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Free Flight Hypersonic Erosion and Ablation Measurement System

Description:

TECHNOLOGY AREA(S): Materials 

OBJECTIVE: Develop a capability to measure volume loss on test articles traveling at speeds ranging from 5,000 to 18,000 ft/s. 

DESCRIPTION: Technologies are needed for measuring the volume loss due to erosion or ablation of test articles traveling at speeds from 5,000 to 18,000 ft/s. For example, volume loss could be determined from surface geometry measurements at two stations along the flight path. Obtaining ablation and/or erosion data during high speed material testing that has a moving test article is a critical for the development of hypersonic weapon systems. High speed ballistic ranges and sled facilities have been used extensively to perform erosion and ablation studies on the performance of re-entry vehicle (RV) materials. Historic methods of measuring ablation/erosion at discrete test stations used high speed photography systems located along the test sample flight path. Cameras opposed to the flight line were used at several locations to obtain images of the ablated or eroded test sample. Significant effort was required to calculate the geometry loss using these images, and uncertainty was high. For facilities such as the Arnold Engineering Development Complex (AEDC) Range G (light gas gun) and the Holloman High Speed Test Track, methods were developed to recover test samples in order to overcome these difficulties and improve understanding of material response. Because these facilities have long test lengths (1,000 ft and 10,000 ft, respectively), the ability to understand non-linear effects through the use of multiple instrumented stations is still limited by the photographic measurement techniques. Recent advances in laser scanning, holography, and photogrammetry technologies should enable more accurate methods for obtaining geometry measurements of test samples. Laboratory investigations of holography systems show the capability of point measurement resolution below 3 micrometers (0.0012”) and potential for hypersonic applications. Innovative concepts using these or other technologies are sought for measuring three dimensional changes in geometry with a spatial resolution on the order of 0.001” for each dimension. Test samples in the ballistic range can reach surface temperatures greater than 2500 °F. Analysis software should perform volume comparisons to determine the volume loss on the surface and output three dimensional models of the test sample surface for comparison with computer modeling and simulation results. Expectations for Phase I include a feasibility demonstration of scanning the surface of cylindrical and conical shaped objects up to 1” in diameter x 1” in length. The object should be moving at velocities greater than 2,000 ft/s, possibly a projectile fired from a rifle. The spatial resolution of the scanned object should be demonstrated in a laboratory using an objective surface of less than 0.005”. Phase II should provide two fully operation prototype systems for measurements at two separate measurement stations along the path of the test article. The prototype systems should be capable of scanning the test articles used with the Range G 3.3” launcher at a threshold spatial resolution of 0.001” for each dimension, and should include a software for processing of the data obtained between the two stations so that comparisons of test sample erosion and ablation can be provided after the test The prototype system should be demonstrated in an environment similar to that of AEDC Range G that uses a facility guided 3.3” diameter track and recovery system. The demonstration/validation test article should be similar to an AEDC legacy RV nose-tip model containing a sample up to 3” in diameter with a length under 2”. The test article should be recovered and compared to measurements made using the prototype system. 

PHASE I: Demonstrate the feasibility of scanning cylindrically shaped objects up to 1” in diameter at spatial resolutions on the order of 0.001” (for each spatial dimension) at a velocity greater than 2,000 ft/s. 

PHASE II: Develop two prototype systems capable of measuring the shape of test objects in a large ballistic range at a 0.001” spatial resolution per dimension and velocities ranging from 5,000 to 18,000 ft/sec. 

PHASE III: Develop a portable system than can be easily installed at AEDC Range G or the Holloman sled track. Test article size should be increased to objects above 8” in diameter and over 8” long with the same .001” per dimension measurement resolution. 

REFERENCES: 

1: Development of an Aeroballistic Range Capability for Testing Re-Entry Materials, Journal of Spacecraft, Vol 12, May 1975

2:  Boundary-Layer Transition on Large-Scale CMT Graphite Nosetips at Reentry Conditions, AEDC-TR-79-45

3:  Development of a high-speed ballistic holography camera for field experiments, SPIE Vol. 5210

4:  A Novel Holographic Technique to Record Front-Surface Detail from a High Velocity Target, NASA SP-299

5:  AEDC-TR-77-98 - AEROBALLISTIC RANGE/TRACK PHOTOGRAPHIC INSTRUMENTATION DEVELOPMENT, available from DTIC with no login credentials required (added on 12/15/17).

KEYWORDS: Laser Scanner, Holography, Photogrammetry, High Speed, Erosion, Ballistic Range, Sled, Holloman, AEDC Range G 

CONTACT(S): 

Marshall Polk 

(931) 454-5965 

edward.polk.1@us.af.mil 

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