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!).

The Moon has no resources we don't have on Earth, however, it has them 'cheaper.'

Building a large structure in space like an orbital resort or a solar power satellite from materials sent from Earth would be impractically expensive. However, if one gets this material from the Moon, these sorts of structures become a lot more practical.

It is a lot less energetically intensive to launch a kilogram of something from the Moon(hard vacuum, low gravity) than it is to launch a kilogram of something from the Earth(air, high gravity). Just compare the Apollo Lunar Lander to a Proton rocket bound for the International Space Station.

Now as for mining the Moon as opposed to asteroids:
1. asteroids are typically quite a bit farther out than the Moon
2. the lunar environment is fairly well characterized: we have 382 kg of near pristine samples of lunar material, while we have only micrograms of samples of asteroidal material.
3.we know how to mine stuff in gravity, we currently do not know how to mine stuff in microgravity

Only problem is that the Moon lacks large amounts of water and carrying said water to the Moon would be energetically costly.

Making something dust tight in a vacuum environment can't be all that hard. We have standards for preventing dust intrusion and they aren't all that different from standards for preventing water intrusion.

And we do have a way to clean dust off equipment in a hard vacuum. Moon dust easily picks up an electrostatic charge, allowing one to use an alternating electric field to remove regolith from solar panels.

The same technology, shouldn't be all that hard to integrate into space suits or other equipment.

Robonaut's legs are designed for walking around the space station in microgravity, so they would be useless in gravity

BUT, the same people working on robonaut are building a female humanoid robot for the DARPA robotics challenge, which could very well walk on the moon

Robonaut's legs are designed for walking around the space station in microgravity, so they would be useless in gravity

BUT, the same people working on robonaut are building a female humanoid robot for the DARPA robotics challenge, which could very well walk on the moon

Except that hydrogen can do some [a href="http://en.wikipedia.org/wiki/Hydrogen_damage#Shatter_cracks.2C_flakes.2C_fish-eyes_and_micro_perforations"]rather nasty things to metals[/a].

Although, hard drives don't get very hot or experience high stresses, so it might not effect it.