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> If a common stem word was what was wanted, there was no need to add -eto, and especially not the -o

What was wanted was common etymology, and the root comes down from Latin via French, so "bilo" = document, or bill; "bileto" = small document, or ticket. The etymology is exactly parallel.

> The only plausible reason I can see for it being bileto and not, say, bilet or bille is to increase the similarity to Spanish and Italian

Familiar forms are a fortunate consequence of Zamenhof's chosen lexicon and system of grammar, but they aren't necessary and in many cases can be misleading - see False friends.

Above all, agglutination rules. If a word formed from combined parts makes grammatical sense but looks different from any other language, that's just hard luck. There are exceptions: "malsanulejo" (place for sick people) has become somewhat archaic, replaced by the much more recognizable "hospitalo."

From this page
https://en.wikibooks.org/wiki/...
"One of the main motivations for the usage of the GPL in FOSS is assurance that once something is released as FOSS, it will remain so permanently."
My understanding is that means in perpetuity.
After you go to /dev/null it's still GPL.

Last I heard, Google has all of its internal services exposed to the public internet. This means that when an incident like this happens, anybody can exploit it.

Using a VPN (or equivalent, such as requiring a dynamic SOCKS tunnel through an SSH bastion, a.k.a. a jump host) would at least add one layer of protection beyond this: jump into the dev network (which may or may not be the same as the office network), then connect to internal services (selective use of proxies is made easier with things like FoxyProxy). That way you need access to the network in addition to access to the server within that network.

A subset of that network could be made available (via VLANs, IPTables on specific SSH bastions, or the like) for remote contractors who only need access to certain servers.

> I'm not a rocket scientist. What am I missing here?

It so happens I am - see my space systems engineering book for proof ( http://en.wikibooks.org/wiki/S... )

Launching from a carrier airplane at 10 km altitude approximately doubles the payload compared to the same rocket starting from the ground. The Pegasus rocket launched from an L-1011 airplane showed this. You can watch a SpaceX launch video to understand why. It takes a Falcon 9 about 1 minute to reach 10 km altitude and Mach 1, which is about the conditions for an air-launch. During this time, the first stage consumes about 45% of the fuel it carries. The flight to this point has been more vertical than horizontal. When you are thrusting upwards, it is counter to the Earth's gravity, so the acceleration is less than if you were thrusting horizontally. You are also fighting drag, and the back-pressure of the Earth's atmosphere. When you start at altitude, and oriented mostly horizontal, all these forces reducing your performance are minimized. So the fuel you burn is used more efficiently, resulting in more payload than just the avoided fuel burn from the first stage. The net result is about a doubling of payload.

So what good is this? Airplanes fly many many times, so the cost of the plane is divided by the number of times you fly it. In fact, this airplane recycles parts from two used 747's, so it cost less to build than an entirely new one would. The 500,000 lb of drop mass it can lift can include a reusable first stage rocket, and a fairly small second stage. This would reduce the throw-away hardware for each flight dramatically.

The first version of this plane will be carrying new Pegasus rockets, like the old L-1011 did. I think that's because Paul Allen has put limited amounts of his money into this project. Once they get the plane working, the next step would be to develop the rocket stage. It's possible they would look for outside funding or partners for that part. From a business standpoint, their problem is the airplane part took so long to develop, that they have two serious competitors already building reusable rockets (SpaceX and Blue Origin). A carrier plane has some advantages over a fixed launch site, like being able to avoid bad weather, and a wider range of launch times and inclinations. It can also serve other markets, like oversize cargo delivery. But I see it as a "come from behind" situation for space launch.

Wow! I never would have guessed. Writer2LaTeX provides Writer export filters for LaTeX and BibTeX.

LaTeX/Export To Other Formats

This about LibreOffice WORRIES me: The download web page doesn't display correctly in either Firefox or Internet Explorer.

> there's a good chance that we've reached peak jobs and the number of people who need to work to provide for all goods and services will start to shrink.

I've spent the last several years working on the concept of Seed Factories ( http://en.wikibooks.org/wiki/S... ). These are starter sets of core machines (lathe, solar furnace, modular robot, etc.), which are used to make parts for *more* machines, until you have a mature factory. This is similar to the way a biological seed grows into a mature tree. The mature factory then produces things people want and need. The growth and operation of the factory is mostly automated, working from stored design files.

The starter set is less expensive to buy than a full factory, and being mostly automated, less expensive to run. Groups of people can split the cost of the starter set, and tend to the growing factory part-time, in addition to regular jobs. As the factory grows, it can produce more products, and the owner/operators can work conventional jobs less. There will still be personal service type things, and some people will work because they enjoy the work, but basic stuff like food, housing, and utilities can all be automated away to a large degree.

