Wednesday, July 19, 2017



Kuiper Belt Navigation and Mining.

 

How might we steer objects from the Kuiper belt to achieve objectives in the inner orbits of the solar system? This question arose from my proposal to alter the rotation of the planet Venus for purposes of exploitation and habitation. That proposal is discussed in the article "Small Fetters" in which I express doubt that humanity has the right stuff to achieve any such objective. http://fullduplexjonrichfield.blogspot.co.za/2013/12/small-fetters.html

Some critics denied that it could be practicable to achieve anything of the kind as a realistic engineering project at all, even in principle. Some simply said that the scale of the project was too large ever to be done in principle. Some said that it could not be worth doing even if it were possible. Some of the more open-minded suggested that, assuming it were done when 'tis done, then 'twere well I should explain how it were to be done and why.

In a thread I pointed out that Kuiper Belt objects, that authorities assume to number in their millions — some estimates suggest billions, should bear kinetic energy more than adequate for practical exploitation. I did not at that time bother to discuss the detailed engineering, taking it for granted that navigating rocks from trans-Pluto orbit to intercept Venus suitably was not intellectually challenging in principle, however challenging the project might appear from political or engineering perspectives.

However, contrary to my expectations, some participants in the thread impugned this, and since some aspects of the topic are of intrinsic interest, I here discuss approaches to obtaining and navigating comets, asteroids, and assorted Kuiper Belt meteorites as required.

I still skirt currently irrelevant engineering issues of course.

Several other ideas and approaches might prove relevant, but here I concentrate on projects such as the engineering of Venus and Mercury and assume that the scale of the project would involve something of the order of 100,000 Kuiper Belt objects of perhaps 10 km diameter on average. Please do not bother to point out that not all Kuiper Belt objects of that order of magnitude are spherical; this is strictly a spherical cow exercise.

Obviously there are many types of approach to such potential projects, and in this discussion I ignore all that are not aimed at a long-term commitment (probably 1000 years or more, possibly even several thousand years; gaining a new planet with all its resources would be worth a good deal more than that in any rational scheme of things). The discussion also has nothing to do with steering any single object, of either gigantic or trivial size, nor bringing it to some sort of relative stop or storage trajectory at some arbitrary position in space. Instead I consider perhaps tens to hundreds of thousands of objects of worthwhile size, small enough to steer economically, and large enough to achieve particular objectives.

Nothing of the kind would be worth discussion without an appropriate infrastructure, but at such a distant remove, details of that infrastructure are hardly worth discussion. Anyone who doubts this should read Arthur C. Clarke's original proposal for communications satellites; he proposed that they should be manned! His proposal was in no way stupid; in fact, given our current applications of communications satellites, if they really had to be manned, they still would have been worth it; it is just our luck that our advances in technology since World War II free us from any requirement for such an extravagance. Similarly, it is practically certain that anything I propose here would seem ludicrous to engineers of the 22nd century.

Instead I merely brush over some plausible requirements of such an infrastructure in discussing principles.

Thousand-Year Projects

 

It is well not to be too casual about beginning a highly technological 1000-year project. I suggest that for reasons of navigation and communication we should start by installing at the very least a few hundred permanent unmanned satellites in strategic orbits in the solar system. That no such project has yet been undertaken is a blot on our record already. However, the solar system equivalent of a GPS system plus communication relay system plus near space (meaning solar system in this context) astronomic and cosmological observation system, would be necessary as the first step in the project. Call such craft the Relay Satellites.

Relay Satellite Infrastructure

 

We should be able to install a profitable, workable and worthwhile foundation within a few decades, but the planned lifetime of the Relay Satellite system would be measured in millennia rather than years and there would be no question of committing to naive uniformity of design during such a period. That infrastructure would be an indefinite project, adapting to our needs and technologies for the foreseeable future. In practice of course, certain apparently arbitrary standards might remain constant, but such are merely practical details that are not immediately relevant to us. The principle is well understood and tolerated and there is a fair discussion of a traditional example at: http://www.snopes.com/history/american/gauge.asp

'Nuff said on that point.

As I see it the Relay Satellites should have modest navigational capabilities, just about enough for maintaining station and attitude in their appropriate trajectories indefinitely. Some of them in near solar orbit might use solar power of one sort or another, but by far the majority would occupy orbits beyond Mars, and some perhaps beyond Pluto. Whether to power them with beamed energy, isotope energy, or on-board fission or fusion power generators is an example of a question I leave to future generations. They should need considerable power for communication at least, plus very sensitive reception equipment, because they would be communicating partly with tiny craft that could not carry giant antennae to capture faint signals. Whether there would be relatively few multifunction satellites or relatively many specialist function satellites, and whether a satellite that outlives its fuel supply would be parked and catalogued, or scrapped, refurbished, recycled, or destroyed, I also leave to future interests. Personally I like the idea of large-scale, modular satellites to be serviced and upgraded by specialist unmanned craft, but I do not insist upon that.

Note that there is no suggestion that such a fleet of Relay Satellites should be dedicated to the Kuiper Belt object navigation project. There would be plenty of function for it without that. It is quite possible that a Kuiper Belt initiative would affect the scale and details of parts of the fleet, but that is not especially relevant here.

