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I'm a Luna-first person. Particularly given the water ice that we've detected. We need propellent depots anyway if we're going to launch the big missions, so why haul all the propellent up a steep gravity well when you can mine it on our moon?
The way I see space settlement being for the next several decades is similar to Antarctica and the high seas. There won't be any permanent colonies (unless Mars turns out to be trivial to proteroform...), but there will be thousands of people on Luna and Mars, and maybe other locations, working at science outposts (as in Antarctica), mining camps (like oil rigs), or hotels (akin to cruise ships). If we're lucky, these will lay the groundwork for homesteads and cities to be built.
Of the two worlds (Mars and Luna), I think Luna has the best near-future profitability, due to it's proximity. It has (some) water and minerals which could be mined. It's a useful place for a science base, for example radio astronomy on the farside, as well as studying the moon itself. It's close enough that tourists could visit. Launch windows aren't the problem they are for Mars. Solar power is far more plentiful at the poles. By focusing on Luna first, we can build up an infrastructure that will make it easier to get science bases going on Mars, as well as support the exploration and exploitation of near earth asteroids.
My thoughts exactly, Terraformer. I think Musk's plans for a Martian city are premature and highly problematic. A lot of people are caught up in the excitement of the prospect, without seeing it for what it really is.
It will cost at the very least $1000/kg to ship anything to the Martian surface and an equivalent amount of money to export anything back to Earth. That is the mother of all tariff walls. It effectively cuts the colonists off from all of the luxuries and manufactured goods that we enjoy here on Earth, unless they can make them for themselves. People paying up to a million dollars for a ticket, will find themselves living a meagre existence as troglodytes in cold, dark tunnels that they cannot escape from. Growing enough food is going to be tough. Living standards will be basic for a long time. Maybe it could be made to work at some level, but the novelty will wear off very quickly when the colonists realise that their brave new world is Antarctica without air, where not a single living thing can survive without an artificial environment. Depression and suicide are going to be big problems. Not somewhere I would want to take my family.
I think a moon base is more valuable because it is more than just an end in itself. It can export materials to Earth orbit, where space manufacturing and real colonisation can begin. The big advantage in my mind is that orbital industries can export products to buyers on Earth, whether they are space hotels, solar power satellites or even manufactured goods to Earth surface, in a way that a Martian colony would find much more difficult. This means that colonists on the moon and in high Earth orbit can afford to pay for the things that they need to import. The inability of a Mars colony to do this is what will ultimately kill the Musk dream.
The BFR will be an interplanetary liner - it's huge, capable of carrying 150 tonnes.
It is small by the standards of Earth transportation – capable of ferrying a hundred or so passengers to Mars and making a round trip every 2.5 years. If its lifespan is 30 years that means that each rocket can carry out a dozen or so round trips in the course of its life – maybe 1200 passengers in each direction. On that basis, it will be difficult for the cost of a ticket to drop to much less than $1million, even if economy of scale is maxed out. The same rocket could transport 78,000 passengers to the moon over the course of its life. This suggests to me that the economics of lunar transportation will be much more favorable to a private investor trying to finance the cost of the ticket.
There are other advantages as well. A rocket making short-term trips does not need the sort of life support capabilities that an interplanetary vehicle would need. It will be cheaper to build and could presumably carry more passengers per trip.
Building a space manufacturing infrastructure on the Moon (as opposed to Mars) will be extremely difficult. Mars has a wide range of resources - all have to do is ship out the initial start-up machinery to get things going there.
It will be difficult to build space manufacturing anywhere. But it will be much cheaper to ship infrastructure to the moon as opposed to Mars, for the reasons already discussed. From what we know, the moon has a harsher environment with less accessible resources. But it is much easier to transport those resources from the surface into high Earth orbit, where there are markets for things like solar power satellites and space hotels. And of course there is then the potential to build truly interplanetary ships, weighing thousands of tons and driven by mass drivers and transporting thousands of people at a time to places like Mars, Ceres and the Asteroids. That sort of capability would really open the solar system to human colonization.
