Really Wild Stuff
This won't work, but a better idea ... might!
Extracting Solar Helium
Solar mega-engineering: What if we harvest much of the helium from the Sun ... and cool it down, extending its lifetime?
But if we could ... the sun emits 3.85e26 watts. The sun is 25% helium, and creates 6e11 kg of helium per second. The Sun's mass is 2e30 kg; the helium fraction is 5e29 kg. Escape velocity from the surface of the Sun is 620 km/s. A magic 100% energy-efficient helium elevator could remove 6e11 kg/s from the Sun with 1.1e23 watts.
If 1% of the Sun's energy output (3.85e24 watts) could lift out helium at 100% efficiency, that would be 2e13 kg per second, 33 times the production rate, and would remove all the helium in 2.5e16 seconds or 800 million years. The Sun would cool, instead of the current slow heating, which will render the Earth uninhabitable perhaps 1 billion years from now.
If (by removing helium) we tuned the Sun to a permanent 3.85e26 watts, and burned up all the hydrogen, how long could it continue to produce 3.85e26 watts?
The current energy production rate consumes 6e11 kg of hydrogen per second, and there is 1.5e30 kg of hydrogen remaining now. 1.5e30/6e11 = 2.5e18 seconds, or 80 billion years.
Over gigayears, the mass of the Sun will diminish, and so will its gravitational pull, so the Earth's orbit will widen and the power received by the Earth will diminish. Ue could fix that by launching a LOT of the Earth's material in the direction of its orbit (prograde), to aphelion distances far from the inner solar system. A better idea is a long series of gravity assist flybys, which would also slow the Earth down in its orbit, moving it inwards. Complications, complications, managing a solar system is a lot of work!
What do we do with all the helium we extract? Perhaps we fly that mass past the Earth and subtract momentum that way. Only a very small delta V on that vast amount of helium would slow the Earth's orbit enormously over the gigayears. That helium can be formed into a "dark helium star" in the Oort cloud, far from the Sun. 2e13 kilograms per second would grow to a mass the size of the Earth in 10 thousand years, and the size of Jupiter in 3 million years, and (as previously mentioned) the entire helium mass of the Sun in 800 million years.
All we need is vast amounts of equipment, and some magic method to extract mass from the Sun's enormously deep gravity well.
Optical cooling uses precisely tuned light to create "energy traps" that cool atoms to microkelvins with zero translational velocity. What if a GYNORMOUS amount of optical power was used to create an energy trap for helium atoms in a solar prominence, and shift those atoms into the path of a GIGANTIC magnetic trap passing near the sun on a steep parabolic?
Perhaps we just fuse the atoms into hydrocarbons, feed male cattle, and produce a lot of B.S. This web page is the beginning of that B.S. production process.
A solar flare typically emits 1e20 joules, and can emit up to 1e25 joules, lifting material far above the surface. MoreLater