Monday, September 10, 2012

Realistic Starships Are Tubes

Out in space, there are two requirements that determine the physical shape of a starship.

The first is heat management, by which I mean dumping heat to keep a starship from overheating. Any kind of drive, even an external drive, will produce a vast amount of heat. And unfortunately, vacuum is an excellent insulator. Also, the temperature of space in Earth orbit is 394 Kelvin (120 Celsius) when exposed to the sun so that line about "space" being cold is just lying crap.

Parenthetically, it's amazing how much lying crap one has to dig through in order to find that number, 394 Kelvin. Cryptic imbeciles who think they're elite engineers do a song and dance because they believe ordinary people are incapable of grasping that it will be cooler than 394 K in the shade. Give me a fucking break.

The second requirement is shielding from radiation and micrometeorites. Isaac Kuo came up with an ingenious way of shielding a starship using only known and existing technology. The idea is to exploit the high velocity of a starship to annihilate everything in its way instead of letting the high velocity work against the starship.

You do this by continuously misting water in front of the starship so the droplets disintegrate everything in their way. After objects are disintegrated down to elementary particles, and conveniently ionized, it's a simple matter to almost instantly sweep them out of the way using an electromagnetic field. Particle accelerators do that all the time.

A 1 milliliter droplet of water going at 99% of light speed hits with the force of 31 tonnes of TNT. One tonne of water going at 99% of light speed hits with the force of 31 megatonnes of TNT. The most powerful nuclear bomb ever made had a yield of only 50 megatons (45 megatonnes).

Now, everyone knows the shape of electromagnetic fields, and most people can figure out from looking at a diagram of an electromagnet that the center of the electromagnet is unshielded. There are no field lines going through the exact center of any kind of magnet or electromagnet. They all cancel out there, so it's unprotected.

So if we want to maximize the amount of shielded volume in our starship, we're going to pick some kind of torus. Right away that looks very different from pretty much every depiction of starships in science fiction. But that's not all.

You can increase the volume of the starship without increasing its cross-section in its direction of travel (ie, what has to be shielded) by elongating it. And by some marvelous coincidence, when the starship is inside a solar system and in danger of getting crispy fried by its sun, that small cross-section also helps, as all you need to do is orient the starship towards the sun.

Incidentally, elongating the starship is also the answer to radiator fins. If you need radiator fins at all, then the best place to put them is down the long axis of the starship, probably in the middle. You put them anywhere else and they're likely to get ripped off. Also, radiator fins that don't catch sunlight are a really good idea.

It's unfortunate that you need strong structural supports to keep the front and back sections of the starships together with the radiator fins in between. Those structural supports have mass and so increase the size of the drive necessary to push the starship. But I can see no way of avoiding this ... unless the misting system is very lightweight. Which it very well might be.

Well, there you have the best possible shape for a starship. It looks like a tube. And if you don't need it to turn at all, better yet if you want to avoid it turning at all costs, then you just spin it. The gyroscopic forces will keep it steady. This also happens to generate gravity, not that computers and AI will ever care about gravity except as a bad thing to avoid at all costs.

And if you're thinking of Babylon 5 or other pathetic space operas where starships spin to generate gravity, you can get that right out of your mind. As a result of the spinning, any such starship is incapable of turning without tearing itself apart. Which is the same reason flywheels can't be used to store energy in automobiles.

No, if a starship ever spins, it's because it's expected to never, ever need to turn for any reason. So it's a good thing interstellar war is flatly impossible, isn't it? What with every space civilization deploying giant space mirrors to fry any incoming enemy vessels, and light up cities at night and during winter.

Starships can never wage war on each other or on any planets like they do in science fiction. Starships can't move like they do in science fiction. And starships can't even look like they do in science fiction. You see, science fiction is pretty much totally fucking useless. It's a wonder that people consider it to expand the mind.

I think the only worthwhile science fiction on television was probably Star Trek and Alien Nation. And that's because both explored the boundaries of humanity rather than get mired in the muck and the past.


dmbarbour said...

If the materials stress is tolerable, it is possible to pair flywheels so the moment of inertia is not externally observable: spin two wheels in opposite directions. Usefully, this can also allow a system to efficiently control its own orientation by shifting energy from one wheel to the other. The result is one wheel will have more energy than the other (and some extra materials stress), but the thrust requirement to restore the balance of energy while maintaining orientation could then be amortized.

Of course, flywheels aren't used in cars as a source of energy for many more reasons than moment of inertia.

dmbarbour said...

The best explanation of gyroscopic effect I've seen is gyroscopes demystified by Darel Rex Finley. This obviously suggests one could adjust angular moment efficiently with timed thrusts, based on the period of rotation. If the 'red circle' is only one quarter of an arc, we'll quickly achieve a change in orientation. (Potentially, one could also thrust on the opposite arc, in the opposite direction, to change orientation without affecting relative position.)

Richard Kulisz said...

Thanks for the link.