Fission/Fusion Reactor: A Sodium-Potassium (NaK) Cooled Fission Reactor provides the power to charge capacitor banks and powers magnetic containment for the fusion part of the reactor. When the capacitors are fully charged, the fission reactor then powers the magnetic fields to contain the fusion reaction and the capacitor banks power the lasing elements to ignite the fusion reaction. The fission reactor will maintain power on the magnetic fields until the fusion reactor generates enough power on it's own to take over that function. The fission reactor will then be held on standby to maintain containment if needed and providing auxiliary power needs or additional power for charging the capacitor banks. The Fusion Reactor uses Helium 3 or Hydrogen for it's fuel. Most Fusion reactors can use both, but not at the same time as there are differing fuel feed requirements. However most current built fusion reactors can switch from one fuel to another after a brief shut down and reconfiguration before re-starting with the other fuel. Depending on the size of the reactor the change over can be completed in approximately 3 hours, however starting a fusion reactor still takes between 4 to 12 hours depending on it's size.
That is part of the technology I am making for my story. Now for the help.
I am thinking that the fission reactor would be something about the size of a mid 70's model Volkswagen Super Beetle for the smallest ones which an in system craft (Cargo/Personnel shuttle) would use, up to 8 40 foot connex Containers for the large passenger Starliners and military ships.
The Fusion part of the reactor due to the magnetic containment bottle which is contained in a sapphire alloy/Plasma Matrix is quite large. The smallest fusion reactor would be about the size 24 40 foot connex containers stacked in a square configuration but the actual bottle is round like a ball. That would be the smallest. The larger one would be 4 to 6 times larger depending on what they are installed in. Military vessels necessarily have those large ones, most civilian ones would have 2 or 3 smaller ones instead of one large one.
Now we have the hypothetical size, my head is still having a problem wrapping around all the assorted errata needed to run those reactors. Fuel bunkerage, feedlines, capacitor rings and their feedlines and all the associated hardware necessary for the care and feeding of those reactors. Not to forget the lasing equipment to even start the fusion reactor.
Plus here is the kicker, most ships except large military ships have 2 or more fission-fusion reactors. A small tramp freighter might have only 1 fusion reactor but they will have at least 2 fission reactors. And if it is a jump drive equipped ship it will require at least 2 fission fusion reactors just to power the main drive and the jump drive.
Do you see why I am having an issue? I have my main character meeting his new crewmates and one of them is standing on a medium size fission reactor that runs through 3 decks, but how do I describe the various connections? How large are they? Actually just how small could a fission reactor get?
My brain hurts now.