Ken Fabian

Airbrush - I don't know about "alarmists" but scientists studying tropical Cyclone/Hurricane (TC) frequency and intensity with global warming mostly aren't coming up with predictions of more frequency. They also admit a lot of uncertainty, in part because there is naturally a lot of variability; I haven't heard of any predictions from what I think are credible sources that haven't come with admitted high levels of uncertainty. But more intense but less frequent TC's is a more usual conclusion than more frequent; data examined do show a significant upturn in North Atlantic Hurricane intensity - Measure of total power dissipated annually by tropical cyclones in the North Atlantic (the power dissipation index “PDI”) compared to September tropical North Atlantic SST (from Emanuel, 2005) The basic premise that warmer sea surface temperatures affect formation and intensity seems sound. The evidence of a trend of warmer SST's looks solid. As Ten Oz points out, the data on precipitation also shows a significant upturn.

I hadn't noticed any "lefty-leaning hegemony" on this site. Certainly some subjects like climate change, nuclear energy, evolution or GMO's can reveal political or other biased assumptions or conclusions, prompting the examination of underlying motivations and heated discussion, yet strictly moderating out the political/ideological aspects can prevent discussion of matters of real significance.

I remain unconvinced about the financial viability of these kind of space activities, even with strong government/taxpayer support. I may come back to that discussion sometime, but later.

I wondered if meteorites have provided a comprehensive sampling of the kinds of asteroid materials - minus the volatiles - that can be expected to be found or if significant absences might remain. Samples of a few asteroids have been returned but samples all the major types haven't been gathered. Does the surface material mirror the overall mineral mix or would core samples by drilling be needed? Nickel-iron would need little refining if it's to be used or sold as nickel-iron - ease of processing would make it attractive, but not as attractive as either metal in pure elemental form. Finding native iron that is relatively pure and not alloyed with nickel would make mining more attractive. Finding native platinum group metals would be more attractive than extracting it at a hundred ppm from nickel-iron - it looks like the estimates of platinum content are based on presence in nickel-irons. Gold - would make money but I'd find it perverse if that were a primary target for asteroid mining. Perhaps it is the asteroids rich in copper rather than nickel-iron that could have better economic prospects - not native copper but a copper mineral seems abundant in some.

I've started a new topic related to this - How reliable are estimates of asteroid mineral content?

In a discussion that wandered into asteroid mining possibilities I wondered what is known with confidence about the mineral resources within asteroids. Reconciling the estimates thrown around with the admitted large uncertainty about the quality of mineral ores within asteroids seems to be essential to estimating the economic viability of any attempts to exploit them. Clarity about what form the desired materials take rather than simple estimates of concentrations and total quantities is needed; a pure elemental metal, even at low concentrations may have good potential for mining - relatively simple techniques can separate and concentrate them - whereas higher concentrations but in the form of alloys with other metals are not so desirable. Not impossible to separate and purify but involving far more complex and costlhy. Examining meteorites here on Earth appears to be the primary source of estimates of mineral potential. The presence of nickel-iron as kamecite and taenite is certain, but is there evidence of the presence of relatively pure iron that is not alloyed with nickel? Whilst there is an existing market for alloys of nickel and iron, if it is pure iron or nickel that is wanted, separating them is no easy matter. Platinum group metals are the ones that seem to arouse the most excitement and there is no doubt they are present, and in concentrations that here on Earth would arouse interest. However they appear to be present as part of the content of nickel-irons like taenite, ie present within those alloys. Is this correct? Have any been found in more pure or concentrated forms, as relatively pure native metals or concentrated alloys, perhaps with others of that metal group or as stony ores ie chemically bound into compounds? I think the enthusiastic proponents of asteroid mining tend to underplay the costs and difficulties - and they no doubt see my scepticism as overstating them. For now I'd like to know more about the resources themselves than go too far into the challenges of exploiting them.

I think I'll leave the discussion - not much to say that I haven't already.

