Astronauts on the space shuttle have tested a heat-shield tile-repair kit.
It was the fourth spacewalk during Endeavour's flight
Spacewalker Michael Foreman squeezed a toothpaste-like material into holes in sample tiles; and then patted the goo flat with a small foam brush.
The material sets hard; and the US space agency hopes the kit could be used on real tiles if orbiters sustain heat-shield damage on future missions.
Nasa declared the test a great success but its engineers will want to examine the samples in detail on the ground.
The experimental results will be returned on shuttle Endeavour when it lands on Earth next week.
Foreman and Robert Behnken were making the fourth spacewalk of the current shuttle flight to the International Space Station (ISS).
During their six-and-a-half-hours outside the platform, the pair also replaced a broken circuit breaker.
The Endeavour mission has already seen the installation of the new Japanese Logistics Module.
This is a storage facility for the Japan Aerospace Exploration Agency's (Jaxa) Kibo laboratory, the main section of which will travel to the station on the next shuttle flight.
The ISS has also taken delivery of the Dextre two-armed robot which will be used to do external maintenance on the platform.
The US space agency has 10 more flights planned after Endeavour to complete the space station and deliver supplies before the orbiters are retired in 2010.
Endeavour is due back on the ground on 26 March.