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More than that, even generating the power from fossil fuels will work out more efficient. Burning petrol in a suitable turbine is what 60%? And internal combustion, buiot as a generator, still 50%.
Kind of wild that even when we don't need to confine the reaction, fusion is so difficult our bombs are mostly fission powered.
In a cylinder or ring built inside a dwarf planet radiation should not be a problem. A kilometre of ice is pretty good shielding.
Heat also depends on what environment you're replicating. British temperate rainforest is far lower insolation than tropical. And only 38% of sunlight is photosynthetically active. I think for Northern Europe equivalence we could get away with 5 layers?
Wondering about the use of a shellworld as a radiator. Build a large shell around a dwarf planet / moon and let atmospheric convection carry heat up to it, allowing for very large habitats without a particularly complex cooling system.
One design I haven't seen for space habitats is the spiral/scroll. If the cylinder is wide and the ceiling heights low enough, you can have multiple levels that are all one contiguous scroll. E.g. a 10km diameter cylinder with 50m ceilings could spiral round ten times with the innermost part having 90% of the gravity the outermost has. 300km long scroll. Make it 100km long embedded in a suitable iceteroid, and you have 30,000km2 of area, all one curled up sheet. Enough for wolves..?
Just solving deceleration would dramatically cut mass ratios. No need to accelerate the ions much, since they're there to provide drag against a magsail rather than pushing it. I wonder if neutral particles could be launched and then ionised by the ship? Could a suitable magsail achieve drag against a stream of say oxygen?
A certain level of gravity does help with plumbing. Maybe we can use diamagnetism to control water instead. Have actual baths and showers and ponds.
Trees could get pretty tall. And evolving to tree is carcinisation for plants. We could have dwarf planets covered in forests with human cities on the inside. In an inversion they may be lit from below.
It does make sense, 40K is a *very* low temperature. Even 90K is going to be 3.5x as dense as sea level.
New Horizons found far lower atmospheric loss rates for Pluto than previously estimated. Terraforming discourse may not have caught up yet.
Calliban,
The scale height decrease is compensated for by the greater area. On small bodies atmospheres need to be modeled with wedges rather than columns; it is no longer a thin layer over a sphere, but a sphere surrounding a smaller sphere.
As talked about before, a few microbars of oxygen should be enough for handling micrometeoroids. If a magnetic field can get us that far, it could prove a pretty useful pre paraterraforming step. At the least, we're going to want to avoid clathrates where we build, so some level of volatilisation will be necessary. Hopefully we can retain it.
Oxygen is paramagnetic. Perhaps strong enough magnetic fields would help to retain it? Otoh, they could have the opposite effect, accelerating oxygen molecules...
It occurs to me that bending the path of the oxygen enough is the key thing here. It doesnt matter if they're moving at escape velocity if they're moving downwards.
Water vapour, being paramagnetic, might be lost. But these worlds are cold, maybe it will freeze out long before reaching the exosphere.
By my estimates, melting through a cubic metre of ice dominated crust, with a starting temperature of 100K, would take about 600MJ of heat. A 1000MWth nuclear heat source could melt a 1km length, 100m wide circular tunnel every 54 days. So I think we could create a lot of habitable volume very quickly in this way. Such a device need not be very heavy. There would need to be some arrangement for pumping the water to the surface of the moon and dispersing it.
There are advantages to constructing centrifuges inside asteroids and dwarf planets. A centrifuge inside that tunnel would give us 30 hectares on the outermost level, with plenty of rad shielding and without the risk of destabilising wobble. Ideally it would be aligned with the axis of rotation of the body itself of course, otherwise we'll be losing energy constantly, though that may not be a major cost. Rotating at 4.2 RPM for 1g on the outer level. Could extend it throughout the entire body as energy allows, giving a very long, narrow city.
We don't need to give up reinforced concrete, yet. Basalt fibre mesh is commercially available. Not quite as good as steel in some applications, but a lot more durable and more similar to the concrete in expansion contraction etc. A basalt reinforced concrete road could last quite a long time.
(Been thinking recently on this for a bit of worldbuilding where the magic comes back in 2014. Has mage bred asphalt eating bacteria that force us to have either concrete or gravel roads. Among other things.)
Ammonia and ethane are under discussed. Not as lifting gases, but as means to alter buoyancy. A ballonet filled with ammonia is lighter than air; compress and condense that ammonia into a tank to collapse it, and it becomes heavier than air. Ethane is slightly heavier than air, so the range of possible lift would be less. Methane would I think be too tricky to condense to be viable.
