How do you deorbit Venus is such a way that your inflatable balloon city comes to a gentle stop, 30 miles up, and just floats there? Worse still, when people need to leave and return to Earth, how do you launch a rocket from the balloon city and return to orbit? How do visitors or pioneers deorbit and land at the floating city? If there aren't materials to effect a repair, how long until it sinks down into the hellzone? Where are materials manufactured for repairs, and how quickly could they be manufactured and sent there? If a rocket is trying to land and goes off course, does it squash the balloon city like a grape? Saying that holes can be patched is well and good, but there are some truly catastrophic failure modes that don't seem entirely unlikely.
> such a way that your inflatable balloon city comes to a gentle stop, 30 miles up, and just floats there?
Literally how floating works.
> Worse still, when people need to leave and return to Earth, how do you launch a rocket from the balloon city and return to orbit?
By launching your rocket from the ballon city and returning to orbit. (I'm struggling to see the novel problem.)
> Where are materials manufactured for repairs, and how quickly could they be manufactured and sent there?
Why is this unique to Venus versus anywhere else in space?
> If a rocket is trying to land and goes off course, does it squash the balloon city like a grape?
Yes. Same as if your rocket is trying to land at your Moon or Mars base (or hell, your Earth landing pad) and goes off course, it squashes your colony like a crouton.
>By launching your rocket from the ballon city and returning to orbit. (I'm struggling to see the novel problem.)
I believe they are having trouble envisioning how you would launch rockets from a balloon city without disturbing the equilibrium of the balloon city because it is assumed that rockets thrusting down with great force would damage the balloon city in a way it would not easily recuperate from.
I also find the idea difficult to understand, but assume that is because it is in an area I know nothing about and the problems that I think sound bad are actually totally solvable engineering problems otherwise it would not be have been suggested as a solution by engineers expert in that area.
on edit: changed rocks to rockets
> how you would launch rockets from a balloon city without disturbing the equilibrium of the balloon city because it is assumed that rocks thrusting down with great force would damage the balloon city in a way it would not easily recuperate from
It's a floating platform. Same as the ones SpaceX lands its rockets on. Same as a gunboat firing projectiles.
Will a launching rocket impart force to the platform? Yes. But unless the platform is super weirdly balanced, or the rocket absurdly oversized for the platform, it will stabilise after rocking a bit. (You'd have to design the platform to be stable in winds, anyway.)
And if you do have an absurdly oversided rocket, you don't launch it from your platform. You float it off to the side on a dedicated launch "boat" and have it ditch its floaty as an ultra-early first stage.
>It's a floating platform. Same as the ones SpaceX lands its rockets on. Same as a gunboat firing projectiles.
It's a great comparison that helps me understand it a bit. In many respects, Venus's atmosphere is as heavy as an ocean. That said, I can still see how if you're talking about the upper atmosphere with pressure similar to what you would have on Earth, the force necessary to do a straight vertical takeoff imparted against a platform seems like it could cause problems.
But it might just be the Archimedes thing of "give me a prop large enough and deliver long enough and I can move the world" applied to atmospheric dynamics, e.g. enough buoyancy and you're good to go. I just don't know how much is "enough" when you're talking about Venus and if that runs into prohibitive engineering complexity that makes it different from our familiar Earth examples.
Not saying it can't be done but I think that one question at least, was reasonable.
Oops, that should be "and a lever long enough"
>And if you do have an absurdly oversided rocket, you don't launch it from your platform. You float it off to the side on a dedicated launch "boat" and have it ditch its floaty as an ultra-early first stage.
The ww2 german "v2 in a tube towed by a U-boat so it can get closer to its target" project being a decent conceptual example of this.
No need for a launch boat. Just light the fuse and eject it from your balloon. Think subsurface missle launch by an Ohio-class sub.
Launching the rocket from a balloon is not a problem. You can have a platform with a hole underneath the rocket's exhaust and the balloon itself can be a torus through which the rocket flies upwards. There would be minimal impact of a rocket launch on the platform if designed properly.
Heck, you could just drop the rocket and have it ignite (one hopes) with lateral thrust, clearing the launch aerostat.
Or consider the aerostat disposable (at a significant replacement cost, see: <https://news.ycombinator.com/item?id=45333674>).
But either way it's a bit less the firey-burney-explodey problem than the sudden loss of a few thousands tonnes of mass that would displace the equilibrium of the launch platform, should you care to re-use that, or the means by which such platforms (capable of supporting said thousands of tonnes of mass).
