Sheet explosive and metal tube, fitted to the inner periphery of a cam-shaped chamber, accelerate particles to velocities nearing 20 km/sec to evaluate efficacy of spacecraft meteoroid shields

Wilson, A. H.

English

NASA Technical Reports Server

1972	 872-10082 
S	 NASA TECH BRIEF 
NASA Pasadena Office 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Velocity Accelerator for Particles 
	
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Sheet:..- 
Explosive	 ..7 
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Detonator
	
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Metal Block
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Exit 
The problem: 
It is desirable to accelerate particles to velocities 
approaching 20 km/sec so that the efficacy of space-
craft meteoroid shields can be evaluated. Explosives 
are ordinarily used as an energy source to produce 
high velocities, but since detonation rates are of the 
order of 9 km/sec, some method must be found to 
increase the effective detonation rate.
The solution: 
Sheet explosive and a metal tube are fitted to the 
inner periphery of a cam-shaped chamber. 
How it's done: 
A cam-shaped cavity is machined in a heavy block 
of metal, as indicated in the diagram; a heavy metal 
cover is fabricated to fit over the cavity block. The 
-.	
(continued overleaf) 
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cover must be capable of being tightly fastened to 
the cavity block with strong bolts. The depth of the 
cavity is sufficient to accommodate the outer dia-
meter of a thin metal tube that is closed at one end 
and made to conform with the shape of the cam. 
A hole at the position shown in the diagram is bored 
through the cover so that the bottom end of a small 
cylindrical detonator (a blasting cap) can come into 
contact with the surface of the sheet explosive. In 
order to assure detonation, a metal backing plate is 
located below the explosive and in line with the axis 
of the blasting cap. 
A thin sheet of commercially available explosive is 
cut to fit the inner contour of the metal tube and 
the exposed sides of the cam-shaped cavity, as indi-
cated in the diagram. Two spacers of the same shape 
are cut; the spacers may be made of any convenient 
material, e.g., cardboard, which has a thickness such 
that a sandwich of the two spacers plus the sheet 
explosive equals the outside diameter of the metal 
tube. The spacers locate the sheet explosive in ap-
proximately the same plane as the center-line of 
the metal tube. 
When the detonator is energized, the detonation 
wave initiated in the explosive begins to travel ra-
dially outward. During each unit of time, the wave 
travels a uniform distance d as indicated in the dia-
gram. The closed end of the metal tube will receive 
the detonation wave first; then each part of the tube
will receive the wave front in succession with the 
open end receiving it last. The action resembles the 
extrusion of toothpaste from a tube. Note, however, 
that during time interval 11, the detonation wave 
has compressed the metal tube along a length K in 
the same time interval that the detonation wave 
traveled radially the distance d; clearly, the rate of 
collapse of the tube is much greater than the de-
tonation rate. 
The contour of the cam-shaped surface can be 
varied so as to give a desired rate of collapse which 
is controllable between wide limits. 
Note: 
Requests for further information may be di-
rected to: 
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP72-10082 
Patent status: 
No patent action is contemplated by NASA. 
Source: Abraham H. Wilson of

Caltech/JPL
under contract to

NASA Pasadena Office 
(NPO-11349)
n 
. 
Category 03
C 


Velocity accelerator for particles

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