My guess is there's not much ferrous material used in most space vehicles. Weight is so critical they're generally built from aluminum, magnesium, titanium, or even aluminium-lithium alloys, all of which are non-ferrous.

Lauch costs can be over $10,000 per pound (that's DOUBLE the price of pure gold), it pays to use exotic materials to reduce launcher and payload weight. Most of these are non-ferrous.