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  1. - Top - End - #61
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    Default Re: Terraforming planets/moons

    Venus also runs into the problem of being outside the habitable zone, while Mars is inside. While Mars would require a lot of work to get there, assuming you could fix its magnetic field and keep an atmosphere, it could stay livable. Venus... wouldn't. It would heat up too much, even if you killed the greenhouse effect somehow.
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    Default Re: Terraforming planets/moons

    Quote Originally Posted by Mark Hall View Post
    Venus also runs into the problem of being outside the habitable zone, while Mars is inside. While Mars would require a lot of work to get there, assuming you could fix its magnetic field and keep an atmosphere, it could stay livable. Venus... wouldn't. It would heat up too much, even if you killed the greenhouse effect somehow.
    I'm somewhat skeptical about that. The mean surface temperature on Earth is probably between 20 and 30 degrees Celcius (Celcius 0 is the freezing point of water at standard pressure, Celcius 100 is the boiling point of water). Mars is a lot further from the Sun. A mean temperature below 0 degrees Celcius is not what I would think of as habitable. Humans as we are can't live in 70 degrees Celcius, but we are ridiculously strongly adapted to Earth, I think something Earth derived could live in those temperatures.

    Having just taken a swift glance at it, I don't understand that graphic at all.
    Last edited by halfeye; 2019-02-09 at 02:28 PM.
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    Default Re: Terraforming planets/moons

    Quote Originally Posted by halfeye View Post
    I'm somewhat skeptical about that. The mean surface temperature on Earth is probably between 20 and 30 degrees Celcius (Celcius 0 is the freezing point of water at standard pressure, Celcius 100 is the boiling point of water).
    16C, actually.There are obviously parts much hotter and colder than that, but if you average the temperatures across the entire surface, that's what you get.

    @Mark Hall: there are as many estimates for where the inner edge of the habitable zone is as there are scientists working on this. There's at least one estimate on the Wikipedia page (https://en.wikipedia.org/wiki/Circum...habitable_zone) saying the inner edge of the zone is at 0.38 AU, which would put Mercury inside it for half its orbit! Admittedly, that one seems to be an outlier, but a blanket statement of "Venus is outside the Solar System's habitable zone" is impossible to make, IMHO.

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    Default Re: Terraforming planets/moons

    Quote Originally Posted by factotum View Post
    16C, actually.There are obviously parts much hotter and colder than that, but if you average the temperatures across the entire surface, that's what you get.
    Ooh, many thanks for that.

    I am strongly in favour of the colonisation of space, and not so strongly in favour of colonising other planets, however I am not altogether against the colonisation of planets.

    I think Venus is a better planet to colonise than Mars mainly because of their gravities. I do not see how Mars could possibly be considered habitable, if Earth's mean temperature is 16 degrees C, that means to me that we are in the cold end of the habitable zone, given that the zone should be ranked from 100 degrees C (too hot) and 0 degrees C (too cold).
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  5. - Top - End - #65
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    Quote Originally Posted by factotum View Post
    16C, actually.There are obviously parts much hotter and colder than that, but if you average the temperatures across the entire surface, that's what you get.

    @Mark Hall: there are as many estimates for where the inner edge of the habitable zone is as there are scientists working on this. There's at least one estimate on the Wikipedia page (https://en.wikipedia.org/wiki/Circum...habitable_zone) saying the inner edge of the zone is at 0.38 AU, which would put Mercury inside it for half its orbit! Admittedly, that one seems to be an outlier, but a blanket statement of "Venus is outside the Solar System's habitable zone" is impossible to make, IMHO.
    Too be fair though, there are plenty of people who DO live in those extreme bands of temp either up or down. I mean greenland can hit -9 C in winter. It wouldnt be easy, far from it, but it would be habitable with the appropriate steps taken. And people adapt to their environment. So as long as it isnt totally hostile to life in a way we cant overcome, we could probably adjust. Now, which is easier for our current tech to deal with, excessive heat? Or excessive cold?
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    Default Re: Terraforming planets/moons

    Quote Originally Posted by Traab View Post
    Too be fair though, there are plenty of people who DO live in those extreme bands of temp either up or down. I mean greenland can hit -9 C in winter.
    But it hits 7C in summer, so the people living there at least get *some* respite from the cold. If the entire planet were subzero all the time, it would be far harder--not to mention that not ever being able to have liquid water on the surface is a big issue.

