## 4. Build a Creepy Crabmobile

October 3, 2013Why build a crabmobile?

### Because working underwater involves huge pressures. To keep it simple the best pressure unit to use is Atmospheres.

### At sea level ( 0 m) the pressure is 1 Atmosphere (atmos).

### …………………………………………………………………………….

### Every 10 m depth adds 1 atmos pressure.

### At 10 m the pressure on your lungs is 2 atmos ie double sea level.

### At 20 m the pressure on your lungs is 3 atmos ie triple sea level.

### …………………………………………………………………………….

How strong are Your Lungs?

### …………………………………………………………………………….

You breath air at 1 atmos pressure in and out.

### According to The Institute for Structure and Nuclear Astrophysics, Indiana

## your lungs only have a capacity:

# …………………………. ± 0.03 Atmos

### …………………………………………………………………………….

### If this comes as a surprise, try it. Try breathing through a hose of, say, 50 cm.

### You will find it quite difficult.

### …………………………………………………………………………….

### SCUBA DIVING

### …………………………………………………………………………….

### The regulator on the SCUBA tanks feeds you air at a pressure experienced at that depth.

### ie. At 10 m you breathe air at 2 atmos pressure

### At 20 m you breathe air at 3 atmos

### Pressure at each depth can be calculated using this equation:

### But here is the Problem:

### …………………………………………………………………………….

### AT 30 m ( 100 ft) the disorientation of Nitrogen Narcosis begins.

### It’s caused by too much nitrogen dissolving in the blood under pressure.

### At 50 m (165 ft) Slowed response. Laughter.

### AT 66 m (217 ft) oxygen toxicity kicks in.

### At 70 m (230 ft) Flawed judgment. Hallucinations.

### At 90 m stupefaction.

### But if you surface too quickly the nitrogen bubbles out in your blood and gives you the bends so called because it is soooo painful.

### Ahhhhhh!

### ……………………………………………………………

# Introducing the Crabster CR 200

### According to Gizmodo, one problem with conventional ROVs – Remotely Controlled Vehicles – is their propellers kick up silt from the sea floor, and their engines struggle in strong currents. But this new underwater explorer sidesteps both of these problems by skittering around the sea floor like a crab.

### CRABSTER CR 200, developed by a team at the Korean Institute of Ocean Science and Technology (KIOST), can survey shipwrecks and collect data for research. It has 4 pilots. One for the walking and posture. One for the manipulators, cameras and lights. One for the sonar and other scanning equipment. One navigator. This is some creepy crab.

# How much pressure can the Crabster withstand?

### At 240 m:

### p = 0.1 d + 1 = 0.1 x 240 + 1 = 24 + 1 = 25 atmos

### Wow! That is 25 times more than sea level.

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