Nasa chief Charles Bolden has inspected a prototype spacecraft engine that could power an audacious mission to lasso an asteroid and tow it closer to Earth for astronauts to explore.
Mr Bolden checked on the progress a month after the Obama administration unveiled its 2014 budget that proposes $105 million (€81m) to jump start the mission, which may eventually cost more than $2.6 billion (€2bn).
Engineers at the Jet Propulsion Laboratory in southern California and Glenn Research Centre in Ohio are developing a thruster that relies on ion propulsion instead of conventional chemical fuel.
Nasa is under White House orders to fly humans to an asteroid as a stepping stone to Mars. Instead of sending astronauts all the way to an asteroid, as originally planned, the space agency came up with a quicker, cheaper idea: haul the asteroid close to the Moon and visit it there.
The space agency would launch an ion-powered unmanned spacecraft to snare a yet-to-be-selected small asteroid in 2019 and park it in the Moon’s neighbourhood.
Then a spacewalking team would hop on an Orion space capsule that is currently under development and explore the rock in 2021.
Scientists have said the redirected asteroid would pose no threat to Earth. If it inadvertently plunged through the atmosphere, it would burn up, they said.