Tucked into the rocket's second stage are cremated remains of more than 300 hard core space fans finally making it into the final frontier.

Space Exploration Technologies' Falcon 9 rocket is scheduled to lift off from Cape Canaveral Air Force Station in Florida at 3:44 a.m. EDT (0744 GMT) on Tuesday. The company, also known as SpaceX, replaced a faulty engine valve that triggered a last-second halt to its initial launch attempt on Saturday.

The rocket's prime cargo is a 14.5-foot-tall (4.4-meter-tall) capsule called Dragon that is filled with food, clothes and supplies for the six astronauts and cosmonauts living aboard the space station, a $100 billion project of 15 countries that flies about 240 miles above Earth.

Falcon 9 carries a secondary payload as well - a container holding lipstick-tube-sized canisters filled with cremated remains. The deceased include Mercury astronaut Gordon Cooper, who died in 2004, and actor James Doohan, who portrayed chief engineer Montgomery "Scotty" Scott on the original Star Trek television series. Doohan died in 2005.

If all goes as planned, nine minutes and 49 seconds after liftoff, Dragon's second stage will separate. It should spend the next year or so circling Earth as an orbital space memorial before it is pulled back into the atmosphere and incinerated.

Houston-based Celestis Inc has arranged for cremated remains to be flown in space 10 times previously, though not all the launches have been successful.

The Earth-orbiting space memorials cost about $3,000. Celestis also arranges for suborbital flights and launches to the moon. Relatives are invited to attend the launch and then participate in a group memorial service.

The upcoming Falcon 9 flight is the firm's biggest yet, Charles Chafer, chief executive officer of parent company Space Services, wrote on his Facebook page. Ashes from 308 people are aboard, though most are reflights from a failed 2008 launch.

"With my Celestis team," Chafer posted on his Facebook page Saturday, as the group gathered to watch the launch attempt. "Ignition, no liftoff ... wow that was close. Try again Tuesday."

Chafer declined an interview request. "We made a commitment not to comment publicly until after the mission," he wrote in an email to Reuters.

"Everyone at Celestis wishes Godspeed to SpaceX," he added.

NASA, which is sponsoring SpaceX's test run to the space station, likewise declined to comment.

"We are aware of the Celestis payload, but we're not commenting on it. It's not our payload," said NASA spokesman Josh Byerly.

SpaceX did not respond to interview requests.

(Editing by Jane Sutton and Vicki Allen)

• A Permanent Economic Emergency