If you want to travel more than 100 miles there is a pretty damn long wait in there.
Who are you that 17 minutes (the time for a Tesla supercharger to charge a Model S 100 miles) is a "pretty damn long wait"? Are you Batman chasing after the Joker? Regardless of your fuel source you'll lose an average of ten minutes every time you need to fill: in exiting, decelerating, going from the offramp to the gas station, pulling up to a pump (assuming there's no wait!), opening your gas tank, picking up and inserting the nozzle, filling, removing it, closing the gas cap, paying, exiting the gas station, returning to the onramp, taking the onramp, and accelerating back to full speed / merging in. A switch to an EV only increases the time for the "filling" part (and has more potential to reduce the "paying" part in that the charger has a digital communication link with the vehicle, making the prospect of autopay a lot more simpler than with gasoline vehicles)
And these things - as the other poster had made quite clear - are the extreme edge case. These only apply to long trips, which the majority of people only do rarely compared to daily driving. In your everyday life, an EV saves you time by letting you avoid trips to the gas station. And has a lot fewer parts to break. How much time does a breakdown cost you?
And by the way, you're supposed to stop regularly and walk around when driving, once every few hours. The US DoT recommends 15 minutes for every 2 hours driving. It's for safety - your own, and that of the people around you.
Back to the subject on hand: what force is everyone here hoping gets discovered? I'm really rooting for a space-dilating inflation gravity; that could potentially resolve all black hole paradoxes by eliminating singularities and disjoint regions of spacetime, explain inflation, and greatly illuminate the nature of the Big Bang.
A planet with the size and density of Earth must be rocky. It can't be a gas giant. It has the density of rock.
1. There are not only two categories of planets, "rocky", and "gas giant". Even in our own system there's also the ice giants, which are very different from the gas giants, being covered by a thick gas layer over massive central cores of "ices" and presumably some rock as well. Other systems may well have other categories.
2. The inner planets are devoid of large gas envelopes not because "sufficient light to be in the habital zone means gases leave", but because the solar wind - which is not some sort of 1:1 correlation with light output for stars - blew it out of the inner solar system before Earth the inner planets were even formed. Most of our volatiles were added back by the late heavy bombardment. When you're talking about exoplanets, first off, you're going to have different ratios of light output to solar wind intensity. You're secondly going to have a different planetary / stellar evolution history. And lastly you're going to have different post-bombardment formation histories. Bombardment from distant-formed bodies is what brings water, nitrogen (initially primarily as methane and ammonia), and the rarer noble gases.
The inner planets are not at some sort of "perfect gas-quantity equilibrium with the sun". If that were the case, Venus - closer to the sun and exposed to more intense solar winds - wouldn't have an atmosphere over 90 times as dense as Earth's. The solar wind (at least in our system) doesn't appreciably deplete heavier gases from Earth-sized planets even when they don't have a magnetic field, and has trouble depleting light gases even when they do.
It's more viable than Orion. Neither have a fully built rocket. Both are readily buildable without requiring any new "major advances" in science. But fission fragment propulsion can be done on a vastly smaller scale, and with a lot less uncertainties. Small scale testbeds have been made, which is more than can be said about Orion (which by definition can't be done on any scale less than "supermassive" and still support humans - around 40 million tons or more with 30m bombs in the original design, 400k tonnes with 300k bombs in Dyson's improved variant (not sure if the latter still counts as "Orion")). You can have a "satellite Orion" version as small as ~300 tonnes, but the accelerations would kill people, and the specific impulse is terrible.
Orion really is not a good design. Again: if you're going to insist on nuclear pulse propulsion, at least upgrade to Medusa. But I don't recommend pulse in general.
I''ll reiterate that quoting a "speed in which a technology can reach" is meaningless. A rocket that propels itself by firing pingpong balls out the back with an air cannon can reach relativistic speeds.... if you're willing to have uncountably many stages, each one vastly larger than the last, so that the size of your rocket ends up big enough to be seen from many light years away;). The figure that you're actually looking for is ISP (big I, little sp.... aka specific impulse), which determines what sort of scaling factor, which is proportional to the velocity of the exhaust. And fission fragment rockets have a much higher ISP than Orion. Orion (baselined for manned missions to Alpha Centauri) had an unimpressive ~6k sec with a theoretical maximum of 100k, while the first generation dusty fission fragment rocket has 527k sec ISP with a theoretical maximum of 1m. Also, like VASIMR, a FF rocket can trade ISP for thrust as desired by injecting gas into the exhaust stream. For example, if one wanted Orion's unimpressive ~6k ISP then with a FF rocket you could get an acceleration of about 0,01 g. The original Orion design called for average (not pulse) accelerations of 0.00003 g (Dyson's variant allowed for 1g acceleration, but when you're talking interstellar missions, there's no practical difference between 0,01g and 1g).
Basically in short, a fission fragment rocket is built around the same-old magnetic nozzle technology we use for a variety of magnetic propulsion methods. No new ground there. The trick is that the ions are the fission fragments from a nuclear reactor, which move at relativistic velocities. Normally fission fragments get thermalized (scattered until they lose their energy to their surroundings), but in a fission fragment reactor, the core is sparse or highly anisotropic or asymmetrical. Magnetic fields curve the fragments away from areas of high mass density to areas of low mass density, giving them the mean free path length they need to be ejected out the nozzle. Even your radioisotopes from daughter products contribute (except gamma & neutrinos).
There's a variety of approaches (mainly limited by the need to cool such a sparse core), such as rotating discs or wires, but my favorite design is the dusty plasma approach, which uses an electrostatically suspended dust (dust has a huge surface area to volume ratio). As a general rule, except for in some situations (usually with large scales), the mean neutron free path length is much larger than the diameter of the core ("reentrant"), so you need a moderator (Be, 13C, or D) or at least reflector on all sides to bounce the neutrons back through the core as many times as you can in order to reach criticality.
The technology keeps advancing... hopefully we'll start to see them deployed on missions in the next decade or two. Even ignoring the potential for interstellar missions, they'd make superb reusable interplanetary tugs, operating for decades and requiring only reaction mass (any gas) if you want to operate in high thrust / low ISP mode, and nothing at all to operate in low thrust / high ISP mode. It occurs to me that one could use waste CO2 from any manned missions as your reaction gas - about 4-5kg of CO2 for a 5-man crew per day.
