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These experiments did not produce any apparent changes in the organism of the animals. Although the animals were subjected to surges of more than 5 G's and prolonged weightlessness during the free fall they appeared to be in good condition after landing (R. 3, 4, 8, 43).

During the second series of experiments, dogs were sent aloft in individual space suits made of rubberized cloth with transparent plexiglas helmets. Each dog had 3 bottles of oxygen (about 900 liters) which was enough for a twohour period. The programing mechanism, parachute, and oxygen supply, together with the dog in its suit were placed on special “catapult carts." In this assembled state each cart weighed about 70 kg. (R. 8, 33).

At an altitude of 110 km. the rocket nose separated from the body and began a free fall. The nose was then allowed to fall some 20 or 30 km. until it attained velocities of about 2,500 km. per hour. At this point (some 89-90 km. elevation) the first “catapult cart” was shot out by means of an explosive charge which gave the cart a velocity of 700 m/sec. and subjected the dog to 6 G's. The whole process took about 0.2 sec. After 3 seconds the parachute opened and the dogs begin a parachute descent which takes about an hour from an altitude of 75-85 km. (R. 2, 8, 33).

The second "cart” was ejected by a similar charge at an elevation of 35-40 km. when the nose of the rocket was falling with a velocity of 1,000–1,150 m/sec. In this case the parachute was timed to open at an altitude of only 3-4 km. (R. 3, 8, 33).

Instruments for automatic recording of reactions of the animals in flight, free fall and parachute descent were placed on the “catapult carts." The instruments recorded the breathing rate, pulse, body temperature, and the maximum and minimum blood pressure. A pressure of 440 mm. of Hg. was maintained within the space suits in flight (R. 8).

Sometimes a parachute would be carried more than a hundred km. away from the launching site and would require several days to find. To prevent dogs from suffocating, the space suits were equipped with special valves which opened automatically at altitudes below 4 km. Of the twelve dogs used in this series none died from shortage of oxygen, meteorites, cosmic rays, or other factors encountered in the upper air. Still one of the dogs died during its second flight due to a defect in one of the rockets which exploded. Photo films in an armored film holder survived the explosion (R. 8, 33).

Automatic filming process in the rocket prior to catapulting of the “carts" had to be carried out with the aid of a system of mirrors since the limited space in the cabin did not permit the placement of the camera directly in front of the animals (R. 8).

The successful results of operation of the safety system under such varied conditions prove the effectiveness of the space suits, ejection devices, parachuting system, automatic controls, etc. After the above flights were carried out five or six years ago (i. e. 1951-52), other series of tests have been made in which the animals were carried twice as high (i. e. to elevations of 200 to 210 km.) in airtight cabins. Again the equipment and dogs withstood the flights well, showing that we were now ready to begin experimental flight in space (R. 43).

SECTION 5-SPUTNIK I, LAUNCHING AND ORBIT The first Soviet Sputnik was launched on October 4, 1957. It was launched by a specially developed high altitude rocket with a highly effective automatic control system designed to hold the rocket in the required trajectory. The launching rocket started vertically and after a very short time the programing mechanism began a gradual deflection of the rocket axis from the vertical. At the end of the launching trajectory section, the rocket was placed in orbit at a velocity of about 8,000 m/sec. The average elevation of the orbit was about 900 km. After the rocket was in orbit, the nose cone was ejected, the satellite left the rocket and began to move independently (R. 2, 10, 15, 44).

The orbit of the satellite was a rounded ellipse with a maximum elevation of about 1,000 km. It required about 1 hour 35 minutes for it to complete one revolution around the earth. Due to the fact that the orbit deviates about 65° from the plane of the equator means that the rotation of the earth displaces its path by about 24° longitude. The perigee of the orbit is in the Northern and the apogee in the Southern hemisphere. The period of revolution of Sputnik I was decreasing at the rate of about 3 sec. per 24-hour period. This rate of shortening enabled scientists to calculate its probable life span (R. 2, 10, 15, 21, 44).

