Imagine with me a solution for getting a large payload into orbit.
Traditionally, we use multi-stage rockets that carry all their fuel from sea level to orbit and beyond. For going from ground to orbit, at least 90% of the weight of the rocket must be fuel. The remaining 10% can be structure. A smaller percentage of this can be payload. In the case of the Apollo missions, "payload" can be considered the weight of the astronauts, camera film, and a bag of moon rocks. Everything else- including the reentry vehicle, was technically disposable. To double the final payload would likely require doubling the initial size of the rocket.
A technically more elegant solution is to use a multi-stage, reusable system. The space shuttle, which only visits low earth orbit, has a much higher payload percentage.
SpaceShipOne, built by Burt Rutan to visit the lowest definition of "space" (about 60 miles) uses a combination of air-breathing jet engines and rockets. Different parts of the system land separately.
So, for the fun of it, I'm thinking about another way to do something similar. Only, in this case, we're going higher than the 53k feet that an air-breathing engine can handle.
Let's say that we need to get 250 miles high to achieve a reasonable, stable orbit. Let's say that we'll be getting there via rocket. Let's be generous and say that the mothership model (ie, WhiteKnight) gets you 10 miles high. That's 4% of the total distance. Aside from the advantage of not having to drill through the dense lower atmosphere while simultaneously gaining the necessary momentum to continue onward to escape velocity, this translates to only a marginal total advantage. The higher your target orbit, the less your advantage.
So, I propose that we get even higher. StratoLab V, a high altitude testbed from the early 1960s, still holds the world record for highest manned balloon ascent. Over 113k feet. Unmanned balloons have reached as high as 173,900 feet- more than half-way to the hard edge of space.
Imagine building a balloon that can lift a two-stage rocket powered shuttle glider as payload to about 80k feet. The shuttle would sit in a cradle, dangling beneath the balloon, and take off at an angle away from the balloon straight overhead. The balloon would achieve non-trivial speed using high altitude winds which would be added to the rocket's total lateral velocity. The balloon, which would likely be manned, would then be piloted to the ground by releasing billions of cubic feet of hydrogen.
In the event of an emergency, balloon crew would parachute to safety wearing pressurized suits. The shuttle would glide to safety. Crew would come down separately on parachutes and the shuttle would be flown remotely. If necessary, it would jettison its fuel and make a water landing. Otherwise, it would operate as designed, making a dead-stick landing at an airstrip. Its payload would be recovered and reused.
Alternately, instead of a shuttle, a two-stage, bare bones rocket would be used. Because of the high altitude, it would not even need to be particularly aerodynamic. The payload could be partially or even completely exposed to the open air.
After landing, the balloon would be deflated, disassembled, placed on trucks, and returned to base for refurbishment and reuse. Helium might be used as a buffer gas- for instance, providing a thin layer- held in place by ultra-thin polyethelene- to diminish the exposure of hydrogen to static charges on the balloon's surface. Because the helium would represent a small amount of the total gas volume, but would be enough to keep the gas envelope up (rather than raking against the ground during landing), this helium could be carried all the way back to earth and then be recovered, purified, and reused.
How big would this balloon be?
Let's imagine that we want to achieve 50k lbs of delivery to low earth orbit- similar to the Space Shuttle.
Let's estimate that the total advantage, over the traditional space shuttle, is about 40%. two-thirds of the advantage comes from being able to bypass the lower atmosphere's drag. The remaining one-third comes from a combination reduced distance, and the cumulative consequence of carrying additional fuel over said distance. A further 10% advantage comes from the reduction in total complexity and, therefore, weight due to being able to bypass the stresses of the lower atmosphere, as well as the 40% drop in total weight and the attendant complexity. Another 5% comes from improvements in rocket technology. That still leaves us with about 1,900,000 lbs (of which less than 3% is payload).
What kind of balloon can carry nearly two million pounds of payload? There's only one I know of.
Wednesday, June 30, 2010
Friday, June 18, 2010
The 100-Mile Diameter Telescope
A telescope's effectiveness arises from two factors. 1. It's ability to collect light (a function of the objective size of the light-gathering lens or reflector). 2. It's ability to focus in on far away detail (the telescope's "power").
If your objective lens is proportionately too small for your telescope's power, you get a dim, noisy image. If the light-gathering capacity exceeds the telescope's power, then you're wasting available information.
The best possible telescope of arbitrary size would be one that gathers all the available light coming from a faraway object and resolves it into an image that is as accurately detailed as that quantity of light allows.
This means that a telescope's power, or "zoom" is always a function of its ability to gather light. Bigger lens = better zoom.
Let's compare two telescopes, the Hubble Space Telescope and the proposed James Webb Space Telescope. The Hubble has a light-collecting area of 4.5m^2 (imagine a square about 7 ft on a side). Webb "will" be 25m^2, (imagine a square about 16.5 ft on a side). That means that the Webb would have about 5.5 times more "zoom" than the Hubble. However, because Webb embodies many technological improvements, it's total performance boost is somewhere between 100x and 400x (in the IR range) of that of Hubble.
I want you to imagine what would happen if we took this to an extreme.
Let's imagine the space telescope that might be built fifty years from now using micro-scale assembly of nano-engineered metamaterials, built in the weightlessness of space, far from the Sun.
Some factors to consider when we calculate the factor of improvement.
First of all, metamaterials may enable us to create telescopes that don't require the light to be reflected to a single small collector (think camera or eyepiece). Instead, we may be able to multiply optical efficiency by several factors by foregoing the inherent lossiness of reflection. Layers of specifically-tuned metamaterials may allow us to detect the direction from which a photon is arriving, filtering or disallowing photons from undesired directions. Essentially, the light-gathering surfaces of the future could be thought of as trillions of nano-scale refractor telescopes that use quantum effects and electric fields in place of physical lenses. Essentially, we're talking about an advanced form of the compound eye.
Instead of interacting with the light twice- once upon reflection, once upon detection- we may be able to interact with it just once, upping efficiency in the process.
Instead of curving the entire surface of the collector, small sections of it could be aimed independently. This would allow us to use a flat, essentially two dimensional support structure instead of a far-more-complex 3D structure. Remember, we're building in space- not just because there's no atmosphere to gobble precious photons, but also because zero gravity means you can build big without the object crushing itself. If we build in a remote enough place- more on that later- the object's own mass, and the self-gravity generated thereby, is of more significance than outside forces. Building in a plane confines those forces to the same plane.
Imagine a great flat sheet of high-strength composite honeycomb. The structure might be built in space by robot "bees" that employ some of the same tricks real bees use to build nearly-perfect hexagonal cells. In each of the cells is a gimbaled ring and, inside the ring, a small flat panel of optically-sensitive metamaterial. We'll call these panel sections "scales." Each scale can be aimed separately.
