Tim Furniss/LONDON
CONCERNS OVER the Russian Soyuz booster and the US Space Shuttle have marred plans for missions to the Russian Mir 1 space station.
Two successive failures of Russian Soyuz launchers are causing anxiety about the planned 14 August launch of the manned Soyuz TM24 spacecraft, already delayed because of budget cuts. The Space Shuttle fleet has been grounded for over six weeks because of worries about its solid-rocket boosters (SRBs).
The TM24 launcher, like the TM23 earlier this year, is a Soyuz U model usually assigned to unmanned missions. Production of the man-rated Soyuz U2 version of the launcher has been delayed by a lack of money.
The Soyuz U failed twice, on 14 May and 20 June (Flight International, 3-9 July). The planned TM24 flight by the slightly less powerful Soyuz U model means that the Mir's orbit has had to be lowered by 11km so that the space station can be reached.
The TM24 is to carry Russian cosmonauts Gennadi Manakaov and Pavel Vinogradev to the Mir, with French researcher Claudie Andre-Deshays. The Frenchman will conduct the Cassiopea science mission and return to Earth on 30 August with the TM23 residents, Yuri Onufrienko and Yuri Usachev, who were forced to spend an additional 40 days in space because of delays in Soyuz booster production.
The other occupant of the Mir, NASA's Shannon Lucid - who broke the US space flight record of 115 days on 15 July - was due to return aboard the STS79/Atlantis, on 9 August at the end of its nine-day Shuttle Mir Mission 4, but will have her stay extended to late September, because of the Shuttle grounding, the most serious since 1990. Lucid will pass the record for the longest female-space flight on 7 September.
NASA has grounded the STS79, the next planned Space Shuttle mission - to deliver Lucid's replacement, John Blaha, to the Mir - from 31 July, to at least 15 September, to replace the vehicle's SRBs. The delay will have a knock-on effect on Shuttle missions through 1997 and possibly delay NASA's first Space Station mission.
The safety-first decision was made after inspection of the boosters used for the previous mission, the STS78, revealed that hot gas had seeped into J-joints in the field joints of both SRBs, in some cases penetrating the J-joints, and impinging, but not penetrating, the capture-feature O-ring designed after the Challenger accident in 1986.
The seepage was probably caused by the use of a new adhesive and cleaning fluid in the J-joints. The new adhesive was used to comply to latest US ozone-depletion regulations.
Although the STS79, equipped with a similar set of boosters, was declared safe to fly, NASA decided to change the boosters on the stack, which had already been rolled back from the launch pad to the vehicle-assembly building at the Kennedy Space Center in Florida to avoid the approaching Hurricane Bertha.
The Atlantis will be fitted with a pair of boosters which use an older adhesive, and which were to have been fitted to the following STS80/Columbia mission planned for October. Enough stocks of the older adhesive is available to fly several missions, and a new type of adhesive may then have to be manufactured.
The STS80 will be delayed until November, and the STS81/SMM5 flight will be put back from 5 December, to 25 January, 1997. Seven missions had been planned for 1997 and the final flight for that year, the STS88/Endeavour, which is to be the first NASA International Space Station mission, may be deferred until 1998.
Source: Flight International
