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Aviation History
1964
1964 - 1710.PDF
FLIGHT International, 4 June 1964 947 APOLLO IN ORBIT THE sixth Saturn I launch vehicle was successfully launched byNASA from Cape Kennedy on May 28. The main purposeof the flight was "to qualify the launch vehicle further and develop the technology necessary to build the more powerful Saturns needed for manned lunar landings and other space explora- tion." The vehicle carried into Earth orbit a boilerplate model of the Apollo spacecraft. An active guidance system was used for the first time to steer the second stage and its attached Apollo craft into an orbit of 109-142 miles above the Earth. Weight of the combined satellite vehicle was 37,3001b. The previous Saturn launching (SA-5) placed 37,7001b in orbit on January 29. Specific primary missions of the May 28 flight (SA-6) were to test propulsion, structure and flight control systems and the technique for separating the first and second stages. Secondary objectives were to determine structural characteristics of the launch escape system, operational suitability of Atlantic Missile Range ground tracking stations, and launch escape system jettison characteristics; and to demonstrate the compatibility of the spacecraft research and development instrumentation and communication systems with the launch vehicle systems. In the first four Saturn firings only the booster stage was live. Flight SA-5 was the first to have a powered second stage. As with SA-6, later vehicles in the series will carry unmanned models of the Apollo command and service modules. The last three Saturn I flights (SA-8, SA-9 and SA-10) will carry meteoroid detection satellites. Flight Sequence After ignition the SA-6 vehicle was held to the launch pedestal until all engines were operating smoothly. Lift-off normally occurs about 3sec after ignition. The vehicle was fired on an azimuth of 90°, but after the first few seconds rolled into its flight azimuth of 105°. The tilt programme began after 15sec of flight. The rocket continued to tilt until 134sec, when it was inclined at 67° from the launch vertical. About 70sec after lift-off the rocket passed through the region of maximum dynamic pressure (max Q), when the aerodynamic pres- sures exerted on the rocket's structure are greatest. This occurred about 3.5 miles in range and 7.5 miles in altitude from the pad. Soon after lOOsec a critical series of actions began concerning the separation of the two stages and the ignition of the S-IV second stage. The steps were as follows:— (1) At 107sec, S-IV engine hydrogen pre-start flow begins, lasting 41sec (until S-IV start-up). (2) At 134sec the first-stage propellant level switches, which sense a low level of propellant and initiate the liquid oxygen pre-start flow in the S-IV, are armed. (3) At 138sec S-IV lox pre-start flow begins. (4) The inboard engines are cut off at 140sec and the outboard engines are cut off by an automatic timer 6sec later. At S-I out- board engine cutoff the vehicle is travelling at about 5,900 m.p.h. at an altitude of about 43 miles and a range of about 56 miles. (5) Within 2sec, the following sequence takes place: the four solid-propellant ullage motors of the S-IV begin their 3-4sec firing; separation command is given and the explosive bolts attaching the two stages are fired; the instrument unit control rate gyro signals are introduced into the S-IV control system; the four solid-pro- pellant retrorockets of the S-I first stage begin their 2sec firing period; and the S-IV stage engines are ignited (1.7sec after the separation signal) about 148sec following lift-off. Some 12sec after stage separation, the launch escape tower and the S-IV ullage motor cases were jettisoned. Active guidance em- ploying thCST-124 platform, used for the first time on SA-6, was scheduled to start about 16sec after S-IV engine ignition. The guidance system determined continually during flight the most effi- cient steering commands to result in the required conditions for in- sertion into orbit. The S-IV engines were to operate for about 475 src- At that time, 10.5min after lift-off, the S-IV with the instru- ment unit and unmanned Apollo attached went into orbit. At insertion, the SA-6 satellite was travelling at about 16,500 m.p.h. Insertion occurred about 1,300 miles downrange from the launch site. The Satellite The length of the orbiting vehicle is 80ft, slightly less than half the length of the complete vehicle at launch. The payload was not separated from the second stage and instrument unit, and no recovery was planned. The orbiting body and weights of components include:— Spent S-IV stage .. ... ,. ... .. 14,2001b Instrument unit .. .. .. .. .. 6,1001b Payload (Insert/adapter, Apollo command module and service module) .. .. .. 17,0001b Total 37,3001b Initially the orbiting body was expected to carry an additional 1,7001b of residual propellant in the S-IV stage which would gradually evaporate. The satellite has an orbital period of 88.55min and may tumble slowly during its estimated one-week lifetime. When the satellite is in sunlight and the viewer in shadow, it was expected to be easily visible from Earth, at about the magnitude of Venus. A Minitrack transmitter in the instrument unit was operating on a frequency of 136.65OMc/s. The system included one battery which should assure operation for the vehicle's lifetime. The telemetry system was expected to operate through one orbit, providing signals which were to be tracked by a number of ground stations. The SA-6 flight was used as a test of the major ground tracking networks of the USA. NASA, the Department of Defense and the Smithsonian Astrophysical Observatory were to take part in a global ground tracking exercise, co-ordinated by NASA's Goddard Space Flight Center. Early quick-look tracking and data reduction General arrangement of the Saturn SA-6 launch vehicle and payload
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