This gives us several advantages which fall under three categories.
1. Perfect focus. Using image feedback from, for instance, known imagery (pointing the telescope at earth for instance), we can adjust individual scales to create the equivalent of a mathematically perfect surface. Only problem is that light traveling to the edges of the gathering plane travels slightly farther, relative to a hypothetical spherical section, than light hitting the center. This means that frequency-scale science would require large amounts of computing power to simulate coherent data. One might expect computing power to be very cheap in the year 2060, but it's good to remember that we're talking about single "images" equivalent to billions of megapixels. Best approach may be to build a computer into each scale and do all the heavy math locally.
2. Selectable focal distance. Our telescope would have one setting for focusing to its maximum detail level at infinity, where the stars and galaxies are, but it could also focus directly on objects within the solar system, or be reconfigured as either an over- or under-powered telescope.
3. Multiple focus. Different areas of the telescope could focus on different objects within the telescope's optimal field of view. In other words, our telescope could be repurposed, in a matter of seconds, from the role of one extremely-large telescope into thousands of merely-large telescopes. This would allow the telescope to be shared in by a large numbers of scientists studying a large number of different objects. Let's say that some interesting signals are coming from a distant star. According to some futuristic mathematical analysis, a supernova is suspected to take place within the next several years. So, part of the telescope is focused on that particular place at all times. One day, things start to evolve. Within three seconds, 95% of the telescope is focused on the supernova. The remaining 5% continues observations that cannot be cut-off without causing intolerable loss of data.
And now for the math you've all been waiting for. How much more powerful than Hubble would our 100-mile diameter telescope be?
First, let's base our calculations on a average optical efficiency of about 50 times that of Hubble. This is based on the suggestion that Webb is about 15 - 70 times more sensitive than Hubble (particularly in the IR range, where dim / small stars are much more visible). It's possible that the numbers may be significantly higher- well over 100x Hubble may be possible. However, metamaterials are almost entirely theoretical at this point in history, so let's not get carried away.
A 100-mile circular diameter comes to about 406,834,381 m^2 of light collecting area. Divide that by 4.5 m^2 and you get a factor of 90,000,000. Multiply that by 50, and you get 4.5 billion.
What could you do with a telescope 4.5 billion times more powerful than Hubble? Crazy things. There are currently 461 known extrasolar planets. With a 100-mile telescope, you could eventually multiply that to over ten billion, some of which might be very interesting. Of known, nearby extrasolars (less than 50 light years) you could map their continents and count their moons. You could measure the gases in their atmospheres to within 1 part in a million. You could study the Oort Cloud in precise detail. You could even study the Oort Clouds of nearby stars. You could study other galaxies with the same level of detail we currently study the Milky Way. Deep field galaxies- the most distant galaxies we've ever seen- could be studied at the same level we currently study nearby galaxies. You'd study quasars- objects the size of solar systems- from across the universe. You could take a picture of Voyager as it leaves the solar system.
For objects within our solar system, it would be like having a microscope. We could study cloud formation on Neptune. We could track microfissures on Europa from billions of miles away. You could map every asteroid with 1:1 detail without sending a single probe.
And you would discover things that no one could possibly predict. For fans of SETI, this could be your key to find the missing aliens, or prove conclusively that they're really missing. Instead of confining your search for lower order life to our own solar system, you could expand your search for life-specific atmospheric oxygen to thousands of planets. And you could search for the apparently non-existent rock-rock-gas-gas-ice-ice solar systems (like ours) with Goldilocks planets (not too hot, not too cold, just right).
And that brings us to the next big question.
Q. Why 100 miles?
A. Because that's the title of this blog entry.
Q. Is there any reason we couldn't use the same modular construction technique to build a 1000-mile telescope?
A. No.
In fact, as you build a 100-mile telescope with individually-aimable scales, you'd start with a 0.01 mile telescope and then build outward. After a while, you'd have a 1-mile telescope, and then a 10-mile telescope. There's no reason you couldn't use these as you continue construction. And there's no reason you couldn't continue construction beyond 100 miles.
At some point, you will reach the physical limits of your construction technique. At that point, you'll have to stop building.
Using the kinds of macroscale construction regimes I discussed in a previous post, Replacement Earths for $1, there's no reason you couldn't continue construction all the way up to the physical limit. So, let's go ahead and do so.
However, there is a way to go beyond the physical limit- a way that solves another problem at the same time.
Here's the problem: the bigger you build, the less feasible it is to change your optimum viewing angle- to aim the whole telescope in a new direction.
Instead of explaining the solution, I'm going to leave this up to the reader to figure out.
Q. How do you build an extremely large (hundreds or even thousands of miles in diameter), single-surface telescope that never needs to be aimed as a whole?
A. See comments below.
If your objective lens is proportionately too small for your telescope's power, you get a dim, noisy image. If the light-gathering capacity exceeds the telescope's power, then you're wasting available information.
The best possible telescope of arbitrary size would be one that gathers all the available light coming from a faraway object and resolves it into an image that is as accurately detailed as that quantity of light allows.
This means that a telescope's power, or "zoom" is always a function of its ability to gather light. Bigger lens = better zoom.
Let's compare two telescopes, the Hubble Space Telescope and the proposed James Webb Space Telescope. The Hubble has a light-collecting area of 4.5m^2 (imagine a square about 7 ft on a side). Webb "will" be 25m^2, (imagine a square about 16.5 ft on a side). That means that the Webb would have about 5.5 times more "zoom" than the Hubble. However, because Webb embodies many technological improvements, it's total performance boost is somewhere between 100x and 400x (in the IR range) of that of Hubble.
I want you to imagine what would happen if we took this to an extreme.
Let's imagine the space telescope that might be built fifty years from now using micro-scale assembly of nano-engineered metamaterials, built in the weightlessness of space, far from the Sun.
Some factors to consider when we calculate the factor of improvement.
First of all, metamaterials may enable us to create telescopes that don't require the light to be reflected to a single small collector (think camera or eyepiece). Instead, we may be able to multiply optical efficiency by several factors by foregoing the inherent lossiness of reflection. Layers of specifically-tuned metamaterials may allow us to detect the direction from which a photon is arriving, filtering or disallowing photons from undesired directions. Essentially, the light-gathering surfaces of the future could be thought of as trillions of nano-scale refractor telescopes that use quantum effects and electric fields in place of physical lenses. Essentially, we're talking about an advanced form of the compound eye.
Instead of interacting with the light twice- once upon reflection, once upon detection- we may be able to interact with it just once, upping efficiency in the process.