I'm convinced this sort of transition is not just possible, but inevitable, because it has better economics than the old way of doing things, and better security. A regular factory will lay you off to save a buck. That doesn't happen if you are part owner. It could go 100% automated, and you still get the stuff you need. During the transition period, it gives people a fall back position if they lose their main job. They just go work at "their factory" instead, while looking for another paid job.

Here you go.

> we don't even have a Wikipedia page on it yet?

We have a WikiBook half written about it: https://en.wikibooks.org/wiki/...

There's a Wikipedia page on self replicating machines: https://en.wikipedia.org/wiki/...

But "fully automated self-replication" is both a limiting concept, and *hard*. There is no reason you can't make different machines than the ones you start with, or different sizes. So a "starter set" can be smaller and simpler than the final factory. All the complexity is in the stored computer files that tell it what to build. There is also no reason that it has to be 100% automated and make 100% of its own parts. Those are theoretical ideals like 100% efficiency. We can tolerate some manual labor and buying parts and materials from outside. The only real requirements are to be efficient enough to compete with conventional manufacturing, and have enough surplus production to pay for the things you can't make on your own.

It's not. That's why we are building the first self-bootstrapping automated factories here on Earth:

https://en.wikibooks.org/wiki/...

Once we have enough factories that have grown to full capacity, we tell them to build rocket factories and launch pads, and send new seed factories into space:

https://en.wikibooks.org/wiki/...

It's not. That's why we are building the first self-bootstrapping automated factories here on Earth:

https://en.wikibooks.org/wiki/...

Once we have enough factories that have grown to full capacity, we tell them to build rocket factories and launch pads, and send new seed factories into space:

https://en.wikibooks.org/wiki/...

I'm part of a project to build this kind of self-bootstrapping Seed Factories, for Earth first, then later in space. There's a report on applying the concept to space at:

* https://en.wikibooks.org/wiki/... (part 1)
* https://en.wikibooks.org/wiki/... (part 2)

I've corresponded with Metzger, and agree with his general idea, but disagree about placing the seed factory on the Lunar surface. The surface only gets sunlight half the time, while in high orbit you can get sunlight 100% of the time. The Moon is severely depleted in volatile compounds because it was baked for hundreds of millions of years, and is too low mass to hold on to easily vaporized materials. Near Earth Asteroids complement the Moon in terms of ore types, and the optimum place to bring everything together is a high orbit near, but not on, the Moon.

I'm part of a project to build this kind of self-bootstrapping Seed Factories, for Earth first, then later in space. There's a report on applying the concept to space at:

* https://en.wikibooks.org/wiki/... (part 1)
* https://en.wikibooks.org/wiki/... (part 2)

I've corresponded with Metzger, and agree with his general idea, but disagree about placing the seed factory on the Lunar surface. The surface only gets sunlight half the time, while in high orbit you can get sunlight 100% of the time. The Moon is severely depleted in volatile compounds because it was baked for hundreds of millions of years, and is too low mass to hold on to easily vaporized materials. Near Earth Asteroids complement the Moon in terms of ore types, and the optimum place to bring everything together is a high orbit near, but not on, the Moon.

Dear Mr 3208 (if I did the binary conversion right),

I taught a class on space elevator design last year:

Notes: https://en.wikibooks.org/wiki/...
Slides: http://imgur.com/a/cCTY5

I should like to make a few comments on your post:

* There have been a number of small scale "space tether" experiments. These bear about the same relation to a full space elevator as flying a kite across a river does to a suspension bridge across that river. We have long way to go before we are ready to build a functioning space elevator.

* The popular image of a space elevator (a 60,000 km vertical cable attached to the ground) is based on a 121 year-old thought experiment by space pioneer Konstantin Tsiolkovsky. That design is laughably impractical, and nothing like what a modern version would be like.

* A space elevator is a transportation infrastructure project, like a bridge or an airport. We don't build that kind of infrastructure for a few tens of vehicles a year, neither would we build a space elevator. The economics would make no sense.

These comments should not be taken as implying I am against the idea. On the contrary, I think space elevators will be very important at some point in the future, and therefore I and many others have done work on the concept. But the time is not yet ripe for them to be built.

The unobtainium is called "Near Earth Asteroid materials", from the almost 15,000 known objects. Whatever orbit you want to go into, there will be some asteroids "near" in velocity terms. So you scrape some rock and dust off the surface of the asteroid, and use it to shield your "transit habitat" on the way to Mars or the Belt. The habitat doesn't stop, but goes in a repeating orbit, picking up new crew each time. During the trip, you process some of the rock into useful products, like fuel, oxygen, water, and metals. If you run low, you send your asteroid tug to get more rock.

And before you call me a "space nutter", my office was on the factory floor where the Space Station modules were built, and I'm working on a textbook for the next generation of space systems engineers ( http://en.wikibooks.org/wiki/S... ), so I do have a clue what I'm talking about.

