Explosives research program evolves through statistics

  • Published
  • By Samuel King Jr.
  • Team Eglin Public Affairs
A 43-year-old stalwart, scientific bomb program is undergoing a revitalizing change by rethinking its methods and procedures through statistical analysis.

The High Explosives Research and Development facility, an Air Force Research Lab asset here, and its new way of thinking are expected to save the Air Force money throughout the life cycle of a bomb by more concentration and effort in the earliest research stages. This new method is called mixture design, an offshoot of design of experiments.

Mixture design and design of experiments are statistically rigorous methods for obtaining a suite of data and understanding the results and interactions between the variables. Mixture Design simply extends those rules to systems having multiple ingredients, according to Wayne Richards, a scientist with the HERD.

"We're building on a mountain of data we've collected already and looking at it in different ways to make significant changes and improve our weapons," said Richards.

The design of experiments approach is not a new method, but could not be fully realized by HERD technicians until the technology would allow them a different view point.

With the aid of statistics software packages, researchers are now employing these methods on complex explosive systems, tracking up to five variables at once, in order to find the "sweet spot" for safety and performance. Since so much information is known about the system and its interactions, technical risk is greatly reduced when a final composition is selected.

With the ability to see those various dimensions and levels, the scientists don't have to start from scratch, said Richards. He described it as having a recipe book for what already works. Scientists can try modifications to that initial recipe because they already know what similar variations provide. This cuts the developmental process in half, he said.

These new implementations provide the Air Force with a better explosive - a safer, more robust bomb.

"When an explosive gets developed, the ultimate goal is for it to detonate, but we need it to do a lot more," said Dr. Tom Krawietz. "It needs to survive 30 years of storage, thermal cycling, vibration on the aircraft, and ultimately penetrate through many feet of concrete. It needs to have high energy, but also have reduced sensitivity. Those things are typically at odds with one another. We must find a balance between them."

To make a better bomb requires some customization or trying to combine the various good properties, while eliminating as many unwanted ones as possible. At the same time, HERD researchers must ensure all of these elements don't conflict with each other.

This requires significant systematic data gathering in the forms of large scale range testing, air blast and sensitivity testing, all the way down to microscopic experiments to measure sensitivities toward impact, friction, electrostatic discharge, etc.

The HERD also has to analyze the what- ifs. Experiments must be done to see how those explosive properties age, the chemical decomposition, how they react to damage, such as a drop or vehicle accident on the flightline and many others.

HERD researchers are constantly in a balancing act of safety and lethality.

"We have to completely understand those trade-offs," said Richards. We must weigh the loss of performance versus the gain of safety, but not so much that it doesn't do what's required on impact."

The process to bring a new military explosive product to the inventory is an average of four years, but that doesn't account for the years of experimentation spent learning about the elements and properties that ultimately make up that new bomb fill.

Experimentation and research is a big part of the HERD mission, but it isn't the only part. The HERD has full-scale, bomb-making and filling capabilities. Whether they're making small, high precision charges to answer detonation physics questions or loading all-up-rounds for flight test or use by the warfighter, those items can be loaded here. Small charges are tested on-site, but larger assets are sent to Eglin's external ranges or cross-country for their debut.

The HERD is the only Air Force facility that develops explosives.  So what keeps this mature program ever-evolving and getting better with age?

"I think it's that sense of accomplishment," Richards said. "There is a reasonable chance we could see something we helped design on television impacting the war effort."