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» Ship of Fools   »   » Oblivion   » It ain't the kind of place to raise your kids? (Page 2)

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Source: (consider it) Thread: It ain't the kind of place to raise your kids?
Kaplan Corday
Shipmate
# 16119

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quote:
Originally posted by LeRoc:
Isn't the capitalist system supposed to be promoting innovation, moving humanity forward?

It was communism which promoted innovation and moved humanity forward by producing the first astronaut.

Just sayin'.

[ 31. March 2016, 23:33: Message edited by: Kaplan Corday ]

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Alan Cresswell

Mad Scientist 先生
# 31

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quote:
Originally posted by LeRoc:
quote:
HCH: It is quite possible that human beings will not be able to colonize Mars due to its light gravity. By now there is quite a lot of data available about the effects of zero-G, but low-G is more of a mystery.
Interesting. Are you expecting low-G to be much different from zero-G? What this tells me that it might be better to experiment with the Moon first. (At least we won't have to deal with launch windows.)
There are several good reasons for starting with the Moon. Better understanding of the effects of low term low-G would be one of them (when it comes down to it we only know about the effects of zero-G on a small number of individuals for a few months - and would low-G be similar but less intense or would we find entirely new effects?).

It would be a test bed for habitats - testing on Earth is good, but ultimately if something goes wrong you just open the door. And, psychology, put a habitat on the dark side and add a few minutes delay to communications. How do people react to that non-instant communication and not being able to look out of the window to see home? Yes, there aren't many launch window restrictions. But, we could always add in a delay so that the Lunar test subjects still have to live with the "we'll get it to you in 30 months" if they forgot something.

At a practical level, if (and, it's an if) a lunar colony can mine materials and construct components of the Mars mission spaceships it will significantly reduce the amount of material we'd need to lift out of our gravity well. If the lunar colonists can mine and enrich uranium that would remove the launch risks of the reactors needed. And, if the effects of lunar gravity on health are minor, it might be possible to run the rotating tether proposed to simulate gravity on the Mars flights at a lower speed, reducing the strain on the tether and the fuel needed to accelerate/decelerate the rotation.

Also the prospect of bring raw materials to earth from the moon (which, we're not going to do from Mars for several decades, if at all) might be sufficient for private investment in the launch and habitat facility development - money that won't need to be found again for Mars.

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Don't cling to a mistake just because you spent a lot of time making it.

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Pigwidgeon

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# 10192

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quote:
Originally posted by LeRoc:
BTW Earlier on this thread I referred to the 'Earthrise' photograph. I just realised that mr cheesy uses it as his Ship avatar.

So does Soror Magna.

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"...that is generally a matter for Pigwidgeon, several other consenting adults, a bottle of cheap Gin and the odd giraffe."
~Tortuf

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Penny S
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# 14768

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There does seem to be a small problem in the mining stuff direction, as most Earth type deposits of useful stuff seem to have been formed as a result of activity associated with a) plate tectonics, and b) water. And, yes, I realise that plate tectonics itself depends on water, but the concentration and deposition of minerals depends on much more intimate connections between the stuff and the water. Uranium, I seem to recall, needs a change in pH to precipitate dissolved metal from solution into ore bodies.
The Moon is rather short of water. Ditto Venus. Ditto Mars.
Iron and alloyed metals are available from asteroids formed by the breaking up of bodies which were large enough to form cores, but would need a lot of work to separate elements out.

[ 01. April 2016, 05:48: Message edited by: Penny S ]

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Boogie

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# 13538

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quote:
Originally posted by Huia:
Oh goody! A whole new planet for people to ruin. One was not nearly enough [Roll Eyes]

I doubt if the planet will care either way.

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Garden. Room. Walk

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Martin60
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# 368

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It ain't gonna happen.

EVER.

Like commercial fusion.

Ever.

Utter childish fantasy.

Here's another: snake oil power.

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Love wins

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Ariel
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# 58

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quote:
Originally posted by LeRoc:
It's two weeks of light, two weeks of dark. And I imagine that people will be living underground anyway?

