New Horizons Arrives At Ksc Options

[Guest_Sunspot_*]

I understand your anger, Doug. But usually it is polluters and authors of catastrophes who spread misinformation, to justify their shemes or to escape punishment.

... I distinctly remember seeing and hearing a women in a news report leading upto the launch saying they "had embarked on a campaign on misinformation" to get NASA's attention. How can you expect people to make a decision on an issue when they're being lied to? As much as I support environmental concerns and issues, enviromental groups are notoriously loose with scientific facts - thanks in part to the publics disinterest and ignorance of science.

[helvick]

It is slow enough to allow Cassini (and Pioneer and Voyager) to work, but Cassini will be very probably out of power before being out of nuclear fuel.

You're quite right - even though these are solid state devices there is some level lof degradation over time which is why I said that it follows the half of Pu-238 more or less.

Its a long time since I did any nuclear physics but I don't recall that there are any Neutrons emitted as part of the Pu-238 decay cycle. (Pu238->U235+Alpha and all subsequent decays are "Nasty Radioactive Isotope"+Alpha|Beta|Gamma ... Lead). It's still a stressful environment for the thermocouple but the dominant component of the loss of power should be the fuel's half life.

[Guest_Richard Trigaux_*]

As much as I support environmental concerns and issues, environmental groups are notoriously loose with scientific facts - thanks in part to the publics disinterest and ignorance of science.

Alas this is often true.

I think science should be learned into primary school, there is no need to be a graduate to understand most basic facts. People understanding the world in which they are living are, I think, less prone to violence or fanaticism.

About environment, it is often scientists who first ring the alarm. Only after environmentalist develop these concerns in a more pro-social perspective. So ecology owes nearby everything to science. But despites this I knew environmentalist who were really anti-science. And really uninformed about it.

[Guest_Richard Trigaux_*]

You're quite right - even though these are solid state devices there is some level lof degradation over time which is why I said that it follows the half of Pu-238 more or less.

Its a long time since I did any nuclear physics but I don't recall that there are any Neutrons emitted as part of the Pu-238 decay cycle. (Pu238->U235+Alpha and all subsequent decays are "Nasty Radioactive Isotope"+Alpha|Beta|Gamma ... Lead). It's still a stressful environment for the thermocouple but the dominant component of the loss of power should be the fuel's half life.

Pu238 undergo a very small percentage of spontaneous fission, see here even more than Pu239. So we can expect that there are neutrons. I also remembered when I worked about this I saw a Cassini radiation map, indicating a neutron flux centered on the RTGs. Weak, but enough to damage certain electronic parts in the long run. This is the reason why the RTGs are often mounted at the end of long booms. For NH it is much closer, I am astonished. Perhaps electronic components are better today.

[Guest_BruceMoomaw_*]

"... I distinctly remember seeing and hearing a women in a news report leading upto the launch saying they 'had embarked on a campaign on misinformation' to get NASA's attention. How can you expect people to make a decision on an issue when they're being lied to? As much as I support environmental concerns and issues, enviromental groups are notoriously loose with scientific facts - thanks in part to the public's disinterest and ignorance of science."

Unfortunately, they are hardly alone in that regard. It was Dean Acheson -- remembered as being one of the more enlightened Secretaries of State -- who said that the government frequently has the obligation to make things "clearer than the truth" to the voters in order to get their support for its Enlightened Policies.

[ljk4-1]

"... I distinctly remember seeing and hearing a women in a news report leading upto the launch saying they 'had embarked on a campaign on misinformation' to get NASA's attention. How can you expect people to make a decision on an issue when they're being lied to? As much as I support environmental concerns and issues, enviromental groups are notoriously loose with scientific facts - thanks in part to the public's disinterest and ignorance of science."

Unfortunately, they are hardly alone in that regard.  It was Dean Acheson -- remembered as being one of the more enlightened Secretaries of State -- who said that the government frequently has the obligation to make things "clearer than the truth" to the voters in order to get their support for its Enlightened Policies.

In the same vein - Jeff Foust once relayed to me that he attended an anti-Cassini rally in Cambridge, MA in 1997, just before it was launched. He was the only pro-space person in attendance. One woman actually told him that she did not want to know the facts, as she had already made up her mind about Cassini and because it was nuclear-powered, it was therefore bad and had to be stopped.

And we wonder why truly intelligent beings from other worlds will not contact us.

[Mark6]

Actually, the blood-chilling thing about "nucular" is how many non-Bushians pronounce it the same way -- including Tony Blair, Walter Mondale, and (as the supreme insult) Clinton's first Defense Secretary, Les Aspin.  A DEFENSE SECRETARY who can't say "nuclear" is a bit much.  And what the hell was Tony learning in those pricey private schools, besides a plummy accent?

Carter pronounced it the same way, and he is an actual nuclear engineer!

