Getting Started

DISCLAIMER: I am not a rocket scientist, merely an amateur that has read a lot of books. Any and all of the information on these pages may be incorrect or inaccurate.

But since I have yet to find a website like this written by a real live rocket scientist, I had to write it myself, as unqualified as I am. However, if I do put inaccurate information on this site, occasionally internet readers will send me corrections. This is the "stone soup" method of website design, with me supplying the stones. Frankly this website is a glorified term paper.

There is some controversy over a few technical details on this site. If you disagree with something you read on this site, first check this page. If you still disagree, your best bet is to go to the usenet newsgroup rec.arts.sf.science and the Yahoo group SFConSim-l and present your case there. If it survives both, I will incorporate your contributions.

Carol Maxwell: "What makes you think you can discover anything? Who are you?

Allan Maxwell: "Nobody. Nobody at all. But the secrets of the universe don't mind. They reveal themselves to nobodies who care."


If you do not understand why space exploration is so important, just watch this video. Be sure to make it full screen.


Keep in mind that whether you are designing a rocket for your SF novel, or for a science fictional wargame, the ship can be the center of attention. Think about the proud series of vessels which formed the focus for high adventure. Vessels with names like Enterprise, Serenity, Seaview (yes, that's a submarine but the principle applies), Luna, United Planets Star Cruiser C57D, Space Battleship Yamato, Battlestar Galactica, Millennium Falcon, Fireball XL5, Polaris, Space Beagle, Discovery, Valley Forge, Dark Star, and the Nautilus (another submarine). And ships that never quite made it, like the Strategic Star Command Galactic Cruiser Leif Ericson. In many cases, the ship becomes a character in and of themselves.

The more real you make the ship, the more real the rest of the story will be.

(ed note: master spacecraft designer Ray McVay comments on the Space Navy Develpment System)

How can a little chart do so much? I've said it before: Soft Science Fiction tries to make technology fit the imagination, and Hard Science Fiction tries to imagine what fits the technology. This chart provides a great framework of technology, logistics, and practical organization to fit one's imagination into.

From Building a Space Navy by Ray McVay (2014)

Introducing RocketCat

This is RocketCat, the official mascot of the Atomic Rockets website. Do not make him angry, you will regret it.

He has a habit of commenting on my explanations, using less diplomacy and more colorful language.

He maintains that he got his name from Elton John, not from any raccoon. He wants to make clear that any rumors about him actually being General Scarr of the Carnivorian Republic are totally unfounded. But he does get a little tense if you mention Ulthar. I asked him if his parents were Space Cat and Moofa and he just rolled his eyes at me. Which was not a denial.

But if he ever gets his claws into Alf, that pathetic alien life form is going to find itself strapped to a live thermonuclear warhead with one kiloton's worth of yield for each cat he's eaten.

You will occasionally see Sneaky the insouciant Cat lurking about the website as well. Don't tell RocketCat, the two do not like each other very much.

Math Is Our Friend

RocketCat sez

Alright you ground-grippers! My name is RocketCat! I'm here to make you into steely-eyed missile people, blasting off and leaving all those trekkies choking on your rocket exhaust.

But we are talkin' Rocket Science here, people! That means ... duntDahDUHHHHH!!! ... Mathematics! If this frightens you, well, go have a seat over there by the trekkies. I'm not talking calculus, I mean math you can do on a dollar store pocket calculator. You can handle that, can't you? Learn where the multiply, divide, square, square-root, natural logarithm (ln), and trig keys are; and you'll be fine.

If ya can't be bothered to do the math, then you can always just look at the pretty pictures. And there are one or two pages here that have hardly any equations at all.

Real rocket scientist know what metric units to use in rocket equations (metre—kilogram—second, centimetre—gram—second, SI). I know that none of them are reading this. So, for the benefit of all you ground-grippers, I'm going to explicitly specify what metric units to use in each equation. Because I know if I don't, it will be just too blasted easy for you to make a mistake in units and get an answer that is a thousand times too big or small.

Or if you prefer, it is because I'm trying to make the equations easier for a non-rocket-scientist to use. You decide.

It is all in the Metric System as well. Because the entire non-USA world in general, and the realm of science in particular uses metric. Get over it.

I'll try to explain things simple, so non-science types can still understand. But there are limits. I assume you at least know what the difference is between a planet and a galaxy. You will have a big head-start if you've had a course in high-school physics (and didn't flunk).

