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Countdown to Jupiter: Juno just seven days from orbit

Coat

I just can't help it, by Jove

Q: What's the name of NASA's Jupiter probe?

A: Don't Juno?

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Pint

Re: I just can't help it, by Jove

Well done for coming up with a joke worse than Friday's referendum result.

Have a pint.

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Re: I just can't help it, by Jove

This is now the new Godwin's Law isn't it? Additional bonus points increase as the reference tends towards the complete non sequitur.

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Joke

Re: I just can't help it, by Jove

You can always go for the Abbot @ Costello "Who's on first" angle.

Q: Whats the name of that new space probe?

A: Ju-no

Q: No!, I don't know! Why would I ask you if I knew?!"

Repeat variations on this riff for 10 minutes.

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Alert

Four tons!

Egad.

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I would like to thank the team at El Reg for the opportunity to indulge in my passion for needless pedantry. 5% of something isn't "much of".

That being said: best of luck to the Juno team! Hope things work out as planned, looking forward to getting to know Jupiter better.

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5% of total weight is on shielding for one component.

A) that sounds like a lot of shielding to me

B) once you add in shielding for other components of the craft, then you will have a lot of shielding

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Anonymous Coward

RE: pedantry

If you want pedantry, the crafts total original weight was 3625kg, that includes the craft, fuel and oxidizer. The craft itself is 1593kg, so the electronics vault shielding, which is 200kg comes in at 12.5% of the crafts weight. This excludes the shielding for cabling and instruments outside the vault.

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Alien

...when it will get dropped onto the planet.

Poor thing. All that effort... at least it won't suffer like Spirit did on Mars. "Did I do a good job? Do I get to come home? Guys?"

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Re: ...when it will get dropped onto the planet.

And dropped into the planet, shurely?

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Re: ...when it will get dropped onto the planet.

If it's going to be dropped into a planet, then they could have at least made it black, with a dimensional ratio of 1:4:9

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Re: ...when it will get dropped onto the planet.

Neil, and you do know that the poor thing is going to be utterly crushed about the whole thing. Not nice at all. And yes, it reminds me of the rovers that definitely could, and did.

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Re: ...when it will get dropped onto the planet.

Didn't we try that with Jupiter about 6 years ago? IIRC, the planet kindof... exploded.

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Alien

Re: ...when it will get dropped onto the planet.

All rovers sent to Jupiter will become platforms for airborne life to rest upon.

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Anonymous Coward

Juno

2 comments

Juno was the wife of Jupiter, so anything it well named as something keeping a close eye on Jupiter.

The radiation belts around Jupiter are so intense because Jupiter has an ENORMOUS magnetic field. The magnetic field strength at the cloud tops is ten times that of Earth and the magnetosphere also much lager that that of earth.

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Paris Hilton

Shielding Selection

I understand that Juno uses a titanium vault for the computer - well-described here - but don't quite follow the material selection. The article says lead is too soft, so presumably the vault is structural; spacecraft designers are efficient like that. But then it says, "anything else is too difficult to work with." Well, no, titanium is not fun, either. It's not as easy to machine and shape compared to aluminum and steel.

There are other issues with titanium. It's not particularly dense, and it doesn't have a particularly high atomic number, so it doesn't seem like a good choice of radiation shielding. High strength steels would be stronger, stiffer, denser, have a slightly higher atomic number, and be easier to work. Tungsten, which would be more difficult to work with than titanium, would be much denser and could be stronger. There's a whole list of alloys that seem like they'd be better choices than titanium.

But, it wouldn't be chosen at a whim. LM Space materials engineers would have done trade studies on the material selection and they'd know what a pain titanium is.

So, does anyone have a reference explaining the radiation environment or how titanium excels as shielding?

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Re: Shielding Selection

One can only guess. There are certainly more parameters, such as the thermal expansion coefficient. Other points to consider would be how brittle a material is and how well-behaved for machining (like making threads). Still another point might be that the parameters are better studied/researched than for other choices of material.

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Re: Shielding Selection

the internet tells me titanium is non-magnetic which is possibly important

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Re: Shielding Selection

There are certainly more parameters, such as the thermal expansion coefficient.

Titanium's is fairly low. I end up using it because it's close to sapphire's, but that's a very different situation than Juno.

Other points to consider would be how brittle a material is

Titanium isn't a winner in fracture toughness, but it's better than some. It keeps good properties down to extremely low temperatures, but that's not unique and Juno should never let its core get cryogenically cold - space probes aim to keep their guts at about room temperature at all times.

and how well-behaved for machining (like making threads).

Titanium is annoying to machine. It's gummy, conducts heat poorly, and doesn't generate chips cleanly. It's not a good choice for threads both because of the machining issue and its willingness to gall if you so much as wave a screw within a couple inches of it. (Easy fix: use a threaded insert.)

Still another point might be that the parameters are better studied/researched than for other choices of material.

I have selected less optimal materials because I knew them better than new unobtainiums. :) However, aerospace aluminum and steel alloys should be pretty well known by LM Space.

I wonder if it's an activation-related thing. As I recall, aluminum and some steel alloying elements may be activated by radiation bombardment (usually neutrons, but...) into radioactive isotopes, which would be awkward for radiation shielding. Maybe titanium doesn't activate and the radiation environment is such that activation is a risk.

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Re: Shielding Selection

I'd like to know too.

Titanium is 56% as dense as steel, while retaining a similar stiffness-to-weight ratio. Titanium has a high elongation number, between 20 to 30%, while typical steels are up to 15%. The lower the number the more brittle. I am wondering if the gravitational differences it might experience could have required a less brittle material. I'd love to know if this guess gets anywhere near the truth.

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Pint

Very interesting project

Will follow this with interest, as Jupiter is receding from view in my 8" scope. No doubt a lot will be learned. A pint to all the engineers and scientists who have made this possible

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All this jupiter info we'll be getting

May well destroy a book series I recall reading a *long* time ago - its somewhat vague, but involved someone becoming a benevolent dictator ruling from a moon around jupiter. It was a fun series. Can't for the life of me recall the title.

In any case, Cheers, but no beer till the orbits done. Want steady hands on those keyboards. Good luck guys and gals.

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Re: All this jupiter info we'll be getting

@ Alistair, Answer: The Sirens of Titan by Kurt Vonnegut Jr.

A good book with the introduction of a chrono-synclastic infundibulum which meant Roomford the dictator existed simultaneously at all points along the spiral that was the infundibulum.

More at https://en.wikipedia.org/wiki/The_Sirens_of_Titan.

I originally read this in the '60s.

Looking forward to viewing the data that comes back from Juno.

A late thought: why is it no one has sent something to probe Uranus?

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Re: All this jupiter info we'll be getting

"A late thought: why is it no one has sent something to probe Uranus?"

Because we're afraid of annoying Klingons?

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Re: All this jupiter info we'll be getting

Perhaps "Bio of a Space Tyrant" by Piers Anthony?

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