Moons of Jupiter Planetcrawl

A long, long time ago (I can still remember how those blog entries used to make me smile) I wrote about the Solar System and its vastness, pondering:

In light of [the sheer size of space], and the fact that the solar system contains 8 planets, 5 dwarf planets, 335 moons and millions of asteroids, minor planets, comets, trojans, centaurs and the like, you really have to wonder why science fiction has obsessed for so long about interstellar and intergalactic empires. Isn't the solar system big enough? 

It strikes me now that the answer is fairly obvious: aliens. There aren't any in the solar system, or at least not ones we can wage war on/fuck/misunderstand, so SF authors by necessity need to look beyond it if they want Klingons.

But the fact remains: the Solar System is massive. Consider this for a second: the distance between Jupiter and Saturn is from 600 million kilometres to 2 billion kilometres. Jupiter has, at current count, 66 moons. Saturn has 62. Uranus and Neptune have another 40 between them. There have been 1,200 Transneptunian Objects recorded. There is a lot of stuff out there to get lost in. Indeed, the question I am currently considering is not so much "Why bother with what's outside the Solar System?" as "Couldn't you just set a game among the moons of Jupiter or Saturn?"

The moons of Jupiter vary hugely in size - from massive rocky Ganymede, bigger than Mercury, to tiny Cyllene, only 3km in diameter. They also vary in character: Icy Europa may have a great warm ocean beneath its surface which harbours life, while Io is a world of magma and volcanoes. Probably only 4 - the Galilean moons of Ganymede, Europa, Io and Callisto - are "settle-able" in the SF sense, but think of the potential in the 58 others. Secret bases for space pirates. Impossibly ancient and haunted alien monuments. Mines to be warred over. Space stations right and left. Orbital rigs for siphoning gas from Jupiter itself, built on construction bases bigger than cities, that circle elliptically around Callisto.

The thing about the Moons of Jupiter Planetcrawl is that the distances make sense. These moons are generally about 200,000 km apart at their closest (although of course, at the opposite ends of their ellipses, they are a heck of a lot further), which is traversable in a few hours at the speed of, say, Voyager 1. An inter-lunar craft would probably be a lot slower, because Voyager 1 is a big fat cheat and has the benefit of decades of acceleration, but still - it's the sort of travel that is do-able in the Star Trek "set a course for Ganymede and we'll be there by Friday" sense, and is imaginable without too much handwaving if you want your SF hard. And since your scope is somewhat restricted, you can actually flesh out your locations in a lot of detail - you don't end up with Traveller-esque abstraction in which each solar system has a single interesting planet about which there is a single interesting fact and a single culture. You can go deep: what's going on with Callisto? How does that affect what's going on with Io? What's with the planetary war on Europa and will the Jovian orbiters get involved?

I happen to have recently bought Diaspora. Maybe the planets are aligning.

Atomic Rockets

I'm going all hard science fiction crazy at the moment with this blog, I know. Bear with me. I just wanted to link to the excellent site Atomic Rockets, an attempt to create a lay person's guide to rocketry and the science behind hard science fiction. (Aside from its contents, one thing you have to love about the site is its eccentric layout. As with all internet sites created by amateurs and which have been around for a long time, it truly feels as if it harks from a bygone era. I wonder if one day there will be an Antiques Roadshow of old websites?)

Anyway, browse through it and enjoy. Some particular favourite passages of mine, from the "common misconceptions" section:

Rockets Got Wings

If your rocket has a multi-megawatt power plant, an absurdly high thrust thermal rocket propulsion system, or directed energy weapons it will need huge heat radiators to purge all the waste heat. Otherwise the rocket will melt or even vaporize. Radiators look like large wings or arrays of panels. The necessity of radiators a real problem for warships since radiators are pathetically vulnerable to hostile weapons fire.

...

Rockets Don't Got Windows

Spacecraft have no need of windows or portholes, for much the same reason as a submarine. (No, the Seaview doesn't count. Strictly science fiction. There are no panoramic picture windows on a Trident submarine). Windows represent structural weakness, and there really isn't much to see in any event. Unless the spacecraft is orbiting a planet or docking with another ship, the only thing visible is the depths of space and the eye-searing sun. And unlike submarines, windows on a spacecraft also let in deadly radiation.

