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:
Raspet, R., "The Reduction of Blast Noise with Aqueous Foam,"
J. Acoust. Soc. Am., 74, (6), 1757-1763 (1983)
Aubert, J.H., Kraynik, A.M., and Rand, P.B., "Aqueous Foams,"
Scientific American, May, 1986, page 74ff
Clark, C.J., U.S. Patent 4,589,341, May 20, 1986 Method for Explosive Blast Control Using Expanded Foam
Raspet, R., "The Reduction of Blast Overpressures from Aqueous Foam in a Rigid Confinement," Applied Acoustics, 22, 35-45 (1987).
"Attenuation of Blast Waves Using Foam and Other Material," This is a composite publication of five technical papers. Army Construction Engineering Research Laboratory, Champaign, IL, 1988 (Available from NTIS, ADA203148) The included titles are: "The Reduction of Blast Noise with Aqueous Foam" (see above) "Attenuation of Blast Waves When Detonating Explosives Inside Barriers" "Shock Propagation and Blast Attenuation" "The Effect of Material Properties on Reducing Intermediate Blast Noise" "The Reduction of Blast Overpressures from Aqueous Foam in a Rigid Confinement" (see above)
Weaver, P.M., "Experimental Study of Shock Structure in Aqueous Foams and the Unsteady Shock Emergence at a Foam/Air Boundary," AIP Conference Proceedings, 208, #1, 819-824 (1990).
Larsen, M.E., "Aqueous Foam Mitigation of Confined Blasts,"
Int. J. Mech. Sci., 34, #6, 409-418 (1992)
Fondaw, G.W., "Mitigation of Shock Waves in a Cylindrical Tunnel by Foam,"
Thesis, Air Force Institute of Technology, March, 1993.
(Available from NTIS, ADA262491*DL)
Larsen, M.E., "NEST Containment Calculator,"
Sandia Report, 94-2030-UC-700, November, 1994
(Available from NTIS, DE95003090*BA)
Crepeau, J., et al, "First Principles Calculations of the Interaction of Blast Waves with Aqueous Foams,"
Sandia Report 99-1587C, July, 1999.
(Available from NTIS, DE00008466)
Thomas, G.O., "On the Conditions Required for Explosion Mitigation by Water Sprays,"
Trans I Chem E: Part B - Process Safety and Environmental Protection, 78, 339-354 (2000)
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.
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 modification have likely been incorporated - "Stabilized Aqueous Foam Systems and Concentrate and Method for Making Them," Rand, P.B., U.S. Patent 4,442,018, April 10, 1984. 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.
