HOUSTON, April 9 -- After a successful trip around the Moon, everything has been going smoothly on the Orion spacecraft's journey back to Earth - except for the US$23 million (RM91.68 million) toilet, which has gotten clogged.

The system designed to flush wastewater into space is malfunctioning, and Nasa believes that a chemical reaction in the urine treatment system is the culprit.

The fecal disposal system, in a separate conduit, is working properly.

Astronaut Christina Koch said the so-called Universal Waste Management System was giving off "a burning heater smell."

Rick Henfling, flight director for the Artemis II mission, stressed Tuesday that "the toilet remains operational. The challenge that we're working through is evacuating...