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    Quote Originally Posted by factotum View Post
    But it hits 7C in summer, so the people living there at least get *some* respite from the cold. If the entire planet were subzero all the time, it would be far harder--not to mention that not ever being able to have liquid water on the surface is a big issue.
    Exactly, the Inuit lived near the pole, but they depended on seals coming up from the sea to breath, if there had been no liquid water they couldn't have lived there.
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    Quote Originally Posted by halfeye View Post
    I don't know what the fuel bill for an Atlantic Crossing by jet aircraft is, but I wouldn't be surprised if it was more than a shuttle launch used to use. Rockets burn a lot of fuel fast, but they don't burn it for very long.
    Er, no.

    Fuel Capacity:
    Boeing Dreamliner: 101,000kg
    Airbus A380: 254,000kg
    Space Shuttle: 2,000,000 kg

    Note that I'm pretty sure the Airbus can go to Australia "the wrong way" from Heathrow on that fuel (somebody used that for their fuel capacity test and I can't imagine another jetliner doing it) and that the Boeing can at least cross the Pacific.

    Welcome to the jurisdiction of our most awful tyrant, the rocket equation (and of course the ~9,000 m/s delta-v needed to get off and stay off this rock). The other side of the coin is that the shuttle has to carry all the oxygen (or oxidizer: half of the fuel is in the solid rockets) it is going to burn. While the "fuel" the shuttle uses (at least after the solid boosters peel off) is extremely light (liquid hydrogen), you still need to bring along plenty of oxygen, and it even outweighs the kerosene in kerosene based rockets.

    And don't neglect our lord tyrant. Increasing the mass of fuel or oxidizer requires more fuel&oxidizer, which in turn requires more fuel&oxidizer. Exponential functions are nasty.

    Maybe if we could build a rocket that didn't require all that oxygen (see NASA's X-43 for the most effective attempt so far), or possibly had a much more energetic fuel per kg (solid mercury sounded like a thing a few years ago, but haven't heard anything since). But otherwise assume that you are going to need enough fuel to send 1000 people around the world 8 times to send 7 people into space (actually I'd assume that you could build a "passenger compartment" in the cargo hold with plenty of people in that 27,500kg mass budget, but nothing like 1000).

  9. - Top - End - #69
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    Default Re: Terraforming planets/moons

    Quote Originally Posted by wumpus View Post
    Er, no.

    Fuel Capacity:
    Boeing Dreamliner: 101,000kg
    Airbus A380: 254,000kg
    Space Shuttle: 2,000,000 kg

    Note that I'm pretty sure the Airbus can go to Australia "the wrong way" from Heathrow on that fuel (somebody used that for their fuel capacity test and I can't imagine another jetliner doing it) and that the Boeing can at least cross the Pacific.

    Welcome to the jurisdiction of our most awful tyrant, the rocket equation (and of course the ~9,000 m/s delta-v needed to get off and stay off this rock). The other side of the coin is that the shuttle has to carry all the oxygen (or oxidizer: half of the fuel is in the solid rockets) it is going to burn. While the "fuel" the shuttle uses (at least after the solid boosters peel off) is extremely light (liquid hydrogen), you still need to bring along plenty of oxygen, and it even outweighs the kerosene in kerosene based rockets.

    And don't neglect our lord tyrant. Increasing the mass of fuel or oxidizer requires more fuel&oxidizer, which in turn requires more fuel&oxidizer. Exponential functions are nasty.