Any propulsion technology can get you to any speed, the question is what sort of scaling factor you're willing to put up with.
And Orion is old tech; it's not really that great. Even as far as nuclear pulse propulsion goes. Medusa is much better in pretty much every regard (efficiency, ability to scale down, radiation exposure to the crew, shock absorption, etc). But non-pulse-propulsion techs are probably best. Check out, for example, fission fragment rockets. Scales down all the way to probe-size, no need for bombs, no "tons of energy released in a short burst", and much more efficient. In terms of performance, it's like a VASIMR engine operating at full thrust for years to decades, with no need for external power. If you went up to larger scales, you might be able to do a fast reactor version and get rid of the moderator and its associated cooling (the heaviest part); the current version has the core surrounded by a moderator (both to reflect the neutrons back in and moderate them down). With a large enough core you could ensure that most neutron free paths would be reflected within the core itself before fissioning (and any external reflector would scale proportional to r^2 anyway while the core mass scales at r^3). Still need to control the reactor temperature, but scattering from high-Z targets transfers a lot less energy to them.
In cosmic terms, I think "nearby" is fair. However, I always snicker a bit when planets get described as "earthlike" just because of their mass and distance from their star. We have counterexamples right in our own system. A distant astronomer using the same logic, upon discovering Venus would have declared its surface "Earthlike" and start going on about how it probably has oceans perfect for discovering life.
A body being "earthlike" requires a lot more than a similar mass and proper solar distance. Heck, do we even know that it's rocky? Proxima Centauri is a red dwarf - would it actually have blown away most of the volatiles during its formation like our sun did? Or by contrast maybe it's volatile-devoid. Earth was whalloped with volatile-containing rock during the Late Heavy Bombardment thanks to Jupiter. Does Proxima Centauri contain a Jupiter? Probably not. Also: my understanding of the habitable zone of red dwarfs is that they leave their surfaces too irradiated for LAWKI. Now, one could say, "well, it'd be in subsurface water". But you can make that argument for half a dozen bodies in our own solar system without requiring a 4+ light year journey.
Anything involving "massive orbital objects consuming unthinkable amounts of power" is not near-term technology.
Surface lasers... maybe. For extremely light probes, at least. COIL, with exhaust recovery and regeneration, could net you something like 20-30% system efficiency, with an excellent capital cost to power output ratio. The chlorine is recovered as potassium chloride, which returns to the needed potassium hydroxide and chlorine with electrolysis. The exhaust, scrubbed in water, yields iodic acid and other iodine compounds which are readily converted back to iodine with heat, and in the case of iodic acid, oxygen as a byproduct. Hydrogen peroxide is generated from H2 and O2. So the inputs that you need are H2, electricity, and heat. You get all of these things from hydrocarbon gassification and separation with cogeneration.
Maybe they meant antimatter-initiated microfission / microfusion? That's certainly much closer (although still not "current technology").
There's some work on significantly improving antimatter production efficiencies (a couple orders of magnitude), although that still doesn't bring us to starship-levels. And significant work on traps. We absolutely can trap positrons... the density is terrible, though. But then again, in starship it's mass density that really matters, not volume density. And I know that improvements to traps is a significant research field.
Re: engines, only positrons turn purely into gamma. Antiprotons turn into a mix of gamma and pions, and a fraction of the pions are charged. So you lose efficiency if you only funnel them out through a magnetic nozzle, but that is certainly current technology, magnetic nozzles for funneling charged particles are nothing new. As for gamma, it can be thermalized, but it requires a large rocket for a low thermalization efficiency and ISP below what would be desired. Perhaps combination with a ram scoop could make up for it.
So no, they're not current technology, you're absolutely right. But they might be at some point in the future.
I have often pondered using an artificial toroidal magnetosphere orbiting through Earths, or better Jupiter's, magnetosphere, to concentrate plasma enough to thermalize it and then use standard magnetic separation techniques along the central dense focus to remove the resultant antiprotons from the high-energy ions (thermalized = maxwellian distribution = some ions in the GeV range). Not sure how well it'd work in practice, though. You'd also get some limited fusion. The plasma in the Io torus is about 100eV (~1e9 K) but "dense", while the plasma further out is gets into the tens of keV (~e11) - hotter than ITER and tens of time hotter than the core of the sun, but increasingly sparse. There's also a variety of techniques one could do to increase the plasma temperature at the cost of decreasing the net flux. The natural flux in the vicinity of Io is about 2000 particles per cubic centimeter, which isn't much, but the research on artificial magnetospheres shows that you can inflate rather large (dozens to hundreds of kilometers) ones with reasonable masses (although toroidal would be expected to be more challenging... but you need a central focus)
All of that said... for interstellar missions, with near-term technology, my money would be on fission fragment propulsion.
I'm actually planning to buy it (and I rarely ever buy games, I normally spend my time working on projects) for exactly that reason. It's a game that by definition you can't complete. You'll never have the "perfect game", never have "seen everything. And thus there is no pressure or drive to complete that. It's something you can pick up and have your own experience in, and put down whenever you want.
The feeling of "what am I accomplishing?" strikes me as almost meta. What are you accomplishing by doing some "perfect game" in any game? It's a false sense of achievement. It accomplishes nothing, it achieves nothing.
In short, the fact that comes across as some sort of a meditative experience is what appeals to me most.
It is an option that has been proposed. But as you note, a planet covered in vast amounts of oxygen in contact with a deep layer of carbon all across its surface is... a bit unstable of a situation. You'd have to actually bury it, deep. It also does nothing for rotation, nor for providing more water. Also, even Venus's nitrogen levels are high compared to Earth. And even if you could stop flame, there would still be way too much oxygen. Providing way too much pressure**
** Depending on how much can be lost to reaction with surface minerals
As for collection, there's a number of different means. The key is that you have an aircraft that is, thanks to its propulsion system used to resist meridional drift (as well as natural turbulence) is plowing a sizable cross section through the mist. Which leads to a variety of possibilities.
1) Natural collection. Initially, the analysis of the VEGA data suggested that liquid was not condensing on the VEGA balloons. This has however been disputed in recent literature, with a reanalysis suggesting that it was indeed collecting, increasing the mass of the balloons until it started to drip off. And this was with a PTFE skin, which is incredibly hydrophobic. With the seams between the gores designed to channel any collected liquid to the base, drip-off collection would - if the modern interpretation of the VEGA data is correct - accumulate liquid surprisingly quickly. But more in-situ experiments on Venus are needed.
2) Enhanced collection. A variant on the former, one choses fabric specifically designed for maximizing collection, by having hydrophilic surfaces. This can be induced even on fluoropolymer skins by a variety of means, often involving as a first step either a chemical pretreatment or exposure to plasma or flame. As Venus's atmosphere is highly hydrophilic, hydrophilic surfaces should be even better than what was experienced by the VEGA balloons.
3) Open drip collection. One could run water or weak acid down along the gores or any other indentations (such as caused by catenary curtains or cable reinforcement) to allow direct adorption into the liquid. This however runs a risk of loss of water, such as to winds.
4) Packed bed collection. Wherein mist-rich gas is funnelled through a narrow space, one could use a packed bed to gain a higher collection ability with less risk of losing exposed liquid. Such locations could be a ring around the envelope at maximum diameter (potentially a dual use of a burble fence), in the wake of the prop(s) (potentially as cowlings or thrust vectoring), or along control surfaces.
5) Osmotic collection. similar to packed bed collection, liquid would be contained within channels separated from the outside air by a gas-permeable membrane
It's far too soon to be able to say which method would be optimal; it requires both Earth-based testing and testing by probes (with the dual-use purpose of collecting chemicals from the atmosphere for analysis). Different technologies present different potentials for recovery of different compounds as well. Natural condensation, for example, would likely collect significant H2SO4 but little HCl, HF, etc, as these latter gases are generally anhydrous on Venus. By contrast, any direct absorption into liquids would be expected to accumulate all andhydrous compounds as well. Accumulation across a membrane would be affected by the relative permeabilities of the chemicals to be absorbed.
Nothing in engineering is "simple". But I would be glad to go into further engineering details with you if you'd like, all the way down to what facilities already present on Earth could be used to assemble craft of different sizes, what suppliers exist for the fabrics, packaging arrangements within common spacecraft fairings, in-transit protection, deployment....
Name a topic.
Settling on Venus is at least as realistic as settling on Mars. In many ways it's a lot simpler and more sustainable.
Actually, both water and oxygen are surprisingly simple... thanks to that sulfuric acid that often is used against the concept of Venus as a destination. Simple heating of sulfuric acid first yields any dissolved water (Venus's H2SO4 is 75-85% concentration). Further heating decomposes H2SO4 into H2O and SO3. Further heating still in the presence of a catalyst decomposition SO3 into O2 and SO2. As far as industrial processes go, it's on the "easy" end.
One issue is that D/H ratio. Over 1% of the hydrogen is deuterium. While it's known that people can survive at high deuterium levels, there is some controversy over whether prolongued exposure may cause other health effects; for example, one study suggests increase incidence of depression at levels far below that encountered on Venus. Unlike most isotopic differences, deuterium has significantly different properties than light hydrogen. Deuterated drugs, for example, can have lifespans in the body many times higher than their non-deuterated equivalents. Deuterated plastics are often far more transparent than non-deuterated ones. Contrariwise, mixtures of deuterated and non-deuterated plastics are often highly opaque because deuterium changes the melting point enough for the plastic to fractionalize into an anisotropic mixture of varying densities (and thus refractive indices).
On the other hand, at a value of nearly $1k per kilogram, deuterium is a potential export product, if one can get launch costs down enough. And there's a rather clever way to do isotopic separation on Venus. You have to store power; this is a given, until one advances to the point of being able to make use of wind differentials at different altitudes. Rather than batteries, you can get a better mass ratio from fuel cells (hydrogen-chlorine fuel cells being a better option than hydrogen-oxygen due to the reduced overpotential requirements at the chlorine end and generally more favorable reaction dynamics). Also, unlike most H2-O2 PEMs, H2-Cl2 fuel cells tend to be readily reversible. The key is that, by far, the best technique for isotopic enrichment (in terms of enrichment factors) is electrolysis. It's not widely used on Earth because of how much energy it takes. But if you need to perform electrolysis either way to store electricity, it's no extra cost. You can also gain an enrichment factor on the recombination side as well. The only cost you have to pay for enrichment in this manner is the wiring of your fuel cell stack in a cascade, as well as extra tankage other plumbing mass for each of the intermediary stages (I could dig up my calculations at one point, I've already worked out how many stages you'd need and how many fuel cell layers would need to go to each stage in order to achieve a given voltage and given isotopic concentration at each end). If I remember right, you get about 17% of the hydrogen mass in the fuel cell system out on the de-enriched end every day.
Mars' loss of water is not comparable to Venus's. A primary indicator of water loss is the deterium-hydrogen ratio. Mars's is 5-7 times that of Earth. Venus's is 150-250 times that of Earth's.
I stopped reading the rest of your post when I hit the words "politically correct physicists".
On Earth it appears that the oceans put enough water into the crust as to make plate tectonics possible (the water lubricates fault lines. If Venus ever had plate tectonics, it probably stopped when the water evaporated.
Why did you just defend that point by linking to an article that states, and I quote, "Earth may be a borderline case, owing its tectonic activity to abundant water [68] (silica and water form a deep eutectic.)"?
Re: Venus's magnetic field: to be fair, 1) our current understanding of dynamo theory is imperfect and frequently fails to yield accurate values for bodies in the solar system, and 2) rotation does play a factor on field strength. Re #1: Mercury's field is an order of magnitude weaker than predicted; Venus's is of course effectively absent; sufficient convection for a dynamo on Ganymede is not expected; etc.
Basically, picture dimly lighting your house with halogen lights (for a rough approximation of the visible spectrum curve)... that's basically what things would look like on the surface of Venus. With a relatively short (although not extremely short) visibility range (I don't remember the number off the top of my head, I want to say a few hundred meters).