Since the turn of the century, the number of known NEA's has increased 15-fold, electric propulsion has increased exhaust velocity ten-fold, and solar arrays have tripled power/mass ratio. It's a different world than the one you probably think exists.

Ignore him. Go look at my space systems engineering book ( http://en.wikibooks.org/wiki/S... ) for a survey ot propulsion methods.

Because back in the 1980s computers booted to the BASIC command line interpreter/REPL. Nowadays, there is, more or less, no such thing. Closest similar thing most non-geeks will get to is a browser console, and while that is reasonable debugging tool for pros, it's not a similarly friendly programming tool for beginners.

Every copy of Windows has a command prompt which will let you write and execute batch files. Not that I'd recommend that as a way to learn programming, but most of the functionality is still there. Just not in a popular "language". I think the bigger impediment is that users expect everything to be in an easy-to-use GUI nowadays, and aren't all that interested in writing code which will only run in a command prompt. (That and the switch from procedural to event driven programming drove everything up an abstraction level.)

My secret programming language in the 80s; there was a shareware batch file compiler. Made .com files so I guess it wouldn't work any more.

Because back in the 1980s computers booted to the BASIC command line interpreter/REPL. Nowadays, there is, more or less, no such thing. Closest similar thing most non-geeks will get to is a browser console, and while that is reasonable debugging tool for pros, it's not a similarly friendly programming tool for beginners.

Every copy of Windows has a command prompt which will let you write and execute batch files. Not that I'd recommend that as a way to learn programming, but most of the functionality is still there. Just not in a popular "language".

I think the bigger impediment is that users expect everything to be in an easy-to-use GUI nowadays, and aren't all that interested in writing code which will only run in a command prompt. (That and the switch from procedural to event driven programming drove everything up an abstraction level.)

You may be interested in my space elevator class notes and slides:

https://en.wikibooks.org/wiki/...

https://imgur.com/a/cCTY5

Article is wrong, so very wrong. Then again it's the Toronto Star, also known in Canada as the Red Star and is known to take a very authoritarian view on things. You enjoy that citation now which will give you a brief overview on criminal and non-criminal privacy rights and you can enjoy this one too. Which reinforced S.8 of the Charter of Rights and Freedoms. You can also find more cases using "the citizen's right to a reasonable expectation of privacy" on this site.

> Do you give your work/time away for free?

Yes, I do. See https://en.wikibooks.org/wiki/... and check the edits on any page. For that matter, look at all of Wikipedia.

> the advantage in space is less than 7 even for poor-efficiency installs like the 15% CF on my garage roof in Toronto.

You are neglecting that sunlight in space is 36% more intense than at standard sea-level conditions. In cities like Beijing, the ratio is higher due to local pollution.

> you think you can launch an entire industry to the moon for less money

Well, near-lunar orbit, where you get full-time sunlight, but not an entire industry. What you launch is a starter set of automated machines (a "Seed Factory" - http://en.wikibooks.org/wiki/S... ). These machines make parts for more machines, and bootstrap up to an entire industry. At first you have to supplement the machines with items brought from Earth, but as your industrial capability grows, the need for that decreases.

> Gradually dying all the time. That goes directly into the CF of a SPS.

Solar panels on the ground lose output power too, about 0.5% per year. How fast they degrade in space depends on their orbit and details of their design.

> A panel in space will deliver the same amount of power to the grid over its lifetime as a panel on the ground.

This isn't correct. The one in space has 24 hour sunlight, and it's 36% more intense. Ground-based solar cells degrade slower, but the rest of the panel besides the cells (front sheet, frame, back sheet, wiring, mounting) is exposed to the weather, and can fail before the cell output is low enough to require replacement.

> you wouldn't put solar panels in the "average location".

Tell that to Germany and the U.K., who are installing lots of solar panels.

> You don't even have the beginnings of a plausible concept, let alone anything working.

I have a Wikibook partially written ( http://en.wikibooks.org/wiki/S... ), and we have an R&D location under development. What have you got?

Actually, the ratio is 7:1 in space vs an average location on Earth. 24 vs 4-5 hours/day of usable sunlight, and 36% brighter Sun above the atmosphere. The economics of space power then boil down to if you can provide power from space for less than 7 times as much as the same solar system on the ground, space makes sense. Otherwise it doesn't. Per your arguments against:

* Launch costs - The point of using local energy and materials in space is to avoid those massive launch costs. Orbital mining has mass return ratios of hundreds to thousands to 1 (depends on where you mine, and how), so the amount you need to launch from Earth is greatly reduced.

* Expensive maintenance - Communications satellites typically last 15 years with zero maintenance (though they do carry spare hardware). They consist of solar panels, and microwave transmitters. Solar power satellites have the same parts, just way way bigger. So maintenance should be minimal, and what there is can be automated, since the SPS has lots of copies of the same items.

