The Athena was an interplanetary spacecraft designed to carry human explorers to and from Mars during the Ares program in the early 21st century. Over 150 meters long and weighing in at around one hundred tons (sans boosters or deuterium propellant), the Athena was the first of many massive in-space construction projects undertaken in low Earth orbit. Built over the course of four years, Athena saw her maiden voyage with the launch of the Ares I expedition in early 2016, and remained in service for another two decades before being decommissioned at the end of Ares V. The Athena, though dismantled for part reclamation after the close of the Ares program, served as the design template for humanity's interplanetary vessels for several centuries afterward.

Athena's staging functioned uniquely relative to previous mission vessels. It used a set of four colossal "Earth-escape" chemical rocket boosters to leave LEO and escape the gravity well of the Earth-Moon subsystem, jettisoning the empty tanks around the L2 point to be recovered and refueled by Deep Space Gateway personnel. Once out from under the Earth's gravitational thumb, Athena engaged its main drive system: a incredibly efficient positron-catalyzed fusion drive developed in the early 2000s. This allowed the vessel to radically decrease the travel time between Earth and Mars to only 220 days. After the full Mars surface mission was complete, the Athena used its twin "Mars-escape" boosters -much smaller than the EEBs- to exit the gravity well of Mars, discarding the spent boosters into interplanetary space as it reignited the fusion drive that would carry it home to Earth.

[ ATHENA STATS ]
(Model scale: 1 full brick height = 3.9 m)
Length: 152.1 m
Total launch mass: 11200000 kg
Vessel wet mass: 210000 kg
Vessel dry mass: 100000 kg
Earth-escape booster (x4): 50.7 m * 13.65 m / 2750000 kg
Earth-escape stage mass: 11000000 kg
Mars-escape booster (x2): 23.4 m * 10.9 m / 450000 kg
Mars-escape stage mass: 90000 kg
Interplanetary drive: Sagitta-1 radioisotope-positron catalyst fusion engine
Drive max acceleration: 0.0005 m/s^2 (0.00005 G)
Drive delta-V: 75000 m/s
Drive specific impulse: 150000000 s
Crew: 4
LEO shuttle: Orion II crew module
Lander: Phoenix multi-stage MTAV (Mars trans-atmospheric vehicle)

Read more about the Ares program and the future-history of Mars on the Diaspora site: https://www.worldanvil.com/w/diaspora-spyglassrealms/a/mars-article