Exiting from box eight at just $1.30 with most outlets, the Robert Britton-trained chaser stepped well and sat in third position in the early stages.
Last week's other heat winner, Starc, was best away from box one and took the lead turning for home the first time, with Space Star unfortunately taken off the track by another runner.
Pushed back to fourth position and 10 lengths from the leader, the 35kg heavyweight shifted to the outside of the track and charged forward, approaching the home turn a mere length behind Starc. In a thrilling finish, Space Star made one last-ditch effort on the line to score by a length in a flying time of 42.18 over the 720m distance.
The son of Bekim Bale and Tonto Tears kept his perfect box eight record of three wins from three starts intact with Saturday night's win and recorded his first career group win for owner Camilla Limon.
Starc was gallant in defeat finishing runner-up for fellow Victorian mentor Andrea Dailly and rank outsider Smooth Number would have trainer Allen Hansen smiling from ear to ear after hanging on for third place.
Space Star's victory was the 16th of his career at start No.27, with the $40,000 winner's purse taking his prizemoney total to $146,700.
Group Two Summer Plate Final full results
1st: Space Star (Robert Britton) – $40,000
2nd: Starc (Andrea Dailly) – $10,000
3rd: Smooth Number (Allen Hansen) $5000
4th: Pumped Up Zarr (Neil Staines)
5th: Double Rinse (Andrea Dailly)
6th: Big Kat (Carl Schlensog)
7th: Serena Nimbus (Neville Brown)
8th: Zipping Rory (Peter Dapiran)
First section: 16.16
Second section: 29.58
Run home: 12.60
Margins: 1L x 11L
Scratchings: Raramuri, Joane