Prometheus - earlier posts made clear that there is a lot of room for near Earth space activities to be commercially viable; it's the successful exploitation of space resources and space colonisation in the absence of profitability - one hopes preceding and leading to it - that I think present a much bigger challenge. Extraordinary claims of inevitable outcomes are made and I don't think they are inevitable. For one thing I don't think technological advancement follows an exponential curve - it will be an S - curve, with an upper boundary, mirroring in aggregate how individual technologies develop, with diminishing returns as the easy big gains are followed by smaller and harder ones. On the railway comparison I will stand by my argument that it is a tenuous and misleading parallel. Arguments for supporting subsidised space activities based on it are disingenuous. And dis-ingenuousness in place of compelling arguments aren't going to win me over. Nor do I think the onus is on me to show that the outcomes aren't inevitable, rather the onus is on the proponents to show that they are. Early railways were making a profit from very early; there was only 8 years between the first full scale working steam railway and the first commercially successful one (In UK). Their development was not subsidised. The US began building it's railway system after the commercial viability had been proven elsewhere. The first was financed by stock offerings in the Baltimore and Ohio Railroad company and it earned money for investors - not sure the extent of government assistance, likely expediting land acquisitions at the least was provided. It was a commercially viable enterprise from day one , arguably before the first track was laid or any freight was hauled - and it's commercial success made it possible to push the railways further. It serviced already existing communities and an already existing economic function, competing successfully with other forms of transport, that were, themselves, economically viable. That is very different to how space development has proceeded. So I find arguments like - "The first steam engine 1698, the American transcontinental railway was built 1863 - over 165 years later. Yet you think 70 years is enough time to say space technology has failed to overcome it's hurdles so let's give up?" - hard to simply allow to pass. Not that I've said "let's give up" - rather, I'm sceptical that the extraordinary outcomes hoped for are likely. Certainly I think the Manned Mars push is misguided, unnecessary and wasteful, whereas I see proving the feasibility of resource exploitation directly as essential to achieving that visionary, space resource rich future. State sponsored programs can help but ultimately it's for commercial projects to prove. I do think the estimates of the value and benefits of those corollaries are overly generous in what they count - another kind of hype - including the implicit claim that many useful technologies could not exist at all except by that means. As an R&D hothouse the US space program not only added to overall R&D it overlapped with some as well as displaced some and I think there is good reason to think R&D would have continued elsewhere, delivering if not the precise same outcomes, still outcomes of great and potentially comparable value and some would have been for serving and advancing many of the same needs. Government sponsored R&D hothouses - space focused ones included - do have my support, just not unconditional or unbounded support and not because I expect them to establish homo spaciens in their new habitat. Not that I have any real influence; I'm just saying what I think. Still, I don't think commercially successful patents and products or near space commercial activities can replace or induce successes at finding and proving the viability of utilising space resources that is the precursor to viable colonisation. Proving the commercial viability in practice should be done by commercial enterprises with business plans that win the financiers over - and I am not stopping them. I'm not saying it's all impossible so don't even try but I think it's a long way from inevitable and made less inevitable when significant steps - giant leaps - along the way must be done in the face of uncertain commercial viability. Pig iron sells in the $200/$300 per metric tonne range, with bulk shipping halfway around the world down near or below $20 per tonne. That is the kind of commercial benchmark that space resources has to beat. It looks like a huge gap to bridge to deliver space iron at competitive prices like that. Rare high cost metals are another matter but usable bodies have not been found yet and some of the expected values of various asteroids are little more than hypeful speculation. If native, elemental rare metals or quality ores are found in quantity they may be recoverable but if they are locked in alloys with other metals, like nickel-irons, they may be unrecoverable. It's certainly possible, even likely that resources of high value can be found but I keep coming back to the costs involved in exploiting them. "Inevitable", like "railways" isn't a compelling argument.

