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Aviation History
1963
1963 - 2013.PDF
• '• - FLIGHT International, 14 November 1963 fig 3 A possible procedure for orbital rendezvous. Target spacecraft A is placed in desired orbit for rendezvous (say 300 n.m.), chase vehicle 0 is launched into temporary parking orbit at 100 n.m., during which plane adjustment occurs and phase difference between itself and target is rapidly assessed by ground stations. Chase vehicle restarts at 180° relationship to achieve Hohmann transfer orbit. A further thrust impulse at apogee stabilizes orbit; vehicles match position and velocity to achieve terminal docking coming US spacecraft Gemini with Vostok, in fact, reveals that the latter already has more volume than the former; the respective weights are approximately 7,7001b for the rendezvous version of Gemini and 10,4191b for Vostok 1. There can be little doubt that valuable data on spacecraft materials, radiation shielding and constructional techniques are being obtained with the 65°-orbit recoverable spacecraft of the Cosmos programme which may well be experimental variants of the original Vostok. In the coming year this programme will be watched even more closely for evidence of a larger spacecraft. The appearance of Polyot-1 on November 1, demonstrating considerable manoeuvrability both in extending an original close- orbit to the high eccentric and accomplishing a plane-change of perhaps 6°, could be an important step towards perfecting the technique of spacecraft rendezvous (Fig 3). There would seem little difficulty in transforming the basic Vostok into a manoeuvrable vehicle of this kind by providing it with a restartable propulsion module, which might take the form of an enlargement of the existing jettisonable equipment section with tankage for medium- energy storable propellants. In view of the extra performance potential of the multi-stage Vostok booster, we should look to a considerable improvement in lift-off thrust for the new vehicle, particularly as its use has been coupled with the desire to assemble and refuel spacecraft in orbit. For this task we should expect something much better than a 10-ton payload. The difficulty of assessing the nature of the Soviet launch vehicle is, of course, complicated by several unknown factors. For example, can we assume with certainty that high-energy propellants will be used in the upper stages, or indeed for the projection of a spacecraft from Earth-orbit following the refuelling operation? Another vital question concerns the configuration of the initial stage. Does it employ tandem or parallel staging? In my recent book, Astronautics in the Sixties3, I suggested that the Russians may be clustering engines of 600,0001b to 800,0001b thrust to achieve lift-off thrusts of 4-5m lb. There have been reports of an engine in this class, employing a high combustion-chamber pressure with multiple pumps, being in design-development since the early 1950s. The time-scale of development leads us to assume that the propellant would be of the conventional lox/kerosene type; but, with a few changes in engine parts as experience grew, a change could later have been made to one of the medium-energy storables as a means of smoothing out pre-launch procedures and facilitating the highly-precise launch-timing necessary for rendezvous missions. In full development, employing a lox/hydrogen second stage, this would result in a close-orbit payload capability of at least 60 tons. Again we can look to the US space-boosters for perspective. As late as 1960 NASA schemes for Earth-orbit rendezvous were still being worked out on the basis of an up-rated Saturn 1 of 2m lb lift-off thrust3. The Marshall Space Flight Center at that time envisaged a Moon-landing mission developing from a rendezvous in Earth-orbit between no fewer than six rocket vehicles, the first being the empty Moonship and the rest orbiting tankers. Then, swiftly, project studies advanced to the Saturn C-2 of 3 m lb, Saturn C-4 of 6m lb, and Saturn 5 of 7.5m lb thrust as finally accepted for development. This thrust increase greatly simplified the flight programme, for now only two vehicles were necessary to perform rendezvous and docking in Earth orbit. Rendezvous was to be performed by launch-ln g a 200,0001b-thrust S-4B stage, fully fuelled, as the payload of a Saturn 5. A second Saturn 5 would then launch the Apollo Moon-S &P, which would act as the "chaser" for the orbiting S-4B. The Plan was for Apollo to be docked with a fully-fuelled S-4B, which w °uid then restart to propel the spaceship from Earth orbit on a transfer path to the Moon. However, difficulties which upset this tidy arrangement soon became apparent. First it was found impossible to divide the two payloads evenly between the launch vehicles, which led to a proposal to allow the S-4B to go into orbit with a full load of hydrogen but an empty lox tank. The second Saturn 5 would have to carry, in addition to the Apollo spacecraft of 78 tons, the full supply of lox for transfer to the S-4B. The mass requirements for the lunar mission were then as follows : Departure from 300 n.m. Earth orbit, 200 tons (approximately twice useful payload of Saturn 5); injection into Earth-Moon trajectory, 75 tons; return vehicle on Moon (Earth value), 25 tons. As already mentioned, this technique was in turn abandoned by NASA in fixing the final configuration of the Apollo project in favour of a single Saturn 5 employing lunar-orbit rendezvous and a composite spacecraft. It was argued that apart from requiring the near-simultaneous launching of two very large multi-stage rocket vehicles, there would be difficulties in the orbital docking of two large-size—21ft 8in diameter—manned and unmanned vehicles. There was also the question of the transfer of cryogenic propellant—a problem which could become severe, particularly if the hydrogen-fuelled vehicle had to be kept in space for any length of time. Not only would it be necessary specially to insulate the tanks but, during periods of solar illumination, it might be necessary to keep the entire space- vehicle orientated end-on to the Sun and to provide suitable radiation shields. Problems arising from the differential expansion of the large structures under solar heating, part being in sunlight and part in shadow, were considered to be particularly troublesome. It seems that the Russians are prepared to face these problems, but probably with smaller launch vehicles. The earlier time-scale of engine development, combined with an earlier commitment to manned lunar exploration, to be effected by Earth-orbit rendezvous, would appear to place the performance of the Soviet launch vehicle somewhere between that of Saturn 1 and Saturn 5. In this context it is tempting to recall a remark ascribed to Mr Khrushchev during a visit to Finland in September 1960; he told a worker that the Soviet Union would soon launch a satellite of 60 tons—"a whole train." Is it entirely a coincidence that a curve can be drawn depicting the payload growth of orbital vehicles since Sputnik 1 and that upon extrapolation it brings us to the 60-ton mark in 1964 ? A multi-stage vehicle with a lift-off thrust of around 4m lb, assuming some use of medium to high-energy propellants, would achieve this level of payload capability. Simple arithmetic shows that it would require a minimum of four launchings to achieve a comparative starting mass to two Saturn 5s. This could perhaps be reduced to three if lunar-orbit rendezvous were employed for the landing and return. The question that we must ask is whether it is reasonable to expect a launch vehicle of this size to have been produced in embryo by the autumn of 1962, or perhaps even a year earlier, if the 1961 Pacific tests are related? Following Soviet practice it would be logical to expect initial orbital launchings of a new booster to start with more modest payloads, perhaps omitting the final stage or employing a modification of existing hardware. Space Stations Everything points to a determination to achieve orbital rendezvous and docking as a foundation goal of Soviet cosmonautics. In bis Paris speech Gagarin stressed that future flights of longer duration would involve the use of multiple crews. This, he said, would enable outstanding problems to be studied
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