The Battle Of Hoth Unlimited, Part One

This article started out as a comparison of how different scifi properties portray tactical combat. To spice things up, I decided to pattern this article after a lively forum board debate I read through years ago, by placing said troops into an actual battle scenario from science fiction and see how they would do. For this, I’ve chosen the Battle of Hoth, one of the most famous ground engagements in on-screen science fiction, from The Empire Strikes Back.

The militaries from various sources will be replacing the rebels defending the base, and we’ll see how each will handle the Imperial ground assault. Remember this is my opinion only, and is purely for fun.

THE SCENARIO

The Empire has discovered a major Rebel base on Hoth, a world gripped in a severe ice age and completely covered over in glaciers and snow. The Imperial Fleet arrives in orbit, and the Rebels activate a large shield over the base that prevents orbital bombardment or direct landing of troops. So the Imperials send in a mechanized division outside the field radius to take out the field generator through an old-fashioned ground assault. Their primary objective is to capture and/or destroy the base’s main generators powering the shield, at the center of Rebel-defended territory.

The Rebels attempt to evacuate base, piling everyone they can into ships to run the Imperial blockade in high orbit. While the base is being evacuated, a number of stalwart rebels fight a holding action against the oncoming Imperial troops to give their fellows time to escape.

Because of the overhead shield, neither side can employ any type of high-altitude attack craft or weapon. Like in the movie, the defenders have to hold out as long as they can.

This battle was actually much larger than what was portrayed on screen. The film narrowly followed only the parts of it Luke and the other principles were involved in, but the battle actually involved thousands of troops and the siege taking place on various fronts simultaneously.

VICTORY CONDITIONS:

Rebel Decisive Win: All the transports get away safely, and the Imperials never take the base.

Rebel Marginal Win: All of the transports get away safely, but the Imperials take the base (this was the result in the movie.)

Imperial Marginal Win: The Imperials take the base quickly enough that a good percentage of the transports never make it away.

Imperial Decisive Win: Imperials take the base with hardly any resistance and intercept most of the transports before they leave planet.

THE RULES

Basically, as we switch out the Rebels for various other sci-fi troops, these soldiers will be given any equipment and weapons from their source material that approximate the role of equipment the rebels had. For example, the rebels defending the base had 9 speeders, so the new troops will also have 9 low-altitude attack craft their forces would typically employ, or the closest equivalent they have in their source material. They will also be employed in roughly the same numbers the rebels were.

Also, like the rebels, the new troops will also be well versed in winter warfare tactics and can take advantage of the environment just as well.

A NOTE ON PLOT-INDUCED STUPIDITY

For this scenario, we are jettisoning what’s called Plot-Induced Stupidity (PIS.) A term that’s become popular with fans of various stripes online, PIS is when characters act outrightly idiotic against common logic, or when events in the story take a badly contrived turn, in order to move the plot along. Some rather famous examples include elite Imperial Stormtroopers in Return of the Jedi being routed by stone-age teddy bears, or some convenient glitch in Star Trek that prevents the crew from using their transporter at a critical moment.

So for this article, PIS is dispensed with across the board for attackers and defenders both. All equipment will work the way it is supposed to, and all troopers involved on both sides will act competently and use smart tactics wherever appropriate.

THE IMPERIAL FORCES

First, let’s take a look at the attacking force.

The Imperials are at about Tech Level 18, meaning they’re a fairly typical space-opera civilization technologically. They do not always employ equipment that takes full advantage of their society’s technical sophistication (why employ clumsy walker units when they have extremely versatile anti-grav technology?), but what they lack in sophistication they usually make up for in ruthlessness and sheer numbers. The Imperials’ favored military tactic usually involves head-on confrontation with overwhelming force. Subtleties and scheming is usually left to the Sith overlords and their pet generals.

