Project 7 Technology Assumptions, Part 1

I’m going to be taking a break from posting for the next week or so. I’m leaving you with a longuish post — feel free to comment, but please don’t burn down the house.

—-

The main goal of Project 7 is to see whether I can create a mecha-based setting with a very “hard” approach to the science involved. This means a minimum of technobabble, and nothing that violates the laws of physics as currently known: FTL or force fields are out, but fusion engines and nanobuilt diamondoid materials are in, for example. Story-wise, we want things to be interesting, so if at all possible I’ll pick technologies that let us do more interesting plots. Engines should have high enough thrust to allow days rather than months of travel, spacesuits should not need hours of pre-breathing before use, and so on. We also need to examine interactions to ensure that unexpected social ripples do not arise (e.a., if private citizens can buy a ship propelled by the equivalent of atom bombs, what happens?).

This said, let’s examine the major pieces of technology we’ll need to build our mecha and spacecraft. Many thanks to the crew of Atomic Rockets, whose work I used to make sure I didn’t forget anything. I was hoping to get around to the “war technologies” part today, but time is running out, so it will have to go in a “Part 2” entry later on.

Total Delta-V Capacity: in space, a vehicle’s Delta-V is effectively its range. Sure, you can coast to your destination, but orbital speeds still have to be paid for. Our vehicles will have to have engine(s) and enough propellant to manage delta-V of between 5 km/s (short-range craft) and 50-100 km/s (interplanetary ships). This is affected by the spacecraft’s Mass Ratio (loaded mass/empty mass) and the exhaust velocity of the engine; we want the former to be as low as possible (to maximize useful payload) and thus we need to maximize the latter (see Engines). This steers us toward high-energy propulsion systems, since a mecha full of fuel tanks would likely look like the Michelin Man.

Engines: I’m going to cheat a bit here and use a plasma engine with a variable thrust magnetic nozzle (kind of like the VASIMR engine, but more advanced). This means that I can get both high thrust/low endurance or low thrust/high endurance, out of the same package. It’s going to make calculating the range of my vehicles harder, but at least they won’t have to carry two different engine systems. It also means that I don’t have to deal with as much waste heat, since most of the fusion reaction will take place well outside the chamber walls. Lastly, by handwaving the nature of the plasma, I can use pretty much anything as reaction mass (hydrogen, methane, water — asteroid dust?) since it merely has to be dumped into the plasma flow — in-situ refueling will make for both longer range and interesting plots.

Structure: remember when I mentioned something about center of gravity? I still want to make that post; however, for the time being just know that we want the spacecraft to balance on its thrust vector, so it has to be fairly symmetrical. This also applies to mecha, so if I want one to carry a big massdriver on one shoulder, I’ll need to put something else on the other one. Ships won’t be a problem — all of my hard science design had a “skyscrapper” designs already, with decks stacked one above the others instead of length-wise like a naval ship.

I’m going to postulate that nano-assembly is possible (we’re already doing some basic stuff today), so the structure of my spacecraft is going to be extremely light yet extremely sturdy. No choice, really, if I want a decent mass ratio. Using nano-assembly also allows me to include all sorts of systems inside the structure itself.

Heat Radiators: this is something that’s always overlooked by designers. Vacuum is a great insulator (no conduction or convection possible), so spacecraft need a way to radiate excess heat away. Unfortunately, by their vary nature radiators can’t be armored, and they need to be fairly large (unless you want them to run at impossibly high temperatures). Fortunately for me, I chose a propulsion system that dumps most of the heat in the exhaust plume, so I don’t need to give butterfly wings to my mecha (though I did, once). Again I’m going to use a piece of “wiztech” and postulate the existence of nano-built, foldable sheet radiators: these will simply be retracted for combat or acceleration. I will also equip spacecraft with a way to vaporise reaction mass (plain old water, likely) as a way to get rid of additional heat in emergencies.

Comm Antennae: all spacecraft need those, of course. I was thinking of using large portions of the outer skin of the vehicles as receivers, since those can be built right in during the nano-fabrication process. We might yet still need dish antennae or some sort of landing radar, but these will be retractable.

Radiation Shielding: back when I wrote Jovian Chronicles I had no choice but to include a powerful type of “radiation screen.” It was the only way to establish a colony around Jupiter. I must admit that I did not think it all the way through — wouldn’t such a shield make all beam weapons useless? — so this time I’ll shoot for a more realistic approach (thus we’ll likely have to drop Jupiter from our list of destinations). The easiest way to go is to use the reaction mass tanks for basic shielding, so we’ll do that. Rad-bulkheads, made of complex organic and hydrocarbon compounds in a nano-fabricator, will stop most ionizing radiation if they are thick enough (and it also forces us to secure a good source of organics for the factories. Bonus plot seed!). Some sort of charged magnetic field would stop quite a few types of natural radiation, but might interfere with the engines.

Gravity: I don’t think there’s a realistic way to make a ship burn continuously at a good fraction of a gee, so we have a choice between no gravity and spinning, here. No problem — I’ve studied the problem for Jovian Chronicles, and the same solutions apply.

Controls: these will be a mix of traditional voice/touch/view controls and mind scanners for certain applications, such as directing the motions of certain parts of the ship/mecha. There will be a lot of pre-processing involved by the onboard computers to ensure that the crew aren’t overwhelmed by data.

More later in Part 2. I need to get some sleep.

Posted by vman at October 21, 2006 11:42 PM