Materials Development

Written by Tom Marlowe

MDA has called for research into a host of materials for missile body structures, electronics, propulsion systems and other subsystems to make them stronger and lighter as well as more capable of surviving extreme height.

The U.S. Missile Defense Agency (MDA) has placed a high priority on producing new materials for missiles that could survive more and more severe conditions. In the latest round of small business innovation research (SBIR) and small business technology transfer (STTR) solicitations, MDA has called for research into a host of materials for missile body structures, electronics, propulsion systems and other subsystems to make them stronger and lighter as well as more capable of surviving extreme height.

The latest round of research solicitations has a deadline of September 23. As with all SBIR/STTR solicitations, firms have an opportunity to receive a research contract for $100,000 in the first phase and another for $1 million in the second phase. A Phase II Transition program would move the SBIR projects into the Ballistic Missile Defense System.

Within the SBIR/STTR templates issued by the Department of Defense in July, MDA identified specific areas of interest for its SBIR/STTR projects for the coming year.

Those topics include producing semi-conductor materials to improve the cost, size, weight and performance of MDA radar systems. MDA has a specific interest in gallium nitride, which offers the potential to produce surfaces that resist subsurface damage. But the absence of gallium nitride crystals of sufficient quality and affordability dampen DoD’s ability to utilize the material to protect its systems, according to MDA.

MDA also seeks materials that can resist ultra-high temperatures for missile defense propulsion. The MDA Manufacturing and Producibility Directorate is looking for “highly innovative and significantly lower cost materials and processes for fabricating new, ultra-high-temperature materials systems for future compact, high performance divert and attitude control systems (for withstanding temperatures of approximately 5,000 degrees F) and for future hypersonic thermal protection systems (with capabilities of withstanding 4,000 degrees F).”

Other projects seek materials that would boost munitions insensitivity for use in propulsion systems for ballistic missile interceptors. MDA would like to see the interceptors, and indeed any of its systems, go further with stronger propellants. New missile materials are therefore required to withstand the power of the propellant, high altitudes, and the heat generated by the fuel, electronics, friction, and other factors.

The MDA also would fund materials for an Advanced Divert and Attitude Control System (DACS) with new components to reduce costs, improve munitions insensitivity, and increase safety. To accomplish these goals, MDA put out an SBIR for the Advanced DACS System to acquire a low cost (less than $200,000), light weight (less than 10 kilograms—about 22 lbs), high performance, fast reaction (less than 10 ms), and resistance to high temperature (2,500 degrees C) and high pressure (2000 psi) with minimum out-gassing.

“Advanced solid and liquid propellants that provide improved performance and reduced environmental impacts are needed with high-density-specific impulse products,” the SBIR solicitation read. “The increased combustion temperatures (greater than 2,500 degrees C) associated with advanced solid and liquid propulsion require more robust materials and processes, and propulsion systems with lifetimes commensurate with interceptor system operational requirements.”

Full details on the MDA SBIR projects are available at an MDA Website at http://www.winmda.com/.

Stronger and Lighter

The U.S. Army, like the MDA, always seeks ways in which to improve its missile systems. Keith Roberts of the U.S. Army Aviation and Missile Research and Development Engineering Center (AMRDEC) says the Army has coined the phrase “tailorable functionality” to describe what it seeks through these upgrades.

The quest to put new materials into new missile systems is driven by a desire to make munitions lighter and stronger, Roberts told MSMF.

“It allows us to increase the propellant to weight fraction,” Roberts stated. “So whatever inert weight we can take out of the missile, we can replace that with propellant. We get more range or we can put more lethality in it with a bigger warhead or whatever you need.

“We are always playing the game of trading off packaging and weight,” he continued. “If you have to sacrifice propellant or warhead capability, then you are heading in the wrong direction.”

The goals of incorporating new composite materials into missile subsystems are to make the missiles more insensitive to interference, increase their damage tolerance, and heighten their thermal management.

With composite materials, integrating composite materials into a motor case or a missile airframe to reduce weight often results in the removal of metal from those subsystems, Roberts noted. Removing metal, however, reduces electrical and thermal conductivity. Thermal conductivity is a particularly important issue lately, he added.

