Emperor class Battleship

For those that don't know much about Gunbuster here is some information on the Sizzler

The Sizzler is the mass production variant of the Gunbuster) developed in the 2050s to help deal with the Space Monster threat and later to escort Buster Machine #3 to the galactic core.

It is used in the same role as what most civilizations would use fighter craft for. Namely intercepting small fast moving threats that might be a problem for the Capitol ship's slower tracking weapons to deal with.

Although it is a bit stronger than most space fighters in fiction.

Weapons/Power

• Reactor output 10²⁶ watts or ~24 petatons per second.

  • That power output is presumably divided between it's beam weapons and it's thrusters.

The Sizzler is armed with three weapons that are relevant to this battle.

• The Sizzler beam which is some kind of energy beam weapon.

  • Similar to the ship based weapons we can probably expect light second ranges out of the beam weapon.
  • Similar to Gunbuster's beam it likely has some degree of AOE (Note: That formation of space monsters is 80 AU in diameter)

• It has melee weapons which hit at 800 kilotons of TNT.

• It has 40 megaton missiles.

Speed

• Max speed: ~90%c

• Normal speed: 60%c

• Acceleration is unknown. But they would need to be able to keep up with Space Monsters that can change their velocity from 10%c to -10%c within a few seconds.

• We could also scale the Sizzler's acceleration off an individual half of Gunbuster (the full mecha is made from two ships) going from huge relativistic time dilation relative to Earth to matching it within a few seconds.

NOTE Gunbuster follows Relativity fairly faithfully when in normal space. So going to 90%c will cause a time dilation factor of 2.29 which effectively doubles their reaction time.

Though to be fair pilots in Gunbuster have reacted to relativistic objects moving around them so that might not be that much of a problem.

Durability

• It's usual opponents can do stuff like this (Diebuster spoilers) it can likely survive that kind of firepower.

  • Without getting into too much detail Sizzlers are a mass production variant of the Gunbuster and they are supposed to be pretty comparable with one another. The Gunbuster can easily tank attacks from a larger variant of the cruiser sized SM above.

Alright now that, that is out of the way

Opponents start 10 light seconds apart with Jupiter in between them. Both sides have a vague understanding what the capabilities of the other side are. For example the Captain of the Battleship knows the Sizzler has a beam weapon, a melee weapon, and missiles but not precise details on them. The Sizzler pilot knows the Emperor class has numerous mass drivers and lasers with possibly some more exotic ordinance.

Any Psykers on the Battleship are not able to directly affect the Sizzler unless this is a stomp.

Bonus round:

What is the strongest WH40k ship that a Sizzler can beat?