NewSpace 2010: Polywell and Vasimr

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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GIThruster
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Postby GIThruster » Wed Jul 28, 2010 5:17 pm

If I understand Wiz's complaint about perturbation, what he's saying is that inertia is an intrinsic property of matter. I don't think Woodward nor March deal directly with that objection to Mach's work. For that IIRC, the paper "General Relativity as a Perfectly Machian Theory" by J. B. Barbour, in the collection above; was a good one, as was "Selected Passages on Machian Ideas" by Einstein--also in the collection.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

Roger
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Postby Roger » Wed Jul 28, 2010 5:56 pm

Why on earth would anyone want to loft 30k miles of elevator? It seems far more reasonable to lower the ribbon from 30k miles in orbit. Use a QED system placed on an asteroid with the propeer content, power into earth orbit. Power the manufacturing with polywell and lower the elevator.

Proly be over mars before anyone tries it over earth, too.

And drop the paper thin premise. Kim Stanley Robinson will laffin @ that big time.
I like the p-B11 resonance peak at 50 KV acceleration. In2 years we'll know.

WizWom
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Postby WizWom » Wed Jul 28, 2010 9:01 pm

GIThruster wrote:BTW Wiz, I'm not the one confused about the obvious connection between gravity and inertia. How do we simulate gravity? We spin. We generate inertia and the results are the same as a gravity field, mass suddenly has weight. That's because gravity and inertia are different outcomes of the same thing: gravinertial force (which is what makes possible the Gravinertial or "GI" Thruster.)


Um... the force felt in a centrifuge is not inertia, but acceleration. You so clearly want your explanation to be the case that I doubt any rational explanation can dissuade you from your belief.
Wandering Kernel of Happiness

Betruger
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Postby Betruger » Wed Jul 28, 2010 9:18 pm

WizWom, the ME conjecture is in those papers. Check it out and see.

TallDave
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Postby TallDave » Wed Jul 28, 2010 10:10 pm

icarus wrote:
With the elevator, you only provide a modest amount of potential energy; the vast remainder is taken from the Earth's angular momentum.


I see an environmental flaw here, who asked Gaia if you could take some of her angular momentum and what do you intend to do about paying it back?


Oh great, Global Slowing, another project for Al Gore to tackle in between demanding massage therapists renormalize his hockey stick.

GT -- There's a good summary of problems here, such as wind:

http://en.wikipedia.org/wiki/Space_elevator_safety

In the atmosphere, the risk factors of wind and lightning come into play. The basic mitigation is location. As long as the tether's anchor remains within two degrees of the equator, it will remain in the quiet zone between the Earth's Hadley cells, where there is relatively little violent weather.[citation needed] Remaining storms could be avoided by moving a floating anchor platform. The lightning risk can be minimized by using a nonconductive fiber with a water-resistant coating to help prevent a conductive buildup from forming. The wind risk can be minimized by use of a fiber with a small cross-sectional area that can rotate with the wind to reduce resistance.


As to why the concept has legs despite the quite possibly insurmountable challenges...

With a space elevator, materials might be sent into orbit at a fraction of the current cost. As of 2000, conventional rocket designs cost about $11,000 per pound ($25,000 per kilogram) for transfer to geostationary orbit.[55] Current proposals envision payload prices starting as low as $100 per pound ($220 per kilogram


http://en.wikipedia.org/wiki/Space_elevator

At those prices, we can seriously contemplate colonization.
n*kBolt*Te = B**2/(2*mu0) and B^.25 loss scaling? Or not so much? Hopefully we'll know soon...

GIThruster
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Postby GIThruster » Wed Jul 28, 2010 11:11 pm

WizWom wrote:
GIThruster wrote:BTW Wiz, I'm not the one confused about the obvious connection between gravity and inertia. How do we simulate gravity? We spin. We generate inertia and the results are the same as a gravity field, mass suddenly has weight. That's because gravity and inertia are different outcomes of the same thing: gravinertial force (which is what makes possible the Gravinertial or "GI" Thruster.)


