image: Comparison of the flier velocity between experiment and numerical results is shown. The thickness of titanium flier is 0.5mm, and the impact velocity is 7.587km/s. view more
Credit: ©Science China Press
In the past 20 years, the Laboratory for Shock Wave and Detonation Physics Research in Institute of Fluid Physics (IFP), China Academy of Engineering Physics (CAEP) has conducted the research in hypervelocity launch technology. The State Key Laboratory of Advanced Technology for Materials Synthesis and Processing of Wuhan University of Technology participated in the research as a cooperator, and took charge of the flier processing. In this project, significant progresses have been made in optimization of the physical design, material processing and experimental measurement technology. Their work, entitled "The gas gun launch advances in numerical simulation of hypervelocity impact", was published in SCIENTIA SINICA Physica, Mechanica & Astronomica, 2014, Vol 44(5).
Numerous space debris in the orbit of the earth, especially the small ones that are untraceable and unevadable, have seriously threatened the safety of the spacecraft. It is of great importance to carry out the numerical simulation and experiment of the impact between the debris and spacecraft, and to investigate the physical process and characteristics, which can be used to enhance or improve the protection structure of the spacecraft, and reduce the harm of the space debris.
In their project, not only significant progresses have been made in optimization of the launcher's configuration, physical design of the flier plate, material processing and experimental measurement technology, but also the experimental data of equation of state (EOS) for the material under ultra-high pressure was also obtained. Their project leads to the progress of the hypervelocity launch theory and experiment technology, and the development of the material science and the processing technology as well. The concrete achievements in this project are as follows:
1. The fluid dynamic codes–the Multi-Fluid Piecewise Parabolic Method (MFPPM) and Level Set Fluid in Cell (LSFC) have been developed, and the optimization of the launcher's configuration and physical design of the flier plate have been carried out by the MFPPM and LSFC codes. The code MFPPM, which can be applied to the multi-dimensional and multi-fluid dynamic simulation, has been validated in the simulation of Sandia's hypervelocity launcher, and widely used in the optimization of the hypervelocity launcher and physical design of the flier. However, the MFPPM does not consider the material strength due to its slight effect under the hypervelocity. Luckily, the LSFC proves to be a remedy for this shortcoming. Evolving but being different from the HELP code, the LSFC takes the Level Set method to describe the material interface. Despite of its only first-order accuracy, the LSFC is able to handle adaptive meshing and parallel computing. Furthermore, it is compatible with various forms of multiphase equation of state, and easily deals with the fluid dynamic simulation including different constitutive models and strength models. It also can be widely used to numerically simulate the transient dynamics processes such as process driven by detonation, the loading effect and the penetration in the flied of explosion and detonation shock dynamics. In addition, it is suitable for the numerical simulation of impact generated debris and structural protection in the hypervelocity impact process.
2. The DISAR/DPS testing and diagnostic technologies have been developed, and the simultaneous measurement of shock wave velocity and particle velocity has been realized, paving the way for the accurate measurement of EOS data by absolute method. In the previous study, our group has investigated the Hugoniot data of various metal materials under ultra-high loading pressure using the acquired quasi-isentropic loading technology, which provides precious and high-quality experimental data for the relative research in weapon physics. The continuous successful applications further maturate loading technology of the three-stage light gas gun. In the past two years, we have launched aluminum, tantalum and platinum flier to velocity of 11km/s, 10.0km/s and 9.0km/s, respectively. Moreover, we successfully launch a tantalum flier to impact the platinum target in March 2014,in which the flier was accelerated to 10.4km/s and kept relatively flat, and the loading pressure in platinum target went up to 1060GPa. This represented another successful launch at ultra-high pressure after the experiment with pressure up to 1018GPa in December 2013, in which the precious EOS data in the platinum target was obtained. Historical breakthroughs have thus been made in the two successful loading experiments performed on three-stage light gas gun with pressure up to 1TPa, and it turns out to be the first record to obtain the pressure with TPa magnitude loading by gas gun under the experiment condition in the world.
See the article:
BAI J S, WANG X, HUA J S, et al. The gas gun launch advances in numerical simulation of hypervelocity impact (in Chinese). SCIENTIA SINICA Physica, Mechanica & Astronomica, 2014, 44(5): 547-556. http://phys.scichina.com:8083/sciG/CN/10.1360/132012-782
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