“Roger. Brakes on,” Patrick said. He applied the brakes, then slowly advanced the throttles. When he was at full military power he let the brakes go, then eased the throttles into full afterburner. It did not take long for the Black Stallion to reveal its legacy as the fastest air-breathing aircraft in the world as the speed built up quickly. It leapt off the runway in less than three thousand feet and climbed at a dazzling ten thousand feet per minute to forty thousand feet.
They proceeded to the air refueling track, which led westbound out over central California to the Pacific Ocean, then descended to twenty-four thousand feet, rendezvoused with a Dreamland KC-77 tanker, a modified Boeing 777 airliner a few minutes later, made contact with the tanker’s refueling boom, and started to take on fuel. The tanker made two contacts: the first to fill up the Black Stallion’s jet fuel tanks in the wings and aft fuselage, and the second to transfer another substance into a separate, larger storage tank in the center fuselage section of the aircraft. The second transfer took much longer because the substance was much thicker than jet fuel, but after almost an hour the refueling was complete. The aircraft was now over three times heavier than it was at takeoff: the aircraft carried twice its own weight in fuel. If it had this same fuel load on the ground, it would never have been able to take off.
After the tanker departed the area, Hunter reconfigured the bomber’s computers for the next phase of flight, then began checking all of the engine and flight systems carefully. Patrick steered the Black Stallion north, then began a slow climb and gradually began applying full throttle. At full afterburner power at forty thousand feet about a minute later, they were at Mach 1.8, or about fourteen hundred miles an hour. “Airflow has stabilized and is in the green, lasers ready — we’re ready to spike the leopards, General,” Boomer reported.
“Let’s see what this thing has under the hood,” Patrick said. He hit a small control stud on the side-stick control and spoke, “Spike engines.”
“Engines spiking, stop spike,” the female computer-synthesized voice responded, adding the command to stop as a reminder. The airspeed slowed to Mach one point six, enough to tug at their shoulder harnesses. On the front of each engine, heat-tolerant vanes extended across the engine inlets, diverting airflow around the fan blades and compressor section of the engines. As the air was turned it was also mixed with tiny amounts of jet fuel and compressed. As the air-fuel mixture was squeezed, several diode laser emitters in each engine ignited it, and the jet exhaust was forced out of the back. The airspeed almost immediately jumped back up to Mach one point eight and quickly rose, exceeding Mach two, three, four, and even began approaching Mach five. The vertical velocity readout was equally as impressive — as the airspeed increased, the pitch angle became steeper and the Black Stallion climbed faster.
The LPDRS, or Laser Pulse Detonation Rocket System, nicknamed “leopards,” was Boomer’s engine design that would change the face of high-speed travel. The LPDRS engines were a new generation of advanced rocket engines that used instantaneous, pulsed detonation of jet fuel using blasts of laser energy, producing fifty percent more thrust than the conventional chemical rocket engines. Patrick was squished back into his seat as the “leopards” engines began their high-frequency hammer-like pulsing and the spaceplane rapidly picked up speed.
Finally, the engines began to throttle back and the pitch angle decreased, until they were straight and level again. The curvature of the Earth began to become apparent, although a few thunderheads on the horizon seemed to reach their altitude. “All engines stabilized and running perfectly at Mach four point five-one,” Boomer reported a few minutes later. “We’re level at flight level eight-zero-zero — eighty thousand feet. Incredible,” Patrick breathed. “Simply incredible. Almost five times the speed of sound.” He glanced at the engine readouts. “And I don’t even detect any fuel burn at this speed.”
“The lasers are hot enough to ignite the compressed air, but we use a few hundred pounds of fuel an hour to help the process along,” Boomer said. He checked some position readouts, then said, “We can turn eastward now and I can have you in Washington in about forty minutes, sir.”
“You could…but that’s not why I came on this ride, Boomer,” Patrick said. “Besides, we have a job to do too — this isn’t just a taxi ride. Let’s do it.”
“Yes, sir,” Noble said excitedly. He checked some more readouts; then: “Ready for suborbital burn, sir.”
“Roger that,” Patrick said. He took one last sip of water from a canteen, then flipped his oxygen visor back in place, tightened up all of his straps, and situated himself in his seat. “Here we go,” he said. “Computer, commence suborbital insertion burn.”
“Commence suborbital insertion burn, cancel suborbital insertion burn,” the computer responded. When the countermanding order was not received, the computer said, “LPDRS engines activated…ignition in three, two, one, zero.”
At that moment they heard four distinctive and rather unnerving “BAARRK!” sounds reverberating through the fuselage, and the XR-A9 suddenly accelerated so fast that a puff of air was forced out of Patrick’s lips. Patrick’s vision blurred and tunnel-visioned as his eyeballs were squished against his skull, but the last thing he saw clearly was the airspeed jumping past Mach five, less than a minute after main engine start. As the airspeed increased, the flight control computer nosed the XR-A9 higher and higher, until their climb rate now exceeded one hundred thousand feet per minute. At that point the readouts switched to thousands of feet per second — two, five, then ten thousand feet per second. The Mach numbers, or times above the speed of sound, were approaching double digits.
Once above three hundred thousand feet at the edge of space, the spikes in the inlets of the four LDPRS engines closed even more. Instead of using the atmosphere to burn jet fuel, the “leopards” engines used borohydrogen tetroxide, or BOHM — nicknamed “boom”—as the oxidizer. The thick soupy substance was a hundred times more efficient as liquid oxygen, and increased the specific thrust of each engine by several thousand percent.
As the numbers climbed, so did the G-forces — the number of times the forces of gravity was being exceeded on the human body. Patrick had pulled as much as twelve Gs before, but only for a few seconds at a time. The G-forces now were not excessive, only about 2.75 Gs (times the force of gravity), but it had been going on for a relatively long time, something that Patrick was definitely not accustomed to. Patrick practiced moving his arms to activate switches on the instrument panel in case voice commands didn’t work, which was a real possibility since his chest felt like someone was sitting on it, and it took effort and control to breathe, let alone speak.
Patrick began to feel as if he had been tackled by the entire Penn State linebacker squad. His vision blurred, then tunneled, and the air was forced out of his lungs — fortunately the life support system immediately sensed this and started shooting pure oxygen into his lungs under pressure to keep him from asphyxiating. Although he was quite uncomfortable, the pressure was not painful, just disconcerting. Could a crewmember stand this kind of pressure flight after flight? he wondered. How long could someone serve with the Black Stallion before something bad happened?
After what seemed like an eternity — but he knew from flying the simulator that it was less than eight minutes — the engines shut down. Suddenly the cockpit was deathly quiet and the G-forces, which had built up to about four times the normal force of gravity, stopped suddenly as well. The sudden quiet and relief from the pressure on his chest made Patrick pause in fear. What caused that sudden stoppage? Was everything OK? Was this the end…?