    Maybe if we could build a rocket that didn't require all that oxygen (see NASA's X-43 for the most effective attempt so far), or possibly had a much more energetic fuel per kg (solid mercury sounded like a thing a few years ago, but haven't heard anything since). But otherwise assume that you are going to need enough fuel to send 1000 people around the world 8 times to send 7 people into space (actually I'd assume that you could build a "passenger compartment" in the cargo hold with plenty of people in that 27,500kg mass budget, but nothing like 1000).
    Okay, that still doesn't look that bad to me. There are thousands of planes in flight around the world every day, possibly thousands airbourne at any particular point in time, I really don't think a rocket launch a week is going to make a bigger dent in the world's fuel supplies than all the jets do, and cars probably take more fuel than jets, though electric cars may be cutting that back quite nicely.
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    Default Re: Terraforming planets/moons

    Quote Originally Posted by halfeye View Post
    Okay, that still doesn't look that bad to me. There are thousands of planes in flight around the world every day, possibly thousands airbourne at any particular point in time, I really don't think a rocket launch a week is going to make a bigger dent in the world's fuel supplies than all the jets do, and cars probably take more fuel than jets, though electric cars may be cutting that back quite nicely.
    So what are you comparing? Fuel consumption of one rocket launch versus all aviation fuel usage in a week? Or all gasoline and diesel use worldwide in a week? So is that like comparing the sugar content of a single watermelon to the vitamin c content of all Flinstones Vitamins consumed in a day?

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    Default Re: Terraforming planets/moons

    Quote Originally Posted by halfeye View Post
    Okay, that still doesn't look that bad to me. There are thousands of planes in flight around the world every day, possibly thousands airbourne at any particular point in time, I really don't think a rocket launch a week is going to make a bigger dent in the world's fuel supplies than all the jets do, and cars probably take more fuel than jets, though electric cars may be cutting that back quite nicely.
    A rocket launch a week isn't going to deliver very much material. To state the obvious here - planets are big. Terraforming is thus a huge feat of engineering, and unless there's options involving self replicating organisms/machines on a fairly rapid cycle that means you need a great deal of material.
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    Default Re: Terraforming planets/moons

    Quote Originally Posted by wumpus View Post
    While the "fuel" the shuttle uses (at least after the solid boosters peel off) is extremely light (liquid hydrogen), you still need to bring along plenty of oxygen, and it even outweighs the kerosene in kerosene based rockets.
    Actually, the fuel being very light (e.g. not very dense) is a problem...it means you need much larger fuel tanks to store the hydrogen than you do the oxygen, and bigger tanks are obviously heavier and also require more structure to hold them together. That's why the lower stages of the Saturn V used kerosene/LOX despite this combo being less efficient than LH2/LOX, and why the Shuttle's external fuel tank was so huge.

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    Default Re: Terraforming planets/moons

    And they have a bigger cross-section, so more air resistance.
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    Quote Originally Posted by factotum View Post
    Actually, the fuel being very light (e.g. not very dense) is a problem...it means you need much larger fuel tanks to store the hydrogen than you do the oxygen, and bigger tanks are obviously heavier and also require more structure to hold them together. That's why the lower stages of the Saturn V used kerosene/LOX despite this combo being less efficient than LH2/LOX, and why the Shuttle's external fuel tank was so huge.
    I also think that hydrogen's lack of density also contribute to hydrogen engines lacking the thrust of kerosene (and now methane) engines (you just can't get enough fuel into the combustion chamber). The Shuttle simply can't liftoff on the "main [hydrogen] engines" and needed both solid boosters ignited for liftoff.

    But all those issues go away after one or more stages (see Saturn V). Your upper stages have much less fuel (by mass) than the lower stages, but there is no reason not to use the same cross sectional area (it helps aerodynamics if it remains constant). So you can go into space with all the advantages of light fuel (and using less fuel in the first stage to accelerate a lighter second-third stage). Of course once you have left Earth's orbit, hydrogen tends to either warm up and boiloff (Apollo missions) or simply leak through the fuel tank (presumably a modern Mars mission with zero-boiloff tech), so expect to use some other fuel for such stages (typically a hypergolic).

