AND TERMINAL BALLISTICS A REPORT PREPARED FOR THE AAF SCIEN'rIFIC ADVISORY GROUP By D. P. MAC DOUGALL Naval Ordnance Laboratory, Washington, D. C. N. M. NEWMARK Department oj Civil Engineering, University oj Illinois • PMblished May, 1946 by HEADQUARTERS AIR MATERIEL COMMAND PUBLICATIONS BRANCH, INTEJtJYiE~9) '1001 WRIGHT FIELD, DAYTON, OHIO V-46579 The AAF Scientific Advisory Group was activated late in 1944 by General of the Army H. H. Arnold. He se­ cured the services of Dr. Theodore von Karman, re­ nowned scientist and consultant in aeronautics, who agreed to organize and direct the group. Dr. von Karman gathered about him a group of Ameri­ can scientists from every field of research having a bearing on air power. These men then analyzed im­ portant developments in the basic sciences, both here and abroad, and attempted to evaluate the effects of their application to air power. This volume is one of a group of reports made to the Army Air Forces by the Scientific Advisory Group. Thil document contolnl Information affecting the notional defenle of the United Statel within the meaning of the Espionage Ad, SO U. S. C., 31 and 32, 01 amended. Its tronsmiulon or the revelation of Its contents In any manner to on unauthorized person II prohibited by low. AAF SCIENTIFIC ADVISORY GROUP Dr. Th. von Karman Director Colonel F. E. Glantzberg Dr. H. L. Dryden Deputy Director, Military Deputy Director, Scientific Lt Col G. T. McHugh, Executive Capt C. H. Jackson, Jr., Secretary CONSULTANTS Dr. C. W. Bray Dr. A. J. Stosick Dr. L. A. DuBridge Dr. W. J. Sweeney Dr. Pol Duwez Dr. H. S. Tsien Dr. G. Gamow Dr. G. E. Valley Dr. 1. A. Getting Dr. F. L. Wattendorf Dr. L. P. Hammett Dr. F. Zwicky Dr. W. S. Hunter Dr. V. K. Zworykin Dr. 1. P. Krick Colonel D. N. Yates Dr. D. P. MacDougall Colonel W. R. Lovelace II Dr. G. A. Morton Lt Col A. P. Gagge Dr. N. M. Newmark Lt Col F. W. Williams Dr. W. H. Pickering Major T. F. Walkowicz Dr. E. M. Purcell Capt C. N. Hasert Dr. G. B. Schubauer Mr. M. Alperin Dr. W. R. Sears Mr. I. L. Ashkenas Mr. G. S. Schairer LAYOUT & ILLUSTRATION Capt M. Miller Capt T. E. Daley ii TABLE OF CONTENTS Part I - Pages 3 to 37 inclusive, has been deleted. Page Part II - Properties of High Explosives Introduction and Summary .........•.........••.' ......•••••........•.... 41 General Discussion •••.•••.•.•......•.....••..•...........••••...•....•• 43 Solid Explosives. • . • . • . • • . • . .. 47 Solid Explosive Mixtures .............................•......••...... 49 Aluminized Explosives ...............................•........•... " 5 1 Liquid Explosives .•.•.....•...................•..........••••.•••••.•••. 53 Quantitative Comparison ...•.•.•.................•....••.•....••........ 55 Table I ....•••...•.••.•.......••............•..••••••••••.....•......... 57 Table II ............•.•••..•••...........' ..........••.•..•.••.•••.•••••. 58 Part III - Terminal Ballistics and Destructive Effects Summary •••........•....•...............................•••••••••....... 61 Means of Producing Damage. • . • • • . • • . • . • • • • • . • . .. 61 Basic Physical Principles ...•..•...............•....•..•...•..•••.••... " 62 Impact and Penetration ..•.........................•....•...•.•••.... 62 Fragmentation. • . • . • . • . • . • • . • . • . • • • . • • • • • • .. 63 Blast in Air. • . • . • • . • • . • . • • • • . • . • . •• 66 Blast in Earth or Water .......•.......................•.•......••.••. 69 Debris ..•.•...•..•.........•••...•................•.••••...•..•••••. 71 Fire, Chemical Actions, etc.. • . • . • • • . • . • . .• 71 Classification of Targets •...•••......•.••..•...........•••••....••••••••• 73 Types of Existing Weapons. • • . • . • . • . • • . • • . • . • . • . .. 74 Factors Influencing Selection of Weapons for Attack .•.....••••.•••..•.•.. 75 Getting Weapons to the Target ...................................... 75 Countermeasures ....••...•.•.•...............•• ; ..........••.•.....• 75 Fusing ..•............•..••.•............................•••••.••.•.• 76 Major Uncertainties. • . • . • . • . • . • • . • • . • • • . • .. 76 Present Status of Weapons Selection .•...••...••••..........•...••.•. 76 Future Needs ...•••••..••.••.••..••••...••.......••.....••••...