Shpaget

The image says it's an engine.

True enough, even gold rings have claimed a few fingers, for example: https://en.m.wikipedia.org/wiki/Ivan_Čupić Which raises the question, why take the risk at all? Anyway, you obviously want something shiny and blingy. Steel will keep the shine longest.

The prospect of snagging the ring on something and losing a finger does not worry you?

Very quickly and in a hurry, since every piece of equipment we've ever sent down there went kaput in matter of hours.

For orbital parameters you need position and velocity.

Just because they have access to the final product, it doesn't mean they know how to reproduce it. Sure, they can mimic the shape, but the material properties are a whole lot harder to reproduce, even if they know the composition. Just take steel for example, heating and cooling regimes play a major part in its production, yet are not obvious in the final product.

That's not how 3D printing works. You can't just have some all purpose goo that turns into whatever material you want. Not only such a goo doesn't exists, but different materials require different 3D printing processes, and most meterials used in our products can't be 3D printed at all. Take any man made item around you and count the different materials in it. Furthermore, making a product usually does not involve just the shaping. More often than not there are additional steps that need to be done. For example, some steel parts need to be quenched and then tempered. Others have to be forged. Those processes were developed because there is a genuine need for the properties they introduce into the material. Glass products require their own production processes. Electronic components, such as microcontrollers and CPUs require huge production facilities. You can't just walk up to a 3D printer and ask it to be a Star Trek replicator.

You can clearly see the layers on the casing and the bolt for what he calls the louvres. That abysmal surface finish is never going to be good enough for bearings in a turbocharger and I'm quite doubtful it can produce a good turbine. For mass production? It is likely not going to change. Injection moulding is exceptionally cheap once you have the tools and produces great results, so for large production runs it is the way to go. It is so popular it is everywhere. Every product that contains something plastic is likely to have injection moulded parts in it.

He prints casings for turbochargers Anyway, this is what it takes to make an injection moulded item. I'd say there has to be a very good reason they go through all that effort - superior quality. The video is in German, but the picture should be enough.

Yes, 3D printers can make nifty parts, but they are still mostly toys. Sure, they can make an intricate thing like this: but mechanical properties of it are very poor. After all, it's plastic. There are printers that use metal, but the material of the finished product is still inferior to other cheaper manufacturing methods. 3D printing is and, I suspect, always will be more expensive and of inferior quality than countless methods of mass production. That being said, they are great for one offs, prototypes, concepts etc. It's great to be able to design a product and print out its enclosure in matter of hours for a low cost, adjust the design and print it again and again until you have ironed out all the issues. With standard manufacturing methods, such as injection moulding, producing multiple tools for testing and prototyping would be prohibitively expensive, however, once you 3D print your final design and decide it's ready for production, you will go back to injection moulding. As for printing sensors and other devices you mention, no that will not happen. Not only are 3D printers incapable of such intricacies and material variation, the instruments need calibration, testing, verification etc... Even if you could print bimetallic switches, they would be inconsistent and useless.

Seems peaceful enough.

They are a peaceful species. They don't fight.

Ok, so I got around to take some photos. Here are some details about it. The camera used was Canon 40D, mounted on a tripod, with 10 second shutter delay and mirror lockup, all in an effort to eliminate the camera shake. I would say the camera was sufficiently stable and not moving. The lens under test is Samyang 800mm f8 mirror lens. It is a manual focus, fixed aperture. It is Cassegrain, Maksutov or similar design. It's hard to tell and impossible to find in specs. In any case the primary mirror is about 10 cm in diameter. For comparison I used a Canon 100mm f/2,8 macro, a refractor, obviously. Just for comparison, the Canon lens is about 2,5 times more expensive. Since it is -2°C outside, I left the camera and both lenses outside for a bit more than an hour so they can cool down. Perhaps some of you may appreciate that. Anyway, here are the photos. The building is about 150-200 meters away. First, the Canon 100 mm f/2,8 macro. ISO 100 f/6,3 1/80s The insert is 100% zoom. Next, it's Samyang ISO 100 f/8 1/80s As you can see there is an awful lot of fuzziness and even some ghosting. This is not zoomed in. That's straight out of camera, just resized for sanity. Next I artificially stepped down the lens. You basically make a small hole in an opaque material which you place over the lens. It's not possible to measure the aperture very accurately, but we can make some conclusions based on other parameters. In this case the effective aperture was reduced to approximately f/20. ISO 100 f/20 1/10s Again, the insert is 100% zoom. There is significant difference between wide open and stepped down Samyang. Much more detail is visible in the third photo than in the second, but the overall sharpness is still much lower than on the Canon. Perhaps if the Canon lens was mounted on a camera with higher resolution sensor, the image would contain even more detail. I can't be sure, I don't have such a camera, but it's clear that the Samyang has reached it's potential on this old sensor and that it would benefit very little from an increased sensor resolution. Yes, the (stepped down) Samyang offers more information, but it's far from good. Of course, this test speaks more about this particular Samyang lens than about good reflector telescopes in general. A small (10cm) space based telescope would without a doubt have significantly better optics than this lens, but it would never be comparable to larger ones, which was the starting point of this topic.

