A bright blue flame of rocket exhaust shot out of the back of the engine, which sailed noiselessly through space on its way to the outer planets. But Kyle, standing three meters away resting his chin on his fist, knew the engine would be going nowhere unless they could eliminate oscillations in the combustion chamber.
"I'm going to take off the cooling jacket," he called out to the room as he reached for the floating holographic display panel on his right and touched a translucent orange button. The cover disappeared from the life-sized, holographic engine floating in the middle of the room. Without looking at his instruments, Kyle could see that the flow wasn't as steady as it should be.
"Let's take it one layer deeper and look inside the combustor." Another touch on the floating panel split the engine in half, revealing red fuel rushing into the combustion chamber forward of the exhaust nozzle. The fuel ignited to blue in the combustion chamber and shot out the nozzle into the vacuum of holographic interplanetary space. But Kyle knew something wasn't right.
With the touch of another button, small yellow arrows, highlighting small fuel concentrations that formed droplets just past the fuel injectors, popped up inside the combustion chamber. That wasn't the problem. The droplet formation was normal, but the sweeping red ribbon-like waves bouncing from one combustion chamber wall to the other were not. The acoustic waves meant there was a resonance coming from somewhere. The waves grew in intensity until reaching a crescendo as they entered the rocket nozzle. Worst of all, at the peak intensity the hologram motion froze and the simulation automatically reset, meaning a real-life rocket would have just exploded. The engine looked like it was bleeding, and Kyle couldn't figure out how to stop it.
"I think we should call Rachel in," suggested Jeff, a structural engineer with a soft Texas drawl. Startled, Kyle looked to his left. Jeff was a little late, and Kyle hadn't expected him to be standing over his shoulder. Jeff's image shimmered slightly as he moved closer to the engine because he was actually standing in an identical lab
1,500 kilometers away.
Kyle muttered to himself and clenched his jaw. He was the lead thermodynamics engineer on duty, and this problem was a showstopper. Rachel's specialty was combustion dynamics, and Kyle knew if anyone could solve the problem, she was the one. "Make the call."
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As the sun dropped towards the horizon, it threw a blanket of gold across the lazy blue-green ocean. Rachel burrowed her toes into the sand, concentrating on the grains rubbing against her skin. She wanted to make sure she was awake, that this perfect sunset was real. A fantastic end to an incredible day.
"Mom, you're being paged," Amber called from under an umbrella by a grove of palm trees where she and her father had been sampling drinks in coconut shells. Amber had finished her drink and was moving her arms in slow circles in the air. Wearing her mother's teleimmersion sunglasses, the young girl's odd ballet was really movements in a gaming environment with friends scattered around the planet.
Rachel took one last look at the sunset, turned, and headed up the beach.
"Looks like they're having a little trouble," her husband, Conner, said.
"It shouldn't take but a few minutes, and I am on call," she replied.
"Come on Amber," Conner said getting up from his chair, "let's go for a swim." Amber passed the glasses to her mother and headed toward the water.
"I'll join you soon," Rachel added with a smile. She settled into the beach chair and put the glasses on. A transparent heads-up display overlaid the sunset as the voice of her computer-generated digital assistant announced "Retinal identity verified. Welcome, Rachel. I understand you have been paged. Kyle seems to be having some trouble in the shop. I'll connect you now."
"Thank you, Rhett." The display immediately became opaque and blocked out the beach and her family in the surf.
Almost instantly she was sitting virtually in the Immersed Technology Design Facility, or ITDF in official jargon. But for the people who thought of it as a second home, it was simply the "Design Shop," or even just the "Shop." Rachel saw the holographic rendering of the interstellar engine hovering in mid-flight at one end of the room next to Kyle and Jeff.
"Okay, I'm here," Rachel called out. Kyle turned around and saw a standardized image of Rachel. Because she was using a portable unit, the system projected a constructed image based on stored data instead of a real-time image of the beach setting.
"Thanks for getting here so quickly," Kyle said. "As you can see we have a little problem." A swarm of red waves still poured out of the engine.
"The waves represent acoustic wave fronts," Rhett informed her.
"So where are the acoustic waves coming from?" she asked.
"I haven't been able to figure that out yet," Kyle answered. He was not surprised by the question. Although he could not hear Rhett's comments to Rachel, he knew that the digital assistant would inform her of the basic setup.
"Let's see if we can walk through this together and see what's happening." Using controls activated by eye motion, Rachel moved her viewpoint closer to the engine. Although she never left her beach chair, Kyle and Jeff saw her image walk across the room. To get a sense of what the system was doing, Rachel watched the engine run for a minute. Kyle stepped up next to her.
"We've been looking at it for a while now with this same display, but I can't determine the origin of the waves," he said quietly.
"I think I see something," Rachel said, as she moved a little closer. "Set the controls to 75 percent flow rate, and adjust the gimbal angle by, say, five degrees."
"Will do," Kyle replied, as he walked to his floating control panel and started entering data.
Rachel couldn't help marveling that she was vacationing in paradise with her family and, at the same time, helping to design a rocket engine a continent away. Thanks to the flawless integration of models and simulations, incredible advances in interactive and communications technologies, and a cultural revolution, the relationship between engineers and their work had changed drastically. Here they were, designing the entire engine at one time, Rachel thought. No longer were subsystems designed separately, to be integrated later. System problems, such as this one, showed up immediately. Design and testing had become one with advanced physics-based simulation capabilities.
