Part of my series on countering misconceptions in space journalism.
From time to time, one reads of studies promoting the concept of crewed missions to Venus. Usually this crops up as part of the perennial debate about going to the Moon, or Mars, or an asteroid, or a deep space space station, or nowhere at all.
“What about Venus?” cry the sorts of people who would jump into a Mac vs PC argument advocating Solaris while fondling a beard that reaches their knees. Reader, this could be me, except I lack the necessary hair production talent.
The basic idea is that Venus requires slightly less delta-V than Mars to get to, has a much thicker atmosphere, more solar energy, and much more frequent launch windows. Capitalizing on all that was the Soviet Venera program, which launched dozens of orbiters, landers, and balloons to Venus during the 1960s, 1970s and 1980s.
While Mars’ surface is a frozen poisonous radioactive airless hellscape, Venus’ surface is rocky, volcanic, and a mere 462 C at 93 atmospheres, supercritical CO2 atmosphere with a side of sulfuric acid. This is so hot that future rovers will depend on mechanical computers/cameras/radios, because ordinary computers will melt. Obviously, sending humans to the surface of Venus is a non-starter.
That’s okay, say Venus exploration advocate(s), we’ll have a giant airship. Somehow we’ll perform EDL at 12km/s, deploy something a hundred times the size of the Hindenburg in a couple of minutes, float around for a few months, then drop a Earth Return Vehicle (ERV) the size of a Saturn V off the bottom, light the engines, and return home.
I love this stuff. Let’s dig in a bit.
I have a future blog planned on airships, because they’re awesome. Let’s rebuild the Hindenburg but with mylar, nylon, carbon fiber, and helium. We can put a thousand people on it. It will be slow, crowded, and a human petri dish, just like a cruise ship. It will also be perilous and too far above the ground, like a plane. And awesome!
How will this work on Venus? I have no idea. I think one could make an argument that a pressure-stabilized airship deployed in space could perform entry, descent, and landing (EDL) without substantial heat shielding due to its very low ballistic coefficient. Let’s say this is possible. After a 6 month trip to Venus, the crew would then hang out in a small capsule suspended from a giant balloon. Let’s hope they like confined spaces.
Inside this balloon, they can drift on Venus’ winds around the planet while they wait for the return launch window to line up. From their perch maybe 50 km off the ground, they’ll have a great view of the sulfuric acid clouds which, when the balloon gets blown around to the night side of Venus (its days are 117 Earth days long), will rise up and engulf the balloon.
While it is true that Earth-Venus requires slightly less delta-V than Earth-Mars, the reverse is not the case. Venus is nearly the size of Earth. With an escape velocity of 10.36km, the ERV will need to be comparable in size to a Saturn V. Fully fueled, it will weigh about 3000 T, which exceeds the working load of the Hindenburg by only a factor of 300. This monster rocket will also need to be launched somehow from a balloon about the size of Manhattan. Maybe it can be dropped and then fly to the side?
Bringing a 3000 T ERV from Earth, in addition to the gigaZeppelin, is a big resource drag. Perhaps its mass could be reduced somewhat by synthesizing its oxidizer from the ambient Venusian atmosphere. If the airship lacks the propulsion to remain on the day side of the planet, the chemical plant will require a substantial nuclear reactor to provide power. Further, as the ERV’s tanks are filled, the airship will somehow have to generate more lift (thousands of tonnes more) to remain buoyant. Lifting gasses can’t be synthesized from ambient CO2 atmosphere, so we’d better make sure we bring enough helium to last the entire mission.
I’ve spent years pondering the head-scratching difficulty of getting humans to and from Mars, building cities there, and solving problems. I think it’s possible.
A human exploration mission to Venus is in another category entirely, and all to get a crew of two from a monotonous space flight to a monotonous balloon flight to a monotonous space flight home. All it requires is about a thousand times the mass relative to a Mars mission, and a generous handful of technical miracles.
Casey Handmer's blog 
Disclaimer first: I’m just a graphic designer. But I think about the Venus problem a lot.
Venus is the golden prize of the solar system. It’s the only planet with gravity close to Earth’s (.91).
Atmosphere is mostly carbon dioxide (96.5%) and nitrogen (3.5%). The CO2 creates the unlivable pressure and greenhouse gas blast furnace.
Here’s the fun fact: the amount of nitrogen is roughly equal to Earth’s. If you were to remove the CO2, strip some of its oxygen equal to 21% of the existing nitrogen, you would have the beginnings of a biosphere.
This is of course a multigenerational problem that might be achievable within the next 100 years. Or later. Who cares?
