AEDC supplying data for next NASA Constellation program milestone

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Data from a test at Arnold Engineering Development Center (AEDC) will be used to support a major NASA Constellation Program milestone - the Vehicle Integration Preliminary Design Review (PDR).

A team at AEDC's von Karman Facility has conducted aerodynamic heat transfer testing on Ares I's first stage, a reusable, man-rated, solid rocket booster (SRB).
Ares I is the crew launch vehicle being developed by NASA as a component of Project Constellation.

Ares I will be used to launch Orion, the spacecraft being designed for human spaceflight missions after the space shuttle is retired in 2010.

In order to reuse the Ares I first stage, it must be able to withstand the aerodynamic heating environment induced during its uncontrolled re-entry into the earth's atmosphere at speeds as high as Mach 7. Prior to testing, previous Space Shuttle SRB wind tunnel and flight data was limited to approximately Mach 4 and below.

Testing at AEDC provided NASA with data to validate and improve the current scaling approach utilized to generate thermal design environments in the expanded Mach range.

NASA officials used the three percent scale model to simulate the Ares-I first stage aft section because this is the area of highest re-entry heating. The test also provided detailed data on various components of Ares I.

The Ares I first stage separates from the upper stage at between Mach 6 and 7
during ascent. The first stage then coasts up an altitude of almost 300,000 feet before reentering in a tumbling and rolling motion. The motion and orientation are similar to the Shuttle SRB during entry but the Mach number during reentry is significantly higher.

The high aerodynamic heating anticipated due to the higher reentry Mach number made it much more important to obtain an accurate database to produce a higher fidelity design environment.

Nathan Payne, Aerospace Testing Alliance (ATA) project manager for the test, said the Ares I first stage heat transfer testing conducted in VKF Tunnels B and C went well.

"This was the first testing on the booster section," he said. "We've done a launch abort system (test) for them earlier in the fall. We've got other tests coming up this year and I'm sure we'll schedule more as they come along."

He said the testing was fairly typical of what they normally do for a heat transfer test, but it was uneventful largely because of what went on behind the scenes.

"The hardest part of the test was the design and fabrication of the model," Payne said. "The model's design changed over time, sometimes the changes were small and other times they were major. Overall, when we got the model and it was finished, it was exactly the way our customers wanted it, all the heat transfer gauges and thermocouples worked excellently."

He said the model shop did a first-rate job, but added that the center's Aerothermal Measurements Lab (ATML) also played a critical role in preparing the model for the test.

"I have never seen a model so heavily instrumented before," Payne said. "I know the instrument lab said they have seen models like this before, but there are very few, and it had been a long time since the last one, about four years from what I understand. The model shop and Aerothermal Measurements Lab folks - really get a gold star for this project."

Stuart Coulter, ATA engineer at the ATML, said the Ares I first stage booster model had many more heat transfer gauges than normal, but not as many as some of the lab's model instrument project efforts in the late 1990's.

"What made this model unique was that many gauges were mounted in a thin-wall cavity or on narrow flanges," Coulter said. "The backside of these gauges and their signal wires were exposed to the tunnel flow and had to be protected. Some gauge wires were routed through very precise narrow channels machined into the exterior of the model. Normally, signal wires are easily routed into a 'safe' model interior."

Coulter credited ATA Design Engineer Scott Wieland, responding to the initial request from the customer, with designing the model and working with the model shop machinists later in the process to accommodate design modifications.

Payne said the customer came away with valuable data they need to ensure the survivability of the spacecraft's booster.

"The flight vehicle - the Ares I stack that we tested, the booster, it is made to be reusable," he explained. "Since they are releasing it at a lot higher altitude and a much quicker than the shuttle booster, they want to make sure it would still be reusable once it reentered, that it wouldn't burn up."