If you can master this website, you will be a steely-eye missile person; and any science fiction you create will have better scientific accuracy than 99% of the crap that is out there now. Plus along the way I'll leave you a few quotes from novels and observations that could spark some fruitful ideas to develop for your work.

Don't panic. All the equations in the following are about high school algebra level. They are all easy enough to manage on an average scientific calculator, a computer spread sheet, or a slide rule for that matter. If needed, the reader should review the rules on Significant Figures.

Having said that, you will find the following pages much easier to understand if you have taken an introductory course in Physics in high school or whatever.

If you are using a pocket calculator, try to find the scientific kind. You will need one that handles natural logarithms (the ln key) and square roots (the key). To do square roots using the calculator program that comes with Microsoft Windows, use the "View" menu to set the view type to "Scientific", click the "Inv" checkbox, then use the "x^2" key. Be sure to un-check the "Inv" checkbox when you are done.

If the equation uses tan(), sin(), or other trigonometric functions, pay attention to what input unit the function wants. If you are using a pocket calculator or the Windows calculator program it defaults to wanting the input to be in decimal degrees. If you are using a spreadsheet or writing your own home brew computer program, the TAN() and SIN() functions want the input to be in radians.

If you are going to do the equations in the Relativity section, you will need a calculator that can handle the hyperbolic functions sinh, cosh, and tanh. On the Windows calculator, click the "Hyp" checkbox, then use the sin, cos, and tan keys. Again, remember to un-check the "Hyp" box when you are done.

Acceleration
gm/s2
19.81
⅟100.981
⅟1000.0981

When I was a boy, you had to do logarithms by looking them up in a book of tables, or with a slide rule. Now you young whipper-snappers can get a calculator at the drug store for $9.95 that will do it with the press of a key.

As per usage in computer programming languages, the symbol "*" means "multiplication". In the following equations, be sure that you use the same units throughout, to minimize that type of error. I generally use meters - kilograms - seconds. Obviously meters * 1000 = kilometers.

Beware that items like a rocket's exhaust velocity are often given in kilometers per second, instead of meters per second. It doesn't matter which you use, but be sure to use the same units everywhere. (For those readers who actually have some knowledge of rocketry: Yes, I know it is inconvenient to use meters per second with all those annoying ciphers. But I still used them throughout this site so as to give one less source of error for those readers who are new to all this.)

Also useful is AU * 1.49e11 = meters. AU's are "astronomical units", the distance between the Earth and Sol. Planetary distances are generally given in AUs, so you have to know how to convert them into the more useful "meters".

1.49e11 is "scientific notation", a fancy way of writing 149,000,000,000 without all those messy zeros. For those who are familiar with scientific notation but not with computer scientific notation, 1.49e11 = 1.49×1011, the "e" stands for "exponent".

"Kilo" means "thousand", e.g., one kilowatt = 1,000 watts = 1e3 watts. "Mega" means "million. Giga" means "billion". There is a handy table of these prefixes here.

Be told that this website uses the mathematical notations in common use in the United States. A comma is used between each group of three numbers and a period is used as a decimal point, e.g., 23,000.17 = twenty three thousand and seventeen-hundredths. 109 is "one billion" with the prefix "giga-", unlike UK nommenclature where 1012 is "one billion" with the prefix "tera-".

Information about the mass and radius of various planets can be found here: http://nssdc.gsfc.nasa.gov/planetary/planetfact.html

In the sections on power sources and the section on spacecraft weapons many of the items have outputs measured in watts. This website has a nice table of various watt levels and comparison items so as to get a feel for things.

Back to the Past

RocketCat sez

All you young whipper-snappers who think that science fiction was invented in 1977 with the first Star Wars movie, I have to inform you that you are sadly mistaken. SF was old when your great-grandfather was born. Get a load of this:

  • "Blaster" dates back to 1925 in Nictzin Dyalhis' When the Green Star Waned. By the time the term was used in the first Star Wars movie it was fifty-two years old.
  • "Disintegrator ray" dates back to 1898 in Garrett Serviss' Edison's Conquest of Mars.
  • "Needler" dates back to 1934 in E.E."Doc" Smith's The Skylark of Valeron.
  • "Stunner" dates back to 1944 in C. M. Kornbluth's Fire-Power.
  • Isaac Asimov invented "force-field blades" in his 1952 novel David Starr, Space Ranger, which was the father of the light-saber.
  • There was a form of "virtual reality" in Sir Arthur C. Clarke's 1956 novel The City and the Stars, and a more limited form in E.E."Doc" Smith's 1930 story Skylark Three.
  • "Tractor Beam" had its roots in the 1928 novel Crashing Suns by Edmond Hamilton, where it is called the attractive ray. Also in 1928 E.E."Doc" Smith's novel The Skylark of Space had attractors which drew an object closer and repellors which pushed objects farther away. The first use of the term "tractor beam" is in Doc Smith's 1931 novel Spacehounds of IPC. Thirty-five years later in 1966 the term was borrowed by the TV show Star Trek. Eleven years later in 1977 it showed up in the first Star Wars movie.
  • "Force Fields" seem to have their origin in E.E."Doc" Smith's 1930 novel Skylark Three. Ray screens defend against deadly weapon beams, and repellor fields turn back shells, missiles, and other weapons composed of matter (in other words it deflects them). In later science fiction, force fields and deflector shields stop both energy and matter, there is no longer two types of field.
  • Dreadnought is from the real world, refering to the largest most deadly type of seagoing warship, the first one was in 1906. The term was popularized for combat spacecraft in E.E."Doc" Smith's Lensman series, first appearing in 1937 inside Galactic Patrol. Smith did have a odd habit of spelling it "Dreadnaught".
  • Zero population growth is discussed in Walter Kately's 1930 story "The World of a Hundred Men."
  • Power from nuclear fusion appears in Gawain Edwards' 1930 story "A Rescue from Jupiter."
  • Atomic bombs are found in Sewell Wright's 1931 story "The Dark Side of Antri."
  • A "tiny computing machine about as large as the palm of a man's hand" (Palm PDA?) is featured in R. F. Starzl's 1931 story "If the Sun Died."
  • And an unprotected man exposed to the vacuum of space but did not explode appeared in Nathan Schachner and Arthur Zagat's 1932 story "Exiles of the Moon."

Of course you shouldn't try to go travel the space lanes without your official Space Cadet handbook (1952).

Or Ron Turner's Space Ace pop up book (1953).

On Shaky Ground

RocketCat sez

We are going to emphasize scientific accuracy here, is that clear? I'll let you have the accuracy slide once and a while, but don't make a habit of it and wash your hands afterwards. I want to see no Technobabble, a bare minimum of Handwavium, and low amounts of Unobtanium. Read what The Tough Guide to the Known Galaxy says about Hard SF.

What? You never heard of Handwavium? I'll let Ken Burnside explain them to you:

Handwavium

It flat out violates laws of physics. We're waving our hands and saying pay no attention to the man behind the curtain. FTL is handwavium in its many forms. I tend to hold that all these designs that ignore thermodynamics are handwavium, as are force fields and gravitic whosimawatchises.

Ken Burnside
Unobtanium

We can't build a physical example of it, but insofar as we can postulate that it can be built at all, the laws of physics say it would behave like thus and so. Calculating the range and damage drop offs of a laser of a given wavelength, aperture size, input energy and conversion efficiency to make a weapon is pretty much unobtainium right now. While Handwavium and Technobabble tell you what you CAN do, Unobtainium usually tells you what is NOT possible.

Ken Burnside
Technobabble

"We've reversed the polarity of the tetryon flow through the main deflector dish, and the Borg's shields have dropped, sir." Or, "His midichlorians are more powerful than Yoda's!" or "Our spaceship is pulled through the aether by the outrage of honest politicians." are all examples of technobabble. Technobabble need not be bad, though in general it's only noticed when it is done poorly.

Ken Burnside

The ratio of Unobtainium to Handwavium to Technobabble defines how "hard" your setting will seem to be to the reader. One of the reasons why I (Ken Burnside) love Mote in God's Eye is that they (authors Larry Niven and Jerry Pournelle) have only two blatant pieces of handwavium (the Drive and Field) and they quite carefully worked out the ripple effects of them before using them. Mote has a very high Unobtainium quotient, as does a lot of Heinlein's space fiction.

The Exordium series has a lot of well reasoned out Handwavium that's applied consistently, but has very little that's directly constrained by Unobtainium (A chief example of Unobtainium is the Tenno glyphs). It also uses very little technobabble, though it uses some (mostly when dealing with aliens).

