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Comment Re:sunfire / in my stellerator / makes me... happy (Score 1) 92

Hmm, thought... and honestly, I haven't kept up on fusion designs as much as I should have... but has there been any look into ionic liquids as a liquid diverter concept? In particular I'm thinking lithium or beryllium salts. They're vacuum-compatible, they should resist sputtering, they're basically part of your breeding blanket that you need already... just large amounts, flowing, and exposed. Do you know if there's been any work on this?

Comment Re:sunfire / in my stellerator / makes me... happy (Score 1) 92

The plasma facing material faces a flux of 1 neutron per 17,6Mev. By contrast, nuclear fuel cladding faces a flux of ~2,5 neutrons per 202,5 Mev, or 1 per 81 MeV. It's certainly higher, but it's not a whole different ballpark. And yes, you're dealing with higher energy neutrons but in a way that can help you - you've often got lower cross sections (for example), and in most cases you want the first wall to just let neutrons past.

There's a number of materials with acceptable properties. Graphite is fine (no wigner energy problems at those temperatures). Beryllium is great, and you need it anyway. In areas where the blanket isn't, boron carbide is great. Etc. These materials aren't perfect, but they're not things that get rapidly "converted into dust" by neutrons. Really, it's not the first wall in general anyway that I'd have concerns about, it's the divertor. The issue isn't so much that it takes a high neutron and alpha flux and "erodes" fast - that doesn't change the reactor's overall neutrons per unit power output ratio, and if you have a singular component that needs regular replacement, said replacement can be optimized. The issue is that you have to bear such an incredible thermal flux on one component. Generally you want to spread out thermal loads, it makes things a lot easier.

Comment Re:Authoritarians will always rule. (Score 1) 411

you need to read closely, the claim is that abortion should be outlawed if and only if, the state outlawing abortion can (without risking the life of the pregnant woman), remove the fetus. Once the fetus is removed, it is then becomes the duty of the state to maintain and grow the fetus using whatever incubator technology they have available.

Sorry, I missed the science fiction premise. I will try harder to remember that this is Slashdot, and not a place to get serious about discussing real solutions to real problems.

Comment Re: Authoritarians will always rule. (Score 1) 411

Third, it's possible to push a woman into sex without actually raping her.

For this purpose, I'll go ahead and lump coercion in with rape. But not just empty promises. If you want promises, get a marriage contract. Ideally the state would piss off out of marriage per se and instead there would just be child responsibility contracts. So, barring rape or coercion, what's wrong with the plan is that women are abused by the court system. That's a problem we need to fix anyway. Let's also fix that problem.

Comment Re:Fusion energy is impractical (Score 1) 92

When a fast neutron hits an atom it knocks it out of its position and frequently changes it to a different element/isotope.

The same applies to slow neutrons, so....? Your average 14,1 MeV neutron is most likely to inelastic scatter down to the point where more exotic reactions than (n, gamma) are basically impossible (excepting a few specific cases, like 6Li(n,t)4He - again, not dangerous). Only a small percentage of your 14,1MeV neutrons (depending on the material they're passing through) have a chance of undergoing anything more than a standard (n, gamma) transmutation. Unless the system is specifically designed to cause that (for example, a beryllium multiplication in the lithium blanket). The standard case is inelastic scatter once or twice -> elastic scatter a bunch -> become partially or completely thermalized -> capture.

This turns a solid structural material into a radioactive powder

What happens depends entirely on what's being bombarded. Many materials are perfectly fine after long periods of exposure - slow or fast neutrons. Light ions in particular are usually either A) relatively unaffected (sometimes requiring sufficient heat for proper annealing, sometimes not), or B) incredibly good absorbers, leaving nothing dangerous behind. See a more detailed breakdown above.

