a reply to: MaxNocerino7
As if right now, 1 (ion drives) seem the most plausible as they are currently in use, and are generally very efficient.
I am very skeptical of the usage of anything sail related, not because they don't work, but more so due to our lack of understanding of solar winds
outside of our own solar system. For instance ones that rely on photons for propulsion would greatly lack the means of propulsion further away from
the sun, and would eventually run out of power as it exits our solar system.
EM drives and others that rely on related ideas seem plausible, but the way they function relies on the presence of magnetic fields (to my
understanding at least) and acting upon those magnetic fields to push against for propulsion. This too would suffer once outside of a solar
The nuclear lighbulb also looks plausible, however it will suffer greatly from a need to dispose of excess heat, and this would greatly reduce it's
capacity outside of atmospheres, unless it was traveling at great speeds allowing it come into contact with more matter that it could interface with
and thus remove waste heat in that fashion in deep space.
For the initial phases, mostly stellar exploration, all of these are plausible (other than halo-drive and horizon drive) however I see something
requiring the expenditure of mass being needed outside of stellar exploration, which invokes the "rocket equation" for all of them.
As for the Halo-drive and horizon drive, they are plausible, however they need another method of propulsion to get them into an instance where they
can actually use their method of acceleration.
Due to this, I lean more so towards an ion drive that gets it's energy from nuclear fission. A runner up is Zubrin's nuclear salt rocket, as it uses
the same method as an ion drive, just with a different means of acceleration of mass. The downfall of Zubrin's idea is that it would rely on an
outside thrust force to get out of the atmosphere due to the radioactive nature of the mass being thrown, though to a far lesser degree than other
NTRs. To be fair Ion engines have the same problem, but for a different reason, they currently lack the thrust to propel themselves through an