Tech

April 23, 2012

Engineering review board concludes review of HTV-2 second test flight

darpa-htv-review

Following an extensive seven-month analysis of data collected from the Aug. 11, 2011, second flight of DARPA’s Hypersonic Technology Vehicle (HTV-2), an independent engineering review board investigating the cause of a flight anomaly completed its report.

The findings of the ERB validated the vehicle’s aerodynamic design and uncovered new information regarding the thermal material properties of the vehicle.

“The greatest achievement from Flight Two, which the ERB’s findings underscored, was that we successfully incorporated aerodynamic knowledge gained from the first flight into the second flight,” said Air Force Maj. Chris Schulz, DARPA program manager, who holds a doctorate in aerospace engineering.

A technology demonstration and data-gathering platform, the HTV-2′s second test flight was conducted to validate current models and increase technical understanding of the hypersonic regime. The flight successfully demonstrated stable aerodynamically-controlled flight at speeds up to Mach 20 (twenty times the speed of sound) for nearly three minutes. Approximately nine minutes into the test flight, the vehicle experienced a series of shocks culminating in an anomaly, which prompted the autonomous flight safety system to use the vehicle’s aerodynamic systems to make a controlled descent and splashdown into the ocean.

“The initial shockwave disturbances experienced during second flight, from which the vehicle was able to recover and continue controlled flight, exceeded by more than 100 times what the vehicle was designed to withstand,” said DARPA Acting Director, Kaigham J. Gabriel. “That’s a major validation that we’re advancing our understanding of aerodynamic control for hypersonic flight.”

The ERB concluded that the “most probable cause of the HTV-2 Flight 2 premature flight termination was unexpected aeroshell degradation, creating multiple upsets of increasing severity that ultimately activated the Flight Safety System.”

Based on state-of-the-art models, ground testing of high-temperature materials and understanding of thermal effects in other more well-known flight regimes, a gradual wearing away of the vehicle’s skin as it reached stress tolerance limits was expected. However, larger than anticipated portions of the vehicle’s skin peeled from the aerostructure. The resulting gaps created strong, impulsive shock waves around the vehicle as it traveled nearly 13,000 miles per hour, causing the vehicle to roll abruptly. Based on knowledge gained from the first flight in 2010 and incorporated into the second flight, the vehicle’s aerodynamic stability allowed it to right itself successfully after several shockwave-induced rolls. Eventually, however, the severity of the continued disturbances finally exceeded the vehicle’s ability to recover.

According to Schulz, “HTV-2′s first flight test corrected our models regarding aerodynamic design within this flight regime. We applied that data in flight test two, which ultimately led to stable aerodynamically controlled flight. Data collected during the second test flight revealed new knowledge about thermal-protective material properties and uncertainties for Mach 20 flight inside the atmosphere, which can now be used to adjust our assumptions based on actual flight data and modify our modeling and simulation to better characterize thermal uncertainties and determine how to assess integrated thermal systems.”

Aerodynamic assumptions and extrapolations from known flight regimes proved inadequate when preparing for HTV-2 inaugural flight test. The data from second flight revealed that extrapolating from known flight regimes and relying solely on advanced thermal modeling and ground testing could not successfully predict the harsh realities of Mach 20 atmospheric flight.

“A group of nationally-recognized experts from government and academia came together to analyze the flight data and conduct extensive additional modeling and ground testing for this review,” Schulz said. “The result of these findings is a profound advancement in understanding the areas we need to focus on to advance aerothermal structures for future hypersonic vehicles. Only actual flight data could have revealed this to us.”

Moving forward, the HTV-2 program will incorporate new knowledge gained to improve models for characterizing thermal uncertainties and heat-stress allowances for the vehicle’s outer shell. The remediation phase will involve further analysis and ground testing using flight data to validate new tools for this flight regime. The ERB findings and remediation phase efforts will inform policy, acquisition and operational decisions for future Conventional Prompt Global Strike initiatives executed by the Office of the Secretary of Defense, Acquisition, Technology & Logistics, Strategic Warfare directorate-the goal of which, ultimately, is to have the capability to reach anywhere in the world in less than one hour.

 




All of this week's top headlines to your email every Friday.


 
 

 

Headlines August 22, 2014

News: GAO: Pentagon violated law with Bergdahl swap - Congressional investigators say the Pentagon violated the law when it swapped five Taliban leaders for Army Sgt. Bowe Bergdahl, who was held prisoner in Afghanistan for five years.   Business: U.S. Air Force issues RFI for new rocket engine - The US Air Force is officially looking into...
 
 

News Briefs August 22, 2014

U.S. military deaths in Afghanistan at 2,200 As of Aug. 20, 2014, at least 2,200 members of the U.S. military had died in Afghanistan as a result of the U.S.-led invasion of Afghanistan in late 2001, according to an Associated Press count. At least 1,821 military service members have died in Afghanistan as a result...
 
 
navair-triton

MQ-4C Tritons to arrive at Pax River this fall

  MQ-4C Triton test air vehicles at Northrop Grumman’s facility in Palmdale, Calif., will fly cross-country to Naval Air Station Patuxent River, Md., this fall. The MQ-4C completed a test flight Aug. 19 with updated ...
 

 
Boeing photograph

Boeing program completes critical design, safety reviews

Boeing photograph Boeing recently completed the Phase Two Spacecraft Safety Review of its Crew Space Transportation-100 spacecraft and the Critical Design Review of its integrated systems, meeting all of the companyís Commerci...
 
 
global-hawk2

Air Combat Command loans Global Hawk to GVCTF

Air Force photograph by Jennifer Romo The 412th Test Wing’s Global Vigilance Combined Test Force received a Global Hawk Block 40 Aug. 6, on loan from Air Combat Command. Tail number 2035, from Grand Forks AFB, N.D., is jo...
 
 

NASA awards program analysis, Control Bridge III Contract

NASA has awarded the Program Analysis and Control III Bridge contract for support services to ASRC Research & Technology Solutions of Beltsville, Md. The cost-plus-fixed-fee, indefinite delivery/indefinite quantity basic contract has a minimum ordering value of $1 million and a maximum ordering value of $37 million, with a performance period beginning Aug. 30 through Feb....
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>