Just to put some hard numbers on it, a crewed Falcon9 (Crew Dragon) has a launch mass north of a half-million kilograms, or 500 tonnes.
The Russian Soyuz-FG, also human capable, has a launch mass of slightly over 300 tonnes.
If this spacecraft is only a shuttle to low-Venus orbit with another transfer craft for the flight back to Earth (or other points of interest) that should suffice. If the launch craft is intended for the full return trip of 100--250 days, things could get a bit cozy and interesting depending on the number, disposition, and fragrance of inhabitants.
There is precedent: SpaceShipOne was successfully launched from an airplane [1].
The great force downward is (mostly) irrelevant if there is nothing below. Just hang the rocket between two towers over a void, with the atmosphere below.
[1]: https://en.wikipedia.org/wiki/SpaceShipOne#Launch_aircraft
>I also find the idea difficult to understand, but assume that is because it is in an area I know nothing about and the problems that I think sound bad are actually totally solvable engineering problems otherwise it would not be have been suggested as a solution by engineers expert in that area.
A refreshingly sober approach that I think is a lot more healthy than hip firing incredulous questions.
I agree though, I don't intuitively understand how it would work. I would think you would do horizontal takeoffs. Also Seveneves by Neil Stevenson gives some interesting examples of ways to escape gravity wells without rockets, but I won't spoil anything there.
I have a silly take on this: to avoid rocking the floating city you throw the rocket overboard, let it re-orient itself upright, then use the main thruster to slow down the fall and then move up.
>Literally how floating works.
Yes, ignoring momentum. Do parachutes just get stuck in the air halfway down? When do you inflate it? If you inflate it, can you even deorbit? Do those pop when you deorbit? Do you cover the balloon with big heavy heat shield tiles?
I'm not claiming I understand this at all, but you seem to have some child's grasp of "how floating works".
> By launching your rocket from the ballon city and returning to orbit.
Launching from the solid ground shakes it (the ground) like a leaf. But you're going to launch a rocket from the balloon, and you can't quite see where there might be a problem.
>Why is this unique to Venus versus anywhere else in space?
If I can't get the materials to repair my building in a hurry, I go outside and I wait. Or I stay inside and I wait. And if I can't do that for my Venusian balloon city, I slowly sink into a zone that melts lead and bakes me alive. And if I get the materials after it has stared sinking, repairing it won't reinflate the balloon and have it rise again, because some significant fraction of the air has leaked out.
>If I can't get the materials to repair my building in a hurry
At that point you might as well be asking "what if they forgot to put fuel in the space ship" or "what if the astronaut missed launch because he forgot to set his alarm". That would be bad but that's not about Venus.
The guy you're responding to is an aerospace expert, iirc.
Anyway, the balloon would be relatively stable. The atmosphere gets increasingly dense as you go towards the surface, while the balloon has a particular density which is more than the wispy far atmosphere and less than the dense low atmosphere. Therefore, if you were to drop it at the top, it would fall (while it's more heavy) then approach the altitude where it's equally dense, and start bobbing around there, until it settles at its equilibrium.
Picture a glass cylinder of water and oil. It's cleanly separated with the denser water on the bottom and oil on top. Then drop an ice cube in. It will sink through the oil and then float, in the middle of the cylinder, on the water.
Last I heard, though acidic, the Venusian atmosphere is not made of oil and vinegar. Nor does it have hard strata lines.
Suddenly losing or gaining a few hundred tonnes of mass will do interesting things to a free-floating aerostat.
> If I can't get the materials to repair my building in a hurry, I go outside and I wait. Or I stay inside and I wait. And if I can't do that for my Venusian balloon city, I slowly sink into a zone that melts lead and bakes me alive. And if I get the materials after it has stared sinking, repairing it won't reinflate the balloon and have it rise again, because some significant fraction of the air has leaked out.
It's more similar to a boat than a house. If your boat has a leak, you need to repair it very quickly or it ends up at the bottom of the ocean. Yet we've managed to do it relatively reliably.
>Yet we've managed to do it relatively reliably.
Sure. Do that when you're in the middle of an ocean that's a few trillion miles wide. It's not as if you can just dive down to the bottom of the ocean there, mine some bauxite, take it back up to your sinking ship, refine it, manufacture new repair materials for the boat, then repair it, is it?
No, you have to have it shipped from a coast a trillion miles away. So again, where are they manufactured, and how long do they take to get there? Can any of this shit even be made in the vicinity of Venus, where transit times might be non-absurd? There are no recoverable materials on the planet itself, are there?
