Why do high explosives produce much higher pressures than low explosives?

High explosives produce significantly higher pressures than low explosives because of the fundamental difference in their reaction mechanisms: detonation versus deflagration.1

• Detonation (High Explosives): These materials undergo extremely rapid decomposition characterized by a shock wave that travels through the explosive at supersonic velocities—typically 8 to 9 kilometers per second for solids and liquids. This process is nearly instantaneous, causing a violent release of energy that generates immense pressure.123
• Deflagration (Low Explosives): These materials, such as black or smokeless powders, rely on fast burning rather than a shock-driven reaction. The pressure is generated by the expansion of gases during combustion, which is a much slower process compared to the supersonic shock waves of high explosives.13

While low explosives can sometimes be forced to detonate under specific conditions of high confinement and large quantities, their standard behavior is limited to rapid burning, which inherently produces lower peak pressures than the instantaneous, shock-driven nature of high explosives.1