With certain technologies, Venus can be quite an attractive place, because of 3 or 4 factors.
- it probably(/may) does not fit what you envision or some of your requirements, those are just a few, I would call legit reasons/factors, if not then handwavium is always available.
Atmosphere
Atmosphere of Venus is 96.5% Carbon dioxide and a mass of 4.8 × 10^20 kg, it about 0.7% of the mass of Luna, and about 20% of the total mass of the asteroid belt.
Attractiveness lays in that it can be extracted without landing on Venus with means of orbital scooping, similarly to this one http://toughsf.blogspot.com/2017/09/low-earth-orbit-atmospheric-scoops.html (u like big pages, eh, so here you can enjoy it as well)
Oxygen is more or less useless, but if there is the transport of hydrogen it can be used to make water as well, at least it can be more convenient to store the stuff, for future uses.
3.5% of Nitrogen also is an interesting component. It looks like a negligible number, but considering that Venus's atmosphere is about 90 times more massive than earth's one, this number represents more than 3x the content of Nitrogen in the earth's atmosphere.
It can be useful for creating a breathable atmosphere in space habitats as an example. As basically there are just 2 easy sources of Nitrogen for early space stages - is the earth itself and Venus.
- At the moment, we are not at the early space stage, if someone is curious, ehh how to say that, mm, we entertain us with the idea of space, and are at an orbital stage, early or middle of it. Moon could be advanced orbital stage.
Carbon can be used for carbon-based nanotech, but without that, it has some uses.
Energy
It is less a thing on its own, but there is an interesting aspect of Venus - in some sense, it is a big battery of heat energy.
So that surface temperature of 740 K (467 °C, 872 °F), it actually energy stored in heat form. Mars has great research value but poor space colony value, and that poor score for space colony place is exactly because of poor sources of energy on mars.
The difference in that energy aspect can be negligible if fusion reactors, compact and sufficiently powerful are available, and fuel is available and all that, so this advantage is temporarily, but still energy stored in form of heat on Venus is quite a respectable number about 2 × 10^26 J, one can be tired counting it in oil barrels.
The attractiveness of that is in our abilities to extract that energy with simple means, being on Venus, in upper parts of the atmosphere, floating at around 50km altitude. And from that perspective, Venus looks like a big oil field.
This energy extraction can be part of a process of cooling down installations on the surface of Venus. This not only extracts energy for the upper part but also provides liquid CO2 for the ground part which is used to keep the temperature and provide energy.
- It does not solve the high-pressure problem, if you envision humans on the surface, then it is an additional challenge, but make one challenge less that is relatively simple. And that challenge is only relevant to human presence on the surface, which can be quite pointless with teleoperating from orbit.
The fundamentally important part here is that expansion, of whatever one is interested to do on Venus, can be really fast, because more or bigger the system is, faster more energy it can extract this way, and more of your goal on the surface it can do. 24.7.365
- sure it is true for any other energy extraction process, but the density of energy and corresponding EROEI can be higher than on mars, where without fusion there is not that much energy, and its density is not that great.
Surface
It can be that crust of Venus is 10 to 20 km thick, which means we probably can get to magma layers to extract those. The situation is much better than on continental areas on earth, but not necessarily as good as ocean bedrocks.
And that again means access to energy for whatever activity, so as materials - basically a rock well - drill it once and then just sit on one place and get materials for "infinity".
- and if we screw up in the process, no one really cares. it can be a testing site for similar technologies on earth for all those gree guys. Green guys invest in Venus, save the earth.
proximity to the sun
Considering the big pile of resources which Venus is, its next competitor Mercury is not necessarily a winner. It may or may not be an interesting factor.
Mcg .. Macguff... ..tinite ... What What?!?!
The problem with explanations that rely on some single reason for explaining why things do happen sure may make it easier for a writer, but it never happens, and honestly never believable or interesting. Oil on earth without all the technological achievements we have is useless and not worth the effort.
So things, events depend on the context in which they happen. What is there for them to happen? It gives a possibility for some things to happen, like a sufficient level of technologies, to the reason for them to happen.
Atm Venus and Mars are equally useless. For regular folks, like senators who sign NASA bills, so as taxpayers which pay them - it appears like a significantly bigger challenge than Mars. And with continuous successful mars programs, it seems like an irrefutable fact. And it looks like there is no justifiable cause, nothing can explain it in any other way than money drain, especially when one is fixed on reaching the surface, bathe himself in the dust of a celestial body, do ... hm idk unspeakable things with it, eh(?)
That low orbit air scooping isn't such fantastic technology, at least it does not look like for some people in that camp, even if for those who are not in it, even if they are smart otherwise there is no way to break their defense.