Not true. The lighting on the surface of Venus during daytime is "gloomy", somewhat like being in a dust storm in the evening. But it absolutely is present during the day (and not at night). I even read one paper that showed that you could actually have solar-powered surface probes. You have to be very careful in your panel selection to find one that will generate anything under those temperatures and light conditions, but you can produce a trickle, for low-power scientific equipment.
The surface temperature varies little from day to night, and cloudtop day/night temperature differences are fairly earthlike. A thick atmosphere does a good job of transferring heat.
Rotation could be to blame for a lot of Venus's problems, however. It could explain Venus's lack of anything more than an induced magnetic field. Which of course leaves it vulnerable to erosion by the solar wind.
Interetingly enough, if you were to eject most of Venus's atmosphere at a couple dozen km/s (if I'm remembering the numbers right), you could impart enough torque to get the planet up to Earthlike rotation speeds. So in terms of "megaengineering" for terraforming, what you effectively need is a solar-driven rocket engine using the atmosphere as propellant, with the structure providing compression and the greenhouse effect (IR reflection / vis transmission), the atmosphere providing absorption inside the "chamber", and lofting from any combination of buoyancy and skin drag. Hydrogen could be returned to Venus via similar systems on gas giants. It's of course a lot more complicated than that in reality, and the concept of construction of such a massive structure is purely within the realms of sci-fi for the forseeable future.
Indeed. It amazes me how much the surface reminds me of many parts of Iceland, where I live. Chemically, Iceland is the closest place on Earth to at least Venus's lowland plains (which appear to be an extreme form of MORB, highly weathered... which is actually rather neat from a minerological perspective)
No, that's not "about it". The things that are earthlike include:
* Temperature
* Pressure
* Gravity
* Radiation shielding (compared to other destinations)
* Sunlight levels
* Atmospheric turbulence
The environment is amazingly earthlike, except for the chemistry. And concerning the chemistry....
The air is still unbreathable and full of sulphuric acid.
The phrase "full of sulfuric acid" gives completely the wrong impression. The sulfuric acid mists in the cloud deck at reasonable heights (~54km., give or take a couple km) are on the order of half a dozen ppm. They're not much higher than the OSHA standards for breathing sulfuric acid mists during an 8 hour shift. Now, Venus's H2SO4 mists are a higher concentration than those on Earth, and there are also anhydrous acidic components. But comparisons to a bath in sulfuric acid are totally inappropriate. It's more like a bad smog or vog (in fact, it is a bad vog).
Oh, and sulphuric acid isn't very friendly to most building materials either.
When you're talking about plastics (were you actually thinking that one would make a blimp's skin out of steel?), sulfuric acid is well tolerated by a large number, if not the majority of plastics. Organic solvents are much more concerning - I'd have much greater concerns for a blimp on Titan. Some fluoropolymers, like FEP and PTFE, are so chemical resistant that they're easier much defined by what does hurt them than what doesn't.
Realistic flight envelopes are not a single component. You generally will have an outer anti-corrosion layer (generally a fluoropolymer... the least fluorinated that provides the desired properties; ECTFE or PCTFE would be excellent), with one or more layers for permeation resistance and strength (generally biaxially-oriented when strength is of concern, like BoPET); for extra permeation resistance, something like EVOH or PVDC), optionally an inner layer (condensation control, anti-fouling, melt-through lamination, etc), optionally adhesive layers (such as EVA-based), and fiber reinforcement (vectran is popular for Venus proposals, although would be somewhat difficult for local production; on the opposite end of the spectrum, the easiest possibility for local production would be UHMWPE, but you'd need to ensure proper UV resistance and that the film components are compatible with the inevitable creep... though to be fair vectran also needs UV control) (there are countless fibers in-between with varying tensile, UV, chemical, creep, etc properties).
Beyond the basic skin you also need ballonets; most likely an additional phase-change envelope for altitude stability; catenary curtains and cables to distribute the weight to hanging structures; and in some cases, where objects need to be kept a minimum distance away from the envelope (such as propulsion), collapsible trusses. You also need mist collection for local propellant production (there are many different architectures, but they're all built around the fact that all of Venus's mists are highly hydrophilic and thus readily condense into water (through membranes or exposed) and onto hydrophilic surfaces. Lastly, if you use a ballute approach (for any combination of reentry, atmospheric deceleration, and/or initial inflation), you need a burble fence (which could potentially double as mist collection, depending on the architecture).
In cases where you might have exposed metal - such as propulsion motors (although even that isn't an inherent requirement) - there are a lot of alloys considered to be fine in Venus-conditions, and indeed which have been used on Venus probes in the past. An example includes Hastelloy C22. You may have noticed that here on Earth, metals in industry are frequently exposed to extremely corrosive chemical production environments for very long times. You design to your environment. A more
The volatiles demonstrably do not "go off with pre-heating". That doesn't happen in volcanoes, and it's not going to happen in an asteroid.
Columnar basalt demonstrably does not "anneal during slow cooling". The columns form during slow cooling.
Differentiation is driven because not all components are readily compatible with each other in the newly cooled matrix, and is responsive to thermal gradients as much as gravity.
Spend some living in a volcanically active location like I do, then get back to me.
The 7 individuals led to a mouse study, which was statistically significant.
Of course, mouse studies don't always apply to humans. But you have suggestive evidence on humans, and statistically significant evidence on mice. That's not something to ignore.
Right, because when a team meets to decide a low-risk landing site, they're all going to collectively sit down and decide, "Let's navigate a habitat down this gaping hole onto who-knows-what kind of bottom and hope we don't induce a collapse in the process, then have our crew members climbing in and out all day."
When it comes to space, the KISS principle applies way more in reality than in sci-fi. You build things here on earth. You only even do seemingly simple in-space activities like connecting premade modules together when it's absolutely necessary. It's cheaper and more reliable to do build on Earth and pay extra in launch costs than to engineer some sort of exotic assembly process in some offworld location to the point where you can trust it (with a million things that can go wrong, you really have to be confident about each one, otherwise you're statistically guaranteeing yourself failure). Heck, even the things one might see as "trivial" in-situ resource extractions - say, ice mining for hydrogen production - are looked at with a wary eye. Many mission designs just simply call for bring the hydrogen from Earth (getting oxygen is simpler, however - solid-oxide fuel cells like MOXIE are considered relatively reliable, and Mars's atmosphere a relatively consistent/trustworthy feedstock; Mars 2020 will be testing it in-situ for the first time).
