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New Horizons: Nasa spacecraft speeds past Pluto

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Re: New Horizons: Nasa spacecraft speeds past Pluto

#291

Post by yellowapple »

scrollaway wrote: post #115
kale wrote: post #102

Earlier quoted context omitted.

What continent are you referring to that has two countries? North America has 23 countries, with the U.S.A., Canada, and Mexico being the largest countries.

Sorry, I meant two other countries and you're right; I have edited to clarify. My point was centered on borders and neighbouring countries. Do you ever see US immigration politics talking about anything else than Mexico? Canada + Mexico + the US occupy something like 95% of the landmass alone. Whenever you hear people talk about immigration in europe, we're talking about immigration from generally 5+ other countries,…

> Do you ever see US immigration politics talking about anything else than Mexico?

As a Californian: all the damn time. Mexico is the target of immigration debates because it's the U.S.'s immediate neighbor; most immigrants (legal or otherwise) from South and Central America either go through Mexico or take a boat.

North America differs from Europe only in the linear arrangement of nodes in a migration graph. In terms of origins, I reckon you're significantly downplaying the similarities.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#292

Post by dalke »

anigbrowl wrote: post #208
dalke wrote: post #129

Earlier quoted context omitted.

Competition may breed innovation, but surely it's not the truism you suggest. Sears is an example of how the introduction of internal competition does not lead to useful innovation - http://www.forbes.com/sites/stevedenning/2013/07/16/do-inter... (It may lead to increased levels of backstabbing, but that's hardly innovative.) Humans are a social species, so also have an innate nature to cooperate. Also, the concept o…

That's a very narrow and technical view of what constitutes a state, to the point of excluding ancient empires and nations like Greece, Rome, Egypt, Israel, China and others. They wouldn't meet the standards of modern statehood insofar as they lacked rigidly-defined borders or fully-developed civic institutions, but I think it's a mistake to imagine that they lacked any sense of national identity. I certainly agree t…

There was no ancient Greece nation. I suspect you mean it as a placeholder for the Hellenic era, or perhaps the kingdom Macedonia.

But as to the issue, I recently listened to a lecture about the process of deciding what the European nations would be after the First World War. The different nations had wildly different ideas of how to decide what was their national territory and people. The people of Alsace speak German, but the French said (and I paraphrase) "look at their love of wine and joie de vivre - they are French, but were forced to speak German".

Or of a farmer in central Europe, when asked "what are you?" answered "farmer", and then "where are you from?" brought the name of the local town. When asked more insistently, he said "Catholic". The concept of nation made no sense to him.

The concept of nationhood is quite complicated. Is Scotland a nation? India during the British Empire? It's more complicated than I want to get into. But in the context of the tgcordell comment, which tries to connect species imperatives with national competition, I mean to point out that the concept of 'nation' is too new to really have an evolutionary component. (And if it does, it's built on cooperation.)

I don't deny that proxy conflict can be healthy, though proxy conflict in Korea wasn't all that healthy for those involved. Is it possible to determine the healthy conflict beforehand, or is it something that's mostly done after the fact?

Re: New Horizons: Nasa spacecraft speeds past Pluto

#293

Post by blazespin »

idlewords wrote: post #234
danbruc wrote: post #228

Earlier quoted context omitted.

I fear that won't work. The speed relative to Pluto during closest approach was 13.78 meters every millisecond, I can't imagine that anything larger than a grain of sand will not behave like a liquid upon impact.

Even a grain of sand will go boom. Here's what a particle of similar size did to the space shuttle windshield, traveling at half the speed of New Horizons. https://commons.wikimedia.org/wiki/File:Space_debris_impact_...

How does new horizons survive? Space must be pretty empty.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#294

Post by idlewords »

blazespin wrote: post #293
idlewords wrote: post #234

Earlier quoted context omitted.

Even a grain of sand will go boom. Here's what a particle of similar size did to the space shuttle windshield, traveling at half the speed of New Horizons. https://commons.wikimedia.org/wiki/File:Space_debris_impact_...

How does new horizons survive? Space must be pretty empty.

That's why they call it space!

More seriously, there's a dust counter on the probe whose entire job is to be hit with stuff. But it's much tinier than a sand grain.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#295

Post by meric »

Sven7 wrote: post #154
kartikkumar wrote: post #147

Earlier quoted context omitted.

I realise that I made an unexplained logical leap to get to the last comment. Basically, based on my professional experience as a planetary scientist, it's my belief that the reason we don't have more satellites cruising through the Solar System is that we (and I mean scientists, engineers, administrators etc.) continue to fail in communicating their true value to the average person on the street. I think that media…

All you have to do is convince Kim Kardashian its important...