SECTION 6-SPUTNIK I, CONSTRUCTION AND INSTRUMENTATION The first sputnik is spherical in form. It has a diameter of 58 cm. and a weight of 83.6 kg. Its airtight body is made of aluminum alloys. Its surface is highly polished and specially treated. A large portion of its volume is taken up by the power supply. Its high weight-to-volume ratio implies successful de sign of internal equipment. Before launching, the satellite is filled with gaseous nitrogen. The externally protruding antennas consist of four rods 2.4 to 2.9 meters long. During the launching flight the antenna rods are pressed to the shell of the rocket. After separation the antennas spring into position on their hinges. The nitrogen gas in the satellite is under forced circulation to help maintain an equitable temperature in the interior of the satellite (R. 2, 9, 15, 45).

The satellite is equipped with instruments for measuring the following parameters: atmospheric temperature, pressure, and density; intensity and velocities of primary cosmic radiation, solar X-rays, solar ultraviolet rays; meteors and meteoric dust; degree of ionization and composition of electrically charged particles; and finally, static charges on the surface of the sputnik and loss of nitrogen from the inside of the sphere (R. 1, 2, 6, 7, 9, 23).

According to V. G. Fesenkov, Sputnik I also had photographic equipment. However its purpose was to record instrument readings rather than photograph the surface of the earth (R. 21).

Air pressures were measured by means of ionization manometers which performed so well in high altitude rockets. The intake ports are designed in a way to reduce and correct errors arising from aerodynamic reasons. The composition of air was determined by means of a frequency mass-spectrometer. A dynamic charge meter was used for determination of electric charges on the surface of the satellite. There was also a proposal for setting up instruments in Sputnik I for measurement of the magnetic field of the earth. However it is not clear as to whether it was done (R. 9, 42).

SECTION 7-SPUTNIK II, ORBIT AND STRUCTURE

The second Soviet satellite (Sputnik II) was launched on November 3, 1957. It was placed in orbit by means of a super long-range, multi-stage, ballistic intercontinental rocket. The rocket rose to an elevation of several hundred km. and released Sputnik II with a velocity of about 8,000 m/sec. Its velocity in orbit was determined by means of the Doppler effect. This method can determine velocity with an accuracy of 0.01% according to Prof. S. Khaykin. The orbit is elliptical, with the apogee in the northern hemisphere at an elevation of about 1,700 km. and the perigee in the southern hemisphere at an elevation of about 1,000 km. Its period of revolution around the earth is 103.7 minutes. It performs about 14 revolutions per diem. Sputnik II also rotates or tumbles (end over end) around its own axis. The tumbling motion takes about 20 seconds to complete the cycle (R. 1, 18, 19, 20).

Unlike the first satellite, Sputnik II is simply the last stage of the carrier rocket on which instruments are installed. After the nose cone dropped off, the forepart of Sputnik II was revealed as a frame holding an airtight dog cabin and an instrument sphere. The sphere is identical in shape and size to Sputnik I. It houses power sources, instruments, and a programing mechanism. The cabin and spherical container were both made of aluminum alloys and their surfaces were highly polished. The total weight of the frame, containers, instruments, and experimental animal was 508.3 kg. (R. 1, 20).

SECTION 8-SPUTNIK II, INSTRUMENTATION Sputnik II was designed to supply information on general structure of the ionosphere and to provide data useful for survival in space. The latter was performed by means of an experimental animal. More specifically the second Soviet satellite provided measurement of : primary cosmic rays; solar radiation; atmospheric temperature, density, and pressure; composition of electrically charged particles in ionosphere; meteors and micrometeors; and conditions of radio-wave propagation. It is hoped that these measurements will throw some light on the cause of polar lights, magnetic storms, and other phenomena of the upper atmosphere (R. 1, 7, 10, 23, 39).

