In March of 1982, the Soviet spacecraft Venera 13 landed a probe on the surface of Venus. The probe sent back the first color photographs from the surface of another planet, revealing that Venus has a desolate landscape to match its hellish atmosphere. It collected and analyzed a sample of the rocky surface, and its acoustic detector measured vibrations from the wind.
Venera 13 sent back some of the best data we have to date of Venus’s surface. The probe holds the record for the longest-lived Venus surface mission.
It survived for just 127 minutes.
Scientists have been trying to return to Venus’s surface since the late 1980s, but this time with instruments that will last for days or even months. That’s where GEER comes in.
GEER, the Glenn Extreme Environments Rig at NASA Glenn Research Center (GRC) in Cleveland, Ohio, is a test chamber that can create Venus-like conditions to study how materials placed inside the chamber react.
“GEER is a highly adaptable facility that’s constantly evolving its capabilities,” said Kyle Phillips, an aerospace and mechanical engineer at GRC. Phillips is GEER’s primary operator and test engineer. “In past tests, we’ve simulated conditions all the way from Venus surface conditions—both lowlands and highlands—up through the lower atmosphere through where we expect the cloud layers to be, and just slightly above the cloud layers and the upper atmosphere.”
Building Spacecraft to Last
Venera 13, its twin probe Venera 14, and the eight other successful attempts to land a probe on Venus all fell prey to the same thing: temperatures hotter than 450°C, pressures about 90 times that of Earth’s surface (90 bars), and a corrosive carbon dioxide–dominated atmosphere. Under those conditions, a spacecraft that might survive for years on Mars or the Moon would break down in minutes on Venus as the outer casing melts or dissolves, wires corrode, and delicate hardware warps.
The GEER team has “tested things like basic materials that one might use in a spacecraft or around the spacecraft,” said Tibor Kremic, chief of space science projects at GRC. “How do those interact with the environment? How do they fare? How did their properties and their functions change over time in a Venus surface–like environment?”
Test material is placed inside the 1-cubic-meter, corrosion-resistant stainless-steel cylinder. The test engineers then ramp up the pressure, temperature, and gas composition inside the chamber and hold it steady for days, weeks, or even months. “Currently, GEER can replicate temperatures from near ambient up to 1,000° Fahrenheit—that’s 537°C,” Phillips said, “and it can replicate pressures from ambient to rough vacuum to…94 bars.”
“We have done work over time in understanding what materials would be viable for long-term missions and which are not,” said Gary Hunter, a senior electronics engineer with GEER. For example, “copper, you might think, is just fine to use for electrical conductors. Turns out, don’t use copper. In fact, gold would be a better material to use because the reactivity on the Venus surface and at those temperatures is different, and the materials that are viable are different, than you might see in standard high-temperature operations on Earth.”
GEER has been operational since 2014, and the team has already made huge leaps forward in terms of designing Venus-durable spacecraft. During a test a few years ago, “we demonstrated electronics operational in Venus surface condition for 21 days,” Hunter said. Computer chips turned out to be fairly durable. “The longest time anything else had ever lasted before that point in terms of electronics on the surface of Venus…was approximately 2 hours. To go 21 days was showing a significant step up in what might be possible [in] Venus surface exploration.”
To Venus and Back in 80 Days
In its longest test to date, the GEER team subjected common geologic samples to Venus’s harsh surface conditions for 80 continuous days.
“We tested geologic material, so glasses, basalts, minerals, things that we expect might be on the Venus surface,” Kremic said, “to understand how they might change or what they might look like if we’re trying to identify them remotely.” A basalt or a glass or a silicate might have a different spectrum or appearance on Venus than on Earth, the Moon, or Mars.
Tests that reveal the properties of planetary materials at extreme conditions serve a dual purpose, Kremic explained. Mission scientists can tailor their instruments to measure Venus-relevant signatures, and they can use test results as benchmarks to interpret those measurements.
The 80-day test also underscored the need for a second, smaller test vessel that could be run at the same time as the larger one. “It’s a very small, mini GEER,” Kremic said. The aptly named MiniGEER went into operation in 2019. It’s just 4 liters in volume (250 times smaller than GEER) and can be brought up to temperature, pressure, and gas composition, and back down again, much faster than its larger counterpart.
“Maybe we have two things going on or we have tests that don’t require the volume [of GEER],” Kremic said, “and this way [they] can be done quicker and at lower cost.”
The Future of Venus Exploration
NASA might be headed back to Venus in the near future—two of its four finalists for a Discovery-class mission are bound for Venus. If one of those missions is selected, the GEER facility will be involved with getting the technology mission ready.
But the team has already been hard at work designing its own Venus mission, a small probe called the Long-Lived In-Situ Solar System Explorer (LLISSE). LLISSE would weigh about 10 kilograms and last for at least 60 days on Venus.
“At Venus you get a day-to-night or night-to-day transition at least once in a 60-day period,” said Kremic, who is LLISSE’s principal investigator, “and so we want to make sure that we capture one of those….We’re going to measure temperatures, we’re going to measure pressures, we’ll measure winds, maybe 3D winds on the surface of Venus,” as well as atmospheric composition and how all of those properties change over time. The team plans to build a full-scale ground model of LLISSE and test it inside GEER for the full 60 days by 2023.
The scientists are also exploring how GEER can adapt to simulate other places in the solar system and beyond. “The beauty and one of the unique things about GEER is that we can mix up pretty much whatever chemistry we want,” Kremic said, and new hardware might let GEER reach colder-than-ambient temperatures too.
“The results of what we’re doing will change and enhance our ability to do science, our understanding of our solar system, and of other [planetary] bodies, Venus in particular,” Kremic said, and we can “be more confident in what we send there.”
—Kimberly M. S. Cartier (@AstroKimCartier), Staff Writer