ARNOLD AIR FORCE BASE, Tenn. --
The Hypervelocity Flyout, Impact and Lethality Ground Test and Evaluation team of the Space Test Branch, Test Division, successfully reactivated the 8-inch-diameter barrel capability of Hyper-ballistic Range G after the 8-inch barrel sat unused for more than a decade.
Range G, located at Arnold Engineering Development Complex, Arnold Air Force Base, Tenn., is a two-stage light-gas gun with a soft-launch capability. Two-stage light-gas guns use a propellant in the first stage to drive a piston to compress a gas which ruptures a burst disc and launches the projectile at higher velocities than can be achieved with just propellant or just gas. Soft-launch describes the minimized acceleration loading experienced by projectiles while still achieving hypervelocity speeds. This capability allows for high-fidelity models to be used that under normal acceleration loading would be damaged.
The Range G gun is most often fired with the 3.3-inch diameter barrel. A 4-inch barrel is also available. The larger 8-inch barrel permits the use of projectiles that are closer in scale to the actual test article being modeled, in turn reducing the amount of possible deviation that has to be accounted for in the data.
“The customer was actually unaware of this AEDC capability, but when they found out from an internal contact, they reached out,” said Bonni McKinney, an AEDC test engineer for the Hypervelocity Flyout, Impact and Lethality Ground T&E capability. “This particular effort is being done in the 8-inch configuration, as opposed to the 3.3-inch, to achieve better scaling for the checkout of diagnostics to be used in full-scale testing. Full-scale testing has been a scheduling issue for them and our configuration allows them to get some of the necessary data earlier.”
McKinney said most of the testing completed with the 8-inch barrel focuses on impact and interaction between the projectile and the target. This test was a reverse ballistics test in which the projectile is actually what the target material would be in a full-scale test and the test article, which would normally be in flight, is fixed in place.
Reactivating the 8-inch barrel involved swapping out the 3.3-inch gun barrel. Each barrel is comprised of multiple large, heavy sections. Once the sections of the 8-inch barrel were in place, they had to be perfectly-aligned and then connected. This included feeding sections of the barrel into the test tank through a porthole. The tank is a vacuum chamber that allows range staff to simulate various altitudes for testing.
Adding to the difficulty with the alignment was the use of a track for the test. When a projectile needs to impact in a precise location, Range G can be outfitted with a track that extends from the barrel and guides the projectile to a short distance from the impact point. This track must be perfectly aligned with the barrel.
“The 8-inch barrel is an incredibly unique capability,” McKinney said. “To my knowledge, AEDC is currently the only range that has the capability of launching this diameter projectile up to 4 km/sec. That being said, it is also incredibly niche. I think this is an opportunity for AEDC to provide a much-needed capability to program offices, maybe even one that they didn’t know they needed.”