Aerostat on Venus vs Surface Colony on Mars

[Algren]

Idk where i picked this up, but there is one other plausible colony destination for humans: Venus.

After a few trips on the net, I've come to the "Aerostat on Venus" side instead of a colony on mars. I'll mention some of the reasons I've picked up as to why:

1. Tons of CO2, we can use that.
2. Earth-like gravity and pressure at 50km: So deltaP-catalysed explosions are not at risk there on venus.
3. Radiation shielding by Venus' atmosphere, but i read somewhere that few meters beneath the Mars surface would also give a similar shielding.
4. The atmosphere at Venus at 50km altitude is more hospitable than that of Surface Mars.

I've tried to look for data such as density of the Venus atmosphere at that altitude, climate of venus etc. but it seems like there's not much data. What are the prime reasons for opting Mars instead of Venus? Hype and lack of data are not viable reasons, and shouldn't be.
I'm also unable to find proper side by side comparisons of the two possibilities.

 

[mathman]

Venus is very hot. I believe it is a lot easier to heat things up, rather than cool things down, to make it habitable.

 

[Bandersnatch]

Humanity is also somewhat capable of building free standing structures, or even digging underground, but it has never actually built a habitat floating in air (let alone in corrosive atmosphere).

 

[Algren]

Venus is very hot. I believe it is a lot easier to heat things up, rather than cool things down, to make it habitable.

At the 50km hieght, where pressure outside and inside is the same, the temperature is 0-80 degree celsius. Basically, a human can survive there on venus at 50km longer than on mars' surface. We won't even touch the surface of venus, that's not the aim.

Humanity is also somewhat capable of building free standing structures, or even digging underground, but it has never actually built a habitat floating in air (let alone in corrosive atmosphere).

Corrosion isn't as big of a problem as pressure differences are. Explosive decompression(can be caused by even a small crack in the settlement wall) can wreck a settlement in Mars and everybody could die instantaneously(airlocks etc. are hence needed). Corrosion is a very slow process, and a simple paint/repaint on our venus settlement can fix the issue. If there is a crack on the venus settlement balloon, it will not explode, and the air will escape very slowly.

A hole on a Mars settlement is like making a hole in a filled balloon(and you are living inside that balloon). A hole on a venus floating settlement is like a keyhole of a enclosed room with a closed door. Guess which is safer?

Edit: When it comes to the inexperience of humans to build a floating habitat, that's a different issue. One has to proceed on that direction and create the required tech.

About data on venus: There have been very very few orbiter missions to venus after the 1980s. Before the 1980s and during, the soviets were crazy about venus: but still we don't seem to have their data. Only 3 orbiter missions, 2 japanese and one european, have been successful since 2000.

 

[DrStupid]

We won't even touch the surface of venus, that's not the aim.

That's a strong limitation compared to a habitat on Mars.

If there is a crack on the venus settlement balloon, it will not explode, and the air will escape very slowly.

If a pressurized habitat on Mars is made of suitable materials the air would also escape very slowly in case of a leakage. But in contrast to a floating habitat on Venus it wouldn't sink in such a case.

 

[Algren]

That's a strong limitation compared to a habitat on Mars.

Why is it a "strong limitation". I understand that humans are an animal which walk on land and cannot fly, but now we can, and we should.

If a pressurized habitat on Mars is made of suitable materials the air would also escape very slowly in case of a leakage. But in contrast to a floating habitat on Venus it wouldn't sink in such a case.

The venus habitat would sink, no doubt. Such things could be fixed and the venus habitat can be refuelled.
Let me tell you how low the pressure on mars, is, it's 6/1000 compared to that of earth's. So, a hole in ISS currently in orbit around the Earth woul be an almost similar scenario to a hole on a Mars colony, whatever be the material. (Rate of leakage of gas depends on only 2 things: Area of orifice, and pressure difference)

 

[rootone]

The surface of Venus still remains uninhabitable in this scenario, and any useful resources on it are not easily available.
What exactly would be the point in a colony which at best can maintain it's functioninal state for a few years

 

[Algren]

The surface of Venus still remains uninhabitable in this scenario, and any useful resources on it are not easily available.