In this scenario, they are employing (at least according to the Wikipedia article on the Battle for Hoth) 9 AT-AT walkers, various smaller walker units (AT-ST units,) and a division of Stormtroopers specifically trained and outfitted for winter conditions. Total Imperial ground troop strength is around 12,000 personnel. Other types of combat walkers are mentioned in EU sources, but they’ll be left off here. We don’t want to confuse casual readers too much, so we’re just going to stick mostly to the types of units seen onscreen in the movie. The walker units advance ahead of the main bodies of foot soldiers, in order to use their superior armor and weapons to smash through the gathered Rebel defenses. Of course, the AT-ATs are carrying a fair number of troops as well.

The Stormtroopers have full-body armor designed to be impact resistant and thermally insulated. The helmets have a full radio suite and a heads-up display with several limited sensor capabilities, such as infrared. The armor, however, does limit movement somewhat, and the helmets severely limit real world vision. This means that if the HUD goes down, the trooper will only have a narrow field of vision unless he removes his helmet.

Their primary weapons are “blasters,” which seem to be low-velocity plasma weapons; basically the weapons superheat a compressed volume of gas into a plasma state then release it as a magnetically-focused bolt. Despite doing potentially impressive heat damage, the Imperial versions seem to travel at low speeds (equivalent to a baseball fastball pitch) and have limited penetration capabilities. On the plus side, though, they are very long-enduring (we never see a Stormtrooper who has to stop to reload), have good effective ranges, and are very rugged.

The Imperial armies do seem to have a troop quality issue that goes beyond the keystone-kop-like PIS we see sometimes. Many don’t seem well motivated or well trained, at least compared to many modern real-world militaries. The Imperials, at least in the movies, depend less on elite, skilled soldiers and much more on raw numbers. The troopers that were involved on Hoth seemed better than most seen throughout the series, but general troop quality is still something that must be taken into consideration.

The quality of the commanding officers (excluding Vader and a few others) seems to be exceptionally dismal. They’re usually portrayed as barely competent and haughty, basically over-promoted bureaucrats more interested in sucking up to their superiors than in actually getting their jobs done right.

And there’s no getting around the most glaring problem with the Imperial forces in this scenario: the AT-AT walkers. They are one of the most impractically designed ground military vehicles ever put on screen. They’re basically slow moving, top-heavy, walking targets. Though they do look very neat (which is probably all the film makers were primarily concerned about) in most ‘realistic’ engagements they’d be more a liability than an asset.

The good is that they’re very heavily armored; Luke even states they’re blaster-proof. The bad--the very bad--is that this chassis is balanced high atop of four very tall, very vulnerable legs. If the vehicle falls, it can’t right itself, and it also seems like heavily uneven terrain could seriously stymie it. Still, the AT-ATs also carry some impressive firepower in the form of forward-mounted heavy blasters. In fact, if the AT-ATs can somehow make it to the defensive perimeter, their heavy firepower is usually assured to bring down any defenses there.

The AT-STs are much better suited for this kind of fight. Though they are also a bit top-heavy for their size, they make up for it by being speedy and maneuverable. Though they seemed underused in the movie, in truth they would be highly effective in hit and run tactics and in infantry-support roles. In a more realistic scenario, they, not the AT-ATs, would prove to be the key weapon system that would allow the Imperials to capture the base.

In summary, the Imperials represent a formidable invasion force, though they do have some weaknesses foes may be able to take advantage of.

THE DEFENDERS

In the movie, the base is defended by about 2000 rebel infantry (making them outnumbered by about six to one). Besides the aforementioned nine attack speeders, they also had various hard point defense turrets at strategic locations and minor vehicles and mounts (tauntauns) to move troops and supplies around. The various new defenders will be given their source-material tactical equivalents of these.

In the movie, the rebels suffered devastating losses; well over a thousand defenders were killed and just as many captured or MIA. We’ll see who can do better, and who can do worse. As per OV tradition, we’ll take the defending forces from lowest tech and work our way up you the highest tech troops.

XENOMORPHS

Source: The Aliens movies

Tech Level: 0

The xenomorphs have no technology per se, so its basically just them naked against the invaders, about two thousand strong, positioned in clusters throughout the base, with a Queen and two dozen eggs/facehuggers for every 200 drones or so.

