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CHIPS Articles: Q&A with Dr. Judah Goldwasser

Q&A with Dr. Judah Goldwasser
Office of Naval Research Program Officer for Energetic Materials,
By CHIPS Magazine - October-December 2007
The U.S. Navy is now developing a new type of munition that could improve lethality on the battlefield, while also helping to protect warfighters. Typically, munitions contain high explosives confined by a case made from inert metal that fragments when the explosive detonates. But the new munitions undergoing development are built using reactive material fragments. The goal of the Navy's development of these new reactive fragments is to create smaller warheads that are more effective than what is used on the battlefield today.

CHIPS asked Dr. Judah Goldwasser, a scientist and program officer with the Office of Naval Research for energetic materials to discuss his work at ONR with reactive materials. Dr. Goldwasser is currently on assignment to the Defense Advanced Research Projects Agency (DARPA).

CHIPS: I read about your work with reactive materials in several technology magazines. I noticed that the Air Force and the Army are also testing. Are you working with the other services?

Dr. Goldwasser: The answer is yes. In some cases, it can be described as coordination, and, in some cases, we are working more closely with them. We are not co-funding anything, but we are coordinating efforts.

CHIPS: How long has the research been going on?

Dr. Goldwasser: It has been going on for a long time.

CHIPS: I noticed that one of the benefits of this new type of munitions is the reduction of collateral damage. Is it because the weapon is more precise?

Dr. Goldwasser: That isn't the reason. RMs usually consist of reactive metals, combined with an oxidizing agent. Whether that agent is another powdered metal or a nonmetallic compound, contact alone isn't enough to trigger an explosion. A high speed impact, though, will chemically mix the materials, igniting them and leading to a compression wave and significant overpressure.

Normally, fragments travel for very long distances and can cause a lot of unintended damage both to objects and people. But the fragments caused by reactive materials can be engineered to limit the effective range before they disintegrate and thus can minimize collateral damage.

CHIPS: So would this type of weapon be suitable in urban warfare where you want to isolate your targets as much as you can?

Dr. Goldwasser: That certainly could be one of the applications.

CHIPS: What can you tell me about your research?

Dr. Goldwasser: The point of the research is to replace kinetic energy, the fast traveling fragments that are launched from explosive warheads are what we call kinetic energy, with a combination of kinetic and enthalpic energy.

Currently, in fragmenting weapons, the damage is caused by the steel fragments penetrating a component. The idea is to replace the inert fragment with a reactive material. The definition of a reactive material is that you build enthalpic energy into it. What I mean by that is these materials can be induced to burn in the air, instead of just flying through the air and causing damage by hitting something. When the fragments from reactive materials hit the target, they will come apart and burn in the air after they penetrate the target.

For defensive applications, for example, instead of getting a hole the size of the fragment as it penetrates into a threat missile, it will heat the local environment, in other words, the air inside the missile and increase damage. The other major benefit of that is that the extent of damage is much more visible so you know that you can stop shooting. You don't need as many weapons. You wouldn't have to re-attack the threat because of uncertainty as to whether you have destroyed it or not.

Those are two of the biggest advantages. It takes much less effort when you hit the target to destroy it and, secondly, you actually know that you have done it, and that you can stop shooting.

CHIPS: Is this technology in use now?

Dr. Goldwasser: This technology is still in development.

CHIPS: I see that one of the challenges in using RM is making the reactive material strong enough to survive the launch. Is that the main thrust of the research now?

Dr. Goldwasser: There are two aspects. One is that it's got to be strong enough to survive launch because explosives are used to launch the fragments. Explosives generally blow things apart, but in this case, the desire is to keep the fragments intact.

Because these fragments are reactive you have to shield them or make them strong enough that the explosion that is generated by the detonation that launches them won't set them off. You want them to initiate only after penetrating the threat so that it reacts inside and causes catastrophic damage.

There are questions about what kinds of materials are best suited for this and how to process them so that the fragment is both strong enough to survive launch and reactive enough to apply sufficient energy when needed to destroy the target.

CHIPS: Will it require a different type of launch mechanism?

Dr. Goldwasser: No, you would be able to retrofit or build standard types of warheads and use the same types of explosives. You just want to engineer the material so that it would survive explosive launch and that it would react when it hit the target.

CHIPS: Do you consider this a revolutionary change?

Dr. Goldwasser: The chemistry is not revolutionary, but the concept is revolutionary insofar as normally, the explosive contains all the energy and when it detonates, it transfers a portion of its energy to the fragments which fly through the air and cause the damage. By being able to put more of the energy of the warhead into the fragment, which reacts only when it hits the target, and not when the warhead explodes, you are bringing a lot more energy to the target than you normally would. It is a different type of defeat mechanism.

Another thing to be aware of is that these reactive materials are nonexplosive, which make them safe to handle. One of the big concerns is the possibility of unintended detonation should the warhead be attacked or subjected to fire or some other accident. There is an insensitive munitions program designed to keep explosive materials from detonating in these circumstances. One of the advantages of these materials is that we can get a lot of energy out of them — but they don't detonate.

CHIPS: How is the shock wave caused?

Dr. Goldwasser: The materials would collide with the target. The high velocity collision of the fragments with the intended target would cause it to react and heat up, which would cause the air to expand rapidly.

Whenever you have this discontinuity the gas expands to equalize the pressure and that causes the compression. As this wave hits the walls of the target or the components inside, it causes them to move. If you have enough energy behind it, it will break it, and that's what causes component or structural damage — the big hole. It is not a detonation but a rapid decomposition or heating up of the environment on the inside.

CHIPS: You mentioned that one of the benefits of this technology is reduced collateral damage incidents. Is that because the warhead breaks up in the air and you can control the distance of the shrapnel or fragment?

Dr. Goldwasser: The detonation of the explosive causes the fragments to fly through the air. Depending on how large they are and how fast they are going, they could fly for a long distance and hit unintended objects or people. Reactive materials can be engineered to limit their effective range and disintegrate after a certain amount of time or distance.

CHIPS: Will this technology be fielded any time soon?

Dr. Goldwasser: I can't speak to that because ONR is the science and technology office for the Navy. In order for it to be fielded it has to be transitioned to an acquisition program.

CHIPS: Is there anything else you can tell me about your research?

Dr. Goldwasser: We talked about the difference between a reactive fragment and a steel fragment, that they can bring higher levels of performance to the munitions that employ them because they are carrying more energy to the target. As a result, battle damage assessments will be easier. Safety issues are being addressed because these materials will not detonate. And they can be tailored to specific applications to reduce collateral damage.

The idea is to be able to provide meaningful new capabilities to warfighters. This new technology is being developed to do exactly that — by enabling increased performance using smaller warheads and addressing safety issues at the same time.

Dr. Judah Goldwasser
Dr. Judah Goldwasser

The Reactive Materials Enhanced Warhead Program demonstrated a missile warhead that defeats cruise missiles and manned aircraft by enhancing the kinetic energy of inert fragments with chemical energy when the target is hit. U.S. Navy photo Dec. 3, 2002.
The Reactive Materials Enhanced Warhead Program demonstrated a missile warhead that defeats cruise missiles and manned aircraft by enhancing the kinetic energy of inert fragments with chemical energy when the target is hit. U.S. Navy photo Dec. 3, 2002.
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