It can only land in places between 53 degrees north and south latitude, because it's in a 53 degree inclined orbit...so, yes, that leaves out mostly chilly places.
The only known case of a death is a dog that was killed in Egypt in the early 20th century by a meteor.
Interesting to note that there is one death attributed to manmade space hardware: a cow in Cuba in the 1960's. I believe the US government wrote Castro a check.
Indeed, the danger from small objects is trivial, simply because the fraction of the Earth's surface that has human flesh on top of it is a rilly, rilly small number. As for a major asteroid impact, I think the best program to deal with that is to go outside with a bottle of your best Scotch and enjoy watching that sucker come down.
Falling satellites? No, not many. Satellites don't fall on us very often.
But rocks do. Mother Nature throws rocks at us from the sky every day, and some of them survive the atmospheric heating and reach the ground. Of those, some would give you a nasty bruise and some would kill you.
In 1955, a woman in Alabama was getting out of her car when a rock came through the garage roof and broke her arm. More recently, another lady was sitting at a red light when there was a mighty clang, and her car trunk was caved in by a smoking-hot rock. Those are the only ones I know of...it's a great big planet and we're little bitty people. Worry about lightning.
More to the point, Asimov imagined a world in which the populace sensibly feared the concept of intelligent robots, and forced the political class to impose those safeguards as a condition of being allowed to make them. It would appear today's populace hasn't figured that out yet.
I believe the OP is the third person I've run across on the Tubes who thought those laws existed for real...
When it's something complicated, like using a ladder, I always call a professional installer. The satellite company always send the most knowledable folks available.
I worked for years in a big operation with raised floor. The neatness up top degenerated into horror when you lifted a tile and looked underneath...raised floor doesn't eliminate the mess, just hides it from the CEO.
Whenever a guy lifted a tile and climbed down to route a cable, I'd say "Don't you bother my pet rattlesnake!" The reply would often be a bit nervous -- especially since we did indeed have rattlers at least twice.
Years ago I read an account by a British Army officer of his days leading a band of native guerrillas in attacks on the Japanese in Burma. They got all their supplies by airdrop, and had to grab the stuff and beat feet in a hurry because the airdrop would alert the enemy. Once in a while a man would be injured trying to catch a package, and one man was killed by a crate of canned pineapples.
He invented a new cause code for deaths and injuries in his logs: DFF, for Death by Flying Fruit.
Look at it this way. The number of meteorites that reach the surface of the earth is estimated at more than one per day. Most of them are very small, but none of them would fail to get your attention if they hit you. How many impacts on humans do you know of?
Consolidated, not Boeing. The Willow Run plant was built to produce B-24s.
They built cruise missiles, too. They were given a captured German V-1 and a contract to make two thousand of them...those would have been used against Japan if the invasion had come off.
Basic assumption is that as long as they are toys, the numbers and sizes will remain small...Of course, it can't be explained in a 30 second sound bite. Sorry if I have exceeded your attention span.
Try going 31 seconds and you might find a few toys like this:
Terminal velocity is proportional to the square root of the weight and inversely proportional to the square root of the area presented to the airstream, among other things.
In the terminal velocity condition the acceleration is zero. The velocity is equal to SQRT(2*W/(Rho*Cd*A)), where W=weight, Rho=air density, Cd=drag coefficient (a function of shape) and A=area presented to the airstream. Run the numbers.
Or, you could just try dropping a rock and a leaf.
Not so. A falling object will not assume a minimum-drag attitude unless it's aerodynamically stable. An arrow, yes. A badminton thingie, yes. A box, no, unless its center of mass is in just the right place. A skydiver can shape himself into a stable object for minimum drag, but an unconscious person will fall in something close to a maximum drag position. And a bullet will stay in the minimum drag attitude only as long as its rifling spin lasts: in a prolonged fall, it will go into a flat-spin mode which is the maximum drag condition.
When you say "It takes energy...", keep in mind that a high-speed air flow can giveth energy as well as taketh it away, and that energy couples into rotational motion in very complicated ways.
For an iPhone, the max drag condition would be horizontal; I just assumed an area of half what that would be. It would probably tumble, which would present about that much drag area.
Nearly all objects will hit terminal velocity within a few hundred feet, but they don't have the same terminal velocity. The back of this here envelope says an iPhone should fall at very roughly 1/3 the speed of a human body. If a skydiver "drops" it, it will actually decelerate and he will see it going up relative to him -- until he opens his parachute and it whistles past him.
