Tunguska 1908

[Steve_D_Ippolito]

June 30th (June 17th Old Style) is the 100th anniversary of the Tunguska event, now believed to be a meteor disintegrating in the atmosphere with multi-megaton force (for comparison, Hiroshima and Nagasaki were 0.02 megatons (or so) apiece). Middle range estimates are that it blew up with a force of 15 megatons.

Tunguska is a river, or actually a group of rivers, in Siberia. There were eyewitness accounts, however all that got destroyed were a very large number of trees. If, however, the earth had rotated an additional four hours and 47 minutes at the time, St. Petersburg, which was then the capital of Russia (and the residence of one Alisa Rosenbaum) would have been suddenly destroyed. In 1908 no one had any concept of atom bombs, and aerial bombardment was unknown to most if not all. The airplane itself was less than five years old. Aside from the fact that this event would have killed Ayn Rand at the age of three, it’s interesting to speculate what would have happened in world history if the capital of a major power had suddenly ceased to exist, for reasons no one could have figured out at the time–it would have seemed like a (rather disastrous) miracle. Also would Russians in the hinterland, a notoriously superstitious/religious lot, have decided that God was mad at the Tsar or at Mother Russia? Or would they have come to some totally different conclusion? What would the other powers in Europe have done in response to the sudden decapitation of the Russian empire? Would the empire have dissolved in civil war as the provinces on the periphery (Finland, Poland, the Caucasus, Central Asia, the Maritimes) tried to break away?

Another interesting aspect is that meteor impact is (depending on the size of the meteor) a catastrophe that could wipe the entire human race out of existence. It would make Katrina, earthquakes, and tsunamis look like nothing. Yet we can potentially do something to prevent it with enough warning. (Hooray for man!) The Yellowstone supervolcano could cause real problems any time in the next million years, and if it were to happen sometime in the near future we would be f***ed, not to put too fine a point on it. But a meteor, we could divert if we had sufficient warning.

Thoughts?

[DavidV]

But a meteor, we could divert if we had sufficient warning.

Thoughts?

Everything that I’ve read suggests that we are unlikely to detect a meteor in time, and even if we did, there is little we can do. Nukes are not very effective in space - no medium for the shockwave.

[ruveyn_ben_yosef]

The Yellowstone supervolcano could cause real problems any time in the next million years, and if it were to happen sometime in the near future we would be f***ed, not to put too fine a point on it. But a meteor, we could divert if we had sufficient warning.

Thoughts?

Getting hit with an asteroid or a meteor a mile across could be an extinction level event. The meteor that blasted out the Meteor Crater in Arizona (you might have seen it in -Star Man-) was only a hundred feet in diameter or thereabouts. The problem is spotting these bodies sufficiently far out and applying enough force to divert it slightly (it need not be destroyed, just diverted).

If we do get hit with a meteor (or asteroid) a kilometer in diameter the impact is sufficient to destroy civilization. It would be possible for the human race to survive if it could go underground with sufficient food and energy stored to wait out the dark period that would follow the impact (it could be several years of darkness). There is a .7 probability the body would hit the ocean and the resulting tsunami would wipe out not only coastal cities, but go inland several hundred miles. It would be necessary to hunker down somewhere in the middle of the continent and in relatively high ground (say the Rocky Mountains). Because of the crop failure that would follow the impact most of the 6 billion or more humans would die. With sufficient preparation, several millions could survive. If the colliding body is several miles across then do the following: Stand with your legs apart, bend down, put your head between you legs and kiss your ass goodbye. The only good news in that case is that it is big enough to see and we could perhaps divert it a bit.

The usual Hollywood fantasy is to use a nuke. Here is the problem with that. Many asteroids are accretion bodies. That is they are essential rubble piles held together with weak gravitation. If the body is large enough a nuclear blast would just break it into several big pieces, each of which can do vast damage to the planet and to civilization. The better way would be to mount low thrust rocks on the body far enough out to divert it. But, as I pointed out, the difficulty is seeing bodies big enough to destroy civilization (on impact) but small enough not to be seen for a sufficient time to get a fix on the orbit. If you see a small body one night and then don’t see it again for months and see it yet again, how does one know it is the same body? One needs at least three good fixes to get a decent estimate of the orbit. And even so, the orbits of small bodies can be perturbed by gravitational interaction with larger bodies. So if the Killer Meteor flies through the asteroid belt, its orbit (even if known) is likely to be perturbed. That cuts both ways. A meteor that, if unperturbed, would not hit us, is perturbed just so, it could it us. Then a meteor we think would hit us might be diverted by gravitational interaction in the asteroid belt, but we could not assume that so we would have to be prepared.

