I was channel-flipping the other day; and I saw a brief segment about some big whoppin' huge engine they were hanging off a 747. I only caught the last minute or so before it went to commercial; but it was showing the testing etc. of this monster.
Man; the SOB was huge! Easily twice the size of the 747's normal engines. Judging by the tests; pretty damn rugged as well.
Anyone know anything about this monster? I.e. it's name/number; specs and the like?

Thanks!