K^2

Correct. It's not a real cube, it is a drawing of a real cube. If I borrowed $20 from you, and returned a drawing, you'd complain. A real cube exists in 3 dimensions. A real tesseract exists in four.

Limiting factor in NTR is temperature, not energy. Lighter propellant carries away more heat, requiring higher input from reactor, but that's usually not hard to achieve. But it also leaves at higher velocity. So for the same 1kg of propellant, you get more momentum. For a conventional rocket, it doesn't matter. Your limiting factor is energy, and all you really want is consistent masses. Having some light and some heavy exhaust would actually reduce efficiency. But beyond that, you just care about how much chemical energy you have per total mass.

That's not a tesseract. That's just a projection into 3-space. A real tesseract is an ordinary-looking cube that appears one morning on your desk seemingly out of nowhere, and disappears just as suddenly shortly thereafter.

If you double RPM, you can cut the diameter in 4. Maybe you'd also be ok with half-gravity. So optimistically, you are still looking at over 60m in diameter. By circumference, this is several times longer than all modules of ISS put together lengthwise, plus you need a hub, plus you need structural supports that will actually be under load. Doable? Yes, but about an order of magnitude more expensive and complex than the largest thing we've put into space so far. I'm also a bit weary of a proposal to build a structure you need to acclimate to as a "hotel" or orbital way-point. This is why I usually stick to 2RPM value. It's something majority of people will be just naturally ok with without requiring an adjustment period. Like I've said before, the ring idea is solid in principle. It's what we should be aiming for long term. But this should not be our first artificial gravity project. We should be aiming for a counterweight-based design first, regardless of whether we want to get an Earth gravity at comfy 2RPM for general stay, or we just want a Mars gravity 5RPM proof-of-concept research lab that we can stick trained astronauts into and which we can probably slap onto ISS. Lets just not immediately jump into building out a full ring either way, unless there is some very specific safety or cost-saving reason involved.

We do need more study, of course. But the few experiments that have been done seem to indicate 2 RPM (give or take) as a rough threshold for people developing discomfort. What we don't know is whether it's something that gets worse over time or you get used to it. Either way, though, we have to start somewhere, and a module-counterweight system will always be easier to build than a balanced ring for any given radius. So while end goal might indeed be rings, or even long cylinders eventually, that's not where we should be starting. Whether it's a proof of concept module for ISS or a totally new station, building out a full ring makes very little sense. I don't think hubless is going to work very well, and it's not a significant enough simplification. Adding a hub pretty much solves the problem. Docking port on the hub-facing side of the habitat, a corresponding port on the hub itself, and a small module that can slide along the cables with ports on either side. I'd call it the space elevator, but the name's taken by something stupid. And if the rate of rotation is slow enough, matching it shouldn't be a problem for any ship approaching the hub. So you have a simple way to get in and out.

It's not like there are any options besides rotation. Starting with a massive wheel sounds a bit overambitious, though. For comfortable stay, you need a ring half a kilometer across. You can shrink that a bit by going to lower gravity and slightly higher rotation speed, which can cause problems for some visitors, but there's only so far you can push it before people start feeling sick. On the other hand, 500m is not a problem if you simply have a tether with a counterweight. In fact, this might be great for a nuclear-powered design, where reactor is more than a quarter mile away from habitat. We really should be working on something like that as an intermediate stage between stations we have now and such giant structures as rings.

If we're going to make it work, NTR. I'm really hoping for a breakthrough in nuclear isomers for that, though. It's the only way for us to have clean launches on true orbital commerce scale, with millions of people going up and down every year. The only other way to break out of the well on civilization scale is the h+ route of not bringing the meat sacks along. All else ends in ruin. We can't sustain necessary scale of launches on chem rockets.

When aerobraking against something like Jupiter or Saturn for aerocapture, heat generation is slightly less of an issue. Because the radius of the planet is larger, you get to spend longer in atmosphere, which means significantly less force, and the heat is deposited over longer time, allowing for it to dissipate naturally. This means that you can usually get away with using your craft and solar panels as your aerobrake, without needing a heat shield or dedicated drogue.