    Of course SpaceX has a "use only one type of fuel per rocket" policy, which is presumably to reduce launch costs (which are still outrageous, at least with a reused rocket). Even something as important as mass can be less critical than the army of technicians needed to get a rocket on the launchpad and light the candle.

    According to Elon Musk, the fuel needed to launch a falcon 9 rocket (seating capacity: 7) was about $200,000. I can only imagine that only after getting his next generation rocket up and running (with nearly full reuse) will any attempt be made at reducing fuel consumption (Blue Origin has two unbuilt rockets to build before such things as well). About the only ways to really do this with current technology involves doing a lot of acceleration through the atmosphere (lots of heat and drag). The X-43 project showed that they could get to mach 6.8 reasonably well, with a top (barely maintained) speed of around mach 10, of course the drone involved was all engine and no payload, so consider it the barest proofs of concept.

    Other methods involve extreme infrastructure construction to get a small amount of acceleration to the rocket (in case you didn't know, the real job is getting into orbit is getting to ~9,000m/s [20,000mph], getting into space is a small fraction of that) and getting through the atmosphere (although the SCRAMJET listed above needed to go at least mach 4 before working, so perhaps some sort of EM catapult could replace the "0 stage").

    The whole point is that the current generation of rocket companies are just picking up the low hanging fruit of reducing costs to get into space. Lowering the price below $200k/7 astronauts will be an epic undertaking (not that landing a falcon 9 on a barge isn't a great leap in rocketeering).

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    Default Re: Terraforming planets/moons

    A JFK London trip uses about 100kg of fuel per passenger, and has an empty weight of about 200kg per seat. If we assume the 200kg per seat weight in a hypothetical passenger to orbit craft, add 100kg per passenger, and then assume 95% propellant weight, we get about 6tons of propellant per seat. 2/3 of that is oxygen, which means about 2 tons fuel per seat. 10 transatlantic return trips would get you to orbit.

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    Quote Originally Posted by Knaight View Post
    A rocket launch a week isn't going to deliver very much material. To state the obvious here - planets are big. Terraforming is thus a huge feat of engineering, and unless there's options involving self replicating organisms/machines on a fairly rapid cycle that means you need a great deal of material.
    Plus, just in terms of regular commerce (which, in a totally pull-from-the-back-of-my-pants assumption I am going to say would be a bit less that the total tonnage it would take to terraform a planet), the market has already decided that it isn't worth it to stick all that stuff on planes. In particular, stuff like construction materials tend to go on slower, cheaper, and more fuel efficient ships because it's heavy and doesn't need to get there fast, and shipping by air would add substantial costs relative to the manufacturing costs.

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    Quote Originally Posted by gomipile View Post
    That doesn't address the health of organs and body parts that aren't load bearing. Is there a weight training regimen that can be handed to a developing fetus to make it develop the same as it would in 1G?

    (edit: If it turns out that more g force than locally available is necessary for fetal development after future research.)
    Prenatal development is a concern, but it's likely that gravity doesn't play a critical role. Consider that prenatal humans float around in amniotic fluid with no particular orientation until very close to the end of term. Delivery would get very complicated -- both bodies certainly change in response to gravity-driven pressures.

    Digestion and elimination are driven by gravity to an extent, but we seem to manage those well enough in microgravity. Reduced gravity would be far less problematic.

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    Default Re: Terraforming planets/moons

    There have been some experiments with rodents in microgravity, and while the eggs got fertilised just fine, they didn't implant properly in the womb and thus never got as far as becoming foetuses. Even if that were not the case, though, what happens once the baby is born? You can't train a newborn in the appropriate exercise regimen to keep bone structure intact any more than you can the foetus--it would be years before the child was developed enough to do that sort of thing, and I think the bone damage would be far too bad to be recovered at that point. The child might well survive, but it wouldn't ever be able to go down to a planet or even experience moderate acceleration in a rocket.

