08-13-2022, 07:49 AM
As folk who follow space news are likely aware, a company named Spinlaunch exists.
They purport to be building a catapult to launch things toward orbit from the ground, by a mechanism that involves attaching the payload to the end of a spinning arm and releasing it at the appropriate moment (so to speak) to get more than halfway to orbit.
The claimed benefits include "gradually" spinning the catapult arm up to launch speed over the course of hours, which supposedly spares the cargo a huge destructive shock and avoids placing an instantaneous demand on the electricity grid for a zillion watts of power which the grid can't provide.
I foresee numerous problems with this plan. Some of them are:
*dynamics of unbalanced spinning loads. If the spin arm is balanced before release then it is unbalanced after release and vice versa.
*gyroscopic forces because Earth rotates while that enormous spin is building up (I guess you could spin in the same plane as the equator to get around this.)
*payload undergoes crushing G-forces due to centripetal acceleration, for hours.
*G-forces endured for hours are in fact sufficient to launch the payload to the same velocity in a linear accelerator the same length as the spinners' diameter.
*The linear accelerator's "shock" would be over in a relative instant.
*They've proposed six hours to spin up, a launch, six hours to spin down, six hours to spin up, another launch, etc. No more than two launches per day.
*But I'm guessing they'd spin down much faster because when they release the payload they release the vacuum in their catapult chamber.
*When air enters the catapult chamber it would cause shockwave damage, friction heating, energy loss and probably spin down in a lot less than six hours.
So rather than bag on them, why not try to fix it? Here is my vision of a more practical Electric Yeeter.
*A linear electric launcher is unconditionally better. We should build that instead. Limit crushing forces to an instant.
*the grid can't provide a zillion watts for an instant, so why don't we use our six-hour draw to spin up a giant flywheel that can?
*At a much lower mechanical stress, the flywheel can store vastly more energy, because it's many times the mass of the payload.
*There is no point at which a flywheel becomes unbalanced.
*A flywheel can be built in the same plane as the equator regardless of what direction you want to launch something in.
*A flywheel need not be spun down after each use. If it takes six hours to store enough energy for a launch, you can launch every six hours.
*There is no reason why launching should release the vacuum or cause shockwave damage etc in the flywheel chamber.
*Depending on the capacity of a flywheel it could hold sufficient energy for several launches. Launching 28 times a week is more flexible than 4 times a day.
*A flywheel can be spun up long before the payload even arrives - for example at night while electricity is cheap.
*When not in use as a launcher you could buy cheap electricity at night and sell expensive electricity during the daytime.
They purport to be building a catapult to launch things toward orbit from the ground, by a mechanism that involves attaching the payload to the end of a spinning arm and releasing it at the appropriate moment (so to speak) to get more than halfway to orbit.
The claimed benefits include "gradually" spinning the catapult arm up to launch speed over the course of hours, which supposedly spares the cargo a huge destructive shock and avoids placing an instantaneous demand on the electricity grid for a zillion watts of power which the grid can't provide.
I foresee numerous problems with this plan. Some of them are:
*dynamics of unbalanced spinning loads. If the spin arm is balanced before release then it is unbalanced after release and vice versa.
*gyroscopic forces because Earth rotates while that enormous spin is building up (I guess you could spin in the same plane as the equator to get around this.)
*payload undergoes crushing G-forces due to centripetal acceleration, for hours.
*G-forces endured for hours are in fact sufficient to launch the payload to the same velocity in a linear accelerator the same length as the spinners' diameter.
*The linear accelerator's "shock" would be over in a relative instant.
*They've proposed six hours to spin up, a launch, six hours to spin down, six hours to spin up, another launch, etc. No more than two launches per day.
*But I'm guessing they'd spin down much faster because when they release the payload they release the vacuum in their catapult chamber.
*When air enters the catapult chamber it would cause shockwave damage, friction heating, energy loss and probably spin down in a lot less than six hours.
So rather than bag on them, why not try to fix it? Here is my vision of a more practical Electric Yeeter.
*A linear electric launcher is unconditionally better. We should build that instead. Limit crushing forces to an instant.
*the grid can't provide a zillion watts for an instant, so why don't we use our six-hour draw to spin up a giant flywheel that can?
*At a much lower mechanical stress, the flywheel can store vastly more energy, because it's many times the mass of the payload.
*There is no point at which a flywheel becomes unbalanced.
*A flywheel can be built in the same plane as the equator regardless of what direction you want to launch something in.
*A flywheel need not be spun down after each use. If it takes six hours to store enough energy for a launch, you can launch every six hours.
*There is no reason why launching should release the vacuum or cause shockwave damage etc in the flywheel chamber.
*Depending on the capacity of a flywheel it could hold sufficient energy for several launches. Launching 28 times a week is more flexible than 4 times a day.
*A flywheel can be spun up long before the payload even arrives - for example at night while electricity is cheap.
*When not in use as a launcher you could buy cheap electricity at night and sell expensive electricity during the daytime.