Sure we need more space sensors, but they should be pointed up, not down. I used to frequent space.com, but then they decided to just shut down the forums without notice or explanation. Now they deal with fearmongering. SDC, going downhill since 2011.

You need much, much better accuracy and precission for optical telescope interferometry.

I'm not offended. I'm well aware that it's a poor quality lens. After all, you get what you pay for, and right at the beginning I said it was a cheap lens.

Sure, there are poor manufacturers and better ones, however, there are no excellent mirror lenses. Perhaps my particular one is poorer than usual, or just it's a matter of opinion. Perhaps what is crap for me is acceptable to somebody else. In any case, I forgot to bring my camera home, so I can't shoot some comparison photos. Will report back.

I have one of those. Samyang 800 mm f8 It's really light, long focal distance and rather cheap, but optically useless. I ended up mounting an exterior stepper motor for focusing with optical sensors so I don't need to touch anything to focus, but still couldn't get good image. Yes I did get a few more details than with my 100 mm macro lens, but the macro is so much better all around. I don't have my camera with me ATM, it's at my workplace, but if you guys want, I can shoot some pictures with it later today.

I was about to say that it's pretty much exactly all down to mirror size, but then @kerbiloid ninja'd me by linking to diffraction limited system wiki entry. We've had the technical capability for building diffraction limited telescopes for quite a while; Hubble being the famous one, but definitely not the first one. Its mirror has been polished to about 10 nanometer accuracy, which should be a good enough argument for discarding any proposition for inflatable mirrors. Just to explain what diffraction limited system is, it's the maximum theoretical resolution an optical system can achieve, and it is directly linked to the size of the primary mirror. Bigger mirror means better image. It's not just light gathering capabilities (although that's a nice bonus). So, a good 10 cm mirror in orbit would make a good telescope, but not a spectacular one. It would be outperformed by many ground based handmade mirrors of larger diameter.

I used to play that on my mom's computer at work. A couple of decades later, I still haven't figured out how to not get eaten.

Most likely not the first one I played (that would probably be some type of Pong), but one of the first games I clearly remember playing and having a great time was Ugh!. It's still a great game.

Exactly. A tsunami is not just a big wave. It's a specific type of wave that behaves differently than those formed by wind or rock splashes (regardless of the size of the rock).

Wouldn't they keep on falling on their noses? It is far to small wheel. Coriolis would have them barf in no time.

I'll have to go with the @5thHorseman and his reasoning. Also, I must agree with @LordFerret. @LN400, while your method brings us to the same conclusion, is that a valid approach to solving this type of riddles? It seems like a fluke it worked here.

Occasionally, I shoot wedding and corporate videos and the company I gig for has DJI Phantom 4 (and used Phantom 3 previously). Couple of months ago we were shooting windmills and the wind was quite strong, so strong in fact that we were a bit anxious to tak of with the Phantom 4. Long story short and a few extra steps back in case of a crash we took off. The drone shot up and stayed hovering about 3 m off the ground in such a strong crosswind that the drone had to keep about 10-15° angle just to keep still and compensate. The video from it was as smooth as it gets, though. The station keeping was completely automatic. Quite amazing actually what modern electronics can achieve in such a small package and for relatively small cost. Just a few years ago, such stability was not possible without huge and heavy gyros, stuff bordering on military tech. Cameras small enough to be flown on RC planes and copters were poor quality and gimbals had no stabilisation, making the video all shaky and next to useless. As for drone vs quadcopter/multirotor, for me a drone is at least partially autonomous, regardless of the configuration. It can be a plane, a helicopter, quadcopter or a submarine, it doesn't matter. Quadcopter is a flying device that uses four propellers to generate lift. It can be a drone, but it doesn't have to. The truth is that most quadcopters, even the cheap Chinese ones, have some degree of automation, even if only for stability or flip tricks. On another, completely unrelated note, I just accidentally discovered/realized that if you press Ctrl + left/right arrow key, the cursor jumps to the beginning/end of the previous/next word. Amazing!