Most of the Lensman series can be seen as Pure Technobabble with a bit of Handwavium thrown in to anchor it in plausibility.

Star Trek and most television SF is a mixture of pure technobabble and some handwavium. Things work because they make the plot work. Things fail because if they don't the plot fails.

Technobabble can easily lead to a farcical read.

Ken Burnside

To this list I'd like to add the term "MacGuffinite". It comes from the term "MacGuffin", popularized by director Alfred Hitchcock. "MacGuffin" means a plot device that motivates the characters and advances the story, but has little other relevance to the story. I define "MacGuffinite" as some valuable ore, substance, or commodity that hopefully introduces no unintended consequences to the SF universe you are creating.

Dramatic Reasons

Robinson's First Law of space combat

Something hitting at 3 km/sec (kips) delivers kinetic energy broadly equal to its mass in TNT.

Rick Robinson
Robinson's Second Law of space combat

For every kilogram of handwavium you remove from a setting, you add about 10 cubic meters of impossible to maintain plumbing.

Rick Robinson

Most people instinctively know Burnside's Zeroth Law of space combat:

Burnside's Zeroth Law of space combat

Science fiction fans relate more to human beings than to silicon chips.

Ken Burnside

That is, while it might make more logical sense to have an interplanetary battle waged between groups of computer controlled spacecraft, it would be infinitely more boring than a battle between groups of human crewed spacecraft.

A one man fighter spacecraft would be a more effective weapon if you removed the fighter pilot, their life support, and their acceleration limits, and then replaced them with a computer. You would basically be converting the fighter spacecraft into a roving missile bus, and removing the logical justification for the existence of fighter spacecraft altogether. But fighter spacecraft have to exist, according to the Zeroth Law (well, actually not. Fighters don't have to exist if there are humans on the carrier/missile boat and/or the target ship).

Yes, there are exceptions to Burnside's Zeroth Law in science fiction, but they are few, far in between, and the result of exceptionally skilled authors. These are the "exceptions that Test the rule" (the original aphorism is from the Latin, and the word "probat" in this context should be translated as "test", not "prove"). Examples include "Longshot" by Vernor Vinge, and "Sun Up" by A. A. Jackson and Howard Waldrop.

In a discussion I witnessed, Henry Cobb described a combat spacecraft with a Magic Fusion Torch (i.e., an exceedingly powerful unobtanium propulsion system). Eric Henry asked why not replace the human pilot with a computer. Henry Cobb correctly noted:

By the Zeroth Law, the Magical Fusion Torch only works when there is somebody on board to maintain the enchantment.

Henry Cobb

Eric Henry wisely observed:

Ah. The Schrödinger Drive.

Eric Henry

The above exchange may seem humorous, but I have seen the same concept actually used in some SF novels.

In Larry Niven's "The Borderland of Sol", FTL navigation requires the use of a device called a mass pointer or mass sensor. This is described as a "psionic device that must be watched by a mind and not a machine." The effective result is to enforce Burnside's Zeroth Law: without requiring a mass pointer, starships in Niven's universe could be totally computer run and would not require human pilots.

In the 1984 Atari 800 computer game Quest of the Space Beagle, the FTL drive requires a human pilot. As the ship enters FTL, the jump must be balanced or the ship goes off course. The only way to to detect an imbalance is by noticing alterations in the flow of time. And computers cannot notice such alterations since their only sense of time is measured by ticks of their system clock. (In my long and misspent youth, I did the illustrations for that game's manual.)

And in David Lynch's movie adaptation of Frank Herbert's novel DUNE, the wargame StarForce Alpha Centauri, and the RPG Universe, psionic human beings are the FTL drive. No humans, no starship.

Unfortunately, as a Hyperspace-driven vessel accelerates into the fourth-dimension, temporal perturbations occur that "wobble" the vessel off-course. These perturbations must be compensated for if the ship is to arrive at its chosen destination. A computer (such as Space Beagle's Beagle) is unable to adjust the temporal imbalance because time is an aspect of organic awareness and must therefore be adjusted by an organic awareness; in other words, you!

