What could possibly go wrong?

On Wednesday, January 16, 2013 12:14:36 PM UTC-6, Bill D wrote:

"Plausible as a last resort. Lets look at the acceleration and rotation phase. 1G acceleration is 19 knots per seconds per second so let's set Vr at 100 kts and Vy at 120 kts. The glider would lift its nose wheel in 5.25 seconds and lift off in about 6 seconds. Vy would be achieved in 6.3 seconds. Vr would be reached in about 130 meters or 430 feet, Vy in about 200m or 656 feet. Assuming you start with a 10,000' runway, that leaves about 9300' left to land and stop straight ahead from 120 knots. You might be able to do this up to a height of 1200 feet AGL given good glide path control devices. Of course, the runway would have an over run braking surface at the departure end plus maybe, arresting wires. Above that, if the glider L/D is high enough, a circle-to-land maneuver should be possible. Do I think this is actually possible? With the right glider design, absolutely. I hope the Dillingham guys will put a winch on a boat and try for an altitude record as a proof of concept."

Minor and forgivable glitch, Bill. Knots is already velocity. Knots per second is acceleration. You said knots per second per second. That is rate of change of acceleration, or "onset". I won't use the other term, as some might think I am snarking at you.

Your boat will have to be anchored, or there will be many HP expended keeping it in place during the climb. So, no initial launch acceleration by having the boat moving. Dang it.

Ture airspeed as altitude increases? 200 feet per second true going through FL200 won't be much indicated airspeed. So, your rope speed will keep going up as the climb progresses. Try to take advantage of the wind aloft. Maybe you can reduce this effect?

You probably will start seeing significant horsepower lost due to the rope being dragged through the air by the glider, and it probably will have a lot more of a catenary. Yeah, tension will be high, but so will drag. And also, the weight will not be insignificant as far as power to lift the rope goes. How much will 15 miles of that 3.625 inch Amsteel blue weigh?

Things change a lot when looking at the horsepower required to lift and drag 20 lbs versus thousands of pounds. Percentages may be nearly the same, but absolute values are not. I think your fuel consumption estimate is low, Bill. :-)

And while we are talking of far out concepts, I still like the idea of being above the jet stream and dropping a chute on a long rope down into it. It starts out falling behind you, but once the chute is in the high velocity "core" of the jetstream, you turn around, allow the chute to inflate and if the gradient is high enough and your plane can fly slow enough, the chute can drag you "downwind."

On Wednesday, January 16, 2013 2:52:14 PM UTC-7, Steve Leonard wrote:
On Wednesday, January 16, 2013 12:14:36 PM UTC-6, Bill D wrote:



"Plausible as a last resort. Lets look at the acceleration and rotation phase. 1G acceleration is 19 knots per seconds per second so let's set Vr at 100 kts and Vy at 120 kts. The glider would lift its nose wheel in 5.25 seconds and lift off in about 6 seconds. Vy would be achieved in 6.3 seconds. Vr would be reached in about 130 meters or 430 feet, Vy in about 200m or 656 feet. Assuming you start with a 10,000' runway, that leaves about 9300' left to land and stop straight ahead from 120 knots. You might be able to do this up to a height of 1200 feet AGL given good glide path control devices. Of course, the runway would have an over run braking surface at the departure end plus maybe, arresting wires. Above that, if the glider L/D is high enough, a circle-to-land maneuver should be possible. Do I think this is actually possible? With the right glider design, absolutely. I hope the Dillingham guys will put a winch on a boat and try for an altitude record as a proof of concept."



Minor and forgivable glitch, Bill. Knots is already velocity. Knots per second is acceleration. You said knots per second per second. That is rate of change of acceleration, or "onset". I won't use the other term, as some might think I am snarking at you.



Your boat will have to be anchored, or there will be many HP expended keeping it in place during the climb. So, no initial launch acceleration by having the boat moving. Dang it.