It is obvious that the preparations for an extinction level event would strain the material and social resources of all the nations of the world. And choosing the survivors (assuming there could be survivors) would be the largest act of triage in the history of human kind. Say only ten million could be placed in sites all over the world. Which ten million out of six billion (or more) will be the lucky ones? And will they be lucky? The psychological impact of coming out of hiding after two years underground might make a dent.

Here is the little good news I can think of. Building telescopes (both earth based and orbital) is relatively inexpensive. Which means private investment could produce sufficient number of Watchmen in the Night to spot many earth orbit crossers we don’t yet know about. This could be done without government. However if we are going to get a hit, it would probably take the kind of resources that only governments can steal to give millions a chance to survive. It would be possible for sufficiently rich folks to prepare there own hide hole for themselves, family, friends and associates. This would amount to thousands of survivors, rather than millions. The human race need not go extinct, but it is good bye to civilization if only thousands survive. Why? Because a critical mass of skills sets would be required to rebuild civilization in say two to three generations. If only a few thousand survive, as did the human race did when the super volcano Toba erupted then it would take thousands of years to rebuild. It takes a culture (even one with warts) to provide the matrix within which knowledge and technique could be retained. So even in an “optimistic” scenario, the human race survives but civilization is pretty well wrecked.

Our only real long run chance is emigration off earth. Perhaps I will write a piece showing why that at best is a gloomy prospect given our current level of propulsion technology. In days of yore humans got from the Asian mainland to Australia on crude rafts. But there was an Australia to go to. Unfortunately there is not another planet in the Goldilocks Zone for us to paddle our crude rocket ships to.

Here is the long and skinny: We are aboard the Titanic and there are not enough lifeboats. The ship is sinkable and there are lots of icebergs out there.

PS: The bad guy of the Tunguska blast never made it earth. Whatever it was disintegrated before contact with the surface and it was a blast wave that did the damage. No crater and no pieces have ever been found. If that baby had leveled London or New York we would still be talking about it.

ruveyn

[D_kian]

The usual Hollywood fantasy is to use a nuke. Here is the problem with that. Many asteroids are accretion bodies. That is they are essential rubble piles held together with weak gravitation. If the body is large enough a nuclear blast would just break it into several big pieces, each of which can do vast damage to the planet and to civilization.

It depends on the kind of asteroid or comet. A nuke can prove effective against the more solid bodies. one problem is we know little about asteroids and comets. They’re small and far away, thus making telescopic observations of limited value only. I think there has been one probe launched to study an asteroid, though. And an informal group within NASA is planning for a manned mission to one.

Still, there are several propposed alternatives, from nukes to conventional explosives, to solar sails, to rocket engines, to mass drivers. It would be good to visit several asteroids and try each and see how they do.

PS: The bad guy of the Tunguska blast never made it earth. Whatever it was disintegrated before contact with the surface and it was a blast wave that did the damage. No crater and no pieces have ever been found. If that baby had leveled London or New York we would still be talking about it.

Check out last month’s Scientific American. There’s an article about Tunguska. An Italian team appears to have found an impact crater close to ground zero. It seems the body, be it an asteroid or comet, did break up and release most of the impact energy while in the atmosphere, but pieces may have impacted anyway. One of the alrger pieces apparently made a crater that now is filled with water.

The area where it hit was completely or almost completely uninhabited, therefore the event was of little note. If a much smaller body had merely damaged a city, any city, we’d still be talking about it. Better yet, we may be doing something about it.

[Matus1976]

The threat posed by asteroid impacts, and indeed Caldera eruptions (like Yellowstone) are very real. I am a staff member of the Lifeboat Foundation, which is an organization whose explicit goal is to identify all the existential threats that humanity faces and work toward implementing reasonable strategies to mitigate those threats. Much of the current emphasis is on the possible consequences of technology like synthetic life, artificial intelligence, and nanotechnology. We are not a luddite organization however, and our advisory board includes Ray Kurzweil and Aubrey De Grey, Kurzwiel is one of our largest donors. But natural existential threats are extremely disconcerting and the closest humanity has ever come to extinction was the last super volcano blast in Toba, about 70,000 years ago, which some scientists suggest brought the entire human population down to about 1,000 adults, so a great deal of attention is being paid to these threats as well. A recent informal poll of our 500 some scientific advisory board members, ranked a global pandemic as the biggest short term threat, with major asteroid impact a close second. Global Warming was near the bottom of the list, and beat only alien invasion as a serious threat. We recently met with the Naval War College’s Strategic Studies Group and gave a presentation on possible threats we might face in the near future.