* Expensive transmission systems - Klystrons and Gyrotrons are pretty simple devices. If you can make solar panels in space, you can make those too. You will need thousands, so you would automate the production.

* Large ground-based stations - Solar farms on the ground need that too, so that cost is a wash.

* Beam weapons - The power beam can't be focused smaller than a few km, so the beam intensity is less than or equal to sunlight. The focusing is determined by the wavelength, size of the transmitter antenna, and distance from space to ground. I wouldn't recommend standing in the beam, but I wouldn't recommend being inside a coal plant furnace or a nuclear reactor either.

* Putting 7 times as many panels on the ground - This is the correct answer today. Launch costs would have to come down a lot, or mining and production in space would have to be well developed and efficient for space power to make economic sense. Those don't exist yet, but that is not an argument to stop research. It's just an argument to not build space power plants *today*.

* Self-replication - this is very difficult, but not required. Automated machine tools today can make parts for more automated machine tools. They don't make *all* the parts, just the metal ones. Mostly automated machinery that can make most of the parts in space is sufficient. The remainder of the hard-to-make parts are sent from Earth, and humans on-site or by remote control do the tasks that automation can't handle. You are correct that this works just as well on Earth. A starter set of machines that can mostly copy itself and make parts for other machines is called a "Seed Factory". Working on that concept is my day job. See https://en.wikibooks.org/wiki/... for a path that starts on Earth and uses the seed factory idea to expand into space.

* Moon vs asteroids - The various types of asteroids (metallic, carbonaceous, etc.) are different compositions from each other and from the Moon. Depending what raw materials you need, you will likely want to mine both. Asteroids don't stand still. Even if they have an easy to reach orbit, they are not always in the right place in that orbit. So your departure windows are limited. The Moon has a more limited range of elements available, but it's always nearby, and has a low enough orbit velocity you can mechanically throw cargo into orbit. The right answer will depend on a detailed assessment of actual needs, which as far as I know, nobody has done using up-to-date information.

My reason is making money by expanding civilization into the Solar System. There are huge amounts of untapped energy and material resources out there. For a description of how the "mining and manufacturing based space program" would work, see:

https://en.wikibooks.org/wiki/... (part 1), and

https://en.wikibooks.org/wiki/... (part 2)

My reason is making money by expanding civilization into the Solar System. There are huge amounts of untapped energy and material resources out there. For a description of how the "mining and manufacturing based space program" would work, see:

https://en.wikibooks.org/wiki/... (part 1), and

https://en.wikibooks.org/wiki/... (part 2)

Having spent a career in aerospace, I think I'm qualified to answer your untutored questions:

> Send up massive amounts of material, to do something "heavy" in free fall

No, space industry is based on using materials already in space, the Moon and Near Earth Asteroids to start with, because it takes less energy to get them from there than from Earth. The first product is *fuel*, used to deliver and maintain the orbits of the 1250 active satellites in Earth orbit. After that comes maintenance of the satellites when they break. Lack of fuel and broken parts force the replacement of entire satellites, at a cost of billions a year.

> Or the massive amount of rocket exhaust would be just great for the environment?

The most efficient rocket fuel in general use is H2 + O2, whose exhaust is water. SpaceX's rockets use kerosine + O2, but they could probably be made to run on biofuels from plants.

> loonacies like Space Elevators

I taught a class on them last summer. They're quite feasible with proper engineering, which unfortunately the popular descriptions are not:

https://en.wikibooks.org/wiki/...

Moving 1000 tons of asteroid rock to near-Lunar orbit counts as heavy in my book. So does processing that rock to useful products.

You guys who arm-wave 3D printing always seem to forget you need spools of plastic filament or other material to feed the printer, and power to run it. If you supply those at more than hobbyist scale, it becomes heavy industry.

Have a read about self-bootstrapping industry in space: https://en.wikibooks.org/wiki/...

The best propulsion system I know of (and I wrote a wikibook on the subject: https://en.wikibooks.org/wiki/... ), is using the Sun as a gravitational lens to focus a very powerful laser on the ship. The ship uses the energy to power a particle accelerator. This has better performance than matter-antimatter propulsion because:

* Antimatter annihilation is theoretically 100% conversion of mass to energy, but storing the antimatter is likely to require massive overhead. So the system level matter to energy conversion is going to be much less than 100%. I'd be surprised if you could reach 10%.

* If the energy is coming from an outside source like the Sun, there is no upper bound to how much you can use, even more than 100% matter to energy conversion.

* If your fuel is accelerated to relativistic speed in a particle accelerator, then thrown out as exhaust, it will gain mass according to Relativity. So you can eject more mass than you start with in your tanks.