In a way, concrete is simply taking the use of mortar to the extreme, where the mortar is mixed with tiny pieces of stone and then poured into shape. Less extreme than modern concrete is the Roman style, which uses bigger pieces of stone -- more rubble than gravel -- and is laid rather than poured. I definitely think the Roman style of construction is due a comeback, given that the labour and complexity should actually be lower than modern bricklaying if forms are used.
Would like to see more stone hexagonal pavers being cut. Hexagons are easier to lay than squares or rectangles due to the way they tessellate, and I like stone more than asphalt so if we can replace a lot of asphalt that'd be great.
There's a good argument for hybrid vehicles, or rather, for electric transmission, even without plugging them in. The efficiency losses are AFAIK outweighed by the ability to optimise the engine for power generation. Certainly at the least it would allow for trucks to use petrol, spreading the impact of fuel shortages instead of having a mad scramble for diesel.
NH4? Ammonium minerals? Not just water? Ooh that will be *very* useful.
Hmm. What implications does this have for CO2 atmospheres closer in? The triple point of co2 is around 300K. Perhaps areoforming minor worlds like the smaller moons (and Ceres) is more viable than we thought?
Such an atmosphere may also protect against micrometeorites, which would otherwise scuff up any lunar greenhouses we build. A useful tool for paraterraforming. Doable with a very thin atmosphere iirc. Like 0.1mb would do, or even less.
See also lunar KREEP. There's Potassium and Phosphate up there. Tbh I'd expect lunar rocks to have what we need, since it's made of the same stuff as Earth's crust and what would have boiled away. Iodine remains a potential difficulty; on Earth it is concentrated by various means. Mars and the ocean worlds might have it.
Worth considering that plants could accumulate elements that are at very low concentrations. Maybe we plant forests explicitly for this purpose.
Now that SpaceX is pivoting towards Luna first, and have proven rockets with more on the way, and a network of comm sats, and can launch humans into space and bring them back alive, this is a topic worth revisiting. How much *now* to set up a base? How much to start industrialising? What launch options for getting off Luna?
Mars may end up being the cheapest place to get elements such as copper and tin and silver for in space manufacturing. Ores only form on planets with hydrogeological processes that can concentrate them. That means Earth and maybe/likely Mars.
In the meantime, we'll have to haul them up from Earth, but fortunately Luna can provide nearly all the mass we need. Maybe even meteoric nickel-iron. And unlike Mars, it has a possible business case for mining, tourism, research, and orbital support services. Which are the reasons humans live in inhospitable Terran environments today. Though, given his haste, Musk may have a Fallen Angels scenario on his mind, where the bulk of humanity turn against space travel and there are only the people up there already to carry the flame to other worlds. A few thousand people should be viable genetically at least, especially given how highly selected they'd be. He may also have an Elysium scenario in mind too, given the talk of using orbital datacentres for the next great economic leap...
Once we have manufacturing on Luna we can start sending sollettas and iron nanorods to Mars, warm the place up somewhat before we get there.
Luna has a potential business case, with mining, tourism, research, support services and goods for orbit. Mars, does not. Luna also has plentiful solar power without an atmosphere to interfere.
With lunar railguns and refining, we can construct hulls for the big ships from space resources, and fuel them up with lunar oxygen. Also have the possibility of tethers with lunar rock for counterweights, maybe made of lunar basalt.
Shackleton City should be laid out on a hexagonal plan. Tesselated domes.
The private rape gang inquiry, organised and ran by Rupert Lowe MP (Great Yarmouth), is turning up and gathering quite a bit on the atrocities committed against native British girls - not just grooming and rape, trafficking also - by organised Pakistani community networks. It's... quite a lot. Not just the fact that so many in that community knew and facilitated it -- if we were to imprison or deport everyone who bears some responsibility, we'd almost certainly be accused of ethnic cleansing. But perhaps worse for the state is that it wasn't merely neglecting its duty to protect these girls, but actively assisting the rape networks and ensuring the girls could not be removed from their grasp. It's existential; the state is rapidly losing legitimacy and will have to rely solely on raw force if they don't pivot and root this rot out (they will not pivot and root this rot out).
Sounds like piston aircraft work for defense, turbines for attack from a distance (need the speed)?
Another area where piston aircraft should be viable is close air support / counter insurgency. Jet powered aircraft are used currently, but the speeds aren't above what you say piston engines can do.