Resources is one big issue in case of venus. But when it comes to energy, that too solar, venus receives almost 240 times more energy than mars. Plus, we have tons of carbon dioxide to feed ourselves/the plants, there may be several efficient and light technology which can convert carbon dioxide to oxygen.
Keep this in mind though: Harvesting and processing resources takes a hell lot of energy.

NASA seems to be doing something about it with HAVOC.

 

[256bits]

Compared to Mars, Venus actually has several big advantages. Firstly, power would be no problem. With an array of solar panels on the airship, explorers would have all the power they’d need. Venus gets 40% more solar energy than Earth and 240 times more than Mars. Since there would be an atmosphere present, the airship could use electrical power to spin turbines for propulsion.

That's what the article says, yet I am wondering where from they got their figures of solar energy or what they are comparing.

This chart shows the solar flux the planets receive from the sun.

At the Earth's surface, the solar irradiance is about 1000W/m^2 ( less due to due to reflection, dust etc. in the atmosphere ) for a surface perpendicular to the sun's rays.
Not sure what a solar panel could collect for Venus at 50 mile height - is the atmosphere totally clear at that altitude??
Mars has a low atmosphere, so on a good day ( no dust storms ) a panel might be able to collect the nearly the 593 W/m^2.

                                 Venus    Earth    Mars
Distance from Sun (A.U.)           0.72      1     1.52
Flux, W/m2                         2643   1370    593
Albedo                            0.8       0.3     0.22
Effective Temperature, K          220      255     212
Actual observed Temperature, K     730      288    218
Greenhouse Effect, K               510       33      5

http://www.atmos.washington.edu/2002Q4/211/notes_greenhouse.html

You will notice in the Table above that even though Venus receives more solar energy than the Earth is, its effective temperature is colder. This is due to the high albedo on Venus (0.8): 80% of solar radiation is reflected to space and only 20% is absorbed by the surface (see Figure 3-1 in textbook for a comparison of albedoes of the three planets). The actual temperature at the suface of Venus is much warmer: 730 K ! The enormous greenhouse effect of 510 K (=730-220) on Venus is due to high levels of CO2 in its thick atmosphere. Mars has a much weaker greenhouse effect because it's atmosphere is much thinner than that of the Earth.

 

[mfb]

The upper clouds are at a height of ~60-70 km, at a pressure well below what we have at sea-level on Earth. They reflect ~3/4 of the light and scatter the rest, so solar power at 50 km height works worse than solar power on Mars. The intense winds are another issue. Add some lightning to this.
You can harvest CO2 both on Venus and Mars, on Mars you can also obtain various other elements from the surface, which is challenging on Venus (well, there nitrogen and sulfur around). Where would you get the material from to repair corrosion?
A few meters below the surface of Mars you are shielded against cosmic radiation, and the risk of sudden pressure loss is limited to airlocks.

We have the technology to keep pressurized modules in a vacuum (or nearly vacuum) operational for 15+ years. We don't have floating stations surrounded by sulfuric acid.
Both planets are interesting, but with current technology Mars is easier.

 

[sevenperforce]

How bad is the sulfuric acid problem?

I mean, any sulfuric acid problem sounds pretty bad. But at the preferred 50 km altitude, is there enough sulfuric acid to cause problems? As I understand it, you could walk around "outside" on a platform at 50 km on Venus as long as you had a mask to protect your mouth, eyes, and nose.

 

[DrStupid]

Why is it a "strong limitation".

rootone already answered this question.

So, a hole in ISS currently in orbit around the Earth woul be an almost similar scenario to a hole on a Mars colony, whatever be the material.

The leakage in the MIR station (after a collision with a Progress transporter) showed that such problems can be handled. There was no explosive decompression, nobody died and finally the damage was fixed and the affected module refilled. I do not see the problem. A habitat on Mars could be fixed and refilled even after complete decompression. A habitat on Venus would be doomed in such a situation.