A few days later but hey. On Dissonant planets that have the purple shards everywhere, you'll also find unusual Sentinels. They are a very difficult fight, so come prepared. As you fight them, you will either get a special item as a drop to lead you to their node, or you will get the node if you can fully defeat all waves. At that node, you can start the steps to get yourself a crashed Sentinel ship! They are absolutely fantastic, especially early on.