JP Aerospace are using hybrid Chemical/Electric propulsion, not conventional Ion engines.

Build a bunch of balloons, each with it's own freezer that would siphon in carbon dioxide and freeze it into huge blocks of dry ice. These blocks would be shot at high speed deep into the Venusian crust.

Or instead of dry ice, these balloons could create diamonds and drop them onto the surface.

The sulfuric acid will no doubt be the basis of the cloud cities' economy and life support systems. I mean, what's the number one industrial chemical in the world? Sulfuric acid. It's needed to make just about everything it seems.

Energy? No problem. Solar, or simply using heat siphoned from below.

My best guess is that they don't actually mean *orbit* in the sense of being high enough and fast enough to circle the globe without power, and will eventually reveal that they're marketing powered upper atmosphere airships as substitutes for orbital satellites. That kind of dishonesty leads me to look elsewhere regardless of the other differences…Bigelow Aerospace would be a good bet. They've got experimental habitats in orbit, and have been doing well at proving out the technology.

A version for operating in the Venusian atmosphere would have thinner walls, lacking the need to hold in the same internal pressure and protect from micrometeorites, simplified thermal control systems due to the more moderate environment, and possibly coatings to resist the sulfuric acid in the upper atmosphere of Venus. That latter is not actually particularly hard to accomplish, the current materials (largely Vectran, apparently) might already be sufficient.

Same goes for terraforming Mars, by the way. You can bombard the poles with comets or nukes and spend centuries building up oxygen, and you get a planet with a thin, cold atmosphere which will require continued maintenance. Or you can build domes that get you more Earthlike environments than terraforming could ever create, and do so from the beginning, and mine the polar ices and comets/asteroids.

Really, due to the low gravity, weather, and reduced sunlight, you're better off with orbital habitats where you can achieve Earthlike spin gravity and use mirrors to concentrate sunlight. The advantages of Venus are Earthlike gravity for small, non-rotating habitats, an environment with Earthlike temperatures and pressures and protection from radiation and micrometeorites reducing structural mass and the consequences of a breach (seal the compromised area off, then put on hazmat suits and patch the breach), plentiful availability of nitrogen (which Mars or orbital habitats would need a constant supply of), and sunlight for crops without concentrator mirrors.

Terraforming is a waste of time and effort. It would require an enormous investment of resources and would require constant maintenance. The atmosphere of Venus is a resource, not an obstacle.

Adam: the winds are extremely variable in latitude and altitude. The velocity you gave was for the cloudtop winds in the middle latitudes. At the altitude a habitat is likely to occupy, windspeed is less than half that. At other latitudes, it will be even lower.

However, if heading upwind to stay in sunlight is impractical, it is still very possible to cast a drag anchor into the slow-moving lower atmosphere to stay in the sunlight longer, and move into the upper atmosphere to minimize the time spent on the night side.

Venus *is* very dry, but there's enough hydrogen to make enough H2SO4 and H20 to blanket the entire planet in an unbroken layer of clouds. Water is still the fifth most abundant substance in the atmosphere, and will concentrate in the H2SO4 clouds due to the extremely hydrophilic nature of sulfuric acid. There's not enough left to make any major bodies of water on the surface if the planet were cooled down, but there's plenty left to harvest for industry and habitats.

No magnetic field, and no ozone layer, may not be a big problem: Stay on the night side, and you don't get zapped with UV *or* charged particles *or* X-rays from the Sun. BTW: cosmic rays are (mostly) NOT gamma rays, they are extremely high-energy particles, and in any case are NOT stopped much by a magnetic field. I expect the cosmic ray flux on the night side of Venus would be similar to that on Earth. (Someone please straighten me out if this is off the mark.)

The original problem with Venus: because it was a little too hot originally, it had no water trap in the atmosphere, so it lost the hydrogen in its water due to photo-dissociation in the upper atmosphere. So it now has an excess of oxygen, which led to the CO2 smothering blanket in the air. If we could find a reaction to combine the H2SO4, and fire off the oxygen (and hydrogen, necessarily) into space straight from the upper atmosphere as this is done, then conditions could get a lot more reasonable. The big trouble: Venus does not ROTATE very much, and one side always faces the Sun, and there's too much sunlight anyway. So you'd have a hard time holding onto any water. That's the big deal-breaker for anything but the most drastic terraforming approaches.

A few points.

Firstly, Landis acknowledges earlier writers in his original paper – he merely updates the concept somewhat.

Secondly, the winds on Venus at roughly the level suitable for a colony go around the planet in roughly 4 days, so the effective day is much shorter than the 117 earth-day solar 'day'.

