h a l f b a k e r yWarm and Fussy
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UPDATE: I've proven that the idea described below is impossible even with todays strongest materials. See annotations.
Currently launching things into space uses is extremely polluting and uses vasts amounts of fuel.
If we can build a gigantic trebuchet with modern materials (carbon fiber) that
can fling things into space we could have a clean space program. It could even be wind powered.
I would like the giant trebuchet to be built in an underground chamber that is under vacuum. That way there will be no air resistance until the projectile leaves a small trap door on top of the chamber.
A trebuchet is superior to a cannon because the acceleration occurs over a longer period of time and is thus more gentle.
Sling
http://www.skidmore...Slingshot.nomad.jpg
The kind of sling I meant. [jmvw, Nov 01 2006]
Trebuchet range calculator for Apple and Windows
http://www.algobeautytreb.com/
[jmvw, Nov 01 2006]
And the mathematics behind the range calculator...
http://www.algobeau....com/trebmath35.pdf
Discusses the mechanics behind a number of Treb variations. [zen_tom, Nov 02 2006]
Space shuttle emissions
http://www.madsci.o...973014746.Es.r.html
Page seems to downplay pollution of space shuttle. [jmvw, Nov 02 2006]
Spreadsheet of simple sling model
http://spreadsheets...Lotn6obSNEs-IGLWwIg
You'll need to set up a google account for this. [jmvw, Nov 03 2006]
momentum exchange tethers
http://www.tethers.com/MXTethers2.html
ok, so it's not underground but who cares [fenn, Mar 22 2008]
more formulas
http://yarchive.net...sling_launcher.html
some more discussion of ground-based slings [fenn, Mar 22 2008]
rotovator to orbit without rockets
http://www.tethers....HASTOLAIAAPaper.pdf
fly fast enough and an orbiting skyhook can grab you. [fenn, Mar 22 2008]
[link]
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“Give me a place to stand and a lever long enough and I will move the world”
Archimedes, 220 BC
I would be interested to know just how long the lever would need to be.
The mass of the weight would also be a a not insignificant consideration.
The irony is that the HB tagline that fell on this idea was "Faster than a Stationary Bullet"
Oh how I miss Bristolz!. I can imagine the picture but have no way of rendering it. |
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careful, here be [carbon fiber magic] dragons. |
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Magic? Maybe.. it'd be fun to do some calculations on this one. If not a trebuchet, a giant sling? |
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(edited; PollyNo9, sorry, I meant a sling or shepherds sling, not a catapult) |
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It would be fun to do some calculations? You mean you haven't? |
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Alternatively, mount the trebuchet on a solar powered electromagnetic railgun, duct tape some buttered toast to the underside, and run the calculations for immersion in custard, then when the projectile hit fresh air the drop in viscosity combined with maximum velocity would cause it to accelerate beyond the atmosphere. |
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I don't know how to tackle the trebuchet, but in case of the sling.. if we'd have a line that is 1 km long, we'd have to hurl this around until it turns 16 times in 9 seconds. |
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I have not been able to find rope that is light and strong enough to do this. With a weightless rope, the force on the rope that whips a 1000kg satellite around would be 12.5 MN, but the weight of rope strong enough to do that is considerable (about 15000 kg for the rope I found) and for that we'd need a stronger rope, that is heaver and so on. With a 100 m rope, the centripetal force would be 125 MN and with a 10 km rope it would be 1.25 MN |
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egberts method may work better. |
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//Give me a place to stand and a lever long enough and I will move the world”
Archimedes, 220 BC// far be it for me to disagree with old Archimedes but where exactly was he figuring on standing when he was gonna shift the world? |
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He leaves that to you when he asks for a place to stand. What he fails to ask for is a suitable fulcrum point about which he can develop a moment. |
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Hang on, let me develop a moment. |
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I just take mine to Boots. |
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You could determine the ideal position with an Arial. |
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//far be it for me to disagree with old Archimedes but where exactly was he figuring on standing when he was gonna shift the world?//
On a turtle. The earth was supported by a giant turtle in those days, so he’d have to find two more turtles--one for himself and another for his pivot point. |
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Meaning that should anyone have wanted to move the Earth back in those days, rather than faffing about with levers and pivots, all they actually needed was a big enough piece of lettuce. |
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//Currently launching things into space uses is extremely polluting// Really? In what way exactly? Which materials are released into the environment and in what quantities? |