Prospecting Craft

 

The second class of craft, prospecting craft, would in contrast be specialised for ranges of function dealing with exploration and prospecting in the Kuiper belt. To this end they would be capable of extremely long range, long-term navigation beyond the orbit of Pluto. Their communication and navigation capabilities would be powerful, but specialised for their role. They would rely on the permanent Relay Satellites for most of such functions, and partly for keeping track of the prospecting craft. Of course, each satellite would have its own intelligence and a very large memory, probably petabytes rather than terabytes, enough not only to manage the data that it accumulates, but the parameters of the infrastructural system. They would have sufficient intelligence for routine tasks, including some fairly complex ones, because apart from the question of how far robotics would have advanced in the next century or two, such tasks would be, if not highly stereotyped, at least confined to a small universe of discourse. They also would have great redundancy of function and capacity to ensure resilience in the face of predictable radiation and unpredictable accident. None of your single-drive hard disks and the like!

Prospecting craft would be exceptional in the amount of reaction mass and energy that they would have to carry, because they not only would have to reach the Kuiper Belt, but would have to do considerable amounts of unpredictable navigation within it. At such a distance from the sun, solar power would be practically worthless, probably including solar wind power. It also would not be practical for such craft to rely on isotopic thermal energy; they would need fission power generators at least, which is the good news; the bad news is that they also would need large amounts of reaction mass, even if they used ion thrusters. Much as they would rely on the relay satellites for control and communication, they might have to rely on rendezvous with tugs and maintenance vehicles for refuelling and upgrading.

Their function would be to locate and characterise as many Kuiper Belt bodies as possible, determining their nature, mass, trajectories and the like by any practical means, whether optical, radar, infrared, gravitational, theoretical or generic, to name but four... err... or so... Bodies that either pose a threat to the inner solar system, or that seem to be potentially valuable to the main project, probably would be visited physically to obtain all relevant information. For example, bodies that are rich in ice or ammonia might either be particularly valuable or not usable for the purposes of the project. Similarly, bodies that amount to aggregations of gravel might be valuable if their trajectories were particularly suitable for gentle manoeuvring, but hopelessly dangerous to use otherwise unless they could be cemented, say by combination with an iceberg or ammonia-berg.

This is a large subject, not worth exploring at this point in any depth. Suffice to say, some such functional craft would be needed to locate and evaluate the objects to be selected for navigation in the project.

Tugs and Maintenance Craft

 

The third class of craft would be the tugs and maintenance craft. They would be a job lot, and I do not discuss their design, which would be variable at all stages of the project. All the other craft would require updating, modification, refuelling, repair, and possibly even retrieval. The Relay Satellites might well require being transported to their stations as well. No one tug or maintenance craft would be suitable for all such functions. However, each one probably would be versatile and each one would have powerful thrusters of appropriate kinds. However, they might need less fuel than the prospectors, because they would have shorter missions, and more closely defined.

Rockrider Craft

 

How many different classes of craft would be needed, I cannot say; the only other one worth discussing here would be the Kuiper Belt object navigation craft. Let’s call it the Rockrider craft. It is the one at the cutting edge, or the coalface if you prefer. It's job would be to rendezvous with a selected object, prepare it for transport, and steer it to the objective.

What possibly, just possibly, could be simpler?

A lot of things of course, but not many are as worthwhile.

Manned and Unmanned Craft in Such Projects

 

Very well. Notice that I have said practically nothing so far about manned craft. I do not say there would be none such, but for the purposes so far discussed, I cannot see any being required, and frankly I cannot in the short term see any manned craft being practical for transient applications beyond say, the orbit of Mars. We are after all speaking of Rockrider craft undertaking voyages of decades at least, and commonly of centuries. Even if we condemned convicts to such voyages, it is hard to imagine what we would want them to do out there in space, even if we could trust them there. I leave such distasteful speculations to those with the appropriate distastes.

Target Objects and Objectives

 

Now, each Rockrider craft would have the task of rendezvous with a nominated object that had been identified, located, and characterised by the prospector craft. Apart from a few prototypes, probably none would be launched before some thousands of target bodies had been selected as having suitable masses, constitutions, neighbours, and trajectories for the project. Many, possibly the majority of such Kuiper Belt objects, might be perfect for launching in a few hundred thousand years, but useless for short-term projects of 1000 years or so. However, there are assumed to be many millions of bodies out there, so I do not feel too defensive about assuming that we would be spoilt for choice of suitable objects.

A suitable object would have to be one that could profitably be adjusted in its attitude and trajectory, for a Rockrider craft to manipulate and navigate it down from say 40 astronomic units, to rendezvous as required with Venus or Mercury at less than 1 AU. For example, if an otherwise suitable 100 gigatonne object were spinning at a rate of several hertz, the very task of de-spinning it strikes me as discouraging; I would rather go on to look for something friendlier. Nor would we be interested in 10-tonne or peta-tonne objects, or at least that is what I assume.  Again, we would prefer to deal with objects whose orbit we could adjust most economically in terms of energy and time. Exactly which variables would be most important in a given case, I do not much speculate upon.

I suspect that very circular orbits would be expensive to adjust, whereas elliptical orbits that approach, or could be coaxed near to Neptune, could be adjusted drastically at modest cost. Difficult decisions would be the business of the human orbital engineers, but generally most decisions could be handled programmatically. Possibly one could use nuclear explosions for crude preliminary adjustment of some kinds of orbits of suitable bodies, or even to persuade some bodies to collide usefully.

