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NASA's Juno, Armored Tank Heading For Jupiter
coondoggie writes "When it comes to ensuring that its upcoming Juno spacecraft can survive its mission, NASA is surrounding the spacecraft's electronic innards with titanium to ward off mission-threatening radiation. Juno's so-called radiation vault weighs about 200 kilograms (500 pounds), has walls that measure about a square meter (nearly 9 square feet) in area, about 1 centimeter (a third of an inch) in thickness, and 18 kilograms (40 pounds) in mass. About the size of an SUV's trunk — encloses Juno's command and data handling box, power and data distribution unit and about 20 other electronic assemblies, according to NASA."
4 Square meters is not a square with 4m sides but with 2m sides so the parent is correct and you buddy are wrong
One square meter is about 10.8 square feet. They got everything right except for the "nearly" part (it should be "over"). Squaring the unit does square the number.
In English, the unit m^2 is written (and said) "square meter(s)" and the unit ft^2 is written "square foot [feet]".
So, one square meter is 1 m^2, which is an area 1 m x 1 m = 3.28 ft x 3.28 ft = 10.8 ft^2, which is 10.8 square feet.
There's an acceptable, albeit annoying, construction in English (or at least American English) that's completely different: "3 feet square" refers to an area 3 ft. x 3 ft., which is 9 ft^2.
Maybe they are estimating badly. Encasing a command module in square plates of titanium, however, would require 6 of those plates (envision a six-sided die). 6*18kg = 108kg. Using your math, 6*45kg = 270kg. The summary estimates 200kg which falls somewhere in between the two back of the envelope calculations.
So my guess is that 200kg refers to the total enclosure that's being created from 6 different components that are estimated in the summary to each weigh 18kg.
It'd be nice if people who submit articles "measured twice and cut once" for the maths they include in their submissions, since this is that place where discussion of the incorrect math will dominate an otherwise interesting conversation about Jupiter exploration.