We know that gravitational lensing works, astronomers use it all the time. Since the Sun makes an enormous lens, it can focus on a small target, even at interstellar distances. To slow down at the end of the trip, keep your beam collector pointed at the Sun, but flip the particle accelerator to point forward,

You may be interested in this report I'm working on:

https://en.wikibooks.org/wiki/...

Rather than one or two places, it envisions settling the whole Solar System using networks of self-replicating factories.

Sounds like you've got the gist of it. C only has a bitwise shift (where the end that the shift would "empty" is filled with zeroes for unsigned integers), not a bitwise rotate (ex. 00001011 rotated right by 2 becomes 11000010), so the closest thing to saying "bitwise rotate this" is using a set of expressions that would have the same behavior. Since a bitwise rotate is the same as splitting the binary number into two parts (of sizes determined by the desired rotation amount) you just have to create the two split numbers, then OR them back together. The Wikipedia example tries to be somewhat universally workable (using CHAR_BIT, sizeof(), etc. to make it work with virtually any unsigned integer type without modification) which is why it's a bit confusing. A simplified example:

If the value in a variable 'uint8_t x' is 10010011 and you want to bitwise rotate it right by 3 bits (to yield the result 01110010), you need to first derive the partial values [000]10010 and 011[00000], then OR them together.

The right-shift operator '>>3' will create the [000]10010 for us without any extra work.

We can generate the 011[00000] by doing a left shift '<<5' in the same way but with the reverse number of bits (calculated as BIT_WIDTH_OF_TYPE - left_shift_count to get 8 - 3 = 5).

Thus, 'x right-rotated by 3' for an 8-bit unsigned integer can be stated most simply (and inflexibly) in C as (x << 3) | (x >> 5), and the compiler will recognize the "two opposite shifts with a total shift of the variable type width ORed together" and emit a single bitwise rotate instruction (like 'r1 ROR r2') for the actual work rather than "load to r1; rotate r1; load to r2; rotate r2; r2 OR r1." Any unsigned integer can be rotated in the same way. Relevant x86 assembly: https://en.wikibooks.org/wiki/...

Does that help?

Stalin had been trying to get an alliance with Britain and France in 1939

Citations?

Britain and France started WWII by forcing Stalin into a position where he thought he had to make a treaty with Germany

He made it not because he was forced, but because he was planning an attack himself. USSR's entire military posture was offensive — materiel dumps, artillery, bombers were located on the edge of the borders. Which is why they were overtaken by Germans so quickly leaving USSR nearly naked in 1941, when Hitler outplayed his pal. Whether Hitler actually knew of Stalin's designs or not remains subject of debate among historians, but it is quite common knowledge, that Stalin was preparing an attack.

By the time Soviet troops entered Poland, the war was well and truly on (and Poland had lost).

That's not true. Polish troops were retreating to reorganize, when they were attacked from the other direction by the Red Army — to this day Poland refers to the events as "Stab in the Back".

Instead of killing the Poles, Stalin could have helped them — but he and Hitler were allies and thus both share culpability for starting the WW2.

Which is exactly why as a space systems engineer, I'm working on Seed Factories ( http://en.wikibooks.org/wiki/S... ). Fully automated self-replication is hard. Instead, a Seed Factory grows grows from a starter set by three methods rather than one:

* Diversification - making new machines not in the starter set
* Scaling - making different size machines (usually larger), and
* Replication - making exact copies of what you already have

Your starter set allows you to make *some* parts and materials locally. The remainder is imported. As you add more machines, you can do other processes and make other products, and reduce how much you need to import.

Rather than try to make it all automated, you use remote control and *some* live humans where necessary. Thus an asteroid processing plant in near-Lunar orbit, or robots building a Lunar base can mostly be controlled from Earth, with occasional human visitors to fix things. Once you are producing food, water, oxygen, fuel, etc , then you can bring in more permanent occupants. The same goes with Mars. Start with a control station on Phobos, which is close enough for real-time VR. The crew remote control surface robots who prepare the landing site. Once enough equipment is set up down there, humans can follow.

Other people are working on finding asteroids and how to bring them where you need them. That's why I'm working on self-bootstrapping factories. Once you have the raw materials, you have to make useful products out of it. Launching whole industrial plants is too heavy and expensive. So you want to make most of the equipment on-site if you can, out of the materials you are mining.

A properly designed space elevator (see my class notes for details: https://en.wikibooks.org/wiki/... and slides: http://imgur.com/a/cCTY5 ) carries on-board propulsion for orbit makeup. It doesn't look anything like the pictures you usually see in the media, though. The continuous ground-to-GEO concept can't be built, even with carbon nanotube cables. It would be inefficient even if you could build it. More modern designs based on much shorter *rotating* cable systems are more efficient. Even an efficient modern design needs more traffic than we have today to justify the large construction cost.