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It's not extremely polluting. |
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Perhaps. I found a page that claimed it isn't, see link, but that page also talks about water and CO2 as the only combustion products of kerosene, which doesn't seem entirely accurate. Either way, the amount of fuel consumed is humungous. The CO2 production is huge and today this is a considerable pollutant. |
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I doubt emissions of space launches have been researched as well as automotive emissions or if emissions were ever measused. |
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Having to lift all of the fuel required for launch accounts for a large percentage of, well, the fuel required for launch. However, even eliminating this, you're still trying to get out of a rather large gravity well. A trebuchet would be a big improvement, but still fairly profligate in terms of energy usage. |
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Phlish, my intuition tells me you're right, but I am unable to verify this. I did verify it for the sling and there seems to be no rope that even comes close to having a sufficiently high strength/mass ratio. |
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... and since a trebutchet is, in fact simply an enlarged version of the staff sling, the materials needed would be quite similar. |
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I'm guessing that if you put this in a vacuum, that would be a big vacuum area, and opening the door for the projectile to fly out might cause a draft strong enough to stop the projectile. Even if not, creating such a vacuum is likely to cause more problems than it solves. |
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A better solution might be to build the trebutchet on a very tall platform... or figure out some way to loft it by blimps... to an altitude where the wind resistance is significantly less. |
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An even better solution might be to reserve trebutchet space programs for smaller airless worlds, such as the moon... or oen of the moons of Mars anyway. |
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I would point out that since the trebutchets are gravity powered via counterweight, there is a very real question as to whether or not the gravity used to pull one object down can be used to leverage another object beyond orbit at all. |
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I did some additional calculations and was able to prove that this idea actually is impossible, even with carbon fiber. |
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I used a simple model that assumes a long round stick with a point mass satellite at the end that is whipped around and flings the satellite away. I found out that even carbon fiber does not have sufficient tensile strength to do this. The mass of the boom itself is always sufficient to tear it apart. |
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Considering that this is impossible, a trebuchet, which arm will not have less weight or more tensile strength is also impossible. |
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For those interested, I made my spreadsheet available in Google spreadsheets. See the link. |
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ye_river_xiv, my model is what you called a staff sling. |
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//I would point out that since the trebutchets are gravity powered via counterweight, there is a very real question as to whether or not the gravity used to pull one object down can be used to leverage another object beyond orbit at all.// |
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I don't see why not (given less gravity). Just use a long enough boom and enough weight. Our restriction on earth is in material strength. |
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I think I'll let a next idea "very tall tower" pass for now. |
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ATTENTION: Would the next person to make it into orbit please toss us down a line? Thanks! |
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I was thinking one could do this in
stages, with a very (very) large treb
hurling up a smaller one, which in turn
hurled a smaller one, and they told two
friends, and so on and so on. But I do
not think that a flying trebuchet will
fling anything - all parts are moving
together, and so there is no difference
to harness. |
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Not only is this not impossible, it's quite feasible. Much more feasible than the silly space elevator, to the point of being possible to construct and launch with today's materials. The general idea is known as a momentum exchange tether. See tethers.com link |
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Not wind powered, but solar powered.
There's even a neat animation on that page showing the tether picking up a payload mass and flinging it into a higher orbit. |
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With some modest improvements in material strength to weight ratio, the tether could pick up items from the Earth's surface. |
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Yeah! and that vacuum is gonna seal itself. |
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//extremely polluting and uses vasts amounts of fuel// Couldn't we just fit the Space Shuttle with a catalytic converter? Hybrid space shuttles maybe? |
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