Indeed, I prefer a relay too; I was just pointing out that it's not a fundamental requirement and there are mission proposals that don't use one.

Actually my "ideal" mission (a Titan sample return mission) has the relay probe be the propulsion stage (ion powered), and operating in a low orbit. While a tilt-rotor explorer would be exploring, the orbiter would be pumping its propellant tanks full of Titan's outer atmosphere (most ion engines are very propellant flexible, and the 1500m/s Titan atmosphere drag velocity is way less than the ion output velocity) and thus refilling its tanks for a return mission. So once the explorer returns on its ascent stage and re-docks, the propulsion stage now has full power and has full tanks for the return mission with the surface samples. Then back at Earth, not only are the surface samples returned, but also the residual Titan atmosphere in the propellant tanks. And both the propellant stage and explorer's (expensive) RTGs are recovered at the same time .

My ideal explorer is not a lander, but a tilt-rotor pontoon aircraft (I really don't see the point of fixed wing... tilt rotor adds in another driven component and joint, but it removes a corresponding required control surface, so it's a wash in terms of complexity, and it lets you land VTOL, then rest on the surface and recharge your flight batteries while doing surface science - aka, you can use a much smaller, cheaper RTG. Win-win-win. And while most propelled designs I've seen use ridiculously tiny quadcopter-ish motors to barely hold a heavy probe aloft (say a 0,5kg motor for a 120kg probe), my mission would have a several kilogram motor so that it'd have enough power to haul its ascent stage up to max flight altitude and velocity and reduce its delta-V reqs down to about 2k m/s. If the ascent stage has the same payload fraction as a Pegasus solid stage then that means that it'd only need to be about 150% the weight of whatever portion of the explorer you wish to return to orbit - totally doable. And the explorer doesn't need orbital maneuvering capability because you've got an ion-propelled propulsion stage out there that can come to you.

As an added bonus? You can do a stardust-style flyby of Enceladus for the added weight of a little aerogel, same with various rings, and a dip through the most extreme outer layers of Saturn with the scoop / pump feeding into a small sampling tank. Then it's not just a Titan sample return, but a Titan / Enceladus / Saturn sample return. And you save weight and cost on science experiments. You don't need to bring the science experiments to the Saturnian system, you just bring the Saturnian system back to Earth ;) No high power orbital radars or massive telescopic imagers like Cassini had, no surface chemistry experiments, no X-ray fluorescence setups... just a navcam on your propulsion stage, a multispectral pancam on your explorer so you can pick what to sample, and a good sampling arm with an abrasion tool (plus any flight hardware you can repurpose, such as the low power radar altimeter one would need).

Yeah, that'd probably be a Flagship mission. But my god, can you imagine how much data we'd get out of that?

(Concerning robotic arms... I was surprised how light they are when researching. MERs's very capable arms were barely over 4kg. Totally doable for even a mission where weight constraints are significant)

Wind speeds are irrelevant. Turbulence is relevant. Venus's cloudtops are not believed to be significantly turbulent in that layer. Who cares how fast you're moving over the surface?

It's known that there are electrical storms on Venus but not whether they ever exist at the altitudes in question.

Venus is actually the easiest place outside Earth and the Moon to have astronauts land... for broad definitions of "land" ;) See this comment.

Of course, anywhere you send humans you have to have an excuse of "them doing science", even though we all know that robots do it far cheaper. On Venus, you would have a floating lab analyzing the results of balloon probes repeatedly descending to the surface, collecting samples, and bringing them back up to the "livable" heights for analysis. For obvious reasons, humans would not be going down there.

Who knows - maybe they'd find something interesting there? Maybe Venus's hellish surface concentrates some sort of rare minerals that might justify large scale balloon collection and return. Some day. ;)

It's not necessary to have a relay, though it helps. The AVIATR concept, for example, involved no relay. The atmosphere is dense but it's not as much of a radio absorber as Earth's.

So many big questions. Are those suspected cryovolcanoes what we think they are, and if so, what's in that subsurface water ocean that they've been spewing out to the surface? What's eating up the acetylene and hydrogen? Where is the unexplained methane coming from? If something is breaking down the acetylene with hydrogen and it's not "living", what sort of natural catalyst could do that at such low temperatures? What on earth are those organic tholins that are everywhere? What are these long-chain organic compounds that are forming in the atmosphere? Could Titan have sitting on it the recipe for how the earliest life on Earth formed? What's in these seas - which are, it should be added, chemically different from each other? And on and on and on. Plus, there's so many incredible exploration concepts to try to answer the questions: orbiters, landers, boats, submarines, hot air baloons, blimps, fixed wing aircraft, tilt rotor aircraft, you name it. No funding for any of them. Even the cheap ones. It all gets dumped on Mars.