Industrialising Venus would motivate investment in floating facilities there. The main product would be either nanotubes or stabilised carbonia – so much more carbon in Venus's atmosphere than the whole asteroid Belt, and a lot of nitrogen too. The planet is very, very dry however – the acid clouds don't amount to very much hydrogen or water at all.

Because the atmosphere has raw materials for construction and building breathable atmosphere, and because the planet provides gravity that you'd otherwise need a large rotating habitat or tether-and-counterweight system to achieve, and a human-friendly temperature range that removes the need for complex thermal control systems. Venus is effectively the only other source of nitrogen in the inner system aside from Earth itself, and although Venus is very dry, the atmosphere does contain water, and sulfuric acid which can be converted into water or itself used in industrial processes. And the atmosphere is primarily CO2, which can provide carbon for polymers.

Once bootstrapped, small supplemental shipments of minerals and machinery would allow enormous expansion, the atmosphere itself providing building material and lifting gas. The Venusian habitats could provide atmospheric gases and polymer building materials to the inner system. In reality, it is probably one of the easiest places to establish large Earthlike habitats. The plentiful sunlight, ease of constructing large habitats under Earthlike gravity, and constant supply of CO2, nitrogen, and water from the atmosphere could make it an agricultural center for supplying the inner system as well…not only with food, but also chemicals and materials derived from plants. And yes, the rocket fuel for getting things into orbit could also be synthesized from the atmosphere, and the thick atmosphere makes Venus itself one of the easiest planets to land on (even if you never actually touch land).

Converting CO2 to building material sounds like science fiction, but it is a fact that plants do it all around us. They can be bred and engineered to do it faster in a higher CO2 environment, and there have been recent advances in doing it artificially, reducing CO2 to formate ions at high efficiency using electrical power:
http://arstechnica.com/journals/science.ars/2008/07/22/powered-enzyme-reduces-carbon-dioxide

The enzyme in question has problems with exposure to oxygen…but oxygen is rather lacking in the atmosphere of Venus.

"Or if you're hellbent on being in Venus's atmosphere, build a huge tower a hundred miles tall and lower it to the surface, then put the city on it."

The tower/beanstalk concept is entirely unworkable on Venus. It's barely doable on Earth, and Venus simply doesn't rotate fast enough (243 days per rotation) to hold an elevator or tower up. However, this has its benefits…sunrise to sunrise is about 117 days, and it would be quite feasible for a habitat to circle the globe (perhaps powered by solar-thermal jet engines) in that time, staying in continuous sunlight. The greater intensity of sunlight and the lack of a night period would make solar power far more effective.

Use in situ resources to build a geodesic sphere with a diameter measured in kilometers. The struts and suspension cables should probably be CNT's for their strength/weight properties. Filled with Earth's atmosphere it will float easily. People live on the inside of the sphere. With a wide vista and artificial day and and night cycles there is no need for windows.

The outer shell would be photovoltaic, with a regenerative glass or similarly transparent sulfur shield. Venus gets more intense sunlight than Earth; there would be no shortage of power.

Link 3 or more of these spheres together in triangle formations for stability so that wind or minor mass movements within the sphere won't make them roll.

Why go? Because I feel like it. Join me if you want, stay on Earth if you prefer. Doesn't matter to me.

That's right, because the whole world revolves around you and your empty-headed consumer-driven "needs", right? Why bother to do anythig truly spectacular if you can't get a flying car out of it? Let's stop all progress and imagination and dreams of something bigger until DAVE bloomin' S gets his precious flying car.

And people wonder why I want to see the human race wiped out..

I'd love to terraform Venus.. and then populate it with a race of heavily-armed robots with orders to shoot humans on sight. That would be awesome. I'd leave your flying car there for you to go pick it up.

(1) This definitely is not a new idea. At least a half dozen writers have spoken of similar things. While I am by no means a famous writer, I wrote about this exact same thing in various internet forums over a decade ago.

(2) Eventually, it may be economical to extract rare resources from Venus, presuming they can be found nowhere else more cheaply. But that question is far from settled.

(3) It seems that a unmanned operation, at most, would be far more practical on just about every level, barring very unusual discoveries on Venus into the foreseeable future.

Why why not send a floating surveyor?

… just a thought.

I wouldn't be so pessimistic if I were you.

Nanotech has come a long way in a short time and in the least the most primitive type of derivative innovations which would be needed to accomplish terraforming will likely be developed in the short term (probably 2015 to 2020).

On the nanotech side, microbial artificial life has already been created in labs. Advancing and engineering that artificial life to terraform is not as far off as you might think.

On the natural side, reprogrammed bacteria is already in use making such things as biofuels. Reprogramming bacteria to terraform either in large number or substantially larger form is also very possible in the short term.

Who knows maybe these critters can be engineered to act as safety nets for unfortunate falling Venusians.