From the manual for QUEST OF THE SPACE BEAGLE by Scott Lamb (1984)

Another annoying fact is that realistic spacecraft propulsion systems are incredibly weak. They will take forever to push the ship to anywhere farther than, say, Luna. So SF authors try to jazz things up by postulating more powerful propulsion systems. Alas, they then run full tilt into Jon's Law for SF authors.

Jon's Law for SF authors is closely related to Niven's Kzinti Lesson. It states:

Jon's Law, part 1

Any interesting space drive is a weapon of mass destruction. It only matters how long you want to wait for maximum damage.

Jon Souza
It goes on to say:
Jon's Law, part 2

Interesting is equal to "whatever keeps the readers from getting bored."

Jon Souza

As an example, a spacecraft with an ion drive capable of doing a meager 0.0001g of acceleration may be scientifically realistic and the exhaust is relatively harmless. However, to most of the audience it will not be interesting. "Nine months just to travel to Mars? How boring!"

The author, not wanting his book sales to go flat, hastily re-fits the hero's spacecraft with a fusion drive. The good news is that the ship can make it to Mars in twelve days flat. The bad news is that the ship's exhaust is putting out enough terawatts of energy to cut another ship in two, or make the spaceport look like it was hit by a tactical nuclear weapon.

The author can still use the drive, but must consider the logical ramifications of the wide-spread civilian availability of the equivalent of thermonuclear weapons. Consider: the more energy the drive contains , the worse the damage if an accident occurs. How would you like to have the captain of the Exxon Valdez skippering a tramp freighter with an antimatter drive? That brilliant mushroom cloud you see marks the former location of Clinton-Sherman spaceport. The more devastation a propulsion system can wreck, the shorter the leash the captains will be on.

So one of the logical ramification is that if drives are too powerful, there won't be any colorful tramp freighters or similar vessels. As a matter of fact, civilian spacecraft will probably by law be required to have a remote control self-destruct device that the orbital patrol can use to eliminate any ship that looks like it is behaving erratically or suspiciously.

Most of the nasty effects of Jon's Law are due to the propulsion system's exhaust. The presence of an exhaust is because rockets use Newton's Third Law (the one about action with equal and opposite reaction). Canny SF authors postulate some kind of hand-waving reactionless drive in an attempt to avoid Jon's Law. Reactionless means no exhaust is required. You feed electricity in, and the ship is magically accelerated. The "gravitic impellers" from David Weber's HONOR HARRINGTON series is an example of a reactionless drive.

Unfortunately such canny SF authors then run smack dab into Burnside's Advice, which is;

Burnside's Advice

Friends Don't Let Friends Use Reactionless Drives In Their Universes

Ken Burnside

The trick is making a reactionless drive that doesn't give you the ability to shatter planets with the Naval equivalent of a rowboat (which would throw a big monkey wrench into the author's carefully crafted arrangement of combat spacecraft). Reactionless drives, with no fuel/propellant constraints, will give you Dirt Cheap Planet Crackers. If you have a reactionless drive, and stellar economics where most of the common tropes exist (privately owned tramp freighters), you also have gravitic drive missiles. And avoiding Planet Crackers Done Real Cheap is almost impossible to justify on logical grounds, the SF author is faced with quite a daunting task.

Hollywood Reasons

I often bitterly complain about the lack of scientific accuracy in TV and movie SF shows. Todd Boyce of Ninja Magic actually works in Hollywood, and explained to me the facts of life about media SF:

To boil down all the possible reasons, it is because of one or more of the following:

0) It's a business

This is a business venture - you put money in with the expectation that more money will come out. The general audience is historically happier watching space ships woosh by shooting glowing bolts of energy than they are watching a slowly rotating spaceship lazily drift across the screen. If you're putting tens or hundreds of millions of dollars on the line, you go for the shooty-wooshy space ships every time, pure and simple.

1) TPTB (The powers that be) don't care.

If whats on the screen looks good, and the storytelling is sufficient, then scientific accuracy rarely if ever matters. If they don't care that cars don't blow up when shot with bullets, why should they care about the theoretical effects of FTL travel.

2) There isn't time to dissect and fix scientific inaccuracies

Once production on a movie is started, it is an unstoppable steamroller with a tight deadline. If the script says a spaceship wooshes by, the people working on the film don't have time to work out what kind of propulsion it uses - they just make the engine glow, push it across the screen in an interesting way and move on to the next shot.

3) The decisions are made in too many places and it isn't even thought about except by people who aren't in positions to make judgment calls.

