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Aviation History
1959
1959 - 1475.PDF
714 , Missiles and Spaceflight... THORS FOR THE R.A.F. (continued) students who have passed through the Tucson school (andVandenberg) have been from the RAF. A number of general aspects of the Thor in operation w#redisclosed by Douglas officials during our visit. A Thor squadron, we were told, consists of 15 missiles and 600 officers and men.The 15 launch pads would be located in five groups of three, and each trio (rather than each individual pad) would be in effect aself-contained unit. One complex of power generators, fuel tanks and power distribution trailer would handle one group of threemissiles, and the launch-control trailer possessed three count-down stations, one per missile. With appropriate maintenance, it was stated, a Thor could bekept for ten years and still be operational. Was it likely that Thors would still be in operation ten years hence? A company engineersuggested that "it might turn out to be the DC-3 of space efforts." The missile had been designed conservatively, and it could be"stretched" and its range increased by about 1,000 n. miles (although Gen. LeMay had told us earlier that effort was atpresent directed to improving reliability, not range). Intended for single-shot operation, a Thor emplacement couldnormally be readied for a second firing in about three days (ducts and cables, but not the pad itself, were burned when a missile wasfired). The training pads at Vandenberg had special facilities for repeated launchings. The company would not state how manyThors had been built to date, but those approaching completion in the plant at Santa Monica were numbered between 220 and 230.The numbers started at 101 and appear to run consecutively. The accompanying cutaway drawing is the first to be publishedshowing the R.A.F.'s new strategic delivery system in detail. In view of the thoroughness of our account published on December 5it is appropriate here merely to highlight certain features. Propulsion is provided by a Rocketdyne MB-2 rocket engineof 150,000 1b thrust at sea level, operating on liquid oxygen and RP-1 fuel. These fluids are stored in large tanks flanking thelaunch emplacement, and are forced into the missile's integral tanks by helium or nitrogen pressure. The fuelling couplings are FLIGHT, 22 May 1959 Warhead and heat-sink naseeonaand inner liner assembly Warhead mounting accessGuidance electronics (items 3-11 are mounted in the computer pallet)Stabilization electronics Computer servo unit Inverter control Accelerometer electronics Power supply Invertor Torque exciterjunction box Stabilized platform gimbal unitEnvironmental tank Guidance ground-conditioning duct Looking not unlike parts of the many DC-series of piston engined transports which were built in the same plant, these are Thor inter-tank sections, pictured from a skirt in which the engine has yet to be installed inserted by hydraulic rams, one on either side near the base ofthe missile and the propellants pass up through pipes 21 and 22 which terminate in "mushrooms" near the top of each tank. Fromthe tanks the fluids are expelled by gas pressure from the spheres 26, and are finally delivered to the engine at high-pressureby the turbopump 28. Separate pipes feed the verniers 35. After a predetermined time—dependent upon target range, butof the order of two minutes—-the supply to the main engine is cut off. At this point the velocity is 25ft/sec less than the 15,000-odd ft/sec required to establish the missile on the correct trajectory, and the final, gentle acceleration is effected by the twin verniersoperating alone. These are likewise cut off after a few more seconds, when the velocity and trajectory are exactly correct.Then the nosecone and warhead 1 is unlatched and allowed to fly ahead by itself, while solid-propellant retro-rockets 36 retardthe remainder of the vehicle. Upon re-entry, the heavy G.E. heat-sink nosecone protects the warhead, while the missile body,a few miles behind and on a shorter trajectory, burns up like a shooting star on re-entry. This general flight-profile is common to all current types ofballistic missile (except for a series of hypothetical high-trajectory devices which are intended to spend some days en route). Thor'sreaction time is theoretically 15 minutes, i.e., this is the time which must elapse between the receipt of a signal to fire and the firstround's departure. In practice the reaction time depends upon a host of factors, the chief being missile reliability and crew com-petence. During development trials the countdown may take any- thing from 24 hr upwards, but at least one 77 Sqn. crew, and atleast one pad, are now approaching the minimum. For this reason it is ridiculous to argue about whether Bomber Command Thorsare operational or not; one or two rounds could, with reasonable luck, be fired now with something like an operational schedule,and the future programme is merely a matter of building emplace- ments and working on the crews until the latter have reached thepeak of training. Keeping crews at such a pitch will probably have to involve occasional live firings, and these will doubtless becarried out at Vandenberg, pending the extension of the range and construction of an emplacement at Woomera. All this is, of course, very valuable groundwork in preparationfor our own Blue Streak. It has been said that, without substanti- ally modifying the airframe or powerplant, the range of Thor couldbe extended by some 1,000 miles, bringing it into the same 2,500- mile class as Blue Streak. At the moment, however, it is muchmore important to achieve true operational capability with the hardware already in Bomber Command's hands.
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