At first, out in the open, the Imperials do very well. With their far superior numbers and firepower, they have no trouble picking off any groups of drones sent out to attack them. The Imperials will have little trouble reaching the base proper or getting to the power generators.

But, as anyone who’s ever seen the Aliens movies can guess, once they actually begin moving into the base itself is when the horror show really begins.

The aliens are very good at stealth, hiding in relatively small spaces, and executing hit-and run ambush tactics. Plus they do not show up on infrared scans. The stormtroopers will be seriously stymied at first, but will likely adjust their tactics once they discover what they’re up against. They do have the advantage of numbers, plus their armor provides them with at least some protection from the xenomorphs’ violent physical attacks and acid blood. Sweeping through the base slowly but cautiously in large groups, they’re likely to take horrific losses, but will eventually make their way through to the field generator.

RESULTS: Imperial Decisive Victory. The Imperials will eventually capture the base, but in the process will lose at least several hundred troops, much more than against the original Rebels. The increased amount of time the Imperials spend capturing the base itself is made up for in a far more speedier traversing of ground from their drop points, allowing them to blow the generators much earlier than in the movie and intercept many rebel transports.


THE ZERG

Source: Starcraft

Tech Level: 0

Purely biological, the Zerg have no technology per se.

As we made a point of jettisoning PIS, we’ll also do the same in this case with GIS—Game Induced Stupidity. Some odd, and even non-sensical, abstractions were necessary in the Starcraft game in order to make the product playable and fun. Soldiers with rifles shooting down battleship-sized starships, producing entire armies with blue crystals and green gas, hatching tank-sized critters in under five minutes, and so on. The games’ narrative, visuals, and cut scenes will be used for a more ‘realistic’ version of the Zerg we’ll use here.

Because of the overhead shield, the Zerg will likely not bother with many air units, excepting Overlords. Instead, the Cerebrate in charge of defense will produce huge amounts of Zerlings and Hydralisks, along with nine Ultralisks to equal the Rebels’ snowspeeders. Point defenses around and within the base will be Sunken Colonies or burrowed Defilers.

Like the Imperials, the Zerg’s favorite tactic is a frontal assault with overwhelming numbers. And that’s exactly what they’ll do; organize three direct assaults on the three AT-AT groups to take down what they see as the most obvious threat right away. Each assault group would likely consist of one hundred to several hundred zerglings and hydralisks to assist three ultralisks.

The problem for the Imperials here is that individual Zerg are much tougher physically than any rebel or even xenomorph. As seen in cut scenes in the game, even the zerglings, the least of the Zerg, can withstand full autofire from Terran gauss guns for a short time. The blasters the troopers are armed with do not have the rate of fire nor the penetration capability of guass guns, and the hydralisks and ultralisks in the attack force are considerably tougher than the zerglings. Though concentrated fire will eventually bring the critters down, it will take a substantial amount.

Seeing several hundred of these monstrous creatures stampeding directly at them, shrugging off most weapons fire, is sure to rattle even the most seasoned soldier. But even with their superior size and toughness, the ultralisks will likely fall fairly quickly, as they would draw the most fire immediately.

But even with the behemoths out of the picture, the AT-AT walkers will likely be doomed, as they learn first hand the meaning of the term “zerg rush.” Zerglings and hydralisks swarm the vehicles dozens strongs, ripping apart their metal legs and tearing them down. Then the survivors turn their fury on the troops and smaller combat walkers, with very messy results for the Imperials. The troopers would eventually prevail from their superior numbers, but would be badly battered and demoralized from these initial assaults.

But once they reach the base perimeter, new horrors await them, in the form of sunken colonies and Defilers heaping Plague attacks on them, plus whatever ground forces the Zerg may have held in reserve. Here, unfortunately, is where the Imperial assault breaks like a wave against a dam. Already badly battered by the initial assaults, the troopers’ thin morale disintegrates as fifty-foot tendril-tongues erupt from under the snow to impale and crush them without warning, they’re continually gassed and horribly weakened by the Defilers, and the troopers who get too close to the battlements are ripped to shreds from Zerglings or hit with bolts of acid from Hydralisks.

