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Aviation History
1988
1988 - 1099.PDF
SPACEFLIGHT Shuttle booster test fi BRIGHAM CITY QM6, the third full-duration test firing of the redesigned Space Shuttle solid rocket booster, took place at test stand T-24 at Morton Thio- kol's facility in Utah on April 20, reports Tim Furniss. "Initial results look good," said a Thiokol spokesman after the test. However, full results of the test will not be known for several days. Should QM6 be deemed a success, it will be followed by a QM7 firing in June and a final, Production Verification Motor (PVM-1) firing in July, clearing the way for a Shuttle launch as early as August 4. The 126ft-long, 1 • 2 million- pound QM6 motor, which fired for two minutes, incor porated flight-configuration field joints between four motor segments, and a capture feature tang and clevis design, with three Viton O rings. The mating insu lation surfaces at each joint were bonded with an adhesive, and incorporated a modified J-shaped deflection relief slot to reduce stresses and increase the sealing action of the bonded surfaces during the firing. The centre field joint was assembled with an intentional manufacturing-type flaw, consisting of a wave defect in the surface of the bonded insulation J seal. This defect may have allowed hot gases to penetrate the bonded insu lation as far as the capture feature O ring. The motor- case-to-nozzle joint was the flight configuration, incorpo rating 100 radial bolts, adhe sively bonded insulation surfaces, a shaped relief slot, and an added Viton wiper O ring, designed to keep the adhesive on the insulation surfaces during assembly. To demonstrate fault- tolerant characteristics of the redesigned case-to-nozzle joint, an intentional flaw was introduced. This was a small blowhole through the poly- sulphide adhesive, which may have allowed gases to penetrate the bonded insu- FLIGHT INTERNATIONAL, 30 April 1988 Rutherford Laboratories reveal Chixsat A proposed Anglo-Chinese X-ray satellite, Chixsat, has been designed by the Rutherford Appleton Laboratory using a Computervision CISMedusa CAD/CAM system. Chixsat's X-ray detectors are exposed when the boost motor is ejected. lation to the added wiper O ring. The nozzle was assembled with the structural backup design outer boot ring which was test-fired on DM8 last August, and not with the design tested on the DM9 firing last December, which failed. The National Research Council has recommended that the Shuttle does not fly until the nature of the DM9 failure is fully understood, and that the design of the QM6 boot ring may be inher ently flawed, even if the QM6 is declared a success. The QM7 test firing next June is scheduled to take place on Thiokol's new T-97 test stand, and will not incor porate intentional defects. The T-97 stand will apply typical ascent stresses to the motor through the external tank attachment points, and this is testimony to Nasa's internal acceptance that the Challenger disaster was primarily caused by excessive stresses on the system in flight that caused not just field joint defects, but struc tural failure in an SRB from lift-off. These assertions by aerospace engineer Ali Abu Taha continue to receive wide support, despite Nasa's official denials. The PVM test in July will incorporate several inten tional flaws that will allow hot gases to impinge on the many O rings in the system. Meanwhile, Nasa has, submitted to Congress its acquisition plan for an advanced solid rocket booster (ASRM), which could fly in 1994. RFPs are to be issued in the summer for a new booster which, surprisingly, still includes a segmented design. The new design will, however, include substantial changes to improve reliability and safety margins, says Nasa. In addi tion, the booster's ballistic design precludes the necessity for throttling the Space Shut tle main engines during the period of maximum dynamic pressure (max q), which reduces or eliminates about 175 criticality 1/1R failure modes in the Shuttle system. The ASRM design goal is to provide a 12,0001b increase in payload capacity, equating to an additional 2-4 equiva lent Shuttle missions per year (based on a rate of 14 flights per year), and will support Space Station deploy ment and other critical missions. Part of the ASRM procure ment will be acquisition of a new booster facility operated by the selected contractor on a Government site, which, in keeping with President Reagan's commercialisation goals, could be provided commercially to Nasa. In preparation for the STS 26 Discovery mission, the flightcrew recently conducted a complete mission simulation at Houston. This featured a centre engine shutdown at T+5min 52sec, requiring an abort-to-orbit. The left-hand orbital manoeuvring system pod experienced problems, one of the five on-board computers failed, and the gyros on the TDRS payload malfunctioned. The simu lation was declared a complete success. SPACESHOTS Hideo Nagata has been elec ted chairman of the Inmarsat Council for 1988-89, succeed ing Geoff Hall. Inmarsat now has 54 member countries, operating almost 7,000 ships with Inmarsat equipment for direct-dial telephone, telex, facsimile, and data commu nications. The proposed adaptable space propulsion system upper stage for Space Shuttle, to act as a backup to the Titan 4 Centaur G prime launch vehicle, has been scrapped. Australia and New Zealand are building satellite sig nals intercept facilities. The facilities are being built in South Island and at Geraldton, Western Australia. 25
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