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Aviation History
1962
1962 - 0839.PDF
FLIGHT International, 24 May 1962 837 Missiles and ' Spaceflight Aurora 7 and Friendship 7 BY the time this issue appears, astronaut M. Scott Carpenter, Lt Cdr, USN, should have completed up to three Earth orbits in the Mercury spacecraft MA-7, which he has named Aurora 7. Originally scheduled for May 15, and postponed until May 24, the MA-7 mission is essentially a duplicate of that flown by Col John Glenn in MA-6 Friendship 7 (which is referred to later in this account). At the same time, it includes several unique experi ments, and the MA-7 capsule incorporates modifications. An entirely novel experiment will be the release of a tethered balloon during orbit, which will thereafter be towed by the MA-7 craft. The visual portion of this experiment will be concerned with the reflection characteristics of various coloured surfaces in space. The relative merit of these colours for optimum visibility will be evaluated, and a correlation between observed and actual separation of the object from the spacecraft after release will be established. The aerodynamic portion will measure atmospheric drag and stability while deployed and a relationship between these para meters and object separation following release will be analysed. An additional objective is provided by the simultaneous dis persion of a cluster of multi-coloured particles or "confetti"— 0.25in Mylar discs which will be placed in the folds of the balloon. The test apparatus consists of a 30in Mylar-aluminium sphere which is to be inflated by an attached 9001b/sq in nitrogen bottle. The balloon is divided equally into five segments. The correspond ing colours of these reflective surfaces are orange, white, silver (aluminium), yellow and phosphorescent, which has a glow charac teristic at night. The balloon is tethered with a 100ft nylon line and a coiled 8ft strip of 0.005in aluminium, which acts as a shock ab sorber as it uncoils. A small metal beam, instrumented with a straingauge, will provide the means of measuring drag. The operational plan calls for deployment of the balloon by the astronaut at the beginning of the second orbit over Cape Canaveral. Output from the straingauge and pilot description of visual observa tions will be recorded on tape. It is desired that the tethered phase last for nearly one orbital period; however, manoeuvrability of the spacecraft is necessarily restricted with the balloon attached and earlier release may be required. "The astronaut will observe the operation from the deployment sequence, through tethering, to release and separation, and any oscillations or gyrations will be noted. Photography of angular displacement, the various colours, and the confetti dispersion will be provided for correlation with visual responses. The astronaut will orient the spacecraft in order to track the balloon's trajectory after it is released, and photographs during this phase are requested when distances are recorded." Possibly of even greater importance is a zero-gravity experiment developed at NASA's Lewis Research Center. Very little is known about die behaviour of liquids in a weightless environment. Various tests have been conducted using drop towers and aircraft in para bolic flight, but the test durations are too short. Project Mercury offers the first opportunity to observe and photograph such be haviour throughout an extended period. The major objective of this exercise is to analyse liquid behaviour in a zero-gravity state for an extended duration and to supply the results to other space programmes. The Gemini and Apollo projects require a detailed analysis of weightless liquid phenomena in order to design fluid storage tanks. This experiment will primarily establish the effect of surface tension in liquid behaviour, but other effects such as viscosity, mass, and liquid/gas volume ratio will be studied. The apparatus consists of a spherical glass flask of about 3in Mercury spacecraft No 18, designated MA-7 and named "Aurora 7" by its pilot Malcolm Scott Carpenter, may have completed its work by the time these words are read. In this picture it is being mated with its Atlas booster on pad 14 at the Cape diameter with an internal lin standpipe, which extends from the internal surface to slightly past centre. The standpipe has three holes equally spaced arounds its base to allow passage of the fluid. The flask is guarded on one hemisphere by a Lucite shield and on the other by an aluminium reflector. An O-ring is sandwiched between these two shields, so that in the event of breakage of the flask, the liquid will not leak into the cabin. The glass flask has an internal volume of 300mm (about a cup) of which the liquid occupies 20 per cent. The constituents of this liquid are distilled water, green dye, an aerosol solution to reduce surface tension, and a silicone additive to inhibit foaming. The unit will be installed within the cabin and will be observed by the astronaut-observer camera, and—periodically—by the astronaut, using a hand-held mirror. A phase of the flight which is of particular interest is the period during and immediately following retrofire. It is theorized that, in a zero-gravity condition, the liquid within the sphere will rise in the standpipe or capillary tube because of surface tension, rather than float around in globules. It may be remembered that Col Glenn experienced minor tech nical difficulties with MA-6, and MA-7 incorporates modifications. A significant change from MA-6 warning signal circuitry was made in MA-7 with regard to the heat-shield deploy indicator circuit. The limit switches which indicate that the heat shield is released have been wired in series, and rigged farther away from the actuation points to prevent accidental operation. As a result of difficulties with the low-thrust attitude control chambers in John Glenn's flight, design changes were incorporated into the MA-7 thrusters. MA-7 changes were designed to preclude nozzle clogging and improve the thermal characteristics of the chambers. Changes include the use of platinum wire instead of stainless-steel screens; reposition of the fuel metering orifice; smaller internal chamber volume; and a new fuel distribution plate. Friendship 7 in London Between May 14 and May 16 the MA-6 capsule Friendship 7 was publicly exhibited in the Science Museum in London. Tens of thousands of visitors inspected Col Glenn's craft—among them two Flight International artists. Unfortunately, the entire craft was encased in an envelope of transparent plastics—doubtless a necessary precaution—but close inspection was rewarding. Probably the most interesting region was the ablative heat shield, constructed of a special grade of glass-fibre bonded with a resin which boils away during re-entry to protect the heat shield with an insulating layer of vapour. As far as could be determined, the heat shield is quite smooth, and the impression recorded by our
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