Quick release, yes. Everything else you said, even whether it's a bracket or some other solution, not so much. Applying math to your contrived scenario you already know doesn't work (a single bracket of 6.5 sq in) is just a waste of effort. Especially since you already mentioned brackets (plural!) in the sentence before that. Of course they'll make the collective surface area large enough for the mechanism to actually work! If they use that mechanism at all.
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Normally, I rather raise just the problem points and let the others get to the conclusion by themselves. But that isn't working here...
Let me remind you, there is no known working example of anyone spinning it to that speed, so there is no known definitive list of problems, and no known solutions to the problems.
You made an error in saying I know the bracket (with 6.5 square inch contact area) wont work. Actually, I don't know that a single bracket wont work. It may work.
What I said was such bracket will exceed the pressure needed to make diamonds. Saying that is
very different than saying it it wont work.
I am not a material science expert. A bracket that can hold 880,000lb may already exist and may even be available off-the-shelf. What I do know is that the bracket must hold the force and must fully extract very very fast.
What is known are the numbers from mathematics. There is no research they can do that will reduce the total centrifugal g-force. And they want it to go fast (2.3km/second) that is the other challenge. If the top-bracket releases 1 microsecond late, the bottom already moved 2.3mm deforming the rocket. So a single bracket may well be the best solution.
But then how will the rocket hold it's shape? That darn thing must hold 880000lb (there about, since not everything will be located at a single mathematical point). With the magnitude of the numbers, it will be problem every direction you look. All are likely solvable, but very few of them will be easy.
So, now that I elaborated some more, was I my attempt of illustrating to you that "likely a lot of problems, likely solvable, but likely not cheap" a success?
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I don't know what the quick release solution is. If I had to guess, some sort of multiple carbon sling setup so the load itself doesn't need be reinforced to support brackets from the high side. Probably some sort of pin system for release. Or explosive bolts if pins won't work.
As for cost, that's not true at all during the R&D phase. Long term yes, unless the competition has more business than it can handle.
Be it "multiple carbon sling setup" or any other setup, you can't beat physics. You want the acceleration for the payload, you will pay for the force of acceleration. Either linear, or centrifugal, or mix. The sling is merely spinning incomplete circles, so you are still dealing with the same centrifugal force. Like a spinning the wheel, once it get to that speed, that will be your centrifugal force. There is perhaps another universe with different laws of physics (and values physical constants) that is more favorable, but in this universe, we are stuck with these contrived math numbers.
For spinning, 11,000g (rounded) and 440lb (200kg) payload = 880,000lbs centrifugal.
2.3km launch speed = 2.3mm/microsecond. The payload will have to deal with the increasing bending and uneven load distribution for every micro second the release is out of sync.
No amount of discussion can change those numbers as long as our universe's physics doesn't change.
Indeed the test and research on how to harden a particular payload object needs to be done only once. Trouble is, the tested solution needs to applied to
every copy of the object that you will launch. The tested solution is likely expensive to apply. Worst yet, any minor change to the payload object, you need to test that object over again.
Since I have been unsuccessful letting you infer deeper from what I say, so let me say this out loud: I said "likely very expensive" from reasoning and experience. Similar to while I don't know how much 100lb of gold is worth today, but from experience, I know a 100lb of gold likely isn't going to be cheap today, tomorrow, or for the rest of the month...