An Unkindness of Ravens Fink. When Wexford does a favour for his wife—to look into the disappearance of one of their neighbours' husbands—everything he finds seems to confirm his first inkling: that this is simply another case of a bored middle-aged man having run off with a younger woman. However, when Rodney Williams is found dead, and another local man is stabbed in his car, Wexford finds himself thrown into an investigation involving a militant feministic organisation known as "Arria", who have taken the raven as their symbol. An Unkindness of Ravens An Unkindness of Ravens is a novel by British crime-writer Ruth Rendell.
Specific impulse to impulse provided by external air that has been used for combustion and is exhausted with the spent propellant. Jet engines use outside air, and therefore have a much higher specific impulse than rocket engines. The specific impulse in terms of propellant mass spent has units of distance per time, which is an artificial velocity called the "effective exhaust velocity". This is higher than the "actual" exhaust velocity because the mass of the combustion air is not being accounted for. Actual and effective exhaust velocity are the same in rocket engines not utilizing air or other intake propellant such as