Instead of curving the entire surface of the collector, small sections of it could be aimed independently. This would allow us to use a flat, essentially two dimensional support structure instead of a far-more-complex 3D structure. Remember, we're building in space- not just because there's no atmosphere to gobble precious photons, but also because zero gravity means you can build big without the object crushing itself. If we build in a remote enough place- more on that later- the object's own mass, and the self-gravity generated thereby, is of more significance than outside forces. Building in a plane confines those forces to the same plane.
Imagine a great flat sheet of high-strength composite honeycomb. The structure might be built in space by robot "bees" that employ some of the same tricks real bees use to build nearly-perfect hexagonal cells. In each of the cells is a gimbaled ring and, inside the ring, a small flat panel of optically-sensitive metamaterial. We'll call these panel sections "scales." Each scale can be aimed separately.
This gives us several advantages which fall under three categories.
1. Perfect focus. Using image feedback from, for instance, known imagery (pointing the telescope at earth for instance), we can adjust individual scales to create the equivalent of a mathematically perfect surface. Only problem is that light traveling to the edges of the gathering plane travels slightly farther, relative to a hypothetical spherical section, than light hitting the center. This means that frequency-scale science would require large amounts of computing power to simulate coherent data. One might expect computing power to be very cheap in the year 2060, but it's good to remember that we're talking about single "images" equivalent to billions of megapixels. Best approach may be to build a computer into each scale and do all the heavy math locally.
2. Selectable focal distance. Our telescope would have one setting for focusing to its maximum detail level at infinity, where the stars and galaxies are, but it could also focus directly on objects within the solar system, or be reconfigured as either an over- or under-powered telescope.
3. Multiple focus. Different areas of the telescope could focus on different objects within the telescope's optimal field of view. In other words, our telescope could be repurposed, in a matter of seconds, from the role of one extremely-large telescope into thousands of merely-large telescopes. This would allow the telescope to be shared in by a large numbers of scientists studying a large number of different objects. Let's say that some interesting signals are coming from a distant star. According to some futuristic mathematical analysis, a supernova is suspected to take place within the next several years. So, part of the telescope is focused on that particular place at all times. One day, things start to evolve. Within three seconds, 95% of the telescope is focused on the supernova. The remaining 5% continues observations that cannot be cut-off without causing intolerable loss of data.
And now for the math you've all been waiting for. How much more powerful than Hubble would our 100-mile diameter telescope be?
First, let's base our calculations on a average optical efficiency of about 50 times that of Hubble. This is based on the suggestion that Webb is about 15 - 70 times more sensitive than Hubble (particularly in the IR range, where dim / small stars are much more visible). It's possible that the numbers may be significantly higher- well over 100x Hubble may be possible. However, metamaterials are almost entirely theoretical at this point in history, so let's not get carried away.
A 100-mile circular diameter comes to about 406,834,381 m^2 of light collecting area. Divide that by 4.5 m^2 and you get a factor of 90,000,000. Multiply that by 50, and you get 4.5 billion.
What could you do with a telescope 4.5 billion times more powerful than Hubble? Crazy things. There are currently 461 known extrasolar planets. With a 100-mile telescope, you could eventually multiply that to over ten billion, some of which might be very interesting. Of known, nearby extrasolars (less than 50 light years) you could map their continents and count their moons. You could measure the gases in their atmospheres to within 1 part in a million. You could study the Oort Cloud in precise detail. You could even study the Oort Clouds of nearby stars. You could study other galaxies with the same level of detail we currently study the Milky Way. Deep field galaxies- the most distant galaxies we've ever seen- could be studied at the same level we currently study nearby galaxies. You'd study quasars- objects the size of solar systems- from across the universe. You could take a picture of Voyager as it leaves the solar system.
For objects within our solar system, it would be like having a microscope. We could study cloud formation on Neptune. We could track microfissures on Europa from billions of miles away. You could map every asteroid with 1:1 detail without sending a single probe.
And you would discover things that no one could possibly predict. For fans of SETI, this could be your key to find the missing aliens, or prove conclusively that they're really missing. Instead of confining your search for lower order life to our own solar system, you could expand your search for life-specific atmospheric oxygen to thousands of planets. And you could search for the apparently non-existent rock-rock-gas-gas-ice-ice solar systems (like ours) with Goldilocks planets (not too hot, not too cold, just right).
And that brings us to the next big question.
Q. Why 100 miles?
A. Because that's the title of this blog entry.
Q. Is there any reason we couldn't use the same modular construction technique to build a 1000-mile telescope?
A. No.
In fact, as you build a 100-mile telescope with individually-aimable scales, you'd start with a 0.01 mile telescope and then build outward. After a while, you'd have a 1-mile telescope, and then a 10-mile telescope. There's no reason you couldn't use these as you continue construction. And there's no reason you couldn't continue construction beyond 100 miles.
At some point, you will reach the physical limits of your construction technique. At that point, you'll have to stop building.
Using the kinds of macroscale construction regimes I discussed in a previous post, Replacement Earths for $1, there's no reason you couldn't continue construction all the way up to the physical limit. So, let's go ahead and do so.
However, there is a way to go beyond the physical limit- a way that solves another problem at the same time.
Here's the problem: the bigger you build, the less feasible it is to change your optimum viewing angle- to aim the whole telescope in a new direction.
Instead of explaining the solution, I'm going to leave this up to the reader to figure out.
Q. How do you build an extremely large (hundreds or even thousands of miles in diameter), single-surface telescope that never needs to be aimed as a whole?
A. See comments below.
Friday, June 11, 2010
The Multi-Engine Electric Hang Glider
Hang gliders only ascend when the surrounding air is ascending. Wind deflected by hills. Pockets of warm air rising. Hang gliders go up for the same reason kites fly. And kites don't need complex airfoils. They're just sails.
Powered aircraft ascend by using their engines to move fast enough to provide their wings with wind. Wind flowing over wings produces lift.
So why do gliders have airfoils- wings with top surfaces longer than than their bottom surfaces- if they're not what makes them rise? Because gliders need to be able to remain in the air as long as possible. To loiter and maneuver to locate the rising air. Just as powered aircraft use airfoils to convert forward motion into altitude, gliders use theirs to convert altitude into forward motion.
What if you put an engine on a hang glider? It's been done. Many ultralights use hang glider wings. Such aircraft land on wheels. Some people employ a simpler approach, attaching a small 15hp engine directly to their flying harness. These are launched and landed on foot.
Powered hang glider require special skill on take-off and landing. And they're not as appropriate for mountain launches. When flying under full power, the pilot is pushed forward through the control bar. This results in a control attitude that is equivalent to a power dive. It's not a very strong position to be in. The pilot is also managing an extra source of aerodynamic directional control because she is directly attached to the source of thrust. This added dimension of control partially obscures the "natural" control motions normally required to fly a hang glider. Also, the propeller provides a substantial amount of drag when the engine is off. Usually this is addressed by building in features that allow the prop to feather or fold back.
