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#51
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Richard Lamb wrote in message ...
From a PAWKI standpoint, it's probably cable tensile strength. Naw, using unobtainium cable takes care of that. The real PAWKI issue is conservation of energy. But if that held, I'd suspect this event is going to feel a lot like catching a Three Wire - at FL 450. At least you have some room to recover from the spin.... |
#52
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"Bob Chilcoat" wrote in message ...
According to the newspaper article I read, the proposed fiber is a "tape" roughly three feet wide and a few thou thick. A flat ribbon is aerodynamically unstable and will vibrate axially in any wind. This thing would seem to be the ultimate Tacoma Narrows Bridge. Just my first impression. The problem with the Tacoma bridge was that the materials couldn't handle the flexing. Lots of materials are designed to vibrate - saxophone reeds, guitar strings, etc. So what would the pitch of this critter be, and how many Db? |
#53
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On Tue, 29 Jun 2004 16:48:11 -0400, Bryan Martin
wrote: // The designers of the Tacoma-Narrows bridge didn't give enough consideration to its aerodynamics or stiffness. It shouldn't have been flexing to that degree at all. It was a solid road deck built from I-beams in an area known for frequent high winds. Modern suspension bridges are usually built from steel trusses for stiffness and have open steel grid decking down the middle of the span to kill any lift generated by the roadway. It's not a kind site. The current bridge there gallops too a little, in high winds. Brian W |
#54
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Just for clarity, how tall is this thing supposed to be?
I saw on proposal that said 62,000 miles! If that's supposed to be anchored to the Earth, I gotta belly laugh. Anybody want to calculate the rotational moment of something THAT long????? Richard |
#55
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#56
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#57
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I missed part of the thread, but the whips are an idea of the late brilliant
Robert F. Forward. I think Tether's Inc. is still going. The idea is that a mass orbits at a reasonable height. Two or three long whips rotate at such a speed that if they where a wheel, it would be rolling on an imaginary sphere that matched the globe that would fit the intended intercept altitude. Just like the wheel of a car, at the lowest point it is not moving with respect to the Earth. If the end is flyable, the slack or flexibility allows it to station keep or more on some course and speed to perform the intercept. The timing has to be good, like 20 or 30 seconds, but lining it all up is pretty predictable. The whip is kept powered up by delivering material from space back to Earth. Forward worked out a series of transfer whips that would allow travel to Mars without carrying any more than maneuvering fuel. The ship or attachment has to be able to travel on the whip in order to change angular speed (by moving the mass closer to or further from the release points. Or delivering the load to the central mass.) I can pull out his papers and elucidate if anyone wants more. We exchanged copies of everything we had published once. I sent some letters to the editors of journals and tech magazines. He sent a big box of Hughes Research internal papers, patents, Omni articles, Physical Review papers, etc. (Included is the famous "Rotating Cylinders and the Possibility of Global Causality Violation.") Forward thought up a lot of great stuff. NASA uses his space-time flatteners for micro-gravity research on the Shuttle. He invented the third of the four basic instruments for testing or measuring gravity, the Rotating Gravity Gradiometer. (I invented the fourth, which required his as a detector). We used to talk occasionally. His death from a brain tumor in his 60's was a major loss. -- Charlie Springer |
#58
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"Felger Carbon" wrote in message ink.net...
"pacplyer" wrote in message om... Inertia: a property of matter whereby it remains at rest or continues in uniform motion unless acted upon by some outside force. The uniform motion in my example was acceleration. Disclaimer: It's 5:30AM. I'm an engineer, not a physicist. BUT... Acceleration **by definition** is **not** uniform motion! ;-) Yeah, I've heard all this befo "Dammit Jim, I'm a doctor, not an engineer!" and "Captain, I cannot change the laws of physics!" My reply: I'm getting a little bit tired of my senior crewmembers conspiring against me! The superstructure can do those things in a jacked-up simulator, understand? It's aviation, but not as we know it. The main thing here is the Enterprise Carrier (NASA 747) is the most capable ship in the fleet and if we can somehow harness the power of those new GE big fan engines by setting them up on the existing airframe... We just might get off this rotten planet! Now get to work on the tether drag calculations! I don't want to hear any more excuses! (yeah, something like that'll suffice... After all, this is a high altitude space thread.) ;-) pac "suffering from hypoxia" plyer |
#59
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On Mon, 28 Jun 2004 20:23:11 -0700, Tim Ward wrote:
Stall speed at extreme altitude would not the benign 180 knots, but something appreciably higher (can you help me out with the high altitude 747 data - actual stall speed at FL 450?). I actually want to fly the 747 pretty fast. If its speed at 45000 feet is fast enough so that the spacecraft's airspeed at 100000 feet is at the spacecraft's best rate of climb speed, then the turning maneuver isn't required. pacflyer gave a 1g speed range for the 747 at 45,000 ft and 580,000 lb of 208 kt to 251 kt. I'm assuming those numbers are in KCAS. If so, that works out to 444 KTAS to 524 KTAS under standard day conditions. At 100,000 ft, those same true airspeed values work out to 56 KCAS to 68 KCAS. The equivalent airspeed, which is what the wing sees, is a bit lower at 52 KEAS to 61 KEAS. That means the orbiter needs to have a very, very low wing loading, which doesn't seem compatible with a re-entry. And it has to support the weight of the tether too. I'm not sure this idea will work, unless we can get a much faster tow aircraft. -- Kevin Horton RV-8 (finishing kit) Ottawa, Canada http://go.phpwebhosting.com/~khorton/rv8/ e-mail: khorton02(_at_)rogers(_dot_)com |
#60
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"Kevin Horton" wrote in message news On Mon, 28 Jun 2004 20:23:11 -0700, Tim Ward wrote: Stall speed at extreme altitude would not the benign 180 knots, but something appreciably higher (can you help me out with the high altitude 747 data - actual stall speed at FL 450?). I actually want to fly the 747 pretty fast. If its speed at 45000 feet is fast enough so that the spacecraft's airspeed at 100000 feet is at the spacecraft's best rate of climb speed, then the turning maneuver isn't required. pacflyer gave a 1g speed range for the 747 at 45,000 ft and 580,000 lb of 208 kt to 251 kt. I'm assuming those numbers are in KCAS. If so, that works out to 444 KTAS to 524 KTAS under standard day conditions. At 100,000 ft, those same true airspeed values work out to 56 KCAS to 68 KCAS. The equivalent airspeed, which is what the wing sees, is a bit lower at 52 KEAS to 61 KEAS. That means the orbiter needs to have a very, very low wing loading, which doesn't seem compatible with a re-entry. And it has to support the weight of the tether too. I'm not sure this idea will work, unless we can get a much faster tow aircraft. -- Kevin Horton RV-8 (finishing kit) Ottawa, Canada http://go.phpwebhosting.com/~khorton/rv8/ e-mail: khorton02(_at_)rogers(_dot_)com Ahh... at last someone who did what I was too lazy to do... the numbers. I knew the indicated airspeed at 100,000 feet would be low. If I can ask a favor, what is the equivalent airspeed at Mach 1 at 100,000 feet, standard atmosphere? And hey, I've already figured on dropping 20 km of tether, what's a wing between friends? Tim Ward |
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