Comment friend's computer hit by this (Score 3, Informative) 31

i have a friend who called me to say that their computer had had the default browser search settings changed to some adware. so i checked the instructions on how to remove it, only to find that the settings shown in the screen-shots *weren't there*. turns out that inspection of the timestamps on the filesystem, the phishing-malware had *replaced* legitimate system libraries, which enabled them to disguise the malware and prevent its own removal. it was necessary for us to go round some friend's houses, drop the macbook into single-user mode and copy over replacement files from an identical copy of macosx.

now, this is the first time i've ever dealt with macosx viruses, but i was surprised that it was so easy for my non-technical friend to be fooled by a phishing attempt which scared her with the "you have 2,500 viruses do you want us to fix it?" tactic. as a purely software-libre end-user for the past 20 years, all i can say is, "welcome to the monoculture world, apple. your false sense of security myth is well and truly over, and you have a hell of a lot of catching up to do".

Comment Re:Are you being simple? (Score 1) 6

You've established that you view everything done by Hillary as being in the primary interest of spreading evil around the world. Even in that light, why would her decision to use a separate email server have to be something she thought up entirely on her own? Are you really claiming that her special kind of evil is such that she wouldn't borrow any tactics at all from anyone who had her office before her?

Considering how much philosophical overlap exists between the actions of the current POTUS and his immediate predecessor, it is entirely reasonable to expect that the underlings of the current POTUS would themselves borrow tactics from the people who previously inhabited their same offices.

Comment Re:More interesting is Age Adjusted Funds (Score 1) 61

I know splitting between equity and bonds is a typical allocation strategy, but I really feel like any bond holdings are inappropriate if you're not planning on retiring in the next ten years. The rule of thumb was always ten percent more bonds every ten years closer to retirement, but I feel like that's much too conservative.

I agree, my personal mix is 90 percent S&P 500 index, 5 percent MidCap, 5 percent Bonds. When I'm about 5 years out, I'll convert some more to bond funds, but sadly most of these age adjusted funds have a heavy overweight on bonds, for some reason.

Comment Re:Venus (Score 1) 304

Plant cultivation is far, far harder on Mars, for many reasons.

1) Natural light: the solar constant is 1/5th as much on Mars as on Venus, and you're guaranteed to have dust clinging to your greenhouse glazing. More on this later.

2) Electricity: Same for solar power. And fission power systems (as opposed to radiothermal, which is far too weak) are 1) a rather expensive line-item to your development costs, 2) heavy to transport, and 3) complex (complexity is not good when it comes to operation in space). Beyond this, most people vastly underestimate how much power it takes to grow plants under lights - you need 1-2 orders of magnitude more area of solar panels than the area of plants you can grow. And the size of the LED lighting systems you'd need is very significant in its own right. Plants consume way more light to grow than most people give them credit for. The real world isn't The Martian where one can grow potatoes on normal room lights ;)

3) Room: Abundant, practically unlimited space comes free with a Venus colony. Space is extremely expensive on a Mars colony - it's a pressure vessel. Another downside to limited space: plants don't like it. It leads to humidity and temperature instabilities and buildups of gases like ethylene that are far more poisonous to plants than carbon monoxide is to humans. These gases break down, particularly in sunlght, so in big areas they're not a huge problem - but in confined spaces, they can deform and kill your plants readily. Pests and diseases also thrive much more in confined spaces.

(My comments on plants come from experience: I grow a small "jungle" in an indoor environment, entirely on artificial light)

So, while it is of course possible to grow plants on Mars, it's far, far easier on Venus.

As for opressiveness, once a wall is opaque, you can't really perceive how thick it is.

Indeed, I wasn't talking about wall thickness :) Just the issue of being enclosed in small spaces. Most designs call for integrating as many windows as they can, but that's always going to be limited - windows are a lot heavier for a given amount of surface area and can't be shielded for radiation exposure.

And I'm not sure how attractive Venus would be in comparison

So, you don't get a landscape, that's true - the surface isn't visible there. But at the desirable altitudes, there is still a "view", the clouds are dynamic there. A few kilometers further up and it's just a continuous haze (which may lead to rainbow effects below, there are some papers debating this ;) ), but in the "earthlike" layers clouds will come and go. Like living among the clouds on Earth.

But no, you don't get a landscape outside. Your landscape is the Garden of Eden you make inside, surrounded by clouds. :)

There's also those ever-present lightning storms all around you - that's going to be noisy, and a serious maintenance issue

The current state of research isn't "ever-present lightning". Again, unfortunately our knowledge of Venus is so poor compared to Mars, so it's hard to make definitive statements. But lightning appears to be "about" as common on Venus as it is on Earth.

