Delta Rocket’s Key Position In American Space Effort

Press, Volume CI, Issue 29900, 14 August 1962, Page 8

Delta Rocket’s Key Position In American Space Effort

The Thor-Delta rocket is finding its way into the news with increasing regularity. Teistar and Tiros, Echo and Ariel are all satellites that have been boosted into orbit with precision and reliability by the three-stage Thor-Delta rocket combination. Weighing 50 tons at liftoff and a little more than 90ft tall, the Delta (as it is called for short) is small compared with giant rockets such as the Saturn. Even so. its capacity to place a quarter-ton payload into orbit 300 miles above the earth makes it a very useful vehicle. Originally intended as an interim vehicle until bigger and better rockets became available, the Delta has, by its outstanding performances, won its way into a key position in America’s space effort. In the recent blaze of publicity after the historic television relays by the Teistar satellite there was little mention of the rocket that made the achievement possible. To perform most effectively. Teletar had to be placed in an orbit 600 miles above the earth at its closest distance (perigee) and 3500 miles at its furthest point (apogee). The orbit also had to be inclined a t an an gle of 45 degrees to the Equator. The Delta rocket which launched the Teistar fulfilled every requirement. It nudged the Teistar into an orbit which ranged from 589 miles, to 3502 miles (errors of only 11 and two miles respectively) and which was inctoed 44.8 degrees to the Equator. Such precision is almost like holing-in-one at golf, except that it happens more often with the Delta. Only Failure Reliability is another virtue of the Delta. Only the first launching failed—an Echo attempt before Echo I. From Echo I to Teistar it has launched 10 satellites without any failures. As early as last October the National Aeronautics and Space Administration was so impressed by the Deltas reliability that a contract was signed with the maker, the Douglas Aircraft Company, for 14 more in addition to the original 12 ordered. Recently the number of additional vehicles was increased to 28—all to be launched within the next 18 months. This success story shows that the Americans are mastering the complex techniques involved in the firing of large multi-staged rockets and have learned much during the last five years. The Delta is a direct descendant of the capricious Vanguard rocket, which was designed purely as a satellite launcher and had no military role. The Vanguard was successful in only three of its 11

flights, but the three successful payloads were inserted into earth orbits whose. combination at height and permanence has only recently been bettered. Improvements to the Vanguard upper stages led first to the Able vehicles—the Tbor-

Able and the Atlas-Able—-and further experience led to the design of the Delta. The first stage of tfte Delta is the well-known I’hor intenmediate range ' ballistic missile. Its single rocket motor burns kerosene and liquid oxygen, and develops almost 80 tons of thrust for a burning time of 160 seconds. During this time the vehicle is accelerated to a speed of around 7000 miles an hour at a height of 40 miles—the actual figures depend on the weight of pay load and the angle of climb. Second Stage The second Delta stage is a nodified and improved Vanguard second stage. It employs highly concentrated ti.ric acid plus a hydrazine compound as its propellants, and bums for 109 seconds, ’he motor produces three

tons and a half of thrust—enough to lift the second and third stages to a height of 100 miles and give them a speed of about 12.000 milea an hour. The two stages then coast to the perigee height of the intended orbit, where the third stage and payload separate from the second stage. The third stage, a solid-propellant rocket adapted from the Vanguard third stage, then fires and accelerates the payload to orbital speed. This injection speed ranges between 16,000 and 23.000 miles an hour depending on the size and shape of orbit required for the payload. The next Delta firing will probably send a new communciations satellite, Relay L into orbit. Like the Teistar. the Relay will be used to link the old world and the new by television and telephone. Unlike the privately sponsored Teistar the Relay satellite has been developed as a United States Government venture to prove the feasibility of world-wide satellite communication links. Ultimrnately a network of 30 or more Teistar and Relay satellites will be established—and each one will require a Delta launching rocket, unless multiple launchings by larger rockets are adopted. Other Delta launches due before the end of this year include two more of the famous Tiros weather satellites and further flights of scientific payloads. These may include another orbiting solar observatory to study the sun, another satellite similar to Explorer XII, which counted the energetic atomic particles abounding in space, and a new satellite designed to measure the density and composition of the outermost reaches of the earth's atmosphere. Last but not least, the Delta will attempt to place a satellite in a so-called stationary orbit sometime late this year. This difficult feat has never yet been tried, and calls for superb accuracy on the part of the launching rocket and tracking equipment. The satellite, known as the Syncom. will orbit the earth ait a height of 22,600 miles, completing one revolution every 24 hours. It will therefore keep pace with the earth’s daily rotation and stay constantly above the same region of the globe. The Syncom’s coverage will extend over a full third of the earth and it has long been held that three such satellites would provide the cheapest world-wide television service.