February 2006 

NASA/TM-2006-214278 

ARL-TR-3753 

 

Dynamic Crush Characterization of Ice 

Edwin L. Fasanella and Richard L. Boitnott 

U.S. Army Research Laboratory 

Vehicle Technology Directorate 

Langley Research Center, Hampton, Virginia 

Sotiris Kellas 

General Dynamics Advanced Information Systems, Hampton, Virginia 
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February 2006 

NASA/TM-2006-214278 

ARL-TR-3753 

 

Dynamic Crush Characterization of Ice 

Edwin L. Fasanella and Richard L. Boitnott 

U.S. Army Research Laboratory 

Vehicle Technology Directorate 

Langley Research Center, Hampton, Virginia 

Sotiris Kellas 

General Dynamics Advanced Information Systems, Hampton, Virginia 
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National Aeronautics and Space Administration or the U.S. Army. 
1

Dynamic Crush Characterization of Ice 

Edwin L Fasanella and Richard L. Boitnott, US Army Research Laboratory 

NASA Langley Research Center 

Sotiris Kellas, General Dynamics 

Abstract 

During the space shuttle return-to-flight preparations following the Columbia accident, 

finite element models were needed that could predict the threshold of critical damage to 

the orbiter’s wing leading edge from ice debris impacts. Hence, an experimental program 

was initiated to provide crushing data from impacted ice for use in dynamic finite 

element material models. A high-speed drop tower was configured to capture force timehistories of ice cylinders for impacts up to approximately 100 ft/s. At low velocity, the 

force-time history depended heavily on the internal crystalline structure of the ice. 

However, for velocities of 100 ft/s and above, the ice fractured on impact, behaved more 

like a fluid, and the subsequent force-time history curves were much less dependent on 

the internal crystalline structure. 

Background 

In Chapter 11 of the Columbia Accident Investigation Board (CAIB) report [1], which 

was released after the space shuttle Columbia Accident, recommendation 3.3-2 requested 

that NASA initiate a program to improve the impact resistance of the shuttle orbiter wing 

leading edge. The second part of the recommendation was ...“determine the actual 

impact resistance of current materials and the effect of likely debris strikes.” In addition, 

recommendation 3.8.2 states, “Develop, validate, and maintain physics-based computer 

models to evaluate Thermal Protection System (TPS) damage from debris impacts. 

These tools should provide realistic and timely estimates of any impact damage from 

possible debris from any source that may ultimately impact the Orbiter. Establish impact 

damage thresholds that trigger responsive correction action, such as on-orbit inspection 

and repair, when indicated. ” 

Consequently, to comply with the spirit of the CAIB recommendations, a team from 

NASA Glenn Research Center (GRC), NASA Langley Research Center (LaRC), and 

Boeing was given the following task: to develop a validated finite-element model of the 

Orbiter wing leading edge capable of accurately predicting the threshold of critical 

damage from debris including foam, ice, and ablators for a variety of impact conditions. 

Since the CAIB report was released, the team has been developing LS-DYNA models of 

the reinforced carbon-carbon (RCC) leading edge panels, conducting detailed material 

characterization tests to obtain dynamic material property data for RCC and debris, and 

correlating the LS-DYNA models with data obtained from impacts tests for both smallscale flat panels and full-size RCC flight hardware panels [2-6]. Foam impacts onto 

RCC panels were examined first. Once the RCC thresholds for foam impacts were 

determined, attention was directed to ice debris. 
2

 

Ice presents one of the more serious debris impact threats to the space shuttle orbiter 

thermal protection systems. Ice that forms on the space shuttle external tank (ET), if 

dislodged during flight, can impact orbiter tiles or the reinforced carbon-carbon wing 

leading edge. Since the entire tank is covered with insulating foam, typically only a thin 

harmless frost occurs under most conditions. However, the fuel lines have bellows and 

brackets where it is very difficult to prevent hard ice formation. During the space shuttle 