You probably launch and land on a floating platform nearby. Nobody on Earth launches from a city. They launch and land in remote areas. Safety and noise. Lot of noise.
Then you fly to the colony balloon.
I'm sure we can figure out stuff, but I guess my point is, why would we do that at all?
How fucked up Earth needs to be than living on a floating oil platform above Venus is better? The point is already hard to make for the Moon or Mars.
Because it's cheaper to live on a f-ed up half-built construction site of a planet than it is to fight with entrenched interests on earth.
Same reason North America got colonized by religious extremists and weirdos.
The free, abundant land choke full of natural resources was probably more important.
There was plenty of death and danger involved in colonizing a foreign land you've never been to with 16th-18th century era technology.
Only free if you discount the costs involved in carrying out genocide against the existing inhabitants. But your point stands, that cost was frequently born by the government, so from the perspective of individual settlers it was often free.
> But your point stands, that cost was frequently born by the government,
Who paid this government?
It's less about the earth being uninhabitable and more about redundancy of species.
Living on a ship at sea, or underground / underwater, should give enough protection against whatever post-apocalyptic situation exists on Earth, it's pretty much always going to be more survivable than Mars or outer space. You might need a protective suit, air filters etc. Still 100x easier than having no atmosphere at all.
What if the threat is not environmental collapse but hostile government?
If they can reach your submarine, they can reach your space colony.
Surprise Dodgeball reference. But I don't think the ocean is as far away as deep space. I also think due to its proximity, it could be entangled in political paradigms that lead to entanglements in international conflicts and the independence from those political paradigms affords a form of insulation.
Aye, this! Redundancy of species...
As in sending a part of species to a hostile place where all living is confined into a one big life support machine, without fresh air (which is very different from freshly uncanned or chemically generated air), without fresh and varied food (which is very different from artificially grown), without open sky and Sun above, without seas, rivers, forests, mountains, without anywhere to wander to find inner peace, in a setting for a psychologic horror where one deranged member of expedition is enough to bring it down.
That is going to contribute so greatly to the redundancy of our species.
I'd much rather be on a cruise ship than a lifeboat, but that doesn't mean cruise ships shouldn't have lifeboats.
No serious advocate of settling Mars, Venus or anywhere else in space seriously believes it will be easier than remaining on Earth, nor are they suggesting that it means we can abandon the Earth entirely, or care less about protecting its biosphere. They simply understand that, no matter much of a relative paradise the Earth is, so long as 100% of humanity exists there then we are placing all our species' eggs at the bottom of a single basket's gravity-well. It will do us absolutely no good if we solve climate change, war, poverty, disease, etc. only to get wiped out by the next comet or mega-asteroid that smashes into us. And, statistically, eventually one will.
>As in sending a part of species to a hostile place where all living is confined into a one big life support machine
At first, I thought you were describing the settling of Australia
Got a better alternative?
This puts the cart before the horse. At least one important question to answer before. Does something absolutely needs to be done? Then we start looking into the best alternative.
What's the concrete threat scenario you avoid by moving to the Venusian clouds? Global warming? Fix it on Earth and if you can't convince people to agree on a solution here, how will you convince them that a Venusian balloon is the best way forward? Nuclear annihilation? Probably digging deep underground is better. Total planetary annihilation? Maybe stations in Earth orbit, or Moon's poles, or L point, etc.
Are we looking for options for which we have the technology and capabilities today, or a few centuries from now? That changes your options from "balloon on Venus" to "terraforming Venus".
The engineering and other practical considerations needed to get such a "station" a realistic chance at long term survival are about as sci-fi for us today as the starship Enterprise. We aren't even at the point where we can sustain an isolated Earth based colony indefinitely in an inhospitable environment. They all need constant maintenance and resupply from the the hospitable environment just a stone's throw away.
It would be one of the worst places. So, you are living over a floating habitat that the only way to get resources it's from out planet. Because, on the surface, the conditions are so hard that even remote mining is impossible.
It would be better the moon, Mars or even moving habits on Mercury. At least you have access to mineral resources, and water (ice).
People don't scale mount everest because there is an macguffin to be found there. They scale it to scale it. Because you can. For the adventure. To assert dominance over the universe.
We can talk about economical benefits or the survival of the species and those do matter. But it's also because colonizing another planet would be fucking epic and go down in history.
With the decline in religion we do need some kind of higher purpose and meaning to rally behind, and going off planet could fit that bill. In a time of increasing divisions it could foster brotherhood.
