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Comment Re:Rockets are too expensive (Score 1) 147

Cotton is strong because the individual threads are imperfect and so the strength comes from the friction between the fibres. Current nanotubes have almost no friction between the fibres, so when you spin them together you end up with something that simply falls apart when you pull on one end. There are research projects to try to improve this, but claiming that it's no different from cotton or wool implies a complete failure to understand the problems.

Comment Re:No Dragon 2 Soft Landing Yet (Score 1) 147

Well, they did produce that huge carbon fiber tank. Which appears to have failed during one of their pressure tanks. Really, building such a huge rocket out of composites is crazy ambitious (if not just crazy), but my hat goes off to them if they can succeed.

They've also made a mini-Raptor that they've started putting through tests. The fact that they've apparently managed those chamber pressures without corrosion problems so far is very impressive.

It occurred to me the other day that they have an interesting potential "halfway" route to ITS, which is that since they clearly plan to have different variants of the spaceship (cargo, crew, tanker), they could start off with the cargo variant and instead of a cargo fairing, have an interstage and use that to boost an elongated Falcon 9 (like the Falcon Heavy central core). So the spaceship would function as a first stage until it got its own booster so that it could function as a second stage. It'd be a perfect testbed for their new technologies (same construction style and engines as the booster, just smaller), while at the same time boosting SpaceX's launch capabilities into the super-heavy range. They'd want to use more atmosphere-optimized nozzles, but apart from that... it's already designed to handle much greater heat loads as well as full propulsive landings.

Comment Re: Rockets are too expensive (Score 1) 147

How much would it cost to make 50 thousand miles of 3-foot, paper-thin steel?

Assuming 'paper-thin' means 1mm thick, then that's around 75,000m^3 of steel, or about 680 Gg. At current steel prices, that's about $250-600m, depending on the kind of steel. The cost of getting that amount of steel to LEO (vastly cheaper than GEO, but assume that most of the mass doesn't have to go up to GEO) at current prices (assuming the cheapest possible launch) is just under $4tn.

The real question is why you care, because steel doesn't have anything like the tensile strength required to be a tether.

Comment Re: No Dragon 2 Soft Landing Yet (Score 1) 147

He's first going to have to learn how to launch that fast. That's one area where SpaceX hasn't had much success - getting its launch turnaround times down. Hopefully they will in the future. Also, since an explosion takes them out for half a year or more (regardless of turnaround times), they better up their reliability by an order of magnitude or more, since each increase in launch rate means more possible rockets that can fail. And of course they want the ITS booster to have a service life of 1000x launches, which means an immensely high reliability.

Anyway, SpaceX's big goal is to have their satellite service give them a nearly unlimited demand for launches in the coming decade, as well as a correspondingly huge income from global sales of satellite net / communications services - and to funnel those profits into ITS. Time will tell... but there's certainly no shortage of ambition.

Comment Re:Not Happening Anytime Soon (Score 1) 147

That's the biggest concern I have. People tire of ongoing expenses. ISS seemed neat at first; now everyone hates it. Why would a moon base fare differently?

Long-term presences in space need to very quickly cut ties with earth, on order of greatest resource dependencies down to smallest resource dependencies. Aka, first things like oxygen, propellant, etc, then to industrial chemicals, of increasingly smaller quantities, with increasingly diversified manufacturing facilities, with very complex/low volume chemical feedstocks and manufacturing processes coming last. Cutting all ties is a process that would take centuries. But you can start with the low hanging fruit, bit by bit, and keep stockpiles of everything needed for maintenance that you can't produce locally.

Unfortunately, running counter to this is expansion. Because if you double the size of your operations, you also double your resource demands. So you need to improve resource independence at a faster rate than you grow.

Part of the problem with the moon is that it's just not a great place for ISRU. Volatiles are rare. We've never even sampled any moon that aren't depleted in volatiles, although there's some data to suggest that various volatiles might be scattered in permanently shaded areas (all of them, in the same place? That's a good question). Surface mineral diversity is limited - primarily light, non-volatile elements. Oxygen is at least widely abundant, but locked up tightly. And while the moon offers short transit times, it's surprisingly not that advantageous concerning delta-V. You can't aerocapture there, landing is fully powered (no parachute deceleration), and to get there you have to already be on such a high apogee orbit that it's not much more energy to go into a Mars transfer. Gravity is less and night is two days long. There are a couple "maybe" peaks of eternal light, but that doesn't mean that they're colocated with volatiles; the last I looked into it it looked like the closest suggested find of water was dozens of kilometers away from the nearest such peak, which would be quite the commute (and thus low throughput / high wear).

The moon is certainly the "cautious" option; emergency returns / resupplies are easy there, and communication fast. Its main value appears to be a testing ground for systems while minimizing risk. But it's not a very appealing place from a settlement perspective.

Of course, I prefer Venus to Mars, but that's neither here nor there ;) I'd like to see a parallel program for both, as the same sort of booster and transfer stage can be used for both, so it's only habitat / ascent stage development costs that are doubled. And once you get past the differences in feedstock sources, production industrial processes converge (Venus advantaged by the higher power availability and easier ability to get rid of heat - excepting in the case of cryogenics, where Mars holds the advantage)

Comment Re:Younger astronauts (Score 1) 147

One, there would be howls of protest. Two, you're not taking that argument to its logical end. You should only send pygmy women by that logic.

Women do consume less resources (by a good margin on average) and take up less space, but if I recall correctly are more vulnerable to radiation-related disease. So it's a tossup depending on what factors are constraining your mission architecture.