Using collisions might seem a bit optimistic, given that even millions of bodies so far out would have a considerable mean separation, but it’s just an example of the kind of consideration that might arise.

The point in general is that we would select bodies with orbits that could be adjusted with minimal investment of energy and material, whether by bombs or by thrust.

However, we could afford a reasonable investment, bearing in mind that a typical energetic profit for dropping from say 40 AU to the orbit of Venus would be about sixty-fold, and to Mercury, 100-fold. Those already are attractive figures. And if we could gain useful momentum by slingshotting past the major planets, we could increase that profit dramatically.

Slingshotting would be important for more than just the increased yield of energy; it would be vital for steering large bodies. Any adjustment of the trajectory of a billion- to trillion-tonne mass would be so expensive that we would care less about the factor of profit, than whether we could afford the project at all. As a result we might well be happy to work at a trajectory for a few centuries to get a finally profitable result by nibbling at the gravitational field of one planet after another. The computing load would be heavy, but routine. Much of it would be done Earthside many years in advance. There would be plenty of time to seek out the most obscure scenarios for each Kuiper Belt object, where each major improvement in handling a single rock would be worth billions of dollars.

Slingshotting would be important in two different ways: energetic gain, as mentioned, and steering. Energetic gain would work essentially by parasitising the orbital momentum of a planet. This is no novelty; it already is a routine technique of long standing in spacecraft navigation.

Steering is another aspect. Obviously passing a sufficiently large planet in a suitable trajectory can change the course of a body almost arbitrarily within the ecliptic. What is more, by passing the planet at greater or lesser distance, one can affect the angle of change practically as much or as little as one likes. In passing close to the planet, one is in a position to adjust one’s exit direction greatly by adjusting one’s incoming course by only a few tens or hundreds of kilometres. To achieve such a difference would require only the gentlest of nudges or persistent pressure a few years in advance. However, with such a delicate requirement one can see why we would want such an elaborate infrastructure of navigation satellites.

The other steering requirement that slingshotting offers, is one’s position relative to the ecliptic. By adjusting one’s position so that we pass to the north or south of a planet, we can adjust our approach so as to move out of the ecliptic. We could for example hit the north or south pole of Mercury practically vertically, or either limb of Venus grazingly, with an enormous bang in either case. We would deliver many times more energy and momentum than we had invested. It would achieve either excavation or adjustment of rotation as required.  

Riding the Rocks

 

Well then, we know that if we can steer a planet into a good starting position and apply a bit of adjustment at critical points, and can stop our rock against a target instead of having to stop it in space, we have it made.

This is critically important, please note. If we got no more energy out of a rock than we had put into it, we might as well save ourselves the trouble and go and shove at the planet directly.  And if we did that, we could not nearly afford the energy. This whole exercise is predicated on the idea that we might manage to get away with three or four orders of magnitude less energy, by application of a little brainwork, commitment and patience. And being apes rather than termites, we can easily manage that can’t we? 

The way we always do?

All the same, there still is the requirement to apply that fraction of a percent of energy, or nothing special will happen.

Let us then consider a hypothetical project. Imagine a typically peanut-shaped, teratonne, predominantly rocky body, spinning about a short axis, but not so fast that any part of it is travelling much faster than escape velocity for this rock. OK?

Still, the spin is unacceptably high. Our Rockrider selects a suitable spot, based on the prospector’s information, instruction from Earth, and its own calculations, lands there, using tethers as necessary, checks the details, and drills into the body of the rock near one end, probably using plasma or laser drilling for the most part. Together with adjustments calculated in the light of what it finds on the way down, it carefully places a multi-megatonne nuclear bomb ordered in advance in the light of the prospecting report decades before, covers the hole nicely like a cat, retreats to a safe distance a few hundred kilometres away in space and on the sheltered side of the rock, and when the attitude and position are right, it blasts a tidy slice off one end of the rock. The resultant vector of the blast both kills the rotation or very nearly, and accelerates the rock into an improved, more elliptical, trajectory. You see, the depth of the bomb was such that several thousand tonnes of material were blasted off at a modest velocity, imparting a really efficient delta-V in the desired direction.

Waste not, want not! Eat your heart out, Saturn V!

Having checked how well the blast had worked, perhaps while it waited for the blast site to cool, the Rockrider lands again, possibly on the blast site, and anchors itself nicely. It begins to run its nuclear generator and plasma drills and to excavate more material in the form of vaporised rocky or sooty material that it condenses as an impalpable powder in very intense atmospheres of energetic electrons and ions in separate  chambers. The cooled particles become powerfully charged microscopic electrets. An electret wouldn't have to retain its charge for more than a few seconds, but in practice probably would do so for years or indefinitely.

Meanwhile the Rockrider has unlimbered its main thrusters, which are specialised twin (or multiple?) linear accelerators, whether electrodynamic, electrostatic or laser. Details, details... It feeds them charged dust particles that they accelerate to modest velocities, roughly two thirds of the delta-V of the whole system as calculated for the entire trip. Pretty well optimal for the energy utilisation, which is one of the limiting factors for the project. In principle such electret propulsion could be far more efficient than ion thrusters. The reaction mass is cheap. In navigating a teratonne rock we could afford to use thousands of tonnes as charged reaction mass without serious regret.

