Rolling Hills researchers measure airfoil surface pressures on this model at very low Reynolds numbers in the water tunnel. (Photo Courtesy of Rolling Hills Research Corp.)

Small Businesses Can Maximize IPP Funds To Develop Technology NASA Needs And That Leads To Commercial Products

Rolling Hills Research Corp. is a small business that has earned success through its work and its use of Innovative Partnerships Program funding, such as the Small Business Innovative Research and Small Business Technology Transfer programs, to more closely examine its ideas.

Rolling Hills President and CEO Brian Kramer said at the core of the company's success is, "we are very interested in the ideas we propose and we have a lean operation."

In addition, the company has become focused on using aerodynamics to improve vehicles and their safety and promoting creativity and freedom in applying innovative ideas to problems.

Two categories summarize many of Rolling Hill's successes: its water tunnel and application of evolutionary flow-visualization and measurement techniques, and using the water tunnel to do "pretty much anything you can do in a wind tunnel," Kramer said. In addition, the company also is known for its research into flow control and drag reduction techniques.

The water tunnel and SBIR

 The water tunnel and the expansion of its capabilities are SBIR success stories showcasing what technology development agreements are intended to lead to - a commercially viable product that can resolve technology challenges, Kramer said.

A wide range of challenges can be met through the use of the water tunnel and at an economical cost. Small models used in the water tunnel are less expensive and can be developed early in the program, when changes can prevent errors leading to big-dollar investments, he added.

The water tunnel was first designed and built for flow visualization, or how flow moves over aerodynamic surfaces. Over the years Rolling Hills researchers took the tool to the next level by using SBIR agreements to develop instruments for use in the water tunnel, such as the five-component submersible balance to measure forces and moments in the water tunnel.

During the past year Rolling Hills researchers were studying surface pressures on a fully instrumented airfoil model in the water tunnel for an SBIR-funded investigation. It simulated a wing in flight, which is common in a wind tunnel but not in a water tunnel.

These images show a new Rolling Hills Research flow-visualization technique developed for studying the effect of the company's patented method of controlling boundary-layer transition from laminar to turbulent on a low-Reynolds-number propeller. The flow-visualization technique shows the separation pattern on the low-Reynolds-number propeller as a function of full revolutions per minute. (Graphic Courtesy of Rolling Hills Research Corp.)

Very low Reynolds number airfoil development with pressure measurements did not exist before, and the new tool allowed the company to take a qualitative tool and make it more quantitative, said Mike Kerho, Rolling Hills chief aerodynamicist and a principal investigator on many of the company's projects.

"Through an SBIR with Dryden, we were able to develop the technology to accurately measure model surface pressures at very low Reynolds numbers. If you're going to do airfoil models and you want to learn something about what the flow field is doing, pressures are a good diagnostic tool to obtain a quantitative understanding of the state of the flow field," Kerho said.

In addition to using the water tunnel for two-dimensional airfoil studies, three-dimensional aircraft models can be studied using a unique computer-controlled dynamic model support system, which provides the ability to rotate the model in the water tunnel about the three axes - pitch, yaw and roll - to permit researchers to take data as the test article is rotated in the water tunnel and for which the stability derivatives can be calculated, Kerho said.

The new capabilities for the water tunnel have made it even more attractive to universities that continue to purchase them in the United States and in a number of countries around the world, including Mexico, France and England.

Stereo lithography

A rapid-prototyping technology, which Rolling Hills contracts out for its customers to gain even greater use of the water tunnel, is stereo lithography, Kerho explained.

While metal and fiber glass models are required for a wind-tunnel environment they are typically costly and time-consuming to manufacture. A system similar to three-dimensional computer-assisted drawing programs now can use lasers to sculpt plastic, resulting in an accurate prototype that is strong enough to endure water-tunnel testing, he said.

Because the water tunnel applies less pressure to a test object compared to a wind tunnel, the stereo lithography models hold up, Kerho said. Model accuracy is essential in wind and water tunnel testing and this process for model manufacturing coupled with the water tunnel can provide both a time- and cost-effective alternative to traditional wind-tunnel testing. Rolling Hills worked with several rapid prototyping shops to develop a methodology that provides high-quality models quickly and economically.

Using SBIR for innovative research

The SBIR grants have been invaluable to Rolling Hills for examining its new concepts, Kramer said.

"It's like peeling back the skin of an onion. When you peel away a layer, you can learn about a limiting factor somewhere else," he said. "Once we identify a problem, sometimes we have to solve five others before we get there."

