September-December 1980:space activities report

ARIANE HITS A SNAG

On 23 May the second Ariane launch vehicle (02) developed engine problems after a successful take off from Kourou,French Guiana, and crashed into the Atlantic Ocean.

After evaluating the telemetry data ESA confirmed that one of the four engines of the L.HO first stage, engine “D", showed anomalies on two occasions: the first time at Ho (ignition)+ 5.7 sec and the second time at Ho+28 sec. The sequence of events was as follows:

Ho+3.3 sec: Launcher lift-off.

+4.4 sec: All four engines function nominally up to this instant.

+4.4 to +6.0 sec: Chamber pressure of engine "D” begins to fluctuate by 4 bar, finally oscillating at an amplitude of + 11 bar at a frequency about 1000 Hz: on the films, this anomaly shows up as a yellow colouring in the exhaust. The mean chamber pressure remains nominal.

+6.0 to +28.3 sec: Engine "D" is once again nominal.

+28.3 to +28.45 sec: Recurrence of chamber-pressure oscillation of 7 bar on engine "D”, showing up the same way on the films.

+28.45 to +63.8 sec: Pressure of engine “D” once more nominal. A temperature sensor on the propulsion bay records a linear rise from 24° to 56°.

+63.8 sec: The temperature in question rises sharply to 100° C, and the chamber pressure of engine “D" falls simultaneously to 10 bar. Vehicle experiences a powerful roll torque.

+63.8 to +104 sec: Flight control system succeeds in maintaining launcher in the nominal trajectory. Roll rate reaches 60° per sec.

+104 sec: Fall in chamber pressure of engines "A" and “B",hitherto completely nominal. Engine "C” continues to function nominally.

+108 sec: Fall in chamber pressure of engine "C" and destruction of launcher, probably initiated by the breaking of a structural connection as a result of considerable general stresses. Consequently, the self-destruct system fitted to each tank operates.

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COLUMBIA'S THERMAL TILES

As readers will know, thermal rotection has become the pacing item in NASA’s reusable shuttle programme. Earlier this year Sidney C. Jones, engineering manager of the Orbiter project for Johnson Space Center, said “recent thermal/loads analyses indicated the need to assess each of the nearly 31,000 tiles on ‘Columbia’ (first production model) as individual structural systems. These loads, resulting from aero, flight control and structural considerations, identified thermal and vehicle structural deflections that affected the tile system.”

As a result, the projected date for initial launch has become rather vague - NASA says no earlier than 30 November 1980 and more likely February 1981. The uncertainty prompted the agency to buy more Delta expendable vehicles while the US Air Force ordered more Titan IIIC launchers.

“Columbia” still occupies the Orbiter Processing Facility at Kennedy Space Center to which it was piggy-backed from California in March, 1979, short of approximately 10,500 thermal tiles. Rockwell International, prime Orbiter contractor, employs 1,200 in two 10-hour daily shifts at KSC to complete tile installation. That has turned out to be an arduous task as “Columbia” lacked 5,400 tiles in late May, 1980.

The explanation lies in those comments by Jones. Agency and contractor began to worry about the system’s ability to withstand launch-related loads in October 1979. A decision to “pull test” tiles beyond the estimated load limits revealed some deficiencies. Tiles had to be removed for rework while new tiles were affixed. The net gain in some weeks fell to 100-125 but moved up to the 500-600 level in April 1980. Since 1 December 1979, all new titles have undergone densification. The surfaces glued to a Nomex felt insulation attached to “Columbia” were treated with a silica-ammonia slurry, then baked twice for 24 hours. This process increased tile strength. KSC reported that at least 10,000 tiles have been densified. Meanwhile some tiles have been damaged inadvertently by employees. Kenneth Kleinknecht, JSC manager at the launch base, believes as many as 1,000 will have to be replaced.

Three main hydrogen-oxygen engines installed in "Columbia" after static testing were removed in early May and returned to Mississippi for more “hot” firings. Each was to be operated for 520 seconds, the duration of burn for normal launch.

NASA decided upon the second firings because new turbopumps were installed after the initial tests and some welds had to be reworked. John Yardley, Shuttle programme director, said a supplier mistakenly included the wrong kind of welding wire in boxes shipped to Rocketdyne, the engine manufacturer.

