1、c 4 m 4 z SELF-SEALING STRUCTURES FOR CONTROL OF THE METEOROID HAZARD TO SPACE VEHICLES atzd James J. Piechocki 1 NATIONAL AERONAUTICS AND SPACE ADMiNiSTRAiiOW k“SH!GTON, D. C. OCTOBER 1964 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SELF-SEALING
2、 STRUCTURES FOR CONTROL OF THE METEOROID HAZARD TO SPACE VEHICLES By Philip J. DAnna, Roger M. Heitz, and James J. Piechocki Distribution of this report is provided in the interest of information exchange. Responsibility for the contents resides in the author or organization that prepared it. Prepar
3、ed under Contract No. NASr-102 by NORTHROP SPACE LABORATORIES Hawthorne, California for NATIONAL AERONAUTICS AND SPACE ADMINISTRATION For sale by the Office of Technical Services, Department of Commerce, Washington, D.C. 20230 - Price $2.75 Provided by IHSNot for ResaleNo reproduction or networking
4、permitted without license from IHS-,-,-FOREWORD This Summary Report was prepared by Northrop Space Laboratories, Hawthorne, California, under NASA Contract NASr-102. The contract is administered by the Office of Advanced Research and Technology, Structures Research Group, Space Vehicle Division, wit
5、h Mr. Norman Mayer as Project Monitor. Principal authors of this report are P. J. DAhna and Dr. R, M. Heitz, Co-Principal Investigators, and J. J. Piechocki, all of Space Materials Laboratory; Dr. R. D. Johnson, Laboratory Head. Other contributors to this program include R. K. Jenkins, R. W. Hunter,
6、 J. K. Hagill, Dr. B. Arden, Dr. A. Caron and T. W. Brown of the Space Materials Laboratory, R. Hornung of NSL Structural Analysis Branch, M. Garman of Northrops Nortronics Division and Prof. G. V. Bull of McGill University. This summary report, written in two parts, describes performance of the per
7、iod from 1 April 1963 through 31 March 1964. Part I reports the re- sults of the program related to self-sealing panels and their evaluation. Shock wave damage control was found to be essential to obtaining effective sealing, particularly in the chemically activated self-sealing panel configurations
8、, Part I1 reports the results from an investigation and development of shock wave damage control techniques under conditions resulting from high velocity particle penetration into liquid-filled compartments. In addition, Part I1 includes the results ot an investi- gation of the mechanical and chemic
9、al phenomena associated with high velocity particle penetration into fluid-filled compartments. has been classified Confidential. Part I1 This report is documented at Northrop Space Laboratories as NSL 62-132-7 (Part 1). iii Provided by IHSNot for ResaleNo reproduction or networking permitted withou
10、t license from IHS-,-,-TABLE OF CONTENTS SECTION PAGE . 1.0 INTRODUCTION AND SUMMARY 2.0 COMPARATIVE EVALUATION OF SELF-SEALING CONCEPTS . 2.1 2.2 Conclusions and Recommendations 3.0 TECHNICAL DISCUSSION AND ANALYSIS . 3.1 High Velocity Particle Penetration Into Compart- ments Containing Nearly Inco
11、mpressible Medfum 3.2 Perforation of Composite Structures 3.3 Material Selection and Evaluation 3.4 Temperature Dependence of Self-sealing Capability 4.0 EXPERIMENTAL PROGRAM 4.1 Equipment and Testing Procedure 4.2 Mechanical Self-sealing Concepts . Summary of Test Results 4.2.1 Elastomer Sphere Con
12、cept 4.2.2 Fiber Mat Concept . Concepts . 4.3.1 RTV Silicone Elastomer/Fiber Mat or Rubber Spheres or Air Gap Concept Rigid Silicone FoamIFiber Mat or Rubber Spheres Concept . Flexible Silicone Foam/Fiber Met or Rubber Spheres Concept . 4.3.4 Silicone Foam/Balsa Wood Concept 4.3.5 Elastomeric Sphere