Return-to-Flight (RTF) program, finite element models of the shuttle Orbiter wing 

leading edge RCC panels were developed that could predict the threshold of critical 

damage from both foam and ice debris. Since the debris may strike the orbiter at high 

velocity, dynamic material characterization of the debris was required for input into the 

finite element material models. After dynamic models for foam impacts were developed 

and validated [7], a search of the literature showed a scarcity of work has been performed 

in characterizing ice for high velocity impacts. Consequently, dynamic ice testing was 

begun at LaRC to determine the force-time histories and derived compressive stressstrain curves of clear, hard-ice specimens impacted at near constant velocity and hence at 

near constant strain-rates. 

The threshold of damage to debris impacts for TPS tiles was determined primarily by a 

large number of impact tests using air guns to generate the required impact velocity. 

These tests covered the likely range of impact conditions, debris types, sizes, and 

velocities. Since TPS tile are relatively inexpensive and easily made, a large test program 

was feasible. However, full-scale wing leading edge RCC panels are very expensive, 

difficult and very time consuming to produce, and only a small number of spare panels 

exist. Consequently, the threshold of RCC panels to debris impacts were determined by a 

combination of testing along with validated dynamic finite element analyses. 

The sprayed on foam insulation (SOFI) that impacted and critically damaged Columbia 

had a density of approximately 2.0 pcf. Clear ice has a density of approximately 56 pcf. 

Materials such as foam and ice with relatively low density (as compared to metals, for 

example) are rapidly decelerated in the atmosphere after dislodging. Hence the shuttle 

orbiter can build up a very large relative velocity with respect to these low-density 

materials depending on the size and mass of the debris and the distance from the release 

point to the impact point. Velocities of foam can reach 2500 – 3000 ft/s, while the 

maximum velocity of ice can reach 1000 ft/s. 

The static strength of ice is difficult to measure experimentally and depends highly on 

directional crystalline structure and the direction of loading relative to the internal 

crystalline structure. Details on static material properties of ice can be found in a review 

paper by Schulson [8]. The dynamic material characterization of ice including strain-rate 

effects presented numerous challenges. A given ice specimen can have a complex 

crystalline structure, in which individual crystals can be very small, large, or a mixture of 

sizes with various orientations. A given ice specimen could be a single crystal, or if the 

freezing process is directional, the ice specimen could be composed of a series of parallel 

columnar crystals. Since ice is a difficult material to work with, strain-rate dependent 

data on ice for high velocities was nearly non-existent. Also, the material published in 
3

the literature has in some cases been contradictory. Some researchers express the opinion 

that ice strengthens at high strain rates, while other researchers have indicated that the 

strength decreases. 

Ice on the external tank can form on fuel-line brackets or bellows as hard, clear masses or 

as icicles. Also, small particles of hard ice may form inside large regions of frost on the 

external tank from the cycles of melting and refreezing. This ice would be difficult to 

detect, but could pose a hazard if released at a point far enough away from the wing 

leading edge to result in a large impact velocity. Pre-liftoff inspections would detect and 

mitigate most large pieces of ice. However, cameras have detected ice inside the fuel-line 

bellows several minutes after launch. 

Ice Test Method 

Impact testing of ice cylinders was conducted using the bungee-assisted drop tower at 

LaRC to accurately measure the impact force time-history for low velocity impacts and to 

investigate strain-rate effects by measuring the effective stress-strain curves of the 

crushing ice for different, near-constant velocity loading rates. This ice characterization 

work was performed to provide data for a dynamic LS-DYNA ice material model for use 

in shuttle RTF impact studies. Specifically, the ice model after validation was to be used 

to predict the threshold of ice impact damage to RCC wing leading edge panels. Since ice 

is a very brittle material, a compressive wave moves through the ice from the impact 

point and shatters the ice. It was postulated that as the velocity of the ice impact 

increased, the crystalline structure might become less and less important. 

