Space Elevator

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....

"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?

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

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

On 29 Jun 2004 12:44:56 -0700, (Corrie) wrote:

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....

The debris field, however, will be quite immense.
--
dillon

When I was a kid, I thought the angel's name was Hark
and the horse's name was Bob.

Brian Whatcott wrote:

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.

I have never noticed any motion. My mother cried when the old one went down. It
was back to waiting in line for the ferry. The original design was an upside
down U in cross section with solid sides. It didn't exactly generate lift. It
would flex a bit under a wind load (35 mph made it gallop like crazy) and twist
and dump, twist back with the U slightly facing the wind and do it again. The
real problem was harmonic oscilation. The darn thing had a harmonic mode that
could get pumped up over time with very little wind.

The replacement is all open gridwork with four wind grates in the roadway the
whole length. My brother, who is a ranger in the Tetons (was on Lou Dobbs the
other night about rescue operations), has his arrest ticket framed from the
time he walked the cable from end to end when he was a teenager.

-- Charlie Springer

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

"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

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

"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