1. Sound-and-flash ranging and other early techniques are summarized in U.S. Department of Defense (1996).

2. The gyro gun sight shown in figure 6.1 was manufactured in Edinburgh, Scotland, from 1943 on at the facility where, 40 years later, your author would begin his career in aerospace.

3. Fighter planes of this period were formidably armed. A Spitfire in the Battle of Britain was sent aloft with eight 30-caliber machine guns, four in each wing; a P-51 Mustang later in the war would have either four or six 50-caliber machine guns. As a physicist I wonder about the recoil effects of all this firepower on airframe speed.

4. “Drift” in this chapter refers to crosswind drift and not to the drift resulting from a spinning projectile as discussed in chapter 5. Early bomb-aiming devices are discussed in Baden (1961, chap. 1).

5. The British and Germans also had sophisticated tachometric bomb-aiming devices during the latter stages of World War II.

6. See Ross (2002) for an account of U.S. bombing efficacy.

7. We might regard dive bombers as guidance systems that controlled 80% of the bomb’s trajectory, leaving only the final 20% as an unguided ballistic trajectory. Japanese kamikaze planes were, in essence, manned guided missiles.

8. The Congreve rocket also played an important part in the Battle of Leipzig in 1813, and a year later against the Americans in the Battle of Bladensburg, outside Washington, DC.

9. The name came from its resemblance to the musical instrument. The idea behind bazookas came from Goddard during World War I. See Hacker (2006, pp. 98–100).

10. Solid-propellant rockets were less accurate than liquid-propellant rockets because of irregularities in the fuel, which led to an inconsistent burn and erratic flight. For a good introductory account to the evolution of rockets, see Van Riper (2007).

11. This figure is readily calculated from a knowledge of muzzle speed and barrel length, plus a few reasonable assumptions.

12. Here I am referring to the speed of the shell when it hits its target and the speed of a rocket hitting the same target. I assume that the rocket runs out of fuel at this instant. For ballistic missiles this is a reasonable assumption. Many guided missiles, however, operate on a boost-coast strategy: they run out of fuel before reaching their target and coast the rest of the way. This extends range and enhances maneuverability because with no fuel, the rocket is lighter and easier to maneuver. You’ll find more on guided missiles in the last section of this chapter.

13. To a radar systems engineer, “illuminate” means to reflect energy from the target (in this case laser beam energy); it does not mean that the target is lit up by laser light. (In a radar context, it may mean to bathe the entire target in microwaves, which then reflect back to the radar receiver.) A more colloquial term meaning the same thing is to “paint” the target. The choice of microwave (radar) or IR/optical (laser) for the illuminating beam frequency is not always obvious. Laser beams are narrower, permitting greater accuracy, but unlike microwaves they are susceptible to scattering and attenuation by fog, clouds, or rain.