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    I think terraforming Venus or Mars is way past our current technology level. After all, if we could change circumstances on these planets so drastically, this little problem called 'climate change' could be solved in a snap.

    However, there are other candidates within our solar system that might be better candidates, being the icy moons around Saturn and Jupiter. The moons Enceladus, Europa and Ganymede are all expected to have liquid oceans beneath an icy crust. A liquid ocean means you've already got an area with approximately correct temperatures, so ti might be possible to seed these oceans with hardy species from our own oceans (krill, algae, etc.) to set up an ecosystem that could eventually feed a human base. That seeding might even be completely unnecessary, as live might already exist on these moons.
    Last edited by DeTess; 2019-02-12 at 05:00 PM.
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    Quote Originally Posted by Randuir View Post
    The moons Enceladus, Europa and Ganymede are all expected to have liquid oceans beneath an icy crust. A liquid ocean means you've already got an area with approximately correct temperatures,
    How good is our guess on that? Technically, we don't in fact need temperature in the 0-100 C range to get liquid water.

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    Quote Originally Posted by Xyril View Post
    How good is our guess on that? Technically, we don't in fact need temperature in the 0-100 C range to get liquid water.
    Technically you are correct, but only in the sense that with a lot more pressure it can get a little colder without freezing, and a lot hotter without boiling, lower pressure won't get you anything we can really use. We really are very badly adapted to water at high pressure. Some fish and other sea life can live at the bottom of the seas, but we can't go much below 400ft down.

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    Quote Originally Posted by Xyril View Post
    How good is our guess on that? Technically, we don't in fact need temperature in the 0-100 C range to get liquid water.
    As half-eye said, freezing isn't affected that much by water pressure. Furthermore, 'surface' water pressure at Enceladus is probably not that much higher than here on earth. This is because high water pressure would mean that the features causing Enceladus south-polar plumes would be widening and expanding, and that is most likely not the case.
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    Quote Originally Posted by Traab View Post
    And make it able to survive constant never ending 240+ mph winds. Thats beyond cat 5 hurricanes, heck, it might even be beyond cat 6 if such a category existed.
    I think the term for that would be tornado-force winds
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    Quote Originally Posted by factotum View Post
    There have been some experiments with rodents in microgravity, and while the eggs got fertilised just fine, they didn't implant properly in the womb and thus never got as far as becoming foetuses. Even if that were not the case, though, what happens once the baby is born? You can't train a newborn in the appropriate exercise regimen to keep bone structure intact any more than you can the foetus--it would be years before the child was developed enough to do that sort of thing, and I think the bone damage would be far too bad to be recovered at that point. The child might well survive, but it wouldn't ever be able to go down to a planet or even experience moderate acceleration in a rocket.
    1. Note that microgravity (effective weightlessness) and 0.37G are quite different. Low gravity may be 1/3 of the force found on Earth's surface, but it is magnitudes stronger than microgravity.

    2. Interesting point on bone and muscle development. Note, however, that in low-G environs, assisted walking becomes possible from a much earlier age than standard gravity. Consider how infants have been observed to stand and walk assisted by buoyancy in a laboratory.

    This isn't saying there won't be challenges; just that I suspect these things will pale when compared to the terraforming effort itself.
    Last edited by Leewei; 2019-02-13 at 05:40 PM.

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    Quote Originally Posted by Randuir View Post
    I think terraforming Venus or Mars is way past our current technology level. After all, if we could change circumstances on these planets so drastically, this little problem called 'climate change' could be solved in a snap.
    I don't think terraforming is a particularly technical challenge. It's a resource challenge. Time, money and materials.

    For instance, most scientists agree on what can be done to effects climates (and resolve climate change), but their is not the political will to spend the resources to do it.

