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I'm a big fan of the floating aerostat concept developed by Geoffrey Landis for colonizing Venus. But how would you supply a floating base?

It would be an awfully small target to aim a vessel at. The Space Shuttle managed to make it to a runway - but it needed a runway. The base would not be a heavy or rigid object capable of assisting much in vehicle braking. The winds would be greater than hurricane force all the time. At the height of the clouds, about 60 to 70 km above the surface, they are measured at roughly 300 to 400 km/h. The base would be carried along by these winds, stationed at a height of about 50 km. What sort of vessel and approach can deal with those conditions?

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    $\begingroup$ This paper by Landis examining Venusian robotic high-altitude airships mentions balloon-based colonization, but does not seem to address resupply. $\endgroup$ – Jerard Puckett Jan 10 '15 at 17:48
  • $\begingroup$ I would assume you'd need very precise calculations, much like are needed to get anywhere in the solar system. You need to account for the date and time (Earth and Venus' position relative to the sun, Earth and Venus' rotation respectively), the latitude and longitude of both points on the planet, and the altitude of the station. Small target indeed, very complicated with a multitude of factors, but totally doable. I mean, we landed people on the moon and brought them back. That seems pretty crazy too. $\endgroup$ – Premier Bromanov Jan 10 '15 at 19:52
  • $\begingroup$ "the wind velocities would be very high, and the base would be a moving target" The base could be stationary relative to the wind. In any atmosphere, you can use airfoils to alter the path of the vehicle. So using wings to maneuver a space vehicle to land on a platform that has no cross-wind should be relatively easy. Significantly easier than landing a plane on an aircraft carrier, which will usually be moving relative to the wind (and pitching).. $\endgroup$ – Andrew Thompson Jan 10 '15 at 23:19
  • $\begingroup$ @AndrewThompson - i updated considering your comments. At the speeds involved, and in mid-air 50 km above the surface, buffeting and cross-winds must be a big deal. $\endgroup$ – kim holder Jan 27 '15 at 16:55
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    $\begingroup$ The floating base will be large, and probably so large that it will only be stationary relative to the average wind. There will be a varying residual component. $\endgroup$ – MSalters Jan 28 '15 at 14:33
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The winds are believed to be relatively constant, so the speed of the outpost relative to the surface should not be a factor. If there are major wind shears at that altitude, then the outpost has other problems. In fact, landing on something that naturally moves with the wind is easier than landing on a runway that is fixed relative to the wind. A runway will often have crosswinds, whereas a floating outpost cannot.

The Shuttle could land on a little runway in Florida entering from orbit, so the same approaches (literally) could be used at Venus. Landing at 1 bar at Venus would be a lot like landing at 1 bar at Earth. You can imagine many approaches depending on the mass of the supplies, such as steered parachutes.

The heat shield will need to be beefier, depending on if you are entering from a hyperbolic approach or from orbit.

The vehicle could use retrorockets to arrest the final approach speed. Shuttle approach speeds were about 100 m/s, which isn't a huge amount of $\Delta V$.

I don't think that this is a problem we're going to have to solve anytime soon.

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According to Colonization of Venus, by Geoffrey A. Landis (2003), most resources necessary for sustaining the colonies will be accessed in situ.

A permanent settlement will need access to the resources required for human life and for greenhouses to provide food and oxygen, and the atmosphere of Venus has these in abundance. Atmospheric carbon dioxide and nitrogen are a plentiful resource. Along with hydrogen reaped from condensing atmospheric sulfuric acid droplets, the basic elements needed for human survival can be found in the atmosphere.

A settlement will require structural and industrial materials as well. These materials, such as silicon, iron, aluminum, magnesium, calcium, potassium, sodium etc. can be mined from the surface material, which is apparently primarily a basaltic silicate. Access to the surface is relatively simple from an aerostat, since the thick atmosphere allows flight by airplanes (Landis 2001) or balloons (already demonstrated on Venus during the Russian VEGA mission [Bougher, Hunten and Phillips 1997]).

As Nick2253 points out in his comment below, the surface may be accessible enough, but conditions for mining are extremely challenging. Air pressure at the planet's surface is about 92 times that at Earth's surface, while temperatures run at least 462$^o$ C (864$^o$ F). Perhaps by the time such colonies exit the technology could be hardy enough, but it's a good bet many such materials will have to be imported.

With sufficient hydrogen and all that CO2, via the Sabatier reaction, comes methane, useful as fuel.

Breathing oxygen for life support can be easily provided by separation of oxygen from atmospheric carbon dioxide, either by zirconia electrolysis or by Sabatier processes.

Landis uses breathable air as part of his lifting support.

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.).

I can imagine it as living in a bubble with a partially dirt deck where the tomatoes grow.

I don't think it's speculation that cargo ships with supplies of LOX, cargo containers of ice, and the mail, among other things, would spring up to service such floating Venusian colonies. The logical infrastructure (to my mind) would be "space supertankers" that are captured into low Venus orbit, serviced by optimized craft designed to ferry goods from orbit to aerostat.

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    $\begingroup$ If I'm lucky, I'll still be around when they ship the first 100 metric ton block of ice to one of our neighboring planets. $\endgroup$ – Jerard Puckett Jan 10 '15 at 21:08
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    $\begingroup$ Mining on Venus is a much more significant challenge than Landis makes it out to be. The incredible pressure and temperature found on the surface significantly limits our options. In fact, I don't know that we are even remotely close to having technology that would let us do this. $\endgroup$ – Nick2253 Jan 27 '15 at 18:55
  • $\begingroup$ @Nick2253 From what I understand the pressure on the surface corresponds to the pressure found in the earths ocean 1 mile or so down. We currently drill with oil platforms far beyond that depth. Perhaps we could drop explosives down. Then drop a metal tool that scoops up rubble using a simple balloon mechanism that doesn't require electronics or sensitive equipment. So a ballon would pull up again the scooped up rocks. $\endgroup$ – Erik Engheim Aug 16 '15 at 22:36
  • $\begingroup$ @AdamSmith You're missing the temperature part. Part of why we can drill so deeply in the ocean is we have a huge heat sink to absorb the drilling heat. Not only do we not have that luxury on Venus, we'd have to find a way to actively cool our drill to prevent it from melting. $\endgroup$ – Nick2253 Aug 17 '15 at 23:39
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I think we can assume the problem of landing is solved by having bases there in the first place. The NASA HAVOC suggestion has ships inflate balloons quickly after entering atmosphere, thus they float at desired altitude.

Next problem is how to do this cheaply and efficiently, if anything like that can be said about space. Asteroids apparently are very preferable to put in Venus orbit, so one would I assume get supplies from stuff mined from asteroids orbiting Venus.

Aerobraking

When something is in orbit it goes at high speed so getting it down requires reducing that speed. Using rockets is expensive but since Venus has a thick atmosphere aerobraking is a cheaper way to do it.

Heat shields

Heat shields can be made from readily accessible resources in space. I've read of one approach of using disposable heat shields one just wraps around a package and it burns up eventually by the time the package is delivered.

Regenerative Aerobraking

Another cool approach is utilizing the aerobraking for energy generation. An enormous amount of energy is released when lowering orbit, which could be utilized. A paper by Robert W. Moses discuss this.

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