NASA has cleared the launch in July of the Russian Zvezda service module for the International Space Station (ISS), despite US concerns about the failure of the Zvezda and Zarya modules to meet NASA safety standards, such as noise levels and pressurisation integrity.
NASA says it will "resolve the problems in orbit", which, in the short term, will involve early crews installing noise mufflers and wearing earplugs.
The US General Accounting Office (GAO) says the Russian-built components for the $60 billion ISS fail to meet NASA safety standards in four key areas. Firstly, the modules lack adequate protection from space debris. Pressurised modules on the ISS are required by NASA to have a maximum of a 2.4% risk of penetration, but the chances of the Russian modules being damaged, resulting in loss of pressure, are rated at 25%.
Also, neither the Zvezda nor Zarya meet a NASA requirement that they could still function if pressure were lost. The GAO also says the Zvezda's windows may not comply with NASA standards and that excess noise in the modules poses a health and safety hazard.
NASA has relaxed its 55dB standard to 60dB, but levels in both modules are expected to reach up to 75dB. The two Space Shuttle crews that flew to the ISS in December 1998 and last May expressed concern over the noise levels in the Zarya.
The much-delayed Zvezda service module, which was to have been launched in 1998, is scheduled to fly between 8 and 14 July. The Zarya, the first ISS component, was launched in October 1998, also after long delays.
The GAO says that NASA should ensure that all safety standards are met before the launch. The GAO's concerns follow three critical reports about Space Shuttle safety, the Mars Global Surveyor loss and NASA's "faster, better, cheaper" policy (Flight International, 21-27 March).
NASA administrator Daniel Goldin says that 2000 will be a "landmark year" for the ISS. He is confident the Zvezda is ready and that the first expedition crew will be aboard the ISS later in the year. Goldin says, however, that contingency plans are proceeding to launch a US-built Interim Control Module in December, to replace the Zvezda if a failure occurs.
Source: Flight International