She can help focus half of America's population onto the problem of budgets for space exploration for all of twenty minutes.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#296

Post by JshWright »

z3t4 wrote: post #273
kartikkumar wrote: post #89

Quote from a friend of mine on the team: "After 9.5 years and 6 billion km, we made it to Pluto 72 seconds ahead of schedule." Amazing! The views of Pluto and Charon already reveal how incredibly fascinating this system is. The dichotomy of their surface colours will most definitely lead to further insight into formation processes in the Kuiper Belt. Just such a shame that we can't land this time around. With the vol…

Cant you just "dock" with the planet, by slowly matching the speed of the moving body using a Hohmann transfer!?

Yes, you could... if you were willing to wait 100+ years.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#297

Post by anigbrowl »

dalke wrote: post #292
anigbrowl wrote: post #208

Earlier quoted context omitted.

That's a very narrow and technical view of what constitutes a state, to the point of excluding ancient empires and nations like Greece, Rome, Egypt, Israel, China and others. They wouldn't meet the standards of modern statehood insofar as they lacked rigidly-defined borders or fully-developed civic institutions, but I think it's a mistake to imagine that they lacked any sense of national identity. I certainly agree t…

There was no ancient Greece nation. I suspect you mean it as a placeholder for the Hellenic era, or perhaps the kingdom Macedonia. But as to the issue, I recently listened to a lecture about the process of deciding what the European nations would be after the First World War. The different nations had wildly different ideas of how to decide what was their national territory and people. The people of Alsace speak Germ…

placeholder for the Hellenic era

Yes.

I agree with your general points, but while many people would certainly have been unaware of or indifferent to a national concept I think people in cities on major trade routes or in power centers like Rome would certainly have been aware of other places and would have been broadly aware of their own significance (although this awareness was doubtless concentrated among a social, military and business elite).

Re: New Horizons: Nasa spacecraft speeds past Pluto

#298

Post by rphlx »

TheCoreh wrote: post #269
drjesusphd wrote: post #221

Earlier quoted context omitted.

Why can't they get more?

I might be mistaken, (and someone please correct me if I'm wrong) but IIRC Plutonium is a side-product of the enrichment of weapons-grade Uranium. I think the non-proliferation of nuclear weapons treaty might impose some barriers on this process, and we're no longer in the Cold War, so it's kinda hard to get Plutonium.

Uranium enrichment is actually a physical rather than nuclear process, and thus it cannot produce other elements such as Plutonium. However once you have enriched enough uranium to create an operating reactor, its spent fuel will contain a few percent Plutonium. The problem is that only a few percent of that will be Pu-238, and separating that from the other four Pu isotopes is incredibly difficult, that is to say, economically intractable.

Therefore, the Pu-238 used in RTGs is likely produced through another process, neutron capture in Np-237. Np-237 is produced in very small amounts in a uranium reactor, but as it's the only Neptunium isotope produced in any significant quantity, there's no need to do an isotope separation on it. It can be chemically separated from the other elements in the spent fuel, which is much easier, although certainly still not easy.

In any case, with the end of the Cold War there are indeed fewer facilities willing & able to produce Pu-238 in kilogram quantities. In the US, spent fuel from commercial reactors currently cannot be re-processed at all, due to proliferation concerns.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#299

Post by TheCoreh »

rphlx wrote: post #298
TheCoreh wrote: post #269

Earlier quoted context omitted.

I might be mistaken, (and someone please correct me if I'm wrong) but IIRC Plutonium is a side-product of the enrichment of weapons-grade Uranium. I think the non-proliferation of nuclear weapons treaty might impose some barriers on this process, and we're no longer in the Cold War, so it's kinda hard to get Plutonium.

Uranium enrichment is actually a physical rather than nuclear process, and thus it cannot produce other elements such as Plutonium. However once you have enriched enough uranium to create an operating reactor, its spent fuel will contain a few percent Plutonium. The problem is that only a few percent of that will be Pu-238, and separating that from the other four Pu isotopes is incredibly difficult, that is to say, e…

Oh. Thanks for the detailed explanation and correction about the enrichment process. Do you think that once we have asteroid mining we'll be able to get Uranium (and consequently Plutonium) in higher quantities so that the economic costs will be viable again? That is assuming we can overcome the legal/security concerns by then.

Re: New Horizons: Nasa spacecraft speeds past Pluto

#300

Post by rphlx »

TheCoreh wrote: post #299
rphlx wrote: post #298

Earlier quoted context omitted.

Uranium enrichment is actually a physical rather than nuclear process, and thus it cannot produce other elements such as Plutonium. However once you have enriched enough uranium to create an operating reactor, its spent fuel will contain a few percent Plutonium. The problem is that only a few percent of that will be Pu-238, and separating that from the other four Pu isotopes is incredibly difficult, that is to say, e…

Oh. Thanks for the detailed explanation and correction about the enrichment process. Do you think that once we have asteroid mining we'll be able to get Uranium (and consequently Plutonium) in higher quantities so that the economic costs will be viable again? That is assuming we can overcome the legal/security concerns by then.

That's a good question - AFAIK nobody has any real idea how much Uranium is present within nearby asteroids. Hopefully they will create some more RTGs & send some probes to find out!
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