The big future for the moon is lunar tourism which will then help fund Mars settlement.
I don't think lunar tourism will ever be a very big market. The place is like an Earth desert without air. There will be a few people prepared to pay a million dollars to do it for the sheer novelty value. But most people spending that sort of money will need to see financial return. Low Earth orbit has better potential for tourism. If the BFR could make round trips to low Earth orbit in a timescale of hours, it's economics would be more like those of a jet aircraft, with costs <$100/kg. At that price, low orbit tourism will be achievable as a once in a lifetime holiday for quite a lot of people, but they will want to do exciting things when they get there. They will want spacious hotels, all-inclusive dining, zero-G swimming pools, etc. To build the sort of infrastructure needed to make this workable will take tens of thousands of tons of materials. Even with the BFR, you could not realistically launch it from Earth.
A round trip to Mars would take over two years. A round trip to the moon could be done in two weeks. The same vehicle could make a hundred trips to the moon in the time it takes for a single Martian round trip. It would be much more sensible at this stage to concentrate resources on a lunar base and build up economy of scale on the launch and transfer vehicles. What's more, a lunar base would be a valuable asset for supporting space manufacturing. With those capabilities, we could build ships capable of shipping thousands of people to the red planet. Accessing Mars will not be possible for ordinary people until we have interplanetary liners.
The visual for the first city on Mars (wonder what the name will be?) looks v surface/dome orientated. Has Musk's team already been doing research on this do you think?
https://www.engadget.com/2017/09/29/spacex-mars-bfr/
Are they thinking in terms of water as a radiation barrier? Or have they got something up their sleeve, like a local electro-magnetic barrier. I would expect there to be more regolith barrier.
But perhaps it's just an "artist's impression" and shouldn't be taken too seriously at this stage.
I am guessing that this picture was produced for publicity purposes. On a planet where background radiation is 15 rem per year, average temperature is -60C and air pressure is 1% of Earth's, it would be crazy not to build inhabited structures underground. Solar panels, greenhouses and airlocks are exceptions of course.
If he can transport people from one side of the world to the other for a cost of say $50/kg, the cost of a ticket would be $5000. There could be a limited market for that - kind of like super-Concorde.
Safety would be an obvious concern. I doubt people will be prepared to risk their lives on routine rocket travel if is more than a factor 10 more risky than a plane flight. That means no more than a 1 in 100,000 chance of fatal crash.
Antius:
I cannot speak as to what you wrote, as I am totally in the dark about that. But I hope things change for the better for you and your fellow Britons. It does not sound good.
They have already passed laws that require internet service providers to keep records of everything their customers do online. I expect an outright ban on VPNs will not be far behind. Right now, they are attempting to force internet companies to provide loopholes and back doors in internet encryption, so that there is no place that can be secret from them.
None of this seems to ring any alarm bells in the minds the UK public. The worst thing about all of this is just how few people are prepared to stand up and say how absolutely crazy and sinister it is. The media pretend it isn't happening. Only a small minority of people seem to care about it at all. I am shocked by how complacent people are and how easily they are enslaved. Where the hell is the modern day equivalent of Thomas Paine?
"As for nuke penetrators, I hope we have them. But I doubt that we do. An item being developed is NOT an operational weapon."
When one uses such devices, it is greatly advantageous to make it look like an accident.
Wait until North Korea launches a ballistic missile and then target the facility with a cruise missile armed with a low-yield nuclear warhead during launch, preferably from a submerged hunter-killer submarine off the coast. That way, it looks like an operational nuclear missile test that went wrong.
Even the most oppressive dictator will struggle to maintain support for a programme after a nuclear 'accident' like that.
What the British government did today should confirm to anyone that the British government is not a democratic organisation. It is not so different in it’s use of arbitrary power as the likes of the Chinese government.
http://www.telegraph.co.uk/news/2017/09 … rror-laws/
Whatever one thinks of the politics of Scottish Dawn, they are a political protest organisation. To my knowledge, they do not carry out assassinations or plant bombs. That didn’t deter the British government from banning them as a terrorist organisation. As such, anyone found to be a member or promoting or associating with them in any way, faces a long prison sentence.