I understand this became a hot take in recent years, because you can always just "Colonize Earth". I do think there is an independent strategic value in terms of existential threats. It shouldn't be a rationale for abandoning environmental preservation and conservation on Earth.
One thing I see, all too often in Internet comment sections is things that could be complimentary are turned against each other and juxtaposed as if one interferes with the other. I don't know if there's a name for that but it happens often enough that it should have a name.
pretty fucked up if it runs into an asteroid or a comet!
> why would we do that at all?
This question is one of a whole genre of "why" questions that come from supposed pragmatists, but I can't help but think the existence of the question misses the entire point.
Luckily, one of the older questions of this genre was about why anyone would bother to climb Mount Everest, and ol' Mallory had such a good answer that I'll just paste the whole thing here:
> People ask me, 'What is the use of climbing Mount Everest?' and my answer must at once be, 'It is of no use.' There is not the slightest prospect of any gain whatsoever. Oh, we may learn a little about the behavior of the human body at high altitudes, and possibly medical men may turn our observation to some account for the purposes of aviation. But otherwise nothing will come of it. We shall not bring back a single bit of gold or silver, not a gem, nor any coal or iron.
> If you cannot understand that there is something in man which responds to the challenge of this mountain and goes out to meet it, that the struggle is the struggle of life itself upward and forever upward, then you won't see why we go. What we get from this adventure is just sheer joy. And joy is, after all, the end of life. We do not live to eat and make money. We eat and make money to be able to live. That is what life means and what life is for.
Of course, with Venus, there's the joy of exploration and also tons of profits and learning to be had. For example, we could cover the entire planet in giant ads. Think of the CPMs you'd get as people looked out the window on their way to Mercury!
On some level I agree with the spirit. But I also think it implicitly concedes that there's not good reasons otherwise, which sells it too short. Existential threats to humanity seem like a pretty good reason, to the point that if reasons mean anything at all it should count as one.
> By launching your rocket from the ballon city and returning to orbit. (I'm struggling to see the novel problem.)
Literally how flying planes off Aircraft Carriers works.
Speaking as a former naval aviator, we haven't cracked the whole "cats and traps with an SSTO" bit yet.
> Yes. Same as if your rocket is trying to land at your Moon or Mars base (or hell, your Earth landing pad) and goes off course, it squashes your colony like a crouton.
The question you answered reads like someone that has missed all of the spectacular fails with Starship tests. Which is the ship designed for these types of adventures, so it seems like a big miss by the GP
> By launching your rocket from the ballon city and returning to orbit. (I'm struggling to see the novel problem.)
I think Newton’s third law may cause trouble-but I’m no physicist.
It’s not even science fiction
https://youtube.com/shorts/MqiSQD6HipQ
> I think Newton’s third law may cause trouble
No more than for a floating platform on the ocean. (Or frankly any sea or airborne firing platform.)
If your launch mass is a significant fraction of station mass, and you can't counterweight, you could float it off to the side and then have the baloon detach when its engines fire. But none of this is in even the top thousand problems that come with colonising Venus.
Floating on a liquid surface is markedly different from floating within a fluid (liquid or gaseous).
To float on a liquid, one merely needs to maintain a lower average density within the vessel than the surrounding liquid. Assuming a largely hollow vessel (as with a ship or barge), it's possible to add or remove considerable payload without losing stable flotation characteristics as the draft of the vessel automatically compensates for the variation, displacing more or less liquid, and maintaining equilibrium.
To float in a fluid, one must maintain precise neutral buoyancy, which is an entirely different animal. As pressure varies with depth or altitude, the tendency is for a vessel to contract as it sinks and expand as it rises, leading to a runaway buoyancy shift (increasingly negative with depth, increasingly positive with height). Many military submarines operate at comparatively shallow depths, often only slightly more than their overall length* (for larger submarines), given both the immense pressures of even modest ocean depths (a few hundred metres), and the compounding nature and risks of runaway buoyancy loss.
Plans for cargo airships face corresponding problems in that when offloading cargo or passengers it is necessary to vent or otherwise scavenge lifting gas (the expense and/or challenges of either venting or compressing helium are great), or to onboard a corresponding mass of ballast. Where suitable water is plentiful the latter is fairly viable, but there are many applications proposed for cargo airships which suggest transport of heavy cargos sites with limited capabilities for same (no facilities, deserts, salt- or otherwise-contaminated water which might play poorly with buoyancy-compensation systems aboard the airship).
