DARPA: Water Could Propel Next-Gen Satellites

The U.S. military is developing fuel technology to extend the life of its global surveillance satellites. The Defense Advanced Research Projects Agency (DARPA) — the U.S. Department of Defense’s central research and development agency — is working with Wallingford, Conn.-based Proton Energy Systems on a program to develop a self-regenerating fuel loop that would use water and solar power to create electricity onboard in-orbit spacecraft. However, questions have been raised in Congress about whether DARPA is focused sufficiently on R&D projects that would be most beneficial to a nation currently at war.

The use of much longer lasting satellites that are almost self-sustaining with the proposed fuel loops could have far-reaching implications for military, aerospace, homeland defense and commercial applications, said DARPA spokeswoman Jan Walker. The so-called “water rocket” program is intended to extend the operation time of satellites “greatly,” to reduce the weight of fuel at launch and to provide the U.S. military with more options for maneuvering its in-orbit satellites.

Satellites become useless once their fuel source has been depleted. The current design life of most geostationary satellites ranges between 10 years and 15 years. To maintain operation, a satellite’s solar panels absorb energy from the sun. Liquid fuel also is needed to propel the thrusters that enable the satellite to maintain orbit and to change its position.

Solar power helps to charge a satellite’s batteries in-orbit to provide additional power for use during eclipse season when the Earth blocks the sun’s view to the satellite. However, the alternative is sometimes to shutdown select functions in order to conserve power. Rather than compromise the operation of surveillance satellites, U.S. military officials are trying to develop a regenerative fuel-cell system that will keep its satellites running at full function 24 hours a day for an extended number of years.

In lieu of a complex chemical propellant, DARPA researchers have turned to the simple compound of water to provide the answer. Water is an inexpensive and easily handled liquid, which NASA has used as a fuel cell source for some of its extended shuttle missions. Through the fuel-cell system, solar power will electrolyze water into hydrogen and oxygen that then will be used by the satellite’s thrusters. Afterward, electricity can be generated through the conversion of some hydrogen and oxygen back into water, thereby charging the satellite’s batteries and providing electric power for satellite operation during periods of solar eclipse.

Feasibility Weighed

“The water-rocket program is feasible because the technology for ground-based regenerative fuel cells is well-understood,” said Walker. The challenge is to develop a regenerative fuel cell that would be able to operate in the zero gravity of space, she added.

Luke Dalton, program manager for Proton Energy Systems, said the fuel-cell technology that will allow satellites to continually generate their own power could help them remain in service for as long as 20 years if the onboard technology does not become too outdated.

The anticipated reduction in the satellite’s weight prior to launch could approach between 15 percent and 20 percent, and it could slightly cut the launch cost, with the possibility of even greater reductions after long-term use, Dalton added.

On June 1, Proton Energy Systems and the Naval Research Laboratory received $1.1 million from DARPA for an advanced fuel cell-development contract. That funding is intended to support continued work on the fuel-cell project. The DARPA award followed the successful completion of Phase I of the contract, originally presented to the company in 2002. Proton Energy Systems thus far has demonstrated its success with electrolyzing water into hydrogen and oxygen. The company also has demonstrated efficient compression of both gases through its solid-state electrolysis cell stack design, called HIPRESS.

The program manager for the water-rocket project is Dr. Robert Rosenfeld of DARPA’s Tactical Technology Office (TTO). According to DARPA’s Web site, the office “engages in high-risk, high-payoff advanced technology development of military systems.” In an overview of the water-rocket project, the office explained that the program is aimed at letting future spacecraft maneuver more easily into higher orbits as well as to refuel during longer, more advanced missions.

To bring the vision of a replenishing, in-orbit fuel source to reality, the TTO plans to design, fabricate and test a regenerative fuel-cell system that will be analyzed for performance and endurance. The biggest technical obstacles may not be known until the technology is tried in-orbit for an extended time. Developers at Proton Energy Systems said they aren’t sure when that phase of the technology rollout might take place.

Congressional Concerns

Despite the financial awards and the progress of the research, a key House committee is criticizing DARPA for its pursuit of such technology. The argument is that the agency instead should focus on more immediate military problems. Such criticism recently was reflected in the House version of the FY05 Defense Authorization Bill, which recommended a $204 million cut from DARPA’s current annual budget for the coming fiscal year.

A report about the bill by the House Armed Services Committee (HASC) stated that DARPA remains a defense agency, and it must be closely attuned to “real defense requirements.” The report further found that the pursuit of the more futuristic technologies must be tempered by the “hard fact” that the nation is at war.

“Our commanders and troops in Iraq have immediate needs for innovative technical solutions across a variety of disciplines,” the report explained. “The committee believes that DARPA should redirect some of its more futuristic efforts to the solution of today’s combat problems.”

Those immediate military needs involve detection, sensing, protection, surveillance and a host of other functions, the report said.

D.K. Sachdev, head of the Vienna, Va.-based SpaceTel Consultancy, said, “DARPA has an impressive record of nurturing long-term innovation over a wide spectrum of technologies; a well-known example is the very beginnings of the Internet itself. It [DARPA] has always encouraged exploration of far-out ideas, some of which can lead to real advances in national defense capabilities. Ideas and concepts that meet the threshold of viability get transferred to industrial organizations that are much better suited for product development for near term needs. Conversion of DARPA’s mission also to near-term applications could create a gap in nation’s long-term technological leadership.

DARPA has not detailed specifically how the military might deploy the project’s technology but potential applications might address current combat needs. Neville Marzwell, the advanced concepts innovation technology manager for NASA’s Jet Propulsion Laboratory, explained that satellites with a regenerative power source could be tactically moved in-orbit to any point of interest in a matter of hours. Depending on the trajectory, distance, orbit and atmospheric conditions, the regenerative technology could encounter some limitations in its ability to refuel a satellite as quickly as desired, he cautiously added.

“In many situations, it would be no problem to move satellites between trouble zones like Korea and Iraq, if that’s what is needed,” Marzwell said.

Government researchers suggest that fuel-cell technology may lead to a new generation of surveillance- satellite capabilities. For now, the project remains in the preliminary stages of research and development.

Real-World Applications

Critics question the practicality and the real-world applicability of the water-rocket project. Roger Rusch, who heads the Palos Verdes, Calif.-based TelAstra consulting firm, said fuel cells are practical and were used more than thirty years ago on the manned Apollo spacecraft.

“In fact, a fuel-cell explosion was the cause of the Apollo 13 anomaly that almost destroyed the mission,” Rusch said. “A fuel cell produces electricity that can be used for electric ion propulsion, such as the XIPS system. Such electric propulsion systems produce minute thrust, but have been experimented with at about 10-year intervals. So far, all have been extremely unreliable.”

DARPA’s traditional role is to work on leading-edge technology. Most of DARPA’s projects are “exotic, expensive, and few ever find applications in conventional, commercial-type projects,” Rusch said.

The government invests in research to determine if important technologies should be developed further, Rusch said. “Few are practical, but at least we know,” he added.

–Tonya Oben

(Roger Rusch, TelAstra, 310/373-1925; Jan Walker, DARPA, 703/696-2404; Luke Dalton, Proton Energy Systems, 203/678-2000 ext.540; Robert Friedland, Proton Energy Systems, 203/678-2144; Neville Marzwell, NASA’s Jet Propulsions Laboratory, 818/354-6543; D.K. Sachdev, SpaceTel Consultancy, 703/757-5880)