The RM-90 Blue Scout II was an American sounding rocket and expendable launch system which was flown three times during 1961. It was a member of the Scout family of rockets. Blue Scout II was a military version of the NASA-operated Scout X-1, with adjustments to the payload fairings, engine nozzles and fins. Blue Scout II had a total length of 21.65 m and a finspan of 2.84 m. It was capable of sending a 30 kg payload to a 300 km orbit at 28.00 degrees. It was a four stage vehicle, with the following engines: Blue Scout II was used for two HETS test flights, and the launch of the Mercury-Scout 1 satellite for NASA. This rocket and RM-89 Blue Scout I were replaced by Blue Scout Junior.

Blue Scout II parameters

Launches

All three Blue Scout II launches occurred from Launch Complex 18B at the Cape Canaveral Air Force Station, the same launch pad used for the Blue Scout I. The first two launches were successfully conducted on 3 March and 12 April 1961 respectively, using vehicles D-4 and D-5. They both carried HETS A2 plasma research experiments on suborbital trajectories. The third launch was conducted on 1 November, using vehicle D-8, with the Mercury-Scout 1 satellite for NASA, which was intended to reach low Earth orbit. The launch failed after the rocket went out of control, and was destroyed by the range safety officer 43 seconds after liftoff.