Author Topic: Why the VASIMR hype?  (Read 216353 times)

Offline yinzer

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Re: Why the VASIMR hype?
« Reply #300 on: 10/06/2009 06:50 pm »
People laughed at Einstein.  People laughed at Galileo.  But people also laughed at Bozo the Clown.

When the VASIMR guys come up with something that actually produces thrust, let me know.  Hasn't Chang-Diaz been at this since the 70s?

I don't recall anyone laughing at Einstein, when he published his three papers. I do recall a Nobel Prize. No one laughed at Galileo either. I think the big problem was the risk of being burned at the stake like Bruno. And people paid good money to laugh at Bozo the Clown (who thus laughed all the way to the bank). VASIMR gets to pass the same test as everything else. In the end, it has to work. To that end, I guess we'll see what happens when/if it gets lugged up to ISS and tested.

The Nobel Prize came after Einstein was shown to be correct, not the instant he published his papers.

As far as I know, the VASIMR guys have yet to demonstrate actual thrust, even with a subscale model.  I would be happy to be corrected.
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Offline Danny Dot

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Re: Why the VASIMR hype?
« Reply #301 on: 10/06/2009 08:03 pm »
People laughed at Einstein.  People laughed at Galileo.  But people also laughed at Bozo the Clown.

When the VASIMR guys come up with something that actually produces thrust, let me know.  Hasn't Chang-Diaz been at this since the 70s?

I don't recall anyone laughing at Einstein, when he published his three papers. I do recall a Nobel Prize. No one laughed at Galileo either. I think the big problem was the risk of being burned at the stake like Bruno. And people paid good money to laugh at Bozo the Clown (who thus laughed all the way to the bank). VASIMR gets to pass the same test as everything else. In the end, it has to work. To that end, I guess we'll see what happens when/if it gets lugged up to ISS and tested.

The Nobel Prize came after Einstein was shown to be correct, not the instant he published his papers.

As far as I know, the VASIMR guys have yet to demonstrate actual thrust, even with a subscale model.  I would be happy to be corrected.

Lets see, all he did was derive the well known Leblintz transformations, derived that the speed of light was indeed constant, then derived e=m*c^2 -- all using straight forward calculus directly from Maxwell's equations.  Then the photo electric effect to quantify this well know effect using the brand new Planks constant, not to mention the third paper on microscopic vibrations of an atom to quantify this effect.

My history book tells me he created quite the fuss in the world of theoretical physics when all 3 hit the street at the same time in 1905 -- and from a stinking patents clerk no doubt.

I think you are referring to the 1919 measurement of gravitational lensing that confirmed the General Theory that he published in 1915 -- well after he was one of the most famous men in history for his 1905 mega hits that changed the world forever.

Do you even know what he got the Nobel Prize for?  Hint: it was not for relativity.

Danny Deger
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Offline alexterrell

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Re: Why the VASIMR hype?
« Reply #302 on: 10/06/2009 08:37 pm »
snip

If VASIMR were aimed at easier traditional EP applications, then you don't need such high accelerations, and solar is fine. Why not design a VASIMR to take, say, 200-500 tons of cargo from LEO to Mars Orbit, over the course of 18 months, using near term solar power, instead of relying on someone else to make an expensive breakthrough in nuclear power?

What is EP?  And a 18 month cargo mission with a much smaller power requirement might be an excellent application for VASIMR.  This might make solar viable.  If you want the total delta of V of the planned 3 month manned mission, dig around and I bet you can find an email address for Ad-astra and someone would be glad to give you this number.

Putting a uranium reactor in orbit is not high tech or high risk technically.  Someone needs to teach the world a cold 235 reactor is less hazardous than the hypergolic fuels we use all the time in satellites. 

Danny Deger
I found this:

Page 4/12 has delta-Vs for Opposition and Conjunction class missions.
http://www.lpi.usra.edu/publications/reports/CB-955/drake.pdf

There is a serious increase in delta V if you want to go fast. Though it looks like around 2020 there an opposition mission might be feasible (Can NASA do first, short stay mission to Phobos around this time?)

I think rather than reducing the journey time, use the capabilities of VASIMR to either increase the mission mass, or take cargo separately. That means reduced acceleration but lower mass because solar can be used.

And on the theme of quick hits for VASIMR, after ISS reboost, they should go for a solar powered tug, with about 2.5MW (a bigger engine or 12 VASIMR 200s?). This could have a dry mass of about 12.5 tons, and with about 12.5 tons of fuel could take 100 tons from LEO to EM-L1 per year (in either one or two trips).

