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Raumfahrt - Probleme mit dem Multi-Purpose Laboratory Module (MLM) für ISS von Roscosmos

24.03.2017

This Russian ISS Module Has Been Delayed For a Decade and It's Still Not Ready to Fly

Russia's next big piece of the ISS hits with another snag just a few months before launch. 

 
 

After years of delays, the Russian component of the International Space Station—which Roscosmos originally planned to deploy in 2007—finally looked like it was ready for launch. However another problem with the Multi-Purpose Laboratory Module (MLM) now threatens to derail a project that's already been plagued with them. The same severe contamination that's kept the MLM on the ground since 2013 has returned, Russian experts involved in the project told Popular Mechanics.

 

Dubbed Nauka (Russian for "science"), the MLM was designed to be a centerpiece of the Russian part of the ISS as well as the core of the post-ISS Russian station. Now that an ambitious future is once again under threat.

 
3D rendering of MLM 'Nauka.'

A TEN-YEAR-OLD DILEMMA

Launched in November 1998, the Zarya, or "Dawn," was the very first ISS module, providing power and propulsion during the international outpost's original construction. This mission was so critical that Roscosmos began building a replacement in case of a catastrophic mishap. The Zarya launch succeeded, and six years later the Russian space agency decided to transform the backup module into the MLM, saving costs on creating an entirely new, custom-built laboratory. This retrofitted module eventually became known as the Nauka.

As its originally 2007 launch date came and went, more and more delays pushed back the MLM's launch. Then, in 2013, engineers discovered a leaking fueling valve as well as contamination in the propulsion system. At the time, reports said repairs and cleanup would take nearly 10 months.

Those months stretched into years. During the last four years, engineers have been working diligently replacing a jungle of pipelines, valves, and thrusters—part of Nauka's sophisticated propulsion system—in an effort to get rid of the sawdust contamination introduced during botched upgrades. Because the spacecraft has stayed earthbound much longer than intended, parts of Nauka have also slipped out of warranty.

Fighting off political and logistical concerns surrounding the project—as well suggestions that they ground the MLM entirely until it can serve as the first module of Russia's own space station—the tedious cleanup and repair effort entered its final phase this year, and the module finally appeared on track for launch at the end of this year or, at the very latest, the first half of 2018.

 

Then things went from bad to worse.

 
ISS training modules at the Gagarin Cosmonaut Training Center. A mock-up Nauka module is in the foreground.

MORE FIXES, MORE HEADACHES

In the past few weeks, engineers found the same contamination they've been fighting for years inside the module's propellant tanks. The repair team tried to wash off these contaminants, but so far all efforts to cleanse the vessels have failed.

To make matters worse, these particular tanks, originally designed in the early 90s, are no longer in production and simply can't be replaced. Because of these tanks' unique design, fitted neatly onto the module like the chamber of a revolver, no modern tanks will work without damaging the spacecraft.

Nauka engineers did catch one lucky break. Roscosmos originally designed the vessel with a second set of shorter tanks. But to make room on the exterior of the converted module for the attachment of a European-built robotic arm and various scientific instruments, engineers removed the them. Now, these remaining (hopefully non-contaminated) tanks could be the only chance to get this long beleaguered spacecraft attached to the ISS.

 
Configuration of the MLM.
 
 
 

Engineers have calculated that a mix of four of these short tanks and two long tanks will give the Nauka module just enough propellant to maneuver itself to the space station after its separation from the Proton M rocket and even have some extra fuel for another attempt to rendezvous with the station if needed.

Although a thin ray of hope remains that Russia will finally get its long delayed spacecraft aloft, no one can tell right now how long this new obstacle will delay the Nauka from finally docking with the ISS.

 
Artist rendering of Russian modules—MLM, Prichal, and NEM—separating from the ISS to form the Russian Orbital Station.

AN ISS TRAFFIC JAM

The Nauka's continual delay has also affected other areas of Roscosmos' ISS effort. The completed Prichal Node Module was originally intended to dock with the Nauka module, but is effectively delayed instep with Nauka. Plans have considered building a special adaptor that could bypass the Nauka, but this would seriously hinder the Prichal Node Module since all but one of five extra docking ports available on Prichal will be rendered useless because of their close proximity to the station.

Still, one open docking mechanism on the far side of Prichal could be used for the attachment of the Science and Power Module, NEM, which is currently in development and designed so that these Russian modules can continue on as the Russian Orbital Station after ISS enters retirement.

Engineers continue toiling away under the added pressure that the ISS has an expected expiration date between 2024 and 2028, which is already an extension from its previous 2020 shut down date. However, all of these options remain on the table as Roscosmos officials are trying to decide what to do next. But since so much time and money have been invested into the Nauka, the Russian space agency is unlikely to give up on it any time soon.

Quelle:PM

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