Wake up, dear

[softweir]

Pretty much correct, though the heating systems were left off for the entire 31 months and the CPU did nothing except check the time every 15 minutes. The heaters were only turned on during the wake-up procedure to allow the star-sighting navigation system to operate. Once the CPU knew which way it was spinning and how fast, then it could kill the spin and re-orient the craft to point the main antenna towards Earth, and then start sending a carrier wave - the least energy-consuming communications mode it has!

Energy economy is still important at this stage, because the craft is still getting considerably less sunlight than it needs to operate fully. The controllers will instruct it to activate and test systems as and when there is enough power for it to do so safely.

[lajoswinkler]

What are you proposing they're using it for, in that case? It's not like you can make bombs out of the stuff. You do realise Pu-238 and Pu-239 aren't the same, right?

They are not the same, but the political implications exist. If country A finds out that country B has a lot of some plutonium radioisotope, even if it's for RTGs and not for bombs, it can reasonably conclude that there's been a heavy purification program going on, larger than it was ever admitted. That will certainly create new diplomatic problems etc.

Pretty much correct, though the heating systems were left off for the entire 31 months and the CPU did nothing except check the time every 15 minutes. The heaters were only turned on during the wake-up procedure to allow the star-sighting navigation system to operate. Once the CPU knew which way it was spinning and how fast, then it could kill the spin and re-orient the craft to point the main antenna towards Earth, and then start sending a carrier wave - the least energy-consuming communications mode it has!

Energy economy is still important at this stage, because the craft is still getting considerably less sunlight than it needs to operate fully. The controllers will instruct it to activate and test systems as and when there is enough power for it to do so safely.

I think only the crucial parts were heated.

[Kryten]

They are not the same, but the political implications exist. If country A finds out that country B has a lot of some plutonium radioisotope, even if it's for RTGs and not for bombs, it can reasonably conclude that there's been a heavy purification program going on, larger than it was ever admitted. That will certainly create new diplomatic problems etc.

The processes for producing Pu-238 and Pu-239 are significantly different; a program to produce Pu-238 won't produce Pu-239 and vice-versa. Pu-239 is chemically separated from spent fuel rods, then it has to centrifuged to remove Pu-240. Pu-238 is produced from Np-237, which is also chemically separated from spent fuel rods (using a different process), which is then fabricated into targets and exposed to neutron bombardment, followed by yet another chemical separation process.

[sgt_flyer]

Well, nasa wants to restart pu238 production - stated quantities would be 1.5kg per year. New horizons missions used 8kg of pu238 for it's rtgs... And that was for a half ton probe which would have 190w of power when arriving at pluton.

Rosetta's weights 3 tons (1.3 tons with empty fuel tanks) bare minimal energy requirements are 390w in minimal function so the probe would need grossly 16kg of pu238 - more than 10 years of the planned US production of the stuff just to keep the bare minimum systems

Concerning the equipments on board, they had to maintain thermal regulation on the onboard fuel in addition for keeping the 'timers' warm:)

(For those who want to know, the probe use MMH and nitrogen tetroxid (hypergols) which freeze at around -50ºC for mmh, and around -10°C for the nitrogen tetroxide.)

Edited January 22, 2014 by sgt_flyer

[lajoswinkler]

The processes for producing Pu-238 and Pu-239 are significantly different; a program to produce Pu-238 won't produce Pu-239 and vice-versa. Pu-239 is chemically separated from spent fuel rods, then it has to centrifuged to remove Pu-240. Pu-238 is produced from Np-237, which is also chemically separated from spent fuel rods (using a different process), which is then fabricated into targets and exposed to neutron bombardment, followed by yet another chemical separation process.

I know but tell that to the general public and the politicians. You're forgetting about the human stupidity.

[sgt_flyer]

I know it's a two month old thread, bu i think this is relevant :

Some two days old news slipped by unnoticed on rosetta

Philae (the comet lander) has been waked up by ESA (this time, the wake up order came from earth, it was not a preprogrammed wake up time) - signal was sent at 6:00 GMT the 28th march, and esa received a reply from philae's systems at 11:35 GMT

http://www.universetoday.com/110822/esa-awakens-rosettas-comet-lander/

Rosetta also got it's first images of it's target on march 20th

http://www.universetoday.com/110761/rosetta-spacecraft-spies-its-comet-as-it-prepares-for-an-august-encounter/

Edited April 1, 2014 by sgt_flyer

[vger]

Gosh, can't wait to see photos of a comet up close.