Is it possible to have an explosive which gives a super-powerful blast as well as creating lethally effective shrapnel? And what's the cost?
Shrapnel is the major source of lethality for most warheads, as it has an effective radius far greater than blast. But if you want the maximum blast, then fuel-air is better, and that doesn't create shrapnel. A fuel-air explosion has two phases: first the gas or aerosol is released to form a cloud which mixes with the air. In the second phase the cloud is detonated, producing an explosion which is much more powerful than the equivalent condensed explosive. However, unlike a condensed explosive, it can't split open a casing and convert it into fast-moving shrapnel. It can't 'drive metal'.
So although fuel-air explosives are extremely effective at destroying buildings (particularly from the inside), they're not so useful against other targets.
Thermobaric explosives or TBX lie somewhere between pure fuel-air and condensed explosives. A thermobaric explosive can be solid but 'fuel rich', for example such a mix of regular explosive with powdered aluminum or similar material. When it is set off, the thermobaric explosive produces an expanding fireball, with the leading edge containing white-hot aluminum particles which add to the explosive effect as they come into contact with the air and burn.
This presentation, entitled TBX Evaluation testing in The M151 Warhead As Risk Reduction for The APKWS shows that with thermobarics you can have it both ways. (The APKWS is the Advanced Precision Kill Weapon System, a small guided rocket which looks like being canceled – but the warhead technology is still valid) .
The aim was to build a warhead with enhanced blast and enhanced fragmentation, and they carried out a series of tests -- see photo -- with explosives from a number of different suppliers. These included the existing explosive filler ("Comp B") and other established and novel formulations:
Supplier Explosive
AMRDEC RAX-16
ARDEC Picatinny PAX-28
Ensign-Bickford Aerospace & Defense YJ-05
NAVY (NAVAIR, China Lake) CL133
NAVY (NAVAIR, China Lake) CLAP
Talley Defense Systems 7174
Talley Defense Systems 7172
Talley Defense Systems 7164
Alliant Techsystems TEPX-D
Alliant Techsystems \ Picatinny NIX-G
American Ordnance Iowa \ Picatinny PAX-3
AMRDEC Baseline PBXN-110
AMRDEC Baseline PBXN-109
AMRDEC Baseline (Current M151 Fill) Comp B
The table of resultson page 15 is surprising. You might have expected that the blast and shrapnel results would have been mixed, so that more blast meant less shrapnel. But that's not what happened.
One explosive fill came out a clear leader, scoring best not only on the blast pressure and blast impulse but also best on fragment velocity and the number of fragment perforations it produced, way outperforming the existing filler in both categories.
Which composition won is not revealed. But it does show that existing munitions can be made substantially more lethal against a whole range of targets with new explosives. But there is a cost: you have to use the dreaded T-word -- "Thermobarics," notoriously labeled 'brutal' or thermobarbaric. And there are not many in the Pentagon who want to go down that road.
