How powerful is a photon torpedo from Star Trek?

It's been too long since we had a nerdy (pseudo) science post here so, I found a good topic in that vein and ran with it...

Things like the time it takes for the Enterprise to warp to one star or another are just scientific plot McGuffins in the Star Trek franchise. They are whatever the writers say they are in the script. However, we can sometimes quantify the actual power/abilities of the fantastic tech seen in the shows and movies.

While reading through the tech manual for Star Trek: The Next Generation, I saw in the chapter on the Enterprise-D's weapons systems that each torpedo has 1.5 kilograms of anti-matter inside. The anti-matter here is anti-deuterium, the anti-matter equivalent to deuterium, a real-life isotope of Hydrogen. The ratio of reactant in the torpedo will be the same as any anti-matter reactor in Star Trek's universe: 1:1.

Thanks to a gentleman named Edward Muller and his web page with an anti-matter calculator we can actually determine how much explosive yield that 1.5 kilograms of anti-matter will actually produce. According to the page, 1.5 kilograms will yield an explosive force of 64.44 megatons of TNT. The most powerful nuclear weapon ever exploded on Earth, the Soviet Union's 'Tsar Bomba', had an explosive yield of 50 megatons.

Soviet scientists could have made it have a yield of 100 megatons but, they were afraid of what that would do to the planet. That's not an unrealistic concern. According o the Anti-Matter calculator page, the third 1883 eruption of the Krakatoa volcano released an amount of energy equivalent to 150 megatons. Also according to that page, Hurricane Katrina hit the Gulf Coast with the force of a 300 megaton explosion. Rather impressive and frightening to think about, heh?

So, if you get into a pointless nerd debate about fictional weapons from a science fiction franchise,  you might have some actual facts to work with for once. That is, unless a future film or episode changes things. And the tech manual's authors did say that the book wasn't canon and shouldn't restrict a writer's creativity...

Furthermore, it's currently impossible for me to even guess at the power of a Quantum Torpedo. The DS9 tech manual lists the explosive yield of the regular photon torpedo with a fictional number, 18.5 isotons. It then goes on to say that the theoretical limits of traditional photon torpedo technology, 25 isotons, was reached and that the Quantum torpedo was developed to exceed those limitations. Then, a few episodes of Star Trek: Voyager ret-conned that with onscreen dialogue about various torpedoes. You can read about those changes on this page from Memory Alpha that talks about fictional units of measurement like Isotons.

Simply put, the torpedoes are as powerful as the writer wants them to be... Even if that creates contradictions and conflicts...

- Lord Publius