It sounds even more alluring. Not only are you on a cold dead planet with no seasons, you’re now stuck underground with no natural light and no view.

quote:
From Hedgehog]
Considering there are cities on Earth (like Trondheim, Norway) that only get about ten hours of daylight in all of December, I suspect people could adjust.

Yes, however the Arctic Circle isn’t most people’s choice of place to migrate to. And the lack of sunlight adds to the depression factor. The only way people could cope with living on the Moon would be to make the conditions as Earth-like as possible, in which case you might just as well stay on Earth.
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LeRoc

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quote:
Ariel: It sounds even more alluring. Not only are you on a cold dead planet with no seasons, you’re now stuck underground with no natural light and no view.
But think about the low-G sex!

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I know why God made the rhinoceros, it's because He couldn't see the rhinoceros, so He made the rhinoceros to be able to see it. (Clarice Lispector)

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Boogie

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# 13538

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quote:
Originally posted by Martin60:
It ain't gonna happen.

EVER.

Like commercial fusion.

Ever.

Utter childish fantasy.


Never say never. Think of the things we use routinely now and once thought were science fiction - even in our own lifetimes. (eg computer in your pocket which can make face-to-face calls to anyone)

[ 01. April 2016, 07:40: Message edited by: Boogie ]

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Garden. Room. Walk

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Ariel
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# 58

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quote:
Originally posted by LeRoc:
But think about the low-G sex!

I'd rather not, thank you.
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SusanDoris

Incurable Optimist
# 12618

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quote:
Originally posted by Lamb Chopped:
Why is it so important to preserve the species?

It is only important to us humans of course! That is why humans of the future will do everything they can to remove at least some of us to somewhere we stand a chance of not being annihilated.

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I know that you believe that you understood what you think I said, but I am not sure you realize that what you heard is not what I meant.

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Alan Cresswell

Mad Scientist 先生
# 31

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quote:
Originally posted by Boogie:
Think of the things we use routinely now and once thought were science fiction - even in our own lifetimes. (eg computer in your pocket which can make face-to-face calls to anyone)

I've heard it said that if you brought someone from Victorian London and showed them the latest smartphone they'd be impressed at our ability to access the sum total of human knowledge from anywhere. And, totally bemused that we use it to share photos of cats.

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Don't cling to a mistake just because you spent a lot of time making it.

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Alan Cresswell

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# 31

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quote:
Originally posted by Ariel:
quote:
Originally posted by LeRoc:
It's two weeks of light, two weeks of dark. And I imagine that people will be living underground anyway?

It sounds even more alluring. Not only are you on a cold dead planet with no seasons, you’re now stuck underground with no natural light and no view.
When it comes down to it, the Moon is an extremely hostile environment, only marginally less hostile than open space (the Moon, at least, has some gravity and half the time you're shielded from solar radiation). And, the psychological aspects of living there are certainly part of the hostility of the environment. You may as well be sitting in a tin can, far above the Earth.

Mars is a bit less hostile. The gravity is higher. There's an atmosphere, if a thin one, to provide some protection from radiation - and, being further from the Sun there's less radiation. On the other hand, there's enough atmosphere to whip up some very nasty sand storms.

It will take a particular kind of person to survive, let alone enjoy, the experience of living in either place. Probably most of us do not have the right stuff.

--------------------
Don't cling to a mistake just because you spent a lot of time making it.

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LeRoc

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quote:
Penny S: There does seem to be a small problem in the mining stuff direction, as most Earth type deposits of useful stuff seem to have been formed as a result of activity associated with a) plate tectonics, and b) water.
I don't think people are thinking about mining for iron or something like that on the moon. As you said, better go to the asteroids for that.

What's mostly being talked about is deploying machines like this to scrape off the rocks and sand and extract stuff like phosphorus and potassium from there. Hardly worth sending to Earth, but invaluable for the Loonies when they want to start their hydroponics agriculture.

quote:
Originally posted by Pigwidgeon:
quote:
Originally posted by LeRoc:
BTW Earlier on this thread I referred to the 'Earthrise' photograph. I just realised that mr cheesy uses it as his Ship avatar.

So does Soror Magna.
I know. I was looking at people who had posted on this thread.

quote:
Alan Cresswell: There are several good reasons for starting with the Moon.
Besides the ones you mentioned, I don't think we should underestimate the psychological effect it will have on people back on Earth to have people living on the Moon.