Powered hang gliders are chimeras. They are neither gliders nor aircraft, but represent a compromise between two incompatible ideals. On one hand is pure soaring flight to which the added noise, cost, weight, and drag of engines is anathema. Hang gliders are designed to be gliders. They're designed to be controlled via weight shift.
On the other hand is powered, three-dimensional, acrobatic flight. Or, if you prefer: high-speed / long-distance passenger service. Aircraft design varies accordingly. Powered aircraft rarely look anything like hang gliders.
If you're a pilot that's interested in soaring, organic control, and the elegance of physically carrying your wing until it carries you, then you're attracted to hang gliding. Otherwise, you'll probably head elsewhere.
However, I'm thinking that there probably isn't a HG pilot that wouldn't appreciate an engine occasionally. Sometimes you want to take off from flat ground and fly flatland thermal- without going to the multiplied trouble of being towed by another aircraft. Sometimes you'd want to boost yourself back into ridge lift instead of drifting down to a faraway valley at the loss of hours of flying. And then there are times when circumstances have left you no option but to crashland in unsuitable terrain- forests, rocks, cacti. In addition to an emergency chute, a bit of thrust would make for an excellent safety feature.
But if you look at the options already available, having an engine for these special occasions means managing a significant amount of awkwardness and drag on a constant basis. So,
What I'm proposing is that the hang glider be equipped with an odd number of small electric ducted fans attached directly to the glider's wing- not to the harness. The fans already exist. They're made for radio controlled scaled-down jet aircraft. And batteries have never been more advanced.
Ducted fans are an efficient way to produce low-speed thrust- in the regime of 0-100mph. Ducts drastically reduce blade tip losses- vortexes of turbulence that don't contribute to thrust. Ducts add complexity and weight, however, which may outweigh the efficiency gains at higher speeds. Also, high speeds entail greater amounts of induced drag caused by the ducts themselves. But DFs, with their shorter diameters, can also operate at higher RPMs than similarly powered open props. Electric motors are a perfect choice for taking advantage of this.
When not under power, the drag a propeller's generates is proportional to the area of the circle of the propeller's sweep. That doesn't mean that the induced drag is exactly equivalent to what would be caused by a flat solid disk of the same diameter. It's significantly less than that. It only means that the wider the propeller, the more drag it creates when not under power. A helicopter, for instance, with its massive prop-diameter, produces enough drag to actually land safely even if the engine quits (see autorotation). Propeller = parachute.
Ducted fans allow for comparatively tiny cross sections.
By using several of them, let's say five, you take advantage of a miniature expression of the multi-engine advantage. Why do large aircraft- WWII bombers, for instance- employ multiple engines? It's not because a single engines couldn't be built that could provide enough power. Bigger engines almost always provides a better power-to-weight ratio (this doesn't apply as much to electric motors). Instead, it's because propellers would have to get very large and be driven very fast- and the blade tips would be exceeding the speed of sound which would generate all kinds of horrible turbulence. Multiple engines allows for smaller prop diameters to generate the same amount of thrust.
That's one side of the argument in favor of multiple engines. The other side is that smaller prop diameters entail far less drag. Assuming you have efficient small engines, and assuming those engines aren't always running, multiple small engines entail far less drag.
Let's do some math, using two small DFs as examples.
First, tuck this away: a Mosquito powered hang glider uses a prop with a 1.35m diameter. That translates to a prop-circle area of 1.42 m^2. The engine / prop combination the Mosquito uses produces about 130 lbs of thrust. That's about 96 lbs / m^2. Sorry about the mixed units. I'm an American.
Let's take a look at some electric DFs: this produces 18+ lbs of thrust with a 120mm diameter or 0.0113m^2. That's about 1592lbs / m^2.
Meanwhile, this one produces 28+ lbs of thrust with a 156mm diameter (0.0191m^2). That equals 1464 lbs / m^2.
The drag induced by a 30% greater diameter cancels out the proportional advantage of 55% greater thrust. Let me put it this way.
The least common multiple of 18 and 28 is 252.
14 x 18 = 252 lbs
9 x 28 = 252 lbs
To get 252 lbs of thrust, you could use 14 of the 18lb ducted fans or
9 of the 28lb ducted fans.
14 x 0.0113m^2 = 0.1582m^2
9 x 0.0191m^2 = 0.1719m^2
If you needed to produce 252lbs of thrust, and if all you cared about was the amount of drag the ducted fan would produce when not in use, 14 slightly smaller DF's' would entail around 8% less drag than 9 of the larger, more powerful ones.
That's how ducted fans roll. They make smaller diameters more stream-lined for similar amounts of power.
Let's assume that each DF is designed to produce some amount of static thrust at some particular operating speed. Either slower or faster is less efficient. Let's call this peak efficiency, or PE.
Let's also assume that each DF can produce significantly more power- albeit at a lower efficiency / longevity. Let's call this peak power, or PP.
Let's also assume that you can also operate your DFs to produce just enough thrust to overcome the drag they produce just sitting there. We'll call this peak longevity (I'd say "endurance," but I already used the letter "E"), or PL.
Why use an odd number of DFs?
If you had five DFs in a row (and I'm not saying it would have to be five. Likely you'd end up wanting between 7 and 11)- two on each wing and one in the center- you could turn them off in the follow progression:
5- all on
4- all but the center one on
3- one on each wing plus the center
2- one on each wing
1- just the center
Let's run some scenarios.
A. Let's say you find yourself in a momentary emergency situation. You need to produce maximum lift in the least amount of time to avoid hitting an imminent obstacle. You turn all five DFs to PP and switch to PE as soon as you're out of the woods.
B. You've dipped into a mountain valley and need to fight your way back into the ridge lift. You don't dare fly too close to the sheer mountain walls, where turbulence is unpredictable. You have open airspace to operate in, and- if necessary- an emergency place to land down at the valley floor. So you switch all five fans to PE and work your way back up until you've above the ridgeline again.
C. You're flying cross country and you haven't even needed your DFs at all. Your batteries are full. So you operate all five fans at PL to give yourself the best possible flight characteristics.
D. You're at 8000ft AGL, flying cross country, and a wide long lake is in your path. You believe that you have enough altitude to glide across with up-to a mile of glide to spare. However, you'd be at such a low altitude on the other side that you'd have precious little chance to find another thermal and make your way back up to cloudbase. Your flight would probably be over for the day. You ask yourself: am I a soaring purist, or am I a pilot? You decide you'd rather fly that break a record, so you set two of the five fans to operate at PE, providing yourself just enough thrust to maintain your present altitude. Halfway across the lake, you encounter sinking air. Instead of wasting time maneuvering in an attempt to find more favorable air you turn on another fan- also operating at PE. After five minutes, you cut to two. Once your shadow hits the shoreline you turn all but one of them off. You're still at 6500 ft when you encounter your first hint of a thermal. Ten minutes later and your high-altitude swim is all but forgotten.
