"Quality of work experience" is a subjective thing - whether you're dealing with a recruiter, family member, friend, coworker, or MBA adcom.
Put it this way. Your work experience in defense/aerospace certainly isn't unfamiliar to any adcom -- there's always a handful of folks each year who come from the same or similar industry as you at any of the top b-schools. In your case, it really comes down to how successful you are at conveying what you've learned on the job and how that will help you in the future post-MBA (in whatever career you're going after).
In practical terms, it's not something to really worry about. If the job is interesting to you, you're learning a lot, and you enjoy the people you work with - you'll be just fine. So long as your GMAT score is within range (by the time you apply, shoot for 700 or greater) and you have decent work experience (no matter what industry it is), it really comes down to how well you execute the applications (i.e. do you come across as a dynamic individual).
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