Holloman HSTT rainfield undergoes improvements Published Sept. 21, 2020 By Marshall Polk Hypersonic Test and Evalution Investment Portfolio HOLLOMAN AIR FORCE BASE, N.M. -- Missiles and other high-speed weapons systems are required to fly through a variety of weather situations. One type of weather that is an important concern for system design is rain. When testers need to understand how missile hardware will perform in the rain they often turn to the Holloman High-Speed Test Track. Run by the 846th Test Squadron (846 TS) at Holloman AFB, N.M., the test track uses a rocket-propelled sled to fly test hardware at high speeds through an artificial rainfield. A recent project funded by the Test Resource Management Center (TRMC) will provide rainfield test customers with more options and also increase the operational efficiency at the track. Bryan Sinkovec, the program manager for the rainfield effort at the 846 TS, describes the upgrade as a “giant technology leap forward for the sled track.” Prior to this project, the rainfield was set up by manually adjusting valves and reading pressure gauges along thousands of feet of test track. The initial setup could often take days of running water to get the system correctly set up. “We are now able to instantly adjust the operating parameters from a single computer in the control room,” Sinkovec said. “Both our setup time and total water usage should be greatly reduced. The control system also has numerous sensors monitoring and logging the performance of the rainfield in real time. We can now precisely identify any part of the system that is not within specifications and quickly dispatch personnel to correct the problem.” The TRMC project team also constructed an on-site lab to study how closely the artificial Holloman rain matches different types of natural rainfall. Mariana Scott, a meteorologist with Integration Innovation, Inc. (i3), has been working with the 846 TS engineering team to explore how data from the rain lab will translate into improved capabilities on the test track. “The distribution of rain drop sizes can vary significantly depending (upon) atmospheric conditions,” Scott said. “The old rainfield was able to produce drop distributions representative of a narrow set of atmospheric conditions. We reviewed weather from all across the globe and also talked with several test customers. That research told us that we needed to develop more options for future test customers.” 846 TS rain lab engineer Kody Gill has been using the research from Scott as a starting point for development work in the rain lab. “The initial lab results look very promising,” Gill said. “In just a few short months, we have been able to discover some critical parameters that greatly influence the drop distribution. We still have much to learn, but we plan to continue working in the lab over the course of the next year so we can fully understand all the sensitivities of the system.” Accurate measurements of the rain were needed in both the lab and out on the track. The team partnered with Artium Technologies, Inc., a small business specializing in atmospheric measurement systems, to develop a custom disdrometer to accurately measure the artificial rain. A disdrometer is an instrument used to measure drop size distributions and the velocity of falling rain. Artium has previously developed instruments for use on NASA atmospheric sampling aircraft and in NASA wind tunnels. Building a system for the unique configuration used at Holloman was challenging but the hardware was delivered just in time for use in the rain lab. “The disdrometer has been essential to our success in the lab” Gill said. “The instrument allows us to quickly obtain data that can be reviewed by the team.” Several organizations came together to make this project a success. Dynetics, Denco, Air and Liquid Systems Inc., and Central Process Engineering all worked together to design and construct the rainfield and rain lab under a Test and Evaluation Technologies for Ranges Armaments and Spectrum contract. The entire project from design to final acceptance took a little over a year and a half to complete. TRMC-funded verification sled tests are scheduled for next summer. These tests will validate the new rainfield capability with realistic missile materials. The checkout tests will also help validate modeling and simulation tools that use the data from the Holloman rainfield along with data from other ground test facilities to make flight predictions. The end result will be a suite of ground test tools and test facilities that ensure U.S. weapon systems remain highly capable in all types of weather.