BAeSEMA was a naval technology joint venture between British Aerospace and the French Sema Group. The company was formed in 1991 and dissolved in November 1998 when BAe purchased SEMA's 50% share.
BAeSEMA acquired Dowty-Sema in 1992, another naval systems joint venture between Dowty Group and Sema.
From BAe's perspective BAeSEMA was an attempt to increase its capabilities as a naval prime contractor. This was not entirely successful for two reasons:
BAeSEMA's major competitor in the UK naval systems market was GEC-Marconi through its Ferranti Naval Systems and Plessey Naval Systems businesses.
On November 11, 1998 BAe acquired Sema's interest in the company for £77 million and merged it into British Aerospace Defence Ltd. BAe's naval capabilities increased dramatically in the next year, its acquisition of Marconi Electronic Systems to form BAE Systems saw it take control of Marconi Marine's shipyards; VSEL (Barrow-in-Furness), Govan (Glasgow) and YSL (Scotstoun).