Tugunska sized impacts seem to occur once per century, be on the lookout!

Lifeboat Foundation

http://lifeboat.com/ex/main

[ST1DinOH]

there is another side to this coin.

aside from the apocalyptic discussion at hand, the Tunguska incident could have been caused by this.

Tesla was hard at work try to prove his machine could do what he claimed. this could have been Tesla tinkering at Wardenclyffe. this could have been the inspiration to his “death ray” that he was looking to make for the military to shoot down planes and missiles.

i’m just sayin…

if anyone was able to do this, it was Tesla.

[Jackethan]

I like the Tesla theory, for its coolness factor. Considering his other achievements, I think it may be possible.

[Tsiklon]

The usual Hollywood fantasy is to use a nuke. Here is the problem with that. Many asteroids are accretion bodies. That is they are essential rubble piles held together with weak gravitation. If the body is large enough a nuclear blast would just break it into several big pieces, each of which can do vast damage to the planet and to civilization. The better way would be to mount low thrust rocks on the body far enough out to divert it. But, as I pointed out, the difficulty is seeing bodies big enough to destroy civilization (on impact) but small enough not to be seen for a sufficient time to get a fix on the orbit.

Mount rocket engines on an Asteroid to try nudge its orbit??? You gotta be kidding me!

You folks dont seem to take into consideration just how much heat is produced by a nuclear explosion(in outer space). If the ensuing fireball is large enough to engulf the asteroid(and some of its extra chunks) it will vaporize it into a harmless cloud of plasma. Chunks outside of the fireball will still absorb enough heat to liquefy. The trouble is few nuclear warheads, particularly those built by the US, have large enough yield to vaporize an asteroid. The only one that might be powerful enough to be of use is the 25-Megaton warhead that tips the Russian SS-18 “SATAN” missile. I think that not only should there be space missions to rendezvous an unmanned probe with a Near Earth Asteroid, but once we can intercept asteroids close to Earth there should be another mission with a probe carrying a large contact burst nuclear warhead. It may very well be that we might need a Nuke with a yield as large as the great Tsar Bomb which was 50 Megatons and produced a fireball 8 miles wide.

[Grames]

Mount rocket engines on an Asteroid to try nudge its orbit??? You gotta be kidding me!

No he’s not kidding. Low thrust, long endurance rockets would be the way to go. A bomb would be unable to produce a fireball in space, there would only be the flash of radiation.

[Tsiklon]

A bomb would be unable to produce a fireball in space, there would only be the flash of radiation.

Thats not true. The sun is a perpetual thermonuclear explosion. The energy released by a nuclear explosion on the surface of an asteroid would be absorbed by the asteroid and its enough to vaporize it into plasma. Exoatmospheric nuclear tests have been carried out and they DID indeed produce fireballs.

[Grames]

Thats not true. The sun is a perpetual thermonuclear explosion. The energy released by a nuclear explosion on the surface of an asteroid would be absorbed by the asteroid and its enough to vaporize it into plasma. Exoatmospheric nuclear tests have been carried out and they DID indeed produce fireballs.

It is true. Less than half of the energy of a nuclear explosion on an asteroid would be absorbed, that energy would create a crater much smaller than the apparent size of the ejected mass plume. An asteroid small enough to be vaporized would also be small enough to not be concerned about in the first place.

Small asteroids have a tendency to be low density according to this paper. This will spread out the total amount of energy able to be absorbed by the body while also reducing the effective cross section. In other words, the less dense it is the more effectively transparent it will be to the radiation released by the bomb. So multiply that starting factor of 1/2 by another small ratio. The question is what fraction of the released radiation converts into the energy raising the temperature of the body, and is that enough to do anything? The answer is not obvious.

It is also not obvious that if successfully vaporized, a mass of superheated (and now radioactive) gaseous and liquid metal hitting the earth is better than a solid mass.

The visible traces of an exoatmospheric nuclear explosion are mainly the glowing remnants of the device itself. That “fireball” not at all equivalent to a surface explosion which produces a shock wave and a literal firestorm where everything heated enough by the radiation oxygenizes, and a huge bubble of superheated air and ash that buoyantly rises through the atmosphere producing a mushroom cloud.

[Tsiklon]

It is true. Less than half of the energy of a nuclear explosion on an asteroid would be absorbed, that energy would create a crater much smaller than the apparent size of the ejected mass plume. An asteroid small enough to be vaporized would also be small enough to not be concerned about in the first place.

