Complex sentence: While the spaceflight aspect of the project was cancelled, two astronauts would later reach space, Joe Walker as a part of the X- 15 program and Neil Armstrong as part of the Gemini and Apollo programs.
Split into simpler sentences: While the spaceflight aspect of the project was cancelled, two astronauts would later reach space. One as a part of the X- 15 program and one as part of the Gemini and Apollo programs.