In Mars heyday before the building of the space elevator ground to orbit craft regularly shuttled personnel and goods up and down the Martian gravity well. With advanced materials, the high thrust provided by fission drives and safe to handle water reaction mass they were also sturdily built, safe and reliable.
A few of the TAVs are still around providing regular and reliable service. They are mostly in the hands of private organisations, some with triad connections. They are actually financially competitive with the beanstalk but cannot handle the high volumes required of modern Mars. However there is less tolerance of their mildly radioactive exhaust today and their numbers are dwindling. Many have been converted to OTVs.
The craft carries enough water reaction mass for a one way journey. It must refuel in low orbit for the return journey to Mars. Several privately owned comets have been moved into low orbit to provide a combined "gas station" and orbital transfer point, where people and goods are moved to OTVs or interplanetary craft.
Design: 23ft Sphere (12.167 spaces, Metal Matrix, Extra Heavy (default) frame); cDr/cPF 0.2/1FSB (Metal Matrix armor).
Modules: Old Cockpit, Very Small PESA, Very Small Radar, 1 compact Fission Drive (water), 7.5 Ultra-light tank (water), 0.5 seat modules (8 seats), 2.5 cargo hold (12.5 tons), small entry module.
Statistics: LMass 143.88, CMass 87.63, Dry Mass 31.38, EMass 18.08, Payload mass 13.3, Fuel Mass 112.5, Cost M$ 3.12, cHP 99, Size Modifier [hull] 4/4, Maintenance interval 11.32 hours (8.5 hours per day)
Performance: Realistic sAccel 1.60 G (Book 1.39 G), Loaded sAccel 0.84 G, Dry sAccel 3.87 G, Empty sAccel 6.72 G, Burn Endurance 520 seconds, Burn Points 444, Realistic DeltaV (without turnover) 3.14 mps (Book 2.72 mps)
Payload: Crew 1, Seated passengers 8, Cargo 12.5 tons
Trip Data: To Mars low orbit (2.2 mps, 0.38G) 300 seconds, Fuel M$ 0.00225
Example economics: 1000 trips per year (500 round trips), One way seat price $80, one way Cargo price per ton $250. As trade is dropping off the cost of running these craft is increasing and prices are rising.
Transhuman Space Index