E. You've been flying cross country for several hours and you could really use a break. It's the middle of the day. You spy a truckstop with huge, mostly vacant parking lots so you meander down, flaring out in the grass at the edge of the lot. You tie your glider down, jog to the bathroom, catch some lunch, and then, with crowd of bemused onlookers wondering what you have in mind, you strap back into your harness, face into the wind, run, turn on all five DFs at PP, lift off, and make a lazy wide circle over the hot parking lot. After you've gained fifty feet of altitude, you switch to PE. Another fifty, and you're getting some positive help from the inevitable black-top thermal. You're back at altitude and on your way.
D. You're contemplating a mountain launch, but the ideal launch direction the site provides is facing 45 degrees away from the direction of wind. What's worse, the wind is averaging 5 mph less than what'd you'd like. So you angle yourself straight into the wind. Two volunteers hold your wings as you ready yourself. You turn on all five fans at PE and start your run. Your HG tugs against your ground handlers. You shout, "clear," and instead of five steps, you're off in three. Instead of dipping down fifty feet before leveling off, you lose nothing. You're alerady climbing. Thirty seconds later, you cut out all five DFs and emerge into a high pocket of ridge lift. For the rest of your flight, your DFs are running at PL.
E. You've just driven 10 hours to fly at a particular mountain in the foothills of Idaho. It's early afternoon and when you arrive, the windsocks are laying limp. You wait an hour, and other than an occasional 8mph gust, it's a still day. You're not looking for an epic journey, you just want to get off the ground. So you power up, setting all five DFs at PE, and up you go. You let all five DFs run at PE until the battery is about dead, stealing altitude from an uncooperative sky. Then you switch to PL and you quietly glide back to earth. What would have been a five minute flight has been stretched into almost an hour.
F. The unimaginable has transpired. One of your under wing guy lines has broken its shackle in a violent bout of vertical turbulence and now your wing is slightly skewed and threatening to deteriorate further. You were flying over steep, tree-covered terrain when it happened. A quarter mile away is an inviting mountain meadow. You have a choice- throw your parachute immediately and land in the trees- or gently nudge your wounded wing into more inviting terrain before hitting the silk. Only problem is, the winds just aren't cooperating with your plans. So your first reflex is to give yourself some emergency power. You point your nose to safe terrain. Simultaneously, one hand has gone to your chute, pulling it from its pocket on your chest. You mentally rehearse your throw, ready to move the moment things get any worse. A subjective hour later, you're over the meadow. You have a few hundred more feet of altitude than you would have had you not used the DFs. Parachute in hand, you take a few extra moments to survey the terrain. Time slows. Satisfied, you make your throw. Your forward progress is abruptly halted and you begin to descend at an angle, turning slowly as you go. You see that you're headed for one of the few small pines that occupy the otherwise open meadow so you goose the throttle on your DFs, producing moments of PP whenever you're facing away from the tree. You radio back that you're okay, fold up, and hike out. You realize that if you'd deployed your chute immediately, you very well might have spent the remainder of the day, scratched and bleeding, a hundred feet up in a tree.
G. You've decided to fly across the United States. You're going from west to east, following the prevailing winds. You keep within sight of roads and highways as you go. Each day, you fly as far as the weather and wind will permit, using your DFs to boost your altitude whenever expedience requires. On cooperative days, the sky gives up hundreds hundreds of miles. Some days you fly from morning to afternoon. Others, you stop several times at towns, or rural gas stations, and beg electricity in exchange for telling your story. You're often invited to supper. Most of the time, people offer you a place to sleep. After you cross the Mississippi, you encounter a patch of rainy weather that lasts for most of a week. You fold up and take advantage of a friendly stranger's offer to store your glider in his garage. When the weather clears, you head east again. After two months, you swing out over the Atlantic and then come to rest on a beach in North Carolina. You're greeted by a crowd of well-wishers who've been following your progress online.
I could write more about the technical details. The types of batteries you'd use (at least 40lbs of compact rechargeable lithium ion batteries designed for small electric cars). I could talk about how, with five DFs, you'd have two on each wing and one on the centerline and that by varying the thrust bilaterally, one could steer the wing. I could talk about how you could use either a system of switches to turn DFs on and off and a single throttle, similar to a motorcycle's throttle control, that varys the power of everything that's turned on. The pilot could have a second throttle-like control, or lateral sliding control, that moves power from side to side to assist in steering. Finally, the pilot could have presets that would keep the DFs running at PP, PE, or PL in whatever configuration she desires.
The DFs could be mounted in a number of different ways. I expect the most practical arrangement would be to mount them to the crossbar under the wing. The center DF could be mounted to the keel. It's important that the DFs be mounted in a way that doesn't cause them to crushed or filled with grass during a noseplant.
I used an example above with 252 lbs of thrust. That's well more than necessary. Somewhere around 170lbs of PP thrust should be sufficient. More than that, and the pilot would be tempted to stray into acrobatic flight.
Total 5 x PE flight time might be around 30 minutes. Dividing the number of DFs multiplies the endurance.
In summary, what makes this idea potentially superior to powered hang gliders that already exist is that it hews closer to the ideal of pure soaring flight. It allows the hang glider to handle like a hang glider again. Instead of turning a hang glider into a small ultralight, it provides occasional assistance, extra flexibility, and emergency power. It allows for take-off from flat ground /and/ hill launches without reconfiguration. It enhances cross-country endurance by providing a bridge between hotspots.
And, if you were to install lightweight photovoltaic cells- like the thin copper indium gallium diselenide films promised by Nanosolar, you might have yourself a solar soarer capable of indefinitely extending its daytime endurance or, in a pinch, of getting off the ground again after a wilderness landing.
Q. Isn't having a powered option kinda like cheating?
A. Yes... but, you should ask yourself whether the added versatility, longevity, would make you a better pilot, or worse. If the answer is "worse," then this concept isn't for you. On the other hand, if you think of this as a safety device, then no, it isn't cheating.
Q. How much will they cost?
A. About $12k fully assembled and tested.
Q. What if I'm building one myself?
A. Between $7k and $10k.
Q. What would you need to make this happen?
A. An investor- initial prototyping should be achievable for less than $50k / 6 mos. A hang glider engineer- someone with a lot of experience repairing, rebuilding, and modifying hang gliders. An "RC Engineer"- someone with experience working with the propulsion equipment. And a test pilot- an advanced hang glider pilot with powered experience. A spokesman (probably one of the aforementioned persons)- someone that can navigate the news media to generate free advertising.
