The more advanced the electronics, the more power they use. The more power they use, the hotter they get. The hotter they get, the greater the likelihood they’ll overheat. It doesn’t take a rocket scientist to understand what typically happens next: The electronics fry.
To quote Goddard thermal engineer Jeff Didion, “In the world of electronics, thermal control is always one of the limiting factors.”
However, he and his team have collaborated with various Goddard engineering disciplines, the National Renewable Energy Laboratory (NREL), and the U.S. Air Force to create a technology that overcomes the limitations. Already proven in laboratory tests that it works for long periods of time, the technology will be tested for the first time aboard a sounding rocket mission from the Wallops Flight Facility this spring.
Called electrohydrodynamic (EHD)-based thermal control, the technology promises to make it easier and more efficient to remove heat from small spaces, vastly expanding the capabilities of advanced instruments and microprocessors. “Today, higher-power chips are available, but they generate too much heat,” Didion said. “If I can carry away more heat, engineers will be able to use higher-power components. In other words, they will be able to do more things.”
Matthew Showalter, Jeff Didion, and Mario Martins are leveraging their respective talents to develop a new thermal-control technology that can fly in space. In this image, Didion holds a prototype pump that uses electric fields to pump coolant and remove heat generated by electronic components.
No Moving Parts
Unlike traditional single-phase thermal-control technologies that rely on mechanical pumps and other moving parts, EHD cooling uses electric fields to pump coolant through tiny ducts inside a thermal cold plate. From there, the waste heat is dumped into a radiator and dispersed far from heat-sensitive circuitry that must operate within certain temperature ranges. Its architecture, therefore, is relatively straightforward. Electrodes apply the voltage that pushes the coolant through the ducts.
The advantages are many. EHD-based systems are lightweight and consume little power, roughly half a watt. Furthermore, they are easily controlled. The application of a specific voltage creates the appropriate electric field that moves the coolant. But perhaps more importantly, the system can be scaled to different sizes, from macro-scale structural cold plates to micro-scale electronic components and lab-on-a-chip devices.
“EHD makes thermal control simpler,” said Tom Flatley, a technologist who is advancing the Goddard-developed SpaceCube processor, a next-generation technology that is 25 times faster than the current state-of-the-art flight processor. It is just one of several technologies that could benefit from the system’s continued development.
Benefits Multiple Applications
“Any electronic device that generates a lot of heat is going to benefit from this technology,” said Ted Swanson, assistant chief for technology for the Mechanical Systems Division. This would include everything from sensors flown in space to those used in automobiles and aircraft.
In development for more than a decade, Didion concedes the concept is not new. He and Jamal Seyed-Yagoobi, a professor at the Illinois Institute of Technology, have collaborated for more than a decade on EHD-based pumps, proving in a laboratory environment that they work for extended periods. What’s new is that he and his team, including Matthew Showalter, associate head of the Advanced Manufacturing Branch, and Mario Martins, an Edge Space Systems employee, are leveraging their respective talents to develop systems that can fly in space. “We’re taking a concept and making it an operational prototype for spacecraft applications,” Didion said.
Flight Demonstrations Scheduled
A prototype EHD pump will be demonstrated this spring when it flies as one of several experiments aboard a Terrier- Improved Orion sounding rocket from Wallops. The main objective is demonstrating that the technology can withstand the extreme launch loads as the rocket lifts off and hurtles toward space. Should it survive the vibration, the technology will have achieved a technology readiness level of seven, meaning it’s at or near operational status — a major milestone for any emerging space technology.
But Didion and his team don’t intend to stop there. With support from Goddard’s Internal Research and Development program, the Air Force, NREL, and others, the team is experimenting with composite materials and special micro-fabrication techniques and coatings to create smaller, more robust thermal-control units. Applications abound. These multifunctional devices could be used as stand-alone, off-the-shelf components ideal for quick-turnaround spacecraft — a capability that particularly interests the Air Force. In fact, the U.S. Air Force plans to demonstrate a modular, 12-inch square thermal-control plate during an upcoming flight.
The technology also could be embedded within the walls of the electronic device itself. Flatley will test the viability of an embedded unit during a SpaceCube experiment called ISE 2.0 flying on the International Space Station in 2013. “He’s working in stages,” Flatley said. “The next step would be to get the technology on circuit cards.” The ultimate goal, however, is to scale the technology to the chip level where the ducts would be no larger than 100 microns, or ten-thousandths the width of a human hair.
This is a breadboard device to prove the concept of using electrohydrodynamic-based thermal-control techniques for micro-scale applications.
“The point is that you want to place the thermal-control unit closer to the source of heat, which, of course, is a lot more efficient at eliminating waste heat,” Flatley said.
The future looks promising, Swanson said. “Jeff has come up with a way to push single-phase fluids around to get rid of heat. He’s demonstrated that it can work for long periods of time. He’s out there partnering with experts here at Goddard and those from other institutions. He’s doing the proverbial ‘look under every rock and around every corner’ in an attempt to advance this technology. In technology R&D, this is the model approach.”
The Office of the Chief Technologist is involved in a variety of projects, missions, and technologies.