Aerobraking is hard to estimate with high accuracy, but at the speeds involved, you usually just scoop up the atmosphere with your craft, so a drag coefficient of 2 tends to be a sensible approximation. In other words, FD = Aρv2 Naturally, A - the cross-section presented, depends on orientation of the aircraft, and ρ - atmospheric density, will vary primarily with altitude. By integrating this force along trajectory, you can estimate amount of work done against your spacecraft, which will give you the effective delta-V. Usually, unless you are doing direct descent, aerobraking will not alter trajectory through atmosphere too much. So you can get away with picking a periapsis and integrating the drag. In other words, you don't need to solve differential equation. The integral itself, however, is ugly, so you'll have to carry it out numerically. In terms of finding correct periapsis, procedure is the same as for finding a root. Pick a periapsis that's definitely too low and one that's definitely too high. Take a point in between, compute delta-V, and see if it's too low or two high. Discard high or low starting point based on result, and keep repeating the procedure with remaining two points until they get close together.

No. But I can explain it like you don't know any Quantum Mechanics. Particles are complicated and unintuitive. Lets work with marbles instead. Imagine that I designed some nifty "smart" marbles that can change colors. The surface is covered with e-ink that can turn red or green depending on electrical signal from internal circuitry. Each marble comes in a box. It detects when the box is opened for the first time, and picks a color at that point. Once chose, the color stays. Inside, there is also a tilt sensor that measures direction of gravity, and we'll use it to make a decision on the color. Now, I have two types of these marbles. First is the "deterministic" marbles. It has very simple circuitry. If it detects that sensor is pointing mostly down, it will make the marble red. Otherwise, it will be green. Since the marble is spherical, the sensor can be oriented any which way, but before you even open the box, the outcome is predetermined. Of course, you can influence the outcome by tilting the box before opening it, but for any given orientation, the result will always be the same. Still, you don't know the initial orientation of the sensor, so from your perspective it's a random 50/50 chance of finding a red or green marble. Second type of marbles is "quantum". They are slightly more complicated. The circuitry inside will take a measurement of the angle of the sensor, and will use that to randomly assign the color. The closer the sensor is oriented to pointing straight down, the more likely it is to pick red, getting to 100% red when sensor is pointing directly down. The outcome still depends on how you tilt the box, but in an impossible to predict way, so you still observe these coming out 50/50 red and green. Evidently, there is no simple way to distinguish between these two mechanisms. Any way you try it, it's 50/50 from either batch. So now, lets consider special pairs of these marbles. Lets say I hand you boxes with marbles in pairs. For each pair, I guarantee that the sensors point in exact opposite direction. You still don't know what the direction is, so any box will still produce red or green marble at 50/50 odds, but you can make some conclusions. Specifically, if you open a box with "deterministic" marble, and it's red, you KNOW, the other one is green. Since sensor points in opposite direction, if first was mostly pointing down, the second mostly points up. Opposite color guaranteed. So you start opening these up, and you notice that ALL marbles behave this way. So are all of them deterministic? Well, there is one more thing "quantum" marbles do. They use radio to talk to each other. So if one marble picked red, the other will re-calibrate the initial zero position of its sensor to guarantee that it will turn green. And vice versa. So when you open them up in pairs, they still produce one red and one green. Annoying! Enter Bell and his inequalities. I won't get into too much detail, because the actual theorems are quite general. But we can talk about specific case that applies to our marbles. Lets take a single pair of boxes. We'll keep one box as it is, and we'll tilt the other box by some angle before opening it. If the tilt angle is zero, boxes behave exactly as before - one red one green. If you flip one box by 180°, then both marbles will be red or both will be green. And the exciting stuff happens in the middle. For the two "deterministic" marbles, as you change the tilt angle of one of the boxes from 0° to 180°, the correlation between colors changes LINEARLY from -1 to 1 (from always opposite to always same). If I stop at 45°, I expect the two marbles to have the opposite color 75% of the time, and same color 25% of the time. But not for "quantum" marbles. If you tilt one of these boxes to 45°, and you follow all of the above rules, you'll find that the odds of two marbles ending up with different colors will still be higher than 75%. And this is guaranteed to be the case, pretty much regardless of the rules used to chose the colors, so long as it's a smooth dependence on orientation of the sensor. The more general statement of the Bell's Theorem is that any kind of hidden variable, which pre-determines outcome of experiment, can be distinguished from a random outcome by considering these types of correlation experiments. And that gave us a way to confirm some of the most important assumptions of Quantum Mechanics about how the outcome of the experiment is determined.

