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Writing hard science fiction set [[Tropes in Space|in space]] carries with it all of the baggage of writing any other genre of literature. Your characters must be believable, your plots and descriptions must not be boring, the story must be ''satisfying'' to the reader in some way, etc.. Every piece of advice in the [[So You Want To/Write a Story|Write a Story]] article is just as sound when writing hard SF as it is when writing a western, a modern romance, a historical naval drama, or any other literary genre you can imagine.
However, to work as a piece of hard SF with space travel, the writer must go one big step farther: The technology, the mechanics of space travel, the planets, the aliens (if there ''are'' aliens), all the details of that futuristic setting ''must be [[Realism|realistic]].''
Since space travel is involved, it's important to remember that human beings have
One of the best resources out there for realistic future space travel is the [http://www.projectrho.com/rocket/ Atomic Rockets page], which covers everything from "what designs are on the drawing board for spacecraft capable of crossing interstellar distances within a human lifetime?" to "why should my female crew members not wear skirts?"
== Outline of Artistic Disappointments and Non-recommended Tropes ==
Sadly, the rules of realistically writing
Firstly, there is [[Bad Writing]]. There are artistic, [[Doylist]] reasons why you'd want to do this, such as inexperience, not reading Allthetropes, a search for reliable, but still bad tropes out of fear of being fired from a writing job (eg. TV and movies are too expensive to treat failure as an option), being underpaid, having an [[Anvilicious]] object lesson to deliver, hating one's boss, other projects and rarely, simple laziness. Treat failure as an option, but never be satisfied with failure nor mediocrity. As a writer in hard SF, you must fully intend to succeed with flying colors, even if you have to take the risk of failure. Because you're dealing with an audience smart enough to have the basic understanding of consistency, accuracy, and natural science required to care about and more-or-less know where a work fits into the [[Mohs Scale of Science Fiction Hardness]], and you're dealing with impersonal forces that can easily take decades or centuries that are not easily [[Time Skip]]ped, such as sub-light interstellar travel, technological and social innovation and the rise and fall of civilizations, you often must write an epic. [[Mood Whiplash| You can't get away with writing a cartoon]]. Hard SF audiences are intelligent and have access to works of other genres and literary award winning works of hard SF, of which there are many, so they won't stick around for [[So Okay It's Average| mediocrity]], which bores them, nor [[So Bad It's Horrible| failure]], because hard SF audiences look forward to reading literary award winning works of hard SF.
Secondly, here is a list of tropes that are generally considered [[Bad Writing]] in a realistic universe, along with some works or franchises that successfully implement some of them and are still considered to be hard SF:
* [[All Planets Are Earthlike]] (at least without [[Terraforming]]). Example: [[Red Mars Trilogy| Green Mars and Blue Mars]] by Kim Stanley Robinson implement this in Mars' case by terraforming Mars.
* [[Inertial Dampening]]. Example: Orion's Arm implements this in the Halo Drive and the rumored Void Drive. The Halo Drive implements this by nacelles that use gravito-magnetism to harness the fuel/engines proper into the main hull of the ship, so everything and everyone in the main hull is accelerated equally, thus making nothing there feel the acceleration. The Void Drive would implement this by having the entire ship inside a space-time metric.
* [[Reactionless Drive]] (at least until the [[w:RF resonant cavity thruster|RF resonant cavity thruster]], aka the EmDrive, is confirmed, if ever) Example: Orion's Arm, written collaboratively, implements this by making the space-time metric really small instead of metrics large enough to surround the ship without making the metric a lot [[Bigger on the Inside]], apparently because making metrics that are large on the outside is too difficult.
* [[Single Biome Planet]]
* [[Space Is an Ocean]]
* [[Space Pirates]]. Example: Corsair by James L. Cambias (''not'' [[Corsair| Minami Fuuko]]) implements this by making the ships into crew-less robots that are run and computer hacked from offices on the Eastern seaboard of the United States. The piracy has a sort of maritime aspect also.
* [[Stealth in Space]] (and most of the other
* [[Teleporters and Transporters]]. Example: Orion's Arm implements this with rental bodies, which are bodies that one uses by [[Brain Uploading]] and engenerators, which [[Me's a Crowd| copy people]].
* [[Green-Skinned Space Babe]] (and [[Rubber Forehead Aliens]] in general)
* [[Faster-Than-Light Travel]] / [[Time Travel]]. Example: The [[Xeelee Sequence]] by Stephen Baxter implements this with [[Sufficiently Advanced Technology]].