The LaRC drop tower provides accurate load measurements versus time and since the ice 

is not shot ballistically, the ice is not damaged prior to impact. In addition, the angle of 

impact is closely controlled except for a possible small misalignment angle between the 

drop head and the top of the ice specimen. The drop tower was configured in the 

intermediate strain-rate testing configuration. This configuration was very successful in 

measuring foam strain-rate effects. Thus, three load cells (see Figure 1) were placed 

below the load platform to measure the impact force of the ice. This method allows 

measurement of both the initial peak force and the subsequent lowered force after the ice 

shatters and becomes a more fluid substance consisting of multiple small snow-like 

particles. 

Figure 1. Load platform supported by three load cells removed from drop tower. 
4

Dynamic Ice Crushing Data 

LaRC Fabricated Ice

Initial ice tests were performed with ice fabricated at LaRC. Polyurethane foam molds 

with a plastic cylindrical insert were used to form the LaRC ice in a freezer, as shown in 

Figure 2. Good clear ice cylinders had an average density of about 56 pcf. Cylindrical 

specimen sizes that were constructed by this method at LaRC were 2.8-in diameter x 1.5-

in long and 1.6-in diameter x 1.5-in long. The crystalline structure of the ice and the 

orientation of the crush axis to the crystalline structure are both very important to the 

static crush strength. 

 Figure 2. Mold used to make ice cylinders at LaRC. 

The enclosed bungee-assist drop tower at LaRC was environmentally cooled for ice 

impact testing. Both air conditioning and dry ice were used to cool the tower and a band 

saw (Figure 3) that was used to cut the LaRC-produced ice cylinders into equal length 

samples. Lead stops were used to arrest the drop head and to prevent overloading the 

three load cells that support the ice specimen (Figure 4). 

Figure 3. Drop tower and band saw in enclosed environmentally cooled chamber. 
5

Figure 4. Ice specimen before impact. Lead stops are on each side of the specimen. 

Two series of tests were performed at a strain-rate near 100/s. The impact velocity for 

these tests is approximately 13 ft/s. For all cases, the engineering strain-rate was 

computed from: 

d/dt (ε) = d/dt (Δl/l) = v/l 

which is approximately v0/l0

where l0 is the original length of the ice, and v0 is the initial impact velocity. This 

approximation is reasonably accurate for small strains. Since the ice is brittle and breaks 

up almost immediately upon contact, the strain to failure is small. This first series 

consisted of 18 identical tests of LaRC produced ice cylinders, 1.6-inches in diameter and 

1.5-in high. The stress-strain curves obtained are shown in Figure 5. The average 

strength was 741 psi, and the standard deviation was 355 psi. The density of the clear ice 

was approximately 56 pcf. The highest strength recorded was 1400 psi, the lowest below 

200 psi. Note that the “effective” strains (up to 3% for the fundamental pulse) computed 

as the change in length of the ice column over the initial length are large since the ice 

continues to load the platform even after the ice breaks up. This effective dynamic strain 

is much, much larger than the static failure strain. The strain at maximum stress is 

generally less than 2%. As the ice breaks up, the grains of ice flow over each other and 

create contact between grains that produces a residual strength after brittle failure. In 

other words, the ice particles behave as a fluid, which can support a dynamic pressure 

load. 

Lead

Stops 

Cylindrical

Ice Specimen 

Load 

Platform 
6

Figure 5. Stress-strain curves for LaRC fabricated ice samples with diameter of 1.6-in for 

an average loading rate of 107/s. (impact velocity approximately 13 ft/s) 

Figure 6. Stress-strain curves for LaRC fabricated ice samples with diameter of 2.82-in 

for impact velocity of 13 ft/s. (average strain rate of 105/s) 

A second series of 20 impact tests was conducted using LaRC ice of 2.8-in. diameter and 

1.5-in. high. The average strength was 780 psi with a standard deviation of 240 psi. The 

highest strength recorded was about 1325 psi, the lowest around 350 psi. The stressstrain curves for this test series are shown in Figure 6. 