13、s/Viscous Face Concept 4.3.6 Rigid Silicone Foam/Air Gaps Concept 4.3.7 Rigid Silicone Foam/Rubber Spheres/Air Gap Concept . 4.3 Combined Mechanical and Chemical Self-sealing 4.3.2 4.3.3 1 6 6 16 20 20 25 29 56 60 60 65 65 71 73 73 81 89 93 100 102 105 V Provided by IHSNot for ResaleNo reproduction
14、or networking permitted without license from IHS-,-,-TABLE OF CONTENTS PAC E 5.0 REFERENCES . 107 APPENDIX A - STATE OF MATERIAL SUBJECTED To IMPACT SHOCK A- 1 SECTION - Vi Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-LIST OF ILLUSTRATIONS FIGURE
15、3- 1 3- 2 3- 3 3-4 3-5 3-6 3-7 3-8 4- 1 4-2A 4- 2B 4- 3 4-4 4- 5 4- 6 4- 7 4-8 4- 9 4- 10 4-11 4- 12 Ruptured Honeycomb Core-Elastomer Panel Ruptured Aluminum Panel (Wafer-Filled Tank) Approximate Solution of Shock Pressure in Chemical Compartment Combined Concept-Rigid Silicone Foam or RTV 60 Silic
16、one Elastomer/Fiber Mat or Rubber Spheres Concept - Configuration Polyurethane Foam + Fiber Mat Concepts Combined - Configuration Combined Concept - Rigid Silicone Foam/Fiber Mat Concept - Configuration Balsa Wood/Silicone Foam Concept Rigid Silicone Foam/Air Gaps Concept - Configuration Northrop Pa
17、rticle Accelerator Northrop Corporation-Light Gas Gun Facility (Vacuum Chamber 1 Northrop Corporation-Light Gas Gun Facility Gun Facility for Ballistic Testing of Heated and Cooled Targets in a High Vacuum Sel f -Sea ling Panel-E las tomer Sphere Concept PAGE 21 22 24 33 47 52 53 54 61 63 64 66 68 P
18、unctured Elastomer Sphere Self-sealing Panel Configuration 69 Fiber Mat Panel Configuration 72 Combined Concept-RTV Silicone Elastomer/Fiber Mat 74 Concept Configuration Combined Concept-RTV Silicone Elastomer/Rubber Spheres 77 Concept -Conf iguration RTV Silicone Elastomer/Air Gap Concept 79 Ruptur
19、ed Aluminum Faced Self-sealing Panel (RTV Silicone 80 Elastomer/Air Gap Concept) Self-sealing Mechanism-Rigid Silicone Foam/Fiber Mat Concept Combined Concept-Rigid Silicone Foam/Fiber Mat Concept 84 85 vii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS
20、-,-,-LIST OF ILLUSTRATIONS PAGE 87 - Combined Concept-Rigid Silicone FoadRubber Spheres Concept-Configuration Combined Concept-Flexible Silicone Foam/Rubber Spheres Concept Configuration Spheres Concept Combined Concept-Flixible Silicone Foam/Fiber Mat Concept-Configuration 90 Self-sealing Mechanism
21、-Flexible Silicone Foam/Rubber 91 92 Balsa Wood/Silicone Foam Concept 94 Internal Foaming in Panel B-1 95 Internal Foaming in Panel B-4 98 Elastomer Spheres/Viscous Face Concept-Configuration I 101 FIGURE 4-13 4-14 4-15 4-16 4-17 4-18 4-19 4-20 4-21 4-22 4-23 Elastomer Spheres/Viscous Face Concept-C
22、onfiguration 103 I1 Rigid Silicone Foam/Air Gaps Concept-Configuration 104 Combined Concept-Rigid Silicone Foarn/Rubber Spheres/ 106 Air Gap-Configuration viii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-LIST OF TABLES PAGE - 2-1 Comparative Eval
23、uation of Self-sealing Panel Concepts 7 4-1 Summary of Calculations 99 LIST OF ILLUSTRATIONS FOR APPENDIX A FIGURE A-1 Analytical Model of One-Dimensional Impact Conditions Graphical Solution to Impact Problems A-2 A-3 Shock Solution: Two-Layered Target PAGE - A- 2 A- 6 A- 6 ix Provided by IHSNot fo
24、r ResaleNo reproduction or networking permitted without license from IHS-,-,-1.0 INTRODUCTION AND SUMMARY The recent limited findings from satellite experiments, although con- firming the existence of a “meteoroid environment,“ have not as yet resolved the various conflicting opinions concerning the
25、 exact nature of the environment or the magnitude of its hazard to space vehicles. However, it is generally agreed by most investigators that, due to their extremely high velocities, meteoroids do present a real hazard to manned space vehicles, particularly those destined for long duration missions.
