Colonizing Venus

Monday, October 24th, 2016

Colonizing Venus may be easier than colonizing Mars:

In many ways Venus is the hell planet. Results of spacecraft investigation of the surface and atmosphere of Venus are summarized by Bougher, Hunten, and Phillips [1997]:

  • Surface temperature 735K: lead, tin, and zinc melt at surface, with hot spots with temperatures in excess of 975 K
  • Atmospheric pressure 96 Bar (1300 PSI); similar to pressure at a depth of a kilometer under the ocean
  • The surface is cloud covered; little or no solar energy
  • Poisonous atmosphere of primarily carbon dioxide, with nitrogen and clouds of sulfuric acid droplets.

However, viewed in a different way, the problem with Venus is merely that the ground level is too far below the one atmosphere level. At cloud-top level, Venus is the paradise planet. As shown in figure 2, at an altitude slightly above fifty km above the surface, the atmospheric pressure is equal to the Earth surface atmospheric pressure of 1 Bar. At this level, the environment of Venus is benign.

  • above the clouds, there is abundant solar energy
  • temperature is in the habitable “liquid water” range of 0-5OC
  • atmosphere contains the primary volatiles required for life (Carbon, Hydrogen, Oxygen, Nitrogen, and Sulfur)
  • Gravity is 90% of the gravity at the surface of Earth.

While the atmosphere contains droplets of sulfuric acid, technology to avoid acid corrosion are well known, and have been used by chemists for centuries. In short, the atmosphere of Venus is most earthlike environment in the solar system. Although humans cannot breathe the atmosphere, pressure vessels are not required to maintain one atmosphere of habitat pressure, and pressure suits are not required for humans outside the habitat.

It is proposed here. that in the near term, human exploration of Venus could take place from aerostat vehicles in the atmosphere, and that in the long term, permanent settlements could be made in the form of cities designed to float at about fifty kilometer altitude in the atmosphere of Venus.

On Venus, breathable air (i.e., oxygen-nitrogen mixture at roughly 21:78 mixture ratio) is a lifting gas. The lifting power of breathable air in the carbon dioxide atmosphere of Venus is about half kg per cubic meter. Since air is a lifting gas on Venus: the entire lifting envelope of an aerostat can be breathable gas, allowing the full volume of the aerostat to be habitable volume. For comparison, on Earth, helium lifts about one kg per cubic meter, so a given volume of air on Venus will lift about half as much as the same volume of helium will lift on Earth.

Settling Venus sounds oddly feasible:

In the long term, permanent settlements could be made in the form of cities designed to float at about fifty kilometer altitude in the atmosphere of Venus.

The thick atmosphere provides about one kilogram per square centimeter of mass shielding from galactic cosmic radiation and from solar particle event radiation, eliminating a key difficulty in many other proposed space settlement locations. The gravity, slightly under one Earth gravity, is likely to be sufficient to prevent the adverse affects of microgravity. At roughly one atmosphere of pressure, a habitat in the atmosphere will not require a high-strength pressure vessel.

Humans would still require provision of oxygen, which is mostly absent from the Venusian atmosphere, but in other respects the environment is perfect for humans (although on the habitat exterior humans would still require sufficient clothing to avoid direct skin exposure to aerosol droplets).

Since breathable air is a lifting gas, the entire lifting envelope of an aerostat can be breathable gas, allowing the full volume of the aerostat to be habitable volume. For objects the size of cities, this represents an enormous amount of lifting power. A one-kilometer diameter spherical envelope will lift 700,000 tons (two Empire state buildings). A two-kilometer diameter envelope would lift 6 million tons.

So, if the settlement is contained in an envelope containing oxygen and nitrogen the size of a modest city, the amount of mass which can be lifted will be, in fact, large enough that it could also hold the mass of a modest city. The result would be an environment as spacious as a typical city.

The lifting envelope does not need to hold a significant pressure differential. Since at the altitudes of interest the external pressure is nearly one bar, atmospheric pressure inside the envelope would be the same as the pressure outside. The envelope material itself would be a rip-stop material, with high-strength tension elements to carry the load. With zero pressure differential between interior and exterior, even a rather large tear in the envelope would take thousands of hours to leak significant amounts of gas, allowing ample time for repair. (For safety, the envelope would also consist of several individual units).

Solar power is abundant in the atmosphere of Venus, and, in fact, solar arrays can produce nearly as much power pointing downward (toward the reflective clouds) as they produce pointing toward the sun. The Venus solar day, 116.8 terrestrial days, is extremely long; however, the atmospheric winds circle the planet much more rapidly, rotating around the planet in four days. Thus, on the habitat, the effective solar “night” would be roughly fifty hours, and the solar “day” the same. This is longer than an Earth day, but is still comfortable compared to, for example, the six-month night experienced in terrestrial near-polar locations. If the habitat is located at high latitudes, the day and night duration could be shortened toward a 24-hour cycle.

Comments

  1. Bomag says:

    “Oddly feasible” is an apt phrase. It seems within the realm of the possible.

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