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Aviation History
1961
1961 - 1129.PDF
FLIGHT, 17 August 1961 231 Centaur is to achieve its performance from the 36O,OOOlb-thrustAtlas by using liquid hydrogen and liquid oxygen for specific impulse of some 420sec in the second stage. Can it give us a useful indicationof the size of the Lunik launcher—which we are assuming did not use propellants comparable with liquid hydrogen and liquid oxygen? Arocket relying on conventional propellants would have to be sub- stantially heavier. Let us tentatively suggest first-stage thrust of 600.000to 700,0001b, and a liftoff weight of 350,000 to 450,0001b. By comparison with Centaur, much greater first-stage thrust is easierto accept than considerably increased weight. Centaur is reported to have a liftoff weight of about 290,0001b, giving a thrust/weight ratio ofabout 1.24. The initial acceleration which this implies of 0.24g. com- pared with the usual optimum of about 0.3. would not in general argueefficient use of the first-stage propellants; but Centaur is yet another American compromise, in which the greatly superior specific impulseof the upper-stage propellants means that some first-stage efficiency can be advantageously sacrificed for a larger upper stage. A figure of 700,0001b for Lunik thrust has been widely quoted, withthe authority of Dr Keith Glennan, former Administrator of NASA, who said: "Soviet scientists have had at their command a rocket whichour scientists and engineers estimate is in the 600,000 to 800,0001b- thrust range. They have spoken of multi-stage launch vehicles, andsome of their mission accomplishments would indicate that they have used upper stages with these ver> powerful tirst-stage rockets." DrGlennan's remarks relate to Phase 1 of the Russian programme. How could this increase of first-stage thrust have been obtained,assuming basic first-stage design did not vary throughout Phase 1? It might have been within the development potential of the engines, orit might have been obtained by the attachment of booster units. Judging from alleged photographs of Russian rockets the latter is a frequenttechnique; many of their rockets must be expressly designed to accommodate these boosters. This picture coincides broadly with a description in a Czech journal,which suggested that the first-stage thrust of Lunik 1 was 600.0001b— 440,0001b main engine plus two auxiliary motors each producing80,0001b. The two auxiliaries were ignited at about 2,000m (6,560ft). It is of interest that these figures for the Phase I launching vehicle—about 500,0001b first-stage thrust in the initial two-stage form. 700,0001b in the final three-stage form—agree with unofficial reports of theso-called T-3 and T-3A Russian ICBMs. The inference is apparently that these two related missiles have been accepted by Western intelli-gence sources as the launchers of the first three Sputniks and the three Luniks respectively, and that their main characteristics have beendecided on the basis of their performances in these space experiments. Much more information about the precise achievements of contem-porary rocket technology would be available to Western intelligence bureaux than to the public. Here we have been making estimates on arough order of magnitude basis, but we may not be very much less accurate, for Russian rocket technology is in an almost unknown stateof development. We can only see its results. The Phase II vehicle We turn now to the Phase II launching vehicle. Many generalconsiderations have a bearing on our ideas of the size of this rocket. We have already seen that there is a strong case for believing that it wasdesigned to send the 10,5001b spaceship-satellite on a variety of missions. Almost certainly, therefore, it would need to be able to accelerate it tonear-escape velocity. Much comment in the Soviet Press lends support to this thesis. For example. Maj Gagarin is reported to have said thatthe rocket could orbit payloads several times greater than the spaceship- satellite. We are also told officially that the quantity of propellants forthe manned orbital launch was more than 100 times the payload weight. So we have here a rocket of comfortably over 1,000.0001btake-off weight, even for a mission which is not assumed to represent its ultimate capability. The apparently large ratio of fuel to payloadmay be a further indication that the rocket was designed for bigger jobs, and not at its most efficient with this relatively small payload. So far the picture is of a rocket fully comparable in size and capabili-ties with the US Saturn. In its initial C-l form Saturn is estimated to have a close-orbit payload capability of 20,0001b, and in the later C-2form 45,0001b. To pursue the comparison, the minimum liftoff thrust of the Russian rocket must be about 1.300.0001b, in view of the weightof at least 1,000.0001b of the version which put Gagarin into orbit; and in later applications the rocket will probably weigh substantiallymore. But Saturn's performance depends on the use of high-energy propellants in the upper stages. If the Russians are relying on con-ventional propellants their rocket will need to be appreciably heavier to produce equivalent performance. In this case 2m to 2.5m poundsis a conservative estimate for the first-stage thrust. What information can we extract from the figures the Russiansgave the Federation Aeronautique Internationale in support of their record claim? A precise translation of part of their submission states;"at launching, the rocket had six engines with total power of 20.000,000 h.p." It is difficult to make much of the horsepower figure. It is am-biguous. In determining the significance of the six engines, the con- figuration is the first problem—how many stages were there, inseries or parallel? It is not necessarily implied that all six engines were clustered for first-stage propulsion. In fact it clearly seems that therewere six engines all-told, and for all six to be operating at liftoff a completely parallel stage-configuration would be