26、 Among techniques proposed or minimizing this hazard , the bumper shield or spaced sheet structure concept has been the one most frequently proposed by space vehicle designers. In this concept, the bumper fragments the meteoroid while the resulting spray of particles is hope- fully stopped by the in
27、ner shell. However, although it has been shown that this configuration can be highly effective in preventing the spray of impact induced particles into the interior of a space vehicle compartment, damage to the inner shell by the more energetic meteoroids may be severe enough to cause fluid leakage
28、from pressurized compart- ments. Therefore, although the bumper shield concept may provide adequate protection for limited short duration missions, our proposed self -sealing structures guarantee the sealed integrity of a pressurized compartment, and provide the “faiI-safe“ capability required for t
29、he more ambitious space missions. The implications, therefore, appear obvious-that, for long duration space missions, more reliable techniques than those currently proposed need to be evaluated. With this objective in mind, Northrop has been proposing the philosophy of the self-sealing structure. st
30、ructural concepts have been developed and experimentally evaluated in In pursuance of this approach, various Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-which the best features of the bumper shield concept have been combined with a self-sealing i
31、nner shell to give a system possessing high penetra- tion resistance, shock wave damage control and self-sealing capability. During the first year of effort on this two year program, as summarized in Reference 1, various self-sealing structure concepts were investigated. Out of this initial program,
32、 five successful self-sealing panel configura- tions were fabricated and their self-sealing capabilities experimentally demonstrated by puncturing with 1/8-inch diameter steel and glass spheres at impact velocities to 7,000 fps. Both mechanical and chemically activated evaluated. The principle of op
33、eration of the mechanical concepts depends upon either the mechanical response of elastomer materials in rebounding upon being punctured and sealing the hole, or on the forces generated by the pressure differential across a puncture in a pressurized compartment in drawing a rubber sphere or other se
34、aling element into the hole and effecting a seal. The working principle of the chemically activated concepts depends on the penetrating particle causing the intermixing of two initially separated chemical constituents so that the ensuing chem- ical reaction will cause one of the constituents (an eas
35、y flowing elastomer) to cure and form a solid mass along the pellet entry path and to effect a seal. self-sealing concepts were During the latter part of the first years program, some limiting hypervelocity testing of these initial self-sealing panel configurations was conducted at NASA Ames Researc
36、h Ceilter in an attempt to verify results obtained at 7,000 fps. Detailed results of these tests, which were con- ducted with 1/8-inch diameter glass spheres at impact velocities to 23,000 fps, are given in Reference 1. Initial results from these tests were not completely conclusive in that only two
37、 of the five panels tested were perforated. However, examination of the impacted panels indicated 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-that shock wave effects at these higher velocities increase panel damage and material removal along th
38、e pellet entry path, thereby making it more difEicult to achieve self-sealing action. Based on these initial high velocity tests, it was concluded that those concepts where sealing capability was dependent solely upon the mechanical response of elastomeric materials would not seal at the higher punc
39、turing velocities and, for the other concepts, shock wave damage control would be a primary prerequisite for obtaining successful self-sealing action. In view of this, the second years program was oriented towards obtaining shock wave damage control in those concepts where initial results indicated
40、promise of successful self-sealing action at impact velocities above 7,000 fps. During the past year, the major effort has been directed to the following tasks : 1. Ballistic testing and concept evaluation at impact velocities from I 10,000 to 26,000 fps. I 2. Investigation of techniques for control
41、 of shock wave damage and material removal during high velocity puncturing. techniques were investigated: The following e e Using composite non-metallic face sheets. Isolating the chemical compartments of the chemically activated configurations from the panel face sheets or interposing a highly comp
42、ressible material between the chemical compartment wall and the face sheets. e Incorporating a volume increasing mechanism (e.g., foaming reaction) in those configurations sensitive to material removal. 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,
43、-,-0 Combining the best features of two or more concepts to give greater effective sealing action against the more severe type of high velocity impact damage. The incorporation of one or more of these techniques has resulted in the development of nine basic panel configurations that have successfull
44、y maintained their self -sealing capability when punctured with 1/8-inch diameter steel spheres at impact velocities from 10,000 fps to 26,000 fps. The techniques used for self-sealing the panels are either mechanical (elastomer spheres), chemical (uncured elastomers or foaming resins) or combined m
45、echanical and chemical (elastomer spheres or asbestos fibers plus a chemical system). The mechanical elastomer sphere concept, although not giving complete sealing action (air leakage rate of 1.3 lbs/day for a Ap = 14.7 psi), added the lowest weight to a double wall panel (0.31 lbs/ ft2). The chemic
46、al or combined mechanical-chemical concepts, with the exception of one configuration (see panel configuration I, Table 2-11, gave complete sealing action (zero leakage rate) when tested at impact velocities of 10,000 fps and above. from 1.24 lbs/ft for the Elastomer Sphere-Viscous Face Concept to 3.
47、44 lbs/ f? for the Rigid Foam-Balsa Wood concept. the various self-sealing panel configurations tested is given in Section 2.0 while panel construction details and other phases of the program are given in the subsequent sections. The weight for these concepts varied A comparative evaluation of As an
48、 additional task during this years program, some exploratory experiments were conducted in which water-filled tanks were penetrated with high velocity particles. The purpose of this investigation was to evaluate techniques for preventing explosive rupturing of the penetrated tank wall under ballistic conditions normally creating such failures. Certain techniques have been developed whereby explosive rupturing of water-filled tanks may be prevented for ballistic conditions creating 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without licen