RESULT: Rebel Decisive Victory. The Imperials retreat with horrible losses, perhaps as much as 40-50% of their ground forces. The Zerg suffer a similar percentage loss, but have no morale problems and are already spawning replacements. The Imperial commanders in orbit, no matter their threats, will not be able to get the troops to brave that meat-grinding horror of the Zerg defenses again. The base is never taken, and all rebel ships make it off planet intact.

MODERN US MILITARY

Tech Level: 10

The US military is not only highly-trained and disciplined, it is also the most technologically advanced military in the world. This makes US soldiers the best suited of any real-world combatants, past or present, for having a chance of taking on the higher-tech forces of the Empire.

The US military maintains very high troop quality, in sharp contrast to the Imperials. In the wake of the wars in Iraq and Afghanistan, the US has a solid core of highly experienced combat veterans, and as a purely volunteer force, the soldiers are in general well motivated to begin with. Even though the Imperial division assigned to the ground assault is very competent by stormtrooper standards, the US soldiers will still be several notches above them in overall quality.

(I’m not an expert in modern military weapons, so forgive me if some assignations of equipment below might be off)

Point defenses will primarily be M-2 50 caliber machine guns or similar, with MK 19 40 mm machine guns (a type of armor-piercing autogrenade launcher) placed in areas where they can expect to be hit with heavy armor units. Both types of guns are mobile, and can be moved around as needed to different hard points. Low-altitude attack craft in place of speeders will be MH-60L Blackhawk attack helicopters.

Realistically, the US troops would also do what they could to heavily mine the most likely approaches the Imperials would take. However, since the Rebels in the movie did not use the tactic (most likely due to lack of prep time), it will be disallowed for the US troops as well.

The primary infantry weapon of the US armed forces is the M-16A2, with some units being equipped with M-4 carbines. Most squads would also be issued at least one M-249 SAW. These weapons do have some advantages over the Imperials’ blasters. First and foremost, they can deliver much greater rates of fire, and can deliver a much more potent kinetic energy punch to their targets.

However, Stormtrooper armor seems very good at absorbing kinetic impact, and given their tech level, will probably hold up to at least a few hits by modern day bullets. In fact, the situation will probably be similar to what US troops encountering J’afa in the original Stargate movie and in the earlier seasons of Stargate: SG-1; it will probably take concentrated autofire on any one target to bring them down.

The same will probably not be true on the other side. Even though the US armor is very effective against kinetic impact and penetration, they are not graded to withstand intense heat. The imperials’ blasters deliver most of their damage as heat, probably at least over a thousand degrees Fahrenheit, concentrated in a focused super-heated stream. Most likely most dead-on shots will penetrate the US soldiers’ armor; those that don’t may have the plasma “splash” against the target like a wave, causing severe secondary burns.

When the imperial assault is first spotted, Blackhawk helicopter sorties are organized to try and take out the AT-AT groups. The helicopters are as fast and nearly as maneuverable as the speeders shown in the movie, and have much longer-ranged weapons. However, the AT-AT’s heavy armor prevents their missiles or their rotary guns from penetrating the main chasis. So they will quickly adopt an alternate strategy: attacking the legs.

As noted earlier, an AT-AT’s big vulnerability is that most of its mass is balanced on four very tall legs. Take out even one of those legs, and the entire vehicle is neutralized. Also, the guns most likely to take out the Blackhawks, the turbo cannons on the AT-AT’s ‘heads’, have a fairly restrictive firing arc, meaning smart helicopter pilots will quickly learn to swing around and come at the walkers from the rear.

The legs are also heavily armored and heavy-duty, and withstood up to repeated blaster fire in the movie. However, missiles are not blasters, and deliver their damage mostly through kinetic impact and explosive concussion. While the walkers may be nigh-invulnerable to the blasters (perhaps by using a thermal superconducting mesh in the armor, which re-radiated away the heat?), kinetic impacts, if strong enough, could just hammer away at the joints until they buckle.