A jet fighter shoots missiles at a big space ship hovering above a city. The director tells the visual effects supervisor to make it happen. The visual effects supervisor tells the digital effects supervisor to make a space ship and to make a jet fighter woosh by and shoot some missiles at the space ship while he goes off and directs the on-set pyro effects.

The digital effects supervisor tells the modeling supervisor to have his team make a space ship and jet fighter and tells the FX supervisor to have his team make some missiles shoot, engine effects, vapor trails, smoke trails and whatnot.

The modelers build a jet fighter and give it harpoon missiles. The modeling supervisor says it looks good. The digital effects supervisor says it looks good. The modelers are done with their job and get put on another production.

The FX supervisor hands the model to the FX team who look at the fighter and say "um...that's not really the right kind of missile to do an air-to-air attack..." "Sorry, the modeler is off the show and these have been approved. Can't change it now" is the response. So the FX team launches harpoon missiles at the space ship.

The final shot is shown to the director/visual effects supervisor and it looks cool, but don't pick up on the fact that the wrong missile is being used. It's approved and put into the film.

(You're probably sensing that this is a true story and know what movie I was working on at the time.)

4) The script-reader's gauntlet

Writers use descriptive language to express action in their script. They don't often get into technical details because each page of a script is supposed to represent roughly one minute of screen time. A writer who spends his time describing the intricacies of a space ships propulsion system is a writer who finds his scripts in the script-reader's trash can.

People who write heavily technical novels are almost always terrible script-writers as they have difficulty working within the confines and limitations of that medium. The scripts that pass through the script-reader's gauntlet will likely be of the less technical variety.

5) People in film making have education in film making, they don't usually have PhD's in physics/astrophysics. And people who have PhD's in physics/astrophysics don't usually know how to make a good film.

It's not that they aren't smart enough, it's that their focus of expertise is in other areas. That's why they hire consultants if they're trying to do something with any degree of accuracy, but even then, accuracy is desirable only if it doesn't interfere with the storytelling. Often, things are set in motion that can't be changed after the fact anyway and you just have to shrug your shoulders and say "That's the way it has to be" if you learn too late of some scientific ramification.

6) The power of ego

You know how people fall all over themselves when a famous actor is nearby? Its worse when companies deal with well known directors. Just yesterday we were kicked out of the screening room during our dailies because Michael Bay was parking and MIGHT be needing it. With that sort of hysteria going on, are you going to be the one that walks up to him and say "this is totally unrealistic and you need to change it" knowing that saying so will mean the end of your employment?

What the director says goes, and few people have the will or the power to contradict him. Film making isn't usually done by committee, it is done by imperial decree and if the decree is that cars blow up when shot with bullets, then that is the way it is.

I'm sure there's a few others I've missed but, speaking of unrealism in Hollywood movies, I need to get back to work on a sequence involving bits of LA breaking off and sliding into the ocean because the Earth's magnetic field has collapsed.

I'm not kidding.

Todd Boyce

A Final Warning

But beware the dangers of reading this website {very big grin}. Tom Clark had this to say:

Ruined! It's all ruined! And it's all your fault. Particularly you, Nyrath!

I've been having to travel quite a bit lately, and for entertainment I've been reading David Drake's Lt. Leary series of novels. Pretty harmless space opera mostly, similar in vein to the Horatio Hornblower or (more accurately) Patrick O'Brian's series of books about Capt Jack Aubrey and surgeon/spy Stephen Maturin in the Royal Navy during the fight against Napolean.

The basic premise and plot didn't bother me, not even the "sail" metaphor Drake adopted for his FTL system. This drives the ships to be lightweight - a corvette like the Princess Cecille is about 150 meters long and weighs 1200 tons empty - and the ships are restricted to about 2-3.5 Gs of thrust. And yes, they land on planets. Lift-off must be a fairly leisurely affair. Propulsion in atmosphere is by "plasma thrusters" which use fusion bottles as a power source, and water as reaction mass. Outside the atmosphere, they use anti-matter powered High Drives to drive the ship. (They are also apparently converting normal matter to antimatter on the fly for energy. Nice bit of sorcery there.) So far, so good.

Then they get to the armament. The ships mount turreted plasma guns (which we already know won't work because of the work Nyrath has done on his Atomic Rockets page), but as he says its the meme that won't go away. But these are the secondary weapons....

