There was always going to be an explosion, everyone said. Acid and alkaline, they said. Different worlds. A blowup was bound to happen, and poor little Carol, caught in the crossfire like that.

Of course, they said all that after the divorce. Before, when the dashing young Starfleet officer met the History doctoral student at a conference on mid-twentieth-century military conflicts, when he'd been trim and tall in his uniform and she'd been short and untidy and smelling vaguely of patchouli, immersed in the culture she was writing her thesis on, it had been a great romance. Opposites attract, everyone said. Yin and Yang, they'd said. The wedding pictures looked happy enough, her father in dress greys, her mother in beads and bare feet.

They couldn't have been entirely incompatible. They'd made her, and no matter what anyone said about the volatility of her parents, she loved them both, and they were good to her. She missed her daddy when he was away, but when he was home he'd fly her out to San Francisco for his entire leave.

The day she turns eight, he takes her into Starfleet HQ. She follows him through the gleaming halls and tries to match his crisp stride and posture, shoulders straight, head high, annoyed at her soft soles for not snapping off the floor like his boots do.

She glories in the way he doesn't hold her hand. She's eight, now, after all, a big girl. He trusts her to not get lost or wander off, and when they turn left through a door (she resists the urge to go through it several times to make it whoosh. Only babies do that!) she discovers that he's trusting her inside a laboratory. Benches and tables neatly covered in scuffed equipment fill the room, and on the far side is a giant window into an even bigger room, with a crowd of officers - mostly in blue lab coats, with a few in red and gold - bustling around in front of it, doing things to banks of computers. He settles safety glasses on her face, just like the ones the real scientists are wearing, and considered her for a moment.

"Well, sweetheart, it's nearly right." Her father turns and calls out to one of the officers currently bent over a datapad. "Hey, Kieu! Where's that equipment we were talking about yesterday?"
"Cabinet C, top shelf!" she calls back, without even looking.

Her father took her hand this time and leads her over to a cabinet in the corner. She waits patiently while he opens the door and shuffles things about on the top shelf, and then he turns around, and - and. And. Oh. Oh, wow. It's a lab coat just her size, in Starfleet Science blue, with the Starfleet crest on the left breast pocket, exactly like the ones the scientists are wearing. One of the scientists is a species she doesn't recognize, about her size, and he - she? it? other? she doesn't know the physical gender cues and decides she'll call it "them" until she's introduced and knows their name and preferred appellation, at which point she'll switch politely like Mum taught her - watches her carefully and opens their mouth in what Carol is pretty sure is a smile. She grins back and mouths "thank you!" at them. They give her a thumbs-up and turn back to their work.

The closures are unfamiliar to her, and Daddy helps her to do them up. She thanks him, too, and admires her distorted reflection in the metal around a fire extinguisher. Wow.

"It's not gold like mine," her father starts, but she cuts him off.
"No," she says. "It's perfect. It's, it's just, it's - " there aren't really any words, so she flings her arms around his waist and squeezes as hard as she can, until he laughs and pretends he can't breathe.
"Now for the rest of your present," he says, and she can't believe there's more. He motions her over to the window, and there's a tall lab stool that he lifts her up to stand on so that she can see over everyone's heads. Kieu, the stocky, dark-haired woman who'd directed them to the cabinet, comes over to join them, tasks apparently finished for now.
"You must be Carol! Welcome to Starfleet."
Carol beams. "Thank you," she checks the rank pips, "Lieutenant-Commander!"
"Just Kieu's fine, dear. Your dad tells me you're really good at math, and I don't stand on ceremony with future co-workers. Want to have a guess what we're doing today?"
Carol thinks her face might actually break in half from smiling, but she looks through the window and examines the room on the other side. Its walls are plated in thick metal, bearing scorch marks a little like the ones on the bottom of the pot she'd ruined when Mum tried to teach her to boil eggs and they'd both got distracted. There's a long thin tube suspended in the middle of it, but it's hanging weirdly, pulled off to the left. She thinks hard.
"Daddy says starships have their own gravity. Is that what's happening in there?"
"Your dad was right, you are clever. Yes, that room has its own gravitic field , to help with safety for the test we're running."
"Something to do with fire? Is that a rocket?"
"Bingo! It's just a scale model - that means something that's the same shape, but a lot smaller, usually for testing purposes - so that we can test a new propulsion system we've been developing."
Carol files away the definition of "scale model". "What's it going to propulse?"
"Propel, sweetheart."
"Thanks, Daddy. What's it going to propel?"

Kieu grins at her. "Anything we want. My personal favourite option is some neat little sensors that Meteorology's knocking up - we can shoot one of our rockets into the atmosphere from a starship, and when it blows, it'll scatter them across twenty kilometres of atmosphere, and the wind'll catch them and take them even further. To anyone on the surface, it'll just look like a meteor."
"And that," says her daddy, "means we won't risk violating the Prime Directive. Remember I told you about that?"
Carol gives him her best insulted look. "Well, yes, Daddy. I am eight. I remember things." He laughs.
"You're doing better than a lot of people, then, kiddo. Hush - the test burn's about to start."