Although the peak stress is about the same for both specimen diameters, the peak force 

depends on the surface area. Thus, the peak force for the 2.82-in diameter ice is over 
7

three times the peak force for the 1.6-in. diameter ice. Force-versus-time curves are not 

shown, but were generated for all impacts. 

Vendor Supplied Ice Specimens: 

Next, for consistency within the program, ice was procured from IceCulture, the same 

commercial ice sculpture vendor that GRC had used for their ice ballistic impacts against 

a load cell. The GRC ballistic tests were at higher velocities than could be achieved in 

the drop tower. Ice cylinders from IceCulture were purchased and shipped overnight to 

LaRC from their plant in Ontario, Canada. Ice was obtained only from this one vendor to 

help control the natural variation of ice mechanical properties. Twenty-five 3.0-in. in 

diameter and 2.0-in. long ice specimens were received from IceCulture in July 2004. A 

total of 75 ice specimens with 1.5-in. diameter and 2.0-in. long were received from 

IceCulture, 25 in July 2004, and 50 in August 2004. The ice obtained from IceCulture 

was clear, near “perfect” ice and many of the specimens were single crystals. All tests on 

the IceCulture ice were performed using the same drop tower configuration at LaRC as 

was previously described for the LaRC produced ice tests 

The first tests were dynamic crush testing of the IceCulture ice samples with 3-in. 

diameter and 2.0-in. height. This ice had an average peak crushing strength of 994 psi 

with a standard deviation of 241 psi. The tests were performed at an impact velocity of 

approximately 17 ft/s with an average strain-rate of 104/s. The average density of the ice 

was 56.7 pcf. The maximum peak dynamic crushing stress measure was almost 1500 psi, 

the minimum was about 625 psi as shown in Figure 7. 









  





























































































































































































































































































-500 

0

500

1000

1500

0 2 4 6 8 10 12 14

Canadian Ice Samples, D=3.0", H=2.0"

Load Cell Stress, Psi

Strain, %

Average Rate = 104/s

Ave. Ult. = 994 psi ( σ = 241 psi)

Ave. Stiffness = 107.8 Ksi (s = 38 Ksi)

Figure 7. Stress-versus strain curves for commercial 2-in. high ice specimens with 3.0-in, 

diameter loaded at an average strain rate of 104/s. 
8

The second series of IceCulture specimens were cylinders 1.5-in. in diameter and 2.0-in. 

high. The strain-rates of these impact tests at approximately 18 ft/s and 49 ft/s were 

107/s and 295/s, respectively. As shown in Figure 8, the average peak crushing strength 

at the strain-rate of 107/s was 752 psi with standard deviation of 460 psi. One specimen, 

likely a single crystal, reached a peak stress of 2175 psi. 













 











































































































































































































































 -500

0

500

1000

1500

2000

2500

0 2 4 6 8 10 12 14

Canadian Ice Samples, D=1.5", H=2.0"

Average Rate=107/s

Stress, Psi

Strain, %

Aver. Ult. Stress = 752 ± 460 psi

Aver. Stiffness = 77918± 69460 psi

Figure 8. Stress-versus strain curves for commercial ice specimens with 1.5-in diameter 

loaded at an average strain rate of 107/s. 













 























































































































































































































































-500

0

500

1000

1500

2000

2500

0 2 4 6 8 10 12 14

Canadian Ice Samples, D=1.5", H=2.0"

Average Rate=295/s Stress, Psi

Orig Strain, %

Aver. Ult. Stress = 1007± 330 psi

Aver. Stiffness = 47906± 18942 psi

Figure 9. Stress-versus strain curves for 1.5-in. diameter specimens impacted at 

approximately 40 ft/s with an average strain rate of 295/s. 

Identical 1.5-in. diameter by 2.0-in. high specimens were tested at a strain-rate of 295/s. 

