Astronauts set for spacewalks to repair physics experiment
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The Alpha Magnetic Spectrometer in July 2011. Credit: NASA
Over the next month, astronauts aboard the International Space Station will work to fix an important particle physics experiment during a series of spacewalks said to be the most challenging since the Hubble servicing missions.
Called the Alpha Magnetic Spectrometer, this experiment is designed to collect cosmic ray particles and record their mass, velocity, charge and direction of travel. According to NASA, the instrument has collected data for over 140 billion cosmic ray events during its roughly 8.5 years in orbit.
Launched in 2011 aboard the penultimate space shuttle mission and placed on the S3 truss segment, the instrument is five years past its original three-year life expectancy. The primary part of the experiment is called the tracker. It collects data on particles as they go through the detector. However, it requires cooling.
A cutout model of the Alpha Magnetic Spectrometer. Credit: NASA
According to NASA, the cooling system involves pumps that move liquid carbon dioxide through a heat exchanger, which turns about 10 percent of the liquid into gas. The carbon dioxide then goes through an evaporator where the heat from the device is transferred, creating even more gas.
From there, the carbon dioxide flows through radiator where it is cooled back to a liquid before returning to the pump to be recirculated.
Beginning in 2014, the first of the Alpha Magnetic Spectrometer’s four redundant cooling pumps began to fail. As of March 2017, it was operating on its last functional pump.
Since then, NASA has been planning and preparing for this upcoming series of spacewalks, which is expected to be the most challenging since the Hubble Space Telescope servicing missions during the space shuttle era.
Unlike Hubble, the Alpha Magnetic Spectrometer was never designed to be repaired in space. As such, new tools and procedures had to be developed in order to accomplish this repair task.
Astronauts will need to remove a debris panel, attach new handrails, cut into cooling system tubes and install a new pump package, which was brought to the ISS aboard the NG-12 Cygnus cargo ship.
Drew Morgan, left, and Luca Parmitano check their spacesuits before their upcoming spacewalks to repair the Alpha Magnetic Spectrometer. Credit: NASA
According to NASA, astronauts Luca Parmitano and Drew Morgan of the European Space Agency and NASA, respectively, are set to exit the Quest airlock just after noon UTC Nov. 15, 2019, in their spacesuits for the first of at least four spacewalks. Dubbed U.S. EVA-59, it should last about 6.5 hours.
The outing will involve removing a debris panel and jettisoning it from the outpost. NASA said the panel is too big to bring back inside the airlock. Over the next year or two, the panel should slowly fall back to Earth and burn up in the atmosphere.
Credit: NASA
To get to the panel, Parmitano will need to ride the 17.6-meter-long Canadarm2 remote manipulator system. Once the it is removed, Parmitano will hand it to Morgan, who will push it away from the ISS.
Once that task is completed, the duo will work to install handrails around the instrument in order to gain better access and mobility for the next several spacewalks.
After those tasks are completed, the two astronauts are expected to make their way back to the airlock to conclude the spacewalk.
A week later, on Nov. 22, the second spacewalk is expected to be performed is slated to begin. A third and fourth are tentatively scheduled for Dec. 2 and Dec. 7, with a fifth on standby sometime after, if deemed necessary.
The latter spacewalks will have to be scheduled around visiting vehicle activity, including the departure and arrival of Progress cargo ships and the berthing of a SpaceX Dragon capsule.
If all goes according to plan, the Alpha Magnetic Spectrometer should be ready to continue gathering data on particles that pass through its detectors and last through at least 2030, should the ISS continue to operate that long.
