Tsar Bomba

While pure fission weapons are limited in the power they can achieve before they become infeasibly heavy and fuel inefficient, with the most powerful ever tested being the 500 kiloton Ivy King device detonated on November 16, 1952, by adding additional fusion stages to a thermonuclear device, a near unlimited yield can be achieved.

Indeed, thus far the most powerful nuclear weapon ever detonated was a three-stage Soviet Tsar Bomba, dropped on October 30, 1961.

Originally designed to have a yield of 100 million tons of TNT, to limit the spread of radioactive fallout, this was reduced at the last minute to only 50 megatons.

Nonetheless, the bomb produced a fireball a whopping 8 kilometers across, which was visible nearly 1,000 kilometers away, and nearly overtook the Tu-95 bomber that dropped it.

The total distance to Alpha Centauri is therefore approximately twenty-five trillion miles.

Voyager I, the fastest human made object on an outward trajectory from the Sun travels at roughly seventeen kilometers per second or about thirty-eight thousand miles per hour At this speed, the journey to Alpha Centauri would require approximately seventy-three thousand years Seventy-three thousand years When that journey would've begun anatomically modern humans were painting on cave walls in Europe and sharing the continent with Neanderthals Every civilization that has ever risen and fallen on Earth every empire, every religion every scientific revolution every war every work of art fits comfortably within that travel time with room to spare The entire recorded history of humanity roughly five thousand years represents less than seven percent of a single trip to the nearest star at our current best speed What about faster? The Parker Solar Probe During its closest approaches to the Sun reaches speeds of approximately one hundred and ninety-two kilometers per second making it the fastest human made object ever relative to the Sun If a spacecraft could somehow maintain that extraordinary velocity on an outward interstellar trajectory the trip to Alpha Centauri would still take approximately six thousand six hundred years The ancient Sumerians were inventing cuneiform writing roughly that long ago An entire arc of human civilization would pass before the spacecraft arrived To bring the travel time down to anything remotely approaching a human lifetime requires velocities that are By current engineering standards almost inconceivably fast At ten percent of the speed of light Roughly thirty thousand kilometers per second The crossing to Alpha Centauri would take approximately forty-two years A crew departing in their twenties might arrive in their sixties Demanding but not impossible in principle for a single generation At twenty percent of the speed of light the trip shrinks to roughly twenty-one years Almost manageable if everything else about the mission could be solved But achieving these speeds requires energy inputs that dwarf anything humanity has ever produced for a single purpose The kinetic energy of a moving object scales with the square of its velocity Double the speed and you quadruple the required energy To accelerate a modest one thousand kilogram payload roughly the mass of a small car to ten percent of the speed of light Requires approximately four point times ten to the seventeenth joules of kinetic energy This is equivalent to roughly one hundred and seven megatons of TNT More than twice the yield of the most powerful nuclear weapon ever detonated, the Soviet Tsar Bomba.

And that calculation accounts only for the payload itself.

It ignores the mass of the propulsion system, the fuel, the shielding, the life support systems, and the structural framework required to hold everything together.