Throughout this book, all measurements are given in both metric units and US customary units. Unless otherwise specified, mile is understood to reference a statute mile and ton is understood to be a metric ton (1,000 kg). Some rounding may be introduced to avoid unnecessarily pedantic conversion results; e.g., 100,000 feet will be converted to 30,000 meters instead of 30,480. Also, idiomatic expressions such as a couple of inches or a few feet, which suggest a very approximate measurement, will not be converted.
This book uses non-gender specific terms, such as crewed and crewless rather than manned and unmanned, except for names of buildings and programs, in accordance with the NASA History Program Office Style Guide:
In general, all references to the space program should be non-gender-specific (e.g., human, piloted, unpiloted, robotic, as opposed to manned or unmanned). The exception to the rule is when referring to the Manned Spaceflight Center (also known as the Manned Spacecraft Center), the predecessor of Johnson Space Center in Houston, or to any other historical program name or official title that included “manned” (e.g., Associate Administrator for Manned Spaceflight).
Although I’m half British, I’ve used US English rules in this book because I know that otherwise I’ll get heaps of mail complaining about my “misspelling” of colour, metre, tranquillity and so on. Brits, instead, will cringe and bear politely.