Removing the CO2 will likely require an orbiting ring structure with dangling scoopers. This can be built up from polymer made from early CO2 removal and/or shipped from Earth. Hydrogen can be obtained from the sulfuric acid. More can be harvested from the outer system.
All that excess CO2 can go into building a second, larger ring structure that would orbit Venus in 24 hours and be the right size for close to 1g or centrifugal force. Important note: I have no clue if those 2 conditions could coincide, but since one of the purposes of this blog is to debunk non-starters, here’s a chance for someone to do the math.
The ring would follow a tilted solar synchronous orbit, wide enough to never pass into Venus’ shadow. Day would be experienced when your local sector swung away from the Sun; night when it crossed back over Venus’ terminals.
This ring, while supporting millions on its own, would also be tasked with terraforming the planet below. Beyond having a livable atmosphere, the surface would also require ongoing shielding from the much closer Sun. This might be achieved by widening the original CO2 scooper ring, for instance.
Add water by harvesting comets and ice from outer system.
Again, not a scientist here. I expect we’ll move people to Mars in the next 50 years. But Venus represents a true terraforming challenge. Hopefully, humanity will bring to the project all the lessons learned from restoring our current planet of residence.
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Here’s a published Quora answer that addresses the terraforming question.
https://slate.com/human-interest/2013/09/outer-space-can-we-make-mars-or-venus-habitable.html
Need to shade the planet for 200 years to freeze the atmosphere, then eject it all with mass drivers to increase the rotation speed.
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Rather than change the rotation speed, I’m more inclined to have some kind of heat transport from the day side to the night side.
Let’s talk spinning first, though. If we have mass drivers capable of launching stuff at 10,000 km/s, we have a lot of options. Even 10 km/s would be a game changer. Anything with a mass driver on it is a super-duper rocket. We can lob stuff into a retrograde orbit around the sun so that it meets up with Venus again, and then pound it onto the surface of Venus at a nearly tangential angle. We can do it slowly, reusing the same material if we feel like. Or we can do it fast, and boil the excess atmosphere off into space. Just because we’re trying to cool Venus off in the long run, that doesn’t mean we can’t heat it up at some point in the process.
The obvious means of heat transport is to have water evaporate on the day side and rain on the night side. Probably not enough, but I would have to do actual calculations to find out. Alternatively, we could cover the planet with some kind of heat-conducting material such as the shadow square wire from Ringworld. It doesn’t exist, but neither do the relativistic mass drivers.
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Mars and lunar bases could be done almost with existing technology. The idea of Venus can be partially blamed on old sci fi? Maybe
Would much prefer the Mars option.
But I am just an interested fan I guess. I believe we need to keep pushing frontiers if only for the technology development while doing so.
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For manned spaceflight, the moon turns me on more than either Mars or Venus. It’s close, you can enjoy the view (Earth), and the sheer joy of romping around in 1/6th g has been captured on Apollo film and audio. The moon would make an awesome two week vacation, and is just around the corner in time compared to the other two, especially Venus.
I get equally excited by unmanned as I do manned missions. I want to see more of them! And I especially want to see more missions to the outer solar system. Sedna anyone?
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You think of living in blimps, then you think of floating cities, which makes you think of Cloud City in Star Wars.
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That all said, there’s actually a pretty good case for human-crewed flybys of Venus – on the path to Mars. Earth-Venus-Mars-Earth opposition type missions make for shorter total mission times and lower delta V than EME conjunction type – and enable human-in-the-loop science investigations at Venus not possible with robotic technology alone. EVE is also potentially an abort case for EVME, and an “Apollo 8” deep space test of long duration human flight – with less cosmic ray exposure and higher flight cadence than EME.
All that does not require human-piloted rendezvous with Venus, which has a more tenuous science and human-spaceflight argument, and it’s certainly not a case for human descent into the atmosphere of Venus.
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I did a deep dive on conjunction class missions and found that they actually use more dV, and have higher thermal requirements, with few benefits. https://twitter.com/CJHandmer/status/980536326763065344?s=19
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I think we at least partially agree. Conjunction has lower dV, but at the cost of total mission duration. Conjunction missions of 900 days and longer dV beats opposition missions of 500-600 days.
The question is whether the additional year you have to spend en toto, and the additional most-of-a-year you spend outside Earth’s orbit as opposed to inside it poses a greater risk/cost to deal with cosmic rays than you would need to answer the relatively easy thermal challenge of a Venus flyby.
Did you look at EVME as well as EMVE? Have you compared your study and assumptions to the Mars DRA? Is this published anywhere? Good stuff.
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Radiation exposure is higher with Venus flyby, as flight time increases by nearly a year and is much closer to the sun.
