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."

Comments

Let the fat jokes commence

[Widowwolf]

It's not fat, It's thick plated!

Re:Unit conversions

[Anonymous Coward]

4 Square meters is not a square with 4m sides but with 2m sides so the parent is correct and you buddy are wrong

Re:Unit conversions

[chill]

Close enough for government work.

aka

"Mars Polar Lander"

Re:Unit conversions

[Anonymous Coward]

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.

Re:Unit conversions

[MyLongNickName]

So one square meter isn't a square with 1 meter sides?

Re:Unit conversions

[blueg3]

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.

Is there an engineer or scientist in the house?

[natoochtoniket]

"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 "

I notice a few issues in this description, which also appears in the article. Some fact-checking might be in order.

How can a single thing be 200 kg, and also be 18 kg? You would think that a single thing would have only one mass.

Then, of course, a square meter is slightly more than 10 square feet.

How can a single square meter of material be made into all six sides of a box the size of a SUV trunk, without slicing it into thinner sheets. A square meter might make one side of such a box, but not all six. If all six sides of a cube total 1 square meter, each side would be about 40.8 cm square. Of course, the box doesn't have to be a cube, but the sum of the areas of the six sides still cannot exceed the total of the material.

Titanium has density of 4.5 g/cm^3. So a 100x100x1 cm piece of it would be 45 kg, not 18 kg.

Re:Is there an engineer or scientist in the house?

[rwv]

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.

This is America!

[riskeetee]

SUV's don't have trunks!

What, expecting a metric system rant?

Summary bad, but not as bad as you might think

[MartinSchou]

The article links to some kind of 'ooh, look at me' article instead of NASA's own page on Juno.

Juno Armored Up to Go to Jupiter

Each titanium wall measures nearly 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.

Not exactly good maths there, so probably a PR piece from a 'journalist'.
9 foot^2 = 0.84 m^2. Could be correct, though I wouldn't use "nearly" for something that far off. And it's impossible to tell if the walls are really 9 foot^2 and they just made a very rough guestimate of the metric equivalent.

1/3 inch = 0.85 cm
Again, that could be right. It might be exactly 1/3rd inch and they guestimated that to about 1 cm. But it's still 15% off.

40 lbs = 18.14 kg
And then you hit something where the weight is actually correct. But since they've messed up that much on the other two, we now don't know if it's exactly 40 lbs or exactly 18 kg.

Hell, we don't even know if the NASA guys who wrote this are incompetent or not. Well, we know they're incompetent, we even know how much (about 15%).

However, the NASA page seemingly being written by an 8-year-old with a bad understanding of units, doesn't really justify linking to an article that is essentially a copy of NASA's page, and especially not when there is no attribution or links to the original article.

Re:Unit conversions

[PagosaSam]

Jesus boys and girls! I had to go back reread the summary to remember what the topic was! Hint: it's not metric/english conversion.