Well, first, you need to do some research on space and related concepts. Then, focus on creating a compelling plot. Think about what could go wrong on the adventure and how the characters will overcome those obstacles. Also, don't forget to add some emotional depth to the characters to make the readers care about them.
To write a great space adventure story, come up with a fresh premise. Like discovering an ancient alien civilization with advanced technology. Develop complex characters who grow and change throughout the story. And make sure the setting is vivid and immersive, making the readers feel like they're in space with the characters.