In space, the horizon assumption is almost always wrong. The one exception is Low Earth Orbit (LEO), where the limb of the earth can temporarily obscure something for roughly an eighth of an orbital period; this is about a 15-minute window, tops. Detection range is never limited by terrain for militarily significant increments of time.Not true for sufficiently distant observers. For an observer on Mars or Ceres, a ship in LEO is going to be eclipsed almost half an orbital period. In a hostile environment, this is exactly when the Earth ship would choose to make major delta-v changes.
With an emissions spectrum on your drive flare, plus distance and proper motion, they can determine the mass pushed by that drive flare. Making your spacebattleship look like a space rowboat doesn't work, and neither do decoys, which need the same drive signature, apparent motion, and mass as the ship they're duplicating.You can’t make a battleship look like a rowboat, but you can make a rowboat look like a battleship. A rocket engine is designed to convert as much of the energy used as possible into accelerating propellant. A mechanism designed to simply produce the same amount of heat and lighter will be lighter, simpler, cheaper and use less energy. Compare, for example a welding torch to a rocket engine with the same thermal output. Similarly, a craft with electric propulsion could route electricity directly to radiators to simulate the heat signature of a much more massive craft.
The usual counter-argument made is "I'll just drift in, with engines cold and go undetected." Your life support system and power plant will be a detectable signal once your engine turns off, and they'll know where to look.Again, a decoy can have a heat source to simulate a manned ship running without thrust. And unmanned ships can hibernate while not under thrust, with very low power output. We’ve already shown that unmanned craft can be lethal weapons platforms, even when operating in the unpredictable environment of an atmosphere with weather.
The ion thrusters used by NASA's probes to Pluto have ISPs of around 10,000 seconds with a thrust of around 4milligees.NASA’s one probe to Pluto, New Horizons, does not use ion thrusters. The author is evidently thinking of Deep Space 1 and Dawn, both asteroid missions.
The combat actions won't be naval in nature, at least in the conventional Battleof Jutland sense. They'll be closer to anti-piracy actions in the Sea of Cebu or the Gulf of Aden; a pirate will lay in wait at a point where a ship must make a course correction – and where missing that correction by a few hours can result in everyone aboard dying of starvation – and capture the ship to hold for ransom.This shows a profound misunderstanding of orbital mechanics. First, most cargo missions won’t need a crew and won’t have one. Second, capturing a ship at interplanetary speeds is much easier said than done.
Consider a specific scenario: the asteroid pirates in Poul Anderson’s 1966 The Moonrakers. Robot freighters travel on Hohmann Orbits between Mars and the Jovian Moons, and space pirates from the asteroids match courses and loot them as they pass through the asteroid belt. There are several problems with this concept.
Simply matching courses takes a lot of delta-v, even if the most efficient course is chosen, and the most efficient course is a very long haul for the pirate crew. Getting away with the loot requires still more delta-v, and another long haul for the pirate crew. For most goods, it’s probably cheaper to buy honestly in Mars orbit and ship to the belt on a robot freighter.
Second, if Burnside is correct that plausible space drives are visible at great distances, it will be quite difficult for the pirates to either achieve surprise or get away without being tracked and targeted.
Third, reliably disabling enough of the freighter’s systems to make it safe to board without damaging the cargo will be tricky, even if the pirates can achieve surprise. And I can imagine a lot of ways a bloody-minded owner could booby trap a ship so that unauthorized boarding becomes too risky for any rational pirate.