- proofs may be a bit on the conspiracy side, but there are(?) LEO military satellites which do change orbits and they may use similar technologies, as engines suitable for that are announced by ESA a few years back, so components are there, and they aren't that much different from what's already in use.
So even with today's technologies, we could start to tap resources from the planet, Venus. Which could have a chain of events allowing us to occupy orbit, upper atmosphere (that 1 bar line) and gradually get to the surface, and start to get resources from it.
Producing regular carbon fiber from CO2 is not impossible, and it can be a base product for making descending modules that do not land but float, and from there continue to the surface and create that energy extraction cycle.
It is possible to say that Venus is more difficult, but at the same time that scoop probe, how is it more difficult than the current mars rovers. Reaching Venus's surface can look more difficult, but how is it more difficult than establishing a Mars colony, a colony won't grow on its own, apparently.
Both cases require exporting our technologies in space, be able to use our accumulated knowledge to make things in space, create material tools there from materials available.
In that sense, Venus has what it takes to make use of it, so as Mars, so as Moon.
It can provide what the other 2 bodies have a hard time providing, it has certain advantages and opportunities.
Early air scooping on Venus, can be a decent match with Moon activity, and in that aspect, both locations Mars and Venus have advantages and disadvantages, advantage of Venus is launch windows are more often so one can get more in the same period of time(19 vs 26 months), delta-v is a bit bigger but not by much and considering oxygen is not needed on both ends, plasma drives will have plenty of reactive mass to use.
Scientific value - all places are interesting. Someone posted about life as potential reasons to jump the train and here I stumbled on the article https://www.technologyreview.com/2020/09/16/1008478/venus-soon-as-possible-phosphine-clouds-astrobiology-life-veritas-davinci/ some suspicious phosphine clouds were spotted.
So if you compare Mars and Venus (hey, where is the moon) both places have scientific reasons, it just matter of - do you have what it takes to go there, I mean money(?), rockets, whatever.
You do not have to have that McWhatWhat to go, in essence, we still know not enough, for to not to say too little, that we have no reasons not to go to all places we can go to in the solar system. The exception is probably the sun, I mean it is hot.
Do you understand what it takes to investigate/research a planet - I mean you can justify the presence of millions of people busy doing that, in situ or teleoperating equipment from orbit and do initial data processing, managing the whole process. Ping from the planet to those planets won't go anywhere in near future ever.
And a planet is not a backyard, or a country, or earth which we have access to and we still prospecting for which materials are where.
So honestly, no one needs an McWW to go there, there are regular reasons, so as future benefits to go there.
Delivery of resources to space, as a note
Venus has some problems with that, I can recognize it, Mars has a similar problem, but yes we can say it looks like Venus has a bigger one, gravity alone is enough to see that.
But again it depends on the user goals, for carbon scoop extraction, the amount of resources required isn't big, and for the similar capacities we have today on earth, in terms of resource delivery to orbit, floating platforms can be enough, rockets do not have to be big, similar to sea launch approaches. If it can deliver its hull to orbit then great - exactly what we needed. 100kg payload class of rockets. It just needs a conveyer of those, and making one having certain setups on Venus is an achievable feat.
- with carbon as staple construction material(in orbit, ground a different story), the rest of the materials required are limited. Even if we do not plan to make chips out of carbon, it may be possible but we do not have technologies for that, percentage of those materials metals, and others are not high, 1 to 2 order of magnitude less than the main construction material. The reason is that in microgravity any solid material can be structural material, and carbon with its allotropes is quite a good one. And considering water will be available for the scoop, in ppm concentrations but still, so as N, S it can be used for plenty of different stuff easing restrictions of the bill of materials in a significant way.
So as there are non-rocket and rocket/orbit assist approaches (for a second one, I know only one interesting idea, and coined the "term" for it) so it is feasible with current technologies, and meaning in foreseeable future. Having nerva would be not necessarily an improvement and it would be rather unnecessarily overcomplicating things, and definitely not Orion - less vodka makes life better, sometimes, lol.
- launch loop is quite a promising approach, its main problem is that if it fails, and with our technologies it not 'if' but 'when', it can deliver quite a damage. On Venus if it delivered something to orbit and then broke it still a win, next one please. And considering all the energy available and that there is nobody there, we can break 10's of those or a hundred and it makes no difference. Even if it does not deliver anything, we can test and perfect it until it does, no oil barrel harmed in this testing, no nuclear fuel rod is wasted and as for the materials - dust to dust.
So as there are problems, so are there their solutions. But approach clearly is not like - I wanna X and nothing else, but what useful things I can have out of what I can do and which one I'll be having today.