“That’s one of the bigger areas of concern when I talk to people in project offices,” Roberts remarked. “As missile electronics are getting more powerful and complicated and reduced in size, they are generating more heat. At the same time, we want to make the system lighter so we want to use composite materials. But composite materials—at least our fiber-reinforced polymers—are much lower in thermal conductivity than their metal counterparts. So we are making the problem worse there. That’s a big area of research for us—to improve those properties and take heat out of missile electronics.”

Of course, developing materials that meet all of these criteria can sometimes get expensive. Interest at the DoD in such research tends to wane when it becomes too expensive, Roberts cautioned. Qualifying a new material involves ensuring that DoD actually could afford to buy it.

“Since we are in the tactical world, we build relatively smaller missile systems in higher quantities. So cost is a huge driver. Whenever composite materials are brought up in discussions to reduce weight, the leading reason they are eliminated from the beginning is that someone will say, ‘That’s too expensive, and we cannot afford it,’” Roberts commented.

“We are constantly fighting the battle of trying to remove the perception that composites are too expensive but also try to come up with low-cost methods of producing them,” he said.

The tactical missile systems that benefit from new materials at the Army include the Joint Air-to-Ground Missile (JAGM), the Non-Line-of-Sight Missile (NLOS), and the Javelin missiles.

But the Army is trying to integrate new technology into any Army missile system that is a program of record. The service uses SBIR programs to produce materials that can become commercialized and thus widely adopted to make those technologies and materials available and affordable for Army missile programs.

“We are trying to create a toolbox for the missile designer where he can come back in, for example, and say, ‘I need this amount of thermal management in this area,’ and we will have the tools for him to accomplish that,” Roberts said.

Usable Tools

Materials Sciences Corp. (MSC) of Horsham, Pa., holds two Army SBIR projects specifically for the development of cutting-edge materials, Simon Chung, Ph.D., of MSC told MSMF.

The company is taking research and development from universities and other companies and moving that work forward into actual applications for improvements in missile technology. The SBIRs are managed by AMRDEC Weapons Development and Integration Directorate-Aerospace Materials Function. Technical points of contacts for these SBIRs are Keith Roberts and Matt Triplett. AMRDEC has ongoing programs, such as Applied Smaller Lighter Cheaper Munition Components-ATO, where they are seeking advanced materials with “tailorable functionality” to be used in the next generation of missile technology.

Its first SBIR with AMRDEC involves producing multifunctional polymers for composite structures to address munitions sensitivity issues.

“We are working with the University of Kentucky, and we are trying to improve performance properties like electrical and thermal conductivity through use of carbon nanotubes,” Chung explained. “We are looking at a couple of different ways to do that. One is to integrate these carbon nanotubes directly into the resin system. We are trying to utilize the superior performance properties of these nanotubes and translate into the missile casing.

“Another technology that we are looking at is the use of highly aligned carbon nanotube arrays,” he said. “That one is specifically to improve the thermal conductivity of the missile casing. The end goal is to promote venting in case of bonfires or slow cookoffs to prevent catastrophic failures.”

Their second AMRDEC SBIR is the High Strength, High Modulus Nano-Composite Missile Structures SBIR.

“In this case, we are looking to replace metallic parts with composite parts with the end goal of reducing weight and keeping production at a relatively low cost,” Chung stated. “Composites can be quite expensive.”

MSC is working with a couple of universities and commercial companies to develop an enhanced compression molding program through the use of discontinuous fiber prepreg materials. The goal is to take high-performance carbon fibers and nanoparticles and use them to improve the strength and toughness of missile structures while reducing the overall weight.

At the end of the SBIR projects, the Army would like to have a toolbox of options to choose from when designing new missiles, Chung observed.

“From our end, we want to develop both a combination of actual usable tools and materials that the Army can use for their next-generation design,” Chung noted.

Those tools would include general procedures on how to manufacture the composite materials.

“Nanotechnology can have a vigorous set of processing requirements. We want to outline if they want to integrate it, how would they produce it and implement it into an actual system. From there, we will leave it up to the AMRDEC to see where it best fits in their design,” Chung elaborated.

The company tests its composite materials thoroughly to ensure they would actually do what they were created to do and withstand the severe conditions of missile launches outlined by DoD.

