Single stage. Launched 12 March 1959 at 20:20. Apogee 334 miles. No re-entry head.

BK03 was the second proving trial, and was successful except for an engine malfunction late in flight resulting in a long period of ‘cold’ thrusting (that is, decomposition of HTP in the absence of kerosene). The fault was subsequently traced to excessive heating of the propulsion bay, in which temperatures were measured during flight.

Control of the vehicle was satisfactory both during ‘hot’ burning and ‘cold’ burning. In this trial, the guidance telescope tracking was made the primary source of information and radar tracking was retained as the stand-by; this proved very successful. Very good tracking information was received until engine flameout, after which radar information was used during ‘cold’ burning.