No, there doesn't need to be a stationary connection.
Here's the problem the boundary layer presents: The air in the boundary layer, by definition, has zero velocity relative to the solid surface, so the only way for heat to leave the surface is by conduction across the boundary layer. (Well, I'm ignoring radiation here, but I don't think that's very much.) The thermal conductivity of air is low, so it presents a substantial thermal resistance.
The effect of the Sandia device is not to eliminate the boundary layer, as the article says, but to make it much thinner, as the PDF says. The thermal resistance of the boundary layer is approximately proportional to its thickness, so the heat transfer goes up by the same ratio. That moves the heat into the air between the impeller fins, which then proceeds to carry it overboard.
You could think of the air bearing as a layer of very slippery Arctic Silver...
Boundary layers aren't confined to air: liquid heat exchangers have them too -- but they just don't present much of a problem, because liquids have much higher thermal conductivities than air, and the heat just happily trucks on through.
No FAA inspection will be needed: after a fender-bender; this thing will not be airworthy, period. ANY ground impact will damage one or more aerodynamic surfaces. You don't call the FAA: you pay an FAA-licensed aircraft mechanic to fix it, and then you pay an FAA-licensed airframe inspector to certify the repair. You might want to look up the hourly rates those people charge...
Yes, you can leave an airplane outside in moderately bad weather...on an airport. Did you ever leave one in a parking lot?
Look at the Terrafugia in the folded-up mode. Everything on its periphery is an aerodynamic surface of one kind or another, and by automotive standards these are absurdly fragile. One parking-lot ding will ground your quarter-million-dollar machine until it's been worked over by an aircraft repair shop at aircraft repair prices.
Slashdot Mirror
It can only land in places between 53 degrees north and south latitude, because it's in a 53 degree inclined orbit...so, yes, that leaves out mostly chilly places.
rj
Hey, there's another thread today that claims non-Newtonian fluids have just been discovered...
rj
...that producers take the word of a candidate's agent when they want to know her age? And they don't, y'know, look at a picture?
rj
Sounds like Jack Sarfatti with a hangover...
rj
The only known case of a death is a dog that was killed in Egypt in the early 20th century by a meteor.
Interesting to note that there is one death attributed to manmade space hardware: a cow in Cuba in the 1960's. I believe the US government wrote Castro a check.
Indeed, the danger from small objects is trivial, simply because the fraction of the Earth's surface that has human flesh on top of it is a rilly, rilly small number. As for a major asteroid impact, I think the best program to deal with that is to go outside with a bottle of your best Scotch and enjoy watching that sucker come down.
rj
Falling satellites? No, not many. Satellites don't fall on us very often.
But rocks do. Mother Nature throws rocks at us from the sky every day, and some of them survive the atmospheric heating and reach the ground. Of those, some would give you a nasty bruise and some would kill you.
In 1955, a woman in Alabama was getting out of her car when a rock came through the garage roof and broke her arm. More recently, another lady was sitting at a red light when there was a mighty clang, and her car trunk was caved in by a smoking-hot rock. Those are the only ones I know of...it's a great big planet and we're little bitty people. Worry about lightning.
rj
More to the point, Asimov imagined a world in which the populace sensibly feared the concept of intelligent robots, and forced the political class to impose those safeguards as a condition of being allowed to make them. It would appear today's populace hasn't figured that out yet.
I believe the OP is the third person I've run across on the Tubes who thought those laws existed for real...
rj
When it's something complicated, like using a ladder, I always call a professional installer. The satellite company always send the most knowledable folks available.
Just ask Alan Harper.
rj
I worked for years in a big operation with raised floor. The neatness up top degenerated into horror when you lifted a tile and looked underneath...raised floor doesn't eliminate the mess, just hides it from the CEO.
Whenever a guy lifted a tile and climbed down to route a cable, I'd say "Don't you bother my pet rattlesnake!" The reply would often be a bit nervous -- especially since we did indeed have rattlers at least twice.
rj
Years ago I read an account by a British Army officer of his days leading a band of native guerrillas in attacks on the Japanese in Burma. They got all their supplies by airdrop, and had to grab the stuff and beat feet in a hurry because the airdrop would alert the enemy. Once in a while a man would be injured trying to catch a package, and one man was killed by a crate of canned pineapples.