Ture airspeed as altitude increases? 200 feet per second true going through FL200 won't be much indicated airspeed. So, your rope speed will keep going up as the climb progresses. Try to take advantage of the wind aloft. Maybe you can reduce this effect?



You probably will start seeing significant horsepower lost due to the rope being dragged through the air by the glider, and it probably will have a lot more of a catenary. Yeah, tension will be high, but so will drag. And also, the weight will not be insignificant as far as power to lift the rope goes. How much will 15 miles of that 3.625 inch Amsteel blue weigh?



Things change a lot when looking at the horsepower required to lift and drag 20 lbs versus thousands of pounds. Percentages may be nearly the same, but absolute values are not. I think your fuel consumption estimate is low, Bill. :-)



And while we are talking of far out concepts, I still like the idea of being above the jet stream and dropping a chute on a long rope down into it. It starts out falling behind you, but once the chute is in the high velocity "core" of the jetstream, you turn around, allow the chute to inflate and if the gradient is high enough and your plane can fly slow enough, the chute can drag you "downwind."

Thanks for the comments, Steve. Of course, you're right 1G is 19 knots/sec..

However, rope speed must sharply be reduced as the glider enters the climb - and even more if there are headwinds otherwise the glider over speeds. I suspect the true airspeed effect would be more than offset by upper winds..

15 miles = 269,280 lbs However, since the rope is getting shorter as you climb, you wouldn't have to lift that much. Drag is more important than weight. You'll gain a bit of Cd on Reynolds number compared to the thin .188" diameter rope commonly used in glider winches.

Actually, I assumed full HP for the whole launch but it will have to be backed way off in the upper half. Tension stays constant but HP doesn't since rope speed has to drop to avoid over speeding the glider. (Water skier effect) I think I probably over estimated the fuel.

A big ocean going tug like the "Far Sampson" could be the ideal platform. It could maintain position with its monster engines. If that turns out to be a problem, a big sea anchor would be the next option. The big Sultzer diesel might not be the best choice for 10 minutes of power. A gas turbine might be a better choice.

On Wednesday, January 16, 2013 6:06:59 PM UTC-6, Bill D wrote:
On Wednesday, January 16, 2013 2:52:14 PM UTC-7, Steve Leonard wrote:

On Wednesday, January 16, 2013 12:14:36 PM UTC-6, Bill D wrote:







"Plausible as a last resort. Lets look at the acceleration and rotation phase. 1G acceleration is 19 knots per seconds per second so let's set Vr at 100 kts and Vy at 120 kts. The glider would lift its nose wheel in 5.25 seconds and lift off in about 6 seconds. Vy would be achieved in 6.3 seconds. Vr would be reached in about 130 meters or 430 feet, Vy in about 200m or 656 feet. Assuming you start with a 10,000' runway, that leaves about 9300' left to land and stop straight ahead from 120 knots. You might be able to do this up to a height of 1200 feet AGL given good glide path control devices. Of course, the runway would have an over run braking surface at the departure end plus maybe, arresting wires. Above that, if the glider L/D is high enough, a circle-to-land maneuver should be possible. Do I think this is actually possible? With the right glider design, absolutely. I hope the Dillingham guys will put a winch on a boat and try for an altitude record as a proof of concept."







Minor and forgivable glitch, Bill. Knots is already velocity. Knots per second is acceleration. You said knots per second per second. That is rate of change of acceleration, or "onset". I won't use the other term, as some might think I am snarking at you.







Your boat will have to be anchored, or there will be many HP expended keeping it in place during the climb. So, no initial launch acceleration by having the boat moving. Dang it.







Ture airspeed as altitude increases? 200 feet per second true going through FL200 won't be much indicated airspeed. So, your rope speed will keep going up as the climb progresses. Try to take advantage of the wind aloft. Maybe you can reduce this effect?







You probably will start seeing significant horsepower lost due to the rope being dragged through the air by the glider, and it probably will have a lot more of a catenary. Yeah, tension will be high, but so will drag. And also, the weight will not be insignificant as far as power to lift the rope goes. How much will 15 miles of that 3.625 inch Amsteel blue weigh?