* [[Techno Babble]]. Example: Orion's Arm implements this with such phrases as "hyperdenebola collapse" to refer to the de-assimilation that tends to happen when a colony's communications with [[The Assimilator| the Amalgamation]] are cut off. According to Wikipedia, Denebola is Beta Leonis, a star in constellation Leo about 43 light-years from Earth. What this star has to do with "hyper", "collapse", and the Amalgamation is not actually obvious.
* [[Cliche]]s, especially [[The Grand List of Overused Science Fiction Cliches| science fiction cliches]]. Even if these are technically possible in a hard-SF setting - which is itself by no means whatsoever guaranteed - then they still tend to be unrealistically common in science fiction, and it is common for them to be unrealistically portrayed. And as detailed above, hard SF audiences tend to be intelligent. So no cliches.
* [[Did_Not_Do_the_Research| Inaccuracies]] that aren't, strictly speaking, about math, natural sciences, microeconomics or futurology, liberties that are not painstakingly [[Deconstructed]] or [[Reconstructed]] or [[Rule of Index| are revealed to be just too implausible by their deconstruction or reconstruction]], and [[Acceptable Breaks From Reality| breaks from reality without regard to how acceptable they are in other genres]]. Inaccuracies that are not about these topics are liable to be confused with inaccuracies that are about these topics, and hard SF is all about [[Consistency]] and [[Shown Their Work| accuracy]], so even if inaccuracies are not confused topic-wise, inaccuracies are still kind of wrong for hard SF.
There are sound reasons why all of the above tropes will probably not work in [[Real Life]].
==== Doing the Research ====▼
▲==== Doing the Research ====
You wouldn't set a story in the Sahara Desert and have your hero go swimming in one of the "numerous lakes" there. You wouldn't set a car chase in downtown Florence, Italy and then make up the street names and city layout. Similarly, don't set your story on Mars and have your hero swelter in the unbearable heat<ref>I'm looking at ''you'', [[Babylon 5]] novel #1 "Voices" by John Vornholt!</ref>, or put an Earthlike planet in orbit around Alpha Centauri without at least mentioning the bright "B" star that should be visible from time to time in the sky. Making up details about places we ''don't'' have strong data about is
In other words
==
If doing an arithmetic problem like "A train leaves Chicago at 8 AM going 60 miles per hour" taxes the limits of your skills, putting realistic space travel into your story is probably not for you. Space travel is ''all about'' doing the math, and the math can get hairy -- especially when dealing with speeds above 5-10% of the speed of light, where special relativity starts to rear its ugly head. But if you're up for the challenge, it's definitely worth doing. Even if you don't show your work to your readers, getting the numbers right (or nearly right) will go a long way toward your story's sense of realism.
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* Controlled nuclear fusion engines
* [[Ramscoop|Ramscoops]]
With the exception of ion engines, all of these are mere drawing-board designs at present, and all of them have practical problems. NERVA engines
But even if controlled nuclear fusion ''does'' become a reality (allowing what [[Robert Heinlein]] called a [http://www.projectrho.com/rocket/torchships.php torch]), that still won't eliminate the need for big rockets if you want to get anywhere in a reasonable amount of time. Sure, your exhaust velocity might now be on the order of (say) 2% of light speed, but the rocket equation still applies. If you want to accelerate at 1''g'' to the half-way point between Earth and Saturn, then decelerate at 1''g'' for the rest of the trip, your total delta-v budget will be about 2% of light speed -- the same as your own exhaust velocity. You'd ''still'' need a mass ratio of ''e'', meaning your spacecraft's
==
We humans evolved on, and (so far) all grew up on, Earth. We instinctively expect the air to be
The sad fact is, though, that no other planet we've detected thus far is even remotely habitable by human standards. The bigger ones are Jupiter-like balls of gas, while the smaller ones are almost universally airless. The few worlds we've found that ''do'' have both an atmosphere and a solid surface have been blanketed in gases that no human can breathe, at pressures anywhere from [[Mars (useful notes)|near-vacuum]] to [[Venus|90 times Earth's sea level]]. While it's theoretically ''possible'' that a planet out there might harbor life as we know it, it would have to fit a long, narrow list of parameters, and even then, the kind of life that might have actually evolved there will most likely be very different from the
In order for a planet to be able to support life as we know it on its surface ''at all'', it will have to lie in a very narrow range of distances from its parent star. Too close, and any water would evaporate. Too far, and any water would freeze. Liquid water -- and life as we know it requires liquid water -- can only exist if the planet lies within that narrow zone where it's receiving just the right amount of energy from its star for the surface temperature to allow it. This is called the star's "comfort zone," or "Goldilocks Zone" (as in: not too close, not too far, but
How far away from the star the Goldilocks zone is depends on the star's energy output. A very dim red dwarf star, like Wolf 359, would require a planet to be only about 1.5 million kilometers away from it to receive as much energy as Earth does from our sun -- that's only 0.01 A.U., 1% of the Earth-sun distance. A bright and powerful star like Sirius A, on the other hand, would require a planet to be 5 A.U. away from it to receive as much energy as the Earth does from the sun.
