plane type

If I remember my History Channel correctly, he was killed in a B-24 that was modified to serve as a "smart bomb"  I can't remember the name of the project but the idea was for a war-weary B-24 to be loaded with explosives taken off with a pilot and co-pilot then at a certain point a chase plane would take over and remotely pilot the aircraft to the target via TV.  The pilot and the co-pilot were to bail out at some point after this transition.  Apparently the plane Kennedy was in exploded before he and the co-pilot could parachute out.

Project Aphrodite, based at Fersfield in Norfolk, did trial the use of old B-17's and B-24 as remote controlled bombs. Kennedy was indeed in a B-24 while on a mission to attack a German V-1 launch site

I thought it was a 17. I checked a book I have on the Military airfields of Norfolk, and according to that it was a B-24. There was a B-17 navigation plane flying with the B-24.

Close, the bomber was the USN's version of the B-24: Consolidated PB4Y-2 Privateer.  The cause of the premature detonation is unknown. It is suspected that it was a faulty fuze on the explosives. The bomber was to be remote to dive on a V-1 launch site.

Seasick is correct. The TV show Dogfights featured this plane and Project Aphrodite on one episode. When Joe Kennedy's plane exploded, the explosion was so large that the largest piece of debris left measured, if I remember correctly, less than 2 foot long.