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    Quote Originally Posted by LordEntrails View Post
    I don't think terraforming is a particularly technical challenge. It's a resource challenge. Time, money and materials.

    For instance, most scientists agree on what can be done to effects climates (and resolve climate change), but their is not the political will to spend the resources to do it.
    Technically speaking, everything is a resource challenge. You could approximate a computer using only stones and a really, really, really big open field. Thing is, some things are so resource intensive at our current tech level that they might as well be impossible. Also, Both Venus and Mars would need to get a magnetic field somehow, which I reckon is still well beyond 'just throwing enough resources at the problem'.
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    Quote Originally Posted by LordEntrails View Post
    For instance, most scientists agree on what can be done to effects climates (and resolve climate change), but their is not the political will to spend the resources to do it.
    This is exceedingly dubious. We have a decent idea of what reversion to historical conditions look like, because we've tracked historical conditions. Actual carbon capture plans though? There's a lot of slop in there, potential side effects we don't necessarily know about, etc. For instance, seeding the oceans with iron will probably stimulate phytoplankton growth and thus sequester carbon. It'll also have chemical ripple effects and ecological ripple effects, both of which are largely unpredictable. Solar radiation management, the other geoengineering technique, is significantly less predictable - and even what's been predicted is full of side effects we don't want and don't know how to get rid of.

    The stuff we understand that is more a logistics and resources struggle is not-terraforming. The accidental mild terraforming we're currently doing is only semi-predictable, the geoengineering responses which would qualify as terraforming (albeit only barely) are yet worse understood. I'm not saying it isn't a resource challenge, just that there are major technical challenges to be solved to even get to the point where it's just a resource challenge, though of the two the resource challenge is a great deal closer to an impossibility.
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    Quote Originally Posted by Randuir View Post
    As half-eye said, freezing isn't affected that much by water pressure. Furthermore, 'surface' water pressure at Enceladus is probably not that much higher than here on earth. This is because high water pressure would mean that the features causing Enceladus south-polar plumes would be widening and expanding, and that is most likely not the case.
    I was actually thinking more in terms of colligative properties.

  29. - Top - End - #89
    Troll in the Playground
     
    WolfInSheepsClothing

    Join Date
    Feb 2008
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    Italy
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    Default Re: Terraforming planets/moons

    the way to terraform venus would be to throw several large asteroids full of calcium at it; calcium oxide + carbon dioxide becomes calcium carbonate, which is basically a rock. that way, it would be possible to remove its thick atmosphere. without the atmosphere providing greenhouse effect, the planet would cool down enough to be livable, at least near the poles.

    To throw asteroids at it, you'd need some robotic fleet in the asteroid belt. A probe would need to be able to mine an asteroid, dig up its water, turn it into hydrogen and oxygen using solar power, and that would provide the rocket fuel needed to deviate the asteroid over time.

    Lack of magnetic field would only be a problem in hundreds of millions of years. You'd have higher rates of cancer for people living in it, but if a society has the technology to move most of the asteroid belt around (because i'm not sure there is enough calcium in the whole asteroid belt to terraform venus; it's probably close) then they should be able to fix cancer with a few pills.

    So, that's the way to go. impossible with current technology, but potentially doable in a future not too far away.

    Regarding bone and muscle development, we have made significant progress in the latest decades to figure out the molecular regulation mechanisms of the body. As it is, the body is programmed to save energy, so if a muscle is not used often, the body dismantles it. But hacking that molecular mechanism, persuading the body to build muscles regardless of exercice, should be doable. I would not bet either way on seeing it in my lifetime.

