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The problem of find an object siting on the bottom of the ocean is different from finding an object actively propelling itself through the ocean.

One possible method of detecting submarines is looking at the wake they produce. As submarines move through the water they leave an underwater wake that slightly modifies the wave pattern at the surface. One can use radar or lidar along with a bunch of computing power to detect these wakes and thus reveal submarines. Implementing such a system could be done relatively cheaply by mounting such systems on a UAV. Submarines have allegedly been detected from SAR satellites.

Acoustic cancellation is no countermeasure for this, one would have to find a way for the submarine to be propelled without making a wake, which is possible, but probably not practical. Although this detection technique does not work well when there are a lot of breaking waves.

The printer does not spray "drops of thermoplastic," it sprays magic chemicals that either inhibit or promote sintering onto a bed of thermoplastic powder and then uses a big o' incandescent bulb to fuse the powder. This is pretty much the selective inhibition of sintering process, so the magic chemicals are probably just something like salt water and black ink.

Now what does this mean? Well because you have to spray a sintering inhibitor on, you can't recycle as much powder, unless they give you a special powder recycler for removing the inhibitor. Because you're printing out lots of black ink, can't really recycle powder, and HP will lock you into using their cartridges you will be paying out the a$$ for ink and 'toner.'

This is a HUGE development though. If the parts really have the same strength and detailing as those produced with laser sintering, as in even if this machine did not come equipped with color capability, then this has just made a lot of big industrial 3d printers obsolete. Getting rid of the need for laser and nitrogen gas purge system for sintering type machines is HUGE! Even with huge expensive print cartridges it's going to be cost competitive with everything out there.

Heck, it probably makes the whole 3d printing service bureau business model obsolete, because this puts high quality 3d printers in the cost range for small businesses.

This is probably the "attack of the killer micros" moment for the additive manufacturing industry.

Why not do something like the Rosetta Projectand etch all the pages on to a mass produced metal disk?

And if you don't limit yourself to the requirement that the text be optically readable, you could make 'Feynman's Library,' use modern semiconductor lithography processes to etch the entire library of congress onto something the size of a library card(and in some sturdy material that ).

For the most part we have the technology to do this, the only big difficulty with doing such a thing(aside from scanning all the books!) would be getting liscensing to 'print' all the books in the library of congress.

While the outer space treaty prohibits countries from claiming celestial bodies as their own, Article VIII states that a country "shall retain jurisdiction and control over such object, and over any personnel thereof, while in outer space or on a celestial body. Ownership of objects launched into outer space, including objects landed or CONSTRUCTED on a celestial body, and of their component parts, is not affected by their presence in outer space or on a celestial body or by their return to the Earth."

Which means that if one might be able to claim an asteroid by by bolting a spacecraft to an the asteroid and stating that the asteroid is now a spacecraft part that was constructed when holes were drilled into the asteroid.

A while back DARPA had the Adaptive Vehicle Make(AVM) project which was to combat the exponentially growing cost of military hardware development by implementing an opensource hardware hackerspace/fablab style model(with more buzzwords than I desire to recall).

Part of this project was MENTOR(another huge acronym), which was going to set up schools with their own makerspaces and have students "compete against one another in the development of cyber-electro-mechanical systems of moderate complexity such as go carts, mobile robots, small unmanned aircraft, etc."

However, the official goal of the program really was to "to teach the principles of model-based design and distributed foundry-style manufacturing to build a next-generation cadre of manufacturing innovators."

Which is a laudable goal and probably does more to defend our country than designing a new tank or fighter jet.

And honestly, how awesome would it be to bring back shop class and modernize it?

Unfortunately, it was never moved beyond a pilot program when AVM got cancelled for it being redundant with Obama's manufacturing initiative.

The big reason why pneumatics aren't used as much in robotics is that air is very compressible, which leads to all sorts of nastiness when you make pneumatic actuators.

Because air is compressible, compressing air is not very efficient compared to say hydraulics. This is bad for exoskeletons.

The other problem is that the compressibility of air limits the 'bandwidth,' or how fast these actuators can actuate and un-actuate controllably, achievable with these actuators. In addition, the bandwidth of pneumatic actuators is often below the frequency of human walking, making them impractical most exoskeleton applications.

And of course, there's more to it than compressibility at play here that could make these actuators impractical. Since these actuators use a rubber membrane, these actuators are subject to hysteresis, significant temperature effects, and creep.

Rubber, when stretched and unstretched quickly, heats up causing the rubber to change it's stiffness. In addition, the temperature of the rubber can also change due the air being pumped into them. Rubber, and other elastomers, also experiences a phenomenon known as creep, where it slowly stretches out with time. In fact, current industrial pneumatic muscles NEVER actuate exactly the same because of all this, and one has to use interesting control approaches.

I am also skeptical that this will be cheaper in practice than mass produced electric actuators. While the actuators themselves are cheap, the valves and other hardware necessary to control them are not. The actuators themselves will certainly wear out sooner than electric actuators(>10 years continuous operation for robot arm actuators) due to the creep mentioned above. With lower efficiency and increased maintenance costs the overall cost of using these could very well be higher.