••••••••• 77 iii PART II PROPERTIES OF HIGH EXPLOSIVES By D. P. MacDOUGALL sF $ PART II PROPERTI ES OF HIG H EXPLOSIVES 3 APRIL 1945 INTRODUCTION AND SUMMARY The purpose of this report is to give a brief summary of the present status of our knowledge concerning the properties and utilization of military high ex­ plosives. Attempts are also made to give estimates concerning the behavior of several mixtures and compounds which are not now in use, but might be considered for use in the future. This report does not contain a thorough discussion of the terminal. ballistics of explosive-loaded munitions. However, this subject is discussed briefly in order to provide a basis for comparison of different explosives. Particular attention is paid to the performance of high explosives in blast bombs, partly because this phase is probably of most interest to the Air Forces, and partly because the action of ex­ plosives in producing blast has been more thoroughly investigated than other types of action. Of the explosives in military use today, HBX or desensitized Torpex appears to be the best all round filler for bombs. A bomb loaded with HBX will produce an area of destruction about 45 % greater than that from the same bomb loaded with TNT. On the other hand, HBX is sufficiently stable and insensitive to shock to be used in G.P. Bombs. If, in the future, conditions arise which permit the use of explosives of much greater shock sensitivity than TNT (for filling some sort of robot bomb, perhaps), the best bet, if the comparison is made on a volume basis, would appear to be an explosive of the Torpex type, but with a larger percentage of aluminum. One might hope to achieve, with such an explosive. a damage area twice that of the same volume of TNT. If the weight, rather than the volume, of explosive is chosen as the basis for comparison, the most effective explosive would be a stoichrometric mixture of liquid hydrogen and liquid oxygen. This mixture might give a damage area four or five times as great as that produced by the same weight of 'fNT. Because of the low density however, this mixture would not be very effective on a volume comparison. There is some discussion in the report of SBX, by which is meant an explosive consisting entirely of a fuel (plus a small amount of conventional H.E. to give dis­ persion) and which utilizes atmospheric oxygen in the detonation reaction. Since 41 V.46579 only the fuel must be carried, the amount of enes-gy liberated per unit weight is, in general, large compared with the value for a conventional high explosive, where, in a sense, both the fuel and the oxygen are carried together. The analysis given in the body of the report suggests that gasoline, used as SBX, might put somewhat over twice as much energy into the blast wave as the same volume of TNT. On a weight basis, the comparison is even more favorable to the SBX. However, experi­ ments with SBX have shown that while it is effective in confined spaces, it is very in­ effective in the open. This is probably due to a slow reaction between the fuel and the oxygen of the air, which may be overcome in the future. This is a subject which might generously repay future investigation. 42 GENERAL DISCUSSION There are many jobs which a high explosive may be called upon to do, and there is not now, and probably never will be, a single explosive which is best for all uses. The properties desirable in the explosive used as the filler of an armor-piercing shell are different from those required for the filling of a depth charge, and a de­ molition explosive must meet still other requir~ments. In the present discussion, most attention will be paid to explosives which can be used as fillings for aerial bombs, both because such explosives are of greatest interest to the Air Forces, and because, on a tonnage basis at least, they are the most important. Even in a single type of muni­ tion, such as a general purpose bomb, the explosive produces damage by at least three different methods, air blast, fragments, and earth shock. It is not necessar~ly true that a given '!xplosive is equally effective in producing all three types of damage. In selecting an explosive for a particular munition, therefore, it is important to have available information concerning its effectiveness in the specific type of action in­ volved. A high explosive is a material which can be induced, at a predetermined time and place, to explode or detonate. In the process of detonation the explosive is con­ verted rapidly, in a period of a few microseconds, into a large amount of gas at a high temperature and pressure, with the release of a large amount of chemical energy. An explosive must therefore be a material of controlled stability. If it is too stable, it will be impossible to make it explode, while if it is not stable enough, it may ex­ plode before one is ready for it to do so. Due to its latent instability, every explosive can be made to decompose, with varying degrees of violence if heated sufficiently. However, if the material is to be of practical utility, it must not undergo appreciable decomposition during extended periods of storage at temperatures which might be encountered in magazines, storage depots, holds of ships, etc. An explosive which does undergo such decomposition during storage is undesirable because