B777-200
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Situational Awareness
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Aircraft Aircraft Damaged; Flight Crew Landed in Emergency Condition; General Maintenance Action
Aircraft
Upon gear retraction after takeoff; got lots of noise and vibration from front left area of the cockpit. No warnings or instrument indications of anything wrong were ever presented from the aircraft. As speed increased and we cleaned up and accelerated on an NADP1 schedule; vibrations became greater and wind noise very loud.  We got as fast as 240 knots indicated. I directed the First Officer (Pilot Flying) not to accelerate any more. At FL150; we leveled off and I directed the First Officer to slow the aircraft. I worked with ATC to allow us time to investigate. Engines; doors; windows; packs and pressurization were all normal. Discussed with the First Officer; and decided to return to ZZZZ and check the aircraft on the ground. No fuel dump required; no emergency was declared. We put the gear down at 25 miles to touchdown; and the noise and vibration reduced significantly. All gear indications were in the green. Landing by First Officer was uneventful.  The brace from the nose gear to the left nose gear door had broken; and the door was swinging freely on its two hinges. The gear door had a crack in it near the rear hinge.
B777 Captain reported after gear retract; noise and vibration were heard/felt; resulting in a return to airport.