100kg of air per second. Yes, typo is my fault, but if you seriously can't even follow THAT derivation, I see no reason to continue discussion. You still haven't answered a single question posed. And the fact that you continue talking about nuclear power is a total reading comprehension fail on your end. Adios.

Lets deconstruct this step by step. Your energy equation (finally with units!) has 1kg/m3 and 1m2. The unit-less equation in your previous post had just a single 1 of one of these. Units are important. Your equation was, in fact meaningless, even if you started out by copying the correct thing. You got lucky that both density and cross-sectional area are 1 in the units chosen. Has it been anything different, the answer wouldn't have anything to do with reality. Moving on. What are you actually looking at? Energy consumed per hour. How much water is generated? You're pushing 100kg of water air per second, or 360t per hour. That's 3.6L of water. Lets look at energy per L. 7.2GJ / 3.6kg = 2GJ / kg. Lets also throw away the meaningless efficiency factor: 2GJ / kg * 0.25 = 500MJ / kg. Now, where have I seen this number before? Oh, yes, in my previous post, where I showed you the CORRECT way of deriving the energy requirements. This is how the flow equation you're using is derived. By assuming that 100% of energy expended on accelerating the air is lost. Still feel like making fun of that concept? Because the real joke is that you didn't even realize that it's the same exact math you've been trying to copy from Google all along. Without having any idea what it actually means or where it comes from. Moving on. The efficiency number you are using is correct for a fan you'd use in a room. One with poorly designed blades, small area, and a lot of turbulence. If you take that 25% efficiency, and apply it to any real world helicopter, you'll be forced to conclude that it can't fly, because it's engines cannot produce enough power for sufficient lift. Realistic numbers for helicopter rotor can be as high as 60% - 70% efficiency. This is a single-stage rotor with no enclosure. A carefully designed multi-stage fan in a smooth duct can reach 90%. And if the only thing you care about is throughput, you can design the duct to give you over-unity efficiency by slowing down exhaust flow, and recovering some of that kinetic energy. If you spent fifteen minutes actually looking at real world designs of propellers, fans, and turbines, you would be able to know all these things. Instead, you plainly just typed in "fan efficiency" into Google, and ran with the first number you saw. Amazing that it backfired, innit? Ha, ha, ha, ha, ha. You're joking, right? You take three attempts to copy correct equation from Google, and you have zero idea of where it came from or what it actually means. I know you can't do the math on air flow from a room. That's why I'm asking you to do it. You clearly have zero background on actual physics. But you keep arguing with somebody who has over a decade of experience in the field as if you know better. And you show zero attempt at learning anything. Are you going to put in ANY effort into actually THINKING about the problem, or should I completely give up on you? I don't really see a point of going through the rest of it until you decide how you want to take this. You can either show that you know what you're doing by solving the room problem, admit that you don't have a clue what you're talking about, or we simply end this discussion.

