Venus, the second planet from the sun, seems like the last place one would want to send human beings. The surface of the cloud-shrouded planet is a hellscape.
On Venus, temperatures reach 900 degrees Fahrenheit and atmospheric pressure is 90 times that of Earth. There are thick clouds of sulfuric acid and a carbon dioxide atmosphere. The surface is marked by volcanoes and craters. There is not a drop of water in any form.
Early science fiction imagined a quite different landscape beneath the Venusian clouds: lush tropical rain forests, oceans and exotic lifeforms, perhaps some intelligent. But the first space probes of the 1960s, starting with the Mariner 2 flyby mission and including a series of Soviet Venera landers, revealed the awful truth. The environment of Venus may have been benign, with surface water, 2 billion years ago, but a runaway greenhouse effect gradually created the hellish Venus that exists today.
However, the Space Mission Analysis Branch (SMAB) at NASA has developed a concept that might allow humans to visit Venus, called the High Altitude Venus Operational Concept (HAVOC). The concept involves sending robotic probes and eventually crewed vehicles to the Venusian atmosphere 50 kilometers above the planet’s surface.
A spacecraft would enter the atmosphere of Venus and, after slowing down using aerocapture maneuvers, would deploy an inflatable airship. The vehicles would then ride the winds of the upper atmosphere of Venus. The spacecraft would contain instruments that would examine both the atmosphere and the surface of the second planet from the sun.
As it turns out, while the Venusian surface is similar to our ideas of what Hell must be like, the upper atmosphere is relatively benign, with temperature, gravity, pressure, and even radiation protection similar to Earth’s surface. Using airship technology, 50 kilometers above the Venusian surface is about as Earth-like as one can get elsewhere in the solar system.
If the airship concept is approved for funding, the first expedition to the Venusian atmosphere would likely be uncrewed, with a suite of instruments. The mission would prove the concept of deploying the airship after entering the atmosphere and sustaining the probe over weeks and months.
An alternative to the airship concept is being developed by Northrup Grumman: the Venus Atmospheric Maneuverable Platform which is described as an “aeroshell-less hypersonic entry vehicle that transitions to a semi-buoyant, maneuverable, solar-powered air vehicle for flight in Venus’ atmosphere.” It would enter the atmosphere of Venus like a “falling leaf” and then fly about, gathering data, for a planned mission of close to a year.
The HAVOC concept also suggests that a crewed mission would be possible. The airship would take a habitat and an ascent vehicle with two astronauts who would then ride the winds of Venus for about a month before leaving and returning to Earth. The study suggests that the mission could be mounted more easily than a human mission to the Martian surface.
Are there advantages to sending human explorers to the upper atmosphere of Venus, as opposed to a robotic probe? No doubt, real-time observations by trained scientists on the scene have a certain value. The crew of the Venus airship could also remotely operate rovers on the surface of Venus, which would more resemble tanks than the relatively fragile models now rolling across Mars.
Besides the technological spin-offs that mounting a crewed mission to the Venusian upper atmosphere might entail, the main justification may just be the sheer audacity, indeed glory of such a mission. Will those intangible benefits justify the considerable cost of sending humans to Venus?
People have walked on the moon and will do so again. People will journey to Mars. But the first people to venture to Venus could soar like leaves on the wind.
Mark Whittington is the author of space exploration studies “Why is It So Hard to Go Back to the Moon? as well as “The Moon, Mars and Beyond.”