After a gravity-defying run since its blockbuster debut, SpaceX shares finally came back down to Earth on Thursday (local time), falling more than 6% as the post-IPO euphoria began to lose steam.Shares of the Elon Musk-led company were trading at $178.50, down 6.5% during the session, after having already slipped nearly 5% a day earlier. Even after the recent decline, the stock remained more than 30% above its IPO price of $135.The latest drop puts SpaceX's $2.52 trillion valuation under pressure. Should the losses hold through the session, the company would shed more than $150 billion in market value.The decline comes after a sky rocketing first week on the market, during which SpaceX's valuation surged beyond $2 trillion following its Nasdaq debut. Shares had jumped sharply in their first two trading days before investors began reassessing whether the company's valuation accurately reflects its long-term prospects, particularly as it ramps up spending on artificial intelligence initiatives."Given the magnitude of the IPO and the strong initial performance, some degree of profit-taking is not surprising," IPOX Schuster analyst Kat Liu said."This has been a particularly eventful and shortened trading week for the largest IPO in history," she added.Investor activity also pointed to a slowdown in buying momentum. Retail traders had purchased more than $300 million worth of SpaceX shares on a net basis over the previous three trading sessions. However, Vanda Research reported that net purchases had reached only $9.1 million by 2:00 pm ET on Thursday.Market participants had already warned that significant swings in the stock price could be expected in the early days of trading because of SpaceX's relatively small public float and elevated valuation.The weakness spread across the broader space sector as well. Rocket Lab and Planet Labs both declined about 3%, while AST SpaceMobile fell around 7%. Intuitive Machines was also lower, shedding roughly 3%, Reuters reported.Meanwhile, SpaceX continues to push ahead with its artificial intelligence strategy. The company announced on Tuesday that it would acquire Anysphere, the developer of the AI coding agent Cursor, in a stock-based transaction valued at $60 billion.Furthermore, according to sources, the company's bankers are expected to begin discussions with investors as early as next week regarding a bond sale of at least $20 billion, with the proceeds aimed at supporting its AI ambitions.