Slashdot Mirror
Who are you that 17 minutes (the time for a Tesla supercharger to charge a Model S 100 miles) is a "pretty damn long wait"? Are you Batman chasing after the Joker? Regardless of your fuel source you'll lose an average of ten minutes every time you need to fill: in exiting, decelerating, going from the offramp to the gas station, pulling up to a pump (assuming there's no wait!), opening your gas tank, picking up and inserting the nozzle, filling, removing it, closing the gas cap, paying, exiting the gas station, returning to the onramp, taking the onramp, and accelerating back to full speed / merging in. A switch to an EV only increases the time for the "filling" part (and has more potential to reduce the "paying" part in that the charger has a digital communication link with the vehicle, making the prospect of autopay a lot more simpler than with gasoline vehicles)
And these things - as the other poster had made quite clear - are the extreme edge case. These only apply to long trips, which the majority of people only do rarely compared to daily driving. In your everyday life, an EV saves you time by letting you avoid trips to the gas station. And has a lot fewer parts to break. How much time does a breakdown cost you?
And by the way, you're supposed to stop regularly and walk around when driving, once every few hours. The US DoT recommends 15 minutes for every 2 hours driving. It's for safety - your own, and that of the people around you.
Pony science? Which pony, exactly? ;)
Back to the subject on hand: what force is everyone here hoping gets discovered? I'm really rooting for a space-dilating inflation gravity; that could potentially resolve all black hole paradoxes by eliminating singularities and disjoint regions of spacetime, explain inflation, and greatly illuminate the nature of the Big Bang.
1. There are not only two categories of planets, "rocky", and "gas giant". Even in our own system there's also the ice giants, which are very different from the gas giants, being covered by a thick gas layer over massive central cores of "ices" and presumably some rock as well. Other systems may well have other categories.
2. The inner planets are devoid of large gas envelopes not because "sufficient light to be in the habital zone means gases leave", but because the solar wind - which is not some sort of 1:1 correlation with light output for stars - blew it out of the inner solar system before Earth the inner planets were even formed. Most of our volatiles were added back by the late heavy bombardment. When you're talking about exoplanets, first off, you're going to have different ratios of light output to solar wind intensity. You're secondly going to have a different planetary / stellar evolution history. And lastly you're going to have different post-bombardment formation histories. Bombardment from distant-formed bodies is what brings water, nitrogen (initially primarily as methane and ammonia), and the rarer noble gases.
The inner planets are not at some sort of "perfect gas-quantity equilibrium with the sun". If that were the case, Venus - closer to the sun and exposed to more intense solar winds - wouldn't have an atmosphere over 90 times as dense as Earth's. The solar wind (at least in our system) doesn't appreciably deplete heavier gases from Earth-sized planets even when they don't have a magnetic field, and has trouble depleting light gases even when they do.
It's more viable than Orion. Neither have a fully built rocket. Both are readily buildable without requiring any new "major advances" in science. But fission fragment propulsion can be done on a vastly smaller scale, and with a lot less uncertainties. Small scale testbeds have been made, which is more than can be said about Orion (which by definition can't be done on any scale less than "supermassive" and still support humans - around 40 million tons or more with 30m bombs in the original design, 400k tonnes with 300k bombs in Dyson's improved variant (not sure if the latter still counts as "Orion")). You can have a "satellite Orion" version as small as ~300 tonnes, but the accelerations would kill people, and the specific impulse is terrible.
Orion really is not a good design. Again: if you're going to insist on nuclear pulse propulsion, at least upgrade to Medusa. But I don't recommend pulse in general.
I''ll reiterate that quoting a "speed in which a technology can reach" is meaningless. A rocket that propels itself by firing pingpong balls out the back with an air cannon can reach relativistic speeds.... if you're willing to have uncountably many stages, each one vastly larger than the last, so that the size of your rocket ends up big enough to be seen from many light years away ;). The figure that you're actually looking for is ISP (big I, little sp.... aka specific impulse), which determines what sort of scaling factor, which is proportional to the velocity of the exhaust. And fission fragment rockets have a much higher ISP than Orion. Orion (baselined for manned missions to Alpha Centauri) had an unimpressive ~6k sec with a theoretical maximum of 100k, while the first generation dusty fission fragment rocket has 527k sec ISP with a theoretical maximum of 1m. Also, like VASIMR, a FF rocket can trade ISP for thrust as desired by injecting gas into the exhaust stream. For example, if one wanted Orion's unimpressive ~6k ISP then with a FF rocket you could get an acceleration of about 0,01 g. The original Orion design called for average (not pulse) accelerations of 0.00003 g (Dyson's variant allowed for 1g acceleration, but when you're talking interstellar missions, there's no practical difference between 0,01g and 1g).
Basically in short, a fission fragment rocket is built around the same-old magnetic nozzle technology we use for a variety of magnetic propulsion methods. No new ground there. The trick is that the ions are the fission fragments from a nuclear reactor, which move at relativistic velocities. Normally fission fragments get thermalized (scattered until they lose their energy to their surroundings), but in a fission fragment reactor, the core is sparse or highly anisotropic or asymmetrical. Magnetic fields curve the fragments away from areas of high mass density to areas of low mass density, giving them the mean free path length they need to be ejected out the nozzle. Even your radioisotopes from daughter products contribute (except gamma & neutrinos).
There's a variety of approaches (mainly limited by the need to cool such a sparse core), such as rotating discs or wires, but my favorite design is the dusty plasma approach, which uses an electrostatically suspended dust (dust has a huge surface area to volume ratio). As a general rule, except for in some situations (usually with large scales), the mean neutron free path length is much larger than the diameter of the core ("reentrant"), so you need a moderator (Be, 13C, or D) or at least reflector on all sides to bounce the neutrons back through the core as many times as you can in order to reach criticality.
The technology keeps advancing... hopefully we'll start to see them deployed on missions in the next decade or two. Even ignoring the potential for interstellar missions, they'd make superb reusable interplanetary tugs, operating for decades and requiring only reaction mass (any gas) if you want to operate in high thrust / low ISP mode, and nothing at all to operate in low thrust / high ISP mode. It occurs to me that one could use waste CO2 from any manned missions as your reaction gas - about 4-5kg of CO2 for a 5-man crew per day.