required. Gagarin sown accounts have told of the stages falling away "one after the other," suggesting a three- or four-stage rocket. One would not easilyaccept the possible maximum of six or even five stages. A two-stage vehicle would probably be adequate for the given close-orbit mission;but what the Russians have created is a space rocket for other and more ambitious projects, for which it is logical to suppose three or fourstages in optimum relationship. . Photographs from the film of Gagarin's flight show the Vostok withwhat is apparently the final stage of the carrier-rocket, closely resem- bling the final stage of Lunik 2. If we accept that this resemblanceimplies a single engine, as on Lunik 2, then for the two or three lower stages of the vehicle we have five engines. Many configurations arepossible. Particularly interesting is a parallel combination of the five engines for first-stage propulsion, with transition to subsequent stagesby discarding engines with or without corresponding sections of tankage. Advantages of this configuration are the theoretically higherefficiency of parallel staging, and the elimination of the need for in-flight ignition of multi-engined upper stages. It may also accountfor the appendages looking like boosters or accessory tanks which, as previously noted, frequently appear in photographs of Russian rockets. One further conjecture. A reference has been reported in a Czecho-slovak journal to a Soviet rocket engine developing 1,000 metric tonnes thrust, i.e., 2,204,9001b. Such an engine might be at the centreof the cluster of five, being discarded to leave four engines sustaining the second stage of operation. A reasonable estimate for the totalthrust of these four engines is somewhere in the region of 500 0001b which gives a total first-stage thrust of roughly 2,700.0001b. Mr VaiCleaver of Rolls-Royce has pointed out that the most technically meaningful interpretation of the quoted 20,000.000 h.p. is on thebasis of dissipation of kinetic energy in the exhaust, in which interpreta- tion it corresponds to a thrust of some 2,730.0001b. (Strictly thisapplies to all six engines, but the final-stage engine makes a relatively negligible contribution to the sum of the thrusts.) These figures areall approximate, the horsepower quoted by the Russians ^probably being much rounded-off. To sum up. in the Phase II launching vehicle we have a rocket ofthree, and possibly four, stages. These provide it with considerably greater potential than necessary for the close-orbit Vostok mission. Ifbased on conventional propellants, its liftoff thrust is likely to be at least 2,000,0001b. How does this rocket match up to the future needs of the Russianspace programme? It certainly looks as though the Russians intend to put a man on the Moon by 1967, and possibly before. They intendto have men on Venus and Mars in the early 1970s. MAIN EVENTS OF RUSSIAN SPACE PROGRAMME Sputnik ! Sputnik 2 Sputnik 3 Lunik 1Lunik 2 Lunik 3 Space-rocket tests Sputnik 4 Space-rocket tests Sputnik 5 Sputnik 6 Sputnik 7 Sputnik 8 Sputnik 9 Sputnik 10 Vostok 1 Vostok 2 Phase Oct. 1957 Nov. 1957 May 1958 Jan. 1959Sept. 1959 Oct. 1959 Phase Jan. I960 May I960 July I960 Aug. I960 Dec. I960 Feb. 1961 Feb. 196! Mar. 1961 Mar. 1961 Apr. 1961 Aug. 1961 | First Earth satellite Dog-carrying satellite Physical experiments satellite Lunar near-missLunar impact Photographed back of moon II Two ballistic firings into Pacific First spaceship-satellite Two further firings into Pacific Spaceship carrying dogs. RecoveredSpaceship carrying dogs. Not recovered 14,2951b satellite, function undis- Parking-orbit satellite for Venus probe Spaceship with dog. Recovered Spaceship with dog. Recovered First manned orbital flight Seventeen manned orbits If the lunar mission is to be fulfilled by a chemical rocket with con-ventional propellants and direct transfer, a vehicle weighing tens of thousands of tons—of the order of 50,000—at launching seems inevi-table. Propellants of higher energy would bring this figure down very considerably, but not below about 4.000 tons. This is not an impossible perspective, but it is most improbable.What we are looking for is a reasonable "next step" which would carry us from the present state to the realization of manned lunar landing.The time-scale we have in mind does not permit more than one major "next step" in rocket technology. In this sense the all-chemical, direct-transfer method does not seem to be a logical "next step." The alternatives are orbital rendezvous—flight refuelling on aparking orbit—rendezvous on the lunar surface, or the use of a direct- transfer vehicle based on the present Phase II vehicle with one or morenuclear intermediate stages. Each of these is a conceivable next step. The existing Phase IIvehicle should be big enough to make orbital rendezvous a relatively simple technique, in that not more than five vehicles would have torendezvous. Rendezvous on the lunar surface looks less likely. Jt will not be long before the course of events reveals whether orbitalrendezvous is the method selected. If it is, experiments must begin soon. That we have reached the present date without any orbital-rendezvousexperiments by the Russians may be taken as favouring the nuclear hypothesis, for a nuclear stage could be thoroughly tested and developedwithout recourse to orbital experiments. On previous form the Russians prefer this type of progress, and their rockets have been very reliableby the time of operational employment. The first orbital-rendezvous experiments might reveal unanticipated difficulties. Current development of either orbital-rendezvous techniques or anuclear rocket would go far to justify confidence in the achievement of manned lunar exploration before the 1960s are out. Unless experimentsin orbital rendezvous are made before long, it would seem that nuclear stages combined with the existing giant chemical rockets constitute theselected option—if we are not tantalizing ourselves with unreal hopes.
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