Again, I am not opposed. But a realistic assessment of what is required must replace hype. I don't have to accept, let alone support overhyped expectations, nor should large expenditures of taxpayer money be undertaken on the basis of popular support built upon such hype. And it is 2017, where we have a far greater understanding of what is possible and what is required - and expect to make investments on sound and detailed business plans. Another misleading historical comparison - those railways made money from the very first sections completed and further construction was financed with near certainty of financial returns on each further section. Utilising space resources appears to require a whole system be built before anything except "corollary" benefits can be realised; those are inadequate by themselves. I think a greater level of real confidence that the result will be economically viable cannot be an afterthought. The other and perhaps more appropriate lesson from history is that speculative ventures like new world colonies that couldn't pay their own way within the existing greater economy ultimately failed. A whole lot of taxpayer funded R&D contributed economically - I see no reason to believe space exploration delivers more and better outcomes dollar for dollar than other major investments in R&D - sure the US space program was exceptional in scale and reach but from the start it was built on the popularity of exaggerated expectations as well as being an expression of national pride in the face of geopolitical implications of near space as a military objective. A lot of those advances could have been delivered by the parallel and overlapping military aerospace R&D programs where the same problems were begging solutions. I am a strong supporter of R&D for many worthwhile goals - and I am not trying to exclude space goals - but extremely large financial commitments to specific sectors and goals should be based on realistic assessments, not hype.

Area54 - perhaps as compound interest applies to the sunk costs invested without financial returns? Or maybe you can elaborate on how doing things that cost more than they earn can be paid for by compound interest. Or what happens to compound interest when the capital gets written down or written off due to economic disruptions? But I suspect the point you are trying to make is like others here, that technological advancement is somehow equivalent to compound interest; but just as the ability of an investment to get interest is dependent on the actual details and conditions, tech development depends on real physics and engineering; rocket tech running at 80% efficient can't be magicked to 180% efficient by compound interest. Getting the last 20% of real potential is likely to be a case of diminishing returns - and when the returns cost too much the project gets abandoned, no matter we might wish otherwise. Whole new technologies have their own development costs - and extreme performance tends to be tech that is harder to make and to make reliable or low maintenance or low cost. Tech development itself has strong dependence on economics, on the willingness of governments to fund the stuff that has no clear economic goal or on financiers to fund the stuff that has a reasonable prospect of making good financial returns; one can follow the other but a strong prospect of good financial returns is still essential for space enterprises to flourish. I think it's pointless to argue the far future or it's inevitability when the gap remains so large; actual ways to close that gap would be welcome in this discussion. Or even compelling arguments that the gap is, or can be made, much smaller. I'm not seeing them.

What I see is unwillingness to acknowledge the size of the gap between what is technically and economically feasible and what is actually needed to kick start colonisation of space - or the gap between what's sufficient for colonies to pay their way as part of the Earth based economy and sufficient for enduring survival entirely cut off from it. Assertions of inevitability just don't cut it. Historical examples all look to bear only superficial and misleading resemblance to the problems and their solutions. Realistic suggestions for how the gap can be closed have not been forthcoming and a reversion to arguing that other motivations will be sufficient in the absence of economic viability seems to just confirm that it remains a long way out of reach. On the one hand people are saying have all the technologies we need, on the other that we don't but will inevitably achieve them. I don't think either has been demonstrated. Whilst Osiris-REX for example, is a reasonable early attempt to sample and return asteroid material that can prove it is possible there is no way that $1billion for 2kg is suggestive of real economic prospects for the utilisation of space resources. Even I would say that it is inevitable it can be done cheaper, but I suggest a minimum billion scale improvement is needed and that is not inevitable.

