Idobox

That's not the case. The fuel would get critical only inside a reaction chamber, and most of the energy would be released there. To put it simply, nuclear fuel is usually not very radioactive, and doesn't react much by itself. When a fissile atom receives a slow neutron, it sometimes disintegrates, releasing energy, fission products, and a few neutrons, but these released neutrons are too fast to cause other fission events. If you put hydrogen, deuterium, carbon or a few other things in the middle, neutrons bounce off them and slow down, increasing the chances of causing more fission. It's called moderation, it obviously increase the power output, and it's very difficult to do properly because a bunch of things will absorb neutrons instead. When one spontaneous disintegration causes on average more than one other fission, you reach criticality, and you get a lot of power (nuclear bombs or power plants need that). The goal of a properly designed nuclear reactor is to make as much stuff react while in the reactor. Typical nuclear reactors us solid fuel, which means they have to keep the concentration low (to burn slowly) and accumulate waste (which often absorbs neutrons, killing the reaction). A salt-water reactor can use nearly pure fuel (if it can keep it from going critical when stored), can achieve much higher burn rate (less non-fissile junk, waste is ejected) and higher temperature (no need to keep the fuel and its container solid, the whole chamber can be made of graphite). Once the water is out of the chamber, concentration will fall quickly (expanding exhaust), moderation will stop (no graphite to slow the neutrons) and the waste will absorb neutrons. As a result, the reaction will grind to a halt. Of course, the exhaust will be radioactive, which means you can't use it everywhere.

I really love the idea of called it "money" or "moneys" Just imagine the scene, bragging about how you managed to collect over 2000 science with a rocket that costs less than 10 000 money. "I need more money to finish my space station, about 20 000 money actually..."

From wikipedia: That's your extra mass: the neutrino, and some extra binding energy energy (released as kinetic energy in beta decay)

Duh! PRC (people's republic of China) and the underground Nazis are allied. The PRC controls Tibet where the Shangrila gates to the hollow Earth are, and tradesfood and other necessities in exchange for secret alien science. I mean, who do you think is leading the Chinese space program? it's a well known fact that every rocket ever has been built by **** scientists. And the alleged coal seam fires in China? cover up for secret **** underground factories. Oh, and check that : Elvis http://www.peter-janmischke.eu/elvis.jpg Xi Jinping, president of PRC : http://en.wikipedia.org/wiki/File:Xi_Jinping_Sanya2013.jpg Either his clone or his son.

Nonsense. The gravity is obviously lower than on Earth. My guess is that it's shot either on Mars, or inside the Earth (check hollow Earth, it's solid science).

The definition you used is quite commonly accepted, but it's too constrained for my taste. As with intelligence, defining is difficult, and the debate is of limited importance until we find something that might be alien life. It works pretty well on Earth to tell the difference between a rock and a living thing, but might be unable to account for exotic stuff, even on Earth. And I don't think reproduction per see is that important for a definition. Worker bees, mules or freshly detached limbs are pretty much alive, but they don't really reproduce. In Lem's great novel Solaris, there is a planet that is, apparently, a giant organism: that kind of thing wouldn't reproduce. Same thing with respiration/excretion, it just means life needs a form of metabolism, consuming stuff and releasing waste is a way to go, but there might others. And even on Earth, there are a number of things that can live without exactly breathing (by fermenting, for example). And that's what I love with Schrödinger's definition, it doesn't care for particulars. Reproduction is just an example of entropy decrease, and metabolism one of use of energy gradients. The one thing that many people don't like with this definition, especially biologists, is that a bunch of things we don't normally consider alive must then be considered so. We have computer programs that decrease their own entropy by using electricity and computing power, some of them can even reproduce sexually. Companies consumes resources to grow, attack, and sometimes absorb, each other, split, mutate. Memes (in Dawkin's sense, not in wow doge much sense), can arguably fit that definition too, and so do cities, nations, etc...

There are photosynthetic see slugs on Earth, although they need to eat algae to get their chloroplasts first. I don't think photosynthesis is that important. There are a number of other processes for life to get energy, and photosynthesis only makes sense if you have a biome that's not too harsh and has a lot of light. There are different definitions of life. Black_sod's is a relatively conservative one. I prefer Schrödinger's one: a system that can decrease its own entropy by using an energy gradient. It allows for much more exotic stuff to be considered alive, like computer programs, large scale plasma structures, complete planets, etc...

ROI of 4 means you get back 4 times what you invested. But it's true that 10 years is too long an horizon for politicians to invest in it. And that's why we need administrations and stable budgets to handle that kind of stuff.

