Proper velocity the traveling object. It equals the object's momentum p divided by its rest mass "m", and is made up of the space-like components of the object's four-vector velocity. William Shurcliff's monograph mentioned its early use in the Sears and Brehme text. Fraundorf has explored its pedagogical value while Ungar, Baylis and Hestenes have examined its relevance from group theory and geometric algebra perspectives. Proper velocity is sometimes referred to as celerity. Unlike the more familiar coordinate velocity v, proper velocity is synchrony-free (does not require synchronized clocks) and is useful for describing both super-relativistic and sub-relativistic motion. Like coordinate velocity
Bussard ramjet to accelerate into the solar wind. However, in their calculations they assumed that: In the Zubrin/Andrews interplanetary ramjet design, they calculated that the drag force d/dt("mv") equals the mass of the scooped ions collected per second multiplied by the velocity of the scooped ions within the solar system relative to the ramscoop. The velocity of the (scooped) collected ions from the solar wind was assumed to be 500,000 m/s. The exhaust velocity of the ions when expelled by the ramjet was assumed not to exceed 100,000 m/s. The thrust of the ramjet d/dt("mv") was equal to the mass of ions