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... which is, in fact, how fast things accelerate downward near the surface of the Earth when you drop them. Mars, by contrast, only has a radius of 3,380,000 meters and an average density of 3930 kg/m<sup>3</sup>, so its surface gravity is only 3.71 m/s<sup>2</sup>, about 38% of Earth's.
You'll note that the Martian atmosphere is extremely thin, less than 1% of the surface pressure of Earth's atmosphere. One factor that
Another factor that can mean no life-bearing planets are possible in a given star system is the lack of heavy elements. The Milky Way galaxy is over ten billion years old. When it first formed, it consisted almost entirely of hydrogen and helium; almost no heavier elements (like carbon and the other elements necessary for organic life) existed. Several generations of stars have been born and died since then, and some of the more spectacular star deaths have peppered the interstellar medium with heavy elements synthesized by those stars' death throes. The sun, for instance, is a third-generation star -- the cloud of gas and dust out of which it formed contained material expelled by a supernova which, in turn, had formed out of an earlier cloud that contained material from an even earlier supernova. This is why there was enough carbon, oxygen, silicon, iron, etc. to form solid, rocky planets and organic molecules. Astrophysicists refer to all elements heavier than helium as "metals" (even if the element in question is oxygen or neon), and sometimes call a star system's heavy element abundance its "metallicity."
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Oh ... and if your planet has any moons, don't forget to use our old formula P<sup>2</sup>M = A<sup>3</sup> to calculate how long their orbital periods are!
==
Two separate "So You Want To" articles now exist to deal with the realism aspects of creating your own aliens. They are:
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== Deviation: Limiting the Damage ==
Let's say the idea of a spaceship carying 10 times its empty weight in fuel sickens you. You want the space aboard your space ship to house your colorful characters, dazzling weapons,
But hold on. You've also opened up a can of worms.
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First, if you allow them to accelerate without pushing anything, they are now violating one of the most basic laws known to physics: the ''conservation of momentum''. In the real world, you can't apply a force to an object in one direction without causing an equal-and-opposite force on some other object. Rockets fly up because their exhaust flies down. Jumping up pushes the Earth ever-so-slightly downward; falling back to the ground afterward pulls the Earth ever-so-slightly up. By letting your space ship violate this basic law, you're saying that momentum ''is not always conserved.'' What other circumstances in your universe will cause momentum not to be conserved? Do the laws of Newton simply get held in abeyance every time someone switches on a gravity generator? Are there natural phenomena that accomplish the same thing?
Second, are you also [[No Conservation of Energy|violating the conservation of energy]]? A 1000 tonne spaceship traveling 1/10 of the speed of light has a kinetic energy of 450 quintillion Joules, equal to 100,000 megatons of TNT. That energy had to come from somewhere. Did it come from burning some sort of fuel on board your space ship, to power the generators? If you used the thermonuclear fusion of hydrogen into helium as your fuel source, and you managed to [[Hand Wave]] a fusion reactor technology that's nearly 100% efficient, you'd have to burn at least 350 tonnes of hydrogen to obtain that much energy, which is a third of your spaceship's own mass. (This isn't as bad a mass-ratio situation as if you'd used a plain-old momentum-conserving fusion rocket, but it's still pretty significant.) And you'll have to burn just as much again to slow your space ship back down at the end of your trip. If this is too much for you, and you decide your
Third, if any 1000 tonne space ship can easily accelerate to a tenth of light speed, then every two-bit spaceship owner has in his possession a weapon of mass destruction. Those 100,000 megatons of TNT-equivalent kinetic energy will act like 100,000 megatons of ''actual'' TNT if they strike a planet. Want a future populated by plucky tramp space-freighters and sneaky space pirates? It ain't gonna happen if every ship is a Hiroshima-on-steroids waiting to happen. Every spacecraft captain will be on too short a leash. Any spacecraft that even ''looks'' suspicious will be killed before it can become a threat. (And, yes, ''all'' fast-moving spacecraft, and even stationary spacecraft, will eventually be detected -- there ain't no [[Stealth in Space]].) Any civilization that didn't take these precautions wouldn't ''be'' a civilization for very long. This might work as a setting for your future totalitarian dystopia, but is hardly the right world for romantic swashbuckling adventures.
