The National Museum of Science and Industry (NMSI) and the Design Museum are both preparing to welcome new directors.

Martin Earwicker, whose background is in the management of government science and defence institutions, will join the NMSI in May. Deyan Sudjic, the art critic and dean of the faculty of art, architecture and design at Kingston University, will take up his post at the Design Museum in September.

Earwicker, who is currently the chief executive of public sector research body the Defence Science and Technology Laboratory, replaces Lindsay Sharp, who stepped down in June 2005.

An NMSI spokeswomen said Earwicker 'has an outstanding combination of skills gained in a career that brings a wide-ranging understanding of science and engineering, universities, business, management and government'.

But Earwicker has no experience of museum management and will have to oversee 960 staff and the five NMSI institutions: the Science Museum; the National Railway Museum; Locomotion; the National Museum of Photography, Film and Television; and the collections centre at Wroughton. Issues that Earwicker will have to face include the future of Wroughton, staffing and a tight budget.

One science source, who did not want to be named, said: 'The NMSI has never been at the centre of the debate about science, technology and society and it faces real challenges to get there. This is because it's still an object-focused institution and there's very little money to develop the institutions. Earwicker has a certain credibility because he's a scientist, but he faces a real uphill struggle.'

The appointment of Sudjic at the Design Museum comes just over six weeks after the announcement that Alice Rawsthorn, its director for the past five years, had left. The museum, which has still not given a reason for Rawsthorn's departure, is also working on a £50m relocation from its Shad Thames home.

Sudjic is the Observer newspaper's design and architecture writer and has previously been the director of Glasgow 1999 UK City of Architecture and the 2002 Venice Architecture Biennale.

A spokeswoman for the Design Museum said no other candidates were interviewed: 'We found out Deyan had been offered a big international job, which he was about to accept. We had to move fast to persuade him to stay in the UK and, fortunately, we succeeded.'

Simon Stephens