Let me say one thing very loudly and very clearly right now: sci-fi does not have to be scientifically accurate to be good. This is one of the profound truths upon which my view of the universe is built. All fiction relies on suspension of disbelief to a certain degree, and there are no rules about how far that suspension of disbelief should or should not be allowed to stretch. Do not let anyone tell you otherwise.

But! We’re not here today to extol the virtues of boundless creativity. Today, we’re here to nitpick.

Several of my friends have said that I am the world’s most annoying person to watch movies with, because of the joy I find in picking apart every scrap of scientific detail. I have to physically restrain myself sometimes from pausing the movie to point out scientific inaccuracies — not because I look down on the writers for including them, but because I think it’s fun to speculate about how things would actually work in real life. I tend to do the same thing in reverse with my own writing. My academic and career background is in aerospace engineering, and I vividly remember sitting in some class — I think it was orbital mechanics — and thinking, Oh, yeah, this is great; I can definitely use this in a book.

Now, here’s the thing: as annoying as this is to me and everyone around me, I can’t imagine I am anywhere near the only person who’s like this. So if you have a commitment to scientific accuracy bordering on unhealthy obsession, but don’t feel like sacrificing time, money, and sanity for an engineering degree, today is your lucky day. We’re going to talk about some key points for writing sci-fi that feels more scientifically accurate (as well as a couple of my personal favorite bones to pick).

1. Keep the noise down

How do sound & explosions work in space? For sound, the answer to this question is simple: it doesn’t. Sound is the result of pressure waves moving through a medium and eventually colliding with an eardrum, making it vibrate at the same frequency as the wave. Without a medium (like air or water) to move through, it can’t exist: period. I’m very sorry, but no amount of scientific innovation is ever going to change this. It’s a basic fact of physics.

Explosions pose a related problem, because the lack of a medium does mean they work a little differently than our earthly intuitions would lead us to believe… but they can still happen. There’s just a few main things to keep in mind:

• There will be no sound. As mentioned, sound has to travel through something, and we’re in a vacuum.
• There will be no shockwave. Shockwaves are like sound in that they need a medium to travel through.
• Debris will be deadlier. In a planet-bound explosion, debris thrown away from an explosion will be slowed by air resistance, pulled down to earth by gravity, and eventually stopped by the ground. Take away these things, and that crap is just gonna keep on flying. Like my boy Newton said, an object in motion stays in motion. So until that debris hits something that stops or redirects it, it will keep traveling with the same initial velocity imparted to it by the explosion. That’s very fast, my friends. So if you’re looking for the destruction and devastation of being hit by the shockwave of an explosion, consider having a chunk of something big and gnarly smash into your protagonists’ ship at several thousand miles an hour. It’ll be more realistic, and suck just as much.
• The explosion will usually produce a spherical cloud. The fun little puffs and tendrils you see in clouds on earth are caused by aerodynamic forces that do not exist in a vacuum. Unless something else is somehow directing the force of the blast or imparting a force on the cloud, the exploding stuff will expand outward in every direction at an equal rate.

2. Have more than one thing go wrong

How do things go wrong in space? Well, usually, a little at a time, over the course of many years.

Engineers purposefully build redundancies into every part of our designs, as well as every stage in the design’s life cycle, from structural blueprints to operational checklists. We sit around all day thinking of every possible thing that could go wrong, and then we design with those things in mind. The consequence of this is that very rarely (not never, but rarely) is an engineering disaster brought on by a single, central cause.

What’s much more common is a string of smaller failures in different, unrelated areas that work together to create a catastrophe. While any one of these failures on its own might not be enough to bring down the whole system, but in concert, they prove to be too much.

Let’s peruse a few examples of major engineering disasters you’re probably at least a little familiar with, and look at the types of problems that, together, resulted in catastrophe. None of these summaries are intended to be exhaustive — I’m just trying to give a flavor of some of the broad categories of things that went wrong.

• The Titanic: operator error (recklessness, ego), sketchy operating conditions, a failsafe mechanism which did not cover all possible failures (namely, a long gash in the hull), the material properties of the hull (the steel they used was really, really brittle at low temperatures), and of course, not enough lifeboats.
• Apollo 13: design and procedural flaws (too much voltage was connected to wires located inside the oxygen tank, which had their insulation badly damaged as a result), manufacturing/installation mistakes (one of the oxygen tanks was moved over from the Apollo 10 spacecraft and was dropped during the move, causing damage that went unnoticed at the time), and the many and varied systemic consequences of a major explosion.
• The Chernobyl Nuclear Power Plant explosion: bad test procedures (they had steps crossed out, which the engineers were told to follow anyway), unsuitable test conditions (the power was held at too low a level, causing xenon to build up in the core), an inadequately prepared test crew, design flaws (the emergency stop button caused a momentary power spike when pressed), and a big ol’ government coverup.

If your story relies on a space disaster, you can make it not only more credible but far more interesting if you have it come from more than one source. Write out an explanation of your disaster and try to work in phrases like “which would have been okay if not for _____,” and “which, combined with the effects of _____…”

Also, notice how many of these cases involve human error (that is to say, all of them). Notice the kind of human error it is: overconfidence, recklessness, pride, prioritization of budget or schedule above safety, and not stopping to evaluate the potential consequences of what, at the time, probably seemed like a small mistake. If you think you’ve got the perfect sci-fi disaster all engineered, sprinkling in a tight budget, a tight schedule, and a dash of reckless disregard for safety never hurts.