The potential damage done to your story by a [[Reactionless Drive]] is just one example of the broader principle. ''Any'' technological marvel that sidesteps the [[Real Life]] roadblocks facing space travel has the potential for unintended consequences. Thermonuclear [http://www.projectrho.com/rocket/torchships.php torchships]? They've got the same "spaceship = weapon of mass destruction" problem that
So what do you do when you ''need'' your characters to be able to move between the stars faster-than-light, or [[Transporters and Teleporters|teleport]], or have a [[Tractor Beam]], or do any of the other myriad things that our current best guesses at the law of nature say are impossible? You set the technology up in such a way as to '''limit the damage''' to your story and your setting. Maybe your [[Deflector Shields]] are magnetic, and can only affect charged particles and ferromagnetic metals -- and your spaceship needs to open up holes in its shields to shoot iron slugs or particle beams at an enemy. Maybe the high speeds needed to traverse interplanetary distances in days or hours are imparted not by your space freighter's own engines, but by
== [[Faster-Than-Light Travel]] ==
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[[FTL Travel]] is one of the bigger thorns in the side of the Hard SF genre. Special Relativity makes it absolutely clear: it is physically impossible to accelerate an object with any kind of mass so that it's moving faster than the speed of light. Even accelerating an object ''to'' the speed of light would require an infinite amount of energy. However, we've also pretty much established that there are no other technological species on any planet in the Solar system other than Earth. If we want to have space adventures involving high-tech aliens, we'll have to travel to other star systems, and the distances involved are so enormous that it would take years to get from one star to another if you were limited to sub-light speeds. Science Fiction writers have had to compromise, and allow ''some'' means of travelling faster-than-light which didn't turn their universe into something totally unrecognizable to a modern reader. Therefore, the ability to move faster-than-light has received more attention in SF than any other fantastic concept as to ways to limit the damage of having it around.
The very worst problem with FTL travel (or even just [[FTL Radio]]) is a certain extremely strange consequence of [[Time Dilation]]. When travelling at any speed, even a brisk walk, relative to somebody else, you'll see his clock move slower than yours -- but he'll see ''your'' clock move slower than ''his''. This extremely counter-intuitive state of affairs means that some distant events in the universe which are in your future are in the other guy's past, and vice-versa. Without FTL travel, though, this isn't a problem. Einstein and Minkowsky established that for any event that's in
Here's an example: Suppose Observer A is standing on Earth, and Observer B is in a space ship, coasting in a straight line at 86.60254% of the speed of light. This gives him a gamma (γ) factor of exactly 2. When the space ship passes by Earth, both
But by going faster than light, even just [[FTL Radio]], you ''can'' receive information about events that are in your own future. You can perceive Event 2, which was caused by Event 1, before Event 1 actually occurs in your reference frame. In our lottery-winning scenario above, suppose Observer A and Observer B had a [[Subspace Ansible]] that allowed instant communication no matter how far apart they were. Observer A could send the winning lottery numbers to Observer B's space ship at 6:20 PM on
[[Translation: "Yes"|In other words]], '''[[Time Travel]]'''. This is the part where unless you're literally the winner of a hard-SF literary award, you have to be reminded that you're not even figuratively the winner of a hard-SF literary award. Writing a story in which time travel is even possible is definitely not recommended for those of you that haven't won a hard-SF literary award.
How do veteran SF writers handle the time travel consequences of FTL travel? Most of them don't. They simply [[Hand Wave|sweep it under the rug]] and hope no one will notice. Those authors who do address it often end up with bizarre universes where wars are fought before they've even started, and characters can [[Grandfather Paradox|shoot their own grandfathers]].
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