WEIGHT OF STORED ENERGY

33' NOTES.

this energy pulsation in the second rhumbatron which produces the current oscillations of the circuit. Frequency is determined predominantly by the dimensions of the apparatus.

An output of 500 watts at 40 centimeters, and of around 100 at 10 centi- meters, is reported. Wavelengths are often discussed glibly and handled familiarly, but waves in the order of centimeters represent oscillation fre- quencies so high as to challenge the imagination. Ten-centimeter waves, for example, correspond to an alternating current frequency of three billion cycles per second. Grandfather's clock ticked off the seconds during a life- time of 90 years to a total of about 2,840,000,000 oscillations of its pendulum. I t would be necessary to crowd all of these movements into the space of one second in order to have the pendulum frequency equal that of the current in the rhumbatron circuit.

To what uses such high-frequency power may be put perhaps cannot be fully predicted. Hitherto the necessary power generator has been lacking, so that little has been done by way of application in the arts and sciences. Where extremely short waves have already proven their value, the power need is ready to be filled. An instrument-landing control system uses short waves as an airplane glide path, and this use for the klystron has been successfully tested. I t has been stated that in the waveband range from one centimeter to one meter there is room for some 270,000 non-interfering signal frequencies. Although the distance attainable in this range would be limited to the horizon, a transmitter located on a tall building in the center of a city and using the one centimeter to one meter band could reach as many receivers as there are telephones in a city of about 1,000,OOO population. The waves are, however, deflected and disturbed by buildings and other obstacles. The extremely short waves may be highly focused with a minimum of equipment, thus concentrating their power. As in the recently announced absolute alti- meter for airplanes, these focused beams may be useful for the location of large obstacles in both aerial and marine navigation.

The new oscillators are not seriously restricted in size and ultra-high- frequency power measured in kilowatts may become an actuality. This possi- bility re-opens the question of applying induction effects to uses previously excluded because sufficient power could not be obtained a t the requisite high frequencies. Many materials normally considered to be electrically non- conducting respond to high-frequency electric fields ; there is an absorption of energy with a direct conversion to heat within the body. A t the present time, applications of this sort are being made up to the highest frequencies which have been readily available. Fever machines (for induction therapy), an injection molding machine in which the plastic charge is rapidly and thor- oughly heated by induction, and a proposal for the rapid and distortionless drying of green ceramic bodies are examples. Such heating is expensive, but in special cases the cost is reasonably low for the advantages obtained. Active interest in this field suggests much to be done with electrons dancing to the beat of the rhumbatron.

- W E I G H T OF STORED ENERGY.-An abstract appearing in Mechani-

cal Engineering, November, 1939, published by the American Society of Mechanical Engineers, 29 West 39th Street, New York, N. Y.

An article by Vernon H. Grant, Bureau of Aeronautics, Navy Department, appearing in Product Engineering for September, 1939, attempts to evaluate the various forms of stored energy in terms of weight in connection with

332 NOTES.

WEIGHT-ENE RGY CONVERSION FACTORS Container Total

Weight, weight, weight, Ib pcr kwhr Ibpcrkwhr Ibpcrkwhr TYpc

Gasoline. ..................... HI gas sphere.. ................. H2 as cylinder.. . . . . . . . . . . . . . . . H2 fiquid.. ..................... Cartridge. ...................... Dry battery. ................... Storage battery 10 hr) ........... Compressed air (100 psi). . . . . . . . Compressed air 500 psi). . . . . . . . .

Compressed air (pm psi). . . . . . . .

Steel, tcnsion or compression.. . . .

Storage battery $3 rnin). . . . . . . . . .

Compressed air $I- psi). . . . . . . . Flywheel (not including hub and

web). ........................ Rubber.. ....................... Stccl, spring.. ................... -

0.18 0.06 0.06 0.06 2.78

45-65 I08 480 181

104 I28 93

301 1290

1475- 443-

0.02 1.92 2.97

2.78 0.12

...

. . .

... 6001 4m1 2731 zoo1

...

...

...

...

0.20 1.98 3 .Of 0.18 5.56

480 88 I

6 q 40' 293

302 =I90

147100 443-

4 5 3

1 Container weights based upon spheres, cylinders are 11/* to z times as heavy.

the study of auxiliary power in airplanes. The author says that suggestions often advanced involving energy storage, while possibly not completely fantastic, are still so far from the optimum designs obtainable that a fresh start, based upon more sound concepts of relative weights, is usually neces- sary. I t is with the latter object in mind that he has studied the different sources of power and compiled the following table in terms of the electrical unit pounds per kilowatt hour, since electricity is usually considered as the primary means for distributing auxiliary power.

- STATIC ELECTRIC HAZARDS ON BOARD OIL TANKERS.-

An article by George F. Prussing, Safety Engineer, Union Oil Company of California. Reprinted in the July, 1939, issue of the Pacific Marine Review, San Francisco, Calif. Originally published in the May, 1939, issue of Marine Safety.

When any liquid flows through pipes or hose or through the air from one vessel to another, static electricity is generated. This in itself is not dangerous unless it can accumulate on some object that is thoroughly insulated from the ground or from the vessel from which the liquid is being discharged. If the liquid is a conductor of electricity, such as water, there is little chance of accumulation Petroleum being a non-conducting liquid does not permit the charges to &cape through it. If accumulation takes place on an insulated object, such as a bucket or tank being filled, or even a bucket floating on the surface of a tank, this accumulation becomes dzardous in the presence of an explosive mixt+e when the accumulated statlic charge is allowed to jump as a spark to some other object.