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Are your EME missions shorter than 2 years total duration? That’s the only way they’d have lower total radiation dose. Solar radiation/wind and charged particles are much easier to protect against than cosmic rays, and the closer you go to the sun, ironically the more protection you have from cosmic rays. equal time trips EVME and EME are, from the literature I’ve seen, pretty much a wash for total dose – but the solar component is easier to shield from. Staying a year at Mars ups the cosmic ray exposure substantially.
In saying the flight time increases by a year, what is your total mission time for EME vs EVME? I’m probably not reading your plots well enough.
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See my blog on radiation.
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Again, even from your look at it, it seems the radiation favorability checks out if total mission time is substantially lower for EME.
CR exposure is lower closer to the sun (which (again ironically ) makes going at solar max more favorable – the need for a storm cellar isn’t changed by one mission type over the other). It’s still not clear to me what are the total mission times you’re comparing? You say that opposition missions are longer than conjunction missions, but I see the opposite by up to over a year.
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1) Regular oxygen-nitrogen breathing mix will float in a CO2 atmosphere. No need for expensive and leaky helium.
2) O2 and N2 can be extracted from the Venusian atmosphere, either chemically or by filtration.
3) Your return rocket will be empty bags and cylinders. You fill the cylinders with CO/O propellants and the bags with O2 gas, so the assembly floats while being filled.
4) Ascent from Venus high altitude to Low Venus Orbit is about 8km/s. It takes another 3km/s to escape Venus and 0.7km/s for an Earth encounter. The ascent can be handled by a staged CO/O rocket and the in-space maneuvers by a solar-electric craft. The crew is delivered to Earth by aerobraking.
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Many good points, but low ISP requires an even huger rocket.
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1) Would the nitrogen freeze above the carbon dioxide? Wouldn’t want to lose that.
2) Do you think depressurizing the atmosphere would reduce or increase volcanic activity?
3) Why not suck up the CO2 with millions of solar-powered pumps? Seems like a lot less work that corralling irreplaceable asteroids. CO2 would be useful for shielding and other orbital projects.
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1) yes, which makes it easy to separate since it will liquefy and form oceans.
2) I doubt it will change activity much in the long term.
3) geostationary doesn’t really exist on Venus due to low rotation speed. No need to use asteroids.
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Re: 3) Ring would spin in free fall. Rotational speed would be maintained by a) angling the skimming pumps in the direction of travel and b) ejecting bursts of processed carbon towards higher collection points.
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You wouldn’t need escape velocity – just low orbit velocity, where you’d rendezvous with an orbiting return vehicle. However, this still involves something on the order of a Falcon 9. So, not as crazy as a Saturn V, but still pretty darn crazy. The big question to me is … umm … why? What is even the point? What is more pleasing about a mission where a human floats in a blimp rather than where a human floats in orbit just a bit further up?
Being in orbit offers some potentially compelling benefits for real-time remote operation of drones on the surface (compared to operation from Earth). Those drones could even be humanoid if you really want boot-prints. The same mission hardware could be used for both Venus and Mars missions, and perhaps even beyond.
But actually going down in person? Why? I know that with Mars, there are a lot of people who really just want a person to be physically walking around on Mars in person for some reason. But with Venus that’s just not going to happen. So what’s even the point?
I think it’s kind of a fun thing to ponder, because it’s weird that it’s even possible. But to seriously consider doing it? Why?
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Exactly.
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Hi Isaac. It’s been a long while!
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If we’re going to be floating around in giant not-gonna-happen balloons, why settle for Venus? Let’s go to Saturn.
“future rovers will depend on mechanical computers/cameras/radios, because ordinary computers will melt.”
I would think that we would be better off with electronics and refrigeration, although I don’t know what working fluid you use when the warm coils of your air conditioner are at 462C.
” Lifting gasses can’t be synthesized from ambient CO2 atmosphere”
If the atmosphere is CO2, then O2 is a lifting gas, right? So is CO2, if it’s warmer than the surroundings.
So maybe we’ll need a balloon as big as New Jersey instead of having it just be Manhattan-sized. As long as this is all imaginary, why not have it be as big as Alaska? You can make the envelope out of carbon fiber, made from the readily available CO2, and every atom of C gives you an O2 as a byproduct. Never mind where the energy to un-burn all that CO2 is coming from: imaginary solar panels don’t weigh anything. Or cost anything. And besides, we didn’t have to de-orbit the mass for the solar panels. We’ll beam the power down from orbit, and make the receiver out of superconducting carbon-nanotube-based unobtanium. Space-based solar power has finally found its killer app.
