PILOT-BALLOON ASCENSIONS AT SEA 



Inst ru me nt s 



Instruments and apparatus used on cruise VII of the 

 Carnegie are described below. Through the courtesy 

 and cooperation of the Division of Aeronautics, U. S. 

 Navy Department, practically everything used in the 

 pilot-balloon work on the Carnegie was loaned for the 

 duration of the cruise. Since it might be desirable to 

 procure the equipment through manufacturers, however, 

 information which might prove helpful in the matter has 

 been included in the notes below. 



Theodolite. --Keuffel and Esser theodolite no. 54005, 

 manufactured according to plans and designs furnished 

 by the Navy Department, was used on board the Carne- 

 gie . Supplied in August 1929, this instrument repre- 

 sented the latest development in aero-theodolites. It 

 was hung in gimbals, with a counterweight, to minimize 

 the effect of the ship's motion. In the work on the Car- 

 negie two features were noted in which improvement 

 might be made. The first was the need for a clamping 

 screw on the lower horizontal plate of the azimuth cir- 

 cle. Such a clamp was part of the equipment of older 

 types of theodolites and would seem to be a permanently 

 desirable feature, since it would permit the "zero" set- 

 ting to be made on true north and would result in azi- 

 muth observations which would be true as read and 

 would not require correction. The second somewhat 

 unsatisfactory feature was the ring constituting the top 

 of the tripod. The diameter of this ring was so small 

 that, for a rolling of the ship of ten degrees or more, 

 the counterweight shaft would strike the ring, sometimes 

 causing the displacement of the instrument in azimuth. 

 On some other ship than the Carnegie the motion might 

 not be great enough to cause the counterweight shaft to 

 strike the ring. 



Sextant. --On board the Carnegie the motion very 

 frequently was great enough to make difficult the read- 

 ing of both altitude and azimuth with the theodolite. To 

 distribute the work, a sextant was utilized for accurate 

 readings of altitude. The theodolite then, was set only 

 roughly on altitude, the major effort being devoted to 

 accurate setting of azimuth. The sextant used on board 

 the Carnegie was made by Plath, of Hamburg, Germariy, 

 type no. 17, serial no. 11730. Type no. 17 is an instru- 

 ment with very large field and an endless drum-vernier 

 which can be read with ease and rapidity. The combi- 

 nation of theodolite and sextant proved a very satisfac- 

 tory arrangement as the motion of the ship did not inter- 

 fere with the sextant readings nearly as much as with 

 the theodolite readings. Therefore, though the balloon 

 might be lost by the theodolite during a period of heavy 

 rolling, the sextant would retain it and, by setting the 

 observed sextant altitude on the theodolite, the balloon 

 often could be picked up again by the latter instrument 

 and the series of observations extended considerably. 



Balloons. --Six- inch and nine-inch balloons in cream 

 or tan-colored pure gum and in black, were furnished to 

 the Carnegie . The six-inch pure gum variety were used 

 almost exclusively. Only when there was a high, white, 

 uniform cirrus formation of clouds could the black bal- 

 loons be used to advantage. Six-inch balloons were used 

 rather than nine-inch, chiefly for economy in the 



hydrogen supply. The ascensional rate of 180 meter s- 

 per-minute, generally used at the land stations in the 

 United States, was used on the Carnegie . There were 

 occasions when a higher rate of ascent would have been 

 desirable, as when large clouds were traveling rapidly 

 or the cloud formations changing rapidly. For such oc- 

 casions the nine-inch balloons, which could be inflated 

 to have an ascensional rate of 250 meters-per-minute, 

 would be preferable. In order that the amount of hydro- 

 gen put into a balloon might be weighed accurately, the 

 inflation had to be performed in one of the laboratories 

 where air currents could not reach the balloon. The lab- 

 oatory door was just sufficiently wide to permit removal 

 of the six- inch balloons, which became 65 centimeters 

 in diameter when inflated, but would not let out the 75 to 

 80 centimeter nine-inch. Future plans would have to 

 take into consideration the need for an inflation room 

 with adequate opening for removing the balloons. Bal- 

 loons were procured from Faultless Rubber Company, 

 Ashland, Ohio, the price for the six-inch being approxi- 

 mately fifty cents each. 



Inflation balance. --The balance is a small device 

 which serves as a valve for admitting hydrogen to the 

 balloon and also serves as a weight for determining the 

 "free lift" of the inflated balloon. Information as to 

 where this might be obtained doubtless could be secured 

 from the Navy Department. The price probably is not 

 great. 



Hydrogen. --The Carnegie was most fortunate in 

 having the cooperation of the Navy Department in the 

 matter of furnishing the hydrogen. One large tank (200 

 cubic feet) is sxifficient to inflate only twenty to twenty- 

 five balloons of the six-inch size and twelve to fifteen of 

 the nine-inch, so that for an intensive program of obser- 

 vations and an extended cruise, a comparatively large 

 number of tanks must be carried. The Carnegie carried 

 six tanks and was able to keep a supply of hydrogen on 

 hand by replenishment at U. S. Naval bases. It was found 

 that some of the larger seaports in the Pacific had no 

 commercial establishments furnishing hydrogen and it 

 would appear, therefore, that unless official cooperation 

 were secured, the problem of maintaining a supply of hy- 

 drogen on an expedition would be an important one and 

 would require considerable advance planning. 



Record forms, plotting board, etc. - -Forms for re- 

 cording observations (Aero 474) and the equipment used 

 for plotting the results were furnished to the Carnegie 

 by the Navy Department. The Navy Department probably 

 would be pleased to furnish information as to where these 

 items could be obtained. Also the book of instructions 

 used by observers on Naval vessels doubtless would be 

 furnished on request. 



Observing Station and Personnel 



Station. --The station should be located on some 

 well-exposed area on the deck where the least restrict- 

 ed view of the full horizon may be had. Also, the loca- 

 tion should be such that the base line may be easily and 

 quickly sighted along for the zero azimuth setting. Two 

 stations were used on the Carnegie , close to the rail, on 



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