Fifty-years ago this week, the NASA SCOUT small launch vehicle successfully orbited the Explorer IX satellite. This achievement marked the first time that an all-solid propellant launch vehicle orbited an artificial satellite.
The concept for the Solid Controlled Orbital Utility Test (SCOUT) launch vehicle dates back to the late 1950’s. The National Advisory Committee For Aeronautics (NACA) saw a need to develop a simple, low-cost launch vehicle for boosting small science payloads into space. Propulsion units for each stage would be selected from the existing inventory of solid rocket motors.
In the same time period, the United States Air Force (USAF) was moving toward the development of a small launch vehicle (SLV) to support a variety of suborbital and orbital military missions. The junior service subsequently partnered with the recently established National Aeronautics and Space Administration (NASA) in March of 1959 to develop a “poor man’s rocket.”
The SCOUT SLV was a 4-stage, all-solid propellant launch vehicle that stood roughly 75-feet in height. The initial version of the vehicle was designed to put a 130-lb payload into a 115 nm circular Earth orbit. The payload capacity of later versions approached 500 lbs. A fifth stage could be added to provide greater velocity performance for missions involving reentry vehicle research, highly elliptical orbits and solar probes.
The original SCOUT propulsion stack consisted of an Algol 1st stage (105,000 lbs thrust), Castor 2nd stage (64,300 lbs thrust), Antares 3rd stage (13,500 lbs thrust) and an Altair 4th stage (3,000 lbs thrust). Many variants of the SCOUT were developed over the program’s life time as the demand increased for higher payload capability. These variants were primarily the result of rocket motor thrust-level upgrades.
A compelling aspect of the SCOUT SLV was the fact that its launch support infrastructure was less involved that the bigger liquid-fueled launch vehicles such as Atlas, Delta and Titan. SCOUT was launched from at least three (3) separate sites; Wallops Island, VA, Vandenberg AFB, CA and San Marco Island just off the coast of Kenya. The latter pair of launch locations supported polar and equatorial orbit missions, respectively.
SCOUT developmental test flights began in April of 1960. The first ten (10) test flights included four (4) orbital attempts. The only successful orbital mission was that flown on Thursday, 16 February 1961 with launch taking place from LA-3 at the Wallops Flight Facility (WFF). The Explorer IX payload was successfully placed into orbit where it was used to study the density and composition of the upper thermosphere and lower exosphere. This mission also marked the first time that a satellite had been orbited from WFF.
While NASA’s SCOUT SLV program lasted more than three (3) decades and was very successful, USAF’s experience with the vehicle was quite different. Under the code names Blue SCOUT and Blue SCOUT Junior, the service employed variants of the basic SCOUT SLV for military missions. Hardware reliability issues and inter-organizational disconnects with NASA led to the USAF SCOUT SLV program being ended in 1967.
The NASA SCOUT SLV was flown 116 times between 1960 and 1994. Of that total, the break-out between research and development (R&D) flights and operational missions was 21 and 95, respectively. Parenthetically, it must be noted that the variety of space payloads launched by SCOUT is a story in itself. (One that must be told another day.) Suffice it to say here that SCOUT was a workhorse launch vehicle for NASA and contributed mightily to the scientific exploration of both near and deep space.