Electronics robust enough for Venus

Day or night, the mean temperature on Venus is about 460 °C, an extreme demonstration of the heat-trapping efficiency of the carbon dioxide that makes up most of the planet’s thick atmosphere. At the crushing surface pressure of 9.4 MPa—93 times that on Earth—the gas exists in a supercritical liquid-like state. Overhead, sulfuric acid clouds tens of kilometers thick are blown around the planet in hurricane-force winds.

Of the 26 spacecraft sent to Venus since 1961, only a handful have attempted to land on its harsh surface. In 1982 the Soviet Venera 13 lander sent the image shown above before its instruments failed, despite the protection of a pressurized vessel filled with heat-absorbing lithium salt, after a mere two hours on the surface. The quick demise is unsurprising, as silicon electronics start to fail at temperatures above 250 °C when too many electrons are thermally excited across the bandgap. In the ensuing decades, silicon carbide materials technology has matured enough to make the heat-resistant semiconductor a more suitable choice for high-temperature applications. In an effort to prolong the life of SiC-based integrated circuits (ICs), a research group led by Philip Neudeck of NASA’s Glenn Research Center has for the past several years toughened the metallic interconnects that link transistors; the protective, insulating layers around the interconnects; and other components. The effort has included choosing pure and relatively inert electronic materials that are stable at high temperature and whose thermal expansion coefficients are well matched.

Now Neudeck and colleagues have demonstrated that the robustly made ICs can operate successfully for several hundred hours in a simulated Venus atmosphere—no external cooling or sealed enclosure required. The researchers tested ring oscillator circuits—a standard logic technology—composed of dozens of field-effect transistors and resistors in a single IC. Shown at right with its packaging, the IC never failed during the 521 hours the team monitored the oscillator frequency inside the Glenn Extreme Environment Rig. The heat-, chemical-, and pressure-tolerant circuits are not just for spacecraft—other applications include monitoring jet-engine combustion and drill-bit temperatures in deep oil wells. (P. G. Neudeck et al., AIP Adv. 6, 125119, 2016 .)

Editor’s note, 9 February: the article was changed to reflect that the instruments of the Soviet Venera 13 lander were protected by lithium nitrate trihydrate, not dry ice.

Editor’s note, 8 February: the stated number of spacecraft sent to venus was changed to 26 to account for the fact that some probes were either flyby missions or failed before exiting earth orbit.