Venus is considered Earth’s sister planet because they’re about the same size and have similar compositions. That’s where the similarities end, though. Once scientists got a close-up look at Venus, they were greeted with a blistering hot hellscape with clouds of sulfuric acid. The European Space Agency (ESA) is planning a new mission to Venus, where its EnVision probe could conduct detailed science that has never been possible before. First, engineers have to figure out how to keep the spacecraft from blowing itself to bits as it descends into the planet’s ferocious atmosphere.
The ESA announced its selection of EnVision last year, and in recent days, it provided an update on the design and construction of the probe. The plan is for EnVision to perform an aerobraking maneuver in orbit of Venus, allowing it to gradually lower its orbit as it scans the surface. The agency has experience with this process from the Trace Gas Orbiter (TGO), as well as Venus Express. In the latter case, the ESA only attempted aerobraking at the end of the mission in 2014, and it did burn up in the atmosphere. With EnVision, the ESA needs to surf the corrosive soup clinging to Venus before it can get started doing science.
Samples for simulated aerobraking tests.
The Venusian atmosphere is 92 times denser than Earth, composed almost entirely of carbon dioxide, and probably doesn’t support life. The crushing pressure is complemented by temperatures that reach 864 degrees Fahrenheit (462 degrees Celsius). For the record, that’s several hundred degrees above the melting point of lead. This is what makes it so difficult to study Venus up close, but EnVision is being designed specifically for these conditions.
EnVision will most likely launch in the early 2030s on an Ariane 6 rocket. The ESA says it cannot budget enough mass to give the orbiter fuel to lower its orbit, so it will rely on aerobraking. The mission will begin in a very high orbit at 250,000 kilometers (155,000 miles), and through successive passes through the atmosphere, it will drop to a 500-kilometer (310-mile) polar orbit for science operations — it won’t land on the surface.
The ESA plans to take it slow with EnVision. Because heat is generated as a cube of velocity, it will spend about twice as long slowing down as the TGO did. Engineers are also hard at work testing different aerobraking materials. They have extreme temperatures to contend with, and Venus’ atmosphere is also high in reactive atomic oxygen. Luckily, the ESA has a facility that can generate atomic oxygen at energy levels that are equivalent to orbital speed. They are testing materials for insulation, antennas, star tracker elements, and more. These materials need to resist erosion while also maintaining their optical properties, which ensures the probe’s sensitive instruments work after it’s reached the intended orbit. The team expects to have the results of this testing by late this year.
When EnVision settles into its final orbit, it will map the planet in greater detail than ever before. Scientists hope that by studying Venus, which may be a victim of a runaway greenhouse effect, we could gain insights into what’s happening on Earth.
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- NASA Captures First Glimpse of Venus’ Surface in Visible Light
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