Once believed to be off limits for human exploration, NASA is considering how Venus might be better to visit than Mars
Venus has recently become a serious consideration for a potential manned mission – since it’s the closest planet, the journey would take less time, and there are more orbital windows of opportunity to go there. It has 81.5 per cent of Earth’s mass – versus 10.7 per cent for Mars – and its atmosphere would provide as much protection against radiation as Earth’s. But that atmosphere is also the reason no one has thought about going to Venus in a long time.
Venus’ atmosphere is 96 per cent carbon dioxide (CO2 ), and because CO2 traps heat from the Sun like a greenhouse, Venus’ surface has an average temperature of 464 degrees Celsius (867.2 degrees Fahrenheit), which is hot enough to melt lead. Also, because CO2 is much denser than air, the pressure at the surface is like being one kilometre (0.62 miles) underwater on Earth, while the continuous cloud cover is made of sulphuric acid. Ever since Mariner 2 confirmed the surface temperature in 1962, Venus has been firmly off the human spaceflight agenda.
Now it appears that deadly atmosphere might enable us to visit and even colonise Venus. NASA’s High Altitude Venus Operational Concept (HAVOC) is based around exploring and colonising Venus’ upper atmosphere with rocket-powered airships and flying cities. Because CO2 is so dense, the atmospheric pressure at an altitude of 50 kilometres (31 miles) is the same as Earth’s at ground level. This, and a temperature range of around 0 to 75 degrees Celsius (32 to 170 degrees Fahrenheit), makes it one of the most Earthlike environments in the Solar System. In addition, normal breathable air is buoyant at this location, so a lightweight habitat could float on the air inside it.
NASA’s study features five phases: first, robotic balloons would go and visit this sweet spot in the atmosphere and check out the conditions. Phase two would be a twoperson mission to orbit Venus for 30 days before returning to Earth, and phase three a two-person mission to spend 30 days in the atmosphere. Phase four would be two people spending up to a year in the atmosphere and phase five would be a permanent floating base.
All of HAVOC’s phases involve delivering airships to Venus; the robotic ones would be about 31 metres (102 feet) long, with the crewed ships about 130 metres (427 feet) long - almost twice the length of a Boeing 747. A HAVOC ship would be packed into an outer shell to protect it from the heat of atmospheric entry; after its parachute slows it down to less than 100 metres (328 feet) per second, the shell drops away and the airship envelope would start inflating. Once full, the airship would floa
