Forgot your password?

typodupeerror

Comment: Re:37,000 feet deep? (Score 1) 122

by ATMD (#35768208) Attached to: Richard Branson Announces Virgin Oceanic Submarine

It may be able to withstand static pressures at the ocean's deepest points, but as soon as you start moving you get dynamic pressure from the bow wave at the front. If it was going fast enough, it could easily experience a pressure head of more than 37000 feet at the nose. Plus, craft like this will be built with a decent safety factor, hopefully at least 2.0, so the people inside it don't die if the engineers get their maths wrong.

Comment: Re:What!? (Score 1) 658

by ATMD (#29961692) Attached to: Feds Bust Cable Modem Hacker

Noone should be coerced into pleading guilty. Imagine he was innocent, but unfortunate enough to have the evidence against him. Now he either confesses to a crime he didn't commit, or gets convicted of "felony commercial burglary", a crime much bigger than the one he didn't commit.

Comment: Re:3.5km/h (Score 2, Informative) 146

by ATMD (#29805381) Attached to: 32 Exoplanets Discovered By Chilean Telescope

I was reading the summary thinking "surely a telescope's sensitivity should be measured in arcseconds, and the minimum detectable speed should be in arcseconds-per-second rather than miles per hour." Of course they were talking about bodies moving toward and away from us, rather than across our field of vision, so it's a Doppler effect measurement rather than looking at a picture and saying, "hey! That bit moved!"

I've just had my big mug of coffee, but obviously it hasn't reached my brain yet :)

Comment: Re:I don't get it.. (Score 5, Interesting) 285

by ATMD (#29258557) Attached to: The Orange Goo That Could Save Your Laptop

Heh, glad I put that disclaimer there. Stopping force is proportional to velocity, (technically shear rate), in a Newtonian fluid such as water or oil: in a shear-thickening fluid viscosity is proportional to velocity. Viscosity is the proportionality constant linking speed and stopping force, so I guess that makes stopping force proportional to the square of the speed.

For more info, try these.

Comment: Re:I don't get it.. (Score 5, Interesting) 285

by ATMD (#29258533) Attached to: The Orange Goo That Could Save Your Laptop

I guess there's a limit to the amount of shock it can absorb. I would imagine its properties have been tweaked so that it stops any impact within its own thickness. Obviously if the impacting object is travelling faster, that results in more rapid deceleration and thus more forces transferred to the delicate internally-bits of your laptop. For dropping off a table though, it probably provides the smallest possible deceleration force against the floor, compared to protection materials currently on the market.

My suspicion would be that rather than rather than causing the linear deceleration of a simple spring constant, (like most other foams, rubbers, etc.), it provides an exponential deceleration: the stopping force in a shear-thickening fluid is proportional to the speed rather than the displacement. This means that the material starts acting from the very moment of impact, as that is the point with the highest speed. A spring, (or foam, or rubber, or anything else that acts like a spring), would do essentially nothing until the impact has squeezed it enough to get a decent counter-force out of it. But by that time it might be too late, and the spring might have already bottomed out. I'd be interested to see some numbers for this gel, to back up the stuff I've just written!
 
/Disclaimer: Mechanical engineering undergraduate. Don't have my qualification yet; take above post with a pinch of salt.

Be free and open and breezy! Enjoy! Things won't get any better so get used to it.

Working...