I'm just asking because during WW2 most of the at-home factory work and work in general happened was done by women because all the men were gone. Was it like that for the defense industry as well (in terms of R&D and actually designing new aircraft and whatnot)?
In the UK the National Service (Armed Forces) act of 1939 was instrumental in the regulation of the provision of manpower to industry and military. Men were conscripted heavily, but there were certain 'starred' professions which could not join the armed forces- certain factory workers, mechanics, police and doctors. This was due to the lessons of the First World War where an economic downturn prior to and in the early weeks of the war led to highly experienced (but unemployed) factory workers joining the armed forces on mass, but with the expansion of industry these new jobs were filled by inexperienced workers.
Consequently manpower in the UK was strictly regulated by the government. for example, difficultly in finding manpower for the coal mines led to the creation of 'Bevin boys' in 1943 with every 1 in 8 men drafted were sent down the mine shafts.
Additionally Britain was one of the first countries in the world to conscript it female population. Women conscripted under this legislation either carried out war work (working in the factories or as a 'land girl'), or joined a suitable corps, which may or may not be segregated by sex e.g. Woman's Auxiliary Air Force was segregated, royal army medical corps wasn't
Some were. The developmental engineers (men and women) were considered essential, along with many farmers with no children, most oilfield workers, and those in heavy industry over a certain age. Those were required for the home front.