Hello aspirant, admission in IISc Bangalore is based on JEE advanced rank and does not depend on JEE mains percentile. For admission  in IISc Bangalore you need a very good rank in JEE advanced. The cut off in 2020 for aerospace engineering was under 250 All India Rank in JEE Advance. If you study very hard for JEE advance exam and get a very good rank then only it is possible. But after getting 82 percentile in JEE mains it is difficult to get under 250 rank in JEE advance but not impossible .

However there are other private and state engineering colleges in which you can you can get a seat. To find the colleges based on your JEE percentile visit -

JEE Main College Predictor 2021 : Predict Colleges based on your JEE Main Rank (careers360.com)

BEST OF LUCK!!