The RM-90 Blue Scout II was an American sounding rocket and expendable launch system which was flown three times during 1961.

[1][3] 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.

Blue Scout II was used for two HETS test flights, and the launch of the Mercury-Scout 1 satellite for NASA.

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.

[6] The launch failed after the rocket went out of control, and was destroyed by the range safety officer 43 seconds after liftoff.