Instruments for measurement of solar ultraviolet rays and X-rays were set up on the frame in the nose of the rocket. Instruments for the measurement of cosmic rays were set up on the body of the rocket. Temperature senders were

set up on the external and internal surfaces of the cabin, the instrument container, and individual components (R. 20).

For measurement of the ultraviolet and X-ray radiation Sputnik II is equipped with 3 photoelectric multipliers placed at angles of 120° to each other. Each photomultiplier is equipped with several filters (metallic, organic, and optical) which makes it possible to isolate special ranges of the X-ray spectrum of the sun and the hydrogen line in the high frequency ultraviolet range. Signals from the multipliers are then amplified by radio circuits and transmitted to earth. The significance of using the satellite for this type of measurement is that most of solar ultraviolet and X-rays are absorbed by the atmosphere and cannot be measured from the surface (R. 20).

Since cosmic rays are deflected by the magnetic field of the earth, the degree of penetration varies with the latitude producing the so-called "latitude effect." The satellite, by virtue of passing rapidly from one latitude to another makes an ideal "station” for observing the “latitude effect.” Sputnik II measures not only the amount of total cosmic radiation but also the amounts for each of the major types of energy level. In short, Sputnik II studies changes in energy level composition of cosmic rays at various latitudes (R. 20).

Cosmic radiation is studied by Sputnik II by means of two charged particle counters set at right angles to each other. Pulses from the counters are transmitted to special transitor circuits which record the number of pulses until a certain number is reached, after which a special signal is transmitted to earth. Then the registration of numbers is begun over again and again transmitted when the set number is reached (R. 20).

Instruments were set to function for only 1 week after which the power sources on Sputnik II were used up (R. 20).

SECTION 9—THE PASSENGER IN SPUTNIK II

The airtight cabin for the dog is cylindrical in form. It is made of aluminum alloys and its surface is highly polished. The dog had a supply of food, and equipment for regeneration of air and regulation of temperature. Attached to the dog were instruments for measurement of its pulse beat, breathing rate, arterial blood pressure, and biopotentials of its heart. Other instruments recorded temperature and pressure in the cabin. Air within the cabin was purified by a special chemical air-conditioning system which removed excess humidity and carbon dioxide from spent air and added oxygen to it. Since convection could not take place in a state of weightlessness, the cabin had a system for forced circulation of air. This also served to maintain a uniformity of temperature within the cabin. The dog was provided with automatic equipment for rationing of food and water and for removing body wastes (R. 20, 46).

As in the experiments made with dogs in high-altitude rockets so Laika, which was sent up in Sputnik II, was conditioned over a period of weeks to spend long hours in small airtight cabins with instruments of various types attached to its body. Tests were also made of the dog's ability to withstand vibrations and other unusual conditions. The dog was also subjected to accelerations of several G's. In this respect Soviet scientists feel that solutions lie in proper positioning of the body with regard to direction of acceleration and in the use of special pressure suits to prevent accumulation of blood in the extremities (R. 20, 46).

Although Laika was sent up without a pressure suit, results show that the animal was able to withstand the accelerations and vibrations of rocket flight and a state of weightlessness for 4 days without adverse effects. What is not known is whether the walls of Sputnik II were adequate to protect the dog from cosmic radiation. The answer to this last question can only be obtained by a series of satellites with animals and numerous instruments. Such a series is planned, but conclusive results will be possible only after the reentry problem is solved and the animals are brought safely back to earth for laboratory investigation (R. 20, 46).

SECTION 10-TRANSMISSION OF INFORMATION BY SPUTNIKS Each of the two Soviet satellites was equipped with two 1-watt short-wave radio transmitters. To simplify observations for radio hams, the instruments on the two sputniks were identical and transmitted on frequencies of 20.005 and 40.002 megacycles. The power was sufficient for signals to be received at distances of up to 10,000 km. The external antennas consisted of 4 rods. In

Sputnik I these antennas varied in length from 2.4 to 2.9 meters (R. 2, 11, 15, 20, 21, 44).