But MSC also must make sure that incorporating these new materials doesn’t involve a vast restructuring of how the Defense Department makes its missiles.

“We must make sure the new materials we are making require minimal retrofitting of current manufacturing standards,” Chung said. “We don’t want them to reinvent the entire wheel just so they can implement some new material. We want to be as cost-effective as possible. One of the big goals in these SBIRs is to make sure the materials are processable so they can be easily integrated into the current manufacturing standards of the Army.”

The U.S. armed forces and the MDA continue to seek improvements in composite materials to maintain their strategic global leadership in missile technology, Chung remarked.

So while the agencies would like to make missiles lighter to enable them to travel further, they also constantly seek ways to do things like make munitions more insensitive, to increase electromagnetic interference shielding and thermal management, and add lightning strike protection as well.

“The end goal here was to provide tools for the Army so that when they are designing a next-generation system, these tools would be available to the designers and they could integrate them as they best see fit,” Chung concluded.

Commercial Concerns

Adding more propellant to a missile system to make the missile travel further involves materials that can handle higher temperatures because stronger propellant in higher quantities yields more heat, Marvin Young, Aerojet vice president of engineering, told MSMF.

Aerojet, based in Sacramento, Calif., is primarily a propulsion company working in propulsion systems for large strategic programs like the Atlas and Minuteman programs and small tactical systems like the Hawk and the Terminal High Altitude Area Defense (THAAD) missile defense system.

“We are looking at providing high-thrust, lightweight materials,” Young described. “A lot of the new mission requirements for missile defense and other missile systems really require much lighter-weight material and higher strength material—materials that can take much higher temperatures than they have in the past.”

Missile systems are getting larger with the intent to tackle larger threats, Young noted. The next generation of the THAAD missile is a much larger missile as is the SM-3 Block 2A missile system.

“If you have a larger missile, the payload gets larger. If you have a larger payload, you have to have lighter materials to accommodate the larger payload,” Young explained. “Likewise, if you have a mission that requires a lot of throttling, then you have to have propellants that run at very high temperatures so that you can throttle from 10 to 1 or whatever the mission requires. That usually requires you to have higher-temperature materials that can withstand those expectations. With that goes the higher strength requirement because they run at higher temperatures.

“They all combine into new missions that require a lot more capability of the missile system. As a result, they put a lot of stress on the current materials in terms of weight, temperature and strength,” he added.

These lighter, stronger, and highly survivable materials also must be affordable, Young said, which presents major challenges to a defense industry that has seen its influence in the commodities markets shrink over the years.

“A lot of our materials are going obsolete,” Young acknowledged. “It’s mainly because whereas the defense industry used to be a fairly major player in the commodities market, now it’s a relatively small player. Companies like Dupont and Dow Chemical and so forth find that the military portion of their business is getting smaller and smaller. So they will discontinue materials because it’s not as profitable as it was in the past.”

Domestic sources for these materials therefore dry up due to low demand. Carbon-fiber-reinforced carbon, for example, is no longer produced in the United States because it is not economically feasible to sustain a commercial market for it here.

To address this state of industry, Aerojet has been examining new resins that are more environmentally friendly as well as nanomaterials that offer increased temperature limits. Nanomaterials such as nanoaluminum and nanocopper offer exciting possibilities through breakthroughs, Young said, but also come with their own sets of challenges.

Nanomaterials, which are sub-micron-sized, come with a number of health concerns. Because they are very small, industry lacks common procedures for how to handle them in a way that addresses any health and safety concerns, Young said.

New materials also require a lot of database support that often doesn’t exist, leaving companies to spend a lot of time generating that database.

“You have to not only convince yourself that you have something affordable that is going to work but also to convince your customers. They only believe data. It takes a lot of money to create these databases,” Young said.

The life cycle of systems also must be considered as it dictates when new materials can enter into use. Even then, some customers may resist change due to fear of failure.

Still, Aerojet is expecting great developments from its investments in new materials.

“We are very excited about nanomaterials. We also are looking at ceramics,” Young affirmed. “We believe there is a lot of potential in the field of nanomaterials. We are hoping to explore that not only through government funding and SBIRs but also our own discretionary funding. We are looking forward to some fairly good breakthroughs in the near future.” ♦