Ambitions of all-electric Navy get reality check.

• Author: Jean, Grace V.
• Position: INSIDE SCIENCE + TECHNOLOGY

* Navy leaders for years have predicted an "all electric" future. Advanced electric drives are expected to revolutionize the way ships are designed and operated. But budget pressures appear to be challenging the Navy's vision, at least for the near term.

The poster child for the Navy's shift to all-electric propulsion is the DDG-1000 destroyer. Originally conceived as a fleet of 32 ships, the Zumwalt class now consists of only three ships to be built at Bath Iron Works in Maine. The class truncation has many implications for naval technology development.

Since the early days of the DDG-1000 program, the Navy has invested more than $100 million to develop a superconducting motor prototype to demonstrate its efficacy as the primary propulsion technology for all-electric ships.

American Superconductor Corp. and Northrop Grumman delivered the 36.5-megawatt high-temperature superconductor (HTS) ship propulsion motor in 2006. A few months ago they announced successful test results. This was the first test of a system sized for a large Navy combatant and the sole motor among three competitors to make full power rating for DDG-1000.

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So far, however, no ships will be outfitted with the advanced motors.

A study found that the DDG-1000 could double its missile count by using superconducting motors because they take up less space on the ship. "There are multiple interconnecting parts of a system on a naval ship that if converted to superconductor [technology], would have a very revolutionary impact on the combat capability of that ship," says Dan McGahn, senior vice president and general manager of American Superconductor, based in Devens, Mass.

Superconductors are known for their magnetic field-generating properties and their ability to conduct electricity efficiently. For the Navy this means naval vessels would be able to transfer power from propulsion systems to weapons and other shipboard functions as necessary and also free up shipboard space for other uses.

The HTS motor is the largest superconducting machine in the world, McGahn says. And yet, it is far smaller and lighter than a comparable conventional motor with the same output of 49,000 horsepower.

The secret lies in the wife. Motors typically consist of coils of copper wire in the rotor. Superconductor wire has about 150 times more conducting capacity than traditional copper wire and creates a strong magnetic field in less space. It also yields stealth properties that...