5 FINDINGS AND CONCLUSIONS  

5.1 MILITARY RATIONALE

Potential Military Applications of MACE Superconducting Pulsed Transformer

The Department of Defense (DoD), Department of Energy (DoE), NASA and the military services have invested large amounts of funding for decades to find compact electrical pulsed power sources for a variety of applications. In the 1980s, the Defense Nuclear Agency (DNA) successfully developed high energy and high power density capacitors for nuclear simulators and other military applications.

As this technology was being developed and commercialized, these capacitors were combined with the necessary switches and safety devices to create Pulsed Forming Networks (PFNs) to enable electrical pulses to be created with a variety of voltage and currents. The capacitor PFNs have become the standard for laboratory and other pulsed power applications. For example, they have been used extensively as power sources for directed energy and electromagnetic launch systems (such as railguns).

Unfortunately, the capacitor-based PFNs are too large and heavy for most mobile military systems, but since they are reliable and available commercially, they have been used extensively in all pulsed power laboratory facilities. For example, the Navy accumulated large PFNs to power their laboratory railguns and decided to go forward with ship-based capacitor PFNs since they had sufficient space on board their large naval platforms. In parallel, they continued to develop higher energy density PFNs for ultimate ship-board use. A standard sea-container (38 m3) in 2010 was able to hold a capacitor PFN storing 8 MJ. The Navy has continued to fund industry to develop advanced capacitors and novel packaging so that the state-of-the-art has been increased from the ability to store 8 MJ to now 15 MJ in the same size sea-container. This is the result of much expert technical effort and is probably about the energy density limit for capacitor PFNs unless there is some unforeseen technical breakthrough in advanced capacitor materials.
 
In the 1980s, OSD initiated the National Electromagnetic Launch Technology Program (EML) and the Army took the lead in investigating high-energy-density pulsed alternators (compulsators) as the potential power supply for mobile EML systems. However, after an investment of several hundred million dollars over 30 years, the Army declared in 2010 that they did not have a power supply solution for a mobile railgun and cancelled their pulsed power and railgun programs.

An understanding of the fundamental physics behind these limitations can be seen in Figure 23: 

Figure 23

Figure 23. Principle of operation and fundamental limits for various energy storage technologies.

Electrical energy can be stored electrostatically in capacitors, inertially in the rotors of pulsed alternators, magnetically in inductors and electrochemically in batteries. It is obvious from the chart that the theoretical energy density of batteries is orders of magnitude higher than capacitors, but the internal resistance prohibits the energy from being extracted rapidly for pulsed power applications. Pulsed alternators potentially can achieve much higher energy and power density than capacitors but the complexity and necessary high rotating speeds have not led to a successful solution to date. Inductive storage is an attractive alternative, but the resistive losses have precluded a practical solution, until now. Advances in high temperature superconductors and their commercial availability as a result in the proliferation of medical magnetic resonance imaging machines have now enabled superconducting inductors to be serious candidates for compact pulsed power sources. The MACE superconducting pulsed transformer will provide an order of magnitude increase in energy and power density over the capacitor PFNs enabling significant reduction in size of the Navy power supply for their 32 MJ ship-based railgun and may enable MOBILE military systems for all of the military services.

Shown below (Figure 24) are current high-energy LASER, high-power microwave and the General Atomics Blitzer Railgun and their capacitor PFN power supplies. The SC pulsed transformer will enable similar systems to be constructed with much less volume and weight.

Figure 24

Figure 24. Current Directed Energy and Rail Gun Systems in development that could benefit from SC pulsed power transformers

Thus, the MACE SC pulsed transformer can significantly reduce the size of electric weapons systems and could enable mobile military systems for a broad class of directed energy (high-power microwave, LASER and EM launcher) weapons systems and they could replace capacitors as the power source for a number of other important military pulsed power applications.

 

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