Um... the force felt in a centrifuge is not inertia, but acceleration. You so clearly want your explanation to be the case that I doubt any rational explanation can dissuade you from your belief.


Wiz, obviously you need a primer. Wiki is not particularly good, but it is not especially bad either:

http://en.wikipedia.org/wiki/Mach's_principle

except that it makes mention of Godel's rotating universe and anyone who has considered these things carefully knows this is a red herring, since a closed universe cannot rotate.

Simplest point to our issue is that, Mach did not add complication to a simple issue, by saying inertia comes from gravity. He answered a long standing question that had eluded Einstein himself, though precursors to the answer can be found in Berkeley and Friedlander. None of these people were concerned with propellantless propulsion. They were considering the issue of inertia. If you just accept that inertia is an intrinsic property of matter, you don't even begin to ask the really deep questions that led to Mach's Principle and Einstein's General Relativity.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

zapkitty
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Postby zapkitty » Wed Jul 28, 2010 11:54 pm

TallDave wrote:As to why the concept has legs despite the quite possibly insurmountable challenges...

With a space elevator, materials might be sent into orbit at a fraction of the current cost. As of 2000, conventional rocket designs cost about $11,000 per pound ($25,000 per kilogram) for transfer to geostationary orbit.[55] Current proposals envision payload prices starting as low as $100 per pound ($220 per kilogram


http://en.wikipedia.org/wiki/Space_elevator

At those prices, we can seriously contemplate colonization.


But that's $6.6 million dollars for 30 tons to GEO... and while I balk at the concept of atmosphere-fueled SSTA torchships taking flight from backyards nationwide a week after EMC2 declares net power :)... there would seem to be a high probability that an established and operational polywell-powered fusion SSTO fleet making regular launches could easily beat that price... and provide much greater flexibility to the customers by providing much faster transport to orbit while avoiding the inevitable beanstalk choke points.

One clue to the future... there's a big difference in current LV prices and cargo capacity for launches to LEO and launches to GEO. This is necessitated by the substantial amount of extra propellant required for GEO over LEO... an amount that is a large part of the gross pay,oad of the LV and a sizable fraction of the vehicle gross liftoff weight.

A fusion LV (FLV) would not need that gross differential in propellant... as all FLV plans that I'm aware of involve the ship using high efficiency drives that a chemically-powered LV simply can't afford to loft.

Thus the price difference for an FLV delivery to GEO will not be 4 times the price to LEO for 3/4's of the cargo... as is currently the case with chemical LVs.

And so I think that beating $6.6 million for 30 tons to LEO (and a bit less tonnage to GEO) should be easy for FLVs.... and much more convenient for the customers...

edits: trimmed quotes, fixed typos...

Tom Ligon
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Postby Tom Ligon » Thu Jul 29, 2010 12:19 am

Regarding a space elevator going in on Mars before Earth, a couple of years back I ran the numbers on Saturn's moon Phoebe, and concluded you could make a nice space elevator for that body using rope from a hardware store, and climb it hand over hand. Long climb, but the forces are quite modest.

I expect this would work quite nicely for larger asteroids with a decent rotation. For little ones you just jump hard.

pfrit
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Postby pfrit » Thu Jul 29, 2010 2:23 am

Tom Ligon wrote:Regarding a space elevator going in on Mars before Earth, a couple of years back I ran the numbers on Saturn's moon Phoebe, and concluded you could make a nice space elevator for that body using rope from a hardware store, and climb it hand over hand. Long climb, but the forces are quite modest.

I expect this would work quite nicely for larger asteroids with a decent rotation. For little ones you just jump hard.


I doubt a nylon rope would work, but you do have a point. If I remember correctly, an elevator on the moon could be made from steel. If we do end up making elevators, the moon would be the logical place to build the first one. You could build it from materials on the moon, you do not require exotic materials (though they would be nice), you could lift the completed tether cheaply and you could make it much longer than actually needed without risk to use it as a sling shot for missions to other planetary objects. The only problem is that there are no people or factories on the moon.
What is the difference between ignorance and apathy? I don't know and I don't care.

icarus
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Postby icarus » Thu Jul 29, 2010 2:30 am

githruster: more red herrings for you, sir.

anyone who has considered these things carefully .... since a closed universe cannot rotate.