Small asteroids have a tendency to be low density according to this paper. This will spread out the total amount of energy able to be absorbed by the body while also reducing the effective cross section. In other words, the less dense it is the more effectively transparent it will be to the radiation released by the bomb. So multiply that starting factor of 1/2 by another small ratio. The question is what fraction of the released radiation converts into the energy raising the temperature of the body, and is that enough to do anything? The answer is not obvious.

It is also not obvious that if successfully vaporized, a mass of superheated (and now radioactive) gaseous and liquid metal hitting the earth is better than a solid mass.

The visible traces of an exoatmospheric nuclear explosion are mainly the glowing remnants of the device itself. That “fireball” not at all equivalent to a surface explosion which produces a shock wave and a literal firestorm where everything heated enough by the radiation oxygenizes, and a huge bubble of superheated air and ash that buoyantly rises through the atmosphere producing a mushroom cloud.

Less than half?? How did you come to this conclusion?(cite sources/calculations please)

A nuclear explosion in space releases no less energy than one on the earth(including atmospheric airbursts). The main difference is the HOW the energy from the explosion is dispersed. The fireball you see from a groundburst is comprised of plasma. This plasma is formed when the intense burst of radiation collides with matter. In space there would be no pressure wave but their WOULD be a very intense wave of electromagnetic radiation with a high enough energy density to vaporize matter within a certain radius. So my point is that a large enough nuke certainly would have enough energy to vaporize an asteroid into plasma which would be ultimately dispersed by the solar wind. At a high enough intensity, X-rays and Gamma rays will strip electrons off nuclei and send them flying out into space. These X-ray burst from a nuclear blast are intense enough to burn through tons and tons of solid ground, like IVY MIKE did when it vaporized the entire islet of Eleugelab.

[D_kian]

Facts are your friends:

1. The idea is to divert the asteroid, not to vaporize it. an explosion is the easiest way to accomplish that goal, taking into account a launch from Earth.

2. Any explosive detonated in a vaccum would produce a shockwave. It comes from the components of the bomb that vaporize in the explosion. For a nuke this would include the entire assembly and casing.

3. You can increase the mass of gas for the shockwave by surrounding the case with compressed air, liquified air, liquid nitrogen, or any other kind of easily liquified gas (think natural gas, argon, oxygen, etc). The best bets are plain air and nitrogen. Or you could add a honeycomb of soft metal like sodium. Gases are lighter, though, therefore less expensive to get to target fuel-wise.

[Grames]

Less than half?? How did you come to this conclusion?(cite sources/calculations please)

The simple geometry of an omnidirectional explosion up against a surface produces the one half factor. It would only be exactly half if the surface were an infinite plane, and as it will actually be up against an irregular convex shape modeled as being tangent to the surface of a sphere it will be less than half, but close enough.

A nuclear explosion in space releases no less energy than one on the earth(including atmospheric airbursts). The main difference is the HOW the energy from the explosion is dispersed. The fireball you see from a groundburst is comprised of plasma. This plasma is formed when the intense burst of radiation collides with matter. In space there would be no pressure wave but their WOULD be a very intense wave of electromagnetic radiation with a high enough energy density to vaporize matter within a certain radius. So my point is that a large enough nuke certainly would have enough energy to vaporize an asteroid into plasma which would be ultimately dispersed by the solar wind. At a high enough intensity, X-rays and Gamma rays will strip electrons off nuclei and send them flying out into space. These X-ray burst from a nuclear blast are intense enough to burn through tons and tons of solid ground, like IVY MIKE did when it vaporized the entire islet of Eleugelab.

1. The idea is to divert the asteroid, not to vaporize it. an explosion is the easiest way to accomplish that goal, taking into account a launch from Earth.

I will respond to both of these comments with the question:

If the entire mass of a theoretical 100 meter asteroid were to be vaporized, how exactly does that impart any net change in momentum to the mass? It does not divert.

This method does not work well as a quick reaction, and there are cheaper more controllable options with several years warning.

2. Any explosive detonated in a vaccum would produce a shockwave. It comes from the components of the bomb that vaporize in the explosion. For a nuke this would include the entire assembly and casing.

There is not enough mass in the shockwave compared to the mass of an asteroid to impart a significant momentum transfer.

3. You can increase the mass of gas for the shockwave by surrounding the case with compressed air, liquified air, liquid nitrogen, or any other kind of easily liquified gas (think natural gas, argon, oxygen, etc). The best bets are plain air and nitrogen. Or you could add a honeycomb of soft metal like sodium. Gases are lighter, though, therefore less expensive to get to target fuel-wise.

Yes, but to accomplish momentum transfer a more massive material is better. A few tons of stuff is going to have a hard time moving a 100 meter asteroid, a mass which is orders of magnitude larger than that.

