NASA'S SCOUT LAUNCH VEHICLE

On July 1, 1960, the first Solid Controlled Orbital Utility Test (Scout) vehicle was launched from the Mark 1 Launcher at NASA Goddard Space Flight Center's Wallops Flight Facility, Wallops Island, VA. Since then, Scout has carried more than 90 satellites into space and performed numerous reentry and probe missions.

Scheduled for launch no earlier than 1993, the last NASA Scout will lift off from Space Launch Complex Five (SLC-5), at the Western Test Range, Vandenberg Air Force Base, Lompoc, CA, marking the end of NASA's involvement in the Scout program.

America's first solid-fuel rocket, the four-stage Scout, manufactured by LTV Aerospace and Defense Company, Missile Division, Dallas, TX, was responsible for launching some interesting and varied payloads. The booster boasts an 88 percent success rate to date, with an impressive 96 percent success rate since December 1963.

Scout has delivered 92 satellites into orbit; including 20 Explorers, which have studied everything from the topside of Earth's ionosphere to X-rays from the Sun.

The 19 suborbital flights of probe and reentry Scout boosters revealed important data on items of interest to manned space flight, such as radio blackout and reentry heating.

In addition to NASA, U.S. Air Force and U.S. Navy payloads, Scout's clients include the European Space Research Organization as well as the governments of the Netherlands, France, Germany, Italy and the United Kingdom.

Scout's reliability can be tracked to its use of standardized launch of manufacturing procedures and the incorporation of off-the-shelf technology, according to project officials.

Unlike most of NASA's larger expendable rockets, the Scout is assembled and the payload is integrated and checked-out in the horizontal position. The vehicle is raised to the vertical orientation prior to launch.

Scout's first-stage motor was based on an earlier version of the Navy's Polaris missile motor; the second-stage motor was developed from the Army's Sergeant surface-to-surface missile; and the third- and fourth-stage motors were adapted by NASA's Langley Research Center; Hampton, VA, from the Navy's Vanguard missile.

The standard Scout launch vehicle is a solid propellant, four-stage booster system, approximately 75 feet (23 meters) in length with a launch weight of 47,398 pounds (21,500 kilograms.)

Propulsion Systems

When the countdown for a Scout launch reaches zero, the Scout's Algol IIIA first-stage motor ignites. Manufactured by United Technologies Corporation/Chemical Systems Division, Sunnyvale, CA, the Algol IIIA combines a steel motor case with a lightweight reinforced plastic nozzle.

Approximately 90 seconds later, at an altitude of about 24 nautical miles (44 kilometers), stage-two blast pressure jettisons the first stage.

Second-stage thrust is supplied by the Castor IIA motor, manufactured by Thiokol Corporation, Huntsville, AL. The Castor IIA motor has a steel case and nozzle containing a graphite throat insert.

Stage three ignites at approximately 56 miles (90 kilometers) altitude and approximately 2 minutes and 16 seconds into flight. The Antares IIIA motor drives the third stage. The Antares IIIA, manufactured by Thiokol's Elkton Division, Elkton, MD, incorporates a Kevlar and epoxy composite case. The motor's nozzle uses a 4D carbon/carbon throat insert, a carbon-phenolic exit cone and a titanium housing. A nominal burn for Antares IIIA lasts about 48.4 seconds.

Approximately 10 minutes after lift-off, stages three and four are given a spin rate of 120-180 revolutions-per-minute. Stage three then separates and performs a retromaneuver to move safely out of stage four's path. Once stage three is clear, the fourth stage's Altair IIIA/Star 20 rocket motor, manufactured by Thiokol's Elkton Division, ignite and burn for about 30 seconds.

Fifteen minutes after lift-off, Scout delivers its payload into orbit. Scout is capable of delivering a 385 pound (174.6-kilogram) payload to a 500-mile (805-kilometer) Earth orbit.

Guidance and Control

The Scout guidance and control system provides attitude reference as well as the control signals and forces necessary to stabilize the vehicle in the pitch, yaw and roll axes.

Miniature rate gyros, contained within the inertial reference package, detect any deviation from the vehicle's programmed path and generate electronic signals. These signals, along with rate-of-movement information, are then fed to the appropriate stage control system.

The first-stage stabilization is controlled by four fins containing moveable jet vane/fin-tip assemblies. These assemblies act as tiny thrusters for the Scout.

Stabilization of the second and third stages is controlled by mono-propellant reaction control systems while the fourth stage is spin stabilized.

Stage Separation

The four solid propellant motors of the Scout are joined by interstage structures called transition sections. "Blow-out" diaphragms join the first and second and the second and third stages. The diaphragm forms an internal clamp that engages two threaded rings around the inside perimeter of the transition section at the separation plane. Blast pressure of the upper stage motor ruptures the diaphragm and disengages the internal clamp, thus allowing the stages to separate.

The third and fourth stages are joined by a four-piece, V-groove separation clamp on the separation plane. When the explosive bolts holding the clamp together are fired, energy stored in spring-loaded plunger assemblies located on the separation plane force the separation of these stages.

The Scout program is managed by Goddard's Orbital Launch Services project for NASA's Office of Space Science and Applications. From April 1959 to January 1991, Scout was managed by NASA's Langley Research Center, Scout Project Office.