Posts by Jon Minhinnick 31 publicly visible posts • joined 22 Oct 2007
It doesn't go directly downwind but at an angle to it. The apparent wind then becomes the vector sum of the craft's motion plus the wind's. This new vector can have a scalar velocity greater than the original wind itself. Since the craft is propelled by the apparent wind, it effectively generates its own wind and sails in that.
If you observe (say) America's Cup racing you'll see that the boats are always sailing about 45 deg to the wind, both upwind and downwind. This is the most efficient angle. To understand it fully, do a google for Polar Curves and Velocity Made Good. Some good stuff at Sailplanner.net.
Hey, NZ's not so bad... it's only a 3-hour flight to the West Island and it's only 30 hours door-to-door Auckland to London. We're practically neighbours! Our Prime Minister is atheist or at least very agnostic. We can effectively close our borders the next time an asian chicken gets a nasty cough. And we use proportional representation when we vote every 3 years. Keeps 'em reasonably honest.
"Gartner: boosting core counts to take advantage of Moore's Law is gonna run out of gas"
"Wiki: the number of transistors that can be placed inexpensively on an integrated circuit has increased exponentially, doubling approximately every two years"
Gartner: Wrong. Moore's Law says nothing of the layers taking advantage of the integrated circuit, it *only* applies to the transistor count.
The rest of their report may or may not be relevant.
I haven't seen it for myself, but I understand that some glider pilots on the west coast beaches of Auckland, NZ sometimes will peel off the ridge lift, perform a touch-and-go on the beach, and return to the ridge lift again. I'm told it scares the heck out of the hang-glider pilots!
YMMV.
"the glasses they use are simply polaroid glasses but with the lenses polarised horizontal and vertical."
Nitpicking, but they're actually at +45 and -45 degrees, not 90 and 0. This is because projected light reflecting off the Imax screen will predominantly be polarised in a vertical or horizontal plain depending on where you're sitting in the theatre (think glare off water or snow), in addition to the encoded polarisation used for the 3D effect. Using the +-45 filters means both eyes will filter the glare equally and prevent shimmer between eyes.
"The holy grail here is a flexible, colour display with notebook screen brightness and resolution"
Nope. Almost every book in any library has monochrome text. None of the books in the library are backlit. Most of the books have a printed resolution less than any modern LCD. LCDs don't work in bright light.
We're talking about e-paper here, not a flexible LCD replacement. We're almost there. Tell the boffins to get on with it!
... and blackhole them. If the user cares, they'll fix it themselves. If not, they stay blackholed. And because they're mainly home users with dynamic IP addresses, refresh the blackhole list once a week. Oh, and notify their ISPs so when the user rings up, there's a listed reason they've been sent to dev/null.
Hmmm... what if webservers also use the same blackhole list, so they don't serve to spamming machines. Then, the user would really care about getting back online. Just send back a page to the user that the requested page will only be displayed if they remove their bot.
How many times have you left the store and set off the (conventional) security detectors even though you've paid and had the tags "deactivated"? By that token, some RFIDs will still be live upon departure and cause merry havoc walking back in later...
But here's a way to have fun with it at home- all you require is your socks and undies tagged, then install a sensor at your front door: Beep! Beep! You Have Worn Those Underpants Three Days In A Row! You Are At Risk of Jock Rot! Beep! Beep! You Have Mismatched Socks! Please Return To Your Bedroom To Change! Beep! Beep! Your Lost Sock Is Located Under Your Bed! Your Cat Is In The Scotch Chest, Third Drawer Down!
Has anybody got a handheld RFID scanner? I can't seem to find my coat...
... when you put your hand on a van der Graaf generator, and point your finger at the (turned on but unlit) bunsen burner. Crack! Poof! Now lit.
And the lithium (then sodium, then potassium) in water. And wondering what would happen if you got some toluene and nitrated it. And those balloons of hydrogen/oxygen (2:1 mix)
Science is fun!
I have a 5" metal plate in my leg holding my knee together, and screws in it the size of my little finger. Goes fine through scanners at the airport.
But I carry the Dr's certificate just in case.