Right. The Rockrider and its Earth support have calculated not only the best things to do, but the best ways to adjust the intensity and direction of the acceleration in feedback to the response of the rock to the thrust. That is what we call steering, right?

Now it gets boring. That Rockrider is going to sit there for a long time, rendezvousing with a few planets for slingshot purposes during the next few centuries. Possibly it gets a few more charges of fuel from visiting tugs and maintenance craft. “Oh, it’s you again is it?” “Yeah chatterbox. Who did you expect? Goldilox?” A few days before impact, the Rockrider kisses its mount goodbye, and goes off for some maintenance and its next trip, which had been chosen for it before it even started on this one.

Coasting Rockriders could kill time by acting as incidental observers of conditions and events wherever they pass or pause, or by relaying signals wherever convenient.

Notice that there are major differences between any viable options for this kind of navigation and the Buck Rogers stories. There is no question of fast turns and dramatic accelerations (except for the occasional nuclear blast of course.) Everything is worked out years or centuries in advance and gently nudged for centuries en route. We cannot afford the energy or the risks of abrupt manoeuvres, but we can trade energy for time, which we have plenty of if we are to aspire to the dignity of termites rather than apes. 

Another objection that might occur to cavillers is that if it is going to take us hundreds of years to ride a single rock home, and we need 100000 rocks, we will take a lot of millions of years for the project. But that is a blinkered point of view. We would have thousands of Rockriders, all working in parallel, and sometimes in teams. It might be centuries before more than a few of the first rocks began to splash down, but then it would be a flood of hundreds per year. Although it would generally be the intention that each Rockrider would bring in more than one rock, even one typical rock would pay a generous profit for its Rockrider.

A really serious objection for a race of monkeys is that we would be labouring for human benefits thousands or millions of years after we were multiply recycled dust and dregs, and monkeys don't do that sort of profitable venture; they want it fast, cheap, and now. But all is not lost. Though the ultimate bull market benefits are far in the future, there is plenty of bull for the developers en route. Whole dynasties of companies could profit hugely from running the projects, improving the technology, applying the information gained much as we have profited immeasurably from satellite communications, weather observations, and Earth science and mapping, even while moaning bitterly and persistently about the costs of space technology and research.

Preventing a single dino-killer collision with Earth (never mind turning it into a profitable collision with Venus or Mercury) would pay for the whole initiative.

What could be simpler? Or easier?

Or more gratifying?


16 comments:

  1. You require all manner of space craft scattered across the solar system? That sounds like a reason to settle Mars first, and warm it up to "Green Mars" status for a closer base of operations to get at the Kuiper belt. Get the Mars city up to a million people and Zubrin has calculated that it they could cook it up to "Green Mars" status in the following 100 years. That means an atmosphere a third Earth's, radiation protection on the surface, walking in clothes (with a breather mask), oceans, rain, and the start of basic farming. It's not "Blue Mars" with a breathable atmosphere, but it's a start. And it doesn't require 100,000 massive 10km Kuiper belt objects from 40AU away! It only requires 10,000 Space X landings of 100 people each on Mars. Done. Humanity would have a second home, and an economic case for then going further to throw Kuiper belt objects at Mars to thicken the atmosphere for "Blue Mars" status. Who knows? The future Space X 'railroad to Mars' system may have already started out towards the Kuiper belt for Venus by then.

    The parameters of technological conversation change so quickly these days I hardly know where to begin with the presumption that we'll even *need* to tidally lock Venus to settle it. We well may not! The science of the very small, such as nano-tech fabricators, comes into play here. The classic 2 approaches come to mind, but with nano-tech advantages.

    HOT TOP-DOWN APPROACH
    The Venusian atmosphere is so thick, floating cities are possible. They could gradually convert the CO2 into carbon nanotubes that build indestructible space elevator mining tubes that anchor a city to the surface and mine it, despite the incredible pressures? What about future materials that are 'smart' and self-healing, and able to mine the hellish Venusian surface the way the oil industry can now reach unheard of depths and angles? Would such space elevator mines suck material up to the cities floating above, gradually expanding those cities and
    https://phys.org/news/2014-07-terraform-venus.html

    FROZEN BOTTUMS-UP APPROACH
    What if future space nano-fibre manufacturing plants could convert just a few large asteroids into massive solar sails that could freeze Venus, letting us get at the surface? Once the dry ice froze into place, solar power could be beamed down from space to run colonies strip mining the planet for CO2 and spinning it up into space elevators, orbital rings, etc to basically turn Venus into an O'Neil or even McKendree space station manufacturing plant. Once they got the hang of it, and various Rungworld's started deploying around the sun with thousands of times the surface area of Venus, would they even stop? Or would they just keep going until there was no planet left, and the human race had millions, maybe even billions time the surface area of Venus to live on? I'm not kidding. Do the math, this guy certainly has!
    https://www.youtube.com/watch?v=HlmKejRSVd8

