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## NASA's Juno, Armored Tank Heading For Jupiter185

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."
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## NASA's Juno, Armored Tank Heading For Jupiter

• #### Re:Unit conversions (Score:3, Informative)

by Anonymous Coward on Wednesday July 14, 2010 @01:08PM (#32903104)

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 (Score:5, Informative)

by Anonymous Coward on Wednesday July 14, 2010 @01:09PM (#32903116)

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 (Score:5, Informative)

on Wednesday July 14, 2010 @01:16PM (#32903242)

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.

• #### Re:Unit conversions (Score:1, Informative)

by Anonymous Coward on Wednesday July 14, 2010 @01:17PM (#32903252)

1 m^2

(1 m^2)(3.28 ft/m) = 3.28 m ft

(1 m^2)(3.28 ft/m)(3.28 ft/m) = 10.75 ft^2

• #### Re:Unit conversions (Score:1, Informative)

by Anonymous Coward on Wednesday July 14, 2010 @01:19PM (#32903288)

Is that really how American's say it?

(How our what say it?)

I think the convention is that "feet square" vs "square feet" tell you whether or not the multiplication has been done yet. So it's 3.2 feet square or 10.24 square feet.

• #### Re:Is there an engineer or scientist in the house? (Score:4, Informative)

on Wednesday July 14, 2010 @01:57PM (#32903950) Homepage Journal

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.

• #### Re:Something new? (Score:3, Informative)

on Wednesday July 14, 2010 @02:09PM (#32904088) Homepage

Is this because NASA is using some COTS electronics on this mission? In the 'old days', we saw hardened electronics being used. Or is it a unique mission requirement, beyond what the old probes did?

From TFA ..

For the 15 months Juno orbits Jupiter, the spacecraft will have to withstand the equivalent of more than 100 million dental X-rays

It's going to see hella radiation, so it needs some pretty beefy shielding. They're also using hardened components developed for Mars missions.

Without its protective shield, or radiation vault, Juno's brain would get fried on the very first pass near Jupiter

So, yes, it's a unique mission requirement.

• #### Re:Something new? (Score:3, Informative)

on Wednesday July 14, 2010 @02:16PM (#32904190) Homepage

FTFA

"For the 15 months Juno orbits Jupiter, the spacecraft will have to withstand the equivalent of more than 100 million dental X-rays," said Bill McAlpine, Juno's radiation control manager, based at NASA's Jet Propulsion Laboratory in Pasadena, Calif., in a release.

According to NASA Jupiter has sizzling radiation belts surrounding its equatorial region and extend out past one of its moons, Europa, about 650,000 kilometers (400,000 miles) out from the top of Jupiter's clouds. Juniper has 63 moons.

• #### Re:Something new? (Score:2, Informative)

on Wednesday July 14, 2010 @03:53PM (#32905504)
They are still using hardened electronics, but Jupiter's radiation belts are orders of magnitude more intense than Earth's radiation belts.

The main component to shield against in the Jovian environment are high energy electrons. It turns out that shields made out of higher charge elements are better at shielding electrons per mass. Aluminum is the defacto spacecraft material. You want something higher on the periodic chart than Al (for the best shielding to mass ratio), so they chose Titanium due to considerations like material availability and ease of manufacturing while still standing up to being launched into space.

Another possibility for high energy electron shielding is to take aluminum and place a higher charge metal (Tantalum is often used) layer right next to it. The Aluminum is the structural component, but the Tantalum is the shielding component.
• #### Senate vote on NASA bill tomorrow;Bill Nye on NASA (Score:3, Informative)

on Wednesday July 14, 2010 @04:13PM (#32905742) Journal

On a related note, there's a bill in the Senate which will be voted on tomorrow (Thursday) morning which threatens to reduce the proposed funding for robotic missions (like the one described in the summary), commercial crew, and space technology in favor of building a government-designed heavy-lift rocket instead. The Planetary Society has an update describing the situation and is urging people who care about space exploration to call their Senators immediately:

http://www.planetary.org/blog/article/00002584/ [planetary.org]

More background info on the bill: http://www.spacepolitics.com/2010/07/14/a-quick-review-of-the-senate-nasa-authorization-bill/ [spacepolitics.com]

For the curious, Bill Nye the Science Guy (the new director of the Planetary Society) and Louis Friedman are hosting a webcast/discussion at 5pm ET today about the future direction of NASA:

• #### Ti, and it's "approximately" 1 meter on a side (Score:1, Informative)

by Anonymous Coward on Wednesday July 14, 2010 @05:02PM (#32906432)

200kg is approximate, and no, it does not include the mass of the contents. And, the actual dimensions aren't a regular cube of 1 meter size, nor are the walls a uniform thickness.

In most spacecraft design (including this one) the enclosure has ribs and cutouts to accommodate the hardware attached, as well as provide appropriate shielding AND for stiffness for vibration loads.

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