About 40 million SpaceX shares are sold short, roughly 5% to 7% of the shares that are publicly available to trade, according to an estimate by S3 Partners.

SpaceX stock has fallen back toward $185 from a $225 peak, as a thin float, new short-selling tools, and a $60bn Cursor deal cool the euphoria.

A rally following the company's record breaking IPO on June 12 has cooled, with stock dropping the past two full days of trading.

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US company's shares have jumped nearly 40% from the June 12 IPO price of $135