More than 1100 young people and their families enjoyed free events full of games, sports, art and competitions.
The Play Day events, organised by local councils, took place in Haywards Hetah, Burgess Hill and East Grinstead.
They featured space-themed fun and activities for children aged under 13.
Prasanna Rebbi, from Burgess Hill, went to all three Play Days with her children.
“We have been to all three events because it is very informative and kids can learn a lot,” said Prasanna. “We have never seen these activities before and my daughter liked it a lot; she wanted to learn more and have fun. Now she is interested in space and is researching at home, it is a really good start.”
Cllr Pru Moore, cabinet member for leisure and sustainability, said: “All three events were a tremendous success, I’m absolutely delighted with how well supported they were by the local community and our town council partners.”
The events took place in Victoria Park, Haywards Heath, on August 5, St John’s Park, Burgess Hill, on August 6 and King Georges Field, East Grinstead, on August 12.
Children learnt about chemical reactions by mixing ingredients to create sherbet and ‘space sludge’. They also made alien masks, solar powered vehicles and jet packs.
Those with energy to burn played on flying spaceships, space hoppers and bouncy castle.