If your goal is living offworld, the most earthlike place in the solar system outside of Earth is the cloudtops of venus. A person could walk outside in shirtsleeves with just an oxygen-providing and eye-shielding face mask. Ordinary earth air is a lifting gas. Gravity is 0,9g. Aerocapture is simple. Water can be condensed straight from the cloudtops and oxygen hydrolized with the abundant solar power. There is zero dust to gum up the works (and the SO2 aspect is overplayed, even in the clouds it's not that concentrated).

If your goal is science, Mars isn't the place either, it's been way more studied than everywhere else but Earth and possibly the moon. People differ about what's the most scientifically interesting place but I'd argue that Titan has the most interesting unanswered questions.

If your goal is a colony that stands a chance of paying for itself (good luck with that), your best bet is an asteroid or cometary body (potentially with ice / CHONP, otherwise they can be shipped in with little delta-V from other asteroids / comets) that has abundant valuable metals in concentrated, non-oxidized forms for mining with little delta-V reqs for earth return or space use.

If your goal is a self-sustaining colony (a "backup earth" or whatnot), step out of the sci-fi novels. We're centuries away from that at best.

We'll just 3d-print out a new civilization on Mars.

Oh, and that infographic forgot Phoenix - so add yet another Mars lander to that list.

What great news for the prospect of life on Mars! Quantities of a chemical that destroys organics on contact are so great that they suck water out of the soil and air!

Nasa's massive obsession with this self-sterilizing rock come at the cost of investigating much more interesting targets elsewhere in the solar system. The money going to Mars 2020 in particular could do so much elsewhere (we really could use a followup to Titan, there's so many mysteries there we're not even close to solving, while new missions to Mars are more trying to find new mysteries to solve and answering the same vague "questions" over and over again) At least Europe is going to get something now - not my personal favorite (if there is anything interesting there, which we don't actually know, it's buried way too deep for us to get at it for a long, long time). But at least it's not NASA's "All Mars Channel".

Solar thermal doesn't count? Biomass doesn't count? Geothermal doesn't count?

Also, on the other side of the spectrum, captured industrial heat doesn't count?

I agree that the world needs to do more with waste heat. But it's not much of an argument for nuclear because heat in general is widely available but thrown away across the board as it stands. Tons and tons of heat, very little usage. And it is possible to economically use, mind you. Here in Iceland for example we use the waste heat from our geothermal plants for all sorts of things - and that's not even as high temperature as most thermal plants' waste heat. We have a whole municipal hot water distribution system running to the lion's share of homes and businesses in the country.

You're mistaken. The main reason desal plants consume so much energy in pumping is not due to sea level changes, it's to provide sufficient osmotic pressure for the membranes. Freshwater is in a higher energy state than saltwater, and that energy must be provided in some way or another. In the brine desalination system, it's provided by the sun evaporating seawater to brine. In a conventional osmotic system it's electricity running pumps.

Sunlight is free**. Electricity is one of the most expensive forms of energy commonly used by humans.

** - Apart from your capturing system. But the beauty part here is how incredibly cheap the capture system is vs. how much solar energy it captures.

On the decision of whether to sacrifice an industry to provide the substance that people need to live, then YES.

And that's folks is why

And that's folks is why being an arse when you disagree with someone is usually mutually exclusive with being able to write proper English.

The flames in a house fire can of course be "over a thousand degrees F". Most air in a burning house is below the boiling point of water. But hey, let's just assume that your bucket is sitting right on top of the ignition source of your house and somehow remains directly in flames underneath it for half an hour. Gee, what sort of analogy could we have for a large metal pot-like thing sitting on some gas stove-like flames... oh yeah, how about a pot sitting on a gas stove (whose flames can also be "over a thousand degrees F")? Because anyone who's ever put a large pot full of water on the stove (for example for canning) can tell you that it will NOT boil off in half an hour.

And seriously, a steel bucket will be "gone"? Methinks you need to look up the melting point of steel.

Or for something cheaper, M-Disc in a bucket of water. Water shouldn't get significantly over boiling in a fire (as it loses its heat by boiling off), and M-Disc is rated to withstand boiling water and not degrade from long-term water immersion (they're burned not by modifying a photosensitive dye like in normal discs, but by literally etching a hard, inorganic layer)

All thermal power plants (which make up the vast majority of power plants) can do that, so that buys you nothing in favor of nuclear in particular.
 

*I'm* saying that when people and businesses are struggling to get water, and there's *one* industry out there that's only a tiny portion of the economy that's making everyone else suffer, then it's a situation that ought to be remedied.