The paper preseots thtd seasonal variations and distribution of atmospherio'density in the upper air over Indian region. The study reveals the density gradient has a down slope from North to South during winter and South to North, upto 200 mb level in summer. At 850 mb level the ieopycnir: lines form tl shallow trough over East aoast and at 700 mb level over Bombay-Poona region while over the rest of the country the isopy 'nice show no spacial fcaturea: At 500 mb level there is a well marked trough of density over North Western India. Above 200 mb level an altogether di-'ertmt picture throughout the year is noticed.One of the meteorological parameters which has received scant attention in the field of Indian meteo-. rological literature is the study of upper air density and variations in it in different seasons. It is well known that density is directly proportional to pressure. The latter has been thoroughly investigated and plays a key role in the field of Meteorology. The authors' attention was drawn to the study of density variation in the upper-air of India in the course of studying the variation in thunderstorm frequencies over North India, The mean monthly data given in Normals of Climat-Temp. based on radiosonde data. for the years 1951-65 were used in this study1. The data relate to the mandatory levels, like surface, 850 mb, 700 mb, 500 mb, 300 mb, 150 rnb and 100 mb and those for-14 stations in Indian: sub-continent have been used in this study. T H E O R E T I C A L C O N S I D E R A T I O N SIt is well-known that the density equation p = PIRT is valid for completely dry air. But in the atmosphere water vapour will alway5 be present. Therefore, the total presswe of a parcel of unsaturated air may be regarded as the sum of the partial pressure which would be exelted by the dry air and the water vapour independently.Since the value of gas constant for water vapour is 815 times that of dry air, the density of water vapour is given by the formula p, = 5e/8RT wherein e=vapour pressure in mb. Density of dry air is given by the equation, pd = p -e/ltT. Thus the density of a parcel of unsaturated air or a parcel of mixture of dry air and water vapour can be written as :where p , = density of unsaturated air in gm/m3, R = gas constant, T = tehp in K O and p = pressure in mb.Starting with this generalised form of equation, air densities from surface upto 100 mb level were computed for 14 stations for twelve months. For such computations, the monthly means of pressure,. 31

Attempts have been made to develop a suitable computer code that can find solutions to the axi-symmetric penetration of an Earth Penetrating Warhead yielding complete space-time histories of the resistive force offered by the target medium. The consequent warhead deceleration and velocity reduction, the resulting axial compressive stress developed in warhead casing as the penetration process progresses into the composite target media consisting of hard concrete of specified thickness followed by earth soil have been discussed.

Intercept geometry of target aircraft and missiles play an important role in determining the effectiveness of the warhead. Factors such as fragment spatial distribution profile, damage capabilities, target and missile characteristics have been considered and visualised through computer graphics and optimum intercept angles have been arrived. Computer graphics has proved to be an important tool to enhance perception and conceptual design capabilities in the design environment.

I. It i51 important to unddrstand the internal ballistic processes for the development of regenerative liquid propellant guns (RLPGs). A 30 mm RLPG test fix lure was developed and firing lrials were I conducted to study the perrprmance of the gun. During tIle trials, sometimes, combustion ignition in the reservoir took place resulting in substantial damage to lhe injection piston. This paper hi&hlights I the possible causes of this combustion and offers suggestions. regarding improvement in the design. An \ elaborate instrumentation setup which coold pinpoint the specific conditions leading to failures is i suggesteq. I I including 30, 105 and 155 mm caliber guns with the aim of developing an artillery weaponl-4. Liquid propellant guns offer a variety ot advantages over the conventional solid propellant guns, viz., caseless and insensitive ammunition, simpler logistics, cheaper propellant, and multiple round and simultaneous impact (MRSI) capability. A couple of accidents with the liquid propellant. during the loading process have been reported in literature5.

The performance of flat cone charge cannot be calculated by the well known hydrodynamic equations used for conventional hollow charges. As such, experimental studies have been carried out to evaluate the effects of liner cone angle, liner thickness, explosive charge to liner mass ratio and stand‐off on the penetration performance. Generalized equations are established relating the basic parameters with the performance of flat cone charge. A simplified computerized design approach has been suggested which would be useful to the practical weapon designers.