(PS I like some of the pop culture references on this thread!)

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I know why God made the rhinoceros, it's because He couldn't see the rhinoceros, so He made the rhinoceros to be able to see it. (Clarice Lispector)

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Martin60
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# 368

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quote:
Originally posted by Boogie:
quote:
Originally posted by Martin60:
It ain't gonna happen.

EVER.

Like commercial fusion.

Ever.

Utter childish fantasy.


Never say never. Think of the things we use routinely now and once thought were science fiction - even in our own lifetimes. (eg computer in your pocket which can make face-to-face calls to anyone)
It's ALL about energy scale. We can be as accumulatively clever as we like for as long as we like it will make NO dent on fusion or colonizing the solar system let alone beyond.

Other vanity projects like AI and matter transmission are just as absurd.

--------------------
Love wins

Posts: 17586 | From: Never Dobunni after all. Corieltauvi after all. Just moved to the capital. | Registered: Jun 2001  |  IP: Logged
Crœsos
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# 238

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quote:
Originally posted by Alan Cresswell:
When it comes down to it, the Moon is an extremely hostile environment, only marginally less hostile than open space (the Moon, at least, has some gravity and half the time you're shielded from solar radiation). And, the psychological aspects of living there are certainly part of the hostility of the environment. You may as well be sitting in a tin can, far above the Earth.

Mars is a bit less hostile. The gravity is higher. There's an atmosphere, if a thin one, to provide some protection from radiation - and, being further from the Sun there's less radiation. On the other hand, there's enough atmosphere to whip up some very nasty sand storms.

It will take a particular kind of person to survive, let alone enjoy, the experience of living in either place. Probably most of us do not have the right stuff.

This seems to be the biggest obstacle to any effort to build an actual colony (as opposed to a research base or some kind of mining/extraction outpost) on Mars. Humans tend not to do that sort of thing. There are lots of hostile environments right here on Earth (though less hostile than Mars). When humans discover some reason to go to those places they usually don't build a self-sustaining city there. They usually build a temporary outpost sufficient to whatever purpose they have for going there and rotate a crews in and out. Think of offshore oil platforms, or Antarctic research bases. A self-sustaining colony worthy of the name is several orders of magnitude more complicated than these kinds of outposts.

Given our reluctance to "colonize" the Gobi or Sahara (for example), why do people think there's a huge demand for colonizing Mars?

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Humani nil a me alienum puto

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Martin60
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# 368

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We're in the shaded bit of this where the x-axis is energy and the y is complexity as to what's EVER achievable. The z-axis perpendicular to this is time. Shrink to a dot and that's us 200,000 years ago. Expand to a postage stamp and that's where we're at. We've gone from banging rocks together to detonating the Tsar-bomba on the horizontal. Heating water with hot rocks in unglazed pots to Lacanian analysis on the vertical (I'm open to better). Time is also synonymous with population.

Archimedes lever is forever out there, along with fusion, radio frequency cavity thrust propulsion and social justice.

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Love wins

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LeRoc

Famous Dutch pirate
# 3216

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quote:
Martin60: We're in the shaded bit of this where the x-axis is energy and the y is complexity as to what's EVER achievable.
So, we can do low-energy complex things and high-energy simple things?

--------------------
I know why God made the rhinoceros, it's because He couldn't see the rhinoceros, so He made the rhinoceros to be able to see it. (Clarice Lispector)

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Alan Cresswell

Mad Scientist 先生
# 31

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In scientific research proposals there's a description that describes an idea on a 'difficulty' scale (x: easy to impossible) and an 'interest' scale (y: mundane to world-breaking exciting). Research proposals that are both world-breaking exciting and very easy are the cash-cow (low risk, high gain). Mundane but very difficult are probably best avoided (high risk, low gain). Some scientists relish the world-breaking and very difficult (high gain, high risk) probably much the same way as gamblers love the roulette wheel. However, most of us live in the bottom left corner of "not too difficult" and "not too exciting", the low risk low gain world of bread-and-butter work.

I would say that that is fairly true of everyone.

