MBT-70

[Marek_Tucan]

Why is there the restriction? How does the water below flight path affect the guidance system?

[PlasmaKrab]

Marek_Tucan said:
Why is there the restriction? How does the water below flight path affect the guidance system?

I may be speaking total BS here, but isn't that related to the fact that the wires aren't coated with some insulant due to weight constraints?
The signal-bearing wire is coiled inside the missile body (or around it in some earlier examples) and doubled or quadrupled for redundancy and equilibrium issues, so the specific weight of the wire is a critical issue to the missile performance. So electric insulation may have been disregarded and therefore lead to critical signal shunts over water.

Another possible case, which would be more consistant with the Striker anectode cited above, is that the wire just sinks into the water (sounds probable for even thin copper wire) fast enough to drag the missile back and down. That would be linked to the fact the the wire uncoils freely while the missile moves, but would also run against this fact, except at top ranges, because of the amount of reserve coiled wire available for unattended sinking before it affects the missile's flightpath.

Just my two cents, extracted from whichever data I could digest on the subject! So if anyone has better facts on this or wants to speculate further...

[Basileus]

PlasmaKrab said:

I may be speaking total BS here, but isn't that related to the fact that the wires aren't coated with some insulant due to weight constraints?
The signal-bearing wire is coiled inside the missile body (or around it in some earlier examples) and doubled or quadrupled for redundancy and equilibrium issues, so the specific weight of the wire is a critical issue to the missile performance. So electric insulation may have been disregarded and therefore lead to critical signal shunts over water.

Another possible case, which would be more consistant with the Striker anectode cited above, is that the wire just sinks into the water (sounds probable for even thin copper wire) fast enough to drag the missile back and down. That would be linked to the fact the the wire uncoils freely while the missile moves, but would also run against this fact, except at top ranges, because of the amount of reserve coiled wire available for unattended sinking before it affects the missile's flightpath.

Just my two cents, extracted from whichever data I could digest on the subject! So if anyone has better facts on this or wants to speculate further...

I concur with your former conclusion in that Striker footage, PlasmaKrab. The wires are too thin to have much insulation, hence standing water, chain link fences, power/phone lines etc. may short out the wires. The rather sudden dive the missile took toward the pond's surface didn't look like a voluntary course correction. As far as depth of the pond, I don't think the weight of the wire would impact missile guidance, as wire guided missiles are routinely fired from helicopters without adverse effects, even with rotor downwash.

Basileus