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

Business insider ^ | 3/16/2012 | Eloise Lee

[U-238]

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.

[unkus]

That’s amazing.

[loungitude]

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

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Pure hilarity! Or is it nauseatingly pitiful? Whatever.

[SunkenCiv]

Thanks U-238. The writer erred:

The moon causes the ground to shift by one to two millimeters every time it pulls the oceans' tides in and out.

No, the moon causes the ground to shift for the exact same reason it causes the oceans to shift.

[irishtenor]

Utter nonsense. The temperature in the room makes more of a difference than the moon does. The heat transfer from your hands make a bigger difference.

[Noob1999]

huh

Huh?????

Ok, so the ground shifts say 2mm at the nose of the plane, and 2mm at each wingtip, and 2mm at the tail of the plane.

So isn’t the plane in the same alignment as all of it is 2mm different???

[irishtenor]

And another thing...”Tolerances in mechanical engineering means the space between two materials, such as between a bolt and a nut. “ If the nut and bolt are put together properly, there is no space in between at all. They should be completely touching.

[Gunslingr3]

I find it kind of worrying.
The Germans had designs in WW2 that were technical marvels, and besieged by teething and reliability problems as consequence.
To what degree are we making the same mistake.
Fighters so expensive you can only afford a handful means they have to be spread thinner, and losses become even more dear.

[Psycho_Bunny]

Frankly, I’d be more worried about this kind of thing:
http://defensetech.org/2007/02/27/that-deaf-dumb-and-blind-jet/

[James C. Bennett]

Actually, there has to be a tiny, tiny space between the two. If not for that space, it would not be possible to put the bolt into the nut.

Also, about the tides, one of the reasons for the movement of the ground is the direct pull of the Moon’s gravity. The other is due to the shifting of the weight of the water mass on the land bearing it, due to the tides.

[Vendome]

Amazing! I would have never thought about that.

[irishtenor]

My bad... Whatever the nut and bolt are holding together should have no gap. If they are installed properly.

[terycarl]

They should be completely touching.

not true at all...if the fit was with no space at all, you wouldn't be able to put them together. In a common nut and bolt combination, with acceptable normal tolerances, you can actually move the nut up and down on the bolt just a tiny bit.....you can also put them together manually...no tools required!!!!

[U-238]

Ping

[raccoonnookkeeper]

It sounds rather silly that a combat aircraft will be more sensitive to tidal gravity than, say, a fragile edifice like the Crystal Cathedral.

[Lonesome in Massachussets]

Utter nonsense I'm inclined to agree with you. I would reckon the tidal effects over the length of the airframe to be about on part in 10^15.

[irishtenor]

Read my post 12.

[Nowhere Man]

I find it kind of worrying.
The Germans had designs in WW2 that were technical marvels, and besieged by teething and reliability problems as consequence.
To what degree are we making the same mistake. Fighters so expensive you can only afford a handful means they have to be spread thinner, and losses become even more dear.

True, the Germans made remarkable stuff ahead of its time but there was no time to work out the teething problems to say the least plus the complexity and cost was so bad, they could only make so many. We and the Soviets on the other hand decided to "Zerg Rush" the Germans where you had 4 or 5 Shermans/T-34's to each King Tiger. As Stalin said, there is a certain quality in quantity."

[Myrddin]

The same lesson we should take away from the AK-47 reliability in the field. It was a 5 MOA rifle. Not exceptionally accurate, but very rugged. Operating reliably in spite of loose tolerances.Our M16/M4 actions have pretty close tolerances. They require frequenct cleaning and the correct lubrication for the environment. The CLP that was OK at home was a disaster in the powder fine sand of Kuwait/Iraq. A dry lubricant was required to avoid a gummy mix of the oily CLP and powdery sand.

[Poincare]

The writer must be scientifically illiterate. The vertical amplitude of earth tides can be as much as 15 inches. And yes, ocean tides do load the edges of the land masses to a very small but measurable degree.