NASA’S Artemis II space mission was due to reach the moon last night, though the three US astronauts and one Canadian on board continued to suffer toilet trouble.

Until the problem with the so-called lunar loo is fixed, mission control has instructed the astronauts to use back-up urine collection bags. The toilet malfunctioned following lift-off last Wednesday and has only worked intermittently since then.

Engineers suspect that an ice blockage may be preventing urine from completely flushing overboard, though the toilet remains usable for defecation.

Orion programme deputy manager Debbie Korth said the astronauts have also reported a smell coming from the toilet, which is buried in the floor of the capsule with a door and curtain for privacy.

Mission management team chairman John Honeycutt said the astronauts were “OK,” adding: “They trained to manage through the situation.”

Artemis II is poised to set a new distance record for humans, travelling more than 252,000 miles from Earth before performing a U-turn behind the moon and heading home without entering lunar orbit. The record is currently held by the 1970 Apollo 13 mission, which had to loop around the moon after an onboard explosion damaged the spacecraft.