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I think the idea is that you wouldn't need this kind of refrigerator with a drone. Instead the drone would be dispatched the moment the next batch of children n

I think the idea is that you wouldn't need this kind of refrigerator with a drone. Instead the drone would be dispatched the moment the next batch of children need to be vaccinated. This is ideal because you don't need a heavy, expensive refrigeration unit to keep vaccines cool for days of travel, thus decreasing the cost and expense of vaccination. Obviously this won't work everywhere; extreme weather, like storms or even high winds, may make drone delivery impossible for much of the year. But it appears that the more we can deliver vaccines by drone, the better.

namibj 8y ago
There are ways to fly reasonably fast with rather cheap technology, if you have some way of bringing the fixed-wing aircraft up to at least over about half the speed of sound. This would e.g. be easy to archive if you use something like a coaxial folding propeller, though if you try, you could probably get away with a single folding propeller, or at least without needing the coaxial nature to provide counter-rotation, as a large enough part of the wings should be outside of the whirl the prop creates, so it can provide enough force against the prop to keep the plane spinning relatively slowly. The technology I'm referring to (a ramjet) is unfortunately not too efficient, but the low-tech nature of it, at least as far as manufacture is concerned (design benefits greatly from modern computational fluid dynamics), makes the manufacturing cost of it, including a fuel tank, come in at about 10-100$. It's basically a fancy shaped pipe with something like a fuel pipe or so coiled around it (for cooling and to ensure sufficient temperature of the fuel), which can just be hydroformed from a seamless section of stainless steel pipe. They guzzle fuel, but as long as you either have an electronic valve a microcontroller can adapt to e.g. a simple flow meter or pressure sensor, along with a temperature probe, they only need the fuel to contain enough butane/propane or so to self-pressurize, and otherwise require the fuel to not tar/char/soot up any of the fuel nozzles and such. Theoretically, though one might prefer to run it on liquid hydrogen in that case, the same technology, but with different tuning could run a similarly rather cheap Mach 2~3 (at surface level) reaching thing light enough to be lifted by a pair of movers or similarly build men. That would be hard to do without going for the hydrogen, and that is unlikely to be prevalent on a small pacific island. Both of these potential things do fall under the category "Your scientists were so preoccupied with whether or not they could they didn't stop to think if they should.", the latter even under the category "ITAR want's to have a word with what you made there.", due to the necessary automatic navigation and speed, as well as technological level of materials used, as high-tech airframes are expensive.
- me_again 8y ago
  That sounds very interesting and cool. But the lower-tech approach in the original article sounds radically more practical in real terms than either drones or liquid-hydrogen-powered ramjets ;-)
  - namibj 8y ago
    This was the general medicine-remote-island-delivery approach ;). The LH2 ramjet could probably be made to launch from a <100m long catapult, I once did a few calculations and UHMWPE fibers should allow accelerating within iirc. 50m to Mach 0.7 with something like a large (half-ton, due to the energy density) steel coil spring (like in a watch, just a "little" larger) at the muzzle and that coiling up the rope pulling an iirc. 100 kg aircraft with a sled or so, due to the ramjet not delivering enough thrust at lower speeds. The side effect would be that because they gain thrust with speed (up to a point, for the LH2 constellation somewhere over Mach 3), there would be plenty of thrust to spare, and combined with the high structural strength necessary for the catapult, and the lack of vertebrae on board, turns up to about 30~50 G are feasible, all at near ground level. While there is certainly an appeal to this, and the technology being sufficiently low-tech for a home shop (I am just going to refer to Sam Zeloof's garage wafer fab), any attempts at building something like it as a large hobby project would be futile for there being no way to test it outside of a remote desert area or the ocean, both rather inhospitable to a one-man flight crew. There are reasons supersonic aircraft are not tested over inhabitation. It would not be nice to a street it could technically fly through, unless the buildings are already blast proof. And a hobby project of that scale you can't even play with will not be worth it. (If you happen to know how to play with something like this despite the supersonic-over-land ban, please divulge your secret.)

namibj 8y ago

There are ways to fly reasonably fast with rather cheap technology, if you have some way of bringing the fixed-wing aircraft up to at least over about half the speed of sound. This would e.g. be easy to archive if you use something like a coaxial folding propeller, though if you try, you could probably get away with a single folding propeller, or at least without needing the coaxial nature to provide counter-rotation, as a large enough part of the wings should be outside of the whirl the prop creates, so it can provide enough force against the prop to keep the plane spinning relatively slowly. The technology I'm referring to (a ramjet) is unfortunately not too efficient, but the low-tech nature of it, at least as far as manufacture is concerned (design benefits greatly from modern computational fluid dynamics), makes the manufacturing cost of it, including a fuel tank, come in at about 10-100$. It's basically a fancy shaped pipe with something like a fuel pipe or so coiled around it (for cooling and to ensure sufficient temperature of the fuel), which can just be hydroformed from a seamless section of stainless steel pipe. They guzzle fuel, but as long as you either have an electronic valve a microcontroller can adapt to e.g. a simple flow meter or pressure sensor, along with a temperature probe, they only need the fuel to contain enough butane/propane or so to self-pressurize, and otherwise require the fuel to not tar/char/soot up any of the fuel nozzles and such. Theoretically, though one might prefer to run it on liquid hydrogen in that case, the same technology, but with different tuning could run a similarly rather cheap Mach 2~3 (at surface level) reaching thing light enough to be lifted by a pair of movers or similarly build men. That would be hard to do without going for the hydrogen, and that is unlikely to be prevalent on a small pacific island. Both of these potential things do fall under the category "Your scientists were so preoccupied with whether or not they could they didn't stop to think if they should.", the latter even under the category "ITAR want's to have a word with what you made there.", due to the necessary automatic navigation and speed, as well as technological level of materials used, as high-tech airframes are expensive.

me_again 8y ago
That sounds very interesting and cool. But the lower-tech approach in the original article sounds radically more practical in real terms than either drones or liquid-hydrogen-powered ramjets ;-)
- namibj 8y ago
  This was the general medicine-remote-island-delivery approach ;). The LH2 ramjet could probably be made to launch from a <100m long catapult, I once did a few calculations and UHMWPE fibers should allow accelerating within iirc. 50m to Mach 0.7 with something like a large (half-ton, due to the energy density) steel coil spring (like in a watch, just a "little" larger) at the muzzle and that coiling up the rope pulling an iirc. 100 kg aircraft with a sled or so, due to the ramjet not delivering enough thrust at lower speeds. The side effect would be that because they gain thrust with speed (up to a point, for the LH2 constellation somewhere over Mach 3), there would be plenty of thrust to spare, and combined with the high structural strength necessary for the catapult, and the lack of vertebrae on board, turns up to about 30~50 G are feasible, all at near ground level. While there is certainly an appeal to this, and the technology being sufficiently low-tech for a home shop (I am just going to refer to Sam Zeloof's garage wafer fab), any attempts at building something like it as a large hobby project would be futile for there being no way to test it outside of a remote desert area or the ocean, both rather inhospitable to a one-man flight crew. There are reasons supersonic aircraft are not tested over inhabitation. It would not be nice to a street it could technically fly through, unless the buildings are already blast proof. And a hobby project of that scale you can't even play with will not be worth it. (If you happen to know how to play with something like this despite the supersonic-over-land ban, please divulge your secret.)