You don't need something huge, 100 or 200m would allow reasonable gravity at a few RPM. For a station, I would probably build it in two parts or roughly equivalent mass, on on each side. Solar panel tracking might be an issue though. You would have to stop the rotation once in a while, when adding/removing a module, changing the orbit, etc, but it won't be a big deal. And you could probably store that momentum in a flywheel for a few days without too much trouble.

Ring centrifuges have a lot of issues, I much prefer the solution of having the habitat at the end of a cable, and everything else on the other end. This way, you can have very large radius for little weight, no confusing issues with up vs down, less Coriolis effect (slower angular velocity), no problem with the center of mass or bearings, your crew is further away from any nuclear stuff you might have. Now, how come nobody has ever tried attaching a Soyuz (or better, a piece of space station) to some random piece of rocket with a kevlar cable? It can't be that difficult, and if things go sour, you can just release the cable and let the habitat come back home.

OT, but republics aren't democracies per se. Democracy means power to the people, which you might think voting gives. But in practice, a small group of people have all the power, some of them being elected; with you having no way to stop them until they reach their term. Technically, we have a mix of oligarchy, aristocracy and plutocracy. True democracy is almost never used at the scale of a country because it is extremely slow and inefficient, but it is used in many cases for smaller organizations. A proposal to make representative democracy more democratic is to replace elections by random draw, like juries or some position in Athenian democracy. And as I pointed out earlier, the people who devised current systems in the US and France did not consider themselves democrats, didn't want a democracy, and used that term in a pejorative way, a little bit like the word socialism in the US today.

Think of it this way, if your country has a space budget of a few million € a year, even if you team up with a bunch of other small countries, you will have trouble having anything comparable to ESA. But you can make a probe, a satellite, an instrument for the ISS or a rover, and get some bigger agency to launch it. If you look at Curiosity, France participated on ChemCam and SAM, the REMS was provided by Spain with help from Finland, the x-ray spectrometer is from the Canadian space agency, Germany helped with the RAD, and Russia provided the DAN. And I wouldn't be surprised that smaller countries have helped with some small parts here and there too.

Chinese leaders are not elected by the population, they don't need to be popular with the crowds, they don't need to be more popular than somebody else, they just need the support of the party, people who usually have similar ideas and goals. They take decisions depending on what they think is good for the country (or for them), not on what the media and other politicians have convinced the people is good for the country. And because party leaders are usually more difficult to influence, and more rational in their decisions, you end up with much more stable programs. Western democracies are ruled by popularity contests, which results in a lot of wasted energy, and a lot less stability. It also means more versatility, and having the rulers at least pretend to work in our interest. On a side note, I learned recently that both American and French revolutionaries did not want a democracy because they thought the people was too stupid and passionate to rule, and devised systems where a small bunch would have all the power, technically an aristocracy. And they used the word 'democrat' as an insult.

from wikipedia : Pressure influences the LFL, or the LEL. You increase the quantity of stuff to soak up energy at the same rate as the available energy increases, but you also increase the reactivity. If you compress the atmosphere adiabatically, you will increase both temperature and pressure, lowering the LEL. And jet engines usually have such a step. Metallic catalysts are used in mono-propellant rockets, I don't see why it would be so hard to use them in combustion engines.

Hence, you need to build a mine and factory on the moon. The crust contains large amounts of aluminium, iron and silicon. I'm not sure what you need to dope the silicon to make decent solar arrays, but if it's not easy to come by, you might send a few kg of the stuff once in a while. And the main problem with solar arrays on Earth is not price, it's unreliability and lack of good storage solutions. If you convert all your power supply to solar, you better learn how to read in the dark. The basic idea behind spaced based solar is to beam things back through microwave. People will complain that it gives them space cancer, you will need absurdly large antennas on both sides, and there's probably a way to weaponize it.

