Stellar Radiation Detons- Cosmic Weapon

Question

In this setting, Humans have done multiple advances in technology and are nearly on the verge of being a Type III civilisation, They have nearly colonized the Milky Way and have tapped energy from nearly all the energy sources available. They are now in war with a rival alien civilisation. The two sides are on a stalemate. Until a human engineer comes up with a plan.

The idea is to take a massive star, around 10-20 solar masses, and make a reflective shell that completely surrounds it. The shell does not have to be completely thick, it is just as wide as aluminium foil. Thus, as the star emits light, this light is again reflected back by the shell onto the star, which heats it up a bit. The star then glows more brighter due to the heat, as it fuses hydrogen more quickly, and emits more light, which is reflected back and heats it up again. This results in a runaway-reaction that causes the star to explode, either from it ridiculously getting crushed by its own radiation pressure and rebounding back, or by the intense heat produced. The radiation and heat released would incinerate nearly anything within the vicinity.

This weapon is used to maximise heat/radiation damage to the enemy, and wipe out their army.

Diagram-

What are the drawbacks of this design, and if any, what should I do to fix it?

Answer 1

It's not a very good weapon

The shell would melt if you trapped all the heat, and you need to move the star to the enemy to make it explode, which is very visible and gives them several years to move their stars or disrupt your manufacturing process.

This just gets worse as you trap more heat, as the shell will heat up even more. Dyson sphering a star is a massive undertaking that you don't do with a thin shell.

In addition, if you heat up the star, it will expand, damaging your shell, and not causing it to explode. Stars supernova when they run out of fuel, not when you make them burn more.

Make a proper dyson sphere.

You'll need a lot more mass, and thrusters, but you can make a proper thick dyson sphere with heat radiators to remove heat. Then use the massive star as a weapon to smash their systems, flying it at stars that are important to the enemy and using the star's vast energy reserves to fire massive lasers to wipe out star systems. Directional fire is better than an explosion anyway, since you waste less energy.

Answer 2

The Shield Melts

The Sun's surface is 6000K. Hot enough to melt iron, stone, tungsten, osmium, or any popular real material. The corona is millions of degrees hot but this is something or a red herring.

If you try and trap the star's energy inside a box then the box melts like an ice cream sandwich.

Answer 3

For a star to explode, you want to compact it, not to expand it.

That's what happens in a supernova, when the nuclear reactions happening in the star core are no longer sufficient to balance gravity, and the collapse it causes generate a flash of fusion, making the star go boom!

Very massive stars can undergo core collapse when nuclear fusion becomes unable to sustain the core against its own gravity; passing this threshold is the cause of all types of supernova except type Ia. The collapse may cause violent expulsion of the outer layers of the star resulting in a supernova. However, if the release of gravitational potential energy is insufficient, the star may instead collapse into a black hole or neutron star with little radiated energy.

Core collapse can be caused by several different mechanisms: exceeding the Chandrasekhar limit; electron capture; pair-instability; or photodisintegration.

Answer 4

The enemy gets a vote, too

This is a useful principle you should never forget in your war planning. By definition, it doesn't take place in a vacuum, but with an active opponent - and quite a good one if they've fought you to a standstill.

This plan is very susceptible to enemy interference. It's obvious (it hardly takes much effort to notice a star being blocked), it needs to be carried out relatively close to the enemy (your engineered nova has a limited effective radius as a weapon, because it's wasting most of its energy blasting empty space), and the construction vehicles, supply shipments, and the thin skin of the star-shell itself are all weak points that an enemy can exploit. Given such a tempting target, you can hardly expect an enemy to just sit there and wait for the star to explode!

Or can you? Perhaps, if your war is dug in along extremely static lines, like a WWI trench system in space (which will no doubt require much further handwaving), then your star-bombs can serve as a way of provoking your enemy into a desperate attack on your fixed defenses before the bomb goes off, or as a way of pushing them off their own defensive line to avoid the explosion. But in a war of maneuver, it's a pretty hopeless weapon.