Thread: Occasional Puzzle Anyone?

I first saw this question on the usenet group sci.math many years ago,
but see below for what I believe is its true origin.

This is allegedly a true story.

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Early in the Cold War the Soviet Union sought to defend its bombers by fitting
rearward* firing missiles**

Every time this was tried the missile would make an immediate U-turn and hit
the aircraft that fired it. Why was this?

*At that time the best position from which to attack a bomber was from
behind, as less/no deflection or lead was needed on unguided weapons, and
early Infra-Red homing missiles needed to see the hot exhaust to lock-on.
Also this is the easiest intercept geometry when using Ground Controlled
Intercept.

**One source quotes missile in the singular, I would have thought it more
likely that they tried multiple fin or spin stabilised unguided rockets, which
were a common air-to-air weapon at the time.

(Paraphrased form "The Chicken From Minsk" by Chernyak and Rose, with
comments added by CaptainBlack).

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RonL

Because the Soviets do everything backwards?

Because the missles were manufacted by Americans?

Because Stalin was afraid the bomber pilots were getting to be too "suspicious"

my brother thinks that they were heat seeking ...that would be cool, hahaha
dan

Originally Posted by dan

my brother thinks that they were heat seeking ...that would be cool, hahaha
dan

[LECTURE=early heatseeking missiles]
The seeker has a limited field of view, and the firing aircraft would never
be in that field and so was invisible to the seeker.
[/LECTURE]

RonL

Originally Posted by Quick

Because Stalin was afraid the bomber pilots were getting to be too "suspicious"

I suspect when the phenonenem was explained that someone visited the
Soviet far east in consequence

RonL

Originally Posted by ThePerfectHacker

Because the Soviets do everything backwards?

Because the missles were manufacted by Americans?

None of these

RonL

maybe it was because one of the latches holding the missile to the plan would releace a tad bit late, forcing the rocket to turn in such a way that the propulsion in back sould send it in a circle and the rocket would then hit the bomber...

Originally Posted by CaptainBlack

Early in the Cold War the Soviet Union sought to defend its bombers by fitting
rearward* firing missiles**

Every time this was tried the missile would make an immediate U-turn and hit
the aircraft that fired it. Why was this?

Hint:

Why does an arrow point in the direction of its flight rather than tumble,
or just retain the attitude it has when released?

RonL

Originally Posted by CaptainBlack

Hint:

Why does an arrow point in the direction of its flight rather than tumble,
or just retain the attitude it has when released?

RonL

Hint2 (Hold down left rodent button and drag over space between lines

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In order to keep a arrow pointing in the direction it is going it is
fitted with fletchings (flights) which have the effect of moving
the centre of pressure when in flight backwards along its length
so it lies behind the centre of mass.

The result of this is that if there is a discrepancy between the
arrows axis and its direction of flight (in fact the direction of the
apparent wind/air flow) the aerodynamic force acts behind the
centre of mass giving a couple acting on the arrow in such
a direction that it tends to turn it to reduce the discrepancy.

We call this aerodynamic stability (at least it is one aspect thereof).


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RonL

Answer (select blank area to see the answer)

The rockets were dynamically stable as described in the hints. That means
that the rocket will flip to point into the apparent wind.

When the rocket is fired it is moving at the same velocity as the launching
aircraft, so the apparent wind is coming from behind the rocket, so it flips
around to point back at the aircraft.


RonL