No, I never said waiting a few hundred years is a valid approach - I don't think ongoing technological progress delivering the means to make it easy is an inevitability. Nor is continuing what we are doing adequate to the task; I think only a huge investment at a scale far greater than anything to date has any real prospects - greater or equal to a manned Mars mission but with the practical goal of demonstrating the true feasibility of mining, processing and using space resources. I think doing what we are doing now will not get us there. Commercial mining enterprises would not be a legitimate goal of NASA or other government sponsored space agency but proving the viability of it might be. Space activities that do pay their own way - satellites for Earth based uses - can be successfully serviced by private industry; contracts to service the needs of those space agencies for exploration are government sponsored activities - taxpayer money is being put into private industry rather than private industry putting money into space exploration. No-one is stopping commercial ventures based around space resources - they continue to not make economic sense. The scale of what's needed before it becomes economically viable exceeds any prior examples - none of which truly parallel what Big Space faces. Previous examples were of commercially proven technology being used at greater scale, within a world far more abundant in readily usable and saleable resources than space is; the space resources are there but they are not readily usable. Big historic railway projects got up after they had the technology well worked out and it was proven to be very successful and profitable at smaller scale - proven before the big investment took place. We've had 70 years of opportunity to prove exploiting space resources is viable and failed to do so. The massive push that is needed to establish sufficient infrastructure isn't going to happen until clear demonstration that exploitation of those vast resources is feasible and have real commercial prospects.

As a primary motivation it doesn't work. That it is a benefit deriving from space development for other reasons is what I've said all along. The priority needs to be to demonstrate this to be true, not producing "inspirational" government sponsored reality TV programming ie Manned mission to Mars. It's the lifting of all the hardware from Earth needed to make effective use of those resources that is the issue I keep coming back to. Until it's in place and proven everything does have to be lifted from Earth. How big the pre-investment must be in order to achieve effective use of those resources has not been addressed. It's the achieving of sufficiently sized and robust space economy that can survive on it's own that concerns me. Those abundant rotating colonies won't just appear there without compelling economic reasons. Space activities that are outposts - and dependent on a healthy Earth economy - are more likely than true self sufficiency. That is a whole other level of size and complexity. Things that could go wrong? Solar flares and cosmic radiation bursts taking out all the communications and transport. A cloud of interstellar debris that no-one noticed coming at high velocity. Essential equipment breaking down and lacking the deep expertise - no matter that you have all the manuals - to repair or replace it.

No, I don't agree with this; this reverts back to this "inevitable that problems will be solved with time" assertion of BeeCee and others, as if technological advancement is a natural law. It's not. The potential to drop the price of space travel (and space mining and space refining and space manufacturing and space agriculture...) by a significant amount - I'd think a lot more than 1% in the near term - is there but whilst time is a factor it is the identifiable physical and engineering possibilities and financial backing that carry it forward and define the limits. What can be done, including the funding of ongoing development, is still bounded by economics. Technology can made to work but not be economically viable. Resources can exist in abundance and not be economically viable. Whether that "lot more than 1% in the near term" is sufficient to get over the hump is not clear to me - and I'm not getting responses that clarify; I think we disagree on how big an investment is likely to be required (how high the hump is) as well as whether those advances that we can treat as achievable carry it past the threshold of human activities in space being self supporting. Just as whether those near term improvements is sufficient to carry a space push past the critical mass to be self supporting is not clear. Civilisations - economies - produced tech advances but civilisations collapsing can and often did take detailed knowledge of their advances as well as the economic capability to achieve them down with them. Other civilisations, because of distance and isolation, did carried on. Now there is convergence into a single economy; collapse, should it happen, is likely to be global. I don't see much sign of good overall management in the face of identifiable problems of global scale so the prospect of the "inevitable" tech progression stalling and going backward due to changed geopolitical realities looks very real to me. And whilst much knowledge will persist, what will be irretrievably lost is actual working expertise and continuity, so that even having all the plans for a space launch system and the funding does not assure the ability to build it. Large, diverse, wealthy economies are fundamental for enabling these things and that applies to the size and capabilities of communities in space being able to do more than exist as an expensive expression of national pride - or worse, be no more than a government subsidised reality TV program, which manned "explorations" such as to Mars risk becoming. Wrong objectives; Mars is a dead end if establishing a working space economy is the goal. The economics of these space activities can't be treated as an afterthought. Which comes back around to what the minimum threshold is before they can break even. BTW, I suspect that a space society/economy would be more fragile and more at risk of extinction than human life on Earth. More likely that Earth will be the long term lifeboat for space civilisations than the other way.

