2013-09-09

09-09-2013: BSinSF - Thermodynamics, the bane of science fiction

Before I get into the meat of this week's post I would like to give you a brief update on some other items. Firstly, I'd like to remind everyone of the soon-to-be-released Launch Pad anthology. It's filled with short stories from the Launch Pad 2012 attendees. Next, you will be happy to know that my wife is nearly finished with her grammatical review and I've started my final pass through the manuscript. My wife will have to make sure I didn't screw things up with the changes I'm making and then the book will be ready for release. I recently received a possible cover and the designer is working on making some requested changes. It's beginning to come together folks.

This week's BSinSF topic is on thermodynamics; it's the bane of science fiction in my book. Nothing is 100% efficient and most of the loss in efficiency shows up as heat. A perfect example is something I deal with every day—power production. Nearly every large power plant has a cooling tower and all that vapor pouring out the top is waste heat. How much? About 65% of the energy generated in the reactor or boiler! This waste heat creates a MAJOR problem for science fiction. In order to understand why, let's take a step back and talk about heat transfer for a moment.

Heat can be transferred in three ways: convection, conduction, and radiation. Convection and conduction require the heat source to be in physical contact with the transfer medium. A spacecraft is isolated from everything else by the vacuum of space which rules out both of these as a means of dumping waste heat. That leaves radiation, which is the transfer of heat through the emission of electromagnetic radiation. This means that if you want to keep your ship cool you need large radiators to dump the excess heat.

If you look at a picture of the International Space Station (ISS), the first thing you will most likely notice are the huge panels extending away from the primary truss. The largest of these are the solar panels that provide the station with electricity. The others are the heat radiators. Damage enough of these and the station will quickly become uninhabitable. Ever wonder why the space shuttle kept its cargo doors open the entire time it was in space? Because the inside of the doors served as heat radiators to keep the shuttle cool. If you're building a nuclear powered warship equipped with directed energy weapons, you're going to have to get rid of a tremendous amount of waste heat. To do that, you'll need a heat radiator with a very large surface area. Now you have a problem.

Take a close look at any science fiction movie ever made and try to point out the heat radiators. I'll bet you won't find any. The starship Enterprise would look pretty silly if you tacked on enough heat radiators to keep the ship's internal temperature within limits. To be honest, I never considered this problem until I started reading the articles on the Project Rho website. I took a stab at a possible solution in When Ships Mutiny by explaining that the entire ship's external hull was designed to be an efficient heat radiator. But I'm sure it wasn't enough.

If you want to write science fiction that is based 100% on known science then your incredibly powerful, massively armored warships are going to have to be equipped with extremely large arrays of heat radiators. If these are damaged or shot off you're warship becomes useless. Temperatures on the inside will quickly rise and your fusion reactor will end up turning your ship into a molten blob.

Even if you make the claim that your ship's power systems are 99% efficient you will still have to deal with the waste heat problem. Heat dissipation by radiation is very inefficient; that's why thermos bottles use a vacuum as an insulator. If your ship's main reactor generates 1,000 megawatts of power then you're impossibly efficient system will still have to find a way to get rid of 10 megawatts of waste heat.

If you're a math nerd and you want to find out just how bad this problem is, I invite you to do some research into thermodynamics. I could have run the numbers years ago when I learned about heat transfer and fluid flow in the Navy's nuclear power school but many years have passed and I simply don't have the time to learn about things like black-body radiation. The math isn't terrible difficult but you need to have a thorough understanding of thermodynamics to get the numbers right.

If you do read the associated articles on the Project Rho website you'll also discover that the heat problem also means that stealth in space (i.e. cloaking fields, stealth ships, etc.) are pretty much impossible. Sorry, the Klingon and Romulan cloaking devices simply aren't possible.

So what's the solution? Actually, in this case the only possible solution is to ignore the problem. That's right—I said ignore it. Until someone comes up with a way to dump excess heat into space without the use of large surface-area heat radiators then you're just going to have to sweep the problem under the rug and hope nobody asks how your ships deal with waste heat.


Next week I'll be tackling a pet peeve of mine by asking: Why do things in science fiction movies glow, pulsate, or generate light? Why do they hum, scream, or make sounds?

PS--This post was late because I got stuck working 12-hour nights at the plant. That doesn't leave much time for anything other than work and sleep.