Free Titan by Stephen Baxter Page A

with concrete.
    The master alarm clamored again.
    Lamb punched it off. “What now?”
    Angel checked. “We’re losing hydraulic pressure, Tom. Shit.”
    And suddenly the orbiter dropped like a stone.
    “Flight, Egil. I got you a diagnosis on the APU situation.”
    “Go.”
    “We think we got a fire back there, Flight. In fact the system signature is looking a little like STS-9.”
    STS-9 had been John Young’s last flight. During the final landing approach on that flight, the power units had caught fire; all but one had failed on the way to the ground.
    Egil said, “Probably we have a hydrazine leak from one of the APUs. If that’s the case, we’ll have volatile hydrazine spraying over the hot surfaces in there.”
    “STS-9 was survivable,” Fahy said. “The crew got down safely and walked away.” That was true; the power unit fire—even a subsequent explosion—hadn’t been detected until the orbiter was back on the ground.
    “But on STS-9 the leak occurred just before touchdown. Here, the leak came a lot earlier, during entry…”
    “Flight, Prop. If we have had some kind of rupture of the OMS fuel lines, maybe that’s linked to these APU problems. The position of the APU tanks, in the tail section—”
    “Save it for the board of inquiry. Egil, Flight. What’s the worst case?”
    “That we’ll be looking at an APU loss scenario. We’ll have to recommend a ditch, Flight.”
    Fahy remembered, now, that the orbiter on STS-9 had been Columbia.
    For long seconds, it was like a roller-coaster ride—what the controllers called a phugoid mode—as the control system tried to stabilize the trajectory. When the oscillations stopped, the orbiter was still deep in blackout.
    Lamb flexed his gloved fingers, and closed his hand carefully around his hand controller. “Let’s see how this mother flies.”
    Benacerraf knew it was time for the first big maneuver in the atmosphere, a wide, banking S-turn. On a nominal descent, the automatic systems were generally allowed to fly the orbiter most of the way home. Today, it looked as if Tom Lamb wasn’t going to trust the automatics any more than he had to. Looking at the broad back of Lamb’s gloved hand wrapped around the control stick, Benacerraf felt obscurely reassured.
    “ADI rate switch to high. Roll/yaw switch to the control stick…” Lamb clenched his hand. He pulled the stick to the left.
    The orbiter banked to port. The Pacific tipped up, a glittering blue skin in the morning light. Shadows shifted across the cabin, sending complex highlights from the instrument surfaces.
    The master alarm sounded. Angel killed it. “We lost another APU, number three. Number one still online.”
    Lamb leaned into his control, and the orbiter pitched over further.
    “I’m only showing seventy degrees bank,” Lamb said. “It’s all I can get.”
    “You figure the elevons are screwed?”
    “It’s that low hydraulic pressure. Or maybe the last APU is going down. God damn this. I’m at the edge of the envelope, here.”
    Now, at Mach 18, Columbia rolled to the right. Below the prow, Benacerraf could see the coast of California, a brown line coalescing along the misty horizon, tipping up as the orbiter rolled.
    “—Houston. Columbia , Houston. Can you hear me, Tom?”
    The blackout was over. Benacerraf felt a surge of relief, illogical, profound.
    Lamb said, “ Columbia , copy. Holy shit, Marcus, is that you? How do you read?”
    “Columbia , Houston. We read you fine. Tom, we read you low on energy, and off the ground track.”
    “Tell me about it. I went phugoid back there and came out low energy. Houston, we’re down to one APU up here, and I think we may be losing hydraulic press. The elevons aren’t responding too well. Going into the second S-turn.” Lamb leaned to the left, dragging the control stick.
    “Copy that. We see you rolling left. We have you at a hundred and fifty-thousand feet, Mach 9. Looking good. Just like barnstorming old Copernicus,