Moontanman - it doesn't matter that military budgets far exceed NASA's; you haven't provided an argument that will divert the funding from the one to the other. Lifeboat scenarios won't do it - and will continually lose out against deep bunker options in military thinking. They are already in place and work for all but the most extreme disaster possibilities. No matter that quantifying the value of military expenditures is impossible or that it includes a vast amount of waste, the financing of a big space push is going to be a separate matter, that will have to be on it's own merits.

It's not about how much time; whether this is attempted now or attempted in some distant future the problems with achieving a kind of critical mass for being a self supporting enterprise are going to have to be faced. Technological advances will occur but, just as it was found that taking commercial aviation beyond the speed of sound was possible but it failed to thrive, there are no guarantees that the ones most required or desired will be delivered. The advances needed are not inevitable. Like Area54 pointed out above - our Earthly problems like climate change could be economically constraining enough to make investments at the scale required beyond reach, especially with enduring division, rejection of expert advice and wilful mismanagement; the geopolitical consequences of excessive fossil fuel use are going to occupy nations and polities for centuries to come and the opportunity to pursue large scale speculative enterprises may get harder over time, not easier. Manned missions to Moon or Mars are in my opinion an extraordinary wasteful vanity - the inspiration value (and broadcast rights - probably the only real means to offset costs!) cannot compensate for failure to aim that precious support at more fundamental objectives; it's not people walking on Mars that will win the financiers over, it is successfully mining, refining and producing material commodities from space sources. And until those commodities are capable of earning real money from Earth markets it won't take it past the threshold that matters most to ongoing financial backing. Even being able to reduce requirements for materials from Earth isn't enough as long as the 'trade' only goes one way - or how do space colonists pay for their accommodation and living requirements and for the equipment that makes them productive? There are advances that would help - a lot cheaper launch from Earth costs as well as much greater capacity are critical. The long term visions I'm seeing here seem to include reliable small scale fusion generation as taken for granted but the combined efforts of the most advanced industrial nations haven't managed any working fusion generation so far so it's by no means assured that more time will solve the problems. It has to be something a space economy can make itself, reliably for enduring self reliance. Fission will need to rely on nuclear fuels from Earth; I don't think there is any real expectation that ores with sufficient concentrations of uranium or thorium will be found anywhere that hasn't has geothermal and hydrothermal processes to concentrate them, ie fission technology requires planets not asteroids; if the planet isn't Earth then there is another whole world of essential infrastructure needed. Fission rockets? Nerva's may work if revisited but will probably parallel other extreme technologies; durability and reliability is difficult to achieve let alone guarantee, no matter what we might wish. Big and risky pre-investments seem needed to develop exotic alternatives into genuine rocket drive options. I remain very dubious about the workability of Orion's and don't even think about using them for launching from Earth. Solar power can work a long way out from the sun but at the asteroid belt it would need huge mirror fields - 30x or more concentrators to get equivalent to solar intensity near Earth; big mirrors are possible in zero gravity but likely to be very fragile. A messy mining operation nearby could be a serious hazard to such a power supply - and one of the cited benefits of space has been absence of environmental regulations... at least for activities outside the habitats; inside them obsessing about environmental integrity and recycling may exceed that of Earthside fanatics. A cloud of ejected mining waste would be better out at the asteroid belt than near precious space assets nearer to Earth but I'm not convinced solar collectors would survive it. Moving asteroids and processing them closer to the Earth and Sun? Perhaps, but it needs to be shown to work at smaller scale before attempting to push billions of tons towards the vicinity of Earth. A lot of infrastructure needs to be in place, wherever it's done, even at smaller scale, to refine and process it, all of which must come up from Earth and be paid for. Is there an expectation that the abundant iron will not be contaminated with nickel? Perhaps nickel-iron alloys can find significant markets by being cheap - if it can in fact be mined and processed and delivered cheaply - but it is pure, uncontaminated iron, for making desirable alloys that will be in demand. I don't think much of anything we do in space will prove easy, simple or cheap. The great risk is that, despite their abundance, space mineral resources will be not be economic to exploit. But that initial push, how big it has to be to carry it past being a subsidised burden and into self supporting and how that can be achieved is what still concerns me. I'm a long way from convinced there is any real prospect of it in any near future I can envisage.