If you do it far enough out from the earth any small change in momentum would be enough, but for the same reason if you could deploy a system far enough ahead of time ( multiple close passes, i.e. years ahead of time) it would be much cheaper to drop an engine onto the rock and have far more control over what happens.

Apparently NASA has put some time into mission planning this general scenario: NASA plans ‘Armageddon’ spacecraft to blast asteroid They plan to drop an engine onto the asteroid anyway, as part of the mission.

[Tsiklon]

The simple geometry of an omnidirectional explosion up against a surface produces the one half factor. It would only be exactly half if the surface were an infinite plane, and as it will actually be up against an irregular convex shape modeled as being tangent to the surface of a sphere it will be less than half, but close enough.

Good point. But if the yield were large enough in proportion to the size of the asteroid, there would still be enough energy to vaporize it into a cloud of plasma. For instance, the IVY MIKE device, which was 15 Megatons and detonated on the ground, burned through enough earth to create a crater 1.8 miles wide and 200 feet deep.

Its true that the momentum of the asteroid would result in a jet of fire. But the cool thing(no pun intended) about plasma is that since it’s electrically charged and if the asteroid were vaporized within the Earth’s magnetosheath the plasma cloud would be pulled towards the Earth and rain down on the Ionosphere making for a very pretty Aurora display! :o If the asteroid were hit far enough out in space that it was outside of the magnetosheath it would be swept away by the solar wind.

[D_kian]

If the entire mass of a theoretical 100 meter asteroid were to be vaporized, how exactly does that impart any net change in momentum to the mass? It does not divert.

If the entire mass of the asteroid were vaporized, who cares where the molecular-sized chunks go? They can’t penetrate the atmosphere without burning up.

This method does not work well as a quick reaction, and there are cheaper more controllable options with several years warning.

Better, yes. Cheaper, no. Faster, no. a nuke works all at once. You set it off, you either get a trajectory change right there and then, or you don’t. A reaction system, or any other possibility (solar sails, large masses, etc) would be much more expensive and require years of planning and execution. Well and good if we ahve years. A death sentence if we don’t.

There is not enough mass in the shockwave compared to the mass of an asteroid to impart a significant momentum transfer.

Agreed, but there’s a great, heaping load of kinetic energy involved. All the explosive energy of the bomb, that not going towards radiation, would be transferred through the shock wave.

If you do it far enough out from the earth any small change in momentum would be enough, but for the same reason if you could deploy a system far enough ahead of time ( multiple close passes, i.e. years ahead of time) it would be much cheaper to drop an engine onto the rock and have far more control over what happens.

Agreed. Yet if we had only, say, two years lead time, it would be explosives or nothing.

[Grames]

If the entire mass of the asteroid were vaporized, who cares where the molecular-sized chunks go? They can’t penetrate the atmosphere without burning up.

They don’t have to penetrate the atmosphere to have equally bad effects. In near earth space the debris storm does massive damage to the artificial satellite fleet, and then it enters the atmosphere and has effects similar to a giant volcano going off on earth. And forever after that, there is this cloud of crap that passes near the earth annually for decades, making new replacement satellites and manned space flight very risky. This is just a bad way to go.

[D_kian]

They don’t have to penetrate the atmosphere to have equally bad effects. In near earth space the debris storm does massive damage to the artificial satellite fleet, and then it enters the atmosphere and has effects similar to a giant volcano going off on earth. And forever after that, there is this cloud of crap that passes near the earth annually for decades, making new replacement satellites and manned space flight very risky. This is just a bad way to go.

Better than letting the asteroid hit the Earth.

BTW you can’t vaporize an entire steroid. At best a portion of it with existing technology, or with any likely technology. I’d like to see a fireball that can consume a volume 100 miles in diameter!

[Grames]

Better than letting the asteroid hit the Earth.

BTW you can’t vaporize an entire steroid. At best a portion of it with existing technology, or with any likely technology. I’d like to see a fireball that can consume a volume 100 miles in diameter!

100 miles diameter asteroids would be dangerous if there were any in earth crossing orbits. That is big enough to be seen, so the fact that we don’t see them is evidence they don’t exist. Much smaller asteroids are the real threat, ones hundreds of feet in maximum dimension.

[D_kian]

100 miles diameter asteroids would be dangerous if there were any in earth crossing orbits. That is big enough to be seen, so the fact that we don’t see them is evidence they don’t exist. Much smaller asteroids are the real threat, ones hundreds of feet in maximum dimension.

You woulnd’t necessarily see a 100 mile wide asteroid if its orbit is eccentric enough to take it far away from Earth. Anyway, vaporizing a rock a few hundred meters wide is also impossible, at least using a nuke.