The funding provided by the SBIR awards is key for the company.

"SBIRs help us to pursue new ideas that we want to research and is our primary source for funding them," Kerho said. "We couldn't do it without SBIR. We do not have the extra capital to do research and development. We use the SBIR agreements to take our ideas and flesh them out to see if they can work. In addition, the technical reviews often give us other ideas on how to best make it work out."

Dryden is a frequent partner with Rolling Hills on SBIR proposals, but the company also has worked with Langley Research Center, Hampton Va., and Ames Research Center, Moffett Field, Calif.

Micro UAVs

The Rolling Hills water tunnel work does have a downside: the Reynolds number produced by the water tunnel cannot be scaled for larger vehicles because of the boundary layer differences, or airflow that moves directly above aerodynamic surfaces, he said.

However, smaller unmanned air vehicles, or micro UAVs, are one class of aircraft that does not have that challenge, he said. Those vehicles can be tested at full-size and full-flight Reynolds numbers, so the water tunnel can produce accurate results.

In addition, the company has applied for a patent for a method for controlling the boundary layer transition from laminar to turbulent on low-Reynolds-number aircraft as a result of some of its SBIR work. Micro UAVs and high-altitude, long-endurance aircraft have challenges caused by very low Reynolds numbers, such as laminar separation bubbles. This technology has proven to reduce drag by 35 to 40 percent, Kramer said.

Through the same SBIR used to develop the low-Reynolds-number airfoil drag-reduction technologies, Rolling Hills also developed a flow-visualization methodology to study the flow field of small, low-Reynolds-number propellers. Similar to the main airfoils on micro UAVs and high-altitude, long-endurance aircraft, the propellers on these aircraft that generate propulsion also suffer from the same low-Reynolds-number-based degradation. Rolling Hills developed a flow-visualization technique to apply its SBIR-developed technology to provide a detailed picture of the propeller surface flow field that can be used to help improve propeller performance.

IPP concept

A current Innovative Partnership Program seed fund proposal that Rolling Hills has on the table is for a separation detector. The IPP is the big umbrella that includes a number of funding mechanisms, such as SBIR, STTR, and the IPP seed fund, to assist companies with their fledgling technology projects.

Called "electronic yarn," the detector is essentially an array consisting of 100 or more self-powered and self-contained sensors. The idea is to replace tufts and cameras for detecting separated airflow in flight with a simple and robust system that does not require calibration or cameras and gives a simple yes-or-no answer to the question of whether there is an aerodynamic separation.

This could be useful in programs like that of the Stratospheric Observatory for Infrared Astronomy, in which there is a large opening in the side of the aircraft where the telescope "peers" out from its host NASA 747SP. NASA may need to investigate and modify configurations like the SOFIA to ensure flow-separation problems do not exist, Kramer said.

The commercialization prospects are high if the detector performs as predicted, Kramer said. The sensors can record information on a flash drive and require no external power source. The application of the idea goes beyond flight research. It could be used in automobiles, ducting and other scenarios in which sensors are required and where there is no visual access available.

STTR projects

Rolling Hills researchers are looking forward with an ongoing STTR agreement with partner California Polytechnic State University in San Luis Obispo, Calif. That work is focused on a thrust-vectoring aerospike nozzle and evolved into a current project with an oxidizer-cooled aerospike.

Aerospike nozzles are considered to be efficient because they adjust to changes in atmospheric pressure due to altitude (compared to a bell-shaped nozzle that does not) as the rocket propels a vehicle. The problem with aerospike nozzles is they often become too hot and need to be cooled, Kramer said. The oxidizer-cooled aerospike concept does what its name implies - it turns fuel into vapor and uses that phase change to cool the engine.

Another new development for Rolling Hills researchers is an STTR agreement with the University of Illinois for a real-time flight-envelope monitoring capability that would give pilot alerts in situations such as icing, heavy rain, battle damage, bird strikes, and other safety-related dangers. If the systems prove robust, they would be good candidates for commercialization, he said.

Indications are that IPP funding mechanisms will continue to be a primary way for small businesses to find ways to work on innovative research ideas. Kramer offered this advice for companies looking to succeed in obtaining grants for their research: "It is best not to chase the 'hot technology' and jump on the bandwagon. Stick to what you have knowledge and interest in. Stick with your strengths. That's not to say don't look to branch out or be creative, but be smart about it."