Some cremated remains of more than 300 space buffs, including one of America’s first astronauts, are aboard the Falcon 9 rocket being prepared for launch from Cape Canaveral, Florida on Tuesday.

Houston-based Celestis Inc., arranged to fly the group memorial with rocket manufacturer Space Exploration Technologies, which is aiming to become the first private firm to reach the International Space Station.

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The container holding canisters of ash won’t fly to the orbiting outpost. It will stay with the second-stage section of the Falcon rocket, which separates from the capsule 9 minutes and 49 seconds after launch.

The companies don’t want to talk about the mission until after liftoff, now scheduled for 3:44 a.m. EDT, but there’s plenty of news about who is flying on the Celestis website.

The dearly departed include Mercury Seven astronaut Gordon Cooper, who died in 2004, and actor James Doohan, who portrayed “Scotty” on the original Star Trek television series and movies.

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The cremated remains are sealed inside lipstick tube-sized canisters and packed inside a container attached to the Falcon 9′s second stage. The spent motor-turned-memorial plot should stay in orbit for a year or so before it is pulled back into Earth’s atmosphere and incinerated.

Celestis has been flying space memorial missions for 15 years. Earth-orbit flights cost about $3,000.

SpaceX hopes to not just fly the deceased and cargo aboard its rockets. The company is competing to build a space taxi for astronauts and tourists as well.

Image: Celestis’ last launch was a suborbital mission flying from Spaceport America in New Mexico in May 2011. This time around, its aiming for higher ground. Credit: Celestis