Any propulsion technology can get you to any speed, the question is what sort of scaling factor you're willing to put up with.
And Orion is old tech; it's not really that great. Even as far as nuclear pulse propulsion goes. Medusa is much better in pretty much every regard (efficiency, ability to scale down, radiation exposure to the crew, shock absorption, etc). But non-pulse-propulsion techs are probably best. Check out, for example, fission fragment rockets. Scales down all the way to probe-size, no need for bombs, no "tons of energy released in a short burst", and much more efficient. In terms of performance, it's like a VASIMR engine operating at full thrust for years to decades, with no need for external power. If you went up to larger scales, you might be able to do a fast reactor version and get rid of the moderator and its associated cooling (the heaviest part); the current version has the core surrounded by a moderator (both to reflect the neutrons back in and moderate them down). With a large enough core you could ensure that most neutron free paths would be reflected within the core itself before fissioning (and any external reflector would scale proportional to r^2 anyway while the core mass scales at r^3). Still need to control the reactor temperature, but scattering from high-Z targets transfers a lot less energy to them.
In cosmic terms, I think "nearby" is fair. However, I always snicker a bit when planets get described as "earthlike" just because of their mass and distance from their star. We have counterexamples right in our own system. A distant astronomer using the same logic, upon discovering Venus would have declared its surface "Earthlike" and start going on about how it probably has oceans perfect for discovering life.
A body being "earthlike" requires a lot more than a similar mass and proper solar distance. Heck, do we even know that it's rocky? Proxima Centauri is a red dwarf - would it actually have blown away most of the volatiles during its formation like our sun did? Or by contrast maybe it's volatile-devoid. Earth was whalloped with volatile-containing rock during the Late Heavy Bombardment thanks to Jupiter. Does Proxima Centauri contain a Jupiter? Probably not. Also: my understanding of the habitable zone of red dwarfs is that they leave their surfaces too irradiated for LAWKI. Now, one could say, "well, it'd be in subsurface water". But you can make that argument for half a dozen bodies in our own solar system without requiring a 4+ light year journey.
Anything involving "massive orbital objects consuming unthinkable amounts of power" is not near-term technology.
Surface lasers... maybe. For extremely light probes, at least. COIL, with exhaust recovery and regeneration, could net you something like 20-30% system efficiency, with an excellent capital cost to power output ratio. The chlorine is recovered as potassium chloride, which returns to the needed potassium hydroxide and chlorine with electrolysis. The exhaust, scrubbed in water, yields iodic acid and other iodine compounds which are readily converted back to iodine with heat, and in the case of iodic acid, oxygen as a byproduct. Hydrogen peroxide is generated from H2 and O2. So the inputs that you need are H2, electricity, and heat. You get all of these things from hydrocarbon gassification and separation with cogeneration.
Maybe they meant antimatter-initiated microfission / microfusion? That's certainly much closer (although still not "current technology").
There's some work on significantly improving antimatter production efficiencies (a couple orders of magnitude), although that still doesn't bring us to starship-levels. And significant work on traps. We absolutely can trap positrons... the density is terrible, though. But then again, in starship it's mass density that really matters, not volume density. And I know that improvements to traps is a significant research field.
Re: engines, only positrons turn purely into gamma. Antiprotons turn into a mix of gamma and pions, and a fraction of the pions are charged. So you lose efficiency if you only funnel them out through a magnetic nozzle, but that is certainly current technology, magnetic nozzles for funneling charged particles are nothing new. As for gamma, it can be thermalized, but it requires a large rocket for a low thermalization efficiency and ISP below what would be desired. Perhaps combination with a ram scoop could make up for it.
So no, they're not current technology, you're absolutely right. But they might be at some point in the future.
I have often pondered using an artificial toroidal magnetosphere orbiting through Earths, or better Jupiter's, magnetosphere, to concentrate plasma enough to thermalize it and then use standard magnetic separation techniques along the central dense focus to remove the resultant antiprotons from the high-energy ions (thermalized = maxwellian distribution = some ions in the GeV range). Not sure how well it'd work in practice, though. You'd also get some limited fusion. The plasma in the Io torus is about 100eV (~1e9 K) but "dense", while the plasma further out is gets into the tens of keV (~e11) - hotter than ITER and tens of time hotter than the core of the sun, but increasingly sparse. There's also a variety of techniques one could do to increase the plasma temperature at the cost of decreasing the net flux. The natural flux in the vicinity of Io is about 2000 particles per cubic centimeter, which isn't much, but the research on artificial magnetospheres shows that you can inflate rather large (dozens to hundreds of kilometers) ones with reasonable masses (although toroidal would be expected to be more challenging... but you need a central focus)
All of that said... for interstellar missions, with near-term technology, my money would be on fission fragment propulsion.
I'm actually planning to buy it (and I rarely ever buy games, I normally spend my time working on projects) for exactly that reason. It's a game that by definition you can't complete. You'll never have the "perfect game", never have "seen everything. And thus there is no pressure or drive to complete that. It's something you can pick up and have your own experience in, and put down whenever you want.
The feeling of "what am I accomplishing?" strikes me as almost meta. What are you accomplishing by doing some "perfect game" in any game? It's a false sense of achievement. It accomplishes nothing, it achieves nothing.
In short, the fact that comes across as some sort of a meditative experience is what appeals to me most.
Ed: that should read Sabatier synthesis, not Fischer-Tropsch.
It is an option that has been proposed. But as you note, a planet covered in vast amounts of oxygen in contact with a deep layer of carbon all across its surface is... a bit unstable of a situation. You'd have to actually bury it, deep. It also does nothing for rotation, nor for providing more water. Also, even Venus's nitrogen levels are high compared to Earth. And even if you could stop flame, there would still be way too much oxygen. Providing way too much pressure**
** Depending on how much can be lost to reaction with surface minerals
As for collection, there's a number of different means. The key is that you have an aircraft that is, thanks to its propulsion system used to resist meridional drift (as well as natural turbulence) is plowing a sizable cross section through the mist. Which leads to a variety of possibilities.