You haven't thought carefully enough it seems, 'rotate' relative to what exactly? E.g, a closed toroidal flow has ubiquitous rotation of the particles about the ring axis but may have no net rotation to the outside observer (although it can have that as well).

Consider that in GR, an expanding universe can interpreted as equivalent to a ubiquitous rotation of the universe in the space-time plane. Hubble's constant is then like a rotation rate, it sets the tick of the universal clock. Godel's solution is mathematically still an option.
Last edited by icarus on Thu Jul 29, 2010 10:48 am, edited 2 times in total.

GIThruster
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Postby GIThruster » Thu Jul 29, 2010 3:14 am

icarus, glad you have an interest!

Let me heartily recommend the anthology above, and especially the paper entitled "A Closed Universe Cannot Rotate" by D. H. King. Who knows, you might even find the paper on the web.

Just as you wonder, "relative to what exactly?"

That's an insightful question and one you'll be glad to glean the thoughts of King on.

From pails of water to galaxies colliding, this is fun stuff!

Just to tease, if inertia is intrinsic to mass, then a closed universe that rotates will generate centrifugal force on its parts. If inertia is not intrinsic but rather relates to gravity "outside", then a closed universe cannot rotate.

In short, a closed universe cannot rotate, and Mach is correct.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

TallDave
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Postby TallDave » Thu Jul 29, 2010 4:07 pm

But that's $6.6 million dollars for 30 tons to GEO... and while I balk at the concept of atmosphere-fueled SSTA torchships taking flight from backyards nationwide a week after EMC2 declares net power ... there would seem to be a high probability that an established and operational polywell-powered fusion SSTO fleet making regular launches could easily beat that price... and provide much greater flexibility to the customers by providing much faster transport to orbit while avoiding the inevitable beanstalk choke points.


Yes, if PW works out a SE is a lot less compelling. But there are considerable challenges in both paths, enough that I wouldn't want to rule one out based on the other at this point.
n*kBolt*Te = B**2/(2*mu0) and B^.25 loss scaling? Or not so much? Hopefully we'll know soon...

AcesHigh
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Postby AcesHigh » Sat Jul 31, 2010 5:02 am

GIThruster wrote:We don't need these thoughtless, useless, dopey solutions from sci-fi. We need solutions that are safe, quick, convenient and economical. We need propellantless propusion and as long as dread, dopey engineers hang out for less, we won't see funding for what's real--the M-E thruster.


in other words, you dont want solutions from "near future" sci-fi, you want solutions from FAR FUTURE sci-fi...

because it would be just weird if you were bashing sci-fi solutions AND defending propellantless thrusters and warp drives (or wormholes?) in the same sentence!

AcesHigh
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Postby AcesHigh » Sat Jul 31, 2010 5:09 am

Betruger wrote:I don't think you can bet on such a skeptic paying a hundred bucks to supposedly read something that defies everything he knows. There's lots of free resources e.g. all the papers and powerpoints and articles for free on the net, that e.g. Paul March has linked to.

e.g.
STAIF-2007 MLT Powered Spacecraft
From this page with more resources to choose from.


who is talking about sketptics here? GIThruster just proved to be a skeptic about space elevators and lightcraft. He tells the guy to read about ME-Effect, but it seems some people here havent read enough about space elevators...

GIThruster
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Postby GIThruster » Sat Jul 31, 2010 6:10 am

I'm not a skeptic. I'm a realist.

Elevators, Solar Sat Power Stations, Lightcraft, Rail Guns shooting stuff to orbit--don't make sense because they cannot be economically viable.

If you need to spend a trillion dollars for a space transport system, then you're never going to have such a system.

It's time aerospace engineers get on board with what is practical. Crazed solutions that require multi-hundred billion dollar investments are NEVER going to happen.

NOT a skeptic! Just a realist. Bogus transport notions need to go the way of the goonybird so that funds can be made available for the real work in propellantless propulsion.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis


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