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Aviation History
1963
1963 - 1431.PDF
FLIGHT International, 15 August 1963 249 ELDO THIRD STAGE . . . upper and lower portions of a spherical tank. Around the equator of this tank is the main reference level of the stage, and also the main thrust ring. Above this ring is attached the payload, and below are attached the main thrust chamber on the axis of symmetry and the two verniers arranged one on each side. Material of the propellant tank is a titanium alloy, Al-Mg 5, approximately corresponding to the US alloy 2219. The shells are formed to their finished 1.72m (67.72in) diameter by a con trolled explosive process of the type now widely practised through out the USA. The inter-tank bulkhead is a dished disc with an additional central depression, and it is secured around its periphery by electron-beam welding. Working pressure inside both tanks is 2201b/sq in, generated by gaseous helium contained in a pair of ellipsoidal bottles. At present the latter are of resin-bonded glass- fibre, but titanium is also being considered for these tanks. Sea-level thrust of the main chamber is 2.25t (4,9601b), and a complete thrust chamber is shown in half section in an accom panying photograph. Chamber pressure is relatively low at 1501b/ sq in, but much of the design is of an advanced and bold nature. The injector head, combustion chamber and throat section are all of the Al-Mg 5 titanium alloy, and are regeneratively cooled. Around the base of this section is an integral flange to which is bolted the main divergent nozzle skirt. Completely uncooled, this is explosively formed from a single piece of 1mm (0.04in) plate of 13V 11C 3A1 titanium alloy. Three stiffening rings are welded around the nozzle periphery. To provide vehicle control in pitch and yaw the main chamber is arranged to gimbal in any direction. The chamber is pivoted near the throat section to a ring which in turn is pivoted about a perpendicular axis (like the mounting of a free gyro) to the main chamber support structure. Propellant feed is effected through flexible piping. Maximum rate of change of the thrust vector is held to a low value in order to avoid any excessive swivel angle of the verniers and thus reduce overall propellant consumption. The verniers, which burn continuously until final orbit injection, are likewise mounted in universal joints and fed through flexible piping. In the final design the verniers will probably be arranged to pivot fore and aft only, in order to provide roll control. Thrust of the present vernier is 50kg (1101b), and thrust-chamber pressure 751b/sq in. In order to obtain more precise injection into orbit Bolkow are developing a new design of vernier with a thrust of only 30kg (661b). This is considered to be the lower limit at which it is possible to utilize regenerative chamber cooling, bearing in mind the chosen propellant combination, low pressures and long burning time. Around the lower half of the stage is attached a skirt fairing weighing approximately 351b, which mates with the French second stage. Above the main thrust ring are 12 tubes welded in aluminium alloy (like those which carry the engines) into the form of four M units. Above these is welded a ring carrying the satellite payload, while between the M units are disposed the various instrumentation and control packages. Access to the latter is obtained through small doors which open around the upper part of the stage, while the satellite payload is protected by a nose fairing of resin-bonded glass- fibre. Propellant feed to the third-stage propulsion begins before s iage separation. Hypergolic ignition occurs almost instantaneously, and the fairing skirt of the third stage parts from the French second stage after some 1.2sec. The lower skirt fairing on the German third stage is arranged in left and right halves, and the command 10 jettison these follows a few seconds later. At an altitude of 35 to 50 miles the nose fairing over the payload is similarly discarded. his sequence is necessarily tentative, because much has still to be worked out between the Germans and the Italians (who are re sponsible for the payload and nose fairing), the Dutchmen (re- ponsible for third-stage telemetry) and the Belgians (to whom '-as been entrusted the ground radio guidance system). An engineering mock-up third stage has already been built, a "d a flight-weight model will be delivered to Hatfield at the end of |"is year for the mating and vibration testing of the complete three-stage ELDO vehicle in the test tower of Hawker Siddeley r^'/namics. Tnis ELDO third stage has been conceived expressly ';r *ne Purpose of placing payloads in Earth orbit; the capability ''• 'he ELDO vehicle in its initial form is a satellite payload greater Engineering half-chamber model of the Entwicklungsring Nord main engine of the ELDO third stage. The radial thrust chamber proposed for the OPHOS high-energy versions was pictured in model form in our June 6 issue than a long ton (2,2401b) in a circular polar orbit at 500km (311 miles), or a satellite of some 200kg (4401b) in synchronous 22,400- mile equatorial orbit. At the same time this assignment is giving Germany the opportunity to develop a rocket and space technology comparable in quality with that of any other nation. Britain and France all have plenty of clever ideas for future versions of all three stages of the ELDO launch vehicle—and so, no doubt, have other members of the organization. For the present, however, the critical third stage is German, and it is this stage which will inject the first ELDO-launched satellite into orbit from Woomera in 1966. Moreover, the Germans are jealously guarding their management of the third stage, and intend by the superiority of their technical proposals to ensure that this continues in improved versions of the ELDO vehicle. An accompanying drawing illustrates one of three Bolkow proposals for an improved first stage, and it is appropriate to conclude by quoting what this company has to say. "Overall performance of multi-stage satellite boosters depends to a large degree upon the efficiency of the final stage. An increase in third-stage performance will lead to considerably greater pay- loads at relatively small expenditure. Use of high-energy propellants for the third stage of the ELDO launch vehicle will increase its payload capacity to 1,3201b for escape missions as compared to the present 2201b. The planned configuration permits the launch of equatorial 24hr satellites to establish worldwide communication and TV networks, as well as space probes for lunar and planetary missions. "Since October 1961 studies have been conducted at Bolkow- Entwicklungen KG on several versions of stages with high-energy propellant combinations such as 02/H2 and F2/H2, pump and pressure-fed. The latter solution appears to be especially promising and has been investigated in more detail. The design proposal OPHOS IE is based on the same propulsion and attitude control system as that used for the medium-energy version. Gross weight is 8,6001b and net weight 1,1501b. The main engine with radial thrust chamber and E-D nozzle delivers 39,000N (8,8001b) thrust. The two vernier engines in compact modules produce 390N (881b) thrust each in vacuum. Overall design philosophy of the system is based on space conditions, and its main parameters have been optimized to obtain maximum performance. Current studies are conducted in view of the so-called 'Further Programme' of ELDO." It is evident from this account that even the original "first programme " ELDO vehicle is far from being a fully known quan tity, and the future versions are a long way down a road fraught with difficulties. But the ELDO vehicle is demonstrating the ability of seven nations to tackle a challenging technological concept together. ELDO third stage Dimensions Overall length (height), excluding satellite payload and nose fairing, 150.2in; overall diameter, 79.1 in; length with skirt jettisoned, I32.5in; distance between verniers (unvectored centrelines), 66.9in; diameter of payload mounting ring, 54.3in. Weights Total stage weight, excluding payload, 7,2501b; total weight of pro pellants. 6,2201b. Performance Total thrust of stage, 5,1801b, of which 4,9601b is main engine and 2201b is contributed by the two verniers. Later vernier engines will be of 661b instead of 1101b thrust each. This stage, in conjunction with the British Blue Streak first stage and French second stage, can place some 2,5001b in low Earth orbit or accelerate over 2001b to escape velocity.
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