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Don't cling to a mistake just because you spent a lot of time making it.

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Martin60
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# 368

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quote:
Originally posted by LeRoc:
quote:
Martin60: We're in the shaded bit of this where the x-axis is energy and the y is complexity as to what's EVER achievable.
So, we can do low-energy complex things and high-energy simple things?
EXACTLY LeRoc. There are NO exceptions. As NASA says: Faster, Better, Cheaper; choose two of the above.

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Love wins

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Martin60
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# 368

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Archimedes' ... complexity eh?

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Love wins

Posts: 17586 | From: Never Dobunni after all. Corieltauvi after all. Just moved to the capital. | Registered: Jun 2001  |  IP: Logged
Russ
Old salt
# 120

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quote:
Originally posted by Boogie:

We humans need goals and aims or we tend to turn in on each other.

Yes.

We need to be contending with, exercising power over, the universe. As long as the alternative is contending with and exercising power over each other.

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Wish everyone well; the enemy is not people, the enemy is wrong ideas

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rolyn
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# 16840

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When we thought Mars might be inhabited with beings who meant us harm we had a tendency to fight each other .
Now that we know ourselves to be alone in our Solar System, and possibly in the wider Universe, we might possibly be starting to think what's the bloomin point in fighting, controlling, and exerting power over eachother .....Well some of us, in theory at least [Roll Eyes]

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Change is the only certainty of existence

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Alan Cresswell

Mad Scientist 先生
# 31

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quote:
Originally posted by Martin60:
As NASA says: Faster, Better, Cheaper; choose two of the above.

And, if you choose "cheaper" then you only get one choice.

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Don't cling to a mistake just because you spent a lot of time making it.

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Martin60
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# 368

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Aye. It'll be crap. Throwing trillions at any and all of the axes won't make fusion or AI or space-faring work. Throwing it up the y-axis IS slowly (z) making inroads in cancer and even dementia by the end of the century. Arthritis? Social justice? Not a chance. Not a hope in hell. Islamic terrorism in response to materialist interference? It all has to be bred out of us.

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Love wins

Posts: 17586 | From: Never Dobunni after all. Corieltauvi after all. Just moved to the capital. | Registered: Jun 2001  |  IP: Logged
Alan Cresswell

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# 31

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If not Mars, how about the stars?

OK, not a crewed mission. But, Stephen Hawking thinks we can send small star ships to other star systems within 30 years.

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Don't cling to a mistake just because you spent a lot of time making it.

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LeRoc

Famous Dutch pirate
# 3216

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quote:
Alan Cresswell: But, Stephen Hawking thinks we can send small star ships to other star systems within 30 years.
Phrasing it a bit more clearly, I think he says these ships will take 30 years to get there. This means that they'd be travelling at near-relativistic speeds. I don't think they would have a way of braking when they arrive at α Centauri, so they'd need cameras with very fast shutter times [Smile]

Did I get it right that these lasers will only need to fire for a couple of minutes?

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I know why God made the rhinoceros, it's because He couldn't see the rhinoceros, so He made the rhinoceros to be able to see it. (Clarice Lispector)

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Alan Cresswell

Mad Scientist 先生
# 31

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quote:
Originally posted by LeRoc:
quote:
Alan Cresswell: But, Stephen Hawking thinks we can send small star ships to other star systems within 30 years.
Phrasing it a bit more clearly, I think he says these ships will take 30 years to get there. This means that they'd be travelling at near-relativistic speeds.
4.4 light years, 30 year trip gives an average speed of 15% light speed. Not relativistic, but faster than any other object we've put into space (or, for that matter, any other object that we know of that's not a subatomic particle).

quote:
I don't think they would have a way of braking when they arrive at α Centauri, so they'd need cameras with very fast shutter times [Smile]
If they could refurl the solar sail once on their way, then unfurling it would give a brake, but it won't be enough to slow the probe very much (unless someone conveniently puts a laser out there for us). If it isn't slowed it will take about 10h to traverse the inner solar system (inside the orbit of Jupiter). If it's solar powered there isn't going to be power to do anything much from further out than that, or probably even that far out. Which is not going to reveal very much from an ultra small aperture camera.

quote:
Did I get it right that these lasers will only need to fire for a couple of minutes?
That's going to depend on the mass of the probe and the power of the laser.