Sputnik I had batteries which lasted 24 days. Sputnik II had power sources which lasted only 7 days. In Sputnik I, signals from the two frequencies alternated. The average duration of the signals, on each frequency, lasted on the average about 0.3 seconds. In Sputnik II, signals from the 20.005-megacycle transmitter transmitted at 0.3 sec. intervals but the 40.002-megacycle transmitter was in constant operation. In actual practice the signals lasted from 0.05 to 0.7 sec. in duration and the intervals between signals varied in order to transmit coded information. The code was based on the theory of information, a branch of cybernetics (R. 11, 15, 20, 38, 45).

This code transmits information on pressure, density, chemical structure of the ionosphere, magnetic field of the earth, primary cosmic rays, corpuscular radiation of the sun, ultraviolet and X-ray sections of the solar spectrum, electrostatic fields of the upper layers, and micrometeors (R. 15).

In the cosmic ray studies the relative number of various nuclei are counted. In particular, the study will determine the relative quantity of lithium, beryllium, and boron nuclei, and those with fairly large charges. The equipment carried by the satellites will also serve to study the variation in the total flow of cosmic rays for 12-hour, for 24-hour, and for 27-day periods. (The 27-day period appears to be based on the fact that the Soviets expected the power sources of Sputnik I to last for 27 days. Actually, the power sources lasted for only 24 days.) (R. 15.)

In addition to data received from instruments within the satellites, information can be obtained on position and velocity of the satellites from observation of the Doppler effects at the point of reception. This was obtained by recording on a magnetic tape the change of tone of beats between the frequency of radio waves emitted by the satellite and the frequency of the heterodyne in the receiver. By using extremely stable frequency generators (such as molecular generators) for purposes of comparison, the velocity of the satellite can be determined with an accuracy of up to 0.01 percent (R. 10, 13, 18, 20).

The design of the radio antennas of the satellites makes it possible to determine the rate of rotation of the satellites which does not exceed a few r. p. m. In Sputnik II the tumbling motion requires about 20 seconds to complete the cycle. The rate of rotation is detectable because the antennas of the ground stations are designed to receive linearly polarized signals and a signal attenuation is obtained when antennas of the satellite radiate waves with circular polarization. This arrangement guarantees reception for any attitude of the satellite with the exception of the case where the plane of the satellite antennas passes through the receiving point and is perpendicular to the direction of polarization of the ground antenna (R. 10, 20).

The two sputniks have also provided considerable information on the ionosphere in respect to radio wave propagation. Heretofore, basic information on the ionosphere was obtained by radio waves transmitted from earth and reflected by the ionosphere. Reflections obtained in this manner were chiefly from the lower layers and not from the maximally ionized layers. The upper limit. of the ionosphere could not be determined by this method. The two frequen«ies emitted by the satellite have different refraction angles and this fact has supplied data on the structure of the upper layers which was not previously available (R. 15, 20).

The results obtained with the 15-meter waves show that reception substantially exceeds the area of direct visibility. In some cases reception distances were 10, 12, and even 15 thousand km. Value of information on ionospheric radio wave propagation is further enhanced by the fact that the orbits of the sputniks are eliptical and they pass below, through, and above the F, layer of the ionosphere. When the satellite was above the Fı layer, radio waves penetrated the entire thickness of the ionosphere, bounced off the earth's surface and spread further by single or multiple reflections from the F, layer in areas where its critical frequencies have sufficiently high values.

It also appears that radio waves, incident upon the ionosphere from above at an oblique angle, are refracted to a considerable degree and thus penetrate beyond the line-ofsight distance (R. 19, 20).