Rocket launch from an inhabited floating atmospheric platform would require accumulation of large stores of fuel (the Tsiolkovsky rocket equation also works against you), as well as presenting various risks associated with enormous barely-contained explosions (should you be lucky). The risks are immense, and hand-waving them away is disingenuous to the extreme.
> To float in a fluid, one must maintain precise neutral buoyancy, which is an entirely different animal
You're right, I was oversimplifying. An aerial or submerged launch platform, then.
> the tendency is for a vessel to contract as it sinks and expand as it rises, leading to a runaway buoyancy shift (increasingly negative with depth, increasingly positive with height)
This is inherent to the cloud city design. Rockets would be a subclass of buoyancy risks, eclipsed entirely by atmospherics.
> Rocket launch from an inhabited floating atmospheric platform would require accumulation of large stores of fuel (the Tsiolkovsky rocket equation also works against you), as well as presenting various risks associated with enormous barely-contained explosions
This is a fair criticism. It's also solved by having offboard propellant storage and launch platforms.
> risks are immense, and hand-waving them away is disingenuous to the extreme
Didn't mean to suggest it isn't risky. Just that the risks from the rocket launch component are dwarfed by many, many others, and to the extent there are risks here, they are ones we've already solved on Earth in analogous contexts. (Maintaining buoyancy isn't remotely the main problem with launching rockets from high-altitude blimps.)
How do those offboard propellent storage and/or launch platforms keep from plummeting to the planetary surface?
What is their buoyancy-management system?
You're offloading the problem, not solving it.
>What is their buoyancy-management system?
Some of y'all have never seen a marina with floating docks and it shows. More of the same.
This entire problem is basically ye-olde spaceX barge only with different factors in the equation and running in both directions (instead of just landing).
Yes, without a hard cut in buoyancy like you get with something that's way denser than air floating in something way denser than it all the math gets a little wonky but it's all still fundamentally the same. When you load a few million pounds of shit you sink a few thousand feet instead of a few inches like a barge in water would, and when that weight turns out to be a rocket that yeets itself you move around thousands of feet or miles instead of feet like a barge, but when you're floating in the air with nothing to crash into who cares.
The dock/barge case is addressed here: <https://news.ycombinator.com/item?id=45330638>
An aerostat doesn't float on a liquid at stable equilibrium through draft displacement, it is suspended in a fluid, with the problems noted previously.
Docks and barges (along with general watercraft) may be constructed arbitrarily robustly from strong and resilient materials. Aerostats somewhat less so.
>The dock/barge case is addressed here: <https://news.ycombinator.com/item?id=45330638>
Addressed naively and wrongly hence the ongoing discussion
>An aerostat doesn't float on a liquid at stable equilibrium through draft displacement, it is suspended in a fluid, with the problems noted previously.
If you let a baloon go will it reach space? No, because the atmosphere is not constant density.
Balloon type objects have the nice side effect of expanding and contracting to reach buoyancy/weight/structural equilibrium. It's not like a submarine "flying" though the water. It's more like a fish expanding/contracting to ascend/descend. More literally, it's like a weather balloon that rides at different attitudes depending on what the weight of your payload is. If you really need to change altitude quickly (or perhaps in response to taking on or losing mass) it wouldn't be all that difficult to inflate/deflate (i.e. change displacement) a subset of whatever device provides buoyancy. Think of it like a heavy lift ship flooding itself (reducing displacement) to change draft.
Like I said, the lack of a "hard cut" between atmosphere and ocean makes the math wonky compared to what we're used to, but the physics DGAF.
>Docks and barges (along with general watercraft) may be constructed arbitrarily robustly from strong and resilient materials. Aerostats somewhat less so.
You could say the same thing about boats vs port facilities.
Yeah, it's an engineering problem but it's a fundamentally well understood one. The way your hand gets forced in terms of material choices might make cost go through the roof, but it the design side of things shouldn't be all that terrible.
The analogy isn't letting go of a balloon, it's of dumping a large mass of payload (rocket + fuel) from an aerostat quickly.
The aerostat will rise. It will float higher in the atmosphere, with decreased pressure around it. It will expand. It will then rise still further.
And there's no ready supply of solid or liquid ballast (as would be available on a near-ground cargo drop) to compensate for the lost mass.
This is untenable for any manned / habitable module, and you'd all but certainly want any of same well outside the danger zone of a rocket malfunction.