Things change a lot when looking at the horsepower required to lift and drag 20 lbs versus thousands of pounds. Percentages may be nearly the same, but absolute values are not. I think your fuel consumption estimate is low, Bill. :-)







And while we are talking of far out concepts, I still like the idea of being above the jet stream and dropping a chute on a long rope down into it.. It starts out falling behind you, but once the chute is in the high velocity "core" of the jetstream, you turn around, allow the chute to inflate and if the gradient is high enough and your plane can fly slow enough, the chute can drag you "downwind."



Thanks for the comments, Steve. Of course, you're right 1G is 19 knots/sec.



However, rope speed must sharply be reduced as the glider enters the climb - and even more if there are headwinds otherwise the glider over speeds. I suspect the true airspeed effect would be more than offset by upper winds.



15 miles = 269,280 lbs However, since the rope is getting shorter as you climb, you wouldn't have to lift that much. Drag is more important than weight. You'll gain a bit of Cd on Reynolds number compared to the thin ..188" diameter rope commonly used in glider winches.



Actually, I assumed full HP for the whole launch but it will have to be backed way off in the upper half. Tension stays constant but HP doesn't since rope speed has to drop to avoid over speeding the glider. (Water skier effect) I think I probably over estimated the fuel.



A big ocean going tug like the "Far Sampson" could be the ideal platform. It could maintain position with its monster engines. If that turns out to be a problem, a big sea anchor would be the next option. The big Sultzer diesel might not be the best choice for 10 minutes of power. A gas turbine might be a better choice.

Can't help myself but I have to add a 'political' comment: If we were on the metric system errors as made above would be unlikely. When oh when will this country ditch the silly medieval units of measure we use (and nobody else) and join the world and scientific community?
Herb

On Jan 16, 6:06*pm, Bill D wrote:

Thanks for the comments, Steve. *Of course, you're right 1G is 19 knots/sec.

However, rope speed must sharply be reduced as the glider enters the climb - *and even more if there are headwinds otherwise the glider over speeds. *I suspect the true airspeed effect would be more than offset by upper winds.

15 miles = 269,280 lbs *However, *since the rope is getting shorter as you climb, you wouldn't have to lift that much. *Drag is more important than weight. *You'll gain a bit of Cd on Reynolds number compared to the thin .188" diameter rope commonly used in glider winches.

Actually, I assumed full HP for the whole launch but it will have to be backed way off in the upper half. *Tension stays constant but HP doesn't since rope speed has to drop to avoid over speeding the glider. (Water skier effect) *I think I probably over estimated the fuel.

A big ocean going tug like the "Far Sampson" could be the ideal platform. It could maintain position with its monster engines. *If that turns out to be a problem, a big sea anchor would be the next option. *The big Sultzer diesel might not be the best choice for 10 minutes of power. *A gas turbine might be a better choice.


Rope speed must be reduced on a NORMAL winch launch, where there is
not much density change between start and ending altitude. Remember.
This is NOT a normal launch we are talking about. And the wind
doesn't always blow, so you won't always get that effective horsepower
and the winch speed may have to increase at some point in the launch.
Agree that speed will hit a high right at rotate, and slow some from
there. But when you are talking of climbing to where air density is
just a fraction of what it is at launch, you may well be reeling in
the rope considerably faster for the last half of the launch than you
are at lift-off.

There is also the matter of accelerating a quarter of a million pounds
of rope in addition to the half million pounds of plane. And by the
way, the article references a paylod of 490,000. That is not the
total weight of the glider and payload package! Ugh! In your normal
winch launch of a 1000 lb glider, you aren't having to accelerate 500
lbs of rope, so you have an easier time accelerating the system.
There are scaling effects that have been missed in the first brush.
But, that is OK. It is fun to think about.

