After that Bleeker and Gershon had crawled all over the MEM, putting the subsystems through comprehensive tests. And every damn one of those tests had given them problems which had needed diagnosis and repeated testing.

There had been that odd, sour smell coming from the environment control system in the surface shelter, for instance, which they had finally traced to a piece of scuffed insulation slowly scorching behind a panel. The electrical power system had shown some severe faults, with whole panels of instruments just cutting out. Meanwhile the inertial guidance system was a pig, wallowing inside its big metal sphere, constantly losing its lock. And the MEM’s big antennae complex had gotten stuck, and for a while it couldn’t talk to the Apollo or the ground…

Relationships between the crew and the ground had gotten strained in all of this. As they wrestled with the craft, Bleeker, as commander, had become concerned that Houston was reluctant to make any compromises in the scientific and PR elements of the flight plan — which, as far as Bleeker and Gershon were concerned, came a long way down the list in comparison to the engineering objectives of the mission. So Bleeker, showing an unexpected assertiveness, got into battles with the flight controllers. He canceled TV broadcasts, and he blue-penciled whole sections out of the flight plan.

At one point the capcom told the crew that the controllers were plotting to bring the Command Module down in a typhoon, and Gershon suspected it was only half a joke.

Finally Gershon had gotten so sick of the problems that he’d taken a little plastic juice-dispensing lemon from the food lockers, and hung it up between the MEM’s triangular windows, in full view of the onboard TV, to show what the crew thought of their new ship.

All Gershon could hear was the rattling thump-thump of the ascent engine’s ball valves opening and closing. The noise was oddly comforting, giving him a feeling of security, that the mission was unfolding as it should.

The Earth slid away from Gershon, as the ascent stage climbed smoothly up toward its rendezvous with New Jersey, the waiting Apollo; it was so smooth it was a ride in a glass-walled elevator.

There wasn’t much for Gershon to do. Because the ascent-stage engine had no backup — it had to work — it had been made as simple as possible, with just two moving parts: ball valves, to release propellant and oxidant into the combustion chamber. The engine, fueled with oxygen and methane, had no throttle or choke; all you could do was throw the master arm and turn the engine on, and it would just burn steadily for ten minutes or so, just as it was designed, to lift its crew off Mars and back to a parking orbit.