    ReplyDelete
    Replies
    1. Firstly, the "all manner of spacecraft" not only carry their own productive justification, but can be employed incrementally as the needs arise. The glib "settle Mars first, and warm it up to "Green Mars" status for a closer base of operations to get at the Kuiper belt. Get the Mars city up to a million people and Zubrin has calculated that it they could cook it up to "Green Mars" status in the following 100 years." Is totally unrealistic.
      1: it assumes that we don't need any non-trivial work in preparation; we not only DO need it, but don't even know yet what we need it for, but it includes heavy industrial equipment and live explorers who will be lucky if they die, bearing in mind what sort of life they will have after their stints. The only human exposure needed for the preparatory phases of the Kuiper belt infiltration would be in the assembly of the space equipment.
      2: The assumptions made about colonising Mars simply are unjustified; they are not even extrapolations, but insubstantial speculations based on resources that at the most optimistic would be challenging to exploit on Earth, where we have other enabling resources available. On Mars you would need to create other resources to get the enabling resources, and yet more resources to create those in turn. And nothing to show for it before it all works. Figures like million-strong cities are ridiculous anyway, as I already have said, and if they were not, then they couldn't support themselves on Mars anyway. And if they could, they could not support a Kuiper-belt assault. Do you remember my mentioning our inability to do similar things here on Earth? You haven't challenged that yet, have you?
      3: "Do the math, this guy certainly has!" Maths like that I did when I first independently thought of Dyson spheres, but what those guys did was not "THE" maths, but just any old maths. Anyone can sling numbers around, but it still doesn't mean that you can do anything with numbers that ignore critical parameters. If you ignore inconvenient facts, you can prove that our current planet could support a human population of 10^25 humans in good health and great longevity. Don't believe me mate, do the maths yourself! Among the items that you might like to include in your calculations, would be the nature of the processing necessary, but do first consider the fundamental nature of thematerials you propose to work with. THEN do the maths.
      Otherwise all that stuff becomes as boring as Trump's wall.

      Delete
    2. Do the maths? Your hot bottoms-up ignores both the fact AND the maths. Never mind the question of what it takes to make carbon fibres from CO2. What about what it takes to make ANYTHING from carbon fibre? Tell us when you get that worked out. And let's see you justify "The Venusian atmosphere is so thick, floating cities are possible." FAT CHANCE! What would they float on? How would they keep cooler than NY in summer? What would they use for resources such as food or industries? Make sure you get your maths right.

      As for the likes of "What if future space nano-fibre manufacturing plants could convert just a few large asteroids into massive solar sails that could freeze Venus, letting us get at the surface? Once the dry ice froze into place, solar power could be beamed down from space to run colonies strip mining the planet for CO2 and spinning it up into space elevators" etc etc, if all you need do is say "what if", then what if you create a magic wand and make all those wonderful things by snapping your fingers to keep away the polar bears?

      Fantasy is one thing, science is another, technology yet another, and infrastructure and sociology yet others.

      Remember: if a system does not have to work, it can meet any other constraint, but one of the constraints in our case is that to be of any interest, it not only must work, but must work well enough; it has to make sense for a start. None of those magic "approaches" you mentioned passes any such tests.

      Delete
  2. Just to be clear, when I say 10,000 landings, I'm not talking about 10,000 ships. It's actually only 1000 ships, with about 25 flights in them . Let's average that down to 20 flights each. That means 10 trips there and back again to get another 100 settlers. So only 1000 space X ships could build a city of 1 million people on Mars within a century.

    ReplyDelete
    Replies
    1. Duzzint make no neverminds and isn't clearly desirable anyway. The ships would have to be of huge value to be worth shuttling back, and anyway, the Martians would be desperately short of resources, so the ships' materials would be more valuable on Mars than between Mars and Earth. In fact, in a rational scheme they should be designed for them and their cargo capacity to be immediately useful to the human cargo suckers after a one-way trip.

      Plus, and hugely more importantly, dumping a million people on a planet without resources is not the same as establishing a city of 1000000 inhabitants. Try looking at what happens when you dump masses of displaced people *on Earth*, where we have huge resources, such as air that one can breathe and water that you can drink, and plants that you can grow, and shops where you can buy food and clothing and factories that can make what the shops don't have, and and and...