Star Trek, Star Wars, and Battlestar Galactica to the contrary, space battles will NOT be fought at a range of a few feet. Directed energy weapons will force ranges such that the enemy ships will only be visible through a telescope. Watching a space battle through a port hole, you will either see nothing because the enemy ships are too far away, or you will see nothing because a reflected laser beam or nuclear explosion has permanently robbed you of your eyesight.

The navigation room might have an astrodome for emergency navigation. But for the most part windows will be omitted in favor of radar, telescopic TV cameras, and similar sensors.

...

Fuel Is Not Propellant

In a rocket, there is a difference between "fuel" and "reaction mass." Rockets use Newton's third law of Action and Reaction in order to move. Mass is violently thrown away in the form of the rocket's exhaust and the reaction accelerates the rocket forward. This mass is of course the "reaction mass." It is sometimes also called "remass" or "propellant."

The "fuel" is what is burned or whatever to generated the energy to expel the reaction mass. For example, in a classic atomic rocket, the fuel is the uranium-235 rods in the nuclear reactor, the reaction mass is the hydrogen gas heated in the reactor and expelled from the exhaust nozzle.

There are only a few confusing cases where the fuel and the reaction mass are the same thing. This is the case with chemical rockets such as the Space Shuttle and the Saturn 5, which is how the misconception started in the first place.

Automobiles, airplanes, and boats are sizable vehicles with relatively small fuel tanks. Not so rockets. An incredibly powerful rocket might approach having half its mass composed of reaction mass and the other half structure, hull plates, crew members, and everything else. But it is more likely that 75% of the mass will be reaction mass. Or worse. Most rockets are huge propellant tanks with a rocket engine stuck on the tail and a tiny crew habitat stuck on the top.

The Solar System

[Had a busy couple of weeks socially, academically and business-ily. (Can't think of an appropriate adverb to do with business for that sentence.) Will be back to daily updates from now on.]

From Bill Bryson's A Short History of Nearly Everything:

Now, the first thing you are likely to realise is that space is extremely well named and rather dismayingly uneventful. Our solar system may be the liveliest thing for trillions of miles, but all the visible stuff in it - the Sun, the planets and their moons, the billion or so tumbling rocks of the asteroid belt, comets and other miscellaneos drifting detritus - fills less than a trillionth of the available space. You also quickly realise that none of the maps you have ever seen of the solar system was drawn remotely to scale. Most schoolroom charts show the planets coming one after the other at neighbourly intervals - the outer giants actually cast shadows over each other in many illustrations - but this is a necessary deceit to get them all on the same bit of paper. Neptune in reality isn't just a little bit beyond Jupiter, it's way beyond Jupiter - five times further than Jupiter is from us, so far out that it receives only 3 per cent as much sunlight as Jupiter.

Such are the distances, in fact, that it isn't possible, in any practical terms, to draw the solar system to scale. Even if you added lots of fold-out pages to your textbooks or used a really long sheet of poster paper, you wouldn't come close. On a diagram of the solar system to scale, with the Earth reduced to about the diameter of a pea, Jupiter would be over 300 metres away and Pluto would be about two and a half kilometres distant (and about the size of a bacterium, so you wouldn't be able to see it anyway). On the same scale, Proxima Centauri, our nearest star, would be 16,000 kilometres away. Even if you shrank down everything so that Jupiter was as small as the full stop at the end of this sentence, and Pluto was no bigger than a molecule, Pluto would still be over 10 metres away.

In light of that, and the fact that the solar system contains 8 planets, 5 dwarf planets, 335 moons and millions of asteroids, minor planets, comets, trojans, centaurs and the like, you really have to wonder why science fiction has obsessed for so long about interstellar and intergalactic empires. Isn't the solar system big enough?

One day I'd like to see a science fiction setting in which humans have colonised the solar system, but nowhere outside it - perhaps because travelling at the speed of light, or faster, simply hasn't been invented. This would be a fractured, multiethnic star system, where travel between planetary bodies takes weeks, months or years and communication is carried out by radio, and where military conflict is a projection of warfare on planet earth. In other words, a little like the era of European colonial expansion around the mid-18th century, except probably more likely dominated by countries such as China, India and Brazil.

Perhaps this setting already exists, and I just don't know about it. If so, its creators just haven't done a good enough job of getting it out there, dammit.