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Don't cling to a mistake just because you spent a lot of time making it.

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LeRoc

Famous Dutch pirate
# 3216

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quote:
Alan Cresswell: [...] 15% light speed. Not relativistic [...]
That's why I said near-relativistic [Smile]

quote:
Alan Cresswell: That's going to depend on the mass of the probe and the power of the laser.
I've been fiddling around a bit. I started with 1 kg for the chip including a sail and a camera, and a 10 minute laser burst. This means that we'd need a 3 terawatt laser. We have those, but they normally only fire for nanoseconds. The energy required is huge.

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I know why God made the rhinoceros, it's because He couldn't see the rhinoceros, so He made the rhinoceros to be able to see it. (Clarice Lispector)

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Alan Cresswell

Mad Scientist 先生
# 31

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Or, turn the equation around. The current most powerful (near) continuous laser is a bit over 1MW. If we assume we can scale that up to 10MW quite easily, how long would we need to fire it to accelerate a 1kg mass of 15% light speed? Assuming 100% efficiency in energy transfer I get 675,000 years!

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Don't cling to a mistake just because you spent a lot of time making it.

Posts: 32413 | From: East Kilbride (Scotland) or 福島 | Registered: May 2001  |  IP: Logged
LeRoc

Famous Dutch pirate
# 3216

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quote:
LeRoc: The energy required is huge.
Okay, I did a follow-up calculation. For 1 minute and 45 seconds we turn off all energy in the world and channel that into a 17 TW laser. That would do it [Smile]


[ETA: Cross-posted.]

[ 13. April 2016, 11:28: Message edited by: LeRoc ]

--------------------
I know why God made the rhinoceros, it's because He couldn't see the rhinoceros, so He made the rhinoceros to be able to see it. (Clarice Lispector)

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Alan Cresswell

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# 31

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I think that basically Hawking needs to redo his maths. Making the craft smaller only has a small effect. Reducing the maximum speed would be more effective - but then you're talking centuries to make the journey, not 30 years.

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Don't cling to a mistake just because you spent a lot of time making it.

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Dave W.
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# 8765

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The NYTimes has an article with more detail and a link to the project's web site.

They're talking about "nanocraft" with a mass of ~1 gram propelled to 0.2c by a mile-wide 100 GW laser array.

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Alan Cresswell

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# 31

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If they can build a probe able to collect useful data and transmit it back to Earth with a total mass of 1g (including the solar sail), and they can produce a sustained 100GW laser beam, and they get a conversion efficiency of 10% of laser power to kinetic energy ... then, 3-5* minutes of laser on sail will get them to 0.2c.

* 3 minutes for classical mechanics, I can't be bothered to work out the Relativistic effects considering how big those 'if's' are.

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LeRoc

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# 3216

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quote:
Alan Cresswell: * 3 minutes for classical mechanics, I can't be bothered to work out the Relativistic effects considering how big those 'if's' are.
I think the difference at these speeds will only be a couple of per cent at most.


We'd also need to find a way to stop people from using this laser to carve their name in the Moon [Smile]

(I still think it's good that people think of this kind of thing though.)

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I know why God made the rhinoceros, it's because He couldn't see the rhinoceros, so He made the rhinoceros to be able to see it. (Clarice Lispector)

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Green Mario
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# 18090

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This is a fascinating idea and seems plausible - ditch the need to carry fuel, tiny probe and huge speeds become possible with realistic amounts of energy.

What I don't get is how they will be able to transmit information back from 4 light years away from the transmitter on a 1g probe. Even allowing for improvements in technology there must be physical limits in terms of energy and strength of signal.

The probe sending information back from Pluto had quite a large transmitter - from the looks of the picture, and a decent source of power (well 200W) and because of the distance could only transmit back a very weak signal Pluto Probe; which meant using massive receivers to listen and transferring data slowly.

The nearest star is over 5000 times further away than Pluto, and presumably the signal strength will decrease with the square of distance??

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LeRoc

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# 3216

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They're planning on using nuclear decay for power, just as in smoke detectors. I don't know much about what kind of power would be needed; I'll try to look up something about this.