1) Natural collection. Initially, the analysis of the VEGA data suggested that liquid was not condensing on the VEGA balloons. This has however been disputed in recent literature, with a reanalysis suggesting that it was indeed collecting, increasing the mass of the balloons until it started to drip off. And this was with a PTFE skin, which is incredibly hydrophobic. With the seams between the gores designed to channel any collected liquid to the base, drip-off collection would - if the modern interpretation of the VEGA data is correct - accumulate liquid surprisingly quickly. But more in-situ experiments on Venus are needed.
2) Enhanced collection. A variant on the former, one choses fabric specifically designed for maximizing collection, by having hydrophilic surfaces. This can be induced even on fluoropolymer skins by a variety of means, often involving as a first step either a chemical pretreatment or exposure to plasma or flame. As Venus's atmosphere is highly hydrophilic, hydrophilic surfaces should be even better than what was experienced by the VEGA balloons.
3) Open drip collection. One could run water or weak acid down along the gores or any other indentations (such as caused by catenary curtains or cable reinforcement) to allow direct adorption into the liquid. This however runs a risk of loss of water, such as to winds.
4) Packed bed collection. Wherein mist-rich gas is funnelled through a narrow space, one could use a packed bed to gain a higher collection ability with less risk of losing exposed liquid. Such locations could be a ring around the envelope at maximum diameter (potentially a dual use of a burble fence), in the wake of the prop(s) (potentially as cowlings or thrust vectoring), or along control surfaces.
5) Osmotic collection. similar to packed bed collection, liquid would be contained within channels separated from the outside air by a gas-permeable membrane
It's far too soon to be able to say which method would be optimal; it requires both Earth-based testing and testing by probes (with the dual-use purpose of collecting chemicals from the atmosphere for analysis). Different technologies present different potentials for recovery of different compounds as well. Natural condensation, for example, would likely collect significant H2SO4 but little HCl, HF, etc, as these latter gases are generally anhydrous on Venus. By contrast, any direct absorption into liquids would be expected to accumulate all andhydrous compounds as well. Accumulation across a membrane would be affected by the relative permeabilities of the chemicals to be absorbed.
Nothing in engineering is "simple". But I would be glad to go into further engineering details with you if you'd like, all the way down to what facilities already present on Earth could be used to assemble craft of different sizes, what suppliers exist for the fabrics, packaging arrangements within common spacecraft fairings, in-transit protection, deployment....
Name a topic.
Settling on Venus is at least as realistic as settling on Mars. In many ways it's a lot simpler and more sustainable.
Actually, both water and oxygen are surprisingly simple... thanks to that sulfuric acid that often is used against the concept of Venus as a destination. Simple heating of sulfuric acid first yields any dissolved water (Venus's H2SO4 is 75-85% concentration). Further heating decomposes H2SO4 into H2O and SO3. Further heating still in the presence of a catalyst decomposition SO3 into O2 and SO2. As far as industrial processes go, it's on the "easy" end.
One issue is that D/H ratio. Over 1% of the hydrogen is deuterium. While it's known that people can survive at high deuterium levels, there is some controversy over whether prolongued exposure may cause other health effects; for example, one study suggests increase incidence of depression at levels far below that encountered on Venus. Unlike most isotopic differences, deuterium has significantly different properties than light hydrogen. Deuterated drugs, for example, can have lifespans in the body many times higher than their non-deuterated equivalents. Deuterated plastics are often far more transparent than non-deuterated ones. Contrariwise, mixtures of deuterated and non-deuterated plastics are often highly opaque because deuterium changes the melting point enough for the plastic to fractionalize into an anisotropic mixture of varying densities (and thus refractive indices).
On the other hand, at a value of nearly $1k per kilogram, deuterium is a potential export product, if one can get launch costs down enough. And there's a rather clever way to do isotopic separation on Venus. You have to store power; this is a given, until one advances to the point of being able to make use of wind differentials at different altitudes. Rather than batteries, you can get a better mass ratio from fuel cells (hydrogen-chlorine fuel cells being a better option than hydrogen-oxygen due to the reduced overpotential requirements at the chlorine end and generally more favorable reaction dynamics). Also, unlike most H2-O2 PEMs, H2-Cl2 fuel cells tend to be readily reversible. The key is that, by far, the best technique for isotopic enrichment (in terms of enrichment factors) is electrolysis. It's not widely used on Earth because of how much energy it takes. But if you need to perform electrolysis either way to store electricity, it's no extra cost. You can also gain an enrichment factor on the recombination side as well. The only cost you have to pay for enrichment in this manner is the wiring of your fuel cell stack in a cascade, as well as extra tankage other plumbing mass for each of the intermediary stages (I could dig up my calculations at one point, I've already worked out how many stages you'd need and how many fuel cell layers would need to go to each stage in order to achieve a given voltage and given isotopic concentration at each end). If I remember right, you get about 17% of the hydrogen mass in the fuel cell system out on the de-enriched end every day.
Mars' loss of water is not comparable to Venus's. A primary indicator of water loss is the deterium-hydrogen ratio. Mars's is 5-7 times that of Earth. Venus's is 150-250 times that of Earth's.
I stopped reading the rest of your post when I hit the words "politically correct physicists".
Why did you just defend that point by linking to an article that states, and I quote, "Earth may be a borderline case, owing its tectonic activity to abundant water [68] (silica and water form a deep eutectic.)"?
Re: Venus's magnetic field: to be fair, 1) our current understanding of dynamo theory is imperfect and frequently fails to yield accurate values for bodies in the solar system, and 2) rotation does play a factor on field strength. Re #1: Mercury's field is an order of magnitude weaker than predicted; Venus's is of course effectively absent; sufficient convection for a dynamo on Ganymede is not expected; etc.
Basically, picture dimly lighting your house with halogen lights (for a rough approximation of the visible spectrum curve)... that's basically what things would look like on the surface of Venus. With a relatively short (although not extremely short) visibility range (I don't remember the number off the top of my head, I want to say a few hundred meters).
Not true. The lighting on the surface of Venus during daytime is "gloomy", somewhat like being in a dust storm in the evening. But it absolutely is present during the day (and not at night). I even read one paper that showed that you could actually have solar-powered surface probes. You have to be very careful in your panel selection to find one that will generate anything under those temperatures and light conditions, but you can produce a trickle, for low-power scientific equipment.
