15m Diameter Meteor From Orbit

[Lord Poe]

Can anyone tell me where I can look up info about the effects of say 10 "15m diameter meteors splashing down from orbit in the middle of the Pacific" would be? Would ANY coastal towns be affected, etc.

I'm Googling as we speak!

[Darth Wong]

You just need a few assumptions and then you can start calculating.

1) Assume average density between 3000 kg/m^3 and 8000 kg/m^3
2) Assume typical NEO velocity of 30 km/s

A 15 m diameter object has volume of almost 1800 cubic metres, so its mass would be somewhere between roughly 5 and 15 million kg. Ergo, its kinetic energy would be half a megaton and 1.5 megatons. Of course, I'm assuming that the 15 m radius is the radius of the object which actually hits the Earth. If that's its size in space, a lot of its diameter would probably be burned off by the atmosphere.

[Lord Poe]

You just need a few assumptions and then you can start calculating.

1) Assume average density between 3000 kg/m^3 and 8000 kg/m^3
2) Assume typical NEO velocity of 30 km/s

A 15 m diameter object has volume of almost 1800 cubic metres, so its mass would be somewhere between roughly 5 and 15 million kg. Ergo, its kinetic energy would be half a megaton and 1.5 megatons. Of course, I'm assuming that the 15 m radius is the radius of the object which actually hits the Earth. If that's its size in space, a lot of its diameter would probably be burned off by the atmosphere.

I'm not giving the opposition any more outs than I already have! They said 15m, and that's what I'll stick with! To be clear, this is another idiotic TFN thread and the "Glove Of Darth Vader" wormhole bullshit:

+http://boards.theforce.net/Message.aspx ... t=25574292

...where it is postulated that only a small amount of the DS2 hit Mon Cal's ocans, and were "Y-Wing sized". I'm giving them 10 pieces to be extremely generous.

Actually, what you've said above is almost exactly what happeded here:

http://www.nss.org/settlement/asteroids/index.html

In October of 1990 a very small asteroid struck the Pacific Ocean with a blast about the size of the first atomic bomb (the one that leveled Hiroshima, Japan, killing roughly 200,000 people in seconds). If this asteroid had arrived ten hours later it would have struck in the middle of more than a million U.S. and Iraqi soldiers preparing for war.

What I haven't seen is what exactly constitutes a "very small" asteroid? Would 15m be considered "very small"?

[wolveraptor]

That depends. The average asteroid diameter is probably a lot more, because there are always a few gigantic ones that could pass for tiny moons, but the median value is probably much smaller, since there are a vast amount of miniscule ones. Of course, the definition of asteroid might disclude smaller rocks, so I'm not entirely sure.

[dragon]

Heres a fairly good impact calc from Arizona done by a geophysics professor. But like DW says the will break up before it impacts and you would end up with an airburst

http://www.lpl.arizona.edu/impacteffects/

[Darth Wong]

Minor correction: I calculated for 15m wide asteroids, but I accidentally used the word "radius" when summarizing it.

[Talanth]

Are you assuming it hits the ground intact? An atmospheric explosion from something that big could do a hellofa lot of damage.
Random link

[dragon]

Are you assuming it hits the ground intact? An atmospheric explosion from something that big could do a hellofa lot of damage.
Random link

15 meter wide asteroid won't do much damage at the surface as they will explode in the upper atmosphere. These explosions were caused by larger asteroids or slower moving ones.
The average impact is 17km/s according to the site I posted above. At 17km/s the asteroid will start to break up at 13900m and will busrt into a cloud of fragments at 2990m or about 10000 feet for you Americans.

At that height the airburst energy is about 430kt however since it is an airbust only a small part of that energy will be directed downward. according to there site at a distance of 1km from you not even receive 1pa of pressure. However some small peices will still hit the ground.

Now at a slower speed of 5km/s it will hit the ground with an impact energy of a little over 100kt. However most of that will be directed in a downward motion.

You will have a crater 434m in diameter and 92m deep. No thermal radiation at 1km but a 3.6 mag earthquake and 67kpa

However according to the site the minimal impact velocity is 11km/s but that I believe is for asteroids from deep space.

[dragon]

Damn hit submmit instead of preview. Anyways as the professor states these values are subject to flucactions as they are based on the limted under standiong of how asteroids undergo impact with the atmosphere.