I recently did a class on space elevator design:

- Class notes: https://en.wikibooks.org/wiki/...

- Slides: http://imgur.com/a/cCTY5

The "classical" space elevator (ground to GEO) can't be built, even with carbon nanotube cable. There are more modern versions that can be built. Realistic engineering designs have to consider a lot of factors that artist's illustrations you most likely have seen don't.

I've been working on a textbook about Space Systems Engineering: http://en.wikibooks.org/wiki/S...

In section 4.9 I do the numbers for orbital mining: https://en.wikibooks.org/wiki/...

The first product of asteroid mining is likely to be rocket fuel. Some asteroids (the carbonaceous type) contain up to 20% water and carbon compounds. This can be processed to Oxygen + Hydrocarbons, which is a common high-thrust rocket fuel. The lifetime mass return ratio of an asteroid tug is ~350:1, and if 20% is usable fuel, then you gain 70:1 just on that one product. Extracting water and carbon compounds only requires kitchen oven level heat, which is easy to do by concentrating sunlight.

There are lots of other products we can potentially extract from asteroids, but that's the easiest and most useful, since most anything you do in space needs some fuel to get where you want to go.

Asteroids did have geological processes, just different ones. The "metallic" type come from protoplanets which melted internally from radioactive decay early in their history. The iron and iron-loving elements sank to the core because they are the densest. Later collisions broke up the protoplanets, exposing their cores. The metallics are a high percentage of iron, nickel, cobalt, and a few other elements. The "stony-irons" come from regions that didn't fully separate the core and rocky layers. They range from low to high percentage iron, with the remainder being rock.

The other process that happened is thermal. Depending how far from the Sun a given asteroid first formed, and later orbit history, certain compounds condensed or not, and then could be baked. Probably the most significant difference is due to the "frost line", the distance at which water ice can remain solid in a vacuum. It happens to be right in the middle of the Asteroid Belt, where Ceres is. Objects beyond that distance tend to have a lot of water. Anything closer tends to have little water, though it can contain "hydrated minerals", where the water is chemically bound.

We actually know quite a bit about the composition of asteroids. Nature delivers samples to Earth in the form of meteorites. We can compare the spectra of meteorites to those from asteroids we get through telescopes, and infer what they are made of. We have flown past or orbited several asteroids, most notably the Dawn mission to Vesta and now Ceres, two of the largest asteroids. Spacecraft carry a larger variety of instruments and can do a better job of telling what the asteroids are made of.

As far as materials processing, we can design machines based on meteorite samples, or simulated samples, since meteorites are rare and valuable. If the Asteroid Redirect Mission that NASA wants to do happens, we would have a sizable boulder to experiment with. After taking science samples, they could try various processing methods on an actual piece of asteroid rock, in zero-g. I don't think we can design serious production units without a a few rounds of trying it on a small scale. For that, we would need at least a small asteroid tug that fetches back chunks from different asteroid types, so we have enough raw materials to experiment on. Most known asteroids are too big to move whole. A 30 meter one is anywhere from 18,000 to 90,000 tons. So for early space mining, we are talking about scraping loose stuff off their surfaces, or grabbing boulders.

my email is the same as my user name here, but lowercase, and add (at)gmail. Feel free to contact me if you want more information. I can point you at sources I have, or send you stuff directly.

I've been working on a textbook about Space Systems Engineering: http://en.wikibooks.org/wiki/S...

In section 4.9 I do the numbers for orbital mining: https://en.wikibooks.org/wiki/...

The first product of asteroid mining is likely to be rocket fuel. Some asteroids (the carbonaceous type) contain up to 20% water and carbon compounds. This can be processed to Oxygen + Hydrocarbons, which is a common high-thrust rocket fuel. The lifetime mass return ratio of an asteroid tug is ~350:1, and if 20% is usable fuel, then you gain 70:1 just on that one product. Extracting water and carbon compounds only requires kitchen oven level heat, which is easy to do by concentrating sunlight.

There are lots of other products we can potentially extract from asteroids, but that's the easiest and most useful, since most anything you do in space needs some fuel to get where you want to go.

Asteroids did have geological processes, just different ones. The "metallic" type come from protoplanets which melted internally from radioactive decay early in their history. The iron and iron-loving elements sank to the core because they are the densest. Later collisions broke up the protoplanets, exposing their cores. The metallics are a high percentage of iron, nickel, cobalt, and a few other elements. The "stony-irons" come from regions that didn't fully separate the core and rocky layers. They range from low to high percentage iron, with the remainder being rock.