Q. What will this do to the sport of hang gliding?
A. This has the potential for attracting new interest to the sport of hang gliding, as well as reviving the interest of some percentage of existing pilots. People who live in flat areas, or are repelled by their impression of the inherent risk and uncertainty of unpowered flight, may use see this as an excuse for giving the sport a second chance. DFs will also add to the cool-tech factor, expanding the potential customer base accordingly.
Powered aircraft ascend by using their engines to move fast enough to provide their wings with wind. Wind flowing over wings produces lift.
So why do gliders have airfoils- wings with top surfaces longer than than their bottom surfaces- if they're not what makes them rise? Because gliders need to be able to remain in the air as long as possible. To loiter and maneuver to locate the rising air. Just as powered aircraft use airfoils to convert forward motion into altitude, gliders use theirs to convert altitude into forward motion.
What if you put an engine on a hang glider? It's been done. Many ultralights use hang glider wings. Such aircraft land on wheels. Some people employ a simpler approach, attaching a small 15hp engine directly to their flying harness. These are launched and landed on foot.
Powered hang glider require special skill on take-off and landing. And they're not as appropriate for mountain launches. When flying under full power, the pilot is pushed forward through the control bar. This results in a control attitude that is equivalent to a power dive. It's not a very strong position to be in. The pilot is also managing an extra source of aerodynamic directional control because she is directly attached to the source of thrust. This added dimension of control partially obscures the "natural" control motions normally required to fly a hang glider. Also, the propeller provides a substantial amount of drag when the engine is off. Usually this is addressed by building in features that allow the prop to feather or fold back.
Powered hang gliders are chimeras. They are neither gliders nor aircraft, but represent a compromise between two incompatible ideals. On one hand is pure soaring flight to which the added noise, cost, weight, and drag of engines is anathema. Hang gliders are designed to be gliders. They're designed to be controlled via weight shift.
On the other hand is powered, three-dimensional, acrobatic flight. Or, if you prefer: high-speed / long-distance passenger service. Aircraft design varies accordingly. Powered aircraft rarely look anything like hang gliders.
If you're a pilot that's interested in soaring, organic control, and the elegance of physically carrying your wing until it carries you, then you're attracted to hang gliding. Otherwise, you'll probably head elsewhere.
However, I'm thinking that there probably isn't a HG pilot that wouldn't appreciate an engine occasionally. Sometimes you want to take off from flat ground and fly flatland thermal- without going to the multiplied trouble of being towed by another aircraft. Sometimes you'd want to boost yourself back into ridge lift instead of drifting down to a faraway valley at the loss of hours of flying. And then there are times when circumstances have left you no option but to crashland in unsuitable terrain- forests, rocks, cacti. In addition to an emergency chute, a bit of thrust would make for an excellent safety feature.
But if you look at the options already available, having an engine for these special occasions means managing a significant amount of awkwardness and drag on a constant basis. So,
What I'm proposing is that the hang glider be equipped with an odd number of small electric ducted fans attached directly to the glider's wing- not to the harness. The fans already exist. They're made for radio controlled scaled-down jet aircraft. And batteries have never been more advanced.
Ducted fans are an efficient way to produce low-speed thrust- in the regime of 0-100mph. Ducts drastically reduce blade tip losses- vortexes of turbulence that don't contribute to thrust. Ducts add complexity and weight, however, which may outweigh the efficiency gains at higher speeds. Also, high speeds entail greater amounts of induced drag caused by the ducts themselves. But DFs, with their shorter diameters, can also operate at higher RPMs than similarly powered open props. Electric motors are a perfect choice for taking advantage of this.
When not under power, the drag a propeller's generates is proportional to the area of the circle of the propeller's sweep. That doesn't mean that the induced drag is exactly equivalent to what would be caused by a flat solid disk of the same diameter. It's significantly less than that. It only means that the wider the propeller, the more drag it creates when not under power. A helicopter, for instance, with its massive prop-diameter, produces enough drag to actually land safely even if the engine quits (see autorotation). Propeller = parachute.
Ducted fans allow for comparatively tiny cross sections.
By using several of them, let's say five, you take advantage of a miniature expression of the multi-engine advantage. Why do large aircraft- WWII bombers, for instance- employ multiple engines? It's not because a single engines couldn't be built that could provide enough power. Bigger engines almost always provides a better power-to-weight ratio (this doesn't apply as much to electric motors). Instead, it's because propellers would have to get very large and be driven very fast- and the blade tips would be exceeding the speed of sound which would generate all kinds of horrible turbulence. Multiple engines allows for smaller prop diameters to generate the same amount of thrust.
That's one side of the argument in favor of multiple engines. The other side is that smaller prop diameters entail far less drag. Assuming you have efficient small engines, and assuming those engines aren't always running, multiple small engines entail far less drag.
Let's do some math, using two small DFs as examples.
First, tuck this away: a Mosquito powered hang glider uses a prop with a 1.35m diameter. That translates to a prop-circle area of 1.42 m^2. The engine / prop combination the Mosquito uses produces about 130 lbs of thrust. That's about 96 lbs / m^2. Sorry about the mixed units. I'm an American.
Let's take a look at some electric DFs: this produces 18+ lbs of thrust with a 120mm diameter or 0.0113m^2. That's about 1592lbs / m^2.
Meanwhile, this one produces 28+ lbs of thrust with a 156mm diameter (0.0191m^2). That equals 1464 lbs / m^2.
The drag induced by a 30% greater diameter cancels out the proportional advantage of 55% greater thrust. Let me put it this way.
The least common multiple of 18 and 28 is 252.
14 x 18 = 252 lbs
9 x 28 = 252 lbs
To get 252 lbs of thrust, you could use 14 of the 18lb ducted fans or
9 of the 28lb ducted fans.
14 x 0.0113m^2 = 0.1582m^2
9 x 0.0191m^2 = 0.1719m^2
If you needed to produce 252lbs of thrust, and if all you cared about was the amount of drag the ducted fan would produce when not in use, 14 slightly smaller DF's' would entail around 8% less drag than 9 of the larger, more powerful ones.
That's how ducted fans roll. They make smaller diameters more stream-lined for similar amounts of power.
Let's assume that each DF is designed to produce some amount of static thrust at some particular operating speed. Either slower or faster is less efficient. Let's call this peak efficiency, or PE.
Let's also assume that each DF can produce significantly more power- albeit at a lower efficiency / longevity. Let's call this peak power, or PP.
Let's also assume that you can also operate your DFs to produce just enough thrust to overcome the drag they produce just sitting there. We'll call this peak longevity (I'd say "endurance," but I already used the letter "E"), or PL.