      Delete
  3. The fact that you still say "Dyson Spheres" means you haven't watched the video. He *immediately* debunks Dyson Spheres as utterly impossible due to the stresses on such a sphere destroying any material we can even imagine. It's not Dyson Spheres, but Dyson Swarms, that he presents.
    >"Do the maths? Your hot bottoms-up ignores both the fact AND the maths. Never mind the question of what it takes to make carbon fibres from CO2. What about what it takes to make ANYTHING from carbon fibre? Tell us when you get that worked out. And let's see you justify "The Venusian atmosphere is so thick, floating cities are possible." FAT CHANCE! What would they float on? How would they keep cooler than NY in summer? What would they use for resources such as food or industries? Make sure you get your maths right."
    You are responding a little emotionally without even investigating the links I've referred you to.
    First, I admitted from the outset that the nano-fabricators I was discussing were speculative. The reality is we just don't know how future materials and manufacturing technologies might enable space mining. In presume that you *want* some kind of industrial functionality with asteroids? I presume you assume there will be *some* kind of space manufacturing?
    Second, the Hot Top down approach is not that revolutionary in scientific speculation. It sounds like you need to go back to basics and red some of the papers referenced at Wikipedia.
    https://goo.gl/LWqrsm
    Third, you're just *asserting* that a colony on Mars is absurd, not proving that opinion. Then you repeat your *opinion* by saying "I've already told you..." without offering any rationale why? Mars has the potential for a CO2 atmosphere, enough sunlight to grow crops, enough thorium to power Molten Salt Reactors, enough minerals to build all the structures we want, enough water to do what we want... I just don't get your hatred of Mars. It's thoroughly illogical! You want a backup home for the human race, fast? One of the world's most successful entrepreneurs wants a permanent settlement to at least start by 2025.
    "Elon Musk founded SpaceX with the long-term goal of developing the technologies that will enable a self-sustaining human colony on Mars.[95][101] In 2015 he stated "I think we've got a decent shot of sending a person to Mars in 11 or 12 years".[102] Richard Branson, in his lifetime, is "determined to be a part of starting a population on Mars. I think it is absolutely realistic. It will happen... I think over the next 20 years, we will take literally hundreds of thousands of people to space and that will give us the financial resources to do even bigger things".[103]
    In June 2013, Buzz Aldrin, American engineer and former astronaut, and the second person to walk on the Moon, wrote an opinion, published in The New York Times, supporting a manned mission to Mars and viewing the Moon "not as a destination but more a point of departure, one that places humankind on a trajectory to homestead Mars and become a two-planet species."[104] In August 2015, Aldrin, in association with the Florida Institute of Technology, presented a "master plan", for NASA consideration, for astronauts, with a "tour of duty of ten years", to colonize Mars before the year 2040.[105]"

    https://goo.gl/wLxTX1

    ReplyDelete
    Replies
    1. They Dyson sphere, belt, swarm etc etc is allatime sametime. The stresses are a detail compared to the rest of the problems. That is why I didn't differentiate. You don't escape one problem (such as stresses, which BTW are NOT as much of a showstopper as he aserts, so watch him again and this time be a bit more alert for handwaving smoke and mirrors) by ignoring the problems with other ideas and sweeping the ones you do mention under the mat of "future materials".

      >You are responding a little emotionally without even investigating the links I've referred you to.

      You are ignoring the challenge to the problem of the floating cities.

      >First, I admitted from the outset that the nano-fabricators I was discussing were speculative. The reality is we just don't know how future materials and manufacturing technologies might enable space mining.

      That does not constitute a basis for assuming which technologies would render which ideas viable. We use CO2 on Earth as a raw material, be we have a venerable technology for converting it into certain classes of material. Nothing about our technology suggests that its presence on Venus or Mars will be anything like a direct asset. Strip-mining it FCSake! After freezing it out with an F2 mirror! Boggle mind, boggle!

      And as for Mars' CO2, that stingy frost over huge areas! Come back when some tiny minded technologist (as opposed to galactic-minded hand-wavers) actually shows how to do it well enough to serve your million immigrants dumped from the shuttles. Before you do that, have a look at work that has been done on artificial chemo- or photosynthesis, and outline how you would get from the typical products to something to support a colony's survival.

      THEN tell me all about the points I missed in those sales spiels. But by that time you too, might not be willing to buy a second-hand shuttle from them.

      Never mind the maths, the failure of imagination is breathtaking. A far better approach than Dyson anything is to build manageable sizes of dwelling unit of national or even city size around fabricated mini-black-holes in interstellar space. Proven physics (do the maths, remember?) and vastly flexible and scaleable.

      Delete
    2. Damn, just lost another reply. Sorry mate, I just can't afford the time right now.

      Delete
  4. Please look into the other options for Changing the rotation speed of Venus. What some have proposed to speed Venus up could also be used to slow it down, going the other way.

    >"A proposal by Birch involves the use of dynamic compression members to transfer energy and momentum via high-velocity mass streams to a band around the equator of Venus. He calculated that a sufficiently high-velocity mass stream, at about 10% of the speed of light, could give Venus a day of 24 hours in 30 years.[21]"

    Make Venus dark by moving just a few asteroids in and manufacturing a solar shield at L1, then use this to slow Venus down in 30 years.

    ReplyDelete
    Replies
    1. Y'gottabejoking!!!

      >a sufficiently high-velocity mass stream, at about 10% of the speed of light

      Yeah, that's a great idea! you want to create a stream of .1C mass of sufficient size to slow down or speed up the planet's rotation to Earth normal? Did you work out how much energy that would take? Several times the energy that humanity has ever used or is likely to use in the foreseeable future. What was that about doing the maths again? And then you have the CO2 to deal with. I suppose you just snatch the carbon out of the CO2 to make a free carbon-fibre equatorial belt? How would you dispose of the waste O2? And have you calculated the stresses on that belt at that speed? .1C is a hell of a lot more than the escape speed out of the solar system. And if your belt is retained on the planet, then when it fails, nuclear bombs won't be in it for comparison and you might even fragment Venus.
      You would however certainly regain part of your undesired planetary angular momentum. Download the book at
      https://archive.org/details/talesofspacetime00well
      and read on from p 327. It might give you pause for thought. That is a quality book.

      Even just changing the rotation rate a fraction so much *without* the suicide belt would leave you with thousands of years of earthquakes while the planet changed shape. What a hen-witted idea!