A technician counts down from thirty, and the computers light up like stars coming out at night. It's nothing, though, compared to the light coming from behind the window. It brightens, and brightens, and the glass darkens in response, and there's a jet of flame like nothing she's seen before, it's blue, and it's glorious. She can't hear a thing, and guesses that the room must not have any air in it. Daddy explained that to her last time she visited. She wishes she could hear the noise it would have made in atmosphere.

By the time the test is over, Carol is leaning so far forward that she's in danger of falling off her stool. Her father ruffles her hair and she swats at his hand in protest.
"Liked that, huh?"
"I loved it!"

It turns out there's one more surprise left in store. One of the work benches in the back of the room, well away from the banks of computers, has a box on it that's wrapped in what looks like scrap paper, with scribbled and crossed-out equations on it. It's strange birthday paper, and she says so. Her daddy looks sheepish, and explains that it was all they had on short notice.

Inside is a pair of plastic drink bottles, scissors, a knife she recognizes as a kind she's not allowed to use yet, some duct tape, and some cardboard. She looks up at her dad, confused, and he rolls up his shirtsleeves and hands her a datapad. There's a program already loaded and running on it - "Water Rocket Design and Simulator", it's called.

She colours her completed rocket purple and draws a window on it, with two people inside. One's wearing command gold, and the other, smaller, person is wearing blue.

They drive out to the hills across the bay, to a park where she can see the Golden Gate bridge and Starfleet in the distance, and there are a bunch of people running around next to a row of rockets mounted on some tubing. They fill the rockets with water and start up something that her daddy tells her is an air compressor, and one by one, the rockets tremble and pop off into the air. Some of them don't go very far, but she has to shade her eyes to watch hers as it arcs up into the sky.
"Just a matter of pressure," says Daddy.

When she gets home, she shows Mummy the lab coat and the video of the rocket soaring. Mummy's not pleased, Carol can tell.
"I think I know what I want to be when I grow up!" she tries. This is a safe topic of conversation. Her mum, an academic to the core, has always encouraged Carol's interests and plans for the future.
"That's nice, dear." says her Mummy, and says no more about it.

Later, when Mummy thinks Carol's asleep, Carol overhears her talking to Daddy on the phone.
"- took my daughter to a weapon test session, Alex, and now she wants to join Starfleet. Starfleet! Yes, I know she's your daughter too. We talked about this, though. Exploration be damned, Commander Marcus, you're a military organization. You have cadets, for goodness's sake, and I will not have you conscripting and indoctrinating Carol. She's bright, you know she is, and turning her into a... a grunt would be a waste, an absolute waste!"

The conversation goes downhill from there, and Carol goes up to her bedroom and hugs her pillow until she falls asleep. The next day, her mother buys her a book - it's an old book, originally printed on real wood-pulp, with nothing interactive or even any video - from the twentieth century, about an even older war. It's by someone named Collier, which is Lucy-at-school's-surname.

"We'll read this together, Carol, and you can ask me any questions you like," says her mother. She says, "this is what war does, even now, and this is what your father does."

Carol doesn't see Starfleet's gleaming laboratories or jets of flame in the mud and blood of the book. It's more alien to her than... well, than the aliens who attend the university where her mother teaches History. Rockets and torpedoes explode, she knows that, but when she closes her eyes, she sees her rocket soaring, and thinks of stealthily mapping stormclouds.

Carol grows up, and attends a civilian university, which pleases her mother to no end. She graduates with her Master's in Physics and Chemistry, and helps a doctoral student develop a more efficient fuel for short-range propulsion. Just a matter of reaction mass and pressure, really. Every year, she takes the oldest students at the local primary school out of town to a field, and they launch bottle rockets together. She always colours hers purple, much to the amusement of the students, who are definitely much too mature to want to use sparkles and bright colours on their own rockets. They solemnly tell her they only do because it makes Miss Carol smile, but she sees them sneakily scoping out their favourites when it comes time to choose materials.

She's grown up since she and her mother read "My Brother Sam is Dead", and she knows that a weapon is a weapon, whether it's bright and shiny and fired at a distance or inefficient and stinking and rammed like a bayonet through the ribs of someone you're staring in the face.

There will always be weapons, though. She can make sure they only hit what they're aiming at. She loathes the idea of collateral damage, and calls it what it is - civilian deaths - in every one of her papers, without fail. Her mother attends her graduation and celebrates with her. Her dad's off-planet, but when she gets accepted into Starfleet Academy, to a shortened program for students with pre-existing qualifications, accompanied by a promise to support her in her Ph.D. research in advanced weaponry, she builds a new water rocket and launches it. She watches it until it lands, further away than any of her rockets have before and startling a cow, and as she trudges over the field to collect it she attaches video of its flight to a picture of herself holding a battered child-size labcoat and an acceptance letter on Starfleet letterhead, addresses the message to Admiral Alexander Marcus, Starfleet HQ, and hits send.