Even so, anything other than a direct hit by an anti-armor missile from the Blackhawks will likely be inadequate, and even then, it will likely take more than one shot.

Modern missiles are very good at homing in on specific individual targets. However, pinpoint-targeting different areas of a target vehicle is something much harder to engineer with modern technology. So hitting the moving, relatively thin legs of the AT-AT’s are going to be difficult. I estimate at best the Blackhawks could take down 1-2 AT-ATs before they themselves become imperiled by organized ground fire.

At the perimeter, the fighting is very fierce, but the US troops are simply too low-tech compared to the Imperials and too out-numbered to prevail. Especially devastating to the US troops are the AT-STs; their speed, maneuverability, and relatively heavy firepower wreak havoc with the US defenses. The surviving Blackhawks pick off what they can, but it likely won’t be enough. When the AT-AT’s with their heavy blasters come within range of the defensive lines, the fight is pretty much over.

RESULT: Marginal Victory for the Imperials. The US forces manage to inflict much heavier troop casualties among the Imperial infantry than the Rebels, thanks to superior rates of fire, but would be much less effective at taking out the enemy armor units, which most of their weapons can’t seriously affect. The only time the Imperial advance is significantly slowed is when the main body of troops reach the defensive perimeter, and all too soon that is breached when the Imperial armor is brought up. The Imperials take down the field generator with numerous rebel ships still on the ground, and capture the base.

STARGATE COMMAND

Source: Stargate SG-1, Stargate: Atlantis

Tech Level: 13-15

Stargate Command itself employs only a few hundred actual combat troops. For this scenario we’ll assume they use normal US troops, as above, to fill out their ranks to the 2000 or so soldiers needed to take the Rebels’ place.

Stargate Command, technically under the auspices of the USAF but more practically its own branch of the US military, has a number of advantages over the ‘normal’ US troops used in the last scenario. Not only do they have captured and adapted alien technology, but they have become highly experienced specialists in fighting battles against foes with superior technology.

Weapons used by the main troops will be as outlined above for the normal US troops. However, it was established that the SGC developed and employed on a regular basis specialized equipment designed to neutralize advantages of the much higher-tech J’afa warriors. They have advanced ammunition that can readily penetrate high-tech armor, and have inserts in their own body armor designed to withstand the plasma blasts of the J’afa staff weapons. Since the Imperials and the Gua’uld J’afa have approximately the same Tech level (18), we can assume that these innovations will be as equally effective against the Imperial snowtroopers. They distribute what they’ll have along these lines to as many of the normal troops as they can, so let’s assume for simplicity’s sake that about half the soldiers have these enhancements.

What this means is that unlike the normal US troops, their weapons can take down individual Imperial troopers with a single shot. So, soldier-to-soldier, they would actually have an advantage, in that the SG teams’ weapons have much greater rates of fire, and would be bolstered here and there by Zat guns and some other captured alien tech. There is also an even greater discrepancy in overall troop quality; the SG teams are the very cream of the crop of the US military, so they would have even better overall training, morale, and motivation than normal US troops.

However, these advantages may not be able to overcome their big disadvantage: lack of advanced armor units. In defending against alien threats in the various series, the SGC had a two pronged approach: space-going battlewagons that could engage in strategic battles in space, and ground troops that could engage in insurgent and guerilla tactics via the Stargates. While both approaches in the end proved very effective, it left a gap in development of their high-tech arsenal: armored fighting vehicles and aircraft.

Basically, the SGC has no high-tech equivalent of the snowspeeders (fighters like the X-303s are designed as high-speed, high-altitude/space attack aircraft, and would be poorly employed here) and will have to rely on what the normal US military used in the last scenario. Thus, they likely won’t have any better success in stopping the AT-AT advance, and will likely only take out a handful of them.

RESULT: Marginal Imperial Victory. Greater troop-to-troop casualties will only slow the Imperials down slightly, given their usual ruthlessness toward their own men. The Imperials will take a greater number of casualties, maybe twice that the normal US military by itself was able to inflict, but in the end the defenses fold as soon as the Imperial walkers smash through the defensive line. The imperials capture a number of rebel ships still on the ground.