      Just as an exercise, try asking yourself the distinctions between the effects of the asteroid bombardment, and the suicide belt. You might find it sobering, both in practicality and in effect.

      Delete
  5. OTHER ARGUMENTS FOR MARS

    “In fact, in a rational scheme they should be designed for them and their cargo capacity to be immediately useful to the human cargo suckers after a one-way trip.”

    You obviously don’t get what Space X is all about. Imagine paying $500,000 dollars to fly from Sydney to Melbourne because you had to buy your part in a plane’s one and only journey. No-one was ever going to use that plane again! A one-way plane trip is just too expensive. No thanks! It’s the same with Space. Space X is about designing a regular shuttle service to Mars to bring the cost down. We can take cargo as well, including habitat in flat-packs. Imagine the first railroad chugging across the great American plains from New York to LA forced the passengers to buy their carriage and then disassemble it and turn it into a house when they got there! But… it’s a rail carriage, designed to travel and bring more people, more luggage, more tools, and more parts on the next ride! Turning a Space X interplanetary ship into a house would give you the most over engineered and expensive house in the solar system. A habitat simply does not need to be engineered to cope with the stresses of take off and eventually accelerating to 100,800 km/h on a journey between the planets. Flatpacks will do, and then eventually with enough tools and engineers and people, Martians will extend their habitats out of local materials. Don’t deny that it’s possible or just reassert there’s nothing there. There’s energy (thorium, sunlight, wind) and matter. Space X want to bring the cost down to about $200,000 per ticket to Mars. That’s affordable. That’s a mid-life crisis, only instead of sea-changing or tree-changing, someone can now change planets! Now, while it might be fun trying to guess what combination of flat-pack habitats, inflatable buildings, tools, modules, compact fuel refineries (Co2 to methane), 3d printers, 3d ice printers, baby bamboo shoots, algae, whatever we’re going to need to get started on Mars: I don’t really have to. You’d have the same job building a shopping list of parts to build the first colony on Venus! Only Venus is a millennia away, and as you say, we may not have that much time. Also, because Venus is in 1000 years or longer, we’ll have centuries of experience and technological innovation on Mars that we simply wouldn’t have if we didn’t bother going there first.

    “Plus, and hugely more importantly, dumping a million people on a planet without resources is not the same as establishing a city of 1000000 inhabitants.”
    Again, that’s exactly the same conundrum you’d face on Venus, pal!

    ReplyDelete
    Replies
    1. >Again, that’s exactly the same conundrum you’d face on Venus, pal!
      Not een close; you disappoitn me. Exercise:

      Work out a logical, practical, safe (vague of course!) outline for starting out on Venus after the bombardment has stopped, the SOx has vanished, the CO2 levels are down to an equilibrium, for establishing a livable environment over a suitably cool fraction of the surface. Stick to currently practical or at least imminent technology, eg nucleic acid engineering, no fancy sunshades or 0.1c suicide belts.

      Delete
    2. Hey Jon, be fair. I have about 4 or 5 posts with many links and arguments you have not bothered to address yet, and you come back at me and ask me to do your argument for you? Sorry, but because you're the one who keeps asserting that there's nothing on Mars and that Venus is going to be *so* much easier to colonise, then *you're* the one that has to demonstrate it.

      At the very least, Mars doesn't have a toxic atmosphere 90 times thicker than our own requiring us to hurl 100,000 giant mountains at it for a millennia just to bash it into a place where the very air won't crush us! Instead, as I keep saying and you keep avoiding, 1000 ships doing 10 return trips each could establish a city that would become self-sustaining and have partially terraformed Mars to "Green Mars" CO2 atmosphere stage in about a third the time your bombardment would have to run. Doable now, with today's technology.

      ****

      Some points about Mars you have not addressed

      4. Its Economic Value

      Mars is worth a lot of money. There are 144 trillion square meters of surface area, roughly the land area of the Earth, available for development. I'm not going to tell you how great all that land is for residential, commercial, and industrial use... go play Sim City.

      An important part of the fusion reaction process is deuterium, a stable isotope of hydrogen. Once we can contain a fusion reaction, the deuterium-tritium reaction has a high yield of energy for the small amount of fuel put in. Deuterium, or heavy hydrogen, is hard to obtain on Earth, but on Mars it is five times more abundant in the form of Hydrogen-Deuterium-Oxygen (See Also: Compositions). A milliliter of liquid heavy-hydrogen fuel would produce as much energy as 20 tons of coal. Deuterium is also important in chemistry because it reacts the same way as hydrogen, but can be distinguished from hydrogen by its mass. These reactions occur slower than normal hydrogen reactions.

      There is an abundance of rare metals on Mars such as platinum, gold, silver, and others. Shipping from Mars to Earth, as mentioned above, is much easier than the other way around. Even more promising is the proximity of the asteroid belt to Mars. Dactyl, the moon orbiting the asteroid Ida shown in this picture, is 1.4 kilometers in diameter, yet it contains more iron that the human race has used in its entire existence. These asteroids could be mined near Mars and shipped from the planet for little cost. What we could see develop is a triangle trade route, much like the one in the 18th century between Britain, the West Indies, and America. The economic potential is colossal.