The return rockets wouldn’t have to even get to low orbit. They would have to get to the height of the bottom of a long tether, and the orbital angular speed of the center of mass of the tether. Only a wispy first installment of the tether would have to be brought along. The rest would be made of more carbon nanotubes made out of local CO2 un-burned with local solar power. I haven’t run any numbers, but with ISRU I’m pretty sure we can bring the cost down from absolutely impossible to still absolutely impossible.
We’ll also have nitrogen available, and maybe sulfur. For hydrogen, we’ll figure out how to capture it from solar wind out in orbit, and send it down via the tether.
Or better yet, just import it from the colony on Saturn.
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You’re good at this.
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For me, a simple country lawyer, human visitation is the MacGuffin of the discussion.
To me, the primary focus is on life detection. Once we achieve that, finding the Second Genesis is the game changer. Then we have evidence life is out there and we can collectively focus.
I remember being heartbroken when we first detected other planets, because Dr. Sagan just missed it. It was his dream to have certainty.
Having drones and airship stations for them are entirely within existing technology, and indications of the sweet spot and potential cloud life are there waiting to be explored.
This isn’t Star Ttrek and the Captain goes on there first landing party. Send the machines. If they detect or discover, then we decide what is next.
Mars and the moon will tech us how to live off world, but unless there is the overarching need to expend our energy , why bother.
Find the life first. Use the drones and robots. Then follow that good science. The rest is 1950’s fascination of walking on dead worlds.
Finding the life is much more important.
JMHO
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More seriously, if all goes well with Mars and deep space, there will come a time when Venus is only as much of a stretch as the Martian city is now, or the moon landing was in 1962. We can’t make viable plans for Venus yet, but we can have fun speculating what those plans might look like.
The surface of Venus is hot, but mechanical stuff can work there. Lead would melt, but any material that’s even kind of refractory would hold up ok.
As an energy source, solar is not ideal on a perpetually cloudy planet. It limits energy collection to altitudes above the clouds. Panels on airships are a possibility, and so is solar in orbit, but today I imagine that we’ll be better off extracting energy from the atmosphere. There’s wind shear, and there’s vertical temperature difference. On an airship you can’t do wind as an energy source, because you’re moving with the wind. Tether two airships to each other at different heights, though, and they both have wind.
But that still involves airships, which get to be ridiculously large when you try to have them carry enough mass to get anything done. I imagine we’ll be better off with insulation at ground level. Insulation needs whatever thickness it takes for the temperature difference you want: a fixed thickness as you scale up. So we will enclose volume and pay for area. That means we go big or stay home. (For the foreseeable, we’re taking option B. But it’s a whole planet full of resources, so eventually we will want it. After the moons of Jupiter, but before Jupiter itself.). Insulation doesn’t do any good unless we have some way of cooling the inside. There’s lots of cool available, a few kilometers up, and dumping heat into cool is an energy source. I still have no idea what working fluid we should use, or whether we should use thermopiles instead.
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Alternatively, even further into the very-distant-future crazy category, we could smash one of the Galilean moons of Jupiter into Venus hard enough to make another asteroid belt.
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> I imagine we’ll be better off with insulation at ground level.
There is no point in even discussing habitation at ground level. Ambient pressure matches 900 M under the sea on Earth. Only one military submarine has been produced that can even approach such pressure, in the Russian navy, that displaces almost 20k tons for 100 crew. It would take 200 Starship launches just to loft the parts for one, never mind get it all to Venus.
That’s without talking about how to pump out the heat that makes it through your insulation, or how to sink the heat from any sort of power generation system; or the lack of light during the thousands of hours of night, if you wanted to try solar. Wind is fast miles up, but sluggish on the ground.
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To my knowledge, there have been several SciFi novels which describe building floating habitats in the Venus atmosphere… one of them is “All The Stars Are Suns”… and ah… Full Disclosure: I wrote it. Here is what I envisioned…
First, why?
Answer, because it is the best place to put a biolab for genetic engineering because it is at the bottom of a damn hard gravity well to get out of. Not much is going to leave without a great deal of help.
I envision that two centuries from now, the issue of getting there is fairly easy. Drop in using capsules, parachute, then N2 balloon. Be picked up by dirigible, then safe at home… and it IS your new home, likely for life… in the ever growing floating city habitat, using the N2 lifting gas in the habitat, and the capsule and balloon material (aluminized mylar) as the source for metals… and use the atmospheric CO2 and water (what little there is) for feed stock for the rest, lots of polymer construction, much of it foamed.
