UPPER ATMOSPHERE.

New Zealand Herald, Volume LXVIII, Issue 20978, 15 September 1931, Page 10

UPPER ATMOSPHERE.

TESTS OF CONDITIONS. WORK FOR AIR MINISTRY. BALLOONS FROM THE DIOMEDE. A series of experiments to determine 1110 strength, direction and other features of currents in the upper atmosphere is at present being carried out by the cruiser Diomode, tlio flagship of the New Zealand Squadron, at tho instigation of the British Air Ministry. The experiments are part of a scheme which is being carried out on every naval station and in all parts of the Empire to furnish accurate data for the Ministry. At 5 p.m. each day this month a large balloon, about 3ft. Gin. in diameter and filled with hydrogen, is released from the cruiser. The rate of climb of tho balloon is 700 ft. a minute, the pressure required to achieve that rate being reckoned by attaching a small weight to the base of the sphere. When the balloon will support the weight the lead is detached and the balloon is freed. The balloons used are of three colours, red, while and blue, tho type chosen depending upon the prevailing conditions each day. Tho chief aim in selecting the colour is visibility. Yesterday, when there was a blue sky with scattered clouds over the naval base, a red balloon was despatched. Apart from the question of visibility another factor which is allowed for in choosing tho colour is tho heat on the day. White is tho best colour for resisting heat, and a whito balloon will float higher on a warm day as tho gas inside does not expand so quickly and the balloon will not burst so soon as one of a darker hue. In a dark balloon tho hydrogen readily expands and soon reaches a far greater pressure than the surrounding .atmosphere, with the result that the envelope bursts too quickly. The usual height attained by tho balloons before they burst is more than 14,000 ft., but owing to tho clouds and other weather conditions their flight cannot always bo followed until they burst. The greatest height at which they can he followed with tho naked eye is less than 4000 ft., hut every minute after their release observations are made with antiaircraft guns, which can be ranged up to an altitudo of 24,000 ft. Ihe balloon's ascent and drift in the wind at the upper altitudes is carefully noted by ranging a gun on it at 60-second Intervals, tho position of tho balloon being plotted out later. The results noted are to bo forwarded to tho Air Ministry at the end of the month. No conclusions will be drawn from these data by the officers in charge of tho experiments locally, the work of correlating and comparing tho data from various Dominions and colonics being in tho hands of officials of the Air Ministry.