Half a croissant, on a plate, with a sign in front of it saying '50c'
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Pocket Lander

Not an eight ball --- an eight ball pocket lander
  [vote for,

Jim agrees --- its difficult to preserve kinetic energy when velocities get large.

Having recently seen a little rocket plant itself neatly on a dime --- Jim has decided to propose yet another improvement upon dissipating kinetic energy into the atmosphere.

Jim takes two PVC tubes, plugs one end of each and connects them via a sturdy rubber pipe. He buries the two PVC tubes vertically in the backward with the open end of each slightly above ground. Now Jim places a PVC plug in both open ends so that a tight seal is made between the plug and the tube.

Jim labels the pocket landers A and B.

Having previously purchase two little rockets Jim places one rocket on A and lands the other rocket on B.

Jim has conserved kinetic energy.

madness, Feb 12 2018

autohorn-blowing Orbital_20Hovercraft
tangential landing proposed in massive footnote [FlyingToaster, Feb 14 2018]

teeter-totter with a moveable fulcrum https://a.1stdibscd...67_1312250361_5.jpg
[FlyingToaster, Feb 14 2018]


       Sturton wonders if Jim is trying to rake together the ingredients for a fish stock.
MaxwellBuchanan, Feb 12 2018

       Jim has yet to make the acquaintance of the well-documented physical phenomena known as the "Coefficient of Friction" and "Coefficient of Restitution"   

       In the situation described, neither energy nor momentum will be conserved. Frictionless pistons are not widely known to exist. Perfectly incompressible fluids with zero viscosity do exist, but working at temperatures below 20 K is challenging due to material embrittlement; PVC is unsuitable.   

       [-] Bad Physics
8th of 7, Feb 12 2018

       [8th] in your comment there you sound almost as if you're criticising this idea from a standpoint of understanding it!
hippo, Feb 12 2018

       Jim might be better off with a teeter-totter apparatus. Not as a replacement for his rocket pipe thingy, but simply as something to entertain himself with.
RayfordSteele, Feb 12 2018

       Better, a climbing frame, and a length of rope tied into a noose.   

       We would certainly find Jim's antics entertaining in such circumstances. Does anyone else want to take a turn pulling on Jim's legs ?
8th of 7, Feb 12 2018

       8th, Seeing as how the active population of the bakery is down to about 10 people or so, I’d like to keep from driving more out the door.
RayfordSteele, Feb 12 2018

       Jim disregards this input as the enfeebled mumbling nonsense of the no longer potentates...   

       Given the evident intellectual stature --- the backyard is large. Not large enough to accommodate intergalactic rocket ships as suggested --- but large. In any case, there are no super conductors or absolute zeros (and no infinities either). PVC and sturdy rubber are quite suitable for all the input loads.   

       It is likely that a different and liberal application of PVC and sturdy rubber is required to improve the tenure of the commentary?!
madness, Feb 12 2018

       Perhaps a different language would suit. My Klingon is rusty. T'Poyr Keh'plekh-nghaahr?
RayfordSteele, Feb 12 2018


       // Jim disregards this input as the enfeebled mumbling nonsense of the no longer potentates.. //   

       Jim, Hab SoSlI’ Quch !   

       // I’d like to keep from driving more out the door. //   

       But we do not seek to drive him out of the door; we want him to stay, twisting in the breeze on the end of a rope, while the crows peck out the last shreds of his eyeballs, and his bones bleach in the sun (if any).
8th of 7, Feb 12 2018

       Ignoring the balls and the landers, I *think* this is an idea for having two rockets push against each other. I suppose you would build up pressure in the tube between the rockets in somewhat the same way as you build up pressure in the breech of a cannon, but slowly and leakily, and then you have to share the resulting pressure between two projectiles.   

       Am I doing it an injustice?
pertinax, Feb 12 2018

       I don't think Jim is talking about the theoretical limit of recovering *all* of the energy of the landing rocket; merely that some portion would be re-used. (The enviro-politician's "conservation of energy", not the physicist's.)   

       When the landing rocket is crushed on impact with B, a fully conserved energy transfer with a zero viscosity incompressible fluid would probably crush the ready rocket at A against its own inertia (assuming it's loaded with a fair mass of propellant, as rockets often are - unlike the "little rocket" types which don't do precision landings)
lurch, Feb 13 2018

       That's better,   

       // merely that some portion would be re-used...   

       All energy is conserved of course --- but yes having rockets land back where they started does not conserve energy in any any useful way.   

       // A fully conserved energy transfer with a zero viscosity in-compressible fluid would probably crush the ready rocket at A against its own inertia   

       Yes... a difficult problem scaled up to adult / interplanetary proportions. To be honest there is not much to add
madness, Feb 14 2018

       Just have one rocket, but make it out of bounciness.
MaxwellBuchanan, Feb 14 2018

       I think they call that a slingshot.
RayfordSteele, Feb 14 2018

       Well - since there so much wasted effort in this...   

       - Salt the landing pad A with 2-centimeter-wide piezoelectric generators “stacked like quarters,”   

       - Better yet ionize the atmosphere within each PVC tube and wrap the apparatus in coils of conductive wire.   

       - Hmm ionize the rocket exhaust and stick it though coils of conductive wire.   

       - Land each rocket on a bouncy castle and have a small child double jump it when required
madness, Feb 14 2018

       Perhaps Jim might develop a way of intermingling the rocket exhaust with, just as a suggestion, cats ?   

       It's a cheap and simple way of converting fishbones into buns ...
8th of 7, Feb 14 2018

       The optimal solution is to have a constant, equal jerk on both rockets.   

       So - ignoring stuff like friction, media momentum, etc -   

       This could be accomplished by launch/land on top free-floating pistons which magically change diameter to accomodate the slope of the funnel-shaped (downwards opening) "cylinders" in which they ride.


       Of course, the solution which doesn't require magic is tangential landing/launch to/from an equator-based linear accelerator <link>.
FlyingToaster, Feb 14 2018

       Too simple, too practical.   

       // equal jerk on both rockets //   

       [madness] on one, Jim on the other ?
8th of 7, Feb 14 2018

       //teeter-totter// with a non-stationary fulcrum.
FlyingToaster, Feb 14 2018

       For simplicity, just put the pivot at one end.
8th of 7, Feb 14 2018

       //pivot at one end// Like an atlatl?
lurch, Feb 14 2018

       //Like an atlatl?// No thanks, but a G&T wouldn't go amiss.
MaxwellBuchanan, Feb 14 2018

       No, like <link>
FlyingToaster, Feb 14 2018


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