Hard UV will do a lot more than give you sunburn. It also disintegrates most plastics. But hey, I'm sure you weren't planning to use any of these. At any rate, you just completely skipped over the particle radiation that's going to fry electronics and, over time, kill anyone who doesn't spend most of the time buried under ground. It's 150ppm of SO2 outside. 50ppm is considered safe for short-term exposure. You can let someone in through a door, and still not get to levels considered harmful for short-term exposure. Moreover, you can go outside, take several deep breaths, and while it won't be good for you, it certainly won't come close to killing you. As for smaller leaks, the levels have to be constantly above 75ppb before it becomes toxic for long-term exposure. That just isn't going to happen, so long as you do occasional checks. Vacuum makes you unconscious within seconds, dead within minutes. So... No, no. I want to see you do the math on this one. You keep making claims about the danger or safety of things, but they are all entirely made up. I've given you parameters, give me an estimate. How long is it until you drop unconscious? Yes, but that's a solved problem, again, see Apollo. What do you propose doing with soil at -63°C, which surrounds you from every direction? Are you allergic to units? What the hell is that first formula even supposed to be? "1003 * 1" is not power. Is it 100m/s times... what? 1kg? (100m/s)3 * 1kg = 106 W/(m*s)? That's definitely not power. 1m2? (100m/s)3 * 1m2 = 106 m5/s3 I don't even know what that is. These numbers are total nonsense. Ok, lets do this analysis for real using real physics. Worst case scenario, you're taking 100T of air and accelerating it to 100m/s to obtain 1kg of water. That's 105 kg * (100m/s)2 / 2 = 500MJ. Units match on both sides! Yes, you can compare 500MJ to some ridiculous conversion where you, again, fail to account for units. Let me give you a simpler one. 1kg of gasoline holds about 40MJ of chemical energy. So this is a little more than 12kg of gasoline. Want another one? If I plug this fan into an outlet, it will take $40 worth of electricity, and I'm using California prices. And yes, I could launch a small satellite out of Sol with this energy. This is why rocketry isn't about energy of your fuel. But alright, we're on solar panels after all, and this is considerable power draw. Fine, lets cut the flow down to 10m/s. Now I have to expand aperture by factor of 10x to compensate and get the same 2L/hour. Oh, horror, it's now a 3m x 3m duct. Now I only need 5MJ per kg of water. That's about 5m x 5m worth of solar panels to make 50L/day - and I'm taking day-night cycle into account already. You'll notice I've skirted around topic of efficiency. That's because any losses on the fan itself are easily offset by not requiring all energy to be wasted. There are many duct designs that can generate these flows with over-unity efficiency by slowing down the exhaust to generate a pressure drop which pulls more air inward. With a real fan and electric drive, the actual energy consumption will be +/- 10% of the above, depending on specific design.

Solar radiation - UV and particle, having to be paranoid about air leaks, inability to land by parachute - must use retro rockets, large temperature fluctuations on the surface. These are all critical factors in where you build, how you build, what materials you use, and what sort of equipment you need. These are all the things that will determine if you can even build a viable habitat, and they are nearly identical for the two bodies. Or I could use your argument and say, "Their difference is limited to sand being a different color, and you can jump higher on the Moon." - See how easy it is to just dismiss everything without putting any thought into what you are saying? Care to actually put effort into your arguments? Can you hold your breath in that? Don't answer that, we both know. Lets go for something more practical, how long until you pass out if there is 1cm hole punctured through a wall of an otherwise sealed room, say, 5m x 5m x 3m? How about a 1mm diameter hole in your suit? You can take as long as you need to compute the answer. I can't say the same about the repairs. It takes about 10m of water to provide adequate shielding. You can do significantly thinner with lead, but we're still talking about 10T per square meter that you need on your ceilings. All sensible proposals for Mars habitation are buried underground. Asphalt and tarred roofs can easily reach 60°+ on Earth. Yet, we don't boil because of it. Nor did the Apollo astronauts, for some reason. Again, if you look at what is relevant for base-building, when you already have to build meters of insulation, it is the average temperature. Which is above freezing on the Moon, and way, way bellow freezing on Mars. Meaning you'll have to expend energy to keep your habitats warm. If you suffer a power loss, you will freeze to death before you have a chance to suffocate. You're really stuck on this, aren't you? 100t is less than half an hour through a 1m² aperture at 100m/s. That's more than 50L of water per day. If used conservatively, enough for several households. A 10m x 10m aperture gets you enough water to refuel Falcon Heavy in 2 months. And since it's already forming ice crystals, extracting water from that will be relatively easy using electrostatics. In other words, for me to overcome the lack of water, it still takes a fan, a collection plate, and a still. And that's basically your sole serious complaint against Venus. I'm still waiting for you to describe any sort of machinery that can last for years in Earth's deserts, let alone Martian ones, which you'll be relying on to mine water from sand. If you know anybody who served in a desert, ask them about vehicle maintenance.

