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Hypervelocity Impact Testing
Millions of man-made debris and naturally occurring micrometeoroids orbit in and around Earth's space environment at hypervelocity averaging 10 km/s (22,000 mph).
This "space junk" collides with spacecraft and satellites. Collision with these particles can cause serious damage or catastrophic failure to spacecraft or satellites and is a life threatening risk to astronauts conducting extra-vehicular activities in space.
WSTF's Remote Hypervelocity Test Laboratory (RHTL) simulates debris impacts on shields, spacecraft and satellite materials or components, and spacesuit assemblies using two-stage light gas gun launchers.
The WSTF RHTL is a remote, access-controlled hazardous test area and is designed to safely handle and test hazardous targets, making it a unique NASA facility.
Orbital Debris and Micrometeoroids
Debris hits spacecraft and satellites. To minimize the potential hazard of debris impacts, it is necessary to understand the current orbital debris environment.
Orbital debris in the near-Earth space environment is made up of micrometeoroids and man-made debris. The man-made debris or space junk consists mainly of fragmented rocket bodies and spacecraft parts created by 50 years of space exploration. These objects number in the millions and orbit the earth at hypervelocities averaging 10 km/s (22,000 mph).
The orbital debris environment is growing. More satellites are being launched, and with non-functioning satellite explosions and fragmentation, the threat of debris impact damage on active satellites and spacecraft is a major concern. Orbital debris remains in orbit a long time, and high-speed collisions between existing particles can produce even more debris.
Larger particles (objects greater than 10-cm in diameter) are being tracked and catalogued by USSPACECOM radar. Spacecraft and satellites can avoid collisions by maneuvering around the larger debris. For example, when a space shuttle is in orbit, the USSPACECOM regularly examines the trajectories of orbital debris to identify possible close encounters. If a catalogued object is projected to come within a few kilometers of the space shuttle, it will normally maneuver away from the object.
Particles less than 1 mm in diameter are not tracked by radar. Fortunately, small particles pose less of a catastrophic threat, but they do cause surface abrasions and microscopic holes to spacecraft and satellites.
The greatest challenge is medium size particles (objects with a diameter between 1 mm to 10 cm), because they are not easily tracked and are large enough to cause catastrophic damage to spacecraft and satellites.
Spacecraft must be designed to withstand hypervelocity impacts by untrackable particles. Conducting hypervelocity impacts on spacecraft and satellite components assesses the risk of orbital debris impacting operating spacecraft and satellites. Developing new materials and designs from HVI impact data provides a better understanding to protect spacecraft and satellites from the debris in the space environment.
One recently developed concept of spacecraft shielding, termed multishock, uses several layers of lightweight ceramic fabric to act as "bumpers," which repeatedly shock a projectile to such high energy levels that it melts or vaporizes before it can penetrate a spacecraft's walls. Lightweight shields based on this concept are used on the International Space Station (ISS).
Spacecraft Shielding with Multishock Bumpers
The ISS is the most heavily shielded spacecraft ever flown. Critical components such as habitable compartments and high-pressure tanks will be able to withstand the impact of debris as large as 1 cm in diameter. The ISS will also have the capability of maneuvering to avoid tracked objects.
HVI Facility Capabilities
WSTF's RHTL is an access-controlled hazardous test area capable of simulating micrometeoroid and orbital-debris impacts on spacecraft materials and components. The facility was designed to safely handle and test hazardous targets. Four two-stage light gas guns (2SLGGs) propel 0.05 mm to 22.2 mm diameter projectiles to velocities in excess of 7.5 km/s. Because of WSTF's remote location and attention to safety, the HVI test facility is capable of implementing test programs that propel projectiles at toxic or explosive materials and components such as batteries, aerospace fluids, and pressurized containers in a controlled laboratory environment.
WSTF HVI Two-Stage Light Gas Gun Launcher Facility
Two-Stage Light Gas Guns
Most modern rifles are limited to velocities below 2 km/s (4,500 mi/h). WSTF HVI two-stage light gas gun launchers use highly compressed hydrogen to accelerate projectiles at velocities in excess of 7.5 km/s (16,800 mi/h). These velocities simulate impacts of particles on spacecraft and satellite materials and components.
Light Gas Gun Schematic
The two-stage light gas gun uses conventional smokeless gunpowder as its first stage. The second-stage propellant is a highly compressible light gas such as hydrogen. The gunpowder is set off by an electronic igniter, and provides rapidly expanding gas that drives the plastic piston forward. The pump tube contains the hydrogen gas which is compressed rapidly by the piston. The hydrogen gas provides the second-stage firing power. In the high pressure coupling section, rapid internal pressurization is followed by a high level of impact caused by the halted piston. The hydrogen gas and launch package are separated by a burst disc. The launch package, sabot, and projectile are located at the beginning of the barrel, just downrange of the burst disc. The pressure in the chambers, like space, is near vacuum. When the pressure in the pump tube becomes sufficiently high, the burst disc fails, releasing the hydrogen gas at very high pressure into the back of the launch package. The launch package is propelled down the barrel into the expansion tank. The expansion tank allows collection and dissipation of high pressure hydrogen gas and permits the controlled separation of the sabot/projectile assembly.
The projectile is photographed with high-speed cameras and flash x-rays just before impact. At times, the impacts are photographed to characterize the debris cloud. Three types of high-speed cameras are used. Cinema cameras run at 10,000 frames per second, 35-mm infrared cameras are capable of 2 million, and the digital cameras are capable of 200 million frames per second.
Laser intervalometers measure projectile velocity. The time difference between interruption of laser beams by the projectile yield an extremely accurate calculation of its velocity. In addition, high-speed data acquisition systems using light detectors, strain gauges, pressure transducers, accelerometers, and thermocouples provide reliable diagnostics.