Go HERE for part two: Avatar, Traveller, Star Trek, and more.

Review: Avatar

I've finally seen Avatar, after getting it on DVD. Thought I'd do a quick review.

I've watched it twice so far and, surprisingly, it was actually better the second time around. I think that it was because I was able to take in a lot of the little details that passed me by the first time. The story IS cliched, as much a retread of a classic story arc as Star Wars was (the 'Stranger in a Strange Land' motif, ie, hero travels to far off land, befriends the natives, has adventures and becomes a great hero--see also Dances with Wolves, Lawrence of Arabia, Ferngully, etc, etc), but just like with Star Wars, the cliched plot path didn't prevent the story from transcending its expectations.

I did not see the movie on a movie screen in 3D, I saw it on a standard TV screen, so I was able to enjoy the story without being overwhelmed by the special effects. Not that I still couldn't appreciate them, but they weren't the main attraction for me in watching the story.

All that being said, Avatar is an important scifi milestone. Pandora easily is the most fully-realized alien world in on-screen science fiction. Kudos to Cameron and his crew for such amazing attention to detail in creating the alien biosphere of Pandora.

The technology of the Earthers was also created with an eye toward realism. The mecha looked less anime-streamlined and much more like what such a system would look like if made in the real world. I especially like the shots of the starship, complete with glowing-hot radiators on the twin nuclear engines and the translucent icy impact shield on its bow. Gave me goosebumps.

For those of you who frequent the Orbital Vector main site, you might be interested that I'd classify the Humans' technology in the movie at about Tech Level 15, maybe edging toward 16. Some anomalies, though--firearms should have been much more advanced, for example.

An interesting thing I was contemplating the second time through is that I don't think the Pandoran biosphere naturally evolved. There seems to be tantalizing hints (particularly the big floating mountains, the huge apparently invulnerable arches around the Tree of Souls, the presence of super-conducting Unobtanium, plus some other stuff) that the world may actually be built on the ruins of a much older more advanced civilization, maybe even post-Singularity. For whatever reason the inhabitants may have decided to abandon technology and bio-engineer a nature-centric utopia for themselves.

I did think Cameron was a bit too hard on humanity, but then its apparent he was trying to drive home certain points. Despite what some conservative critics may have said about the film, I don't see it as anti-American or anti-military, as some have said. Rather, like most films of its type, its meant as a cautionary tale, showing us the dangers of a what could happen if we let certain forces in our society run out of control. (Ie, no 'green' left on Earth, and humanity apparently run by out-of-control, amoral corporations.)

There are some exceptions, of course. Cameron apparently could not resist taking a few digs at past US administration, but they are few and fleeting.

I don't think every human soldier and worker on Pandora would have gone along with the destruction of Na'vi except for a few scientists and the Hot Aircraft Pilot. I think a lot more would have protested and tried to block Colonel Bad Guy and Corporate Douchebag. But I also realize the film could only get so complicated and long, so the creators had to simplify things a bit with this.

The Na'vi in a way also had to be streamlined in a certain way for the same reason. In order to work, the movie needed to portray the aliens as actual sympathetic characters. However, making them too inhuman, as realistic aliens would be, would take too much time and work that it would distract too much from the story, which was making for a long movie to begin with. Most other scifi films and TV series run into this problem. Because of limited time to tell stories, creators have to choose: should the aliens be human-like, and be characters the audience can relate to, or should they be realistically inhuman, and result in them being puzzling enigmas? Here, Cameron obviously chose the former path, and though it is kind of stretching believability that the Na'vi would look and act so human having evolved on a completely alien world, for the purpose of a two+ hour movie it works well enough.

As I said, the plot as a whole was pretty familiar. Since I myself kind of came up with something similar with part 1 of The Shattered Sky (see the sidebar for links), I can attest Cameron did NOT 'rip off' the story as some people say. Its just seems that when you have certain story elements, certain plots and characters follow naturally for drama's sake. But even if events were in the broad term predictable to anyone who's seen this type of story before, it was in the details that the story become very enjoyable, and at times even surprising.

