Complex sentence: Multiple attempts to put the Seastar into production, often as a joint venture with other aerospace companies, were made throughout the 1990s and early 2000s, however securing the necessary financing to proceed to the manufacturing phase proved challenging.
Split into simpler sentences: Multiple attempts to put the Seastar into production, often as a joint venture with other aerospace companies, were made throughout the 1990s and early 2000s. However securing the necessary financing to proceed to the manufacturing phase proved challenging.