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Comment: Re:Iron Man's Suit Defies Physics -- Mostly (Score 2, Interesting) 279

by John Carmack (#23266718) Attached to: The Science of Iron Man
Hydrogen peroxide powered rocket packs fly for around 30 seconds, because they have a specific impulse of around 125, meaning that one pound of propellant can make 125 pound-seconds of thrust, meaning that it takes about two pounds of propellant for every second you are in the air. Mass ratios are low for anything strapped to a human, so the exponential nature of the rocket equation can be safely ignored.

A pretty hot (both literally and figuratively) bipropellant rocket could manage about twice the specific impulse, and you could carry somewhat heavier tanks, but two minutes of flight on a rocket pack is probably about the upper limit with conventional propellants.

However, an actual jet pack that used atmospheric oxygen could have an Isp ten times higher, allowing theoretical flights of fifteen minutes or so. Here, it really is a matter of technical development, since jet engines have thrust to weight ratios too low to make it practical. There is movement on this technical front, but it will still take a while.

John Carmack
Education

A math lab in your cell phone 1

Submitted by
Roland Piquepaille
Roland Piquepaille writes "As most of us are using cell phones today, Israeli scientists have decided to put a math lab in your pocket. They developed a library of math modules which can be installed on almost cell phones available today. So you'll be able to see graphs or solve equations on your phone while on a train or a bus ride. You'll also be able to send graphs or formulas by SMS to other students — and to send the results of your exercises to your teacher. Did I mention you can download these applications for free? But read more for additional details and a look at one of the Math4Mobile applications."
Power

Neighbors Fight to Stop Backyard Windmill

Submitted by
An anonymous reader writes "It was bound to happen. Man wants to build a windmill in his backyard to obtain clean energy for his house. Main obtains correct permits and builds the windmill. Neighbors aren't happy and sue man. This is exactly what's happening to Michael Mercurio of Beach Haven Terrace, NJ. Mr Mercurio, whose windwill and 56 solar panels on his roof supply roughly 97% of his usage, is being sued by some neighbors because his 40' windwill is too tall, produces too much noise for their liking, and causes "strobe-like shadows" across their properties. Mercurio is fighting the lawsuit, not only because he wants to keep the windmill because of its positive environmental aspects, but because he is the owner of a 4 year old company which supplies and installs windmills. This may become an interesting test case for future home installations of windmills."
Space

Water vapour found on exoplanet->

Submitted by
TallDarkMan
TallDarkMan writes "We're getting quite a collection of planets (we know about) outside our solar system, and we can add another one that has water! From the article:

Astronomers have found water vapour in the atmosphere of a giant planet outside our Solar System. The detection in the extrasolar planet HD 189733b was made using Nasa's powerful Spitzer Space Telescope and is reported in the journal Nature. — It is only the second time water has been detected on an exoplanet.
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Engadget: Sony files patent for liquid airbag designed to protect electronics->

From feed by engfeed

Filed under: Misc. Gadgets

We know how much you love it when companies come up with completely contradictory names for their new technologies, so the "liquid airbag" from Sony should really make you squirm with glee -- nevermind the fact that it has nothing to do with car safety. Sony's patent filing for the technology details a liquid filled bag that could protect components from drop damage: the technology could work on laptops, smartphones, and hard drives. While others have tried using liquid bags to protect gadgets before, none have been particularly successful. Sony's patent application would result in a bag that would keep the device central, therefore protecting the entire surface of the device from damage after a drop. Now all we've got to do is wait an unknown length of time until either Sony starts creating devices with this technology, or someone else does first and Sony sues them for it.

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Office Depot Featured Gadget: Xbox 360 Platinum System Packs the power to bring games to life!


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Slashdot.org

Slashdot and the tagging fad 2

Submitted by
An anonymous reader writes "Here's a question for the slashdot crowd. Tagging is one of those fads that seems to be everywhere, and slashdot has picked it up too. After watching how people use tagging since it's introduction here, it appears that it's mostly useless though, given that nearly every article gets tagged with either contradictory tags ("yes","no","yesno", all on one post) or ones that are opinions of the tag posters ("slownewsday", "whoopeef*ck", "wewerenotmeanttobe", as a sampling from the current front page). The remaining tags of any value seem to be solely for the purpose of categorizing, and can be achieved without tagging by editors simply putting articles in the right category/subcategory. So my question: why bother with the tagging thing? Can we get that useless garbage off of the front page so we don't have to see "whoopeef*ck* and other childish noise?"

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