Avoiding carrying fuel with you is certainly tempting, solar sail and various beam-powered types of propulsion are some of the better known ones. Various types of the solar wind sail would give much more thrust if one could figure out how to efficiently stop or deflect the solar wind particles (mostly protons), and various versions of a ramjet when in interstellar space. https://en.wikipedia.org/wiki/Magnetic_sail#Interstellar_travel is a decent summary. My bet is on that kind of technology, unless someone revolutionizes space travel by figuring out how to bend spacetime more efficiently than with sheer mass, and makes something like the Alcubierre drive feasible.
>unless someone revolutionizes space travel by figuring out how to bend spacetime more efficiently than with sheer mass, and makes something like the Alcubierre drive feasible.
The bigger problem here is just that genuine negative inertial mass (which you need for warp drives) is considered to be probably impossible for good reason, since it lets you both violate causality and create perpetual motion machines.
Avoiding carrying fuel with you is certainly tempting, solar sail and various beam-powered types of propulsion are some of the better known ones. Various types of the solar wind sail would give much more thrust if one could figure out how to efficiently stop or deflect the solar wind particles (mostly protons), and various versions of a ramjet when in interstellar space. https://en.wikipedia.org/wiki/Magnetic_sail#Interstellar_travel is a decent summary. My bet is on that kind of technology, unless someone revolutionizes space travel by figuring out how to bend spacetime more efficiently than with sheer mass, and makes something like the Alcubierre drive feasible.
>unless someone revolutionizes space travel by figuring out how to bend spacetime more efficiently than with sheer mass, and makes something like the Alcubierre drive feasible.
The bigger problem here is just that genuine negative inertial mass (which you need for warp drives) is considered to be probably impossible for good reason, since it lets you both violate causality and create perpetual motion machines.