The surface temperature varies little from day to night, and cloudtop day/night temperature differences are fairly earthlike. A thick atmosphere does a good job of transferring heat.
Rotation could be to blame for a lot of Venus's problems, however. It could explain Venus's lack of anything more than an induced magnetic field. Which of course leaves it vulnerable to erosion by the solar wind.
Interetingly enough, if you were to eject most of Venus's atmosphere at a couple dozen km/s (if I'm remembering the numbers right), you could impart enough torque to get the planet up to Earthlike rotation speeds. So in terms of "megaengineering" for terraforming, what you effectively need is a solar-driven rocket engine using the atmosphere as propellant, with the structure providing compression and the greenhouse effect (IR reflection / vis transmission), the atmosphere providing absorption inside the "chamber", and lofting from any combination of buoyancy and skin drag. Hydrogen could be returned to Venus via similar systems on gas giants. It's of course a lot more complicated than that in reality, and the concept of construction of such a massive structure is purely within the realms of sci-fi for the forseeable future.
Indeed. It amazes me how much the surface reminds me of many parts of Iceland, where I live. Chemically, Iceland is the closest place on Earth to at least Venus's lowland plains (which appear to be an extreme form of MORB, highly weathered... which is actually rather neat from a minerological perspective)
No, that's not "about it". The things that are earthlike include:
* Temperature
* Pressure
* Gravity
* Radiation shielding (compared to other destinations)
* Sunlight levels
* Atmospheric turbulence
The environment is amazingly earthlike, except for the chemistry. And concerning the chemistry....
The phrase "full of sulfuric acid" gives completely the wrong impression. The sulfuric acid mists in the cloud deck at reasonable heights (~54km., give or take a couple km) are on the order of half a dozen ppm. They're not much higher than the OSHA standards for breathing sulfuric acid mists during an 8 hour shift. Now, Venus's H2SO4 mists are a higher concentration than those on Earth, and there are also anhydrous acidic components. But comparisons to a bath in sulfuric acid are totally inappropriate. It's more like a bad smog or vog (in fact, it is a bad vog).
When you're talking about plastics (were you actually thinking that one would make a blimp's skin out of steel?), sulfuric acid is well tolerated by a large number, if not the majority of plastics. Organic solvents are much more concerning - I'd have much greater concerns for a blimp on Titan. Some fluoropolymers, like FEP and PTFE, are so chemical resistant that they're easier much defined by what does hurt them than what doesn't.
Realistic flight envelopes are not a single component. You generally will have an outer anti-corrosion layer (generally a fluoropolymer... the least fluorinated that provides the desired properties; ECTFE or PCTFE would be excellent), with one or more layers for permeation resistance and strength (generally biaxially-oriented when strength is of concern, like BoPET); for extra permeation resistance, something like EVOH or PVDC), optionally an inner layer (condensation control, anti-fouling, melt-through lamination, etc), optionally adhesive layers (such as EVA-based), and fiber reinforcement (vectran is popular for Venus proposals, although would be somewhat difficult for local production; on the opposite end of the spectrum, the easiest possibility for local production would be UHMWPE, but you'd need to ensure proper UV resistance and that the film components are compatible with the inevitable creep... though to be fair vectran also needs UV control) (there are countless fibers in-between with varying tensile, UV, chemical, creep, etc properties).
Beyond the basic skin you also need ballonets; most likely an additional phase-change envelope for altitude stability; catenary curtains and cables to distribute the weight to hanging structures; and in some cases, where objects need to be kept a minimum distance away from the envelope (such as propulsion), collapsible trusses. You also need mist collection for local propellant production (there are many different architectures, but they're all built around the fact that all of Venus's mists are highly hydrophilic and thus readily condense into water (through membranes or exposed) and onto hydrophilic surfaces. Lastly, if you use a ballute approach (for any combination of reentry, atmospheric deceleration, and/or initial inflation), you need a burble fence (which could potentially double as mist collection, depending on the architecture).
In cases where you might have exposed metal - such as propulsion motors (although even that isn't an inherent requirement) - there are a lot of alloys considered to be fine in Venus-conditions, and indeed which have been used on Venus probes in the past. An example includes Hastelloy C22. You may have noticed that here on Earth, metals in industry are frequently exposed to extremely corrosive chemical production environments for very long times. You design to your environment. A more
The volatiles demonstrably do not "go off with pre-heating". That doesn't happen in volcanoes, and it's not going to happen in an asteroid.
Columnar basalt demonstrably does not "anneal during slow cooling". The columns form during slow cooling.
Differentiation is driven because not all components are readily compatible with each other in the newly cooled matrix, and is responsive to thermal gradients as much as gravity.
Spend some living in a volcanically active location like I do, then get back to me.
Just good old-fashioned Space Nuns, of course.
The 7 individuals led to a mouse study, which was statistically significant.
Of course, mouse studies don't always apply to humans. But you have suggestive evidence on humans, and statistically significant evidence on mice. That's not something to ignore.
Right, because when a team meets to decide a low-risk landing site, they're all going to collectively sit down and decide, "Let's navigate a habitat down this gaping hole onto who-knows-what kind of bottom and hope we don't induce a collapse in the process, then have our crew members climbing in and out all day."
When it comes to space, the KISS principle applies way more in reality than in sci-fi. You build things here on earth. You only even do seemingly simple in-space activities like connecting premade modules together when it's absolutely necessary. It's cheaper and more reliable to do build on Earth and pay extra in launch costs than to engineer some sort of exotic assembly process in some offworld location to the point where you can trust it (with a million things that can go wrong, you really have to be confident about each one, otherwise you're statistically guaranteeing yourself failure). Heck, even the things one might see as "trivial" in-situ resource extractions - say, ice mining for hydrogen production - are looked at with a wary eye. Many mission designs just simply call for bring the hydrogen from Earth (getting oxygen is simpler, however - solid-oxide fuel cells like MOXIE are considered relatively reliable, and Mars's atmosphere a relatively consistent/trustworthy feedstock; Mars 2020 will be testing it in-situ for the first time).