The Home Secretary Amber Rudd gave the following reasons for banning the organisation:
‘National Action is a vile racist, homophobic and anti-Semitic group which glorifies violence and stirs up hatred while promoting their poisonous ideology, and I will not allow them to masquerade under different names.
“By extending the proscription of National Action, we are halting the spread of a poisonous ideology and stopping its membership from growing – protecting those who could be at risk of radicalisation.’
In other words, they were banned and criminalised not because of anything they did, but because the UK’s despotic Home Secretary doesn’t like their ideology, and in her typical oafish way, decided to crush something she didn’t agree with, probably without even understanding the significance of what she was doing.
This effectively makes the UK a totalitarian state. We still go through the motions of having elections. But political parties are not free to present radically different policies to those of the powers that be. If you don’t bow down to the ideals of cultural Marxism, then you are a terrorist and a criminal. People are not free to express opinions – if your opinion is offensive to anyone, you can be arrested and charged with inciting hatred in Britain. One has to wonder what the point of elections actually is under conditions like this.
The same Home Secretary recently brought into power a bill that allows the UK police, MI5 and other government agencies, unlimited access to the online activities and phone calls of any individual. From now on, anything you say, write, search for, or read can be intercepted and used against you.
According to the Sun newspaper, here are some of the activities the British government will imprison you for:
‘Being a member of, or inviting support for a banned terror organisation is a criminal offence carrying a sentence of up to 10 years in prison.
Arranging or assisting in arrange a meeting of a banned group or speaking to a meeting can also be punished with a decade long prison term.
Wearing clothing or carrying something that arouses suspicion you are a member or supporter of a banned group is punishable by six months inside or a fine of up to £5,000.
Any group can be banned by the Home Secretary if she believes it is concerned in terrorism.
This includes committing a terrorist act, preparing a terrorist act, encouraging terrorism, or being otherwise concerned in terrorism.’
https://www.thesun.co.uk/news/4569388/b … awn-ns131/
Apparently, you can now go to prison for wearing the wrong clothing, failing to avert suspicion that you aren’t a member of a group the government doesn’t agree with; wearing the wrong symbols; arranging a meeting for people they don’t like; even talking to a group of them.
This sort of corruption goes far beyond Orwell’s most Dystopian fantasy. The sort of nightmares he dreamed of are now real life. The greatest enemy of any thinking Briton, is his own government. How can these people presume to lecture the likes of North Korea when their own policies are based on such complete oppression of their own people?
Cosmic rays are an issue on Mars. They hit the upper atmosphere producing a shower of secondary particles, much as they do on Earth. The Martian atmosphere has only 1.6% of the column density of Earth's atmosphere, so most of those particles reach the ground. On the plus side, they individually have less energy than the original cosmic ray. So the magnetic field need not be as strong as it would need to be in free space.
Director of the NSA, Admiral Mike Rogers, has admitted in a private town-hall-style meeting of NSA staffing that Donald Trump did, in fact, collude with the Russians. Months ago it was reported that there was a FISA surveillance warrant on Carter Page, dating back to at least the summer of 2016, which would have been right in the middle of the time he worked for the Donald Trump campaign.
The surveillance on Carter Page actually goes back much further than originally thought. It goes all the way back to 2014. This means that every word of Page’s remote communications with Donald Trump and the campaign have likely been recorded.
Who cares. What does collude mean anyway? The Democrats receive campaign contributions from the pro-Israel lobby, Saudi Arabia, China, to name just a few. I would fully expect Trump to have conversations with the Russians. It is not an insensible thing for an aspiring president to do. Wouldn't it be great to actually find a way of getting along with these people? The fuss and paranoia generated by the US media over 'Trump and the Russians' is absurd. The Washington Post and New York Times are Zionist rags pushing their own interests and a lot of people are either too ignorant or too stupid to see through it.