3. Make your spaceship more aerodynamic

“But my spaceship is in SPACE! You JUST SAID there’s no air in space!” True, but there is a whole heck of a lot of the stuff between us and space. And in order to go from here to there, you have to go through all of it, and go through it really freakin’ fast. So your spaceship actually has to be really, really aerodynamic. That means it needs to be streamlined and smooth, as well as have adequate stabilizing surfaces and perfect balance. Sharp corners, angular shapes, things jutting out into the airflow, and the like are all generally no-gos for spacecraft design. Rocket fuel is expensive as heck, and the less aerodynamically efficient your ship is, the more fuel it’s going to waste trying to fight its way up through the atmosphere.

Now, if your ship is assembled, docked, and loaded in space, with passengers and cargo reaching the dock by means of a short-range transit ship or a space elevator or something, you can let this one slide a little. (The International Space Station was assembled in space, which is why it’s allowed to look like that.) But in some cases, you might want to make it aerodynamic anyway in case it ever needs to do an emergency landing on a planet.

4. Wade into the controversy of touch screens in space

Touch screens are a contentious issue in the aerospace community. Personally, I come down pretty firmly on the side of not liking them. Does that mean you shouldn’t put them in your fictional spaceship? Nah, go for it. But first, hear me out, and understand why you might be putting your characters in a sticky situation.

We’ve been using big, clunky buttons in stuff that flies for a very long time, and for very good reason. With a button, toggle, or dial, you can see what position the switch is in at all times, even if you lose power (you can even feel it without necessarily looking — useful if you’ve got your eyes glued to your instruments during a tense moment). Touchscreens are also hard to use in turbulence, and pose a greater risk if you accidentally bump into them or brush against them while moving around the flight deck. There’s also a lot to be said for the tactile feedback you get when pushing a button or turning a knob. Haptic feedback can, of course, be engineered into a touch screen, but it’s cheaper and easier to achieve with a physical switch.

These are all things you’ll have to weigh when deciding what the controls look like in your fictional spaceship. In addition to all this stuff, this posting featuring responses by several pilots has a really good rundown of the various advantages and disadvantages of touchscreens in aircraft that may help you decide.

And yes, I know, the SpaceX Dragon capsule has touchscreens. There are lots of engineers out there who are plenty worried about that. Luckily, the Dragon also has physical buttons for functions you can’t afford to lose in the event of an emergency.

Also, the buttons on aircraft and spacecraft are incredibly satisfying to press. I just have to throw that out there. Not necessarily a strong argument in their favor, but an argument I feel bound to present nonetheless.

5. Let’s talk about units of speed

When things start to go fast — like, slightly below the speed of sound — we start using different units that more accurately reflect the physics going on at those speeds.

Within the atmosphere, you’ll start hearing Mach number thrown around once you get up to the speeds of, say, a commercial jet. Mach number is defined as your airspeed divided by the speed of sound. The important thing to know here is that the speed of sound is not a constant — it actually changes based on temperature (and thus altitude) and what medium you’re moving through. So Mach 1 corresponds to a different airspeed at sea level than it does at 10,000 feet. It’s also not the same on, say, Earth and Mars, not only because of the difference in temperature, but because of the different chemical composition of the atmosphere.

We use Mach number because at high speeds, the physical phenomena that limit the performance of the aircraft (like shockwave behavior, and temperature and pressure variations, to name just a couple) are highly dependent on the speed of sound. This means that the equations for all of these things are written in terms of — you guessed it — Mach number.

Now, as we’ve discussed, there’s no sound in space, so trying to define things in terms of Mach number would be both impossible and meaningless. Instead, in spaceflight we tend to use something like kilometers per second. You have to go so ridiculously fast to escape Earth’s gravity that by the time you’re out there, measuring in units of distance per hour or even distance per minute would give you annoyingly high numbers, and who wants to deal with all those digits?

If you’re writing about long-distance or faster than light space travel, in addition to the light year (defined as the distance a photon travels in one year) you might also want to familiarize yourself with the AU (astronomical unit — the mean distance from Earth to the Sun) and the parsec (a measurement derived from the orbital geometry of Earth, which comes out to be about 3.26 light years). These units are found today in astronomy.

Or, come up with your own units! The ancients did not use the same units of measure we use today, and I think it’s a safe bet that in the far future, we will have moved on to a better system as well.

In closing: don’t worry about any of this

Do you have the perfect scene already written where your perfectly cube-shaped, touchscreen-laden spaceship, doomed and drifting aimlessly through the vacuum of space at two hundred million feet per hour, explodes with a thundering kaboom thanks to one tiny flaw? You know what — I’d read it. I’d read it, and I’d probably love it.

Like I said, sci-fi does not need to be scientifically accurate to be good. Not all fiction is meant to reflect real life. These tips and pointers are not meant in any way to be some kind of be-all, end-all ruleset for writing about things that fly. They are intended to provide some guidance and inspiration to writers in the particular subgenre known as hard sci-fi, where writers focus a lot of energy on making the science as plausible as possible. And it is not better or worse than hand-wavy soft sci-fi, despite what a lot of angry people on the internet who like to argue about these things will tell you. If it’s your thing, I hope this was helpful, and if it’s not, I hope it was at least interesting. And either way, go forth now and write whatever the heck you want.

Happy writing.