They finished the first checking of the cargo, and went on out of the shed and across the sunbaked tarmac toward the lighter. The Tangiers Poe was a great concrete oval, ringed by warehouse sheds and repair huts and administration buildings. All of Earth's space shipping was conducted here, close to the Mediterranean coast of North Africa, where perfect flight conditions were rarely marred by clouds or rain or cold. Where flight plans include three variables--a lighter moving from a moving Earth to a moving Space Station--no one can afford delays caused by bad weather. In the shed, the cargo handlers loaded small open-sided carts, which were then driven across the field to the lighter. The cargo for QB came out on the second cart, and Glenn Blair supervised its careful stowing and tying down in the hold, then made the second check after its specification line on the manifest. The first checkmark meant that he had found the seven crates in undamaged condition in the shed. The second one meant that he had accepted delivery onto the lighter. Eight more checkmarks would be made before the cargo was finally delivered to QB. All cargo and personnel traveling between the Earth and the Moon made the trip in five stages. Stage One was transit from the surface of the Earth to the Space Station, aboard a torpedo-shaped ship familiarly known as a lighter. Stage Two was aboard the Station, during its fifteen-day trip from perigee, four hundred miles up, to apogee, eighty-four thousand miles from Earth. (Space Stations One and Two circled the Earth, one at perigee whenever the other was at apogee, so that a shipment left for the Moon every fifteen days.) Stage three was via a ship technically known as V-T-V (vacuum-to-vacuum) but informally called the Barbell, because of its shape. This stage also took fifteen days, and covered sixty-two thousand miles, terminating at its meeting with Space Station Three, eighty-four thousand miles from the Moon. Station Three orbited the Moon every fifteen days, so that this lap of the trip, Stage Four, took seven and a half days. And finally Stage Five, via another lighter, was from Station Three at perigee two hundred fifty miles above the Moon to the surface of the Moon itself or, as in the case of the seven aluminum crates from Los Angeles, from Station Three to Quartermaster Base, the maintenance satellite for the whole system, in permanent orbit two hundred miles above the surface of the Moon.