All in all, it was well worth seeing, and definitely a science fiction movie milestone, mostly for its stunning world-building and satisfying if unsurprising story. Looking forward to the eventual sequel and seeing if I'm right about Pandora being a post-technological society.

The 7 FORGIVABLE Sins Of Sci Fi

A lot has been made about the scientific inaccuracies and logical fallacies we often see in on screen science fiction. While no doubt some of it does stem from just plain ignorance or carelessness, a lot of it actually serves an important story telling purpose.

The first commandment of any form of entertainment is straightforward: You Must NOT Be Boring. This coupled with time constraints, limited budgets, and the need to tell a complete story driven by characters, has led to a number of shortcuts that creators of film and TV science fiction have to take. Its not that they, the writers, the FX crew, etc., are unaware of how scientifically accurate phenomena would actually work, its just that they have to put entertaining the audience and creating a compelling but easy-to-follow narrative first. And that often requires compromises.

This isn't to say that fans aren't right to complain about obviously stupid plot developments, or groan-inducing nonsense technobabble. Only that people should understand that science fiction is primarily about stories and characters first, and if some scientific accuracy has to be sacrificed to enhance either of those, so be it.

1. Cow Goes Moo, Duck Goes Quack, Space Goes Kaboom

In a dramatic presentation, music and sound effects are often used as dramatic punctuation, a tradition that goes back centuries to the earliest plays and operas. Its used so often because its proven itself very effective at evoking visceral responses from the audience. Should a filmmaker give up such a useful and versatile tool in a science fiction film simply because in real life, sound does not travel in space?

The answer is, it depends. Some very successful science fiction has used space silence as an effective dramatic device (2001, Firefly, Planetes). However, these works are almost always aimed at a more mature, thoughtful audience. For a more general audience work, especially an action-oriented one, such abrupt silences can serve to kill the dynamic flow of the story. So using sound in spaceshots, such as engine noises, weapon fire, explosions, etc, as well as background music, is forgivable if it all keeps the story or action flowing smoothly.

NOT FORGIVABLE: Humans breathing and talking in space without explanation (Superman IV, Power Rangers, for example). Even the most non-science-savvy of audiences nowadays know that people can't survive in space without spacesuits, much less go around talking in naked vacuum.

2. Enhance!

A sin scifi shares with many a modern crime show, this is where a computer enhances a visual image in some way that should either be impossible (how exactly do you enhance four fuzzy pixels into a complete mugshot?) or take many hours of tweaking and programming.

This is a necessity mostly born of time constraints. A typical scifi TV show only has an hour, not counting commercials, in which to tell its story. How much of that time do audiences really want to watch a computer operator clicking a mouse and typing at a keyboard to tweak an image into clarity? Even a montage of that would be fairly mind-numbing. So this is a quick little shortcut most scripts use to bypass what would be a scientifically accurate but very boring process to watch.

3. The Universal Up

In scifi TV shows and movies, most ships meet each other in the depths of space always oriented in the same "up" direction. Most combat, too, is usually depicted as two dimensional. Spaceships come at each other from ahead or behind, but rarely from below or from above.

This is mostly a visual shortcut, to avoid confusing the audience. Because make-believe spaceships come in a lot of unusual visual designs, they can be difficult to recognize from odd angles, especially during combat when they may be zipping quickly across the screen. This way the audience can more easily keep track of who's the good guy and who's the bad guy.

There have been exceptions to this, of course (particularly Return of the Jedi), but even then, with the fighters zooming about in three dimensions, the main fleets themselves were arrayed on a more or less flat plain in space as they exchanged shots.

4. And One Gravity For All

In science fiction, most locales are either one Earth-normal gravity, or zero gravity. There is no in between, even on the Moon or Mars or alien planets. Even the most low-tech future societies seem to easily develop magical artificial gravity.