The other process that happened is thermal. Depending how far from the Sun a given asteroid first formed, and later orbit history, certain compounds condensed or not, and then could be baked. Probably the most significant difference is due to the "frost line", the distance at which water ice can remain solid in a vacuum. It happens to be right in the middle of the Asteroid Belt, where Ceres is. Objects beyond that distance tend to have a lot of water. Anything closer tends to have little water, though it can contain "hydrated minerals", where the water is chemically bound.

We actually know quite a bit about the composition of asteroids. Nature delivers samples to Earth in the form of meteorites. We can compare the spectra of meteorites to those from asteroids we get through telescopes, and infer what they are made of. We have flown past or orbited several asteroids, most notably the Dawn mission to Vesta and now Ceres, two of the largest asteroids. Spacecraft carry a larger variety of instruments and can do a better job of telling what the asteroids are made of.

As far as materials processing, we can design machines based on meteorite samples, or simulated samples, since meteorites are rare and valuable. If the Asteroid Redirect Mission that NASA wants to do happens, we would have a sizable boulder to experiment with. After taking science samples, they could try various processing methods on an actual piece of asteroid rock, in zero-g. I don't think we can design serious production units without a a few rounds of trying it on a small scale. For that, we would need at least a small asteroid tug that fetches back chunks from different asteroid types, so we have enough raw materials to experiment on. Most known asteroids are too big to move whole. A 30 meter one is anywhere from 18,000 to 90,000 tons. So for early space mining, we are talking about scraping loose stuff off their surfaces, or grabbing boulders.

my email is the same as my user name here, but lowercase, and add (at)gmail. Feel free to contact me if you want more information. I can point you at sources I have, or send you stuff directly.

IAARS (I am a rocket scientist) (see my wikibook if interested: https://en.wikibooks.org/wiki/... )

Beamed power for space launch has been discussed for decades - I have several ring binders of data on the subject. Practical depends a lot on your power storage. Space launch of anything larger than a teacup takes a lot of power. For example, the three liquid engines on the Space Shuttle put out a combined 21 GigaWatts of power, of which 156 MegaWatts was just to run the turbopumps to shove the propellants into the main combustion chamber (the turbopumps had their own combustion system to power themselves).

So this launch system seems to have batteries between the power grid and the microwave generators. That makes sense, because you can't suck GigaWatts on demand off conventional grids. Batteries have been improving in cost and performance pretty well recently, so that may have put it in a practical range. I wonder, though, if on-demand turbogenerators might not be cheaper.

The other parts of the system: heat exchanger, phased array, high power microwave amplifiers, are relatively straightforward, you just need a lot of them. What I wonder about is traffic model. High power launch systems like this cost a lot to build. If you only use them a few times a year, that investment has to spread over relatively few launches. You really want to use them a lot, like daily or hourly. But where is the traffic going to space to fill that much capacity?

It is listed in my space transportation wikibook: https://en.wikibooks.org/wiki/...

All rockets heat a propellant, then expand it from a chamber and nozzle to maximize thrust. Conventional rocket heat the propellant by combustion of the propellant itself. But if you have an external energy source, you can heat it that way instead. In this case, the energy source is a microwave beam, and the propellant is Hydrogen gas. Engines like the SpaceX Merlin have exhaust products of CO2 and water, since their propellents are kerosine and oxygen. These have high molecular weights, much higher than for Hydrogen. Lower molecular weight gases have a higher speed of sound at the same temperature. Therefore their exhaust velocity in a nozzle can be higher, and you get more thrust per kg of gas.

This has been known for a long time, the physics of gas expansion are well known. To make a workable space launcher, you need enough MW of microwave energy, accurate focusing and tracking, and a really efficient and lightweight absorber on the vehicle. Power requirements for space launch are surprisingly large. For example, the Space Shuttle carried three liquid engines, which produced 7 GW of exhaust power each. Something that may have made this concept workable is high power, reasonable cost batteries. Gigawatt power levels are more than most electric grids can deliver. So a way to store it up and release in a short time is very helpful. Traditional rockets did it with very big propellant tanks and enormously powerful (70,000 Horsepower) turbopumps to shove the propellants into the engine fast enough.

Launch to orbit is a high energy proposition. Conventional rockets add 50 kW of kinetic energy to each kilogram of payload for 600 seconds. The Tesla Model S car consumes 20 kW for the whole car at highway speed.

You can't troll someone who spent a career in aerospace, and has written a book on space systems engineering [ http://en.wikibooks.org/wiki/S... ] when it comes to space systems design. You especially can't troll me when you are
an anonymous coward, and I have the same user name here as on Wikibooks, and can thus prove I wrote that book. Now go away, or I
shall taunt you a second time.

In div by zero, why is the zero considered an error? It may be a valid measurement.

I've looked at a bunch of useful formulas, and can't find a single one where replacing ANY variable value with 0 would be wrong.

http://www.infoplease.com/ipa/...
https://en.wikibooks.org/wiki/...
https://quizlet.com/3796199/ph...

