Adrian Mann is an awesome digital artist who has visualised some of the classics of spaceflight studies of the last 35 years...

This is Rocket Science

...some notable creations are Starship Daedalus

Starship Daedalus

...which is very cool. And another 'blast from the past' is Project Orion

Project Orion

And the ultimate starship design, the interstellar ramjet

Bussard Ramjet

But there's some near-term designs from the 1960s, aka the Nerva nuclear thermal rocket and its associated Mars Mission

Project NERVA

A PROFAC (Propellant Factory) from the early 1970s (studied by ELDO, the European Launcher Development Organisation, parent of the ESA)

PROFAC and Space Tug

...the Space Tug design is from a European study on early Lunar access using European and NASA hardware. In Adrian's visualisation we're seeing the Luna Landing kit deployed, plus an add-on Crew Mission Module. For interorbit operations the Space Tug would have neither and would dock to a cargo module or another Space Tug operating as a booster stage. Fully fuelled a Tug would mass 12.5 tons, with a burn-out mass of about 1.8 tons. According to Marcus Lindroos this is well within state of the art. By comparison NASA-studied Tugs massed 2.5 tons dry and 20.8 tons fully fuelled, with an extra 4.4 ton CMM for a 3-man 50 day mission.