Yes. But this kind of analysis is treacherous. Boost at periapsis changes shape of the trajectory, not just how fast you are moving. And as you coast along, the speed is only altered by component of gravity along direction of motion. As an extreme case, a craft in circular orbit never speeds up or slows down no matter how long it orbits. So in general, one cannot insist that trajectory that lingers longer is guaranteed to have a greater change in speed. I think this will be true for any free coasting trajectory near a single source of gravity, but I'd have to think about how I'd prove it mathematically. That's not to say that your intuition about it is wrong, just that you have to be careful with using this chain of thought. Energy conservation is a lot easier to work with in this context, since it works regardless of the path taken - at least, for a conservative potential, which gravity from a single body is.

It is, if it's applied as a sufficiently short impulse. Things get complicated when you have low thrust engines, like ions, that you are using over a long transfer orbit. When you're just making a correction burn while passing periapsis, though, you can assume that it's always going to be equivalent to change in velocity. But yes, there is a reason why relevant engine stat is specific impulse, not specific velocity. Energy is also conserved, but you have to look at total energy. So you have to account for kinetic, potential, and chemical energy of fuel before, and kinetic, potential, and thermal energy of the exhaust after. Momentum, being a vector quantity, is a lot easier to work with.

Kinetic energy is always given by mv2/2. If you say that speed has increased from 100km/s to 101km/s, you are saying that kinetic energy increased from 5GJ to 5.1005GJ. If you are saying that kinetic energy increased by 0.5MJ to 5.0005GJ, then the speed increased from 100km/s to 100.005km/s, for a delta-V of 5m/s. You have to pick one of these scenarios. You simply cannot have both. The first one is correct in this case, but it's useful to work out why. Again, look at the rocket in a vacuum (no gravity) example I've given in the previous post. Do you agree that kinetic energy gain is different there, depending on how fast the rocket was going before the engines kicked in?

This was in rotating frame, where Sun revolves around Earth. That's where I got the Ω2 term in the potential from.

^ This is a really good observation as well. Moon and Mars are extremely similar environments. Gravity on the Moon is about half of Mars, which doesn't make a huge difference. Makes building there easier, if anything. The atmosphere on Mars might as well be vacuum as far as your life-support considerations go. Neither of these has radiation shielding worth talking about. Temperature variations are a bit higher on the Moon, but it is warmer on average, which should make maintaining temperature easier. There are parts of the Moon that give access to water ice in very similar condition you'd find it on Mars - with lots of hard to remove dirt. Except, Lunar dust isn't as toxic. No weather, no sand storms. The short of it, if you can't build a self-sustaining colony on the Moon, you can't do in on Mars either. And while people do want to build Lunar colony, nobody talks about it as permanent home that can stand on its own. It's always in a context of a transfer point and mining outpost, relying on constant supplies from Earth. Mars is pretty much the same environment with way more troublesome logistics.

Ok, lets walk this back. Take these 0.5MJ and walk them back to the point just after the burn. The rocket's total energy is still 0.5MJ, and the potential energy here is -5GJ. So the total kinetic energy is 5.0005GJ. So the rocket is traveling at 100.005km/s. In other words, it has just expended 1kg of fuel and went from 100km/s to 100.005km/s, getting just 5m/s of delta-V. Does that sound right to you? delta-V efficiency of the rocket doesn't change with where we fire it. If you are trying to understand where extra 100MJ of energy came from, look at what happened to the energy of the fuel/exhaust. Don't be lazy. Work through the whole thing. You are making the same exact mistake that people make with rocket formula. Forget about gravity for a moment. If you start from rest and burn enough fuel to gain 1km/s, you increased rocket's energy by 500kJ per kg. If this same rocket is already traveling at 10km/s and it performs the same burn, its kinetic energy went from 50MJ/kg to 60.5MJ/kg, for a total gain of 10.5MJ. We burned the same exact fuel in exactly the same engine. Where did the extra 10MJ came from? If you understand how energy conservation works for rocket in vacuum, you should be able to work through rocket in gravity well.

