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The rest of the class filtered out, leaving the Commander, Langley, and a looming blackboard filled end to end with chalk. There was a time and place for old, reliable technology, especially when it compelled her students to take notes and not just wait for summaries to be posted.
There was an inconvenient side effect, though… she rubbed her thumb against her index and middle fingers, feeling the dust between them. Her kerchief wouldn't be enough, at least without water.
“Here, Langley.” The Commander passed her a wet wipe.
“Thank you, Richard.” She wiped the dust off and dried her hands with her kerchief. Normally, she would have slipped her gloves back on, but she had a special lesson she needed to start.
(No chalk necessary.)
“Where were we?” She knew, of course, but she asked anyway.
“The transonic regime.”
“And?”
“How you’d design a plane around it.”
“Good.” Langley nodded, naturally starting to pace in front of the desk Richard was sitting at. “There are many factors at play – the most noticeable is probably the wing shape, right?”
“All bent back?”
“Yes. Can you give a guess as to why?”
“It looks cool?”
“A serious guess, please.”
“Uhm… maybe it’s something to do with the sonic boom? It’s all angled, isn’t it?”
“Not precisely. Those wings do perform better when they’re inside the cone of the boom, but there’s a more basic reason. It’s all about delaying shocks. You remember shocks, yes?” She stopped dead in front of Richard, gazing right into his eyes.
Richard nodded. “The speed drops, the pressure increases, it’s bad for your plane.”
Back to pacing in front of the desk, heels clicking. “I would have used more words, but yes, that’s about it. Knowing this, we want to decrease the airspeed going head-on, straight into the wing. It would seem like the only way to do this is by slowing down, making the whole thing a moot point, but…” Langley gave Richard an expectant glance.
“If it’s straight on speed you’re worried about – perpendicular to the edge of the wing – you could just angle the wing?”
“Exactly!” Langley grinned. “I think that’s a relevant lesson for you, especially, Richard. Not every problem needs to be tackled head-on, or can even be approached that way safely. Wouldn’t you agree?”
“I mean, I didn’t need supersonic wings to teach me that…”
“But you agree?”
“Yes, I suppose I do. So I sweep my wings. What’s next?”
“And then there's Whitcomb’s area rule. When you have a plane around the speed of sound - above or below - you want the cross-sectional area of the plane to follow a smooth curve,” Langley said, tracing a hump in the air with her finger.
“Wouldn't it already be…?”
“No, not if you just made the body of the plane a plane old cylinder. When your wings start going out, you need the plane to narrow down in turn… it’d be like…”
“A girl's waist,” Richard said.
“Like a Coke bottle,” Langley replied, a bit stiffly.
“They never compared it to–”
Langley sighed: “They did, yes. They called it the Wasp Waist or the Marilyn Monroe.”
“I… I think I’ll need a physical example.” Richard said, a dumb smile starting to spread across his face. “Hands on, even.”
“Richard…” Langley really, honestly tried to summon some disappointment in her voice. Promise. Her gaze flitted to the door. The last class of the day had just been excused.
“Maybe you should get a little closer,” Richard suggested. “Make sure I can hear properly.”
“You’re at the front of the class.” Langley sighed. But it was a class of one. The battle was already lost, and they both knew it. She circled around the desk and slid in, and most certainly did not lean into him when he wrapped an arm around her. That would be an improper thing to do, after all.
“Whitcomb, you were saying?” Richard breathed, his breath tickling her hair.
“Well, that was most of it covered…” Langley said. “Narrow the craft into something like a waist as the wings take up more area, then flare the body out once the wings taper off.”
“And you’ve got your flying Coke bottle,” Richard said. “You want to grab a soda later?”
“I’ll consider it,” Langley said, trying her best not to look him at the eyes. He laughed, and close up against him, Langley could feel vibration. He was, of course, bigger than her…
(Leaning in closer, she could hear the steady beat of his heart. More combustion engine than jet engine, really, boom boom boom, not the continuous flow of a turbine.)
The door flew open. “Heya, Langley I was wonderin’ if you could–” Shouhou came to a screeching halt, nearly lost her balance (blame those towering heels), and then turned right back around. “Pardon me, I’ll be excusin’ meself now…”
Langley’s cheeks immediately bloomed red, but before she could sputter a justification for herself, the Commander gave a cheery “See you!” and Shouhou left, shutting the door securely behind her.
Several moments too late, Langley leapt away from Richard and threw herself back into teacher mode. “Vortex generators!” She squeaked. “I really should have mentioned them back with swept wings.”
The Commander was wearing an unbearable grin. Low aspect ratio. Very toothy. Langley couldn’t bring herself to find it irritating, embarrassed as she was. Fortunately, he indulged her: “What’s a vortex generator?”
“It’s some feature intended to create a vortex in the air. There are several uses for them, but one is that a vortex can serve as a good way to stop any air that’s flowing down the wing from picking up too much speed as it travels down.”
“It’s flowing sideways?”
“It most certainly is,” Langley said. “You’re not making any of that wind speed disappear when you angle a wing – it’s just creeping down the length instead of perpendicular to the edge…”