Can one leave? Yes, with a lot of help, in a hybrid aircraft / rocket. Climb to very high altitude as an aircraft with no fuel and very little reaction mass aboard, using electric driven propellers powered by very, very tight beam laser or maser from space. At altitude, spend some time compressing gas for reaction mass, then up out of the atmosphere, or at least most of it on a suborbital ballistic, to be “scooped” by a rocket that makes a low pass (yes, it would intercept the atmosphere on that ballistic… but won’t wait that long) then after rendezvous, the pick-up craft fires its rockets to get both back to orbit. From there, onward to where ever using microwave sail ship.
In the story, I describe how bio-terraforming of Venus like worlds might be accomplished using genetic engineering.
Candice H. Brown Elliott aka: Seaby Brown, Author
All The Stars Are Suns
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I agree it’s excellent fodder for scifi!
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Finally, someone gets it. There will be no return for most people. It’s not about sending, scientists but colonists and they’ll stay in floating cities. Add some artificial wombs and gynoid nannies to the mix, and they’ll grow there. No consent necessary. They can have all the (VR) games, ebooks, and tv shows from Earth, though. Most people have it worse.
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I recently discovered an answer these Venus-first turtles can understand. You can walk on the surface of Mars and the Moon. That is essential when you need local hard stuff to build and expand your first settlement. That is impossible on Venus with foreseeable technology.
It also works with the Space Settlement-first crowd because you cannot live in an O’Neill colony until it is sealed with an atmosphere.
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Science should be done by robots if possible. Return missions with humans make no sense. It’s easy to agree with that. Sending humans as colonists is a goal of its own, though. Also, in the long run, Earthlings might seek freedom or low taxes one day, simply wanting to get away from Earth. Here some ideas how its done:
More ambitious plans aside, floating cities in the clouds sounds good to me. The right air pressure, temperature, gravity, some ressources, atmospheric protection against small asteroids and a lot of solar power included. Shielding from radiation seems to be the problem, which would need a solution.
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You can make a nuclear reactor for the Venus cloud-tops just by hanging a big plastic-film tube from a balloon, with a naked atomic pile inside near the bottom and a wind turbine at the top. It can supply its own lift — no separate balloon needed — if you constrict the opening at the top a bit.
The radius of the tube is chosen so that most of the radiated energy — from gamma rays, neutrons, what-have-you — is captured by the air inside, which gets hot and rises through the turbine.
This would work on gas giants, too, and on Ganymede and other moons with substantial atmospheres.
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I think the ambient temperature differential from top to bottom would be a lot more than any effect from absorbing radiation. There is a terrestrial proposal I read somewhere (?) of a windmill in a desert that uses ground heating and plastic sheets to feed winds up into a column. Another option might be some kind of giant stirling engine.
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There is no need for the tube to be longer than, say, twice its diameter, so the difference in ambient temperature between entry and around the exit is minimal. The difference between ambient and heated air temperature may be very large, limited only by the tolerance of the materials. With a PTFE fabric tube and turbine blades, that could easily be a hundred K.
The difference from the desert scenario is that nothing is heating the air outside the tube. The only hot air is inside it. The only cooling available is by expanding, which is limited by the shape of the tube except at the turbine aperture. The air inside a strictly-cylindrical tube would have almost the same density as outside air, but just have much higher pressure; that is why it can drive the turbine. Air exiting the turbine can only be replaced with cool air coming into relative vacuum at the bottom. The bottom needs mechanical support to stay open.
Note that there is no significant wind around this gadget, because it rides the prevailing wind, although it can experience gusts.
A stirling-cycle engine would eliminate any value in using a nuke; then you might as well just use solar and batteries.
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BTW, mea culpa: Ganymede has no appreciable atmosphere. But the method would work well on Titan and (maybe surprisingly) Saturn, Uranus, and Neptune, which have cloud-top gravity hardly different from Earth’s. The lifting gas on those planets can only be hot air, because the air is mostly hydrogen. On the plus side, the temperature difference can be very large, because ambient is so cold.
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“After a 6 month trip to Venus, the crew would then hang out in a small capsule suspended from a giant balloon. Let’s hope they like confined spaces.”
Why would they hang out in a suspended capsule? You’re using the blimp analogy from Earth, which is an imperfect analogy for Venus.
Earth needs a big balloon of helium or other light gas in order to float. For Venus, you need something with a total buoyancy of about 1 atmosphere to float at a level with Earth-like temperatures. A buoyancy of 2 or 3 atm would also be possible with a bit more life support.
Therefore, adjusting your partial pressures of oxygen a little, it’s completely possible to live INSIDE the balloon, not suspended in a little capsule from it.
I’m assuming the ERV is on a different blimp, and people might be staying on Venus long term (not enough return rocket space for everybody).
You could even forego the return rocket altogether (and science mission) and make this the new prison colony 😉
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