Saturday's planned launch for NASA's Endeavour shuttle—carrying seven astronauts and parts for Japan's Kibo space lab—halted when technicians discovered a gaseous hydrogen leak, CNN reports. The technical glitch is similar to the leak that grounded NASA space shuttle Discovery in March. CNN explains that the leak was "on a vent line that leads from the ground umbilical carrier plate to the launch pad and to the 'flare stack' where vented hydrogen is burned off." Endeavour's passengers have a 16-day mission planned featuring five spacewalks aimed at updating Japan's "bus-sized, 32,000-pound module" in the International Space Station. No word on the thwarted astronauts' state of mind, but the Kibo lab may offer at least one aesthetic clue: it's name means "hope" in Japanese.