I found the definition of pyroshock at [
http://www.grc.nasa.gov/WWW/RT1998/7000/7735hughes.html ] to be:
Pyrotechnic shock, or pyroshock, is the transient response of a
structure to loading induced by the ignition of pyrotechnic (explosive
or propellant activated) devices. These devices are typically used to
separate structural systems (e.g., separate a spacecraft from a launch
vehicle) and deploy appendages (e.g., solar panels). Pyroshocks are
characterized by high peak acceleration, high-frequency content, and
short duration. Because of their high acceleration and high-frequency,
pyroshocks can cause spaceflight hardware to fail. Verifying by test
that spaceflight hardware can withstand the anticipated shock
environment is considered essential to mission success.
It is possible to calculate the average acceleration of the grenade in
g based on the distance it must travel and the speed it attains while
traveling this distance. The true initial acceleration or "shock
acceleration" of the projectile, however, would only be attainable
through testing. I was unable to find any website that listed this
figure based on real world testing.
That said, I will try to help you calculate the average acceleration
of an M203 grenade when fired. I claim no expertise in physics so you
may want to double-check my calculations.
When reading about specific grenades, I learned that some contain
their own propellant and they will all have different weights and
muzzle-friction characteristics, so each type of grenade will have its
own specific muzzle velocity.
=============================================================
Here are the search terms I typed into google.com to get the
conversion factors I used. Type the words that are in quotes directly
into the search box and you'll get the indicated results.
"convert feet to meters"
result: 1 feet = 0.3048 meters
"convert inches to meters"
result: 1 inches = 0.0254 meters
"convert g to meters per second squared"
result: 1 g = 9.80665 meters per (second squared)
=============================================================
Source 1:
The physical characteristics of the grenade launcher are documented at
[ http://conspiracyx0.tripod.com/weapons2/m203.htm ] as:
muzzle velocity: 246 feet per second = 74.98 meters per second
muzzle length: 14.96 inches = .38 meters
Source 2:
The physical characteristics of the grenade launcher firing an M406
are documented at [ http://www.pbs.org/wgbh/pages/frontline/shows/ambush/weapons/m203.html
]
as:
muzzle velocity: with M406 grenade, 74.7 m/s
muzzle length: 380 mm = .38 meters
Source 3:
The physical characteristics of the grenade launcher are documented at
[ http://www.nisat.org/weapons%20pages%20linked/US/m203_grenade_launcher.htm
] as:
muzzle velocity: 71 meter/second
muzzle length: 394 mm = .394 meters
=============================================================
So in the distance of the muzzle, the grenade has to accelerate from 0
to its full muzzle velocity. If we assume constant acceleration, then
we can use the basic laws of motion to work out the acceleration. I
used an online motion calculator [
http://hyperphysics.phy-astr.gsu.edu/hbase/mot.html ] to do the math
with the following results:
Source 1: 7397 meters per (second squared) or 754 g
Source 2: 7342 meters per (second squared) or 749 g
Source 3: 6462 meters per (second squared) or 652 g
I'd go with the second calculation for several reasons:
- It's the middle of the three numbers
- The figures come from PBS, a reputable news organization
- The figures are associated with a specific grenade, the M406
- The figures are sourced as from Jane's Infantry Weapons,
24th Edition, 1998-99.
- Jane's publications have a good reputation for having accurate
munitions data. |