The average peak stress was 1007 psi with a standard deviation of 330 psi. The resulting 

stress-strain curves are shown in Figure 9. For this test series, there is statistically an 
9

increase in peak stress for identical sized specimens with strain-rate. The failure stress 

was found to increase with strain rate for thin ice samples under compression in a 

Hopkinson bar as reported by Shazly [9]. The compressive failure stress was found to 

vary from 2900 psi at a strain rate of 90/s to 4930 psi at a strain rate of 882/s. 

 

Professor Erland Schulson at Dartmouth University, who evaluated ice specimens for 

NASA [10], determined that ice obtained from IceCulture can be either a single crystal or 

multiple columnar crystals. Schulson determined the static strength of single crystal ice 

may be as high as 2175 psi, while the strength of the multiple crystal ice can range from 

870 to 1305 psi. These values are consistent with the observed dynamic data. 

High-speed Crush Testing at 100 ft/s

From examining the ballistic data generated at GRC, the crystalline structure of the ice at 

higher impact velocities appeared to have a much smaller effect than for low velocity 

impacts. To examine this observation, the drop tower configuration and the lead stops 

were optimized such that impacts of 100 ft/s could be tolerated without damaging 

equipment or instrumentation. At 100 ft/s, the structure of the ice, initial cracking, etc, 

was expected to have a much smaller effect; however, orientation effects probably still 

existed. Therefore, the angle of impact between the drop head and the top surface of the 

ice was kept as small as possible. A series of three 100 ft/s impact tests were conducted 

onto 1.5-in. diameter x 2-in high specimens from IceCulture. Plots showing the force 

time history for these three tests are shown in Figure 10. The average strain-rate for these 

tests is 578/s. The corresponding stress versus strain curves for these impact tests are 

shown in Figure 11. 



















 



















































































































































































































































































-500

0

500

1000

1500

2000

2500

3000

3500

-0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

#21, 97fps

#23, 97fps

#24, 96fps

Load Cell Force, lbs

Time, ms

Figure 10. Force time history curves from 100 ft/s impacts onto ice specimens 1.5-inch 

diameter x 2.0-in high performed in Langley bungee-assisted drop tower. 
10

When the stresses in Figure 11 are compared with the average stresses in Figures 8 and 9, 

additional evidence for an increase in strength with strain-rate is apparent. However, 

inertial effects also must be considered. 









  







































































































































































0

500

1000

1500

2000

0 5 10 15 20

Canadian Ice Samples, D=1.5", H=2.0"

Average Rate = 578/s

Load Cell Stress, Psi

Orig Strain, %

Figure 11. Engineering stress vs. strain plot for force time histories shown in Figure 10. 

High Speed Video Data

Frames from high-speed videos showed that the ice specimen breaks up into snow size 

particles upon first contact with the drop head at velocities near 100 ft/s (Figure 12). This 

response is very similar to the behavior observed in the 200+ ft/s ballistic impacts 

conducted at GRC. In contrast, at impact velocities of 10 - 40 ft/s (Figure 13), the ice 

fractured into relatively large fragments upon contact with the drop head. The force 

time-histories for the lower velocities were very dependent on whether one corner of the 

ice was contacted first (weak shear behavior), on whether there was initial cracking that 

promoted shear behavior, and on the internal crystalline structure of the ice. Between 40 

ft/s and 100 ft/s the ice apparently changes its dynamic fracture behavior. For impacts of 

ice onto the shuttle, impacts at low velocity most likely will be influenced by the 

structure of the ice. However, most impacts will likely be in the range greater than 100 

ft/s where the exact microstructure of the ice should have only a secondary effect. 
11

Figure 12. Sequential ice deformation after impact in drop tower at 100 ft/s. 

 Figure 13. Ice just after contact with drop head moving at 11 ft/s (left). 

Large ice particles are formed for low velocity impacts (right). 

