SCORPION program

The SCORPION (Self CORrecting Projectile for Infantry OperatioN) program was a research initiative led by the U.S. Army Research Laboratory (ARL), the U.S. Defense Advanced Research Projects Agency (DARPA), and the Georgia Institute of Technology to integrate Micro Adaptive Flow Control (MAFC) technology into small caliber munitions to develop spinning, guided projectiles. The program led to the creation of a spin-stabilized 40mm grenade, also called SCORPION, that could propel itself to its target by using calculated micro-jet bursts of air to correct its path once launched.

History

The SCORPION program began in 2001 as a joint venture between DARPA, Georgia Tech Research Institute, and ARL’s Weapons and Materials Research Directorate in order to improve the precision of small to medium-sized munitions in complex, dynamic environments.

Micro adaptive flow control is largely defined by the active manipulation of aerodynamic flows using small time-dependent actuators in carefully chosen locations. By taking advantage of flow instabilities, the system can generate large amounts of energy from using only a small fraction of the overall flow if the actuators and their activity are properly assigned. As a result, MAFC can enable low power yet highly distributed redundant actuation systems in contrast to flow systems that utilize steady blowing where high velocity flows must be provided through complex and high-loss ducting.The project was spearheaded by the proposition that MAFC and advanced microtechnology could be combined to establish closed loop guidance of a projectile, demonstrating more effective flight control and steering capabilities.

The program was divided into two phases, Phase I and Phase II. The former focused on constructing the flight control system and determining whether MAFC could be integrated into a 40 mm round to provide adequate guidance to its target, while the latter prioritized determining whether MAFC technology could be used to steer projectiles that were smaller and even faster than those used in Phase I. By 2005, Phase I had been completed, and the SCORPION program was chosen as a DARPA demonstration program in order to further investigate the use of MAFC in high-velocity, small-diameter projectiles.

The SCORPION program concluded in 2007 after successfully demonstrating the use of MCFA to maneuver a 40 mm rifle-launched grenade. In 2009, ARL researchers at White Sands Missile Range, New Mexico tested the renamed XM1100 Scorpion networked sensor and munitions platform and achieved what they called a “mobility kill” for the first time, highlighting the system’s ability to identify and track its targets. According to the researchers, the XM1100 Scorpion successfully demonstrated all of its major functions, including command and control, ground sensor tracking, target engagement, anti-vehicle munitions launch, warhead lethality, and self-destruction. (8) If successful in the government development testing phase, the Pentagon has displayed interest in utilizing the munition system for long-range combat in urban environments.

Projectile Design

Designed to be fired from the M203 grenade launcher, the SCORPION projectile is a 40 mm grenade that was based on the M781BT practice grenade. Due to how 40 mm grenades are spin stabilized and have highly nonlinear aerodynamics, researchers undergone several tests to understand the aerodynamic nonlinearities and flight dynamics of the projectile’s trajectory. Experiments with the base model has shown that these projectiles exhibit fast and slow mode angular precession, meaning that the aerodynamic control system must not only deal with a spin rate of 60 Hz, but also account for the nonlinear response of the round. Both the rotational motion and the precession of the projectile served to greatly complicate how the projectile respond to control forces.

The SCORPION projectile features a telemetry system based on the Army Research Laboratory’s diagnostic fuze (DFuze), a high-g, projectile-based sensor system that measures inflight ballistic data. Used primarily to determine the projectile flight dynamics along the trajectory, the telemetry system consists of four radial accelerometers, a three-axis magnetometer, an axial accelerometer, a two-axis accelerometer for transverse acceleration, and a suite of four Yawsondes. While the magnetometers serve to measure the SCORPION’s projectile orientation and roll angle to the earth’s magnetic field, the Yawsondes measure its projectile angular orientation to the sun. Through the use of the magnetometers and the Yawsondes, the angular state of the projectile can be identified. The accelerometers help measure the accelerations of the SCORPION in the x, y, and z directions, and an encoder board is present inside the projectile to collect the sensor data and send it to the ground station.

As a result of its telemetry system, the researchers can monitor the forces on the SCORPION as it flies to its target. However, in order to control its flight path, the projectile employ MAFC through the use of tiny synthetic jets embedded on the surface of the projectile. Developed by researchers at the Georgia Institute of Technology, these synthetic jet actuators are designed to fire bursts of air to alter the flow field and pressure distributions of the surrounding air. When turned on momentarily, these synthetic jets use those tiny, short bursts to correct the trajectory of the projectile as it travels towards its target.

As active control devices with zero net mass flux, the synthetic jets produce the desired amount of control of the flow field through momentum effects. They act as steering devices for the projectile, using a minute-vibrating diaphragm-like system powered by piezoceramic elements. Due to the tiny air vortices created by the synthetic jets, an asymmetry in the airflow can be created around the projectile. In addition, the resulting Coanda effect can multiply this effects of this phenomenon, producing air flow changes that are strong enough to change the projectile’s trajectory. The SCORPION’s electronics have also undergone g-hardening to withstand the heavy forces generated during each launch.

However, issues still remain with this design. The SCORPION projectile lacks sufficient payload room for a full guidance system as well as a greater explosive power. As a result, researchers have investigated using gas-generator actuators, which employ miniature explosive charges to create stronger steering forces and allow the projectile to travel faster in the air.

In addition to the 40 mm SCORPION, a 25 mm SCORPION has also been developed. Designed similarly to the 40 mm model, it features two axes of rate sensors, three aces of accelerometers, three axes of magnetometers, and two additional radially oriented accelerometers. The 25 mm SCORPION is comprised of two sections, the electronics control module and the actuator module. This divide serves to prevent potentially hazardous material like the propellant from interacting with the control electronics until just prior to firing. According to flight experiments conducted at the Army Research Laboratory, the 25 mm SCORPION successfully established the charge weight needed to meet the velocity requirements when launched at 0.8 Mach.