Aurora by David A. Hardy Page B

missions had been inconclusive to many scientists, sadly.
    Meanwhile, the most important item was to unload and set up the Blimp. Aurora set to with a will, unpacking the incredibly thin but strong material of the envelope while Vitali Orlov erected the struts for the cabin and motors.
    â€œWhy can’t we use a proper airplane?” Aurora asked, more to make conversation than anything else.
    The Russian engineer pulled a face. “Oh, when we decided early in mission planning that only way to explore large area of very difficult terrain is from air, we looked at various designs for aircraft, but no good.” Orlov normally spoke perfect English, with an American accent—he had spent some years studying at MIT—but occasionally, especially when he felt he was “lecturing”, his sense of humor led him to parody the stereotypical Russian.
    â€œPlane would have to travel six times faster in Mars air than it would on Earth to give same amount of lift, yes? Would need two-and-half times as much power, too. Then there is power-plant. Air-breathing engine with propellers or jets—no good! Have to use rockets, electric power, or glider? Need be glider with bloody big wingspan. So, no plane. Many problems. No runway. Small range. Big wings hard to pack to bring here too. You see difficulties?”
    Aurora nodded, then said “Yes. I see. Well, anyway, I can’t wait for my turn in the balloon.”
    â€œIs not balloon! Is what we call hybrid—part lighter-than-air, part aerodynamic airship, yes? And needs only quarter of power—less, even—than on Earth. Is filled with hydrogen—quite safe: no oxygen in Martian atmosphere to make explosion. Electric power for propellers from solar cells. Easy!”
    The envelope was almost laid out on the desert. “But it’s enormous!”
    The gasbag was in fact just over 100 meters long. But only its size was intimidating. It was being filled with stored hydrogen from the electrolysis plant back at Base; this was extracted from water-ice—H 2 O—which of course produced twice as much hydrogen as oxygen. The latter was used for their life-support packs. Once the bag had been inflated and the cabin attached, the Blimp floated above the ground, tugging gently at its tethers in the light wind. It was obvious the Blimp was going to be a joy to use, and simple to operate.
    By the time the task was finished, the Sun was settling redly into a bank of haze, back in the direction from which they had come. The remains of the dust storm created a splendid display of colors, with separate layers of orange, crimson, magenta, violet and Prussian blue swirling towards the zenith. Stars appeared, and Aurora wished she had time to fetch out her paintscreen. Later, she told herself, shooting off a few frames with the tiny digital camera she always carried on her suit.
    The crew spent the night in their rovers, which were relatively large and well equipped. Tomorrow they would erect another inflatable, this time full of oxygen, as a pressure dome. Officially, this should have been their first job, but they had all been eager to see the Blimp aloft, and one more night of slightly cramped discomfort would do them no harm.
    * * * *
    Their camp was not in the best position for a test flight, as they were near the top of the Tharsis bulge—the volcanic upland area that dominates Mars’s northern hemisphere. This meant that the atmosphere was even thinner here than elsewhere on the surface. But nearly all of their flights would take them westward, towards Valles Marineris, and where it was safe to do so they would actually be descending into the canyons, within which the air was actually measurably thicker than up on the surface.
    Such was the excitement among the crew that straws (actually lengths of electrical cable) were drawn to see who should be first to go aloft. All of the members of the mission had, as an essential part of their