Thanks for the clearing up on the word fuel. I have trouble conceiving an oxidized state of oxygen, as you would need to strip electrons away from it. Maybe in high temperature environment. About methane, the LEL doesn't mean anything if you don't have air at 1atm with 20% oxygen. There is methane, it is possible to burn it, but not as an open flame at the end of an oxygen hose. I don't feel like doing the math, but you can compress the gas and/or use metallic catalysts to increase the reaction rate. An other option would be to inject a lot of oxygen, which would be terribly wasteful. By the way, the atmosphere contains only 1.4% methane, but is at 1.5atm, so the partial pressure is similar to 2.1% at 1atm.

or Munhole

2001 space Odyssey is extremely realistic. It also very slow and contemplating, and it's a freaking masterpiece. I don't understand why nobody adapts Rama or some other hard-science stuff. Space opera is full of conventions to make it fun, and that's okay. Dogfights and super-slow shiny lasers are to space what orcs, magicians and dragons are to the middle ages, stupidly irrealistic, and so much more fun than the real stuff. What really pisses me off is when they try to make it more realistic, near future, and completely screw up. Gravity is the most recent offender, and made a number of mistakes that are really stupid, and not even needed for the plot. Like when she holds George Clooney's hand and he's "falling" from the ISS, they could just have made them spin, or have him loose pressure, or anything to explain the force. Or when they decided to have the shuttle 50m from ISS repairing Hubble, rather than have the shuttle 50m from ISS because it is doing something related to ISS. You can let Flash Gordon fly on a jetski if you want, but if you have real spacecraft involved, please try to ask somebody who knows how it works.

From memory, the planet is not orbiting, is extremely difficult to access, and they go because they wonder what kind of technology provides the humongous power to keep it from falling. The planet can be seen from very far. I also remember stuff being destroyed by tidal forces pretty close from the planet, but closer to the black hole, including stars, but I 'm not sure of my memories on that point. The planet is held by some form of anti gravity, we have no idea how that works, so there is no reason to believe there are any significant tidal forces within the funnel. But it's also important we're talking of doctor Who, the series that explains the plot using timey-wimey ball of , er, stuff. It's not science-fiction, it's not even future fantasy, it's a glorious acid trip disguised as cheap sci-fi, and pretty much nothing in it is remotely plausible. And that's why it's awesome. So, with our current understanding of physics, no way. With some form of antigravity, why not?

If you find water, you can make LH2/LO2 and sell it to other space operators to refuel once in space. You could also sell moon rocks for novelty. The moon is not protected by either a magnetic field or an atmosphere, and doesn't have wind or a water cycle, so the top soil accumulates particles from solar wind, like He3. That being said, He3 is worthless as a fusion fuel (more difficult to fuse than D-T or even D-D and still produces neutrons) and present in tiny concentrations only. And my favorite concept: mometum exchange tethers. They're long cable cables spinning with stuff attached at each end, and they allow to exchange momentum between two objects, for example accelerating a ship from suborbital to orbital speed by decelerating stuff that is in orbit and throwing it in the atmosphere. You could build a mass driver on the moon and launch bags of dust to a tether in LEO, they would arrive with at least 5km/s of velocity, which means a 10kg bag could boost a 50kg satellite by 1km/s

Nuke, there are places with methane atmosphere, like Titan. Some other oxidizers might fare better than oxygen if you don't care for cost or pollution, but the good ones are usually unstable and thus difficult to store. Lajoswinkler, I've never heard oxygen being called fuel. Isn't that word reserved for the part that is oxidized? The English language doesn't appear to have the words ergol or comburant (according to Firefox's dictionary), so I'm not really sure.

Authorization to build a colony somewhere, probably on some moon or in the Asteroid belt. Stuff to build said colony. It might be cheaper or faster to buy some stuff from us than bring it or manufacture it. Antiques, lolcats and rule 34. Seriously, think of all the stuff western explorers and anthropologists have brought back from other cultures, and how much it is sometimes worth. As said, biodiversity. Of the millions of species around, some are bound to be useful somehow, and it is easier to study and abduct them without these pesky fighter jets and ICBMS trying to attack your advanced ship. Highly specialized workforce. Given we are the only technological species we know, we have no idea how different we are from the norm, and we might well be absurdly good at pottery or macrame without even knowing.

While grammatically correct, the French sentence sounds weird, probably not written by a native speaker. I can understand why they would use Latin or Greek, as they are classic languages. Any idea why they would use French? It's not like they're 17th century European royalty or big fans of Sartre. Given the flag colors, and that the bird is definitely not a bald eagle, my first thought was the French also had weird mission patches. Any chance the US shares information with France, or even has some kind of joint project at Groom Lake?

I've never tried, but do the dishes close if you run out of power? If they don't you will be severely limited in the complexity of the circuits. Also, the batteries are going to act as large parasitic capacitors and slow down everything. I suggest putting lamps or multiple probe cores to drain them faster. Anyway, very cool.

I just discovered SpaceX is recruiting A LOT, and not just rocket specialists. http://www.spacex.com/careers/list It will be significantly easier for US citizens because of various aerospace and defense rules, and I guess a few people here could be interested.