|
MachFront.com |
|
|
MachFront.com |
|
What is a Mach Front?
| During a nuclear explosion,
the air that has been compressed and accelerated outward by the nuclear
fireball’s explosive expansion separates and propagates outward as a
shock wave.
When this primary shock wave strikes the ground or water, a secondary shock wave is generated by reflection. The two waves propagate outward along the ground or water, forming a single reinforced shock wave called the Mach Front. A Mach Front is a single vertical shock wave formed when the primary shock wave of a nuclear detonation reaches the earth's surface and coincides with a second wave generated by reflection. The overpressure (the amount by which its pressure exceeds atmospheric pressure) of the Mach front is roughly twice that of either the primary or secondary shock wave. |
 |
"Ah, that instant! I felt as though I had been struck on the back with something like a big hammer, and thrown into boiling oil…. I seem to have been blown a good way to the north, and I felt as though the directions were all changed around."
-A junior-college girl in Hiroshima.
The very first mechanical effect of a nuclear shock wave on any person or object in its path is a forceful blow from the instantaneous pressure jump in the front. This is followed immediately by the crushing effect of blast overpressure and a high velocity wind. These effects decrease quasi-exponentially with time until the pressure reaches atmospheric pressure (i.e. zero overpressure). After this there is a slight negative overpressure (i.e. a suction phase), along with a reversed blast wind [, p.4].
PSI?
| Very close
to the point of explosion, the overpressure can reach several
thousands of psi (pounds of pressure for every square inch). For the
purposes of comparison, the overpressure in a pressure cooker is of the
order of 1-15 psi.
The velocity of the winds accompanying the explosion for different levels of overpressure is listed in Table 1. As can be seen from it, the winds that accompany even a low overpressure have velocities that are associated with hurricanes and can cause significant damage by themselves.
|
|
| At 15-20 psi,
the winds from an explosion can fling a person at several hundred
km/hour. Near a glass window, at an overpressure of 5 psi, there could
be more than 400 pieces of glass per square foot of surface (each weighing
about 5 g on the average), flying at speeds of 200 km per hour or more.
An important difference between the blast effects of a nuclear weapon and an ordinary chemical explosive is that the shock wave for a nuclear weapon can be several feet in thickness. This could complete enclose a small structure simultaneously crushing it from all sides. Further, since it also takes much longer for the wave to pass through any structure, it subjects the structure to overpressure for a longer period of time. |
|
| Consider this: The body of an average 150 lb male, 6 feet tall,
has the surface
area of about 2930 inches. Say John Smith from Yonkers, NY, was
getting the morning's mail when a 25 MT nuclear weapon was detonated
just above New York City.
At a distance of just over 11 miles, the mach front would easily be 5 PSI. For every one of John's 3000 square inches, 5 pounds of overpressure is exerted. That's over 15,000 pounds of pressure total, or 7˝ tons. Ouch. |
| Air Burst:
25 Megaton blast
This is a diagram of a 25 MT airburst over New York city. Russia has several SS-18 "Satan" Intercontinental Ballistic Missiles (ICBMs) with a 25 MT warhead. The numbers inside the circles represent PSI. The diameter for the outermost ring is 62 miles. Click the image for a more detailed description of damage within the blast rings. |
 |
Although nuclear war has not yet happened, the sheer numbers of those that will be killed mean that, statistically, chances are decent that your death will be the direct result of a mach front. Prevent Nuclear War
Text on this webpage partially ripped from "Effects of Nuclear Weapons".
Questions? Comments? Send email to webmaster.
To get a free email forward account, email us with the following information:
1) The name of the @machfront.com email you would
like (ie, joe@machfront.com)
2) The email address that you want messages forwarded to. (ie, user@lameisp.com)
I'll try my best to accommodate you.