in little bits and pieces travelling at terminal velocity.

 

Anyway, I've gotten the chance to see a few decently big objects enter the atmosphere over my years of sky watching. Interestingly enough, both came in at shallow angles to Earth's atmosphere, so I gotta wonder if they might have just been space junk. In October 2010, I even heard a series of sonic booms following a one object that was perhaps as bright as the full moon (who knows, maybe brighter), and crossed the sky in about six or seven seconds before finally breaking up completely. It looked like a white-green arc welder arc, left a glowing tail, and shed several chunks that glowed orange and trailed off at an angle, and then faded out itself in a little burst of orange. About 2-3 minutes later, a series of booms that lasted 2-3 seconds could be heard, sounding like distant fireworks. I gotta think SOMETHING made it to the ground from that one.

 

These little things I'm seeing though are probably only a foot or two across though, and are probably doing all this at like 200,000-300,000 feet, however, the sound travel time for the sonic booms would suggest a lower altitude. That said, I did not actually time how long it took for the sound to reach me, so I'd say my time estimate was off.

 

The other big one I saw was, coincidentally, during the Leonid meteor storm of 2001, and I say coincidentally because it was not a Leonid meteor itself. Similar in appearance and behavior (a little bit whiter, intensely bright, little orange chunks/sparks breaking off, faded into orange) to what I described above, except a bit fainter, and no sonic booms were heard.

Edited March 12, 2012 by Speed

[Speed]

I hear ya. Its ok now, ta? :)

 

Yea, more than fine by me. I was pretty pissed at myself when I thought I had burned bridges with you, as you're pretty active in the community and a good guy- though you did shootdown Mojeaux in my squad a few times in a single day on the 104th server, prompting him to call you "pilotasshole", but I won't hold that against you :P. "Ta" though- who the hell are you, Viper or something? :D

 

Also, this is the first thing I saw when I looked at your post:

 

Anyway, enough of this happy-touchy-feely care-bear crap. Any more and I think I'm gonna be sick :puke:

:D

[Pilotasso]

LMAO! :D

[RIPTIDE]

Can I have a cuddle too Pilotasso?

[Pilotasso]

Sure but lemme disguise from lion back to hedgehog first. ;)

[159th_Viper]

Porcupine is cuddlier :P

 

[Speed]

Porcupine is cuddlier :P

 

 

Ouch, that's gonna be one dead kitty.

 

Anyway, on topic, here's a fun little site to keep tabs on:

http://neo.jpl.nasa.gov/risk/

[636_Castle]

How about the near miss asteroid 2012 EG5 that will be making an appearance on April 2nd?

 

EG5 was discovered within the last 24 hours, and is expected to pass around 0.7 LD from Earth (in the 100,000 mile range). NASA was expected to make an announcement regarding the asteroid on Thursday, but I don't think they did.

 

To make matters worse, the asteroid is currently condition code 9, meaning it's trajectory path is very unpredictable. (Condition codes are ranged from 0 to 9, with 0 being a good flight path trajectory, and 9 being uncertain).

 

The asteroid is 65 meters wide.

 

(Video animation starts at 24 seconds)

 

Lt0XPVu22ow

Edited March 16, 2012 by 636_Castle

[Speed]

2012 EG5? According to the JPL, it's only got a like a 1 in 2 million chance to hit us in the next 100 years, with the only "dangerous" pass being in 2048- but maybe this object is so new the table hasn't been fully filled in?

 

http://neo.jpl.nasa.gov/risk/2012eg5.html

[hassata]

YN_pCabinfk

[Speed]

A minivan-sized asteroid apparently exploded over central California earlier this week, releasing about 5 kilotons of TNT of explosive power:

 

http://www.space.com/15426-daytime-fireball-minivan-size-space-rock.html

 

Like I said though, there's nothing to worry about with the small objects- they hit us all the time, and they always explode at very high altitude.

Edited April 25, 2012 by Speed