Drone defense

Some of the video from Ukraine suggests that drones are getting to be quite effective weapons. If they were quieter, I suspect the criminal cartels would be using them for assassinations already--loiter and attack the witness/judge/competitor.

Some of the videos show them capable of entering shelters through windows or passages. And, of course, they're good at watching for things, whether they have offensive capacity or not.

OK, how do you stop them? You're with your buddies in a truck and hear/spot something headed your way. Shooting won't do much unless you're super-super-accurate. Net guns... they look nice, but I wonder how practical those are in the field. Hide behind trees...

Pros and amateurs try their hands at downing drones in this video (which has a very annoying long commercial in the middle). Some of the methods are more amusing than useful.

One of the methods tried is the vortex ring cannon, which can pack more of a punch than you might expect. For sufficiently large vortex cannons, of course. Of course, you could also try using guns adapted (with blanks) for the purpose. The article cited talks about "knock-down effect" on humans (mediocre), but it might be suitable for trying to knock down lighter flying objects.

Copter-type drones are somewhat at risk for vortex ring state, where instead of pushing the air down the propellers push air down and around and up and back through the blades again, in a "circle" that doesn't provide lift. The article explains how designers have been mitigating this. However, if a strong vortex ring hits a quadcopter, it should provide some impact, some twisting, and maybe cause one or more of the propellers to get into VortexRingState.

If the equipment is just an adapter on the end of your rifle (and maybe blank rounds, maybe not), it might be easy to carry, cheap(*), and relatively quick to field. The vortex ring is a lot bigger than a rifle bullet, so your chances of hitting are better.

There are obvious possible issues--would it destabilize the drone enough with an average hit? would the ring move fast enough to reliably hit a moving target (80 m/sec??? with my sloppy estimates for vorticity)? and can soldiers/civilians aim well enough, especially at night? Oh, and is the effective range good enough?

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(*) "Cheap" would probably be the kiss of death, unfortunately.

UPDATE: I found an Army report. The Wikipedia image of the vortex ring was out of a 40mm barrel, and they developed 100kpsi in their chamber, using a "rupture disk" to get the cleanest possible flow. They did not design the test system for rapid fire. So this probably wouldn't be a snap-on, but a separate (hopefully light) blunderbuss. They found that C4 wasn't great--the ring momentum was low--so they converged on "exotic" explosives like Red Dot and Bulls Eye (up to 30g). They were getting about 160'/sec.

Their aim, so to speak, was attacking humans, who are typically less fragile than drones in flight. The idea might work. I assume that with lower pressures the final velocity would be proportionately lower, but fluid dynamics is messy.

0 G

We wondered what could be different about dance in 0-G. You don't get more than about 90 seconds for a routine (I don't think the space station has room, or priority), and you'd have to practice in water, which has very different viscosity from air.

Of course whatever we wonder about, somebody else has already tried.

Eventually dancers will want to use fans for maneuvering, especially for non-solo routines. This looks fun (aside from the racket), but not a lot like dance.

Passing time better left unpassed

Our eldest was given a Dr. Who Exploding Tardis jigsaw puzzle. Do I need to say that it is not complete yet? When I went to look up an illustration for the post, I changed my mind about the subject and started to rejoice that it wasn't "The Lines" or a solid color one.

I've heard of an abstract puzzle that included extra peices, of ones that didn't include edge peices--were there double-sided jigsaw puzzles with pictures on both sides? Yes.

I don't start jigsaw puzzles myself, but if one is already out it tends to exert a diabolical fascination...

FWIW, Prado Museum has a collection. If you want to put together the Garden of Earthly Delights...

Fresnel X-rays

You've all seen an ordinary magnifying glass--it looks like a section of a glass sphere, maybe flat on one side, or maybe with both sides curved. Since all the bending of light happens at the surface, what happens if you cut out the excess and just use hundreds or thousands of little (disjoint) sections? Augustin-Jean Fresnel thought of it, and developed the lenses that bear his name. His thought was for lighthouses to be more powerful by capturing and focussing more of the light, and it worked very well. There's graininess in the image you get when using these things, but that's the price you pay for compactness.

How do you focus X-rays? They can be scattered in coherent ways by crystals--suppose you used little slices of crystals tilted at increasing angles and stacked in rings?

Turns out somebody else thought of the idea first. The Laue lens uses crystals in concentric rings. You can get pretty decent focus, too: 8.4nm × 6.8nm .

Reading in bed

Someone described the condition of a friend in the hospital as being not even able to read. That brought the following to mind. Unfortunately he is not in good shape. Maintaining concentration is probably impossible when he'd not in the induced coma, so the following would be useless for him.

When you're flat on your back after (e.g. shoulder) surgery and you'd like to do something more than watch the boob tube, it is frustrating to realize you can't hold a book in position. E-books might change that.

There are several possibilities. You can mount a flatscreen monitor on the ceiling, and use a tablet at your hand with some kind of bluetooth interface to the monitor pickup, which would then control the monitor. This would allow other things besides just books, of course. You could fumble through your email, browse the web, or setup your own boob tube feed. However, room lighting might make it less than ideal. Room lighting (and the greater expense!) make projection on a screen on the ceiling even less attractive.

It would be easier to mount a swing-arm type of holder (with stiff springs!) to the headboard, for your e-reader or tablet. If you can lift your arm, it should be fairly easy to control. If you can't, a tablet should be within easy bluetooth range of a corresponding device you could have at your side. You'd need help with the orientation in that case, but since you'd probably also need help getting out of bed that's likely available.

Yep

Wii conductor

Suppose you recorded an orchestra, carefully separating the instrument classes: brasses, strings, etc., and then used a Wii (together with a fairly nice sound system) to mix the streams using instrumented gloves as the control. You give the beat, and the sound streams run fast or slow according to your beat. Gesture at the image of the brass section for a little more brass, and that gets amplified in the mix. Stretch out a phrase... if there's a standardized gesture for it you could program it.

Pausing and restarting from some defined time points have to be integrated into the system somehow, and you need a set of different symphonies to play with, but it would seem possible that a Wii could be used for "Conductor Hero." It might not have the horsepower itself, and a bolt-on sound mixing processor might be a bit pricy--I don't have the intimate knowledge of the hardware needed to guess.

This is similar to, but a little more complex than, Wii Maestro, which I just learned about after googling to see if any was already doing this already. It doesn't seem to do any mixing, just speed and volume control, though that's quite a bit. Maybe the next release...