The boiling potassium reactor, equipped with MHD generator was estimated to able to achieve P/W of 1kW/kg. But it wouldn't be an easy technology to develop.
The low thrust of the EM drive might not be such a problem for some mission scenarios. If we ever do get round to establishing space manufacturing in High Earth orbit, it would be very useful to have a tug that can ferry bulk materials like methane, food, water and heavy equipment from LEO to L5. If the EM drive can achieve a round trip time of a few weeks, it would be perfectly acceptable, especially if the drive system was essentially maintenance free and could operate for decades with no requirement for intervention.
Another application is interstellar flight. If it is going to take a century of more to get to the nearest star anyway, then the low acceleration of the vehicle is not an issue, especially if some other means can be used to boost it to solar system escape. At a constant acceleration of 0.01m/s2, a vehicle could reach a-centauri in about sixty years. That's as good as any theorised fusion drive.
I still can't get my head around a device that would seem to be a perpetual motion machine. As velocity increases, the kinetic energy of the vehicle would exceed the total energy expended to accelerate it, assuming thrust remains constant. That would seem to violate the most basic law of physics. The other explanations are: (1) It doesn't work; (2) Acceleration declines as speed increases, maintaining conservation of energy; (3) Energy is being drawn from a source that we do not yet understand, i.e. the quantum vacuum.
This is a variant on Robert Zubrin's salt water rocket. The salt water rocket itself is unlikely to work (at least with 235U), because the fission cross-section and reproduction factor of 235U rapidly declines as neutron energy increases away from the thermal region. This means the salt water rocket would reach criticality, there would be a low energy pulse and most of the propellant would leave the nozzle without even reaching boiling point. See here:
http://wwwndc.jaea.go.jp/Reproduction_F … 235_0K.jpg
One way of avoiding this is to start criticality with a hard neutron spectrum - say in the KeV range. As temperature increases, the reproduction factor will increase and the reactivity will increase along with it. A good candidate fuel would be Uranium Tetrachloride, which is molten at temperatures above 590C. The high atomic weight of chlorine limits any neutron spectrum softening and the moderate melting point means that the engine chamber and fuel handling apparatus can be made from stainless steels.
An interesting option would be to add small amounts of deuterium and tritium to the engine whilst in operation. This would undergo fusion, releasing superfast neutrons, which would boost reactivity, potentially allowing for reduced critical mass.
There is insufficient water in the atmosphere of Venus to sustain an algal population. Also, plants need minerals to grow.
The Democrats are funded by Saudi Wahabi's that want Islam to conquer the Western world. They also receive money from Israel.
Why should we honestly care if the Republicans received some funds from Russia. They are arseholes, but so are the Saudis. There has been scant evidence of Russian collusion in the US election so far. But if it did happen, why would it be unacceptable and Saudi collusion acceptable? Or is it just that the Republicans are the 'wrong sort of people'?
Venus closely resembles a biblical description of hell. If its temperature and atmospheric pressure are reduced through use of a sun shield, colonisation may be possible. But would it ever be desirable? The planet has very little hydrogen. It also has a deep gravity well, that makes escape impossible. A terraformed Venus would be a dry Vulcan. Mars does not have these problems.
High CO2 also screws around with blood acidity levels in humans. After a few days exposure, bone demineralisation starts to occur - people basically pee out their bones. You need a hammer and chisel to remove the resulting limescale from the heads. Put people in a high CO2 environment for years at a time, and they will develop osteoporosis and arthritis by the time they hit their 40s.
Have I correctly understood what Musk has said here?
Without propulsive landings there will be no Mars landings. Unless the lander weighs considerably less than 1 tonne, which isn't practical for any manned landing.