In the beginning there were a lot of challenges. Working in an immersed environment was intense, and people tended to burn out after about four hours. Maintaining a high level of performance day after day, week after week, seemed impossible. But in the end they worked it out with the help of an unlikely acquaintance. One of the design engineers had a cousin who worked a rotating schedule on oil rigs in the Gulf of Mexico. After a lot of argument, senior management decided to try something similar, and it had worked far better than anyone expected. The designers had been organized into two teams. Each team worked for three weeks and then had two weeks off. Workdays included four hours of integrated design and four hours of individual work in their own offices. Some hours were devoted to debriefings and brainstorming to improve the integrated design sessions. The change had required a colossal shift in workplace thinking, but no one could argue with the results. Time to completion was down and quality was up.
Rachel was grateful for the change. She was spending more time with her family and had a new sense of excitement about her work. She was now on her two-week break, taking the vacation that had been postponed several times because of the rough work schedules under the old system.
"Okay, I'm ready," Kyle said. Rachel snapped back to attention. Her display turned blue with red lines streaking past as she directed her avatar to walk directly into the holographic combustion chamber. Ignoring the red acoustic waves, she moved forward until she saw the yellow arrows marking the fuel droplets forming just after the fuel was atomized by the fuel injectors. The injectors acted like an industrial-scale perfume sprayer, but with a punch. In this case, the droplets were highly flammable rocket fuel that ignited almost immediately in the combustion chamber.
"Kyle, could you please slow the flow rate." The fuel flow rate slowed so that she could see where the fuel droplets formed. "Wait a minute!" The whole design shop heard a loud pop when Rachel snapped her fingers on the beach. "I think I have it, Kyle!"
"Where?" Kyle passed through part of her holographic projection as he ran into the display.
"Right here. See how the droplets form all at once as they come out of the fuel injector? See the same pattern that forms at equal intervals?" Before Kyle could answer she said, "Rhett, what is the time difference between individual droplet formation within a single set of droplets?"
"The simulations indicate that 95.6 percent of the droplets form within 0.01 milliseconds of each other. And the time interval between droplet sets is a constant 0.12 milliseconds," Rhett replied.
"That has to be it. See the droplet formation here, Kyle?" She pointed into the fuel stream. "It has a constant formation rate."
"Oh, that's it," Kyle sighed. "I should have thought of it. That's well within the structural resonance range."
With new energy, Kyle turned around. "Jeff, please compare the frequency of the mechanical resonance in the combustion chamber with the frequency of the droplet set formation rate."
Jeff keyed a few buttons on his design panel. "They're within half a Hertz of each other."
"That's it, then!" Rachel said.
"What's it?" Jeff asked, not understanding the consequences of the data he had pulled up.
"The fuel droplet formation rate corresponds exactly to one of the combustion chamber's acoustic resonance frequencies," Kyle answered. "When the fuel droplets vaporize and burn all at once, the periodic forces from the resulting pressure waves interact with the mechanical properties of the combustion chamber. That unstable burning process increases the peak pressure of the waves until the chamber ruptures and the engine explodes."
"So all we need to do is shift the resonance frequency of the combustion chamber," Rachel concluded.
"I'll take care of that," Jeff said, as he touched his display screen a few times. "You two are a couple of smart designers."
As he finished speaking the red acoustic wave markers disappeared. The combustion instability was gone. Everyone in the room applauded. Images and voices of people who had been monitoring the design work from other labs filled the room. Rachel had almost forgotten about the other design and manufacturing groups that were linked into the shop and had been monitoring their progress remotely. One of the newcomers, a manufacturing engineer, called out to Jeff, "What changes did you make?"
Jeff raised his voice above the excited noise. "First, I had the atomization model change the hole distribution pattern with the manufacturing tolerances in the fuel injectors to randomize the droplet formation. Then I adjusted the dimensions of the chamber slightly based on the chamber acoustic model to shift the chamber resonance frequency. But when I adjusted the chamber size, the structural model indicated I had to change the weave on the composite fiber structure to compensate for some stress points the model picked up."
"Well, according to the manufacturing stress models," the manufacturing engineer said, "that composite change makes the combustion chamber stronger. We can get rid of some supporting struts, which also simplifies the assembly process. Good job!"
A moment later several team members jumped as an office cubicle, complete with pictures of the family and a coffee cup pencil holder, appeared at the back of the room. The cost engineer sitting at his desk was flushed.
"Jeff! That's fantastic!" he yelled. "I just got the update from manufacturing. Because of the reduced support structure, we can save 2 percent on engine manufacturing costs."
The whole room applauded again. Kyle cut in, "Hey, Jeff. Kudos to you and Rachel."
"You're welcome. Call any time," Rachel smiled even though they couldn't see her facial expressions. "But right now the waves are calling. I'll see you next week." The engine they had almost finished would be finalized in three weeks after a total development time of five weeks. The preliminary parts would be available even sooner. The rest of the spacecraft was being developed simultaneously in other immersed design shops, and the mission was expected to take off, literally, just nine months later. The schedule from initial concept to launch was 14 months.
Rachel sat for a moment longer observing the excitement in the room. Everyone was smiling and people were trying to slap each other's holograms on the back and give translucent high fives. It was a good feeling to turn a design problem into a design improvement.
"Disconnect please, Rhett," Rachel said. With a satisfied smile she headed down to join her family for a sunset swim.
--- This actually is an extract from a report....and a driver and an implementation for my thesis as well :-).....just philosophizing....seriously:-)
-Anup