A year later, Carol finds herself, along with several other cadets, in a room that's empty save for a pair of poles attached to opposite corners and forming an X in the centre. Her class is comfortable in zero-gee now, and they've arranged along a wall, velcro-tipped gloves helping them to maintain their orientation with ease. It's a far cry from the flailing groundpounders they'd been at the beginning of the semester, when they'd struggled gracelessly to orient themselves.

Nobody's vomited in weeks. Carol is extremely glad of this.

"Marcus!", calls the instructor. "You're up first! Jaunt to the centre and use the poles to bring yourself to as complete a stop as you can. Once you've done that, let go."

Carol is not extremely glad of that, though. Going first has not been her strong suit. She lacks the physical coordination of some of the other cadets, particularly the ones aiming for Security or Command, and she likes to see how other people complete tasks so that she can practice in her head beforehand.

"Good luck!" whispers Christine, and Carol pushes off - very gently, a dislocated shoulder early on in the course had taught her a lesson about mass and inertia that someone studying for a doctorate in Physics really should not have had to learn that way - towards the centre of the room. She misses the X slightly, and slides herself along the pole she does manage to catch until she's at the centre, spinning gently in place but not moving perceptibly towards any of the room's six walls. She lets go of the pole, and her stomach twitches ominously.

She will not vomit, she tells her digestive system and inner ear sternly. She won't break the class streak.

"Clear, Marcus?"
"Clear!" she answers, and flinches when the poles telescope back into the corners, leaving her floating freely with nothing to grasp. To make matters worse, her flinch has affected her orientation, and now her slight spin is around two axes, not just the one she'd been rotating around before. She swallows, collects herself, judges, and shimmies in the way they'd spent their first weeks practicing, and halts her spin, coming to rest facing the instructor and only around twenty-degrees off from his head-foot line.
"Good job," he says, and Carol resists the urge to smile. He's a good instructor, but he's stingy with his praise.
"Thank you, sir."

He addresses her entire class.
"I'm only going to say this once, folks. We've been practicing manoeuvering in zero-gee in preparation for when whatever starship you're on inevitably suffers some kind of technical issue and loses local gravity. Up to now you've had momentum, other people, or ship struts to use so that you don't get stuck drifting forever like Marcus there and crashing hard to the ground when and if people smarter than you get the gravity working again. This time, you've got none of those. What's the procedure?"
"Assess! Orient! Act!" the class choruses dutifully.

"Marcus. Assess!"
"The gravity has failed. I've somehow lost any momentum I might have had and am not moving at any appreciable speed towards anything I can use to secure myself."
"The nearest handhold is approximately eight metres away, subjectively above me. It appears to be secure, and nothing potentially dangerous is moving towards me, it, or the path between us."
"Act, then."
She thinks for a moment more.
"What is it, Marcus?"
"I apologize, I forgot to assess two important aspects. I take it there's nobody around who can share some momentum with me?"
"That's correct."
"In this scenario, is there atmosphere, or am I hypothetically in a pressure-suit, in a vacuum?"
She could swear she sees him smiling. "You're in an atmosphere, but dressed in a pressure-suit in case of potential hull breach."

Perfect. She reaches into one of her jumpsuit's pockets and removes the tin of compressed air she'd picked up earlier to clean some electronics at her workstation. She angles the nozzle downward towards her feet and expels nearly all of the air, keeping some back in case she needs to adjust her course at all. It's not a lot, so she only drifts slowly, but it's enough to impart a vector, and she can tell she'll be within arm's reach of her intended handhold within ten minutes.

"What," cuts her instructor's voice, "is that?"

"Every Starfleet pressure-suit is equipped with canisters of compressed air, sir. Usually a bit bigger than this one, but it's what I've got. You implied that I was in immediate danger from a potential fall, and I thought avoiding that was worth spending five minutes' worth of suit pressure."

This time she's certain he's smiling.

"We usually have to go through a few cadets before someone figures it out. What was your thought process, Marcus?"

She thinks of the hills above San Francisco and discarded drink bottles, and wonders if she can paint the air canisters on her pressure suit purple without violating regs.

"Given a little pressure, sir... anything can be a rocket. Even a slow one."

He nods, and deploys the poles again. He calls the next cadet while she floats, slowly, towards the certain handhold.

NOTE: With thanks to Measured_Words for giving part of it a once-over - any mistakes or nonsensical bits are entirely mine. This is dedicated to igrockspock for being responsible for a lot of stories about amazing Starfleet ladies, either directly or as instigator and temptress.