Why use an odd number of DFs?
If you had five DFs in a row (and I'm not saying it would have to be five. Likely you'd end up wanting between 7 and 11)- two on each wing and one in the center- you could turn them off in the follow progression:
5- all on
4- all but the center one on
3- one on each wing plus the center
2- one on each wing
1- just the center
Let's run some scenarios.
A. Let's say you find yourself in a momentary emergency situation. You need to produce maximum lift in the least amount of time to avoid hitting an imminent obstacle. You turn all five DFs to PP and switch to PE as soon as you're out of the woods.
B. You've dipped into a mountain valley and need to fight your way back into the ridge lift. You don't dare fly too close to the sheer mountain walls, where turbulence is unpredictable. You have open airspace to operate in, and- if necessary- an emergency place to land down at the valley floor. So you switch all five fans to PE and work your way back up until you've above the ridgeline again.
C. You're flying cross country and you haven't even needed your DFs at all. Your batteries are full. So you operate all five fans at PL to give yourself the best possible flight characteristics.
D. You're at 8000ft AGL, flying cross country, and a wide long lake is in your path. You believe that you have enough altitude to glide across with up-to a mile of glide to spare. However, you'd be at such a low altitude on the other side that you'd have precious little chance to find another thermal and make your way back up to cloudbase. Your flight would probably be over for the day. You ask yourself: am I a soaring purist, or am I a pilot? You decide you'd rather fly that break a record, so you set two of the five fans to operate at PE, providing yourself just enough thrust to maintain your present altitude. Halfway across the lake, you encounter sinking air. Instead of wasting time maneuvering in an attempt to find more favorable air you turn on another fan- also operating at PE. After five minutes, you cut to two. Once your shadow hits the shoreline you turn all but one of them off. You're still at 6500 ft when you encounter your first hint of a thermal. Ten minutes later and your high-altitude swim is all but forgotten.
E. You've been flying cross country for several hours and you could really use a break. It's the middle of the day. You spy a truckstop with huge, mostly vacant parking lots so you meander down, flaring out in the grass at the edge of the lot. You tie your glider down, jog to the bathroom, catch some lunch, and then, with crowd of bemused onlookers wondering what you have in mind, you strap back into your harness, face into the wind, run, turn on all five DFs at PP, lift off, and make a lazy wide circle over the hot parking lot. After you've gained fifty feet of altitude, you switch to PE. Another fifty, and you're getting some positive help from the inevitable black-top thermal. You're back at altitude and on your way.
D. You're contemplating a mountain launch, but the ideal launch direction the site provides is facing 45 degrees away from the direction of wind. What's worse, the wind is averaging 5 mph less than what'd you'd like. So you angle yourself straight into the wind. Two volunteers hold your wings as you ready yourself. You turn on all five fans at PE and start your run. Your HG tugs against your ground handlers. You shout, "clear," and instead of five steps, you're off in three. Instead of dipping down fifty feet before leveling off, you lose nothing. You're alerady climbing. Thirty seconds later, you cut out all five DFs and emerge into a high pocket of ridge lift. For the rest of your flight, your DFs are running at PL.
E. You've just driven 10 hours to fly at a particular mountain in the foothills of Idaho. It's early afternoon and when you arrive, the windsocks are laying limp. You wait an hour, and other than an occasional 8mph gust, it's a still day. You're not looking for an epic journey, you just want to get off the ground. So you power up, setting all five DFs at PE, and up you go. You let all five DFs run at PE until the battery is about dead, stealing altitude from an uncooperative sky. Then you switch to PL and you quietly glide back to earth. What would have been a five minute flight has been stretched into almost an hour.
F. The unimaginable has transpired. One of your under wing guy lines has broken its shackle in a violent bout of vertical turbulence and now your wing is slightly skewed and threatening to deteriorate further. You were flying over steep, tree-covered terrain when it happened. A quarter mile away is an inviting mountain meadow. You have a choice- throw your parachute immediately and land in the trees- or gently nudge your wounded wing into more inviting terrain before hitting the silk. Only problem is, the winds just aren't cooperating with your plans. So your first reflex is to give yourself some emergency power. You point your nose to safe terrain. Simultaneously, one hand has gone to your chute, pulling it from its pocket on your chest. You mentally rehearse your throw, ready to move the moment things get any worse. A subjective hour later, you're over the meadow. You have a few hundred more feet of altitude than you would have had you not used the DFs. Parachute in hand, you take a few extra moments to survey the terrain. Time slows. Satisfied, you make your throw. Your forward progress is abruptly halted and you begin to descend at an angle, turning slowly as you go. You see that you're headed for one of the few small pines that occupy the otherwise open meadow so you goose the throttle on your DFs, producing moments of PP whenever you're facing away from the tree. You radio back that you're okay, fold up, and hike out. You realize that if you'd deployed your chute immediately, you very well might have spent the remainder of the day, scratched and bleeding, a hundred feet up in a tree.
G. You've decided to fly across the United States. You're going from west to east, following the prevailing winds. You keep within sight of roads and highways as you go. Each day, you fly as far as the weather and wind will permit, using your DFs to boost your altitude whenever expedience requires. On cooperative days, the sky gives up hundreds hundreds of miles. Some days you fly from morning to afternoon. Others, you stop several times at towns, or rural gas stations, and beg electricity in exchange for telling your story. You're often invited to supper. Most of the time, people offer you a place to sleep. After you cross the Mississippi, you encounter a patch of rainy weather that lasts for most of a week. You fold up and take advantage of a friendly stranger's offer to store your glider in his garage. When the weather clears, you head east again. After two months, you swing out over the Atlantic and then come to rest on a beach in North Carolina. You're greeted by a crowd of well-wishers who've been following your progress online.
I could write more about the technical details. The types of batteries you'd use (at least 40lbs of compact rechargeable lithium ion batteries designed for small electric cars). I could talk about how, with five DFs, you'd have two on each wing and one on the centerline and that by varying the thrust bilaterally, one could steer the wing. I could talk about how you could use either a system of switches to turn DFs on and off and a single throttle, similar to a motorcycle's throttle control, that varys the power of everything that's turned on. The pilot could have a second throttle-like control, or lateral sliding control, that moves power from side to side to assist in steering. Finally, the pilot could have presets that would keep the DFs running at PP, PE, or PL in whatever configuration she desires.
The DFs could be mounted in a number of different ways. I expect the most practical arrangement would be to mount them to the crossbar under the wing. The center DF could be mounted to the keel. It's important that the DFs be mounted in a way that doesn't cause them to crushed or filled with grass during a noseplant.
I used an example above with 252 lbs of thrust. That's well more than necessary. Somewhere around 170lbs of PP thrust should be sufficient. More than that, and the pilot would be tempted to stray into acrobatic flight.
