I What Size Space Bombs Would Detonate in Midair Based on Their Composition?

[JohnWDailey]

On June 30, 1908, the remote Siberian region of Tunguska made headline news when an explosion knocked down 80 million trees in an area of only 770 square miles. The mystery was that there was no crater, which led to the assumption that the space bomb responsible for the catastrophe detonated in midair--a behavior scientists call an "air burst". The explosion must have happened four to six miles above the actual lands of Tunguska.

We know that the space bombs that visit Earth, be they comets or asteroids, comprise of any of three materials--rock, metal or ice, and each reacts differently to the rising pressure associated with descending to the Earth's atmosphere at high speed.

Let's say that we have a scenario where a space bomb is due to explode four to six miles above the Earth and duplicated it three times so that we have one scenario where the space bomb is made of rock, another of metal and one more of ice. At an altitude of four to six miles, what is the largest space bomb from each scenario that would fall down before being detonated in midair?

 

[Vanadium 50]

"Space bomb"? This sounds artificial. This is an entirely natural phenomenon.

 

[OmCheeto]

On June 30, 1908, the remote Siberian region of Tunguska made headline news when an explosion knocked down 80 million trees in an area of only 770 square miles. The mystery was that there was no crater, which led to the assumption that the space bomb responsible for the catastrophe detonated in midair--a behavior scientists call an "air burst". The explosion must have happened four to six miles above the actual lands of Tunguska.

We know that the space bombs that visit Earth, be they comets or asteroids, comprise of any of three materials--rock, metal or ice, and each reacts differently to the rising pressure associated with descending to the Earth's atmosphere at high speed.

Let's say that we have a scenario where a space bomb is due to explode four to six miles above the Earth and duplicated it three times so that we have one scenario where the space bomb is made of rock, another of metal and one more of ice. At an altitude of four to six miles, what is the largest space bomb from each scenario that would fall down before being detonated in midair?

hmmm... I can't remember how to figure that out. But I did find a very fun app for that last year: Impact: Earth! A meteor/comet impact simulator [PF]

Devilishly fun.

 

[JohnWDailey]

"Space bomb" is anybody from space that detonates on contact with Earth, be it on the surface or the atmosphere. If you want to be conversational, be general. "Meteor" and "meteorite" won't do because such changes in name implies a change in mechanics and chemistry, which there really isn't.

 

[davenn]

"Space bomb" is anybody from space that detonates on contact with Earth, be it on the surface or the atmosphere.

not in any reliable scientific literature I have ever read. please don't use this term ... yet another garbage pop-science termDave

 

[JohnWDailey]

You know, it doesn't really hurt to be conversational.

 

[Drakkith]

"Meteor" and "meteorite" won't do because such changes in name implies a change in mechanics and chemistry, which there really isn't.

The term used by astronomers is generally "bolide" or "superbolide", though there is no official term from the IAU. See here: https://en.wikipedia.org/wiki/Bolide

Let's say that we have a scenario where a space bomb is due to explode four to six miles above the Earth and duplicated it three times so that we have one scenario where the space bomb is made of rock, another of metal and one more of ice. At an altitude of four to six miles, what is the largest space bomb from each scenario that would fall down before being detonated in midair?

According to the table on this wiki page, a stony object 50 meters across detonates around 5-6 miles in the air. Based on the table, it looks like the altitude depends on the diameter of the object, so a larger object would explode closer to the ground. I'm guessing the diameter of the object would need to be about 55 meters or so do get an explosion at 4-5 miles in altitude. I don't know what the diameter might be for non-stony objects.

 

[OmCheeto]

...
I don't know what the diameter might be for non-stony objects.

The link I referenced yesterday, Impact: Earth!, has a link to a paper that appears to be the source for everything one needs to figure this out: Earth Impact Effects Program: A Web-based computer program for calculating the regional environmental consequences of a meteoroid impact on Earth

Unfortunately, I'm not willing to do John's homework.

 

[CWatters]

According to the table on this wiki page, a stony object 50 meters across detonates around 5-6 miles in the air. Based on the table, it looks like the altitude depends on the diameter of the object, so a larger object would explode closer to the ground.

Begs the question... Why don't all small ones burn up very high up? How come so many make it to the ground and are picked up in places like Antarctica? Are all small ones the result of a bigger one exploding high up?

 

[Drakkith]

The link I referenced yesterday, Impact: Earth!, has a link to a paper that appears to be the source for everything one needs to figure this out: Earth Impact Effects Program: A Web-based computer program for calculating the regional environmental consequences of a meteoroid impact on Earth

Unfortunately, I'm not willing to do John's homework.

Thanks for the links, Om. The paper and calculator were excellent.

 

[Drakkith]

Begs the question... Why don't all small ones burn up very high up? How come so many make it to the ground and are picked up in places like Antarctica? Are all small ones the result of a bigger one exploding high up?

I assume they were much bigger, but most of the material was vaporized during the travel through the atmosphere. I'm no expert though, so I have no idea about all the details.

 

[OmCheeto]

I assume they were much bigger, but most of the material was vaporized during the travel through the atmosphere. I'm no expert though, so I have no idea about all the details.

@D H struck me as the most "experty" person regarding meteors, here at the forum.
He taught me a lesson or two about the Tunguska event.

 

[sophiecentaur]

You know, it doesn't really hurt to be conversational.

I'm not sure about that. Sloppy language can lead to massive misunderstandings and "it really doesn't hurt" to learn and to use the general accepted terms in a technical argument. If a symbol in a mathematical procedure is suddenly changed then you could expect a seriously wrong answer - likewise with a change of words.

 

[bobkolker]

bolide. A word of Greek origin meaning ball or quasi-spherical object. A round rock is a bolide