It's the terahertz wave scanners that worry me... what do they do to pregnant women?? (Or more specifically, their babies)
(Getting slightly off-topic here)
All fixed-wing aircraft (gliders, powered planes) obtain lift by moving air over their wings. Power aircraft do this using thrust from an engine to move fowards. Gliders do this by converting their potential energy (height) into kinetic energy (speed forwards). In a glider, you are always descending through the air, and the trick is to find air that is going up faster than you're going down.
If a pilot talks of a stall, they mean a wing stall, otherwise they would say "compressor stall" for a turbine engine, and piston engines never stall because they are never heavily loaded at very low RPM (except for prop strikes. Ha.) They would however stop due to other problems, and those are lumped into "engine failures" or something else. Other stalls are elevator and rudder stalls. These are much more rare.
Christopher Emerson is right to say there are different kinds of wing stalls, and I was simplifying in my original post. I have plenty of times practised stalling, of the "mush" variety where you waft through the air, stick fully back, nose still high and losing a lot of height, and also the fully developed stall, where the nose drops as the wings no longer support the aircraft at all, you end up looking straight down at the ground which is rushing up to meet you fast. Ironically, when the nose drops in a full stall, the correct action is to push the nose even further down to get the wings flying again.
And then there are high-speed stalls (tight turns pulling g), incipient spins and full spins (only ONE wing is stalled), and stalls due to wind shear (turning steeply low to the ground). Rudder stalls if you are outside your C of G load limits (flat spins etc) and I have no idea how to recover from an elevator stall!
I also suspect that because a 777 is tuned for high-speed flight (cruise at mach 0.84 iirc) it would develop its low-speed stall fairly quickly. Can anyone see if the 777 has its flaps down? I'm meeting a couple of Lufthansa pilots (one Airbus, one Boeing, both glider) for dinner tomorrow night, I'll see what they say.
Chris is sort of right... if the plane stalled (and although a quick google didn't find it for me, it would just need to drop its airspeed below say 100 kt) then the plane WILL fall, and whatever forward speed it had at the time would just describe the shape of the parabola. The vertical descent is still entirely due to gravity.
When a wing stalls, it *stops* flying. If that happens, you need to hope you've got enough altitude to recover, and I don't know of anything that will do this at 30'.
@ Ru: Learning how a wing loses lift is an exercise left to the poster.
@ Geoff: 9.81 m/s/s is also known as g, the acceleration due to gravity on the Earth's surface. A stalled plane does, in fact, drop *exactly* like a brick.
Been there, done that, filled in the CAA accident report. (I stalled my glider on from 5', and that was unpleasant enough)
A pilot of that calibre would of course be careful to keep enough speed on for a climb out as well as the flyby. Go and watch a gliding competition where a pilot will fly their sailplane in from the last turnpoint, 50 km away at Vne (Velocity never exceed), dump their water ballast and fly through the finish line at 30' and 120 kt, then haul back on the stick, climb back to 1000', join the downwind circuit for a normal landing. Magic.
Helicopter icon because stalling those things is the stuff of nightmares.
Remember when the French govt bombed the Rainbow Warrior in Auckland in 1985? Yes, state-sponsored terrorism. Against a friendly nation. The perps were pretty quickly caught, tried and found guilty. Put into prison. And then the pressure started. France threatened trade sanctions (big force in the EU, where NZ sells its butter) and the terrorists went to live on a (French) Pacific atoll. For a while, anyway, until they came home to France to a hero's welcome.
So we have not just innocents disappearing, but proven guilty terrorists also being removed and never coming back. The USA is an even bigger economic superpower (excluding sub-prime mortgages!) and they will just take what they like. You've got something America wants? Get used to losing it.
The criticism of the Prius is that it is only as efficient as a good diesel car. The criticism of lead-acid batteries is that they don't have a high peak power output. The criticism of supercaps is they don't have the energy density of batteries. So, why not:
Have a smallish diesel motor, use it (a la the Prius) to power the wheels when needed and to charge the batteries in a managed fashion (rather than dumping the regeneration load into them say), and use the supercaps to provide that extra bit of oomph for the really sharp power demands. Regenerate into the supercaps. There'd be no real extra complexity than the current Prius except for perhaps a circuit to manage the load between the batteries and the supercaps. And that would probably be less than a dozen components...
Now, if anyone tries to patent this, can someone point this post out as prior art...
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