Another thing that we need to learn more about is atmosphere variation. We've seen what appears to be significant variations in sulfur levels on Venus over time - it seems that the sulfur may be the result of frequent or continuous volcanic activity. So how the atmosphere will vary over time is an important question to be able to answer before we can send humans.

And how do you plan to prevent lightning strikes through your habitat?

Again, we don't know the distribution of lightning between a) different altitude layers, b) different latitudes, and c) over time. We actually don't know at this point if it's ever a risk at all - and if it ever is, whether it's avoidable or not. If it's not avoidable, then yes, one would need lightning protection (I presume faraday cage-style rather than any sort of ion shield), which would add mass and require a more difficult testing regime. If it is avoidable, or is never a problem: then there's no issue.

Definitely need more data on this one before we can send humans! It's time to stop neglecting Venus.

but since you're in the middle of the cloud layer they won't actually be getting anywhere near as much sunlight as they would in orbit, maybe not even as much as they would on Earth or Mars

Actually no :) The light levels at acceptable flight altitudes (~51-55km) are comparable to Earth on a clear day (except that you also have almost as much light also reflecting up at you as coming down at you). Depending on the frequency, it blocks about half of the light from the sun - but twice as much light hits Venus. Mars, however, gets 40% as much light as on Earth - when the dust isn't blowing. Sometimes you get dust storms which can last for months, easily enough to kill plants from lack of sunlight.

Note that solar panels don't have to be outside the envelope, if the envelope is transparent (which I've been assuming thusfar). They can even be built into structural elements (for example, solar roofs on shelters or walkways). It'd cost under 10% of the power, and in turn they'd be shielded from winds, lightning (if a risk), icing (if a risk), corrosion, etc, and your wiring needs would be greatly reduced. I really don't see a point to having anything outside the envelope except for the return rocket (even that's not 100% necessary, but probably a lot easier than a rocket-sized drop-bay ;).

If the ambient pressure is ~1atm, then you have roughly as much air above you as you would on Earth, but without a magnetosphere you're going to be counting on that air to block a lot more radiation.

I read a paper about this before but can't be bothered to dig it up again ;) Okay, okay, just a second.... hmm, this may have been the one. They simulated the Carrington Event and one previous one that was even stronger, and found that even they wouldn't be problematic at 62km (let alone a more realistic 53-54km, which has orders of magnitude more atmosphere over it). That is to say, they calculate 0,09Gy. Radiation therapy in humans is 45-80Gy. A CT scan is 0,008 Gy. So it's like getting a dozen CT scans, but nothing like undergoing radiation therapy. And that's at a much higher altitude than people would actually live at. Long-term GCR at actual colony height, according to their graphs, would be about 1e-8Gy/20h, or 4,4e-6Gy/year - not at all "dangerous". Levels are indeed higher than on Earth, but they're not problematic like they are on Mars. You don't need added shielding, you're sitting under a mass of shielding equivalent to a ~5 meter tall column of water. And the atmosphere above you creates a small induced magnetic field to boot.

Comment More interesting is Age Adjusted Funds (Score 5, Informative) 61

A lot of American and Canadian retirement accounts are in "age adjusted" funds, which are really just a mix of mutual funds or ETFs of bond funds and stock funds.

If you check, you'll find most large firms have an S&P 500 index from Vanguard or Fidelity (like the VINIX) which has an expense ratio of around 0.02 or 0.04 percent, and a Total Stock Market index with an expense ratio of around 0.05 or 0.07 percent and a Total Bond Market index with an expense ration of around 0.10 or 0.12 percent.

You could replace the "age adjusted" fund that charges you 0.40 to 0.65 percent with an automatic stock fund and bond fund allocation, e.g. 70/30, and then just reallocate periodically. Cost to you drops from 0.40 to 0.05 percent, in many cases.

That's all these "wealth firm robots" really do. You can buy the underlying components and pay less.

It's the fees that kill you. You don't notice them when returns are 12 percent, but when the market is crawling (like today) with 1-2 percent returns, you sure notice the fees that siphon off up to 1/4 of your earnings.

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