Rate Sensitive Finite Element Material Model Development for Ice Impacts 

A search of the literature for finite element models of ice impacts uncovered work by 

Kim and Kedward [11] on hail impacts simulated by DYNA3D, the public domain 

version of LS-DYNA [12]. Although their ice material model worked well for their 

purpose, spherical ice impacts onto a composite plate at relatively low velocities, an 

attempt to use their elastic-plastic ice model for cylindrical ice impacts onto flat RCC 

panels did not produce good results. Consequently, a rate-sensitive plasticity material 

model for ice with failure was developed by Carney et. al. [13] for use in determining the 

threshold of ice impact damage to the shuttle Orbiter RCC wing leading edge. 

This material model 155 was developed for use in modeling ice in the LS-DYNA 

Eulerian formulation. The new material model keyword designation in the production 

LS-DYNA version 971 code is *MAT_ PLASTICITY_ COMPRESSION_ TENSION_ 

EOS. The ending “EOS” indicates that an equation of state is used in the model. The 

isotropic elastic-plastic material model allows unique yield stress versus plastic strain 

curves for both compression and tension. When either the plastic strain or pressure cutoff 

values are exceeded, the deviatoric stresses are scaled, allowing a solid to fluid transition. 
12

Rate effects on the yield stress can be modeled by a Cowper-Symonds strain-rate model 

or by user defined load curves that scale the yield stress of the compression and tension. 

Material rate effects that are independent of the plasticity model can also be included. 

The data generated from the dynamic crush testing of ice at NASA LaRC for velocities 

up to 100 ft/s along with data obtained from ballistic impacts of ice at GRC onto load 

cells were used to calibrate the new ice material model in LS-DYNA. 

Concluding Remarks 

In the shuttle return-to-flight preparations following the Columbia accident, finite 

element models were needed that could predict the threshold of critical damage to the 

orbiter’s wing leading edge from impact of ice debris. Hence, an experimental program 

was initiated by NASA to provide crushing data from impacted ice for use in dynamic 

finite element material models. A high-speed drop tower was configured to capture force 

time-histories of ice cylinders for impacts up to approximately 100 ft/s. At low velocity, 

the force-time history and resulting stress-strain curves obtained from dynamically 

crushing ice depended on the complex internal crystalline structure of the ice. However, 

for velocities of 100 ft/s and above, the ice fractured on impact, behaved more like a 

fluid, and the subsequent force-time history curves were much less dependent on the 

internal crystalline structure. The data generated from the dynamic crush testing of ice at 

LaRC for velocities up to 100 ft/s along with data obtained from ballistic impacts of ice at 

GRC onto load cells were used to calibrate the new ice material model in LS-DYNA.

References 

1. Gehman, H. W., et al, “Columbia Accident Investigation Board,” Report Volume 1, 

U. S. Government Printing Office, Washington, DC, August 2003. 

2. Carney, K., Melis, M., Fasanella, E., Lyle, K, and Gabrys, J., “Material Modeling of 

Space Shuttle Leading Edge and External Tank Materials for Use in the Columbia 

Accident Investigation.” Proceedings of 8th International LS-DYNA User’s Conference, 

Dearborn, MI, May 2-4, 2004. 

3. Melis, M., Carney, K., Gabrys, J., Fasanella, E., and Lyle, K., “A Summary of the 

Space Shuttle Columbia Tragedy and the Use of LS-DYNA in the Accident Investigation 

and Return to Flight Efforts.” Proceedings of 8th International LS-DYNA User’s 

Conference, Dearborn, MI, May 2-4, 2004. 

4. Gabrys, J., Schatz, J., Carney, K., Melis, M., Fasanella, E., and Lyle, K., “The Use of 

LS-DYNA in the Columbia Accident Investigation.” Proceedings of 8th International LSDYNA User’s Conference, Dearborn, MI, May 2-4, 2004. 

