Sending a lander to Venus presents several huge engineering problems. Granted, we'd get a break from the nail-biting entry, descent, and landing, since Venus' atmosphere is so thick a lander would settle gently to the surface like a stone settles in water – no sky cranes or retrorockets required.
But the rest of the endeavor is fraught with challenges. The average temperature at the surface is 455 degrees Celsius (850 Fahrenheit), hot enough to melt lead. The mix of chemicals that make up the atmosphere, such as sulfuric acid, is corrosive to most metals. And the crushing atmospheric pressure is roughly equivalent to being 1,500 meters (5,000 feet) under water.
These extreme environmental conditions are where metals and electronics go to die; therefore, the few Venus lander missions that have made it to the surface – like the Soviet Venera missions – only lasted two hours or less. Any future landers or rovers will need to have nearly super-hero-type characteristics to endure on the surface of Earth's evil twin.
But there's one additional challenge that might be close to being solved: creating batteries that can operate long enough in Venus' hellish conditions to make a lander mission worth the effort.
NASA is working with a company called Advanced Thermal Batteries, Inc (ATB), and together, they created the first battery that has demonstrated the capability to operate at Venus' temperatures for an entire Venus solar day, which is approximately 120 Earth-days.
The battery is based on short-lived thermal battery systems used for powering smart missiles. The battery contains 17 individual cells and uses specifically designed chemistry and structural materials.
While the battery is still in development, engineers are encouraged that tests conducted demonstrate that these types of batteries are capable of operating in harsh environments like on Venus.
Additionally, this advanced type of battery technology may provide a new energy storage device for future exploration in harsh environments across the Solar System.
"This recent battery technology demonstration, with improved architecture and low self-discharge electrochemistry, is a huge accomplishment that many may have not thought possible," said Dr Kevin Wepasnick, ATB Project Engineer, in a NASA press release.
Batteries appear to be the only solution for powering a Venus lander. Solar panels are not viable due to surface light levels being comparable to an overcast day on Earth, and current solar panel designs would not withstand the high surface pressures. A radioisotope thermoelectric generator (RTG) requires bringing a heat source to the surface of Venus, and since heat management is already a major mission challenge, this method is not a good option.
But on Venus, thermal batteries can utilize the ambient atmospheric conditions to heat a special high-temperature electrolyte that is solid and inert at standard room temperature. Additionally, they can remain operational without the need for pyrotechnics or thermal insulation.
NASA says this new battery approach has demonstrated high-temperature operation for unprecedented periods of time, and lays the foundation for a new paradigm in battery technology and for Venus landers.
The work on the new type of thermal battery is part of ongoing work at NASA Glenn Research Center to develop a small Venus lander called the Long-Lived In situ Solar System Explorer (LLISSE).
The program uses the latest advances in high-temperature systems and a novel concept of operations to allow operations on the surface of Venus for 60 days or longer while the lander collects science data and transmits it to a Venus orbiter.
LLISSE is intended to be approximately 10 kilograms (22 pounds) and carry a suite of small sensors to measure winds, radiance, temperature, pressure, and abundances of key atmospheric chemical constituents. LLISSE will be a complete system with electronics, communications, and instrumentation – all of which will require a battery to operate.
ATB says they expect that a complete prototype Venus battery system will be demonstrated in the next 18 months.