I concede the 100t / l of water. (modern source) But you should take your own advice and look up composition of Martian soil if you're going to insist that you can just "melt and clean it", as well as distribution of water ice and its quantities. I'll take 100t of non-corrosive gas to yield 1l of volcanic lake water, thank you. There is nothing in that air I can't fix with a still. Dealing with Martian sand is completely different story, both chemically and mechanically. Look up at failure rates for machinery that operates in our ordinary terrestrial deserts.

I've covered getting water on Venus vs Mars in this thread in much detail. Please, refer to that. The idea that it's going to be easy to obtain water or fuel on Mars is ridiculous. On Venus, however, you literally make it from the air. Nothing else necessary. Weather on Venus is dramatically calmer than on Earth. High altitude, more uniform temperatures, no interference from terrain. The colony will move with the winds, there is nothing you can do about it, but there will be almost no relative wind for structures to deal with. And as pointed out, your lifting gas can be nitrogen. It's hard to imagine something safer. If you want to avoid overhead of landing and launch pads, early on you can capture gliders with drones and use disposable balloons to lift the SSTO prior to launch. Eventually, I'm expecting cities of tens or hundreds of thousands, where overhead of a runway isn't a big deal. But at an early stage, you simply don't need one and can do without.

But mostly what ARS said. There are a lot of advantages to denser atmosphere. On the matter of going there and back. Going up from Mars is a lot easier than from Venus, yes. But if you're building a colony, your first priority is getting people down. A glider will manage that just fine on Venus. Maybe you'll have a drone to catch these. Maybe you'll decide to actually build a runway. Both options are quite viable, and allow for huge errors in range even with complete power-off landing. You can also do parachute or powered landing. Plus, it really doesn't matter where you come down, so long as you are within gliding range. On Mars, missing landing spot might be ok, or it might be catastrophic if you hit a bad patch of rocks. We will lose colony ships on descent there, it's not even a question of if, but only of how many. That'd be acceptable if it was the only option, but it isn't. Yes, ascent from Venus can be conducted using conventional multi-stage rocket. Although, I would argue that building SSTOs is probably a good idea. Because atmosphere of Venus is denser, the ascent from the same pressure altitude is actually easier, as the air is all concentrated at lower altitudes. Plus gravity is slightly lower. So any SSTO that can work on Earth will work on Venus. We have had promising projects that would do just fine. And whether hydrogen or methane, it will be easier to synth fuel on Venus. @kerbiloid I don't think you're picturing environment of a frigid desert in near vacuum correctly if you are imagining getting ice with an ice pick. Your entire proposal is so absurd as to be meaningless. If I bury a block of ice in a desert here on Earth, you won't be able to make drinkable water from it without a lot of hardware, which will constantly break due to sand.You will need heavy equipment to mine, refine, and purify water on Mars, all while in conditions that are dramatically worse than worst of what we have on Earth. The sand on Mars is more destructive, and cold worse than Antarctic. The sulfuric acid from my water on Venus is removed with a still. You simply cannot compare the two. And It's less than 1 ton per 1kg of water based on the same document. Again, this is altitude-dependent, and cloud colonies would be at optimal altitude for water collection. Are you aware that there is data for radiation levels at various altitudes, and that at 1 bar altitude, radiation is comparable to Earth? We have data on these things. You haven't even bothered to look at it. You continue on your trend of making up false facts about something and using them as arguments. That's not how a discussion works.