I haven't reviewed _all_ formulas, of course, and there might be places in code where disasters (or nonsensical results) might happen. Can anyone give me just one, please?

According to this page outlining GCC's backend mechanism, I can see why it's *slow* at times.

One of my friends told me that tcc compiled a linux kernel in 10 seconds

It has variables, loops, functions, etc.

It has variables, loops, functions, etc.

Elon Musk wants to build a Mars Colony too, but he has a rocket factory (SpaceX), and several other businesses that can earn lots of money *and* supply hardware for Mars: Tesla (electric cars on Earth, electric rovers on Mars), Solar City (home roofs, and soon high efficiency cells for Earth and Mars), and the Gigafactory (batteries for vehicles *and* nighttime backup for solar panels). So his plan is a lot more feasbile than Mars One's.

The real question is where is Mars One going to get the $6 billion they estimate for their project? If they have that money, they can hire the right aerospace companies and engineers to build real hardware. But without it, they just have pretty pictures on a website, and aren't going anywhere.

And as someone who helped build the Space Station, and written a book on Space Systems Engineering ( http://en.wikibooks.org/wiki/S... ), Mars One isn't being innovative *enough* to really bring down costs.

So this is telling me that the apps that Google "Features" currently are not inspected or analyzed by any humans before they become featured. "Featured," to my way of thinking, means recommended. So, currently, are algorithms recommending apps, not people? And if so, how long before algorithms recommend movies, books, music? (Currently, Wikibooks notes that "Featured books are books that the Wiki community believes to be the best . . .")

No. "Apps featured in Google Play" isn't the same as "Featured Apps in Google Play". Neither phrase was from Google, either, but from the summary.

The summary is wrong in others ways, too. It says that Google is going to begin screening apps. The actual announcement says that this has been going on for several months. It also says that the process is "human-based", which the announcement doesn't say, just that the process "involves a team of experts who are responsible for identifying violations of our developer policies earlier in the app lifecycle." This leaves open the possibility that the team in question automates the actual screening, which is obviously much more normal for Google.

Really, your best bet is to ignore the summary and the linked article and just read the post from Google: http://android-developers.blog...

So this is telling me that the apps that Google "Features" currently are not inspected or analyzed by any humans before they become featured. "Featured," to my way of thinking, means recommended. So, currently, are algorithms recommending apps, not people? And if so, how long before algorithms recommend movies, books, music? (Currently, Wikibooks notes that "Featured books are books that the Wiki community believes to be the best . . .")

seriously though, http://en.m.wikibooks.org/wiki... if you had a 'perfect' crystal of metal, such as is common microscopically, the strength of pure metals is around 1000x that of actual samples due to defects. Basically defects pre-stretch the bonds removing most of the needed energy needed to make them slip. Controlling how the defects occur through easy to apply processes is exactly how its possible to easily change the properties.

This way you'll get a feel as to whether there's a hope that they can at least make a start at adapting the right library to your needs. You can even do it with her as the other part of a "pair"; this way, you can discuss the thinking behind her decisions at any point and then maybe discuss other solutions, or how she would attack other problems. You also get a feel as to whether the candidate is a good fit with your other people.

Yeah I never understood that, why try and recover the clock signal from the data stream? If I where designing it I would have my DAC monitor the stream to calculate what the clock signal is supposed to be then generate my own dam clock signal. Let's face it there is only a handful of possible clock signals.

what do you think a CDR (clock data recovery) circuit does...?

> Yeah, I buy it. Hell, I'd work for little more than a pretty meager wage if I could be reasonably sure of ACCOMPLISHING something meaningful in space.

You can, and don't even have to quit your day job. Read up on "self expanding automation" ( http://en.wikibooks.org/wiki/S... ), where a starter kit of machines is used to build parts for more machines, until you have the production capacity you need. In space, instead of sending a whole factory to process asteroids or support a Mars base, you send just the starter kit, and build the rest from local materials. On Earth the same idea of bootstrapping from a starter kit lets you grow your rocket factory or launch site, or any other industrial production you want.

An industrial starter kit will be beyond the average person's finances, but then so is a data center. The way to bring it down to the individual level is (a) to make it distributed - the machines are split up among different people or groups, but they collaborate to make things, or (b) to run a centralized production location on a time share or lease basis. You need a part, you submit the design files and a small payment to have it made. Much of the work becomes designing new or upgraded things to make to expand the system. You can do that at home, because you already have a computer to run the design software.

Once people get the hang of making starter kits and growing them, they can work towards more and more difficult locations. First typical metro areas, then deserts, ice caps, oceans, and finally space. Your first kit, when it is fully grown up, can produce another starter kit for the next location, and so on. You automatically build your supply chain as you go.