5. Lyle, K., Fasanella, E., Melis, M., Carney, K., and Gabrys, J., “Application of NonDeterministic Methods to Assess Modeling Uncertainties for Reinforced Carbon-Carbon 
13

Debris Impacts.” Proceedings of 8th International LS-DYNA User’s Conference, 

Dearborn, MI, May 2-4, 2004. 

6. Kellas, Sotiris, “Quasi-Uniform High Speed Foam Crush Testing Using a Guided Drop 

Mass Impact.” NASA CR-2004-213009, April 2004. 

7. Fasanella, Edwin L., Jackson, Karen E, Lyle, Karen H., Jones, Lisa E., Hardy, Robin 

C., Spellman, Regina, Carney, Kelly S, Mellis, Matthew E, and Stockwell, Alan E. 

“Dynamic Impact Tolerance of Shuttle RCC Leading Edge Panels Using LS-DYNA.” 

AIAA-2005-3631, AIAA Joint Propulsion Conference, Tucson, AZ, July 10 – 13, 2005. 

8. Schulson, E. M., “Brittle Failure of Ice.” Engineering Fracture Mechanics, 68, 

pp1839-1887, 2001. 

9. Prakash, V., Shazly, M, and Lerch, B., “High strain rate compression testing of ice.” 

NASA TM-2005-213966, 2005. 

10. Iliescu, D., Schulson, E. M., and Fortt, A., Characterizations of ice for return-toflight of the space shuttle. Part I Hard Ice. NASA CR-2005-213643, 2005. 

11. Kim, H. and Kedward, K. T., “Modeling Hail Ice Impacts and Predicting Impact 

Damage Initiation in Composite Structures.” AIAA Journal, 38 (7), p1278-1288, 2000. 

12. Anon., “LS-DYNA Keyword User’s Manual – Version 970,” Livermore Software 

Technology Company, Livermore, CA, April 2003. 

13. Carney, Kelly S., Benson, David J., DuBois, Paul, and Lee, Ryan, “A 

Phenomenological High Strain Rate Model with Failure for Ice.” Submitted to 

International Journal of Solids and Structures, 2006. 
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

2. REPORT TYPE 

Technical Memorandum

 4. TITLE AND SUBTITLE

Dynamic Crush Characterization of Ice

5a. CONTRACT NUMBER

 6. AUTHOR(S)

Fasanella, Edwin L.; Boitnott, Richard L.; and Kellas, Sotiris

 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

NASA Langley Research Center U.S. Army Research Laboratory

Hampton, VA 23681-2199 Vehicle Technology Directorate

 NASA Langley Research Center

 Hampton, VA 23681-2199

 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001 and

U.S. Army Research Laboratory

Adelphi, MD 20783-1145

 8. PERFORMING ORGANIZATION

 REPORT NUMBER

L-19225

10. SPONSOR/MONITOR'S ACRONYM(S)

NASA

13. SUPPLEMENTARY NOTES

An electronic version can be found at http://ntrs.nasa.gov

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified - Unlimited

Subject Category 16

Availability: NASA CASI (301) 621-0390

19a. NAME OF RESPONSIBLE PERSON

STI Help Desk (email: help@sti.nasa.gov)

14. ABSTRACT

During the space shuttle return-to-flight preparations following the Columbia accident, finite element models were needed that

could predict the threshold of critical damage to the orbiter’s wing leading edge from ice debris impacts. Hence, an

experimental program was initiated to provide crushing data from impacted ice for use in dynamic finite element material

models. A high-speed drop tower was configured to capture force time-histories of ice cylinders for impacts up to

approximately 100 ft/s. At low velocity, the force-time history depended heavily on the internal crystalline structure of the ice.

However, for velocities of 100 ft/s and above, the ice fractured on impact, behaved more like a fluid, and the subsequent

force-time history curves were much less dependent on the internal crystalline structure.

15. SUBJECT TERMS

Ice; Debris; Impact damage; Space Shuttle; Wing leading edge

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