Primary weapons of these ships are kinetic-kill weapons, anti-matter driven torpedoes launched from tubes in the side of the ship. Thirty-ton kinetic-kill torpedoes. And the Sissy carries twenty of them. (Which means half again her mass is weaponry...) Now, the torpedoes accelerate at 12 Gs, which is OK given that their targets only accelerate at 2 G usually...but then Drake goes on to say that the missiles can reach a maximum velocity of 0.6 C in combat conditions. And that they do so in 8 minutes.

Now, before I started hanging out here, I probably would have bought that statement at face value and driven on. But no...now my innocence has been lost, and it kept eating at me, until I started doing the numbers.

- At 12 G, and assuming zero initial velocity, it would take one of those torpedoes about 420 hours to reach that velocity. That's about 18 days, if you're counting. It would also cover 1.4E11 kilometers while its at it. Even with a 6:1 acceleration advantage, I don't want to think about how large a sphere a ship that can accelerate at 2 G continuous for 18 days would be... Did I mention that the torpedoes don't carry seekers on them? They have some sort of rudimentary command link control, but no terminal guidance seekers.

- At impact, each torpedo would unleash the kinetic equivalent of about 35,000 gigatons on its target. This is considerably more than I would expect to have to use to kill a ship-sized target....in fact, with 20 stowed rounds, the Sissie is a threat to a significant portion of the inhabited galaxy. (Since this is a relativistic weapon, I used the formula's found here.

In one book, two torpedoes miss their target and enter the upper atmosphere of an inhabited planet....and disappear harmlessly in "a flash of plasma". Ummm...sorry, don't think so. Even if 30 tons of missile turn into plasma on contact with the atmosphere (and at 0.6 C I don't think they'll have time to melt), they are still 30 tons of plasma moving at 0.6 C! So much for that inhabited planet.....

So...now I'm ruined. If Drake had just done a little math, and maybe set the terminal velocity of the torpedoes to 0.06 C, or even 0.006 C, things would have worked out much better. But no...now thanks to the "education" I've received here, slips like that come back to haunt me in my sleep.

Frankly, it would have been fine if Drake hadn't thrown that "0.6 C" number in there - the missiles have a high enough margin of acceleration versus the ships to make them a credible threat. It's just that, as one of H. Beam Piper's characters once said, "C makes for an awfully long lever." Ships capable of tossing around high-relativistic weapons become planet-killers in relatively short order. You don't need redirected asteroids - which is what brought about the end of galactic civilization the last go-round - to kill a civilization on a planet. One corvette with a load of torps can do it handily.

So a word to authors who like to throw around big numbers....Do the math first! Please!

I need the sleep....

Tom Clark
RocketCat sez

You say that knowing the science ruins your enjoyment of things with sketchy science? Boo-hoo, cry me a river. So I suppose your knowledge of grilled steak ruins your enjoyment of hamburgers that taste like cardboard? Well I guess we'd better forbid everybody from ever tasting a steak. They'll be happier that way.

By that idiot logic your knowledge of knowledge is ruining your enjoyment of life. Wrong. Thomas Gray said "Thought would destroy their paradise. No more; where ignorance is bliss, 'Tis folly to be wise." What a load of hooey. Sticking your head in the sand never works.

No, the solution is to demand higher quality SF like Tom Clark said, over and above the fact that scientific knowledge is worth knowing for its own sake.

The Green Hills of Earth

Let the sweet fresh breezes heal me
As they rove around the girth
Of our lovely mother planet
Of the cool, green hills of Earth.

We rot in the molds of Venus,
We retch at her tainted breath.
Foul are her flooded jungles,
Crawling with unclean death.

[ --- the harsh bright soil of Luna ---
--- Saturn's rainbow rings ---
--- the frozen night of Titan --- ]

We've tried each spinning space mote
And reckoned its true worth:
Take us back again to the homes of men
On the cool, green hills of Earth.

The arching sky is calling
Spacemen back to their trade.
ALL HANDS! STAND BY! FREE FALLING!
And the lights below us fade.

Out ride the sons of Terra,
Far drives the thundering jet,
Up leaps a race of Earthmen,
Out, far, and onward yet ---

We pray for one last landing
On the globe that gave us birth;
Let us rest our eyes on the fleecy skies
And the cool, green hills of Earth.

Robert A. Heinlein

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