Holloman High Speed Test Track Research Articles

Modeling a Nonlinear Melt Region as a Result of High-Speed Sliding

The solution discussed in this paper relates to the high-speed movement of a vehicle along a rigid support in which friction becomes a heat energy source for melt. A one-dimensional nonlinear heat transfer set of equations dependent upon a vertical forcing function, created by horizontal movement characterized by velocity, is considered in the supersonic regime. A good example of this type of condition occurs within the U.S. Air Force Holloman High Speed Test Track at Alamogordo in New Mexico, which supports experiments routinely run at hypersonic speeds. In addition, there are several applications including rail guns, high-speed trains, and hypervelocity projectile research. This application is the setup at the Holloman High Speed Test Track. The testing there involves articles propelled at high velocities, in excess of Mach 8, while attached to a rail by way of wraparound slippers. Modeling the entire test run would be computationally expensive due to thermal–mechanical coupling and nonlinearities in geometry as well as material. This work uses a finite difference scheme to solve the one-dimensional heat transfer equation while accounting for the time the slipper is in contact with the rail, versus not in contact, as well as the differing pressures experienced by the slipper as it travels down the track. It also accounts for material properties that change with respect to temperature, leading to nonlinearities. The model output shows a direct correlation between predicted melt at the surface and the damage as measured by a slipper after the acceleration portion of a test event.

Engineering Approach for the Evaluation of Mechanical Wear Considering the Experimental Holloman High-Speed Test Track

AbstractThis research is directed toward an understanding of the high-speed interaction effects that two bodies have on each other. The experimental high-speed test track at Holloman AFB has undergone many design innovations over 50 years. One of the problems that remains in the modern era related to improving the speed characteristics of a rocket test sled is the wear that the interconnecting device, called the slipper, undergoes as it slides down the rail and impacts local asperities. The research is separated into two main areas. The first is the metallurgical investigation in which the material change is brought about by the surface friction through surface collision, and characteristics are determined that lead to a numerical model. The second is the development of a finite-element model using the commercial code ABAQUS, which is used in an attempt to capture the physics involved in the overall phenomenon. It became evident that the wear is not uniform, but is dictated by the evolving aerodynamics of...

Magnetic Levitation Upgrade to the Holloman High Speed Test Track

Two superconducting magnets, mounted on a rocket sled are propelled by solid fuel rocket motors. During sled motion, the field from the magnets interacts with passive copper rails embedded in a concrete guideway to produce levitation and flight stability. Six flight tests have been successfully conducted to date with the most recent in April 2008 reaching 673 kilometer per hour. The magnets consist of racetrack coils, which are wet lay-up wound with rectangular NbTi wire. They were tested to 245 A with a peak field of 7.5 T and winding current density of 38 kA/cm2. The coils are bath cooled. A passive valving system prevents loss of liquid during rapid acceleration and deceleration. Boil-off gas cools an aluminum thermal shield and the current leads. In this paper we present the most recent magnet design, static and flight test results.

An evaluation of high velocity wear

The Holloman High Speed Test Track (HHSTT) is a rocket-powered sled track facility used for testing a variety of hypervelocity aerospace applications at speeds approaching 3000 m/s. Research conducted at the HHSTT has to consider several features that result from the physics of high velocity. The feature of gouging has been noted to be a significant factor at speeds above 1.5 km/s. This characteristic has been studied in recent years by several authors including the senior author of this paper. Another feature that is always present is that of wear between the shoe and the rail resulting from their sporadic contact as the sled travels down the rail. This paper attempts to establish a proof concept that can eventually be extended into future understanding of wear at high velocities. The authors approached wear using two separate techniques. The first technique involves the use of equations that have been successfully used to represent wear at low speeds. This technique relies on the research of Lim and Ashby and the equations they developed to model the different modes of wear. Included in this technique is the use of Archard's wear equation. The second technique, completely independent of the first, relies on the physics of frictional movement displayed by a model produced using CTH, a hydrocode developed by Sandia National Laboratory for analyzing hypervelocity impact problems. This technique considers features that are potentially present in the overall phenomenon but are limited to the use of the code. The authors have found it necessary to make simplifying assumptions in both techniques, but the end result is a better appreciation of what is needed to put together a more accurate model of wear at high velocities.

Further validation of a general approximation for impact penetration depth considering hypervelocity gouging data

A first-order approximation of penetration depth is developed for use in engineering design. A survey of available penetration data is used to construct a one-dimensional approach for estimating the geometry of a crater resulting from high-energy impact. The results are generalized to allow approximations to be made using existing experimental data without the requirement for laboratory testing. This approach for penetration depth approximation is validated using the hypervelocity gouging data from the Holloman High Speed Test Track (HHSTT) and hypervelocity gouging impact tests conducted by the authors.

Application of Laser Techniques in Rain Impact and Erosion Investigations

A laboratory photographic system employing a giant pulsed ruby laser as a light source was adapted to field use in recording erosion and rain impact phenomena on controlled rain-erosion testing at the Holloman High Speed Test Track facility. Techniques using the short-time duration of 20 nanoseconds to effectively stop the sled motion of specimens traversing a rain environment at speeds in excess of 1.8 km/sec are described. A front/back light method for recording erosion detail, flow visualization and shadowgraph information with a single laser as the light source for multiple cameras is presented. Photographs of rain drops impacting on sled specimens are shown along with a comparison with conventional photographic techniques. The advantages of employing the single laser with multiple cameras discussed in this paper demonstrate its applicability to the diverse problems of recording erosion, abla-tion and aerodynamic data of test specimens traveling at hypersonic speeds.