Inexpensive aerial test beds can study ultrasonic technologies

Inexpensive aerial test beds can study ultrasonic technologies

As part of research to evaluate CubeSats as an aerial test ground for technologies being developed for future generations of hypersonic vehicles, GTRI researchers developed this plasma source to generate high temperatures. Credit: Sean McNeil, GTRI

Miniature satellites called CubeSats are taking on larger roles in space missions that could previously be performed by more expensive conventional spacecraft. Now, researchers at the Georgia Institute of Technology are envisioning a larger mission for CubeSats as an aerial test of technologies being developed for future generations of hypersonic vehicles.

The development of hypersonic vehicles that can travel through the Earth’s atmosphere at Mach 5 or faster—five times the speed of sound—is attracting significant new funding from governments and branch. However, the test facilities needed to evaluate thermodynamics, aerodynamics, acoustics and other critical issues to operate in that harsh environment are limited, in high demand and in use. costly.

Georgia Tech researchers want to remove that barrier by building rigid CubeSats that can use re-entry from space to create the conditions needed to evaluate ultrasound technologies. Small satellites, with their main systems protected from the heat of re-entry, will be launched into the upper atmosphere from the International Space Station or a “carpool” rocket to provides several minutes of testing at speeds up to Mach 25.

“We are looking at the feasibility of building an inexpensive flying wind tunnel,” said Krish Ahuja, Regents Professor of Aerospace Engineering and head of the aerospace and acoustics division in the Laboratory. aerospace, transportation and advanced systems of the Georgia Institute of Technology. Institute (GTRI) and project principal investigator. “We were able to collect quite a bit of data needed for hypersonic research and provide a new way to conduct studies that can currently be quite difficult.”

Initial study suggested development of 6U . vehicle

Based on a six-month feasibility study that included collaborators from the Georgia Tech School of Aerospace Engineering and two private companies, Ahuja believes it will be worth pursuing the design of a 6U. test car for concept evaluation. (6U CubeSat is about the size of a desktop system unit). If that proves promising, larger vehicles could be built with more capable instrumentation, guidance and even propulsion.

The goal in the first year of the project was to understand what it takes to develop and launch test platforms—and recover them after flight. The design and development of new experimental vehicles must overcome significant challenges related to the control of aircraft flight time, speed, altitude and direction. transport during data collection. Systems to communicate with the ground and track the vehicle’s trajectory must also be developed. Additionally, part of the first year goal is to create a roadmap that shows the development and testing process.

“Ongoing work will include a ‘system of system’ analysis of the concept to model its performance and interactions with other systems. Support system to evaluate its ability to conduct scientific research,” said Ahuja. “Our initial calculations indicate that the 6U CubeSat can be hardened with a thermal protector under ultrasonic conditions to help progress perform limited feasibility experiments. This will be a building block for future systems that will be larger and able to conduct the testing we envision.”

Initial testing may involve a free fall test vehicle, but subsequent tests will include control surfaces that provide steering to prevent somersaults and unwanted impacts. other. Multiple CubeSats can also be operated together.

Possible new possibilities for small satellites

CubeSats, so called because they are designed to standard cube sizes, are not usually designed for post-mission recovery; When their job is done, they simply burn up in the air. Since Ahuja wants to study the effects on materials and collect data from onboard instruments, the satellites flying in the wind tunnel will need to be recovered using a parachute to drop them into the recovery area. , perhaps in the Southwest Desert.

“Getting them down in the right place will require good guidance and control, good telemetry and propulsion,” he said. “The challenge will be to make these really small and inexpensive. To get the information we need, we’ll have to get the test platform safely down to the ground.”

The high temperatures generated upon re-entry into Earth’s atmosphere could be useful for more purposes than simulating hypersonic conditions. Ahuja believes that the heat could be used to power a proprietary device that could provide steering for the CubeSats, which typically do not have a propulsion system.

Much of the current research on supersonic flight relies on data from computational fluid dynamics simulations, which need validation from testing. In addition to the information gleaned from the experiment, Ahuja believes that small spacecraft can make a big contribution by providing a real-world anchor for the analytical tools that researchers are using for a variety of methods. supersonic facility.

A new approach to ultrasound testing is needed

Supersonic testing is often performed in short-duration wind tunnels or high-temperature test platforms, meaning that high-speed and high-temperature conditions are difficult to achieve simultaneously and for the duration of the test involved. to hypersonic vehicles. In addition, there are very few existing facilities that can perform such testing and they are in high demand. The new test bed is expected to provide about three minutes of testing per flight.

There is now an urgent need to understand how much and what type of thermal protection system is needed to protect hypersonic vehicles at high speeds, where friction can generate temperatures of more than 4,000 degrees Fahrenheit. There are also questions about sound effects and how uneven heating would spread throughout the vehicle and potentially damage the vehicle’s structure.

“The airflow over a hypersonic vehicle can be both turbulent and layered, varying in different parts of the vehicle,” Ahuja said. “These large changes in flow properties can produce large changes in vehicle surface temperature, which is highly undesirable for the structural integrity of the vehicle. Therefore, we need to understand. This heat load cannot be studied in conventional wind tunnels, which typically provide runtimes of a few seconds under supersonic conditions, because because it takes a while for those conditions to stabilize.”

Acoustic loads can also significantly affect the structural integrity of hypersonic vehicles, and that also takes time to assess. “Acoustic loads are of the kind that can create cracks in the structure that grow over time,” he said. “We can create and study these conditions with our flight test.”

By gathering enough data from the initial studies, Ahuja hopes to attract collaborators to help implement the new experimental approach.

“There is a lot of enthusiasm for this so I believe our chances of success are very high,” he said. “By launching from another space system, we won’t have to worry about the initial propulsion. This could solve a lot of the challenges in conducting hypersonic research.”

quote: Inexpensive aerial test platforms that can research hypersonic technologies (2022, 1st December) get 1st December 2022 from airborne-testbeds-hypersonic-technologists.html

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