Reply #39: The smallest possible FTL ship would be 1.25 km in diameter

[TechBear_Seattle]

Basically, it would be a central sphere about 250 meters in diameter to hold the fusion reactor and a store of helium fuel. The reactor powers an energy "bubble" of altered dimensions a few Plank lengths thick above the surface scaffolding of the ship; this bubble defines the boundary of the universe inside the ship and the universe as a whole. When the ship is under way, normal spacetime kind of flows around the ship and reconnects without a ripple behind it.

It does happen that, occasionally, a piece of matter will go through the bubble, causing it to reconfigure briefly to match the altered dimension, then snap back to normal as it passes back into the normally formatted universe inside. Weird things happen when this occurs: it is not good for quarks to change from red, green and blue to vermillion, chartreuse and aqua. The resulting Yakazumi-Zellerhoff (or "why-zed") radiation is short lived but hazardous to a wide variety of materials. Because of this, safety protocols require a minimum of 200 meters of dead space between the inner surface of the bubble and anything other than internal scaffolding, and at least 500 meters between the inner surface and any organic materials, inhabited modules or essential systems such as the fusion reactor.

So basically, I want FTL travel to be expensive and somewhat dangerous, under the control of a mega corporation; think of the Spacer Guild from the Dune books. And I want the few inhabited systems (human habitable worlds are pretty rare) to be effectively on their own, isolated from all other human culture except for the regularly scheduled FTL vessels which park outside the star's heliopause to transmit and receive data and take on and dispatch cargo pods that will take another three to four weeks to transit the system.

And I want it this way because. :hi: