NASA set to livestream a six hour-long spacewalk from the International Space Station. Watch here.

Russian cosmonauts Fyodor Yurchikhin and Sergey Ryazanskiy will be going outside of the space station to launch several nanosatellites, perform structural maintenance and collect research samples. The event will start at 10am ET, with commander Yurchikhin and flight engineer Ryazanskiy exiting through the Pirs airlock at about 10.45am.

“Ryazanskiy will begin the schedule of extravehicular activities with the manual deployment of five nanosatellites from a ladder outside the airlock,” the space agency said in a statement. “The satellites, each of which has a mass of about 11 pounds, have a variety of purposes.

“One of the satellites, with casings made using 3D printing technology, will test the effect of the low-Earth-orbit environment on the composition of 3D printed materials. Another satellite contains recorded greetings to the people of Earth in 11 languages. A third satellite commemorates the 60th anniversary of the  Sputnik 1 launch and the 160th anniversary of the birth of Russian scientist  Konstantin Tsiolkovsky.”

Yurchikhin and Ryazanskiy will also be installing handrails outside the space station to improve future spacewalks, while they will collect samples from various locations outside the Russian part of the ISS.

This will be the seventh spacewalk of 2017 and the 202nd since construction began on the space station in 1998. The longest spacewalk ever to be undertaken was in March, 2001, when NASA astronauts Jim Voss and Susan Helms spent eight hours and 56 minutes carrying out maintenance and installation work on the station.

Astronauts are well prepared for spacewalks. Clayton C. Anderson, a NASA astronaut who performed six spacewalks during his time on the ISS, recently explained what would happen if an astronaut floated away into space in a Quora question.

He said assuming the astronaut is on an ISS spacewalk and that they have somehow become untethered from their vehicle, they will then resort to using a jet back called SAFER— Simplified Aid for EVA Rescue .

These jetpacks, which he says are “straight out of a Buck Rogers comic book,” allow astronauts to fly back to the ISS where they can reattach themselves and continue going about their business. “SAFER gives astronauts basically one-shot to ‘come home,’” he wrote. “Limited in fuel, and governed by the laws of orbital mechanics, it is not simply a leisurely task to fly back to safety.”

Anderson explains there are several steps the astronaut must take and that they are extensively trained to do this through virtual reality on Earth. These are as follows:

1. Realize one’s predicament (not hard to do, but might involve internal verbalization of cuss words!).
2. Deploy the SAFER handcontroller, power it on and stop the tumbling by initiating attitude hold (a button push). Note that you will still be moving away from the ISS.
3. Reorient yourself to ‘find’ the ISS using only directional yaw (imagine slowly rotating to your right or left). Try to stop so you are facing —as much as possible— the point from which you departed.
4. Now that you are looking back at ISS, establish attitude hold again with the ISS in your line of sight.
5. Using translational thrusts only (via your hand controller) —up/down, right/left, to ISS/from ISS (obviously to ISS is your best choice!)— and your knowledge of orbital mechanics, slowly fly back until you are close enough to grab on to something!

While untethered spacewalks have taken place in the past, so far no astronaut has ever accidentally come free and floated away.