Total 5 x PE flight time might be around 30 minutes. Dividing the number of DFs multiplies the endurance.
In summary, what makes this idea potentially superior to powered hang gliders that already exist is that it hews closer to the ideal of pure soaring flight. It allows the hang glider to handle like a hang glider again. Instead of turning a hang glider into a small ultralight, it provides occasional assistance, extra flexibility, and emergency power. It allows for take-off from flat ground /and/ hill launches without reconfiguration. It enhances cross-country endurance by providing a bridge between hotspots.
And, if you were to install lightweight photovoltaic cells- like the thin copper indium gallium diselenide films promised by Nanosolar, you might have yourself a solar soarer capable of indefinitely extending its daytime endurance or, in a pinch, of getting off the ground again after a wilderness landing.
Q. Isn't having a powered option kinda like cheating?
A. Yes... but, you should ask yourself whether the added versatility, longevity, would make you a better pilot, or worse. If the answer is "worse," then this concept isn't for you. On the other hand, if you think of this as a safety device, then no, it isn't cheating.
Q. How much will they cost?
A. About $12k fully assembled and tested.
Q. What if I'm building one myself?
A. Between $7k and $10k.
Q. What would you need to make this happen?
A. An investor- initial prototyping should be achievable for less than $50k / 6 mos. A hang glider engineer- someone with a lot of experience repairing, rebuilding, and modifying hang gliders. An "RC Engineer"- someone with experience working with the propulsion equipment. And a test pilot- an advanced hang glider pilot with powered experience. A spokesman (probably one of the aforementioned persons)- someone that can navigate the news media to generate free advertising.
Q. What will this do to the sport of hang gliding?
A. This has the potential for attracting new interest to the sport of hang gliding, as well as reviving the interest of some percentage of existing pilots. People who live in flat areas, or are repelled by their impression of the inherent risk and uncertainty of unpowered flight, may use see this as an excuse for giving the sport a second chance. DFs will also add to the cool-tech factor, expanding the potential customer base accordingly.
Wednesday, June 9, 2010
Barefoot With Shoes On
This blog is about an experiment in toughening the soles of my feet.
For the last three weeks I've gone hiking barefoot. The idea came to me at the end of a trail. Shoes were already off to wade in a cryogenic stream. The trail was about a mile and a half long, covered with sharp cubic quartzite gravel. It made for some slow going. Speed didn't come natural.
Which was good, because it made an otherwise short hike last longer. Instead of waiting in the parking lot, I was waited-for- at least for a couple minutes.
The next week was similar. About two miles total over a mix of gravel, scree, talus, and- toward the end- across the forest floor. My feet were sore after that one too. I was the slowest poke around. Again, a short hike made more substantial by barefooting it.
This last weekend, I hiked about 3.6 miles. This trail was through a pine forest, occasional sand, gravel, snakes (x2), and stone outcroppings. This week I didn't just hike, I jogged, I ran. I kept ahead of other shoe-wearers. I was no kind of slowpoke.
And my feet were about as sore as they'd been the previous two weeks. Not too bad.
Today I bought a single 3-tab shingle asphalt composite shingles from Home Depot. It traced my foot, cut off half my big toe (on the cut-out, not the toe itself) and made myself a pair of gravel-covered insoles to use without socks.
The shingles probably won't last a day before I wear all the gravel granules off. The combination of heat and friction will, doubtless, make short work of them.
What I need is a pair of durable, rough-gravel insoles that won't degrade from the heat typical to the human foot. If I can toughen my feet up on odd-numbered days, and maintain that toughness even when I'm not hiking barefoot, then going barefoot when I want to would be far more appealing. Instead of being an exercise in pain management, I'd be able to focus on the unique sensory experience of being in touch with the ground.
Is it strange to want to go barefoot? No, not really. Barefoot is healthy. It allows your feet and gait to take their natural shape. Going barefoot causes you to adapt to your surroundings, distribute your weight, tread lightly. Instead of pounding on your heels and jarring your knees, barefooting makes you glide, naturally. Vibram, of shoe tread fame, makes shoes that mimic the look and feel of going barefoot, called FiveFingers. They literally have five little toes. I admire the concept. For people who want to wear shoes, who don't want to experience the pain or risk of going shoeless, or who want to go out in hot or cold weather (shoeless even on white concrete in the summer is torture).
So, that's the idea. Durable foot-toughening insoles for graduating to shoelessness.
For the last three weeks I've gone hiking barefoot. The idea came to me at the end of a trail. Shoes were already off to wade in a cryogenic stream. The trail was about a mile and a half long, covered with sharp cubic quartzite gravel. It made for some slow going. Speed didn't come natural.
Which was good, because it made an otherwise short hike last longer. Instead of waiting in the parking lot, I was waited-for- at least for a couple minutes.
The next week was similar. About two miles total over a mix of gravel, scree, talus, and- toward the end- across the forest floor. My feet were sore after that one too. I was the slowest poke around. Again, a short hike made more substantial by barefooting it.
This last weekend, I hiked about 3.6 miles. This trail was through a pine forest, occasional sand, gravel, snakes (x2), and stone outcroppings. This week I didn't just hike, I jogged, I ran. I kept ahead of other shoe-wearers. I was no kind of slowpoke.
And my feet were about as sore as they'd been the previous two weeks. Not too bad.
Today I bought a single 3-tab shingle asphalt composite shingles from Home Depot. It traced my foot, cut off half my big toe (on the cut-out, not the toe itself) and made myself a pair of gravel-covered insoles to use without socks.
The shingles probably won't last a day before I wear all the gravel granules off. The combination of heat and friction will, doubtless, make short work of them.
What I need is a pair of durable, rough-gravel insoles that won't degrade from the heat typical to the human foot. If I can toughen my feet up on odd-numbered days, and maintain that toughness even when I'm not hiking barefoot, then going barefoot when I want to would be far more appealing. Instead of being an exercise in pain management, I'd be able to focus on the unique sensory experience of being in touch with the ground.
Is it strange to want to go barefoot? No, not really. Barefoot is healthy. It allows your feet and gait to take their natural shape. Going barefoot causes you to adapt to your surroundings, distribute your weight, tread lightly. Instead of pounding on your heels and jarring your knees, barefooting makes you glide, naturally. Vibram, of shoe tread fame, makes shoes that mimic the look and feel of going barefoot, called FiveFingers. They literally have five little toes. I admire the concept. For people who want to wear shoes, who don't want to experience the pain or risk of going shoeless, or who want to go out in hot or cold weather (shoeless even on white concrete in the summer is torture).
So, that's the idea. Durable foot-toughening insoles for graduating to shoelessness.
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