Russian cosmonauts are hoping to hit a golf ball into Earth's orbit from the International Space Station, setting a record for the longest drive ever made.
If Nasa gives the go-ahead, the attempt will take place during one of three spacewalks planned for 2006.
The ball will be hit with a gold-plated golf club, made of the same scandium alloy used to build the station, and is expected to orbit Earth for four years.
Some experts warn a mishap could cause "catastrophic" damage to the station.
The ball is expected to travel millions of miles - its progress tracked using global positioning transmitters as it gradually loses altitude through atmospheric drag.
"It will come back through the atmosphere, heat up, melt away and never be seen again," said Bill Alior, director of the Center for Orbital and Re-entry Debris Studies in the US.
Safety fears
Nasa is currently studying the risks of the commercial deal, brokered by Russia with the Canadian golf company, Element 21.
The stunt depends on the ball being hit out of the space station's orbital plane. Mr Alior said there was a "small risk" the ball could fall back onto the station or collide with it during a subsequent orbit.
The extent of the damage would depend on factors such as the impact angle and the speed of collision.
"The drive will have to be made in a certain direction to minimise that possibility.
"But the trick will be hitting the ball wearing a spacesuit. It's probably not going to be too easy," he said.
In a worst-case scenario, the ball would remain at the same altitude long enough for its orbital plane to shift so it could hit the station side-on.
An orbital debris expert at Nasa's Johnson Space Center in Houston, Texas, told New Scientist magazine that it would be like a head-on collision with an impact speed of about 9.4km (5.8 miles) per second - equivalent to a 6.5-tonne truck moving at nearly 100km (62 miles) per hour.
If the astro-golf attempt is approved, Element 21 plans to donate the gold-plated golf club to a charity back on Earth.
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