Submarine Aircraft Detection
 

I wonder if any former/present MRA boys on here might care to comment on the following.

Helping the next door neighbour's boy with his maths homework, the following question was posed:-

A submarine at a depth of 150 feet detected an aircraft flying at a height of 30,000 feet. What is the difference in height between the two?

So simple was the answer of 30,150 feet, we suspected a trick question.

But moreover, I was left wondering at the premise of the question. I am aware that subs have acoustic capability, but can subs actually detect aircraft at such altitude from such depth?

Bearing in mind that this is a public forum :cool:, anyone care to enlighten me on rough parameters?

I do recall once receiving nothing but a funny look upon querying a P-3 flyer on the range of his MAD boom :uhoh:

Cheers

Cooch

Coochy,

To answer both your questions in simple terms;

1 - Yes
2 - No, but a quick Google search will give you the physics/maths for this

As for the Q posed to the P3 guy - you probably confused him hence the odd look ;)

The only Submarine Aircraft I know of is Skydiver. (Or Sky 1)

Surely the answer is that the question doesn't contain enough info to provide an accurate answer.

Height is not really the correct altimetric term but the answer would be 30,150 feet.
Re detection, a towed phased array radar is used which uses the surface of the sea as an aerial. The devil is in designing the algorythm to use the correct basic frequency for the temperature and sea state. The PRF must not be a harmonic of the basic or lesser wave patterns or the surface returns swamp the air return.

Basil, how did you arrive at that answer?

How tall was the submarine in your equation ;)

I'm sure that the answer is the simple one of 30,150 feet.

But I would say that height does not have a negative component, when we dig a mine we don't say that it has a height of -600 feet, we switch to depth as with submarines. Therefore the true difference in height is 30,000 feet.

This has all the attributes of the old junior school maths question involving fence panels and posts................

Wander.
Here's one for you, it's roughly the same as one my kids had when at school.

How many 1.25 metre long lengths of wood would be required to make a pentagon shaped frame with five equal 1 metre sides.
Trying to explain to the teacher that the answer was six and not five was interesting :)

I can believe it - but marked "wrong" if not the answer on the crib

Brainstormer, ok, I'll bite. You might get away with 4 even. Then again was the one metre side internal or external.

My difficulty, aged 9, was explaining to the teacher that the sum of the internal angles of a triangle were not necessarily 180 degrees. While I won the argument she then changed the rules.

Pontious, thanks for the bite but I've had to put myself in detention for EXTREME thickness :)
I should have said that the answer was 5 and not 4 as the teacher had wanted.
I have no excuse for getting those numbers wrong, sorry, I must have had a bit of a brain freeze moment.
The teacher just added the total length of sides of the pentagon frame and so thought 5 metres of wood would be enough, but of course that doesn't mean that 4 x 1.25 metre lengths would do the job.

In regards to rules being changed, that's just school life :)
Pupils are first taught that the boiling point of water is 100 degrees C, then once they get a bit older they are then shown how it can boil at a wide range of temperatures :)

BS, the last was a physics project I tried to set up. It was to boil water in a pressure cooker with various weights on the valve. Perfectly safe of course as H&S had yet to be invented. Sadly I could not mainly a seal with the thermocouple leads.

My next effort was to make some selective weed killer. At the last moment the master who had offered his lawn was advised not to. I had to make do with a school lawn. Unfortunately the recipe did mention dilution.

Finally one pupil demonstrated the effect of boiling sulphuric acid.

Happy days.

the sum of the internal angles of a triangle were not necessarily 180 degrees.

Please educate us.

Spherical trig, do I need to go on?

What is the angle between lines of longitude and latitude at the equator?

Thank you.

Cheat!

Pontious
How about a fairly safe but educational water boiling experiment.

Materials are a bottle of wine or just a wine bottle.
Thermometer
Wine saver vacuum pump.

Pour boiling water from a kettle into a wine bottle, fill about half way.
Allow to cool for a few minutes then use the wine saver to create a partial vacuum thus allowing the water to boil again at a lower temp. Repeat over and over until the water boils around 65c

At this stage you can either say 'this is how hot water boils at the summit of Mount Everest. :)

BS, the first problem is the bottle shattering as you add the boiling water :)

The second is not knowing the vacuum pressure.

The alternative was to place a bottle of carbonated drink in a freezer which was demonstrably liquid at -18, remove the cap, the pressure instantly reduces and the contents freezes.

More pleasurable was to do this with a lager in St Vincent while sheltering from a tropical downpour. Physics without fun is boring.

Mind you, attacking a submarine at 150 feet is fun - blind darts.

Well to be picky - a triangle is a 2-dimensional shape so wrapping it onto a 3-dimensional form makes it no longer a triangle. Internal angles adding up to 180deg is indeed a characteristic of all triangles!

PDR

PDR,no, using the world, take a plane from the poles along a circle of longitude. The angle between the axis from the centre of the earth to the pole and a line of longitude at the pole is 90. The angle between the axis and a radial to the equator is also 90 which gives 3 internal angles summing to 270.

The issue is not that it is 3-dimensional, it clearly isn't, but that Euclidean geometry, where the internal angles of a triangle sum to 180, is based on straight lines.