For additional information, contact Karen Rodriguez at (575) 524-5723 or karen.m.rodriguez@nasa.gov.
This "space junk" collides with spacecraft and satellites. Collision with these particles can cause serious damage or catastrophic failure to spacecraft or satellites and is a life threatening risk to astronauts conducting extra-vehicular activities in space.
WSTF's Remote Hypervelocity Test Laboratory (RHTL) simulates debris impacts on shields, spacecraft and satellite materials or components, and spacesuit assemblies using two-stage light gas gun launchers.
The WSTF RHTL is a remote, access-controlled hazardous test area and is designed to safely handle and test hazardous targets, making it a unique NASA facility.
Orbital Debris and Micrometeoroids
Debris hits spacecraft and satellites. To minimize the potential hazard of debris impacts, it is necessary to understand the current orbital debris environment.
Orbital debris in the near-Earth space environment is made up of micrometeoroids and man-made debris. The man-made debris or space junk consists mainly of fragmented rocket bodies and spacecraft parts created by 50 years of space exploration. These objects number in the millions and orbit the earth at hypervelocities averaging 10 km/s (22,000 mph).
The orbital debris environment is growing. More satellites are being launched, and with non-functioning satellite explosions and fragmentation, the threat of debris impact damage on active satellites and spacecraft is a major concern. Orbital debris remains in orbit a long time, and high-speed collisions between existing particles can produce even more debris.
Larger particles (objects greater than 10-cm in diameter) are being tracked and catalogued by USSPACECOM radar. Spacecraft and satellites can avoid collisions by maneuvering around the larger debris. For example, when a space shuttle is in orbit, the USSPACECOM regularly examines the trajectories of orbital debris to identify possible close encounters. If a catalogued object is projected to come within a few kilometers of the space shuttle, it will normally maneuver away from the object.
Particles less than 1 mm in diameter are not tracked by radar. Fortunately, small particles pose less of a catastrophic threat, but they do cause surface abrasions and microscopic holes to spacecraft and satellites.
The greatest challenge is medium size particles (objects with a diameter between 1 mm to 10 cm), because they are not easily tracked and are large enough to cause catastrophic damage to spacecraft and satellites.
Spacecraft must be designed to withstand hypervelocity impacts by untrackable particles. Conducting hypervelocity impacts on spacecraft and satellite components assesses the risk of orbital debris impacting operating spacecraft and satellites. Developing new materials and designs from HVI impact data provides a better understanding to protect spacecraft and satellites from the debris in the space environment.
One recently developed concept of spacecraft shielding, termed multishock, uses several layers of lightweight ceramic fabric to act as "bumpers," which repeatedly shock a projectile to such high energy levels that it melts or vaporizes before it can penetrate a spacecraft's walls. Lightweight shields based on this concept are used on the International Space Station (ISS).
The ISS is the most heavily shielded spacecraft ever flown. Critical components such as habitable compartments and high-pressure tanks will be able to withstand the impact of debris as large as 1 cm in diameter. The ISS will also have the capability of maneuvering to avoid tracked objects.
HVI Facility Capabilities
WSTF's RHTL is an access-controlled hazardous test area capable of simulating micrometeoroid and orbital-debris impacts on spacecraft materials and components. The facility was designed to safely handle and test hazardous targets. Four two-stage light gas guns (2SLGGs) propel 0.05 mm to 22.2 mm diameter projectiles to velocities in excess of 7.5 km/s. Because of WSTF's remote location and attention to safety, the HVI test facility is capable of implementing test programs that propel projectiles at toxic or explosive materials and components such as batteries, aerospace fluids, and pressurized containers in a controlled laboratory environment.
Two-Stage Light Gas Guns
Most modern rifles are limited to velocities below 2 km/s (4,500 mi/h). WSTF HVI two-stage light gas gun launchers use highly compressed hydrogen to accelerate projectiles at velocities in excess of 7.5 km/s (16,800 mi/h). These velocities simulate impacts of particles on spacecraft and satellite materials and components.
The two-stage light gas gun uses conventional smokeless gunpowder as its first stage. The second-stage propellant is a highly compressible light gas such as hydrogen. The gunpowder is set off by an electronic igniter, and provides rapidly expanding gas that drives the plastic piston forward. The pump tube contains the hydrogen gas which is compressed rapidly by the piston. The hydrogen gas provides the second-stage firing power. In the high pressure coupling section, rapid internal pressurization is followed by a high level of impact caused by the halted piston. The hydrogen gas and launch package are separated by a burst disc. The launch package, sabot, and projectile are located at the beginning of the barrel, just downrange of the burst disc. The pressure in the chambers, like space, is near vacuum. When the pressure in the pump tube becomes sufficiently high, the burst disc fails, releasing the hydrogen gas at very high pressure into the back of the launch package. The launch package is propelled down the barrel into the expansion tank. The expansion tank allows collection and dissipation of high pressure hydrogen gas and permits the controlled separation of the sabot/projectile assembly.
The projectile is photographed with high-speed cameras and flash x-rays just before impact. At times, the impacts are photographed to characterize the debris cloud. Three types of high-speed cameras are used. Cinema cameras run at 10,000 frames per second, 35-mm infrared cameras are capable of 2 million, and the digital cameras are capable of 200 million frames per second.
Laser intervalometers measure projectile velocity. The time difference between interruption of laser beams by the projectile yield an extremely accurate calculation of its velocity. In addition, high-speed data acquisition systems using light detectors, strain gauges, pressure transducers, accelerometers, and thermocouples provide reliable diagnostics.
For additional information, contact Karen Rodriguez at (575) 524-5723 or karen.m.rodriguez@nasa.gov.