With robots tooling around the Red Planet’s surface and reporting back on conditions there, dreams of human space travel—complete with human colonies—have fixated on Mars. We've even argued about who should go. But some think we’re fixated on the wrong planet altogether: There’s a case to be made for human travel to Venus first.
On the pro side, the second planet from the Sun is closer to Earth than Mars, writes Evan Ackerman for IEEE Spectrum. On the con side: "Venus’s surface is hellish, with 92 atmospheres of pressure and temperatures of nearly 500 degrees C."
Colonists to Venus would not build on the planet's surface; they would, in theory, set up a floating "cloud city" in Venus’s atmosphere. Of course, Venus-bound missions would "require big policy changes at NASA," writes Elizabeth Lopatto for The Verge. But two scientists, Dale Arney and Chris Jones, of NASA’s Systems Analysis and Concepts Directorate at Langley Research Center in Virginia, point out that about 31 miles above the surface, the gravity and pressure is Earth-like, temperatures stay near the more manageable 167 degrees F and the colony would be more shielded from the Sun’s radiation than Mars.
In other words, it might be easier in the long run to set up a human colony on Venus. NASA calls it the High Altitude Venus Operational Concept (HAVOC) mission.
The procedure for "landing" a spaceship would be different if the atmosphere is the final destination, Arney explains to IEEE Spectrum:
Obviously, in our case, ‘landing’ would represent a significant failure of the mission, so instead we have ‘entry, descent, and inflation,’ or EDI.” The airship would enter the Venusian atmosphere inside an aeroshell at 7,200 meters per second. Over the next seven minutes, the aeroshell would decelerate to 450 m/s, and it would deploy a parachute to slow itself down further. At this point, things get crazy. The aeroshell would drop away, and the airship would begin to unfurl and inflate itself, while still dropping through the atmosphere at 100 m/s. As the airship got larger, its lift and drag would both increase to the point where the parachute became redundant. The parachute would be jettisoned, the airship would fully inflate, and (if everything had gone as it’s supposed to), it would gently float to a stop at 50 km above Venus’s surface.
Just as on Mars, a robotic crew would check out the conditions first. Then humans would arrive and live in a habitat based on NASA’s Space Exploration Vehicle. All could be part of the run up to a manned mission to Mars, Jones told IEEE Spectrum.
A energetically scored video from NASA illustrates the whole concept: