Blasting & Explosions

note: Also see "Controlled Foam Injection" and "Foam Compression"

Aqueous foam is used for both blast attenuation and noise suppression. The technology was developed by Sandia (see also Military Defense Law web page) and is generally a military and law enforcement technology. Some pertinent references are:

In 1985 Sandia demonstrated the effectiveness of foam blast suppression, as shown in the following photographs originally published in the Scientific American article entitled "Aqueous Foams." In each case shown below 5 pounds (2.3 Kgs.) of C-4 military explosive was detonated. In the foam suppressed case 800 cubic feet of foam, expansion ratio = 200, was used to cover and then suppress the blast.

Sandia demo of foam blast suppression effectiveness Sandia demo of foam blast suppression effectiveness
Sandia, 1985
5# C4
Sandia, 1985
5# C4
800 CF Foam
E/R = 200
90% Impact Reduction

More recently a CBS television news story about Sandia and their antiterrorist technology development produced a short video which was shown on the evening news. Included in this video was a similar demonstration related to explosive disposal and chemical weapons disposal. Two still photographs are shown below. The C-4 charge was 4 pounds (1.8 Kgs.) in each case. The first picture was about 0.6 seconds after detonation. The second picture shows the "foam tent" supporting the suppression foam. The exact foam volume is unknown. As shown in the 10 second video clip, see below, the physical characteristics of the foam do not allow a "self-supporting" foam mound to be constructed. The foam is generally described in the following patent, although some modifications have likely been incorporated:

The video shows that the residual, unsuppressed, explosive force vents from the top of the foam tent. Three observations are:

  1. The plastic tent by itself could not suppress the detonation force
  2. There are foam systems currently available capable of self-support, thereby possibly eliminating the need for the plastic tent
  3. The military application requirements may necessitate a very high expansion ratio, thereby restricting some foam characteristic variables.
Sandia demo of foam blast suppression Sandia demo of foam blast suppression
Sandia
4# C4
t=0.6 secs.
Sandia
4# C4
t=0

Video


Foam Suppression Video