Here's One Reason The Moon's Gravity Is So Important To The Military


Photo: flikr/Defence Images

When you’re building one of the world’s most advanced jet fighters, there’s no room for error.Engineering technology used by BAE Systems, a partner in the F-35 joint strike fighter program and the manufacturer of Typhoons, even takes the moon’s gravitational pull into account. 

The moon causes the ground to shift by one to two millimeters every time it pulls the oceans’ tides in and out. And this tiny movement can throw off the precise alignment of an aircraft’s frame as pieces are put together.

“That might not sound a lot, but given the tolerances we are working to on Typhoon, two millimeters is two millimetres too much,” said Martin Topping, head of the aircraft’s maintenance at BAE.

Tolerances in mechanical engineering means the space between two materials, such as between a bolt and a nut.

BAE explained that the tolerances used to build the Typhoon, most notably used by the British RAF, are so fine now that even the movements of the tide can throw the jet fighter’s tolerances out.

Its frame is 15 metres long, so there’s plenty of room for tiny misalignments here and there. Taking the moon’s pull into account as the frame is pieced together helps the finished aircraft’s computer control system function more accurately in flight. And it saves 16 gallons of fuel per average flight.

So how do you fend off the moon’s pull?


Photo: MOD

The defence and aerospace company builds each Typhoon on a floating concrete raft. Having the aircraft and the engineering equipment on a raft ensures that everything moves together — not one piece is left a millimetre behind. “All movement is relative, achieving a near perfect alignment whatever the moon may be doing,” said Topping.

The automated alignment system on each raft uses two laser trackers and nine computer-automated levers. BAE said it has spent over $4 million dollars installing this facility, helping to create one of the most perfectly aligned fast jet airframes in the world. 

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