Pancho stayed with them for the weekend. She cleaned and cooked and fed Milo and answered the telephone and drove home Sunday night and on Monday morning Harrison returned to work. He sat at his desk and studied diagrams for an adaptive control system he’d been developing with engineers from Minneapolis-Honeywell to automatically monitor and change the X-15’s gains. Voltage alterations were required to adjust the flight control system, and the stability augmentation system used in previous flights was not an effective solution.
It was impossible to set the gains in the flight control system to a single value that would be optimum for all flight conditions. The speed range was too wide. The MH-96 prototype was designed for high altitude flights outside of the atmosphere. It would automatically combine both aerodynamic and reaction controls, compensating for the reduction in effectiveness of the aerodynamic controls as altitude increased. It consisted of electrical modules and mechanical linkages designed and tested in the simulator, which had analogue computers to replicate the nonlinear aircraft dynamics.
He drank hot black coffee. He stared at a schematic of the inner-loop control architecture.
He was scheduled to make the first X-15 flight with the MH-96 installed that Friday. It was also the first flight test of Reaction Motors’ XLR-99 rocket engine, also known as the Big Engine, capable of fifty-seven thousand pounds of thrust.
He studied a memo from Bob Bridshaw at Honeywell.
Bridshaw warned that the MH-96 was a rate-command, attitude-hold system and might not observe usual speed stability characteristics if the thrust did not match the drag. More problems: the system was designed to maintain a limit cycle oscillation at the servoactuator loop’s natural frequency. The laws of gain adjustment made Harrison wonder if the gain valve would lag behind the optimum setting. It would still be a better solution than the standard stability augmentation system with pilot-selectable gains, especially during reentry.
He grunted and took another sip of coffee. Ridley walked in.
Jim, he said, surprised. Wasn’t, uh, expectin to see you today.
Runnin a program, ain’t we?
Ridley thought for a second, considered the situation.
Sure are, he said.
You think the MH-96 might disengage in flight? Harrison said.
It’s been designed to run for seventy-five, seventy-six thousand hours between failures, Ridley said.
Uh-huh.
Reset the system, you shouldn’t have any problems.
Yeah.
Want a coffee? Ridley said.
Got one here.
How long you been here?
Couldn’t sleep. Goddamn coyotes, Harrison said.
Mating season, Ridley said.
If it was up to me, Harrison said, I’d gather a posse and hunt down every last one of em.
Thankfully it ain’t up to you.
Where we launching?
Over Silver Lake.
I reckon landing might be a problem, Harrison said.
With the lakebed?
With the stick. I usually have to pull it back, keep increasin the force to keep her on the angle as I slow. I reckon the stick will have to stay dead center.
You might be right, Ridley said.
Only one way to find out, Harrison said.
Ridley sat down opposite him.
We’ll climb at seventy-five percent thrust, he said, level out at a hundred thousand feet. Then accelerate to Mach five; hundred second burn; shutdown. Then you can evaluate the system’s responses by making a series of yaw, pitch and roll inputs.
Sure the lakes are dry enough now? Harrison said.
Hell, yeah, Ridley said. Driest goddamn winter I ever seen. Joe and Neil tested em on Saturday. Say, here’s something I found out from Walker. You know why your flight was delayed til Friday?
Thought Jerry said there was a problem in the coupling?
Nope, Ridley said. The air force was conducting an ejection seat test using a tranquillized bear.
You made that up.
Did not. His name was Little John.
They named him?
On my mother’s life.
Little John?
Ejected at forty-five thousand feet.
How’d he pull the cinch ring?
Guess a bear’s got claws.
How fast was he goin?
One point four Mach.
He was supersonic?
Fastest damn bear in the world.
They should put him on the cover of Life.
Who’s been sitting in my chair?
That’s the funniest goddamn thing I ever heard.
Made one helluva mess.
He bought it? Harrison said.
Chute didn’t open, Ridley said. Poor bastard hit the runway like a sack of shit. Bull’s-eye, right in front of everyone. Damn thing exploded. Hell of a mess. They had to close the runway. Walker had to take a shower after.
This is the greatest story I ever heard, Jackie, Harrison said. How come you’re just tellin it to me now?
Ridley looked at the desk. You were kinda busy over the weekend, Jim, he said.
Oh, Harrison said. Right. Still a goddamned funny story.