In fact, the brushless motor in the compressor they show in the video probably can provide" 25% of the power of a normal human elbow," and the only reason it can't be used on a human elbow is that much of that power is at high-speed with low torque. If someone were to develop a compact and efficient gearbox for turning high speed- low torque into low speed-high torque, then one could mass produce it and skip all the pneumatic silliness.(Or just do what that company that robotics google just bought did and use watercooling/overclocking)

Well technically 3D printing refers to the process of using an inkjet, the very same inkjet from a regular printer, to deposit a binder on a layer of powder. 3D printing is just one Additive Manufacturing process.

Now DMLS and Laser Sintering(SLS is a trademark of a particular company) aren't quite yet ready for consumers yet.

Laser sintering of plastic requires inert gas, messy plastic powder, and messes up if temperature varies even a tiny bit(sintering scales with T^4). Messy doesn't even begin to describe how dirty these machines are. You can almost taste the powder in the air near these machines.

DMLS uses explosive metal powder, requires inert gas, and a pretty dangerous laser. But the real kicker to DMLS that makes it ill suited for the consumer market is the support removal. In order to prevent the printed parts from deforming and to dissipate heat, one has to print supports in. In other words, after printing you have to go in and do a bunch of sanding and dremeling to remove METAL supports from the part!

LOM is pretty much just for making stuff out of paper, so one probably wouldn't be able to make a very good gun with it.

SLA can really only do plastics and ceramics. And doing ceramics requires a special kiln.

However, SLA might be coming to the consumer market due to it's simplicity, speed(there's indications these machines could print very fast), and resolution.

The technology will improve, BUT fabbers capable of actually printing a working uzi aren't likely to be something everyone would have in their home.

Plastic is not a good material for making firearms, especially 3d printed plastic, which currently has worse mechanical properties than injection molding.

Sure 3d printers can print metal and ceramics, but they are not something every normal person would want in their home. They either require explosive metal powder, large amounts of power, a precision kiln, or inert gases.

This is much the same with CNC machines today, most people don't have a big CNC machine in their garage, aside from the fact they're expensive, they're messy!

Since they have found these guns are completely useless, then hopefully they won't enact legislation to require all 3d printers have crippling DRM that makes it impossible to print guns.

Or maybe they might, but given that they now have a government study that say these guns are useless, it's gonna be a lot harder(I hope) for scare-mongering politicians to cripple or ban 3d printing

This ignores the point of concept cars. Those solar panels aren't generating power so much as hype.

So the question we all want to know is can this actually happen?

Will a bird/cat/rodent be fried when they enter the beam?

Well we know the car roof has an area of 1.5 square meters and the lens provides 10 times the energy that would fall on the car roof. Using standard insolation of 1000 watts/m^2, we can deduce that the solar radiation flux on the car after the lens is 10000 watts/m^2.

So is this enough to fry a cat? The answer is.... yes, but it wouldn't happen instantly! According to wolfram alpha 10000 watts/m^2 is 10 times the radiation flux necessary to cause harm to biological tissue!

This is also in the range to singe holes in black pieces of paper!

Worst case, our poor puddy cat will probably make it out with some singed fur, but should otherwise be all right!

First, those pennies aren't made of nickel, they're made of copper coated zinc.

Second, pennies don't melt when exposed to a fresnel lens of that size, they VAPORIZE! Or at least the zinc does anyway

Well, we have plenty of technologies for dealing with highly abrasive materials and operating in highly abrasive environments.

Take for instance the concrete pump, it's a device that moves a slurry of fine(and many times not so fine) particles at high rates of speed with a decent MTBF.

We have cars, trucks, and mining equipment that can operate with a decent MTBF in abrasive and sandy environments

We have helicopters that have to deal with operation in sand environments, where blades and other fast moving components essentially get sand blasted!

And there has been some recent work on lunar regolith tolerant connectors.

Now the bigger issue that we have isn't that the dust is abrasive, but that we can't model how the dust behaves! Granular materials like lunar regolith do not have scaling laws. Thus, we can't make small scale 'wind tunnel tests' on systems that handle granular materials, the only way to test is at full scale.

So when someone wants to build a new type of concrete plant, they test it out at near full scale and tweak it until it works, because we have no good way to computationally model it before hand. And even then, most concrete plants and other systems that handle granular materials do not work very well. They tend to experience jams and other problems which must be fixed with regular maintenance.

And we don't know why they jam or even in some cases why they work in the first place!

Thus we'd have trouble building a 'concrete plant' on the Moon without impractically large expenses, because we don't understand dust.

The solar proton flux is really, really, really, really low, even during a solar flare! We're talking 10s of protons per square centimeter at best here.

That is not a lot of water. 600 million cubic meters is roughly the volume of Sydney harbor. In human terms, this is certainly quite a bit of water, however, this water is spread out over a very large area. This makes getting sufficient amounts of water difficult, especially in cold, shadowed craters(no solar power!).