Complex sentence: Having failed to re-create the effect, Seaton realizes that the missing component is a field generated by DuQuesne's particle accelerator, and thereafter sets up a business with his millionaire friend, Martin Crane, to build a spaceship.
Split into simpler sentences: Having failed to re-create the effect, Seaton realizes that the missing component is a field generated by DuQuesne's particle accelerator. Seaton thereafter sets up a business with his millionaire friend, Martin Crane, to build a spaceship.