Justin D. Littell

Heliogyro Solar Sail Research at NASA

The recent successful flight of the JAXA IKAROS solar sail has renewed interest within NASA in spinning solar sail concepts for high-performance solar sailing. The heliogyro solar sail, in particular, is being re-examined as a potential game-changing architecture for future solar sailing missions. In this paper, we present an overview of ongoing heliogyro technology development and feasibility assessment activities within NASA. In particular, a small-scale heliogyro solar sail technology demonstration concept will be described. We will also discuss ongoing analytical and experimental heliogyro structural dynamics and controls investigations and provide an outline of future heliogyro development work directed toward enabling a low-cost heliogyro technology demonstration mission ca. 2020.

A Comparative Analysis of Two Full-Scale MD-500 Helicopter Crash Tests

Two full scale crash tests were conducted on a small MD-500 helicopter at NASA Langley Research Center’s Landing and Impact Research Facility. One of the objectives of this test series was to compare airframe impact response and occupant injury data between a test which outfitted the airframe with an external composite passive energy absorbing honeycomb and a test which had no energy absorbing features. In both tests, the nominal impact velocity conditions were 7.92 m/sec (26 ft/sec) vertical and 12.2 m/sec (40 ft/sec) horizontal, and the test article weighed approximately 1315 kg (2900 lbs). Airframe instrumentation included accelerometers and strain gages. Four Anthropomorphic Test Devices were also onboard; three of which were standard Hybrid II and III, while the fourth was a specialized torso. The test which contained the energy absorbing honeycomb showed vertical impact acceleration loads of approximately 15 g, low risk for occupant injury probability, and minimal airframe damage. These results were contrasted with the test conducted without the energy absorbing honeycomb. The test results showed airframe accelerations of approximately 40 g in the vertical direction, high risk for injury probability in the occupants, and substantial airframe damage.

Photogrammetry Measurements During a Tanking Test on the Space Shuttle External Tank, ET-137

On November 5, 2010, a significant foam liberation threat was observed as the Space Shuttle STS-133 launch effort was scrubbed because of a hydrogen leak at the ground umbilical carrier plate. Further investigation revealed the presence of multiple cracks at the tops of stringers in the intertank region of the Space Shuttle External Tank. As part of an instrumented tanking test conducted on December 17, 2010, a three dimensional digital image correlation photogrammetry system was used to measure radial deflections and overall deformations of a section of the intertank region.

Large Field Digital Image Correlation Used for Full-Scale Aircraft Crash Testing: Methods and Results

Since the summer of 2013, five full-scale crash tests have been conducted at NASA Langley Research Center’s (LaRC) Landing and Impact Research Facility (LandIR) on deformable airframes for the evaluation of a variety of crashworthy concepts. Two tests were conducted on two CH-46E “Sea Knight” airframes as part of the Transport Rotorcraft Airframe Crash Testbed (TRACT) project and three tests were conducted on three Cessna 172 General Aviation aircraft as a part of the Emergency Locator Transmitter Survivability and Reliability (ELTSAR) project. Full field digital image correlation (DIC) data was obtained as a part of each aircraft’s experimental suite, thus giving insight into the crash severity and airframe deformation which occurred for each test [1].

Composite Fuselage Impact Testing and Simulation: A Model Calibration Exercise

Results from a model calibration study of a composite fuselage front frame test article subjected to impact loading are presented. The effort, undertaken over a 2 year time period, involved both modal and impact testing of the front frame section of a composite fuselage test article. Data from both types of tests were used with multi-dimensional calibration metrics to assess model adequacy. Specifically, two metrics are used: (1) a metric to assess the probability of enveloping the measured displacement during impact, and (2) an orthogonality metric to assess model adequacy between test and analysis. Because the impact test is destructive, vibration test data were also collected for model assessments in terms of modes of vibration. To justify the use of vibration data for calibration of the impact model, the paper discusses how to assess the relevancy of vibration data for calibration of impact models. Finally, results from the impact test are discussed and compared to model predictions and model uncertainty bounds.