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I got this idea from reading a post about a one-way mission to Mars. for a way to get back from Mars to Earth would to be to include the materials necessary to make a hydrolic catapult. They would arrive on the planet (in this case mars), do whatever they needed to do, catapult together, put the part
of the rocket that is used for re-entry in the appropriate area to launch it, load everybody up, the launch at the proper angle and time. they would have to make sure all of the formulas to get back to earth are correct so they don't end up careening into the sun
P.S. I finally came up with something
Project HARP
http://www.astronau...ticles/abroject.htm
Experiments using a supergun to launch satellites in the '60s. [quantum_flux, Dec 02 2007]
Launch Ring
http://space.newsci...tes-into-orbit.html
Article about a proposed acceleration ring and ramp. 2000g so only good for non-living payloads. [marklar, Dec 03 2007]
CERN
http://public.web.c...Public/Welcome.html
Somewhere in Europe. [DrBob, Jun 17 2008]
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You came up with something, [keith]? That's great! Why don't you post it? |
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Welcome to the bakery, [keithbrunkala]. Here's your sheild, a horse to ride on, and a sword with a croissant and fishbone insignia stamped into the hilt. Now, we hear you are good with catapults so please line up our current inventory and prepare to storm the castle. |
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//hydrolic catapult//
Please define "hydrolic"
"formulas " sp. "formulae" |
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Take no notice of these pedantic spelling
corrections, [keithbrunkala], they're only
doing it to divert attention away from the
major flaw in your physics. |
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Take no notice of pedantry? Who are you and what have you done with my half-bakery? |
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A hydrolic is a watery slobbering. |
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And the horse you rode in on. |
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If there was a catapult to catapult the catapult then...it could use no fuel at all. |
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Listen to their criticisms, because frankly, whatever bones you makes ya better unless it doesn't! At least in theory that makes sense.... however, some people are naturally better at getting buns than other people are, and conversely there are natural bone eaters too. |
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I am happy with getting a bun. If I knew physics then I would tell you the "formulae", however, I am not even going to attempt in sounding smart anymore. In afterthought it probably would be some sort of cannon or something. I haven't been thinking straight lately, must have been all of the thanksgiving turkey, or just the lack of anything resembling intelligence |
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Considering this seriously, I think the physics is sound, if difficult in practice. Accelerating a spacecraft in space requires a lot of reaction mass. If you can use the planet as your reaction mass, then your spacecraft can weigh less. |
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So to make this work, what would be needed is a launcher that weighed less than the reaction mass required to achieve a similar velocity. Unlikely to be possible, even if the raw materials for the launcher were refined in situ. The total energy required is not likely to change much either. |
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[+] because I think it's built on sound logic, but I'm not sure it could be made better than a normal rocket launch (unless the launcher is used for a large number of spacecraft, one after the other, when it starts to look better). |
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OK, fair enough. I think it would work better on bodies with no significant atmosphere. You still need a power source of some kind to wind up the catapult. [+] |
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Incidentally, if i type "formulae" on this copy of Firefox, which has a built-in spellchecker, it flags it as misspelt. It also does that to "spellchecker" and "misspelt". Maybe that's American English for you. |
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I spent 30 seconds on this, so I wouldn't swear it's accurate. But say your catapult is a big boy, with a swing three times the length of a football field. And you limit the acceleration to 20 G's, so that at least some of the passengers survive. Then the max speed you can get is 1100 feet/sec, one fifteenth the speed and one half of one percent of the kinetic energy you need to escape Martian gravity. |
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[ldischler] excellent, I was just going to ask someone to figure out how big a catapult/trebuchet arrangement we'd need to put something into orbit. |
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There are twelve steps to recover from being a hydrolic. As for the idea: |
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ldischler's calculation seems a few orders of magnitude out. If you want to get home that is. If you want to get home in one piece, that is another story. |
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// ldischler's calculation seems a few orders of magnitude out.//
Are they? Take the equation v=(2ax)^1/2. Plug in 20 G's for "a" (20*32.2 f/s^2), and 1000 f for x (the radius of the catapult). Then v=1135 f/s. Martian escape velocity is roughly 16,500 f/s, which is about 14.5 times the catapult velocity. |
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//Are they? Take the equation v=(2ax)^1/2. Plug in 20 G's for "a" (20*32.2 f/s^2), and 1000 f for x (the radius of the catapult). Then v=1135 f/s. Martian escape velocity is roughly 16,500 f/s, which is about 14.5 times the catapult velocity.//
<jaw drops in awe and reverence for a superior intelligence> Wow! Now I remember why I keep coming back to the HB</jdiaarfasi> |
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//In afterthought it probably would be some sort of cannon or something// |
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This is a good afterthought. |
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This idea is similar to the one proposed in "The Moon Is A Harsh Mistress" by Robbert A. Heinlein. In the novel a moon colony had a catapult to send grain raised in tunnels on the moon back to earth. The catapult (iirc) was a electromagneticly opporated linear accelerator. It worked by using magnetic fields to pull the steel containers towards the field before turning off the magnet. Each shipping container had a couple small rockets for fine tuning of the trajectory. |
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The loonies wanted earth to build a catapult for shipping the other direction. It would be located on the equator facing in the spin direction (giving all objects a 1000mph boost). |
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As far as a return voyage goes the earth catapult would have to send solar cell packages to mars in advance then the mission could hook them up along with the new equipment to build a return catapult. |
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This idea has been looked at seriously- except that to save costs on accelerators it would be built in a loop and simply loop the projectile around until escape velocity is reached. |
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// The catapult (iirc) was a electromagneticly opporated linear accelerator. It worked by using magnetic fields to pull the steel containers towards the field before turning off the magnet // |
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Kind of like a big railgun? |
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// This idea has been looked at seriously- except that to save costs on accelerators it would be built in a loop and simply loop the projectile around until escape velocity is reached. // |
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Kind of like that underground donut built for studying what happens when you smash atomic particles into each other? It's somewhere in europe... The major difference here is that the object being accellerated is not meant to crash, but to escape. I suppose you might call it an electromagnetic sling... |
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//It's somewhere in europe//
(linky)
//Are they? Take the equation v=(2ax)^1/2. Plug in 20 G's for "a" (20*32.2 f/s^2), and 1000 f for x (the radius of the catapult). Then v=1135 f/s. Martian escape velocity is roughly 16,500 f/s, which is about 14.5 times the catapult velocity.//
I feel that some clarification is required at this point, if only to prevent my brain from dribbling out of my ears. When we talk about a 'catapult' are we referring to a large see-saw type arrangement with the passengers sitting in a large cup on the end of a lever, nervously awaiting the release of a counter-weight or are we talking about a gigantic elastic band stretched back from an inverted A-frame with terrified passengers sitting in a cup and praying desperately that someone will come up with a better idea before the tension is released? |
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