This story was updated at 9:15 p.m. EDT.
Two spacewalking astronauts ventured outside the International Space Station Monday to stock the outpost with vital spare parts on a day that, 40 years ago, saw the first-ever moon landing by people from Earth.
Astronauts Dave Wolf and Tom Marshburn spent nearly seven hours working outside the station to attach three large spare parts to a stowage platform while, on Earth, NASA celebrated the 40th anniversary of the Apollo 11 moon landing.
The spacewalkers were floating outside at the exact time - 4:17 p.m. EDT (2017 GMT) - in which astronauts Neil Armstrong and Buzz Aldrin touched down on the moon with their Eagle lander on July 20, 1969.
?How cool,? said Canadian astronaut Julie Payette from inside the station as the day began.
Payette and Endeavour shuttle pilot Doug Hurley controlled the station?s robotic arm from inside the outpost during the spacewalk while crewmate Chris Cassidy choreographed the excursion from aboard the orbiter.
?A special day to do this on the 40th anniversary of Apollo,? Cassidy said.
Legacy of Apollo
Monday?s spacewalk was the second of five on tap for Endeavour?s crew, and the 202nd excursion by American astronauts since Armstrong and Aldrin walked on the moon, NASA officials said.
Earlier Monday, NASA held a press conference at its Washington, D.C., headquarters with a group of Apollo astronauts who lamented the $100 billion investment into the space station. Apollo 13 commander Jim Lovell said that after 10 years of construction, the station?s return on that investment has been about nil.
?It?s almost a white elephant,? Lovell said. ?And until we can get a return on that investment, it?s money wasted.?
Lovell, Aldrin and other astronauts chided NASA and the United States in general, for losing its nerve to take ambitious and dangerous risks for the sake of exploration. Mars - not the moon - should be the ultimate goal, the veteran Apollo astronauts said.
?We have allowed our country to turn into a risk averse society,? said Apollo 7 lunar module pilot Walt Cunningham. ?It?s reflected at NASA, it?s reflected in everything that we do today?there are things worth risking your life for.?
Stocking up on spares
Wolf and Marshburn began their orbital work at 11:27 a.m. EDT (15:27 GMT) as the linked shuttle and station flew 220 miles (354 km) above the country of Kazakhstan in Central Asia. They spent the bulk of their time moving spare parts brought up to the space station aboard NASA?s shuttle Endeavour, which arrived at the outpost last week.
With Wolf perched at the tip of the station?s robotic arm, the spacewalkers carefully stowed a 6-foot (2-meter) antenna, a cooling system pump and a motor for the station?s railcar-like mobile transporter on a storage platform attached to a truss on the outpost?s metallic backbone. At times they had only inches of clearance between their cargo and the immense bulk of the space station.
The spacewalkers hit a few snags that slowed their orbital work. Wolf had some difficulty positioning the foot restraint that served as his perch at the tip of the station?s robotic arm.
An attachment hook on Marshburn?s retractable 85-foot (26-meter) tether slipped from his spacesuit-clad hands during the excursion, delaying the spacewalk until he could retrieve it from under an equipment cart. At no time was Marshburn at risk, since his 55-foot (16.7-meter) safety tether and the longer line remained connected and securely in place, mission managers said.
Because of the glitches, Wolf and Marshburn ran out of time before they could set up a new camera on the station?s Japanese-built Kibo lab. It was the sixth career spacewalk for Wolf and the first for Marshburn.
Endeavour?s STS-127 astronaut crew is currently in the midst of a 16-day mission to deliver a new crewmember and a large external experiment porch for the space station?s Japanese-built Kibo lab.
While the spacewalkers worked outside, the station?s Expedition 20 crew successfully repaired a flooded toilet inside the orbital outpost. The $15.6 million space commode broke down on Sunday, posing a potentially uncomfortable problem for the crowded station?s crew of 13 people (seven aboard Endeavour and six station spaceflyers).
The joint shuttle-station crew is relying on two working toilets aboard the station because the shuttle Endeavour cannot empty its own bathroom?s wastewater tank while docked at the outpost. The system?s nozzle on Endeavour?s exterior would spray the wastewater over a new experiment porch, which astronauts installed Saturday outside the Kibo lab.
With the toilet now working, Endeavour?s crew does not have to worry about filling the shuttle?s wastewater tank or resorting to Apollo-era waste collection bags that were packed aboard just in case.
The U.S. space agency bought the station toilet from Russia in 2007 in a $19 million deal that included the commode and spare parts for other systems, a NASA spokesperson told SPACE.com. It was delivered to the space station last fall.
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SPACE.com is providing continuous coverage of STS-127 with reporter Clara Moskowitz and senior editor Tariq Malik in New York. Click here for mission updates and SPACE.com's live NASA TV video feed.