I will believe it when I see it:
https://www.nextbigfuture.com/2017/05/l … plans.html
Even if it works, fusion is unlikely to be economic here on Earth. Power density would be about an order of magnitude lower than a PWR. The device is basically a shell of rare Earth superconducting magnets. Most of the energy comes out as fast neutrons, which irradiate the reactor walls, superconductors and everything else, requiring that the whole thing be stripped down by robots every 18 months. To generate fresh fuel, cooling must be accomplished using a liquid lithium blanket. Radioactive tritium must then be chemically separated from the molten lithium. Does this sound like a device that will ever provide cheap and abundant energy?
Cities on Earth have almost exclusively grown organically. They start as small settlements on rivers, roads or coasts and infrastructure is gradually added, often on top of old infrastructure as population grows. Utopian visions of planned cities make good pictures to hang on walls, but tend not to get built in real life. Think of all the utopian futurism of the first half of the 20th century. How much of it ever got built? Much of it looks bizarre and quaint now.
The reality of a future Mars city will be lots of small pressurised structures and domes, lots of small and individually financed projects coming together to form a city scape.
I wonder if phobos is a source of dangerous debris? A single impact on the surface of the moon would generate many times its own weight in debris, most of which would exceed the moon's escape velocity. Admittedly, the moon's gravity would also hoover up any debris generated by impacts.
There would appear to be no easy solution to debris cluttering Earth's orbit. The larger pieces can be intercepted and their orbits altered to intersect Earth's upper atmosphere. It is the smaller bits that are problematic. Maybe laser beams can be used to alter the orbits of small debris?
About a year ago, I attended a lecture given by a senior astronomer on the subject of exoplanets. He seemed to think that the preponderance of super-Earths in close orbits was more an artefact of our detection methods, not a representation of genuine abundance. Time will tell.
But I think your point is basically correct. If the Earth were much more massive than it is, it would be very difficult to reach orbit without nuclear pulse propulsion. If a substantial portion of planets are super-Earths, then that would appear to be another constant in the Drake equation.
What we have learned about bacterial life suggests that it is both hardy and adaptable and capable of arising in many environments in our own solar system. But complex multicellular life requires a far narrower set of conditions to survive and didn't emerge on Earth until late in its existence. It is easy to see that a complex civilisation requires an even more favourable set of conditions, stable over long periods, in order to arise. Long shot: Life is everywhere, but complex and intelligent life with advanced technology is rare indeed.
I spent a little time looking into the Nuclear Salt Water Rocket proposed by Robert Zubrin. I believe that the concept (as it stands) is unlikely to be workable.
The reason is that neutron reproduction factor and reactivity in a moderated mixture tends to decline with increasing temperature. Take a look at the graphs for neutron reproduction factor.
http://dspace.mit.edu/bitstream/handle/ … ture06.pdf
The mixture would be injected cold (when reactivity is greatest and average neutron energy is 0.025eV) and as it heats up (and average neutron energy increases), the reaction would tend to dampen as reproduction factor declines.
Notice however that in the fast neutron region (>1KeV), the reproduction factor increases with increasing neutron energy (i.e. temperature). This suggests that Zubrin's rocket would work well for all fissile fuels at high neutron energies. This suggests that the rocket would work best if the fuel was injected as pure molten uranium or plutonium chloride, with no water present. Any hydrogen injected with a temperature lower than 10million K (1KeV) will tend to dampen the reaction.
Kbd512, Zubrin's nuclear salt water rocket would seem to represent the best of all worlds. No one in official NASA circles appears to take it seriously. To my knowledge, it has never been subjected to serious modelling. Yet it would appear to allow unlimited access to the solar system within timescales of weeks or months. What is your opinion on its plausibility?
I have been working on a lower performance concept for a nuclear thermal engine that uses natural uranium as fuel. Whilst this is much more bulky than NERVA, it could be constructed on Mars using local materials. The engine is only really workable in space, as it's T/W ratio is too low to achieve take-off from a planetary body. However, T/W would be substantially greater than any electric propulsion system and ISP would be 800-1000. It should therefore be possible for a freight carrying vessel to traverse from low Mars orbit to high Earth Orbit and back again with a single tank of hydrogen propellant.