BeeCee, Moontanman, I'm not opposed - I just real doubts that the robotic explorations, placement of astronomical instruments or people in space can pave the way for commercial exploitation that is an essential prerequisite to colonisation in space. Lifeboat scenarios aren't going to work as motivation - it has to be the other way around; colonies have to achieve economies of sufficiently size, complexity and comprehensive competence for other reasons to develop the full range of capabilities needed for enduring survival in the absence of a continuing supply line from Earth. Those other reasons need to be economically viable and for space resources to be exploitable a whole lot of pre-investment has to be in place, specific to those enterprises. Whilst there are crossover elements just the scale alone makes the infrastructure for launching robotic explorers or service the ISS unsuitable. Optimism about what space can do for us isn't what's needed - clearly there is an abundance of that; it's hard plans that have reliable expectations of profit, that bankers can be optimistic about are what are needed. It's a catch 22 - asteroid mining won't be viable without a lot of on ground and in space infrastructure and capability and that won't get built without the certainty that later viable mining and refining operations will recover the costs. My concerns are around those thresholds, past which things grow without subsidy - which I think are much higher than the extreme optimists are saying. The scale of pre-investment to have any hope of establishing a self funding space economy, the scale that an in-space economy has to achieve to be able to survive if all trade with Earth were cut off - these are the problems I have with space enterprises. I think they are much larger than the extreme optimists are saying. Now people are discussing building massive orbital structures, like these fundamental problems of achieving the essential pre-investments will take care of themselves through the generous application of applied optimism. And object if I say the optimism looks and sounds like a form of science fiction.

We are not currently under imminent threat of extinction; other kinds of serious problems can and do rate as more urgent and in combination they represent a significant risk to long term efforts to exploit and colonise space - economics you know. Attempting to read into my doubts about the viability of space enterprises some kind of callous willingness to sacrifice the human race is not addressing the issues I've raised. I don't like the attempts to shame me into agreeing with you. As a motivation, going to space as an extinction prevention measure is both premature and I think has a high risk of being ineffective without some remarkable technological advancements - the same problems that impact the viability of space activities with more immediate goals and motivations. Achieving those goals appear to be necessary precursors to any capability for self supporting space colonies capable of being an off world backup for mankind. I'm willing to discuss why I think that.

No-one has convincingly demonstrated that it is inevitable, just expressed extraordinary optimism that it is. A point you may be avoiding. Without favourable economics it's not inevitable. Nor is technology inevitably going to advance sufficiently to achieve those favourable economics. It may but it may not; greater capabilities may come with greater expense and with diminishing returns on R&D investments. Vanity projects I can see; populism within wealthy nations can achieve that and space ventures do have a solid body of popular support so a presence in space is likely to continue for the foreseeable future. That isn't the same as economically viable or self supporting or inevitably going to expand or lead to a future of favourable economics. A functional, enduring, healthy and wealthy Earth economy is, itself, not an inevitability but it looks essential to these optimistic scenarios. A sustained history of failing to be profitable (outside the communications and Earth sensing satellites) is cause to believe that just trying a bit harder for a bit longer won't be enough - and whilst a whole lot of tax dollars spent on space R&D delivered useful and marketable inventions from the US moon program there is nothing intrinsically superior about space R&D; similar scale R&D spending with different focus would also deliver useful and marketable inventions, just not the same ones.

