The first step in my equipment setup was for me to replace the old-fashioned spring-scale force-measuring kludge with an electronic load cell I’d picked up surplus. It fit nicely with the help of a battery-powered drill and a box of bits I’m never without. Then we mounted the rocket motor, a remarkably compact contraption wrapped with a tangle of wires and tubing.
“Ceramic?” I looked up quizzically when I noticed the material the engine casing was made of. “I presume there are some reinforcing fibers in it.”
He smirked. “Just you mind your own business and hook up them wires.”
“How do you cool it?” I asked, remembering a study of the Space Shuttle Main Engines I’d reviewed. NASA had been working on a nearly pure copper nozzle liner cooled by liquid hydrogen.
“MHD and thermal emissivity,” he replied cryptically. “Hurry up, I want to run about a dozen tests this afternoon.”
I installed ten thermocouples in wells he had provided in the motor casing and nozzle, found a spot on the concrete pad to mount a radiometer calibrated to act as a radiant energy thermometer so I could measure exhaust plume temperature, and ran the wires and cables back through a trench to a bank of well-shielded signal conditioners, and from there back to the control bunker, where I set up my computer. I also set up three video cameras, one normal, one infrared, and a special ultraviolet unit I had developed myself using some tricks from a NASA technical brief. These were tied to the computer, overlaying the images with synchronized time and data. I installed filters on the infrared and visible camera lenses to protect them from the intense light Jake expected, then calibrated the system, checked all the channels for function, and was ready to go.
First Patti, then David, came from their respective bunkers carrying small tanks of rocket juice. “You indicated you were going to use a tripropellant,” I noted. “What combination are you using?”
“Ah-well, that thar would hafta be a secret,” Jake said with a mysterious grin. “Call this mix Wallbanger.”
I rolled my eyes. “OK, be that way. Let me guess. I know you use hydrogen peroxide, I’d guess about 95 percent concentration, as an oxidizer.”
“Well, let’s just say it ain’t the stuff that comes from Clairol,” he replied with a confirming grin. “Course, that don’t mean I won’t also be trying liquid ozone.”
“Yeah, right,” I said recognizing a quickly dismissed possibility we had discussed in our letters, and retaliated with an even scarier possibility he’d suggested. “Or maybe tri-fluorine.”
“Or di-lithium,” he replied.
“Naming it after a drink probably means you’ve got some alcohol in it.”
He shrugged. “Could just mean you’d only dream up this mix with a couple of stiff drinks in you.”
I patted my equipment. “I’ll have a pretty good idea of the third component when I see the color of the exhaust, anywhere from near infrared up through ultraviolet B and then some.”
Patti and David scanned the area for unexpected visitors, then scurried back behind the earthworks to the control bunker. Jake primed the system and ran down a simple checklist, all remarkably informal to someone used to elaborate NASA test rituals. It was more like a mechanic planning to start a rebuilt gas engine.
I started the computer and video recordings, and he flipped the “fire” switch. At first, the little bunker sounded like the Concorde was parked just outside doing a run-up check with full afterburners, but the sound quickly changed to a piercing shriek.
“Damn,” I said as he switched the thing off about three seconds later, “I’ll need to zoom back for the next test. Exhaust plume went way off screen.” I glanced at the computer screen. “And the radiometer went off scale. Hell, I had that thing set for eight thousand degrees Kelvin, the hottest rocket exhaust I’ve ever heard of.”
“Well, now that’s what comes of conventional thinking,” Jake said with a self-satisfied grin. “Don’t worry, that was just a little blip. We can run it again. Can you get an estimate of exhaust temperature from the UV video?”
“Yeah.” I rewound the tape. “I’ll reset the radiometer range higher on the next test. I’ve measured plasma spray temperatures over twenty thousand, but nothing that high from a purely chemical reaction.”
Jake shook his head. “There’s that conventional thinking again. What sort of nozzle temperatures did you get?”
I stared at the display. “Crap, the thermocouples must have slipped out. The hottest is only 148 degrees.”
He nodded. “Sounds about right.”
I stopped the tape and pressed play, then turned to stare at him. “How the hell do you keep it so cool? A laminar flow boundary layer?”
He shrugged. “MHD and Thermal Emissivity. What’s the tape show?” One side of the screen had a computer-generated color-temperature scale corresponding to the false-color images made by the camera. I shook my head. “Man, the calibration has to be off. I’m getting around 12,000 degrees.”
Jake whooped and jumped in the air, then came down, slapped his thighs, and did a little dance. “Right on target,” he sang, then he froze, looking at me like a kid at Christmas about to get a package from a rich relative. “What kind of thrust did it make?”
I read the figures, and he punched them into a calculator. “Bull’s-eye,” he rejoiced. “Tom, if you want specific impulse, you gotta have exhaust velocity. If you want exhaust velocity, you gotta have pressure. If you want pressure, you gotta have temperature.”
I nodded, tolerating the lesson in basic thermodynamics. “But temperature is limited by available materials,” I observed. “You have to have a way to hold the reaction. You told me you were trying to build a ship that could be turned around in half a day. Gas it and fly again. You need a conservative design that won’t eat itself alive every time it runs.”
Jake smiled patronizingly. “You’ve been looking at too many old chemical rocket engine designs, m’boy,” he said. “And not enough at nuclear designs. Come on, put another quarter in that video game and let’s do it again.”
The second run with Wallbanger went flawlessly, a full thirty seconds, then we switched to a fuel system called “Meringue.” Jake was a little disappointed with it, as it produced about 12 percent less umph than he had expected, but said the name came from the mixture being exceedingly touchy, and figured that had something to do with it. “Popcorn” worked satisfactorily, but the performance was lower than the others, as expected. Then we tried “Baked Beans,” also an unimpressive performer which, I gather, used some hydrogen sulfide to try to boost reaction rate. “Cream Puff” was even better than Wallbanger.
I asked him where he got his fuel system names, and he admitted his loyal techs dreamed up most of them. I suggested that his loyal techs were probably underfed.
“Now,” Jake announced with a flourish as Patti scurried back into the bunker after depositing her empty fuel canister, “we will try my favorite… Pan Galactic Gargleblaster, nothing less than the most potent rocket fuel ever designed by humankind. Everybody ready?” We nodded. “Drum roll.” David drummed his pencils on the bench. “Lift-off!” He pressed the ignitor button.
The ground shook, there was a terrific bang, and the engine simply disappeared from my monitors, followed by what looked like a little rain squall with a bit of fog.
There was a moment of silence as we stared in disbelief at the monitors.