(PS Quickly coming back to lasers, the Titan Laser located at Lawrence Livermore National Laboratory in California for less than a picosecond uses 76 times as much energy as the rest of the world combined. Maybe someone should go and talk with them.)

[ 13. April 2016, 20:36: Message edited by: LeRoc ]

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I know why God made the rhinoceros, it's because He couldn't see the rhinoceros, so He made the rhinoceros to be able to see it. (Clarice Lispector)

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Lamb Chopped
Ship's kebab
# 5528

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quote:
Originally posted by LeRoc:
But think about the low-G sex!

I think one would have a tendency to become uncoupled rather easily.

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Er, this is what I've been up to (book).
Oh, that you would rend the heavens and come down!

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Martin60
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# 368

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quote:
Originally posted by Alan Cresswell:
If they can build a probe able to collect useful data and transmit it back to Earth with a total mass of 1g (including the solar sail), and they can produce a sustained 100GW laser beam, and they get a conversion efficiency of 10% of laser power to kinetic energy ... then, 3-5* minutes of laser on sail will get them to 0.2c.

* 3 minutes for classical mechanics, I can't be bothered to work out the Relativistic effects considering how big those 'if's' are.

How many 'g' is that? And how much heat? Surely you'd have to ablate a meter thick tungsten disk?

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Love wins

Posts: 17586 | From: Never Dobunni after all. Corieltauvi after all. Just moved to the capital. | Registered: Jun 2001  |  IP: Logged
Alan Cresswell

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# 31

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It's 10000-15000g, for 3-5 minutes of acceleration.

For maximum efficiency you want the sail to reflect the laser light without heating. You can have a drive that evaporates when hit by the laser, if you focus the plasma generated it will contribute to the thrust - but, then you have added fuel (and a lot of mass) to the probe.

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Don't cling to a mistake just because you spent a lot of time making it.

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Alan Cresswell

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# 31

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quote:
Originally posted by Alan Cresswell:
It's 10000-15000g, for 3-5 minutes of acceleration.

Just noticed the NYT article has 60000g. That's higher because a) they envisage only 2mins of acceleration, b) I haven't accounted for the small Relativistic effect and c) as the probe gets further from Earth (which will happen very quickly) the power delivered by the laser will fall off, so the initial acceleration will be much higher. Still, a very high acceleration that will require some engineering (and, that means mass) to ensure the probe doesn't break apart - in particular that it stays attached to the sail.

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Don't cling to a mistake just because you spent a lot of time making it.

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Alan Cresswell

Mad Scientist 先生
# 31

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quote:
Originally posted by LeRoc:
They're planning on using nuclear decay for power, just as in smoke detectors. I don't know much about what kind of power would be needed; I'll try to look up something about this.

The NYT article mentions Americium (the element in smoke detectors), which is an interesting choice of isotope. Conventional RadioThermal Generators (RTGs) such as the one on New Horizons use 238Pu, with an 88 year half life. 241Am has a longer (433y) half life, so you would need 5 times the mass to give the same energy. You gain a power supply that doesn't produce significantly less power over the mission duration (238Pu would decay by 15% over 20y, 241Am by 5%), but in a mass critical application I would go with starting with 20% more 238Pu than needed for the mission end than 5x the mass. 241Am is more readily available and cheaper.

That's before you've worked out how much you need. RTGs surround the isotope with material that is heated by the decay of the isotope, and then a thermo-electric converter. This is simple and reliable technology, but not very efficient (the RTG on New Horizons generates 4000W of heat, 200W of electricity) and heavy (10-20kg). Also, there isn't really any other technology to convert radioactive decay energy to electricity. Which makes it the obvious choice for applications like New Horizons. I have no idea if it's even possible to scale such a generator down to 500mg or less (so it's less than half the mass of the probe), especially if it needs to power an interstellar transmitter.

