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Aviation History
1957
1957 - 1815.PDF
6 December 1957 weighing about 1,500 Ib, and the third majorsection contains the guidance package, acces- sible through a large door shown in thedrawing. Prime contractor for guidance is the A.C.Spark Plug division of General Motors, who in July were awarded their definitive researchand development contract, which came to $38m. The system includes an inertial plat-form with Minneapolis-Honeywell HIG liquid-floating gyros. As a backstop is aWestern Electric system (evolved for the Titan ICBM) of the radio-inertial type. B.T.L.(Bell Telephone) ground radar is specified and Packard-Bell are also named as a major elec-tronics contractor. Sperry-Rand supply the essential Univac computer. The rest of the airframe consists of integraltankage for the liquid oxygen and kerosine, and although it is pressurized this is doneas much to assist propellant feed as to preserve shape and structural integrity. Each tank isbuilt up from three panels each forming a 120-deg segment of the finished section. Care-ful stretch-press operations give the panels curvature in two planes—the drawing showsthat overall diameter changes constantly—and the inside of each skin is milled to leave a typeof "waffle" pattern giving adequate stiffness. The web thickness, which is held to greataccuracy, is reported to be 0.2 5in. At the bottom is the gimbal-mounted Rocket-dyne S-3 motor, rated at 160,000 1b thrust. This is higher than the thrust of the Atlasboost motor, but the chambers are not dis- similar. All control of the flight of Thor isobtained by varying the axis of the chamber. Surrounding the motor is a flared skirt on' which are mounted four small delta fins, giving increased stability during the first few secondsof flight. Thor thus makes a neat package of destruc-tion; yet even the engineering skill of its creators could not save the flight-test pro-gramme from a bad start. The first XSM-75 was on the firing pad at Patrick in November1956, twelve months from the start of design (and six months earlier than the first XSM-65,which contributed so much to its rapid design). It took two months to assemble a completeset of ground units, conduct all the checks and bring everything to a state of full service-ability. Thor No. 1 took to the air in January. It rose a distance estimated variously as "twofeet" and "a matter of inches"; then con- tamination by foreign matter in the liquidoxygen caused a malfunction in a starting valve, resulting in an immediate loss of thrust.The XSM-75 fell just hard enough to cause structural failure, and the remaining pro-pellants exploded. It was not until April 23 that the Douglasengineers and their sub-contractors were able to fire the second round. This one achieved aclean launching, but shortly began to "wander" from its programmed course (this was chal-lenged later, by a report which claimed that the Patrick tracking system was at fault) and, inorder to prevent it from falling on the Florida mainland, was detonated by the range-safetyofficer after a flight of 38 sec. Even more galling was the fate of XSM-75 No. 3, whichwas scheduled for firing in June (before an expectant audience estimated at 1,200 sight-seers). Four minutes before the end of the count-down, an electric circuit associated withthe kerosine pressure-regulator shorted, leading to an uncontrolled fuel spillage. Two spectacu-lar explosions followed and the weapon was engulfed in a vast fireball of kerosine, most ofwhich had burnt when the liquid oxygen tank burst shortly afterwards. This seems to have been enough "crashprogramme" for both Douglas and the Air Force, who have since followed a policy ofadvancing more methodically in smaller steps. No longer has the entire weapon system beenmade to work at each firing; instead a policy of maximum reliability and intensified staticand component testing has been adopted. Douglas and the U.S.A.F. each put $3m intoa Thor test-facility on 1,700 acres near Nimbus, Sacramento (adjoining the Aerojet-General"campus"), which, begun in November 1956, is now engaged in captive firing of completeweapons. By July Douglas were training Air Force personnel with SM-75 mock-ups andthe flow of XSM-75 development rounds passed the one-a-month level. On the fourth and fifth firings success stilleluded the harassed team, but on September 20 the sixth XSM-75 went "all the way" at last, 905 with a flight of 1,350 miles with excellenttelemetering. The next, fired on October 4, exceeded its design figures by a substantialmargin and went some 2,000 miles down- range. In that month the Defense Departmentpointed out that less than ten per cent of the test vehicles allocated to the IRBM (Jupiterand Thor) programmes had been fired, and called for a major acceleration. Douglasresponded with a second firing in the same month (on October 23) this being the eighthround and the