Using materials found in space in situ sounds great - but in my opinion people are grossly exaggerating how readily that can be done and downplay the costs and difficulties of doing so, the inverse of BeeCee's view of my position. Recalling a doco on doing repairs to Hubble, dealing with a handful of screws presented a team of leading engineers with a year of planning and preparation; sure, some of that would be once off (designing a power screwdriver that didn't twirl the operator around each screw for example) but those are a long way from being the mass produced, off the shelf items that in situ mining, refining and high tech manufacturing require. I think it is in fact very difficult, requiring technology that doesn't exist, using infrastructure that hasn't been built - and I believe it is not economically sound to develop and build such expensive infrastructure in such hostile conditions so far ahead of any reasonable expectation of financial returns; rather, the infrastructure is the necessary prerequisite to any such expectations. Yet building in space for other purposes, where those are not expected to deliver significant returns, seems unlikely to deliver the infrastructure such projects need. There is no real reason to expect any inevitability to any of it. Not even inevitability of continuing subsidy and popular support space ventures have previously enjoyed. Hype abounds here - and that, like the various motivations cited - is inadequate to achieve the extraordinary expectations being expressed. Economics as much as physics and technology is a difficult to surmount limiting factor so I am not surprised that it is those more ephemeral and idealistic motivations that are looked to keep things moving in a spacewards direction in the absence of any economically compelling ones. Comparing to military - or any other large scale spendings that have difficult to quantify benefits - is as dubious a comparison as comparisons to colonisations using sailing ships. I'm not convinced that the optimism is warranted. What minimum infrastructure to mine an asteroid? How much industrial capability in space is needed - starting from a base of zero - before such an operation can be undertaken and how far between that and delivering in quantity to customers who pay? It looks like a huge gulf. What minimum capabilities are needed for a space colony to be self supporting? Much more than any attempts at remote mining I would expect. More crucially, how big does a high tech dependent economy and populations have to be to support just the ability to reliably reproduce the basic, essential infrastructure for enduring survival, without reliance upon Earth's economy?

I'm saying exploring and exploiting space resources are so unlike historic explorations and colonisations that any similarities are superficial and very misleading; those historic "new" world colonies died or thrived according to their ability to participate in the existing sailing ship enabled trading economy. They were "discovered" and established using long proven, widely used technologies, very often the cheap run down vessels that were no longer economically viable, a step short of being stripped of salvage and scuttled; any explorations and colonisations of space requires at the minimum the most advanced technologies, much improved and at far greater scale than currently exist - the low cost versions of these are a necessary prerequisite, to start with, not a hoped for benefit that might emerge along the way. A huge pre-investment is needed that has no historic equivalent that I'm aware of. The not-imaginary technologies currently in play remain far short of what is needed to be financially viable - and the hypothetical improved and enlarged iterations remain hypothetical and unproven, no matter that they may appear, as a schematic on a screen, technically viable. The economic benefits are not obvious; (leaving aside the near value of near Earth satellites for purely Earth based reasons, where the benefits are clear) as soon as we move our sights beyond Earth orbit the costs escalate ahead of the potential for economic returns. Vast resources yes but the costs and difficulties are extreme. It requires such a huge pre-investment necessary to exploit even the most accessible space mineral resources that break even look - pardon the pun - astronomical. There is no starting small to mine asteroids or the moon or Mars and investments on that scale don't happen without far greater certainty of lucrative payoff on bank approved time scales than can possibly be given ahead of those projects going ahead - a catch 22 that I've only seen addressed by proposing vastly more government subsidy of space programs - and those aren't even aimed at delivering what is needed. The urge to seek better pastures well suited early homo sapiens - pushing past that mountain range or beyond that desert really could and did deliver them abundant resources and opportunities as well as distance between intractable problems they left behind, and they could do it with what they carried on their backs and with the skills within a few individuals - because even the high rocky places and harsh deserts are far more habitable and their resources more readily exploitable, than anything in space. Whilst the appeals to that primitive urge to seek better pastures make good PR and induce continuing popular support, they can't and won't deliver the opportunities wished for and in that sense it's a kind of false advertising.

The primitive urge to seek new and better horizons and leave intractable problems behind rather than face them. The popularity of science fiction that tends to downplay or completely bypass - by some imaginary tech brilliancy - the extraordinary costs and difficulties. The illusion that it would be a lot like the successful historic colonisations that happened on Earth. The false expectation that ingenuity can overcome all limitation. The belief that it will be not just economically viable to do so, but deliver enormous economic benefits. The belief that space colonies can provide enduring security and defence from existential threats. The unlikely expectation that humans in space will enjoy greater freedom from regulation or societal constraints.

