I was in the shower the other day thinking about the sun going Nova, you know...like you do, and a thought occurred to me:

Could you turn the sun into a stable, mostly closed system?

Some details of the universe in question:

• The actor in this case is a type II civilization
• They have colonized 5 planets in their 12 planet system
• They have access to unobtanium for the purpose of building any machinery that needs to interact with their star or be used in the process.
• The unobtanium is not adversely impacted by the heat of the star or the cold of interplanetary space. For the sake of this question it is also perfectly sealed meaning there is no loss of whatever in your calculations.

The goal:

• Create a system that allows you to prevent a star (identical to our sun) from going nova, or burning out or at least drastically elongates the lifespan of the star (at least 20% more starry life)
• Requires the least possible amount of external stellar fusion resources from being space-trucked in to feed the system.

Answers must:

• Identify which solar products must be removed from the star
• How would you extract it? (keep the unobtanium in mind)
• In what quantities?
• How much energy would it require? How does this energy compare to overall solar energy captured?
• Identify which elements/compounds must be added to the star
• In what quantities?
• How much energy it would take to move them from Mars orbit to the sun
• For the sake of this question ignore resource availability
• Identify what can be recycled from the extracted stellar waste
• Ideally most if not all of the required elements could be synthesized from solar waste.
• The remaining waste can be dumped on a Mercury like planet nearby, the less the better.
• Propose machinery/system to execute the process

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