[spfrss]

If you go to

http://www.pluto.jhuapl.edu/overview/deis/intro.html

you can read the Draft Environmental Impact Statement about NH

Live long and prosper

Mauro

[Guest_Richard Trigaux_*]

Its a long time since I did any nuclear physics but I don't recall that there are any Neutrons emitted as part of the Pu-238 decay cycle. (Pu238->U235+Alpha and all subsequent decays are "Nasty Radioactive Isotope"+Alpha|Beta|Gamma ... Lead). It's still a stressful environment for the thermocouple but the dominant component of the loss of power should be the fuel's half life.

There is not only Pu238 in the RTGs. Pu238 is not produced from isotopic separation from other Pu isotopes. This process would be very difficult and anyway not complete, lefting an amount of Pu239 and even Pu240. It fact it seems that they start from Neptunium. There are only two "stable" isotopes of Np: 236 and 237, and they are much easier to extract from ordinary nuclear wastes of electricity reactors. Then they irradiate this neptunium into a special nuclear reactor, where it absorbs neutrons until it forms Np238 which quickly beta decays into Pu 238. But the time this pu238 remains in the reactor, it can in turn transmute into Pu239 and even Pu240. So whatever the method, there is a percentage of Pu239 in the Pu238. They certainly try to minimize it, as it does not produce heat, but it cannot be completelly avoided. It is like that, in nuclear physics even a theoretically "clean" reaction often has parasitic minority paths which can be very harmful.

So the presence of Pu239 is enough to explain that the RTGs emit neutrons. The other rays (alpha or beta) are damped by the casing before reaching the thermocouples.

Another consequence of this is that the RTGs are not just recycled nuclear wastes, they require the production of other nuclear wastes to be manufactured, so they arise the same issues than the nuclear reactors. The only white point is that the RTGs fuel cannot be used to make bombs, in case it falls into bad hands.

[ljk4-1]

Carter pronounced it the same way, and he is an actual nuclear engineer!

When Blair was interviewed about the Huygens landing on Titan, he readily confessed he wasn't into science in school and learned very little on the subject as a whole as a result.

It's sad how when it comes to science, people almost brag about their ignorance on the subject. May explain the current state of the world.

[Guest_Richard Trigaux_*]

When Blair was interviewed about the Huygens landing on Titan, he readily confessed he wasn't into science in school and learned very little on the subject as a whole as a result.

It's sad how when it comes to science, people almost brag about their ignorance on the subject.  May explain the current state of the world.

It is still worse than that: Huygens is not just about science, it is our first landing on a completelly unknown world, ant it has many enthraling philosophical implications and is a mater of strong poetical/existential emotion. And these concerns are for everybody, not just for scientists or amateur astronomers like on this forum. I wonder if people who feel nothing about space exploration are really incarnated on our planet, or if they are hovering somewhere above (or under). "Ooooh, Huygens, it is about Saturn, so it is about science, very complicated, headache and all, oooh" (This post is not specially aimed at Mr Blair and other politicians, there are many street populists who are much worse)

[mchan]

In the latest PI update, Alan Stern describes NH's journey to KSC including a close encounter with a reckless driver.

http://pluto.jhuapl.edu/overview/piPerspective_current.html

Mike

[Guest_Richard Trigaux_*]

In the latest PI update, Alan Stern describes NH's journey to KSC including a close encounter with a reckless driver.

Frightening to think that the Pluto mission could have finished in a traffic crash. A meteorite in space w<ould be more romantic.


The classification of reckless drivers encounters:
First kind close encounter: just fear
Second type close encouter: bolts and nuts smashed.
Third type close encounter: humanoids injuried.

[Rob Pinnegar]

Frightening to think that the Pluto mission could have finished in a traffic crash. A meteorite in space would be more romantic.

Heh, heh. Funny how this dovetails nicely with the sub-thread Mike started a while back. Buddy was probably rushing home to avoid missing this week's WWE Smackdown. He'll probably never know how close he came to actually doing something significant (although in a negative way).

It's a pity that the cops weren't able to pull him over. It can't be often that they get the opportunity to ticket someone for endangering a United States spacecraft.

Switching topics: Does anyone happen to know how reliable the launch vehicle for New Horizons (Atlas-Centaur-STAR) is thought to be? How many previous missions have used this configuration?

[mchan]

Switching topics: Does anyone happen to know how reliable the launch vehicle for New Horizons (Atlas-Centaur-STAR) is thought to be? How many previous missions have used this configuration?

No previous mission has used the exact configuration that NH is using (Atlas-V with 5 SRB's, Centaur, Star-48). The NH FEIS gives a estimate of 93.8% of a "successful launch leading to Pluto trajectory". That number was calculated before the successful launch of MRO, so a revised calculation with the other factors unchanged will yield a higher estimate of success.

There have been 6 launches of Atlas-V to date, but the first time for a new configuration always has the potential for something that was not thought of beforehand. This launch will likely have more than the usual reviews to reduce the potential of missing something.

-Mike