[xv] Controversy often surrounds the conversion of the Cyrillic characters used in the Russian language into the Roman letters used in English. In the absence of a universally accepted standard, we have transliterated Russian personal and place names after the pattern established by the Soviets themselves and as recorded in the English language version of the ASTP documents.
The metric system poses an equally thorny problem. NASA is committed to the national goal of metrication, and in 1973 the space agency prohibited the use of English weights and measures in all publications, including its historical series. But NASA engineers were not thinking metric all the time. ASTP documents often recorded specifications in metric form, but they almost always added the English equivalent. Furthermore, the actual production of the American components for the joint mission was done on manufacturing tooling calibrated in standard American engineering units. As some passages in the text indicate, this English metric schizophrenia caused occasional troublesome moments when the switch from metric drawings to English tooling required extra care to determine that all the critical dimensions were correct. In this history we have followed the trend to metrication, and we have used the systeme internationale d'unites (SI) with one major exception. We have chosen millimeters of mercury to designate cabin pressures. The Soviet space community has commonly used this measurement, while their American counterparts have used pounds per square inch (psi). Neither side talked in pascals (newtons per square meter), the approved SI measurement, which would have puzzled nearly everyone who worked on ASTP.
Another metric unit requires explanation. In
the English system, "pound" is used to describe both mass and force.
The creators of the metric system devised two distinct units, the
familiar gram for mass and the less familiar newton for force - thus
pounds of weight become grams, but pounds of thrust become newtons.
Where we wrote about thrust, we used both newtons and the equivalent
in pounds. Elsewhere, we have given only the metric units to keep
from cluttering the pages with endless conversions in parentheses.