Current consensus holds that the next logical place for humans to explore is Mars. Its atmospheric composition and average temperatures make it the second most hospitable planet in the solar system after Earth. Moreover, both planets have large polar caps, which consist primarily of water ice.
Venus, on the other hand, is incredibly harsh, with toxic clouds of sulphuric acid, 92 atmospheres of pressure and temperatures reaching around 465 °C. For these reasons, it will probably be a very long time before we step on the Venusian surface.
But what about staying in the atmosphere? Dale Arney and Chris Jones from the Space Mission Analysis Branch of NASA’s Systems Analysis and Concepts Directorate at Langley Research Centre propose establishing a one-year-long – or even a permanent – base in the upper atmosphere of the unforgiving planet.
“The vast majority of people, when they hear the idea of going to Venus and exploring, think of the surface, where it’s hot enough to melt lead and the pressure is the same as if you were almost a mile underneath the ocean,” said Jones. “I think that not many people have gone and looked at the relatively much more hospitable atmosphere and how you might tackle operating there for a while.”
The proposed mission, named HAVOC (High Altitude Venus Operational Concept), would consist of several phases, designed to ensure the safety of human astronauts and the eventual success of the mission itself. The first phase would consist of robotic exploration, followed by a 30-day crewed orbital mission. Provided these went smoothly, a crew would be sent out to the atmosphere for 30 days and then for a whole year, with the possibility of permanent habitation.
Evan Ackerman, reporting on the project for IEEE Spectrum, writes: “At 50 kilometres above its surface, Venus offers one atmosphere of pressure and only slightly lower gravity than Earth. Mars, in comparison, has a “sea level” atmospheric pressure of less than a hundredth of Earth’s, and gravity just over a third Earth normal. The temperature at 50 km on Venus is around 75°C, which is a mere 17 degrees hotter than the highest temperatures recorded on Earth. It averages -63 °C on Mars, and while neither extreme would be pleasant for an unprotected human, both are manageable.“
The most intriguing things about the mission are the helium-filled, solar-powered airships, proposed by Arney and Jones. The crewed vehicle would be 130 metres long with solar panels at the top and living quarters on the bottom. For both entering Venus’ orbit and returning to Earth the astronauts would use an ascent robot.
“It would take a substantial policy shift at NASA to put a crewed missions to Venus ahead of one to Mars, no matter how much sense it might make to take a serious look at HAVOC,” remarked Ackerman. “But that in no way invalidates the overall concept for the mission, the importance of a crewed mission to Venus, or the vision of an eventual long-term human presence there in cities in the clouds.”