      5. Its Location

      That brings us to our next point: location. Mars is relatively close to the Earth. Mars sits between the asteroid belt and us, acting as a kind of stepping stone to what lies beyond. It remains close enough to the sun to benefit from its heat (and light) but remains far enough away to be protected from any significant change in the sun's heat output. (We still know little about the sun's long-term heat cycles.)

      Delete
  6. Mars has economic resources and another value: it's safer distance from the sun, safer than Earth and vastly safer than Venus! See points 4 and 5 about the economics.
    http://redcolony.com/features.php?name=whycolonizemars

    You wrote:
    “Try looking at what happens when you dump masses of displaced people *on Earth*, where we have huge resources, such as air that one can breathe and water that you can drink, and plants that you can grow, and shops where you can buy food and clothing and factories that can make what the shops don't have, and and and...”
    Again, the first colonisers on Venus would face the very same issues, no breathable atmosphere, no shops, no jobs, no nothing. Just a world full of resources to harvest over time.

    “And as for Mars' CO2, that stingy frost over huge areas! Come back when some tiny minded technologist (as opposed to galactic-minded hand-wavers) actually shows how to do it well enough to serve your million immigrants dumped from the shuttles.”
    I’ve already quoted the papers. Mars has enough CO2 frozen at the poles to create a greenhouse effect that would cook CO2 out of the regolith, eventually turning it into a 0.3 bar atmosphere. Once again, that’s enough for clothes (with a breather mask), liquid water, oceans, rain, protection from radiation, and the start of a farming cycle. The bottom line Zubrin has calculated is that a city of a million people would be using the resources on Mars to grow their food, build their cities, create their breather masks, and cook up super-greenhouse gases to cook the planet. 1 city of 1 million would take 1 century to cook Mars, using just 1000 Space X ships loaded with 100 people over 10 round trips each, with massive technological, psychological, cultural and scientific advances accruing over just a few centuries.
    I know why you’re nervous. You can see how my small investment with far more immediate returns makes your 100,000 giant rocks over a whole millennia seem like so much economically impossible ideological hand-waving!

    MARS AS PIT STOP FOR VENUS
    Why Mars first? Because it will get us into space faster and cheaper and more reasonably in a shorter time with greater returns, but it’s not a choice of Mars OR Venus. That’s too binary and immature. It’s both / and. Mars is a step closer to the Kuiper belt. After a mere 1000 ships do 10 return journeys each, and the city of a million is up and running and growing their own crops, there’s this whopping great space industry that might start to fragment and point in new directions. Mars will have an accumulation of astro-engineers itching for the next challenge. Future corporations and governments might be in a race to do the next big thing. Can all that methane on Titan supply tanker runs out on the solar system? What’s in those asteroids? What about that Kuiper belt?

    ReplyDelete

  7. What about our moon, and just building a dirty great solar shield factory there to shoot a shield at Venus?
    SHIELD THEN MASS DRIVER
    Finally, on the high velocity mass stream, do you have numbers on how much energy that would take compared to moving 100,000 10km rocks? You do realise that I was talking about setting up that mass driver after Venus was already frozen by a shield? I was suggesting using it to do exactly want you want to do, slow Venus down to a tidally locked orbit. I was trying to help. And you respond with “Even just changing the rotation rate a fraction so much *without* the suicide belt would leave you with thousands of years of earthquakes while the planet changed shape. What a hen-witted idea!”
    Pardon me, but isn’t your whole idea of hitting Venus with 10km wide or wider rocks to slow it down going to do worse?

    “Just as an exercise, try asking yourself the distinctions between the effects of the asteroid bombardment, and the suicide belt. You might find it sobering, both in practicality and in effect.”
    They both end up with Venus parked, except my version involves MUCH CLOSER resources to achieve it MUCH SOONER. EG: A moon base could use a rail gun to fire solar cell shields in towards Venus, both cooling Venus for a century or so and then providing power to the mass driver. You worry about how much power that would take? It would take under half a million square kilometres of solar panels to power our world. But a solar shade would eventually require an area 4 times the diameter of Venus. It could be incredibly thin, with an in situ space station factory sewing component sheets together after they arrive from our moon base. Not all of it has to be solar PV, but imagine if it were? What if in the far future we had a post-scarcity economy where AI and robots provided us with most goods and services. So dirt cheap, that money was almost a meaningless concept. Then a giant solar shield becomes feasible. 4 times the diameter of Venus = an area of 1.84 billion km square. That’s over 3680 times the area required to power the whole Earth today. You don’t think that would run the Mass Driver? The Mass Driver slows Venus down for 30 years. Then comes the fun part, moving the shield out the way and seeing what this parked Venus idea of yours actually does. For in reality, we can model it, but we have no idea. Not really. Would the winds be so terrible that it is almost impossible to land on the surface, or build colonies in the twilight zone? Have we made a huge mistake? How is this actually going to work really? Why didn’t we also get our robot overlords to build huge mass drivers on hydrogen rich planets and shoot hydrogen at Venus to react with the CO2 and make water and carbon? Then we could use our solar shields to mimic the day and night cycle, and make Venus far more Earth like. I’m not ruling your idea out totally, just pointing out that you really don’t actually know what Venus would do parked like this.

    ReplyDelete
    Replies
    1. Sorry EN, you have some sound points and some that aren't even unsound, but I don't at present have the time.

      Frustrating, but...

      Sometime maybe.

      Delete