    To reach orbit cheaply you'd need a space elevator. My personal vision is this nanotube wire connecting gound to orbit supporting tubes for mag-lev trains, with regenerative braking systems that conver the kinetic energy into electricity while braking. So you spend a lot of energy to get a train up (though you don't need propellant to lift other propellant, so much cheaper than a rocket), but you recover most of that when you need to brake a train going down. You could also mine the asteroids and use the resurces thus gathered as a counterweight to pull other stuff up.
    The problems with this is making a nanotube wire long enough, launching it into orbit (it's going to be big, and you must send it up all at once), and protecting it from asteroids and wheater. Maybe you could build it in orbit directly, but protecting it is still a problem. the space elevator is theoretically feasible, but I'd be really surprised if work on it started in this century.
    In memory of Evisceratus: he dreamed of a better world, but he lacked the class levels to make the dream come true.

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    my take on the highly skilled professional: the specialized expert

  30. - Top - End - #90
    Bugbear in the Playground
    Join Date
    Mar 2007

    Default Re: Terraforming planets/moons

    Quote Originally Posted by Fat Rooster View Post
    A JFK London trip uses about 100kg of fuel per passenger, and has an empty weight of about 200kg per seat. If we assume the 200kg per seat weight in a hypothetical passenger to orbit craft, add 100kg per passenger, and then assume 95% propellant weight, we get about 6tons of propellant per seat. 2/3 of that is oxygen, which means about 2 tons fuel per seat. 10 transatlantic return trips would get you to orbit.
    Blindly plugging that into the rocket equation requires an Isp of 470s (requires a rocket engine more efficient than any known chemical design), but that only shows that SSTO is a dumb idea. It also implies that you are at least at the right order of magnitude for fuel usage (450s is possible).

    Assumption 1: use a shuttle fuel tank for second stage fuel - this gives us a "real world value" for how heavy it is, and also allows the most efficient engine possible, a hydrolox. Assume an Isp of 450s. Assume that 100kg of mass will be needed in the second stage per passenger (and the rest in the first stage). Assume that 6000m/s of 9400m/s will be done by the second stage (actually got 7000m/s, and needed it!).

    wet mass = 760000kg (shuttle tank) + dry mass
    dry mass = 200kg*1000 passengers
    Isp = 450 (SSME in vacuum)
    delta-v = 450*9.8*ln((760,000+250,000)/250,000)
    delta-v = 6917 m/s

    sanity check: dry mass of shuttle tank = 25kg per passenger. Check!

    first stage:
    dry mass = wet mass of first stage + 1000kg*1000 passengers = 1060000kg
    wet mass = 2,070,000kg
    Isp = 330 (Raptor at sea level)
    delta-v = 2323 m/s

    sanity check = wet mass/dry mass ratio (just the first stage) = 11 : this is way too low [falcon 9 is 17], expect to be able to move 10-25kg per passenger up to the second stage...

    total fuel = 760,000+1,010,000=1,770,000kg
    fuel per passenger = 1,800kg (slightly less than two metric tons)

    I'm not at all certain about building a spaceship (second stage) with a human payload to dry weight of 1:1.

    [edit] Sanity check: an Airbus A380 in full "cattle car" configuration can hold ~1000 passengers. Dry mass is 277kg/passenger. No way you are going to get that first stage anywhere close to that, so assume 250-500 passengers or 4-8 tons/passenger.[/edit]

    But perhaps with efficiencies of 1000 passengers it is possible. Everything else checks out. Note that I relied heavily on using hydrogen for efficiency reasons, but methane is a *lot* cheaper than hydrogen (you crack methane to get hydrogen, and crack more because it will leak out before you cram it into your rocket). Of course, expect a lot of oxygen to be used as well. Also I used the Isp for sea level for the first stage, although it won't spend long there at all. Expect the delta-v to climb to 380s, and any additional delta-v (because you moved mass to the first stage) to be about that efficient.

    Note: this calculation relied on "Goslash27"'s "reverse rocket equation" e^[DV/(9.82*Isp)] = Rwd where DV is the delta-V and Rwd is the ratio of wet to dry mass. https://forum.kerbalspaceprogram.com...uot-explained/
    Last edited by wumpus; 2019-02-14 at 01:02 PM. Reason: second sanity check

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