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Aviation History
1961
1961 - 1044.PDF
146 FLIGHT, 3 August 1961 Ranger /, NASA's most sophisticated spacecraft to date, has been de- veloped by the Jet Propulsion Laboratory, Pasadena, California. In its "cruise" configuration it has a span of 17ft and a height of 13ft, and its 6751b gross weight is made up of 2381b structure, 501b solar panels, 2431b electronic packages and 1441b miscellaneous experiments Missiles and Space flight... spacecraft, and the second a high-gain directional antenna 4ft indiameter at the base of the craft. The two solar panels are each approximately 10 sq ft in area,and each contains 4,340 solar cells. They are expected to pick up enough solar energy to produce 155-210W. Because of the attenuation of solar energy by the Earth s atmos-phere there is uncertainty as to precisely how much solar energy can be collected by the panels and converted into electrical energy.This uncertainty must be resolved before more complicated space- craft carrying solar panels are sent out on different missions, someas far as Venus and Mars, and so one of the experiments on board Ranger 1 includes four specially calibrated cells which will measurethe cells" operating characteristics. The two solar panels are hinged on framework below the hexagon, and in the launch position arecarried in a folded position. In the hollowed-out inner section ot the hexagon is a silver zincbattery weighing 1251b with a capacity of 9,000 Watt-hours. This batterv will provide the power to run the spacecraft prior to the timeof acquisition of the Sun by the solar panels, and also will serve as a back-up power source if the solar acquisition is not successful.The battery will provide enough electrical power to run the space- craft for two days. Before the solar power is available to run the spacecraft, the tworadio transmitters on board will both send data to Earth via the omni-directional antenna. A three-watt transmitter will send on afreauency near 960Mc/s and a separate quarter-watt transmitter will send on a similar frequency. The quarter-Watt transmitter has alifetime of seven days and will stay on the air continuously until its battery is exhausted. Spacecraft Controller Six electronic boxes located on each sideof the hexagonal base contain the electronic intelligence of Ranger 1. One of the most important of these instruments is called the space-craft controller. It is this controller which allows Ranger elec- tronically to calculate when it should perform what function, howit should roll and pitch to find the Sun and lock on to this power source with its solar panels, how to find the Earth and aim itsdirectional antenna at the Earth, and perform many other functions. The spacecraft controller is an electronic solid-state timer. Ittakes 400 cycles per second from the spacecraft power source and divides it into one pulse per second, and uses these pulses as thebasic timing reference. These pulses are accumulated in a storage device, and the unit also contains a memory device which has apre-set series of triggers. When the accumulated pulses match the pre-set count stored inthe memory device, a relay is closed and the controller issues a command for Ranger 1 to perform some specific function. Fromlaunch to the end of its useful life there are ten such commands that the controller must issue: hence there are ten channels and ten 16 The controller timer is started 3min before launch. This time then serves as the reference point for future commands to beissued by the controller. When the spacecraft is turned on, from nower supplied by the large Silver zinc battery inside the hexagon,most of the scientific instruments and both the quarter-Watt and the three-Wait transmitter begin to operate. However some instruments are not turned on, notably the solarcorouscular detectors, and the three-Watt transmitter is given only enoueh power to run at half strength, i.e.. 1.5W. This is done be-cause as the launch vehicle passes through a critical area between 150 000 and 750,000ft, there is a tendency for devices using highvoltase to arc over and damage themselves; hence these are turned on bv the controller after this critical time. During the launch phase of the Atlas-Agena B launch vehicle,the spacecraft is protected against aerodynamic heating by a shroud which covers it. After Atlas cut-off, at approximately*80sec the shroud is jettisoned. At almost the same time that the nrotective shroud is pushed forward by eight spring-loaded bolts,the Agena B separates from the Atlas. At this time, the Agena B pitches down from an attitude almost 15 above the local horizonto one almost level with that horizon. In this horizontal mode, the Agena B fires for the first time and burns for almost 2*min to reach Earth-orbital speed of approxi- mately 18 000 m.p.h". After 2imin of burning time. Agena B shuts down and coasts in a parking orbit for more than 13min until it reaches the optimum point in time and space to be fired for the second time. , MAGNETOMETER ION CHAMBER LYMAN ALPHA TELESCOPE COSMIC OUST DETICTOX ELECTROSTATIC ANALYZER PITCH * ROLL JITS X-KAY SCINTILLATION COUfttERj SPACECRAFT CONTKOUi MEDIUM SNfKGY DETECTORS ELECTROSTATIC ANALYZER H1OH-6AIN ANT In the first Ranger shot, which is not aimed at the Moon, themechanics of this parking orbit are not important, but will serve as a test of the procedure for use in later launches which will be aimedat the Moon. The parking-orbit technique is a means by which the geometry imposed on Moon shots by the location of the AtlanticMissile Range is corrected by using a second-stage rocket as a mobile launching platform in space. Injection of the Agena B and the Ranger 1 spacecraft, still asone unit, occurs approximately over Ascension Island in the South Atlantic Ocean approximately 23min after launch. Up to this time,the events of the launch, separation of Agena from the Atlas, opera- tion of the spacecraft system and ignition, and cut-off times ofAgena B will have been telemetered to ground tracking stations through the Agena B telemetry system. A little more than 2min after injection, the spacecraft is separatedfrom the Agena B, again by spring-loaded bolts. After this occurs. Agena B yaws through 180°, fires a number of solid retro-rocketsand moves into a different and lower trajectory from that attained by Ranger 1. There are two reasons for this manoeuvre. It wouldnot be desirable in later shots for the unsterilized Agena B to follow Ranger on in and to impact the Moon and, if Agena Bclosely followed Ranger, the spacecraft sensory system might mistake reflected sunlight from Agena B for the Sun or the Earth. Ranger 1 is now pointed on a trajectory which will take it out on,a long swing away from the Earth, and the dead Agena B rocket casing is slowed down on an orbit that will move it closer into theEarth's atmosphere, ultimately to burn up by friction. The sequence of the ten commands issued to Ranger 1 by the spacecraft con-troller during the flight is as follows:— First Command. This is issued 25min after the controllerwas started, which was 3min before the launch. This command is to increase the power being sent to the larger transmitter from 1.5Wto 3W. The increased power allows the ground station near Johannesburg more easily to acquire the signal from the spacecraft.The Deep Space Instrumentation Facility station in South Africa also will be able to tell from telemetry from Ranger 1 that thiscommand was issued to the spacecraft by the spacecraft controller. Second Command. This is issued at 35min and turns on the scientific instruments which had previously not been turned on because of the passage through the critical altitude area. Third Command. This is issued at 36min 40sec and performstwo separate functions. The first function is to extend, by means of a compressed spring, the electrostatic analyser package in a smalibox on a small boom about 4ft from the main body of the space- craft. This is done so that the two sensors in the electrostaticanalyser can look at the Sun and away from the Sun at the same time without interference from the body of the spacecraft. Thesecond function of this command is to fire small squibs which pul! out the pins locking the two solar panels. When these pins art-displaced, compressed springs move the solar panels out until the> are at right angles to the length of the spacecraft. This operationtakes about half a minute. Fourth Command. This occurs at 61min 40sec, turns on theattitude control system, and sends power to the Sun sensors, the
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