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I was wondering if it would be possible to take an O type star and lift material from it reducing its mass in cycles near the time the star reaches the end of its main-sequence age for each reducing mass, while harvesting energy from it throughout?

The idea is to make the most of the vast amount of energy produced by the largest stars by building Dyson swarms around them, then lifting material near the end of their main-sequence age to make them stable again but each time only reducing the mass to necessary stable levels, as little as possible to ensure the most solar energy can be harvested in the shortest time, as time goes by lifting cycles will be further apart as the stars mass reduces but hopefully it will give the greatest energy return for each star.

Another option, with the most energy to be harvested as fast as possible being the goal, would be to stabilize an O type star near the end of its main-sequence then add material back to it in cycles keeping it as an O type star mass for the foreseeable future but I am not sure if that will work as planned and it may be a waste of resources?

Could either idea be achieved successfully by an advanced civilization or would timing of lifting for the first idea be un reliable if trying to leave it as late as possible and would small decreases be possible to keep stabilize it? And is the second idea possible and likely a better idea?

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then lifting material near the end of their main-sequence age to make them stable again but each time only reducing the mass to necessary stable levels

Stars leave the main sequence once they've burned up a significant proportion of their hydrogen. A big O-class star might do this in a few million to a few tens of millions of years. At this point you can't meaningfully "stabilise" them... that fuel is gone and one way or another they're turning into a different kind of star.

All main-sequence stars will eventually move off the main sequence when that fuel is gone. Starlifting prolongs the process, in exchange for reducing the luminosity of the star and hence the amount of power you can extract via whatever mechanism. Its a tradeoff between time and power... you get to pick which you want more of, but you can't have them both... there's a finite amount of fusibles available, and a finite amount of energy you can extract from them.

stabilize an O type star near the end of its main-sequence then add material back to it in cycles keeping it as an O type star mass for the foreseeable future

Won't work, because either a) you run out of hydrogen and it leaves the main sequence or b) you reduce its stellar class and maintain its output for longer.

The only other alternative would be to dump fresh fuel into the star to prolong the hydrogen-fusing phase. This would require a ready supply of large, young stars... easier said than done. The Orion's Arm setting proposed superintelligences constructing "grazer" wormholes to dismantle stars and transport their mass over interstellar distances to somewhere it could be more useful. This isn't obviously less plausible than your hypertechnological setting.

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  • $\begingroup$ Yeah I had forgot about the core fusing into heavier elements even if new hydrogen is plenty full, does that mean you cant keep prolonging large stars as fusion at the core will continue so the only option is taking it down to a more stable F or G type? $\endgroup$ Commented Jan 4, 2022 at 17:38
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    $\begingroup$ @AlanDavies given the masses involved, you'd be breaking it apart into many F or G types. O-type stars are very large, after all. It is remotely possible that on a big and hot enough star with lots of convection you could combine starlifting and refueling using other stars you've dismantled for the purpose, removing heavier elements as you go. I'm not sure it has many benefits over the "build your own benign cluster" approach, though. $\endgroup$ Commented Jan 4, 2022 at 17:57

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