Comment Re:Rockets are too expensive (Score 1) 147

I have read the book, and it's an absurd degree of wishful thinking. Just ignoring the huge number of things that they just gloss over or omit outright, the materials technology they're talking about is about two orders of magnitude away from what we actually have, and might even be physically impossible. Measurements of individual carbon nanotubes (let alone bundles, let alone bulk fibres) don't approach the strengths being talked about there. Colossal carbon tube does better on an individual tube basis, but again, we're nowhere even close to the materials tech required. And for what? For a massive, very low throughput, tiny safety margin, most-failure-modes-unaccounted-for, low-power-efficiency means of access to space? Colour me unimpressed.

If you want something better, I recommend looking into Lofstrom loops (launch loops). Current materials tech, high efficiency, high throughput per unit mass, no orbit restrictions, and works even on tidally locked bodies.

Comment Re:Rockets are too expensive (Score 2) 147

Quite true. The materials technology required is about two orders of magnitude away from actual materials technology, for starters. And among the countless other problems with space elevators, they're not actually all that efficient. Laser power beaming over those distances works out to single-digit transfer efficiencies, and microwave power beaming even less (microwave power beaming to space can be efficient, but only if the receiving antenna is huge). And no, you can't regularly hang things or run power wires up a space elevator - the mass of the cable has to be vanishingly small.

Active-suspended structures, such as Lofstrom loops, are a much better choice. Power transfer efficiency can be greater than 50% and current materials technology should be sufficient. They can also be designed to shoot payloads into any orbit (unlike space elevators), and work independent of the properties of the body in question, as well as having far greater throughput per unit mass. There's really no reason to choose a space elevator over a Lofstrom loop.

Comment Re:I remember the same predictions about Amazon (Score 1) 202

Amazon's advantage over B&M will disappear after they start charging sales tax.

Yeah that pretty much happened. Amazon seem better/cheaper for some things, especially computer parts. But compared to the rest of the internet (including B&M stores, where I can check stock and prices online) they're often not the cheapest any more.

The thing is, magic internet pixies don't really fix the need to have a serious logistics network, which basically puts them on the same footing as the other major players. Those guys did not exist in a vacuum of no competition and had to put quite a lot of work into making their networks efficient anyway. It's also interesting to see them compete with B&M chains where they've got such things down to a fine art: for example in grocery deliveries in the UK, there's already a fiercely competitive market with immense volumes and huge logistics chains (don't forget the chilled and frozen goods!) and compared to the competition, Amazon kinda suck.

Comment Re: Not a problem at all (Score 1) 989

Depends on your definition of feminism indeed.

Yes, but only in a trivial sense. The super extreme view is held be a small fraction of people who inhabit certain places on the internet and happen to be very noisy. If you attempt to use that definition outside of that group, or people aware of that group, you will essentially be using a private definition and will be misunderstood.

I'm taking the current "modern" feminists (third wave feminism) which you can see in action on Twitter (eg. the GamerGate instigators).

I don't see how the instigators---either the dude who posted that long screed or the people attacking Anita Asrkeesian---are feminists by any definition of the word.

more modern definitions leave the equality out of it.

No, not really. This is not to say you can't fine some wingnut somewhere who does so. The internet is a large place and you can find someone professing to belong to some cause to say almost anything. The fact that a small number of nutcases exist doesn't really say anything about the general cause. Mostly, equality is left out on in the rather peculiar fantasies of TheRedPill, AVFM and other such places.

A traditional feminist movement in modern eras would be primarily focused on countries around the world where women don't have the rights yet to run for president

No. You're saying what YOU think feminists ought to do. There's still plenty to do back home. There is also more wrong in the world than any one person can try to fix, and complaining that someone is concentrating on a cause they like, not some other cause you don't even like enough to do anything about is a cheap rhetorical trick. It's meaningless because it can be levelled at more or less anything, because there is always somewhere else worse in the world. Come to think of it, why are you wasting time arguing on the internet when there are people being tortured in North Korea? You should be spending your time helping them.

you could just be a part of it and not see the issue of what your group represents (eg. if your definition of feminism comes from AmiMojo

If you're going to claim AmiMojo is part of a hate group then have a massive [citation needed]. That says far, far more about your biases than about his IMO.

Comment Re: Maybe, but maybe not (Score 1) 202

My memory is that if Amazon had been happy with just books and bookish stuff they would've turned a profit much sooner. A smaller, and possibly short lived, profit...but sooner.

Profit is a pretty misleading metric. Amazon had enough income to exceed their operating expenses for quite a while. This is the intuitive definition of profit, but not what appears on a balance sheet. They were taking all of that money, using it as collateral to borrow more, and then investing all of that in growing their business. That meant that they didn't make a profit, but only because anything that would have been profit was ploughed straight back into the business. They were also very willing to shift markets. They created a cloud offering because they had to over-provision in their data centres to cope with spikes in demand and realised that they could sell some of this excess capacity. This turned out to be so lucrative that they poured all of the profits from their retail arm into expanding it for years. They did the same thing with the Kindle.

Comment Re:Sounds good to me (Score 2) 202

For the employer it's a win, but for consumers and staff it's not always

It actually isn't. There was a Freakonomics episode about this a few months ago. The problem is that front-of-house staff in the USA are now getting a significant proportion of their income from tips, which are a percentage of the total cost. This means that their income has gone up a lot more over the past couple of decades than that of kitchen staff, to the point where someone with a cooking qualification can still make more money waiting tables than being a chef. Even worse, it means that the income varies hugely between days, so it's trivial to find someone to work on a Friday or Saturday night, because they'll make loads of money, but restaurants often can't find people to work on Wednesday or Thursdays, because they'll make a lot less (for regular slots, you can establish a rota, but if you need cover for a sick employee then it's much harder).

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