One likely consequence is that any launch aerostats would be at best highly unstable in their altitude and station-keeping characteristics. It's quite possible that a disposable, single-use design might be required. Given that materials would likely have to be shipped from Earth, or possibly from near-Venus asteroids via space-mining, this considerably increases cost and complexity of any such missions.
Aerostats, as lighter-than-air craft, have vastly more-tightly constrained mass budgets than any water-based floating structures. Ignoring and/or waving that away is obtuse in the extreme. Particularly given the additional concerns and considerations of launch-capable structures. Existing aerostats and rockets operate at the outer limits of engineering design capabilities, and still go boom with some regularity, often due to exceeded structural tolerances.
>The aerostat will rise. It will float higher in the atmosphere, with decreased pressure around it. It will expand. It will then rise still further.
Now explain weather balloons. Why don't they rise to infinite altitude?
Like I said, the numbers are all wonky, but the principals are the same.
If there is too little mass for the amount of bouncy just compress your gas and hold some reserve buoyancy/balloons to inflate if you expect to be able to deal with rapidly increasing mass.
Weather balloons reach a stable equilibrium altitude because 1) they're designed to expand as they rise (at quite an impressive ratio) and 2) they're not suddenly gaining or losing 100s of tonnes of mass.
At least one if not both those prereqs is missing from the observed case. Though discussing the matter further has lost virtually all appeal.
You fly the rocket on the bottom of a plane, then fire it out. Assuming these cloud cities have landing strips, right?
Managing ballast might be a challenge…
> You fly the rocket on the bottom of a plane, then fire it out
This requires engineering the rocket to withstand structural loads in two directions as well as a ~90-degree rotation under thrust. Not trivial. (It's been a major handicap for airlaunch on Earth.)
Landing on and taking off from floating platforms is like the one part of Venusian colonisation we've actually solved.
Or you just drop it off the side.
Gonathan Goff wrote bunch on what you have to work with in terms of what you can extract from Venus's atmosphere. While metals would need to be imported if you're going to pick some place in outer space to live its hard to do much better.
https://selenianboondocks.com/category/venus/page/2/
One fascinating idea I haven't heard talked about is, if we ever are able to make super-strong carbon composites, they could be used on Venus for passive floating dragnets to scrape raw materials from the surface. They could float just enough to drag the surface from one end and be carried along by winds from the other, and then be passively triggered to float back to the upper atmosphere to be harvested.
Thanks to the extreme bouyancy of Venus, a small amount of compressed air could passively lift much more than it would on Earth, making Venus's bouyancy a secret super power. And you could design nets with creative combinations of hooks, one-way valves and so on to gather a payload as it passively drags the surface. And seaweed-style distribution of compressed air capsules could make it fault-tolerant even if ripped into segments by the horrific winds of the middle atmosphere.
The temperature, torsion, and corrosion are as extreme as it gets, and it may not be realistic, and/or it may not be feasible to think such payloads could float through the hurricane force winds and be recoverable in any systematic way at higher altitudes. But it has a tantalizing feeling of "holy heck this bouyancy super power might be useful" in the event we had material strong enough to do it. That would give a hypothetical Venus settlement access to iron, magnesium, aluminum, calcium, some titanium, and bunches of silicon dioxide.
Yeah, if you can't send robots to the surface to mine necessary minerals, don't bother building floating cities.
> How do you deorbit Venus is such a way that your inflatable balloon city comes to a gentle stop, 30 miles up, and just floats there?
Aerobraking with the balloon? A balloon the size of a city would slow down very fast in a thick atmosphere like that, then slowly descend until it reaches the stable altitude.
> Worse still, when people need to leave and return to Earth, how do you launch a rocket from the balloon city and return to orbit?
Spaceplane? Take off like a glider on a slope runway, then ignite the rocket.
> If there aren't materials to effect a repair, how long until it sinks down into the hellzone? Where are materials manufactured for repairs, and how quickly could they be manufactured and sent there?
That's a true problem. Local manufacturing would be on the surface. An elevator or cable car could make the connection to the ground facilities, if the winds aren't too strong. But the manufacturing of the materials would be extremely difficult in surface conditions.
> If a rocket is trying to land and goes off course, does it squash the balloon city like a grape?
Nope. See first answer.
> Saying that holes can be patched is well and good, but there are some truly catastrophic failure modes that don't seem entirely unlikely.
Possibly.
But the biggest question is why go there?
Facilities on the surface of Venus ? What drug did you take?
First. High temperatures in a corrosive atmosphere. Also, there aren't winds. There are currents. At the surface the atmosphere it's supercritical. It's more like a fluid than a gas.