Published reports in mid-May suggested that NASA might remove all tiles that have not been densified which would further delay "Columbia”. An agency spokesman said, however, the ship will not require this further assurance for one flight.

It was planned, he added, to densify tiles between subsequent launches as Orbiter cargo loads increase. “Columbia” is expected to fly four test missions, launched in Florida and landed in California, then to undergo extensive modifications.

"Challenger”, the second Shuttle off the production line, will take over in 1982.

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CHINA MOVES AHEAD

A three-stage version of China’s CSS-X-4 intercontinental ballistic missile is being developed for various space applications. Bigger than either the USAF Titan II and the Soviet SS-9 Scarp, it stands about 141 ft (43 m) tall and has a maximum diameter of 11 ft (3.35 m).

The rocket—to be known as “Long March 3”—has four gimbal-mounted engines in the first stage developing a combined thrust of some 280 tonnes. Stage two, supported by an open truss framework, has a single engine of the same type with a vacuum thrust exceeding 70 tonnes. Four small gimbal-mounted motors provide thrust-vector control. Both stages employ the storable propellants nitrogen tetroxide and UDMH. The third stage, which employs LOX/LH2 propellants, has four gimbal-mounted thrust chambers.

The launcher will be able to send 800 to 900 kg payloads into geostationary orbit. China’s first communications satellite is expected in 1981-82.

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SATELLITE INTERCEPTION TEST

The test of the Soviet Union’s satellite interception system during April 1980 was a more complex operation than might seem at first glance, writes Robert D. Christy. Indications are that four satellites may have been involved.

The first indication of the test being about to take place came with the launch of Cosmos 1169 by C-1 vehicle from Plesetsk on 27 March. It achieved an orbit of 476x515 km at an inclination of 65.8° and probably served as a calibration target for ground radars.

Next, on 3 April, again by C-1 vehicle from Plesetsk, came the launch of Cosmos 1171 into a 966x1010 km, 65.9° orbit. This orbit compares with that of the target in the previous test of the system (Cosmos 967). A wait of fifteen days then ensued until 18 April when at approximately 0040 UT, the interceptor—Cosmos 1174—left Tyuratam on an F-1 launcher. It achieved am orbit of 362x1025 km, 65.8°, leaving behind an intermediate rocket stage in a 140x432 km orbit.

At about 0411 UT on the same day, while on its second revolution of the Earth, it passed about 60 km from Cosmos 1171 about 1000 km above Leningrad. It was after this event that the fourth satellite came into the picture.

One and a half orbits later, when Cosmos 1174 was near perigee, it passed around 550 km from Cosmos 1167, a micro-thruster controlled (reconnaissance?) satellite which had been in orbit since 14 March. Cosmos 1167 was an F-1 launch from Tyuratam which had achieved an orbit of 428x444 km at 65.0° inclination. Use of the microthrust engine had ensured that it remained within a kilometre or so of its initial orbit up to that time. The orbits of Cosmos 1167, 1171 and 1174 were all in the same plane, and furthermore the nodal periods of 1167 and 1171 at 93.30 and 104.87 minutes respectively were in an exact ratio. For every nine orbits completed by 1167, 1171 completed exactly eight.

The closest approach of 1167 to 1174 occurred at 0639 UT arid at the same time, a large manoeuvre by Cosmos 1174 altered its orbit to 380X1660 km at 66.1° inclination. The manoeuvre was reminiscent of those in previous interception tests which normally signal the actual interception. The result of the modified orbit was a second close pass by Cosmos 1174 of 1171, at a distance of about 70 km, this time off the west coast of the US.

Finally, a very small manoeuvre by Cosmos 1174 on 19 April enabled it to intercept Cosmos 1171 yet again; this time the pass distance was within 20 km. It occurred over the eastern Pacific Ocean, near Easter Island.

Presumably Cosmos 1171 was the primary target in the experiment, although the obvious inference is that Cosmos 1167 was also involved; its role was probably more in the nature of an observer. The relatively distant pass of 550 km by Cosmos 1174 should probably not be classed as a true interception, but its occurrence and the relationships between its orbit and those of Cosmos 1171 and 1174 are unlikely to have been coincidental. Also, in the cases of all three interceptions of Cosmos 1171 by 1174, Cosmos 1167 was between 4500 and 5000 km away at the times of the events and could easily have monitored them.