The New Horizons probe has a ~2m dish and about transmits at about 100W. If a micro-transmitter can produce a focussed signal with a tighter beam than New Horizons, and the amount of data that needs to be transmitted is much less, then a smaller power will work. But, I'd guess at 10W rather than 1W or less. But, let's be generous, and say the probe can operate on 1W (the majority being the transmitter), how big an RTG would it need? Assuming a much higher efficiency than current systems, let's say 5W thermal for 1W electrical, that's an activity of ~5TBq. That comes out to about 8g of 238Pu, or 40g of 241Am. Which is never going to fit in a ~1g probe!

So, from the other end. 250mg of 238Pu will generate 150mW thermal, if they're lucky 50mW electrical. Probably no more than 25mW available for the transmitter ...

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my working ...

each decay produces ~5.5MeV alpha particle and we capture the majority of that energy
1eV = 1.6x10^-19 J, 5MeV = 8*10^-13 J (let's call it 10^-12 J)
5W = 5J/s = 5/10^-12 alphas per sec = 5x10^12Bq (5TBq)

decays per sec = N(1-e^-lambda) - where N is number of nuclei
For 238Pu, t1/2 = 88y, 2.8x10^9s
decay constant lambda = ln2/t1/2 = 2.5x10^-10 s-1
thus (1-e^-lambda) = 2.5x10^-10
and, N = 5x10^12/2.5x10^-10 = 2x10^22
mass of each nuclide = 238*1.7x10^-27kg = 4x10^-25 kg
Therefore mass of 238Pu = 2x10^22 * 4x10^-25 = 0.008kg

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Don't cling to a mistake just because you spent a lot of time making it.

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LeRoc

Famous Dutch pirate
# 3216

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Yeah, overall it seems to be nice what-if thinking. (And by all means let them think further about it, who knows in which other ways it might help.)

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I know why God made the rhinoceros, it's because He couldn't see the rhinoceros, so He made the rhinoceros to be able to see it. (Clarice Lispector)

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LeRoc

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# 3216

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quote:
Lamb Chopped: I think one would have a tendency to become uncoupled rather easily.
I understand it involves a lot of elastic bands.

There seems to be an official NASA ban on sex on the ISS. But there have been rumours …

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I know why God made the rhinoceros, it's because He couldn't see the rhinoceros, so He made the rhinoceros to be able to see it. (Clarice Lispector)

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Martin60
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# 368

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So, it's utter, UTTER twaddle, kid's stuff, hype as bad as the Martian fossil, as useless as hot fusion let alone cold and RF resonant cavity thrusters.

Way out on the x=y line on the hyperbolic paraboloid.

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Love wins

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Doublethink.
Ship's Foolwise Unperson
# 1984

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The problem with colonisation of another planet, is the fairly inevitable war we will end up having with it when it becomes successful enough to want independence.

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All political thinking for years past has been vitiated in the same way. People can foresee the future only when it coincides with their own wishes, and the most grossly obvious facts can be ignored when they are unwelcome. George Orwell

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Martin60
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# 368

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60K g needs the robustness of a Luger bullet. A wristwatch can take 5K

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Love wins

Posts: 17586 | From: Never Dobunni after all. Corieltauvi after all. Just moved to the capital. | Registered: Jun 2001  |  IP: Logged
LeRoc

Famous Dutch pirate
# 3216

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quote:
Doublethink.: The problem with colonisation of another planet, is the fairly inevitable war we will end up having with it when it becomes successful enough to want independence.
The Moon is a Harsh Mistress.

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I know why God made the rhinoceros, it's because He couldn't see the rhinoceros, so He made the rhinoceros to be able to see it. (Clarice Lispector)

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LeRoc

Famous Dutch pirate
# 3216

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quote:
Martin60: 60K g needs the robustness of a Luger bullet.
I thought that rifle bullets regularly have an acceleration of over 60,000 g inside the barrel?

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I know why God made the rhinoceros, it's because He couldn't see the rhinoceros, so He made the rhinoceros to be able to see it. (Clarice Lispector)

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Alan Cresswell

Mad Scientist 先生
# 31

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10^6 m/s² (wise words at the bottom of that page, BTW), 100000g.

Which does present an alternative to lasers. A gun barrel long enough to sustain that acceleration for 1-2 minutes, with enough explosives to maintain the force pushing the "bullet" (aka nano-star ship). Point and fire.

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Don't cling to a mistake just because you spent a lot of time making it.

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