NASA, in preparation for a spacewalk on Saturday, has devised makeshift snorkels that would allow an astronaut in a spacesuit to continue breathing even if a sudden water leak should fill the helmet, as happened to an Italian astronaut who almost drowned in July.

Two astronauts, Col. Michael S. Hopkins of the Air Force and Richard A. Mastracchio, are to step out of an air lock on the International Space Station at 7:10 a.m. Eastern time in the first of at least two spacewalks aimed at replacing a malfunctioning pump module that is part of the space station’s cooling system.

Koichi Wakata, a Japanese astronaut, will be operating a robotic arm from inside the station to assist with the repairs.

Colonel Hopkins will be wearing the same spacesuit — No. 3011 — that leaked in July. During that spacewalk, water partly filled the helmet. The astronaut in the suit then, Luca Parmitano, was able to hurry back to safety, but not before water covered his eyes and blocked his nostrils.