And you may get a Cd advantage, but you are still dragging something
through the air that is almost 20 times the diameter at over twice the
glider flight speed. So, your Cd may be down a hair, but your total
drag is going to go up a bunch. Even in terms of percentage of total
system. Again with that scaling. And again, drag is likely more
important than weight when the weight of the rope is less than 1 or 2%
of the weight of the glider. When the weight of the rope is 50% of
the weight of the glider, it is a whole other story.

Still think you have under-estimated the fuel consumed.

Now, how can you possibly claim that if the boat is using its engines
to hold position, that it is not fuel consumed for the launch? Just
drop the anchor and be done with that part of it! :-)

Enough of this semi-technical talk. This is, after all,
Recreation.Aviation.Soaring. The place where people bash the SSA
Rules committe for not adopting the IGC Rules, talk about how ugly the
PW-5 is, and in general, just waste time.

Steve
(Kill-Joy)

I for one do not find the PW-5 to be ugly.

On Wednesday, January 16, 2013 11:18:06 PM UTC-6, Tony wrote:
I for one do not find the PW-5 to be ugly.

You, sir, have broken your glasses and are wearing Beer Goggles!

In article ,
Vaughn wrote:

On 1/15/2013 4:28 PM, Ralph Jones wrote:
http://www.networkworld.com/community/node/82160

NASA has been working on similar concepts for years. The Eclipse Tow
Launch Demonstration Project actually towed an F-106 behind a C 141 in
1998. http://www.nasa.gov/centers/dryden/p...S-049-DFRC.pdf

This was to validate the Kelly Space and Technology Eclipse Astroliner
Tow-Launch Concept which featured a low aspect ratio rocket glider as a
launch vehicle towed behind a (guess what), 747.

http://www.kellyspace.com/launchvehicle2/

There used to be video of the C 141 towing the 106. They used a very
long tow line and a low tow position IIRC. The rather beefy towhook was
mounted on top of the 106 nose. The advantages to a tow launch we (1)
Engine nozzle(s) on the spaceplane would be optimized for high altitude
operation; (2) Less fuel needed for launch (3) Lower landing gear mass.
Landing gear mass has been one of the bigger design problems for
horizontal takeoff spacecraft.

During a discussion of this with some engineers and actual rocket
scientists, I (and others before me, apparently) suggested that not only
should the spacecraft be attached to the first stage by a towline, the
towline should, in fact, be a refueling boom. Got the idea from fighter
jocks telling stories about fighters being towed by tankers as an
emergency operation. With minimal, or no fuel on board, the towed
spacecraft would be extremely light since it would be mostly empty fuel
tanks. Fuel would be transferred after reaching a safe(r) altitude. This
would also allow for even lower landing gear mass.

--- news://freenews.netfront.net/ - complaints: ---

On Thursday, January 17, 2013 10:12:21 AM UTC-6, Steve Leonard wrote:
On Wednesday, January 16, 2013 11:18:06 PM UTC-6, Tony wrote: I for one do not find the PW-5 to be ugly. You, sir, have broken your glasses and are wearing Beer Goggles!

i got new glasses!

On Thursday, January 17, 2013 1:24:26 PM UTC-6, Tony wrote:

i got new glasses!

But you are still wearing the beer goggles, Tony!

And to WB, I have seen the video, too. Found a video o fa takeoff, but nothing in flight. They did get some interesting dynamics when in high tow.

And, you would probably need two "ropes" back to the rocket if you wanted to fuel it once you got to altitude. Rockets generally get fuel and oxidizer and you really don't want them mixed before they go into the combustion chamber. Thus, a need for seperate fuel lines from the tanker.

Tony wrote:
On Thursday, January 17, 2013 10:12:21 AM UTC-6, Steve Leonard wrote:
On Wednesday, January 16, 2013 11:18:06 PM UTC-6, Tony wrote: I for
one do not find the PW-5 to be ugly. You, sir, have broken your glasses
and are wearing Beer Goggles!

i got new glasses!

Aww hell tony probably thinks a PW-2 is pretty as well :-)

Pete