tics module would form the third side; and an 8.5-metric ton command module and a 3.2-metric-ton airlock module would together make up the fourth.
A pressurized “bridge” tunnel would cross the inside of the square, linking directly the two habitat modules. Another tunnel would pierce the center of the bridge vertically. Its forward end would link with the top of the drum-shaped, 11.9-metric-ton Earth Recovery Vehicle (ERV), while its aft end would carry a docking unit. The ERV, situated deep within the spacecraft’s structure, would double as the crew’s solar flare “storm” shelter. Four spherical tanks holding a total of 91.9 metric tons of cryogenic liquid hydrogen/liquid oxygen propellants and two rocket engines with a combined mass of 4.6 metric tons would be mounted atop the crew modules.
The ERV/storm shelter would be mounted at the center of an 11.4-meter-diameter, one-metric-ton flattened conical aerobrake heat shield. ERV, ERV aerobrake, crew modules, tunnels, propellant tanks, and engines would nestle within a bowl-shaped, 25-meter-diameter, 16.1-metric-ton MOI aerobrake. Except during propulsive maneuvers and aerobraking, four solar arrays capable of generating a total of 35 kilowatts of electricity at the piloted spacecraft’s maximum distance from the Sun (that is, in Mars orbit) would extend beyond the edge of the MOI aerobrake. During maneuvers and aerobraking, the arrays would be folded out of harm’s way atop the crew modules, Fully assembled and loaded with propellants, the piloted spacecraft’s mass would total 193.7 metric tons.
The assembly crew based at the Space Station would link a newly assembled smaller (197.4-metric-ton) OTV to the piloted spacecraft, then would attach the larger OTV used to launch the cargo spacecraft to the new OTV. This would create a 48-meter-long, 738.7-metric-ton stack.
The stack would move away from the Space Station on 21 November 2004. Shortly thereafter, the first OTV would ignite its engines to start the second OTV and the piloted sprint spacecraft on their way. Its work completed, it would then separate, aerobrake in Earth’s atmosphere, and return to the Station for reuse. The second OTV would repeat this performance, then the piloted sprint spacecraft would burn nearly all of its propellants to place itself on course for Mars.
The piloted spacecraft would aerobrake in Mars’s atmosphere and fire its engines to circularize its orbit on 3 June 2005. Almost immediately after MOI, the crew would rendezvous with the waiting cargo spacecraft. Three crewmembers would board the Mars Lander, deorbit, and land at the preselected landing site. They would explore the site for from 10 to 20 days. The other three astronauts, meanwhile, would transfer the Earth-return propellants stored on board the cargo spacecraft to the piloted spacecraft’s empty tanks. They would also discard the piloted spacecraft’s MOI aerobrake.
SAIC noted that the ideal trajectory for a one-year piloted Mars mission launched as soon as possible after the arrival at Mars of the cargo spacecraft on 29 December 2003, would have the piloted spacecraft depart Earth on 8 January 2005, reach Mars on 2 August 2005, depart Mars on 1 September 2005, and return to Earth on 8 January 2006. SAIC’s Earth-departure date, a little more than a month ahead of the ideal date, would increase the piloted mission’s duration by almost two months.
Launching the piloted sprint spacecraft early would, however, add an abort option to the mission. If, for example, the cargo spacecraft’s propellant cooling system failed and allowed the Earth-return propellants to escape while the astronauts were en route to Mars, then they could use the propellants that they would have used to circularize their orbit about Mars after aerobraking to ensure that their spacecraft would skim through Mars’s uppermost atmosphere on 3 July 2005. The aeromaneuver, properly executed, would nudge the piloted spacecraft’s course enough that it would intersect Earth on 15 January 2006.
SAIC explained that one goal of Phase II of the Mars program would be to seek out a