When the satellite is below the F, ionization maximum and is approaching the observation point from the sunlit area of the earth, the 15-m. signals arrive at the reception point after successive reflections from the F, layer and the ground. However, after the satellite passes the observation point and proceeds into the unlit area of the earth, the reception is limited to the line-of

sight distance. In a number of cases, unsymmetrical reception pattern was observed. The proximity of the satellite to the F2 ionization maximum is be lieved to create exceptionally favorable conditions for the formation of waveguide channels which carry radio signals over very large distances. There is evidence that along with the satellite signals which have traversed the shortest distance, observation stations sometimes receive signals which have circled the world. This type of radio-echo was picked up on the 15-m. wavelength by Yu. N. Prozorovskiy (one of the most experienced short-wave amateurs of the U. S. S. R.) at 00:07 hours on October 8, 1957, in Moskva (R. 19).

The 7.5-m. signals have been, as a rule, received within the line-of-sight distance. However, 7.5-m. waves can spread beyond the line-of-sight distance due to high critical frequencies of the F2 layer in daytime (R. 19).

SECTION 11-RECEPTION OF SIGNALS FROM SPUTNIKS An exclusive radio monitoring program has been organized in the U. S S. R. In addition to a large number (60 according to one source) of professional radio observation stations equipped with radar and radio direction finders, the U. S. S. R. has a large amateur observation program. The amateur program is centered around some 26 or 28 DOSAAF radio clubs, some of which possess a large quantity of high-quality radio observation equipment. In addition, the satellites were observed by a large number of radio amateurs with the aid of specially built radio receivers. Diagrams of these receivers and of directionfinding attachments have been published in 1957 in various issues of the Soviet magazine “Radio” (R. 10, 15, 16, 21).

In order to receive signals heterodyne receivers have to have a sensitivity of 1-3 microvolts. The 40-megacycle signal is expected to be more reliable so that amateurs are encouraged to use receivers of the 38-40-megacycle frequency of the types described in the periodical “Radio” (R. 11).

Half-wave dipoles as well as loop antennas, of the type used for television, can be utilized for the reception of signals from a satellite. To obtain the necessary directional pattern, the antenna is suspended a quarter wavelength above the ground, or metal roof, which serve as reflectors. Reception is best in the planes perpendicular to the antenna. Since no broad-band characteristic is required from these antennas, the dipoles can be made from tubes or even from soft wire, suspended on two isolating stretcher cables. Ordinary lighting cord may be used as a feeder, but in case of considerable length it is desirable to use high-frequency cable matched to the antenna (by means of a U-bend) and to the input of the received (R. 13).

A simple 300-ohm antenna can be made from the KATV-300 television cable. Antennas must be set up in the North-South direction (R. 13).

SECTION 12-MONITORING PROCEDURE

In order to be of maximum value, observations should be recorded on tape together with the exact time of passage of the satellite. The receiver should be turned on well ahead of time in order to stabilize the oscillator frequencies. An intermittent signal of 0.2- to 1.5-sec. period may announce the approach of the satellite. The signal strength increases gradually to attain a certain maximum and then gradually fades away. The duration of observation may vary from 5 to 15 minutes depending on the sensitivity of the receiver. It is important to record the exact time of the beginning, the peak, and the fading of the signal (R. 13).

Tape recordings of the observation will be especially valuable. If, in addition, the exact time of observation is fixed, the tape becomes an important document to determine the exact time of passage of the satellite over certain points. The time of passage of the satellite nearest to a given point can be determined from the change of strength of the received signal. Maximum signal strength will correspond to the shortest distance to the satellite. Despite its simplicity, however, this method fails to give accurate result due to fadings of the signal in the ionosphere (R. 13).

A much more exact method for determining time of passage is based on the frequency shift due to the Doppler effect. In this case, it is important that the oscillator frequency remain constant within a score of cycles (the frequency of the satellite transmitter being quartz-controlled). To achieve this it would be necessary to stabilize the receiver oscillator frequency by quartz crystal, or by very careful parametric adjustment. It is simpler, therefore, to use a con

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