Ever heard of keeping all eggs in one basket? This planet gets hit by large rocks quite frequently. If one comes by large enough to wipe us out, we can do absolutely nothing about it. We have to have at least one off-world self-sufficient colony. Simply having supplies out there isn't going to cut it, when whatever few survivors make it there, and can't continue to sustain themselves for centuries without supplies from Earth. And how do you propose getting that ice? First, it's not abundant everywhere. In most places, there is just a bit of ice mixed in with dirt. So while you are looking for a place that has sufficient ice, setting up drills, equipment to melt and filter the ice, and all of it while traversing rugged terrain in an environment where getting a cut on your suit means death, I extend the hose, and start condensing water from air. While you are figuring out how to filter extremely fine dust from water without clogging the filter, I'm already drinking it. While you're figuring out how to fix damage due to coarser sand, I'm drinking fresh water. And when you run out of ice wherever you set up drilling and need to relocate, I'm drinking fresh water. There are four things you need to survive several days. Heat, pressurized environment, breathable air, and water. I get the first two for free. You have to generate heat and maintain pressure. If you get a leak or an electric outage, you're done. If I have an atmo leak, I fix it with duct tape, because there is no pressure difference. And if I get power outage, I sit in the dark. And then getting water is effort on Mars, vs just setting up a fan and a condenser on Venus. Doesn't matter how dry the air is, because I can pump a lot of it through a condenser with very little effort. Oh, and habitable altitudes are at cloud layers, so while it's still pretty dry, it's significantly higher moisture content than average. On Mars, these are also your only construction options. And mining on Mars is going to be a lot harder than mining on the Moon. Lunar dust is just as bad for machinery as Martian, but on the Moon it has decency to drop instantly back to the surface. On Mars, once you start drilling, that stuff will be everywhere. If you think keeping machinery operating in a desert is hard, you haven't tried it on Mars. On Venus, you can go 100% organic and not bother with any significant quantities of minerals. Venus has thick atmosphere. Getting stuff to Venus is super easy. Entry speeds for cargo in-bound from Earth will be slightly higher than these of Apollo missions coming back from the Moon. Nothing a heat shield can't handle. Landing on Mars, though? The atmosphere is too thin to properly slow you down, although still generates huge amounts of heat, and then parachutes are completely useless on the final leg. Yeah, you have less speed to kill than on Venus, but you're killing majority of it with rockets. And you can't exactly land a new module far from the base, because then you can't move it. But if rockets fail, you just bombed your own base. On Venus, any additional cargo can arrive miles away from habitats, and then be floated to the main base. The main theme of all of this is that on Venus you have backups and redundancy built into the environment. On Mars, there is zero margin for error. If anything goes wrong, you can't fix it. If you there is a sand storm and solar panels are buried you are without power. If there is a hole in a habitat, that habitat is dead. If there is a problem with your module, and you have to dash outside, you better have a space-suit. On Venus, it won't be pleasant, but you can get out and fix something. You'll need a chemical shower, but you won't be dead. On Mars, radiation is a problem. You'll need shielding for habitats, and you'll need shielding for growing food, any of this fails, and you're done. If I need a new place to grow food on Venus, I can put some air into a plastic bag, and that makes an acceptable greenhouse. And this is across the board. Living on Mars is like skydiving without a spare parachute. You can come up with as many improvements to safety as you want, it only has to fail once. Not having a backup is stupid. All arguments for Mars come down to "It has dirt". And it's toxic dirt, which won't support plant life, with fine, destructive dust, and almost no useful minerals unless you go through tons of it. It's another hazard of the Red Planet. Not a boon by a long shot. And once you give up on the idea of needing dirt under your feet - we all seem to be pretty much in agreement that free-floating space-station is quite acceptable - then Venus wins by default. Absolutely everything else is better there. Pressure, temperature, gravity, resources, solar power, radiation protection, and general lack of hazards. The colony will survive if these shipments stop. Everything crucial to survival is present in atmosphere. Everything else is "nice to have". Building a colony that won't die horrible deaths once shipments from Earth end on Venus is way, way easier than anywhere else in Sol system. We can have something self-sufficient there in decades. We cannot anywhere else.

Again, for scale height. Which doesn't mean what you implied it means, specifically because of non-constant temperature.