third consecutive success. There have been several firings since. Engines for XSM-75s have been built atRocketdyne's main plant at Canoga Park, Cal. Production motors are manufactured at thenew $ 13.2m facility at Neosho, Missouri, which also produces units for Jupiter and Atlas.Employment at Neosho has already climbed to 750 and should reach double this numberby next June. The first Neosho-built Thor engine carried out the test-stand "shake-down"tests early in October, and production units are now being put through regular acceptancetests. Firings at Patrick are being accelerated, and the J.C. Harper Construction Co. wererecently awarded a $700,000 contract to "change the house and loading dock forWS-315A" at this establishment. Thor trans- porters are built by the Fruehauf Trailer Co.against a contract worth $15m. Douglas Aircraft's own major SM-75 con-tract so far is for $67.5m; placed in January, it covers "airframe fabrication and testing."Largest of the individual contracts is the Wes- tern Electric/B.T.L. (Whippany, N.J.) guid-ance contract, which, including SM-68 Titan, was finally agreed three months ago at$104,192,000. Total IRBM investment by October was $430m, of which WS-315A hasabsorbed about $230m. It is reported that about $130m is allocated to the programmefrom FY58 funds. A single production SM-75 would cost about $500,000. As noted at the outset, the productionU.S.A.F. weapon will be either Thor, or the Army Jupiter, or a hybrid "Thupiter" or"Thorpiter" (according to the ratio in which the weapons are merged). On September 13,Charles Wilson, about to retire from the posi- tion of Defense Secretary, said "the mergercan be achieved without undue delay. I believe that it is possible to produce such amerged weapon in quantity in about a year." But, at his final Press conference in October,Wilson announced the temporary shelving of olans for a merger, on the advice of theHoladay-Medaris-Schriever committee. Thor has no shortage of funds, and both it andJupiter will be developed further to see if either shows itself to be clearly superior. Last week the Department of Defense tookthe momentous decision of allowing the development programmes for both Thor andJupiter to go at least as far as the preliminary stages of production; and it was implied, butnot stated definitely, that the two weapons might be procured in inventory quantities andoperated alongside each other by Strategic Air Command. In the past few days additionalThor and Jupiter development vehicles have been fired; and, surprisingly, one of the lattermalfunctioned owing to "technical difficul- ties." As is briefly noted in the description ofthat weapon, the nose cone of Jupiter is coated with from seven to ten layers of refractoryplastic material, the underlying structure being a skeleton of titanium alloy; several of theouter layers are allowed to burn off during re-entry. Thor, on the other hand, has aslightly different type of nose cone, although part of the re-entry body is covered withspecial plastic laminates with a depth equal to half the probable wave-length of long-rangeradars, so that the reflected signal is greatly reduced in strength. Most of the Thors so far Sperry Sergeant (Left, above) Surface-to-surface. Solid sustainer motor. Overall height, about 32ft; body diameter, 36in; fin span, about 110in. Launch- ing weight, probably about 15,000 Ib; burn-out speed, at least Mach 3; maximum range, about 50 miles. Chrysler Redstone XM5 (Right, above) Surface- to-surface. Liquid-propellant sustainer motor with jet-deflection by vanes. Height, excluding nose probe, 63ft; body diameter, 72in; fin span, 12ft; launching weight, about 40,000 Ib; burn-out speed, Mach 5; maximum range, more than 200 miles. fired have been engaged in the development ofairframe and propulsion, the former in par- ticular being entirely new and somewhat ofan unknown quantity in comparison with the so-called "hand-built" and relatively conven-tional body of Jupiter. Most of the XSM- 75s have been equipped to follow a pre-programmed trajectory using an autopilot, whereas the Army weapon has now completednumerous trials with full guidance. As a result of the Macmillan-EisenhowerTalks early this year, the outcome of the Thor/ Jupiter programme will be supplied not onlyto the U.S.A.F. Strategic Air Command but also to the United Kingdom. Nuclear war-heads will not be supplied, but will be retained by U.S. forces—presumably the 7th Air Divi-sion—for allocation to the British IRBM user —presumably the Army—on Presidentialauthority. Titan During 1955 the U.S. Defense Northrop Snarlc SM-62 Surface-to-surface. Two 33,000 Ib-thrust solid boost motors, one Pratt and Whitney J57 turbojet for cruise propulsion. Body length, excluding probe, 69ft; wing span, 42ft; launching weight, over 48,000 Ib; cruising speed, Mach 0.94; maximum range, 5,000 miles.
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