[extropy-chat] Impact Effects (was: Pluto New Horizons launch -getting ready)

[Amara Graps]

For the record, I'm really sad to lose Damien. Mehran went far beyond
the parameters of this list (and some wanted serious discussion with him!).
And adding the dangerous presence of Despres, the list suddenly took on the
personality of flypaper-for-the-bizarre.

>Amara et.al. what would happen if a ton of stuff hit the earth at
>.5c?  Surely it would be a bad hair day for humanity and the rest of
>animalty.)

The inputs are strange, but according to the results of the
impacts program, assuming a spherical iron density impactor on a head-on
collision, it would break up and leave a crater-strewn field.

This is the easiest way to check, since they've done the work for us:

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

PDF document that explains their equations: 
http://www.lpl.arizona.edu/~marcus/CollinsEtAl2005.pdf

I didn't finish reading the document to see all of their assumptions,
so perhaps the .5c is beyond what the program is designed to handle.
(although they say that it can handle 'science-fiction parameters')

------------------------
My notes:
The maximum velocity of an object orbiting the sun is 72 km/sec

Checking the energy, I get 1E19 J before impact, so how did they arrive
at 1E17 J, unless I did something wrong.

1 ton = 910 kg
Energy = 1/2 mv^2 = 1E19 Joules

------------------------ Results
Impact Effects
Robert Marcus, H. Jay Melosh, and Gareth Collins

Please note: the results below are estimates based on current
(limited) understanding of the impact process and come with large
uncertainties; they should be used with caution, particularly in the
case of peculiar input parameters. All values are given to three
significant figures but this does not reflect the precision of the
estimate. For more information about the uncertainty associated with
our calculations and a full discussion of this program, please refer
to this article

Your Inputs:
     Distance from Impact: 100.00 km = 62.10 miles
     Projectile Diameter: 0.60 m = 1.97 ft = 0.00 miles
     Projectile Density: 8000 kg/m3

     Impact Velocity: 15000.00 km/s = 9315.00 miles/s (Your chosen
     velocity is higher than the maximum for an object orbiting the
     sun)
     Impact Angle: 90 degrees
     Target Density: 2500 kg/m3
     Target Type: Sedimentary Rock

Energy:
     Energy before atmospheric entry: 1.02 x 1017 Joules = 2.43 x 101
     MegaTons TNT

     The average interval between impacts of this size somewhere on
     Earth during the last 4 billion years is 1.3 x 103years

Atmospheric Entry:
     The projectile begins to breakup at an altitude of 123000 meters =
     403000 ft

     The projectile bursts into a cloud of fragments at an altitude of
     65300 meters = 214000 ft

     The residual velocity of the projectile fragments after the burst
     is 14700 km/s = 9150 miles/s

     The energy of the airburst is 3.51 x 1015 Joules = 0.84 x 100
     MegaTons.

     Large fragments strike the surface and may create a crater strewn
     field. A more careful treatment of atmospheric entry is required
     to accurately estimate the size-frequency distribution of
     meteoroid fragments and predict the number and size of craters
     formed.

Major Global Changes:
     The Earth is not strongly disturbed by the impact and loses
     negligible mass.

     The impact does not make a noticeable change in the Earth's
     rotation period or the tilt of its axis.

     The impact does not shift the Earth's orbit noticeably.

Air Blast:

     The air blast at this location would not be noticed. (The
     overpressure is less than 1 Pa)


Earth Impact Effects Program Copyright 2004, Robert Marcus, H.J.
Melosh, and G.S. Collins
These results come with ABSOLUTELY NO WARRANTY
-- 

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Amara Graps, PhD          email: amara at amara.com
Computational Physics     vita:  ftp://ftp.amara.com/pub/resume.txt
Multiplex Answers         URL:   http://www.amara.com/
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"It is intriguing to learn that the simplicity of the world depends
upon the temperature of the environment." ---John D. Barrow