Mostly the common examples given of science being badly wrong are ancient history - and long since corrected. The example of "don't know" tend to have competing schools of thought and acknowledge the ongoing uncertainty. Climate change science doesn't even genuinely figure as one of the examples of either; Arrhennius had the fundamentals of the climate role of CO2 worked out not long after the IR absorption and re-radiation properties were documented. Even the 1970's global cooling hype was unrepresentative of the state of climate science at the time, something that a National Academy of Sciences report "Understanding Climatic Change" in 1975 made very clear.

GeniusIsDisruptive - you haven't said what you think of climate science - or at least not within this thread. The kinds of points you make are strongly suggestive of rejecting the mainstream science on climate. Any attempts to evaluate the relative costs and benefits of our energy and emissions choices will be skewed if starting with assumptions that the science is wrong and presumptions that there are no serious downsides to releasing gigatonnes of CO2 into the atmosphere each year. The impacts of climate change itself - not only the impacts of climate change avoidance policies and choices - on the capability of billions to have a decent living can't be simply set aside. "WHAT IF you are wrong" also applies to the Conservative Right's position - and given the abundance of persistent, clear expert advice supported by every peak science body, all that contradicts it, it's a far more credible case that it's them that are wrong. The contributions of that politicking to the inadequacies and compromises - to lack of emissions reductions and displacement of fossil fuels - of efforts to date shouldn't be underestimated. It prevents the depth of support renewable options need to achieve their full potential, just as it prevents the largest body of ongoing support for use of nuclear for climate (within Right Conservative politics) from being mobilised effectively. I have a lot of trust in science, it's methods, institutions and professional standards. Those have served us well and still do - people like Giaever in the video Tim88 presented above are not prevented from doing any alternative climate science but object that low quality science will be rejected by publishers and subject to strong criticism; it's a conspiracy to maintain high professional standards the climate science deniers face, not a conspiracy to exaggerate the influence of GHG's on climate or exclude science that might show otherwise. When even a layperson like me can see the gaping holes in Giaever's arguments it's no surprise that he gets criticism and even derision from the actual working professionals he disparages and slanders. The climate problem is a global economy-wide one that can't be fixed purely by voluntary emissions reductions efforts of concerned individual - and those extremists that live frugally with zero emissions will get dismissed as loony extremists and ignored, without raising their credibility with people like "Genius" and Tim88 at all. Those favouring strong climate action that aren't so extreme will be accused of hypocrisy instead of lunacy so there will be no satisfying the critics. My household for example, self supplies electricity 95% of the time and exports 4 to 5 times as much low emissions energy to the grid as it imports. I minimise vehicle use and unnecessary travel and look forward to affordable electric vehicles that I can charge at home but that takes organised efforts by others, including at the government policy level; I haven't achieved net zero emissions but I don't think that is hypocrisy, it is recognition of the socio-economic as well as technological constraints within which I live. I don't hate fossil fuels, but the expected, deferred costs of the consequences of their excessive use must be acknowledged and faced squarely. I recognise that it must be a transition away from excessive fossil fuel use, where ongoing emissions must be accepted in order that the transition be orderly, to minimise economic disruption - and that simply ceasing emissions is not appropriate. It is not a transition aimed at stopping people being rich or having vacations or driving vehicles or having prosperity, no matter that there are fringe extremists who appear to have such aims; the extremists aren't driving this or where it looks like they are that is almost certainly a case of lack of direction and competence from those who do hold authoritative positions of trust and responsibility. It's aimed at sustaining prosperity by avoiding irreversible harms from climate instability. It's not about depriving anyone of prosperity, it's about having our cake and eating it too.

Paul - A lot more real physics - and far beyond the basic stuff that you aren't yet on top of - will be needed to advance space propulsion. There are some proposed methods that don't involve launching reaction mass out the rear but those involve outside forces like sunlight or solar wind. Unless that piston gets shot out the back, never to be used again, the stopping and moving it back to it's original position will use as much energy as it took to push it back in the first case - and a bit more, given there will be efficiency losses.