The reason for this stems from the current limits of special effects and most movie/TV budgets. Simply put, all the actors and sets are on Earth, and there's no escaping that a full G is in effect there. Studios have gotten fairly adept over the years at visually fudging freefall with harnesses and other tricks, but these can get expensive, and are usually not used except for certain necessary scenes. In other words, faking anything other than Earth normal gravity can be a budget buster for most productions, so they usually use artificial gravity as a quick and easy end run around that.

5. Cosmic Wharrgarbl

Wouldn't it be convenient if every race, nation and civilization spoke the same language? In many science fiction universes, they do.

Yes, we know that the act of actually translating and learning to speak a completely new, alien language would be a long, complex, and arduously boring process to watch. Like with Enhance! this process is usually shortened dramatically, or even hand-waved away, to save on the audience's sanity and to get on with the story that will actually entertain them.

UNFORGIVABLE: Not providing even an arbitrary explanation for WHY everyone speaks the same language. If even my 8 year old nephew knows enough to question why everyone is speaking the same, then its not something audience members will just shrug away. Universal translators, babel fish, telepathy, a common trading language, etc., just pick one and move on. I'm looking at you, Stargate Atlantis. Earthers show up in a brand new galaxy that has been removed from human contact for 10,000 years and everyone can easily understand each other the first time they meet?

6. Ridged Forehead Syndrome

Aliens are one of the centerpiece concepts of science fiction. From everything we know about evolution, its easily a trillion to one odds that any alien lifeform will end up looking even remotely like us. So why do so many aliens in sci fi look like actors from Hollywood central casting with crinkly foreheads?

The simple answer is, of course, they are. Until fairly recently, expecting a special effect to act would be like asking the moon to dance a jig. If you wanted the aliens in your story to be actual characters instead of some barely-seen rubbery suit or glowy cloud, that meant you had to use human actors. And even Hollywood make-up masters could only make them so alien, especially with the budgets many productions had.

This has changed somewhat with modern computer animation (especially with incredibly convincing CGI characters like Gollum in the Lord of the Rings movies), but even so the process still remains very expensive. So ridged forehead aliens are still forgivable, as long as other measures are taken (language, mannerisms, culture, etc) to show that they're from a world other than earth. It is also forgivable if the presence of near-human aliens is plausibly explained away (such as in the Stargate universe, where many human populations were transplanted off Earth in ancient times to be used as slaves of the alien Gua'uld.)

UNFORGIVABLE: Having near-human/ridged forehead aliens in a sci fi production where the FX budget easily allows for better, less human alien characters. This is a sin especially perpetuated by japanese anime--being animation they aren't limited by FX budgets, and yet too often their aliens come in only two varieties--very human-looking or loathsome tentacle-beasts.

7. Outdated Special Effects

Now, we've all had a good laugh at one time or another at the Styrofoam rocks on the original Star Trek or the hokey muppet Yoda in The Empire Strikes Back. But seeing people put down the entire movie or TV show because of such special effects is definitely a sci fi sin.

We all know the story we're watching isn't real. But we're willing to suspend our disbelief for the sake of being entertained. Its why we can enjoy animated movies even though everything in the film is at least several steps removed from reality; its why we can get into plays even though its obvious we're just watching people shuffle about and talk on a stage with obviously artificial sets. If the story is good enough, whether the FX scenes look realistic shouldn't matter so much as how well they serve the ongoing story and move it along.

The original King Kong is a brilliant example. Does the Kong of the movie even closely resemble or move like a realistic gorilla? No. But is the movie still very entertaining? Definitely yes. The FX are crude by today's standards, but still serve the story of the film and move events along very well.

So this sin is very forgivable IF the special effects crew did the best they could with the technology and budget they had at the time. How well the effects serve the story should always matter more than how realistic they look.

UNFORGIVABLE: using outdated special effects on more modern films; in fact, the bigger budget and more modern a movie is, the less forgivable this sin is. Also, using special effects so much that they dilute the story instead of enhancing it, as was the case of all three Star Wars prequel films.

Let me know if I've forgotten any!