There are two ways that the engine could be built. The most technically easy option for a mars colony would be a pebble bed reactor with natural uranium carbide slugs embedded within graphite spheres. However, the low moderating power of carbon would result in an excessively large core. The second option would be a hybrid, hydrogen cooled, heavy water moderated core. This would have higher power density, but requires a more complex design. Uranium carbide fuel must be housed in graphite sleeves within magnesium alloy tubes running through a tank of D2O. The graphite is in place to insulate the D2O from the hot hydrogen gas used to cool the fuel. Because the moderator remains cool, the neutrons remain fully thermalised even as the uranium reaches temperatures of >2000C.
An obvious problem with a hydrogen cooled, deuterium moderated rocket is that the propellant has a 641x higher neutron absorption cross-section than the moderator. This could both dampen the reaction and could make core physics unstable. However, the propellant atom density at 10bar and 2500K is still 1000 times lower than that of the moderator. Also, because phase-change does not occur in the propellant, any power transients will be relatively slow and should be dampened by the Doppler effect and active control systems.
Because the burn-up of natural uranium is limited to ~500GJ/kg, the fuel must be replaced after about 2 round trips. This would presumably be carried out in Mars orbit at the same time as hydrogen propellant refilling.
The purpose of the core would be to power large volume freight transport (1000s of tonnes) between Earth and Mars orbits. Freight must travel in both directions cheaply, because beyond a certain point, a Mars colony must be capable of paying for its imports using exports.
The only reasonable justification for returning to the moon that I can foresee is to provide materials for space manufacturing, things like solar power satellites, which I know you are sceptical about. In that case, the station needs to be at L5, not L1. The moon is just too poor in resources to be interesting in any other way.
What is clearly needed for interplanetary transport is a solar/nuclear-electric propulsion system. It makes no sense using Musk's ITS upper stage as an interplanetary transport. It ruins the economics of the launcher due to the 2.5 years that it takes to get to Mars and back. To get aeroplane economics on these launchers they need to be turned around quickly and as you say, a spacecraft must be designed for the task at hand, otherwise it is non-optimised and wastes payload and money. The need for tanker launches into Earth orbit makes the economics even worse.
If an electric transport vehicle is used as part of a Mars transport infrastructure, then regolith from Deimos could be used as reaction mass in a VASIMR engine. The vessel would stop there on the way in to gather propellant for the trip to low Mars orbit and back. It would stop again on the way out for propellant to take it to low Earth orbit and back. That requires a delta-v exceeding 12km/s, not including gravity losses and assuming constant payload.
The economic performance of the vehicle improves as trip time goes down. We want as many trips within a reasonable economic return window as possible (20 years?). That keeps space radiation hazards as low as practicable as well. This requires both high thrust and high delta-v, in other words lots of power to weight. Some space nuclear reactors are on the drawing board with estimated power density of 1KWe/kg. These are either gas or liquid metal cooled reactors coupled directly to an MHD generator. The problem is that no one is seriously developing them beyond concept stage. Something with power density that high is dangerous and hugely expensive to develop. Coupled to a VASIMR with an ISP of 5000, these could achieve accelerations of 0.01m/s2 and could accelerate from LEO to Earth escape in about 4 days, with a total delta-v of over 30km/s with a mass ratio of 2. It is very difficult to achieve that performance using solar power.
Electric propulsion is needed for another reason that is often overlooked. It is not enough for a Mars colony to be able to import goods cheaply from Earth. It needs to be able to export goods to Earth to pay for its imports. This requires that the cost of export is sufficiently low for high value-to-weight manufactured goods to be able to compete on the Earth markets. So the launch vehicle on Mars must also be capable of achieving good transport economics to and from Mars orbit. It cannot be used to fly back to Earth. Ideally, we would want to run both Earth and Mars launchers continuously, accumulating and retrieving payload in their respective orbits. The electric transport vehicle would be scaled up to transport hundreds if not thousands of tonnes of payload per trip between the planets. That way it achieves economy of size and the launchers achieve economy of volume.