He invented a new cause code for deaths and injuries in his logs: DFF, for Death by Flying Fruit.
rj
Look at it this way. The number of meteorites that reach the surface of the earth is estimated at more than one per day. Most of them are very small, but none of them would fail to get your attention if they hit you. How many impacts on humans do you know of?
rj
Isn't that the guy who duplicates your house key and passes it to his buddy who burgles your house while you're in the restaurant?
rj
Consolidated, not Boeing. The Willow Run plant was built to produce B-24s.
They built cruise missiles, too. They were given a captured German V-1 and a contract to make two thousand of them...those would have been used against Japan if the invasion had come off.
rj
RC aircraft are also restricted to ceiling height, location of use, and size/weight
http://www.rcuniverse.com/magazine/reviews/868/Mac-Hodges-B-29.jpg
Basic assumption is that as long as they are toys, the numbers and sizes will remain small...Of course, it can't be explained in a 30 second sound bite. Sorry if I have exceeded your attention span.
Try going 31 seconds and you might find a few toys like this:
http://www.rc-diecast.com/wp-content/uploads/2011/03/lanc.jpg
rj
Zu befehl.
rj
Size has no bearing
Terminal velocity is proportional to the square root of the weight and inversely proportional to the square root of the area presented to the airstream, among other things.
rj
Oh, jeez...
In the terminal velocity condition the acceleration is zero. The velocity is equal to SQRT(2*W/(Rho*Cd*A)), where W=weight, Rho=air density, Cd=drag coefficient (a function of shape) and A=area presented to the airstream. Run the numbers.
Or, you could just try dropping a rock and a leaf.
rj
Not so. A falling object will not assume a minimum-drag attitude unless it's aerodynamically stable. An arrow, yes. A badminton thingie, yes. A box, no, unless its center of mass is in just the right place. A skydiver can shape himself into a stable object for minimum drag, but an unconscious person will fall in something close to a maximum drag position. And a bullet will stay in the minimum drag attitude only as long as its rifling spin lasts: in a prolonged fall, it will go into a flat-spin mode which is the maximum drag condition.
When you say "It takes energy...", keep in mind that a high-speed air flow can giveth energy as well as taketh it away, and that energy couples into rotational motion in very complicated ways.
For an iPhone, the max drag condition would be horizontal; I just assumed an area of half what that would be. It would probably tumble, which would present about that much drag area.
rj
Nearly all objects will hit terminal velocity within a few hundred feet, but they don't have the same terminal velocity. The back of this here envelope says an iPhone should fall at very roughly 1/3 the speed of a human body. If a skydiver "drops" it, it will actually decelerate and he will see it going up relative to him -- until he opens his parachute and it whistles past him.
rj
No, there doesn't need to be a stationary connection.
Here's the problem the boundary layer presents: The air in the boundary layer, by definition, has zero velocity relative to the solid surface, so the only way for heat to leave the surface is by conduction across the boundary layer. (Well, I'm ignoring radiation here, but I don't think that's very much.) The thermal conductivity of air is low, so it presents a substantial thermal resistance.
The effect of the Sandia device is not to eliminate the boundary layer, as the article says, but to make it much thinner, as the PDF says. The thermal resistance of the boundary layer is approximately proportional to its thickness, so the heat transfer goes up by the same ratio. That moves the heat into the air between the impeller fins, which then proceeds to carry it overboard.
You could think of the air bearing as a layer of very slippery Arctic Silver...
Boundary layers aren't confined to air: liquid heat exchangers have them too -- but they just don't present much of a problem, because liquids have much higher thermal conductivities than air, and the heat just happily trucks on through.
rj
...Where do you attach this accelerometer-based apparatus when you're boinking?
rj
No FAA inspection will be needed: after a fender-bender; this thing will not be airworthy, period. ANY ground impact will damage one or more aerodynamic surfaces. You don't call the FAA: you pay an FAA-licensed aircraft mechanic to fix it, and then you pay an FAA-licensed airframe inspector to certify the repair. You might want to look up the hourly rates those people charge...
rj
Yes, you can leave an airplane outside in moderately bad weather...on an airport. Did you ever leave one in a parking lot?
Look at the Terrafugia in the folded-up mode. Everything on its periphery is an aerodynamic surface of one kind or another, and by automotive standards these are absurdly fragile. One parking-lot ding will ground your quarter-million-dollar machine until it's been worked over by an aircraft repair shop at aircraft repair prices.
rj
Oh, fer chrissake...google "Beech 1900" or "ATR-72" or "Embraer Bandeirante", among others.
rj