This is a useful paper http://www.scribd.com/doc/18689863/Solar-Electric-Tug proposing a 400-700KW Hall Effect thruster to do the same. VASIMR needs more power but can use less fuel.

Offline yinzer

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Re: Why the VASIMR hype?
« Reply #303 on: 10/06/2009 08:51 pm »
He got the Nobel Prize for the work on the photoelectric effect and the quantization of light.  In 1921, 16 years after he published his first revolutionary papers.

Perhaps people didn't laugh at Einstein.  But they thought he was wrong, about the quantization of light and about special relativity.

Someone thinking you're wrong doesn't make you right.

Ad Astra doesn't have a thruster, even a breadboard one.  They have a fairly powerful plasma heater, some pretty pictures and math about how you might be able to build a thruster using said power heater, and an incredible PR machine.  But no thruster.

I'm not sure why they've spent the last ten years building bigger plasma heaters instead of an actual thruster; perhaps someone with more insight could chime in.
« Last Edit: 10/06/2009 09:47 pm by yinzer »
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Re: Why the VASIMR hype?
« Reply #304 on: 10/06/2009 10:35 pm »
He got the Nobel Prize for the work on the photoelectric effect and the quantization of light.  In 1921, 16 years after he published his first revolutionary papers.

Perhaps people didn't laugh at Einstein.  But they thought he was wrong, about the quantization of light and about special relativity.

Someone thinking you're wrong doesn't make you right.

Ad Astra doesn't have a thruster, even a breadboard one.  They have a fairly powerful plasma heater, some pretty pictures and math about how you might be able to build a thruster using said power heater, and an incredible PR machine.  But no thruster.

I'm not sure why they've spent the last ten years building bigger plasma heaters instead of an actual thruster; perhaps someone with more insight could chime in.

Huh? It is an actual plasma thruster, just not in space! (And charged particles are only "stuck to magnetic field lines" on a large scale where the magnetic field is constant, like the solar corona. If they were stuck even on small scales, then synchrotrons wouldn't work, would they? Yup, all those charged particles would be stuck in the magnetic fields!) I guess most of the reason they haven't flown smaller demonstration thrusters is that there is a minimum size needed for the refrigeration requirements of the superconducting magnets. Hall thrusters and other ion thrusters have much, much smaller minimum sizes.
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Offline yinzer

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Re: Why the VASIMR hype?
« Reply #305 on: 10/06/2009 10:46 pm »
He got the Nobel Prize for the work on the photoelectric effect and the quantization of light.  In 1921, 16 years after he published his first revolutionary papers.

Perhaps people didn't laugh at Einstein.  But they thought he was wrong, about the quantization of light and about special relativity.

Someone thinking you're wrong doesn't make you right.

Ad Astra doesn't have a thruster, even a breadboard one.  They have a fairly powerful plasma heater, some pretty pictures and math about how you might be able to build a thruster using said power heater, and an incredible PR machine.  But no thruster.

I'm not sure why they've spent the last ten years building bigger plasma heaters instead of an actual thruster; perhaps someone with more insight could chime in.

Huh? It is an actual plasma thruster, just not in space! (And charged particles are only "stuck to magnetic field lines" on a large scale where the magnetic field is constant, like the solar corona. If they were stuck even on small scales, then synchrotrons wouldn't work, would they? Yup, all those charged particles would be stuck in the magnetic fields!) I guess most of the reason they haven't flown smaller demonstration thrusters is that there is a minimum size needed for the refrigeration requirements of the superconducting magnets. Hall thrusters and other ion thrusters have much, much smaller minimum sizes.

They have not demonstrated the magnetic nozzle, nor have they actually measured thrust - a force exerted by the device.  They have theories about how the plasma will detach, but only theories.  Plasma dynamics are complicated and poorly understood enough that the lack of a test should raise real doubts.

At one point they had a notion to test a 10-kW or so thruster on a free-flying satellite, but nothing came of it.

This is not an issue of "can they scale their drive up to the numbers they are throwing around" but an issue of "does their thruster work the way they think it does".  The answer at this time is "no one knows".
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Re: Why the VASIMR hype?
« Reply #306 on: 10/06/2009 10:51 pm »
Really? It's not THAT complicated. I understand your skepticism, but in this case, the physics of their thruster is completely sound. If it is better than other designs yet to be seen, but it will certainly work.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline yinzer

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Re: Why the VASIMR hype?
« Reply #307 on: 10/06/2009 11:32 pm »
My understanding is that the physics and especially the engineering of their magnetic nozzle are still not completely solid.  It certainly has not been demonstrated.
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Re: Why the VASIMR hype?
« Reply #308 on: 10/07/2009 02:01 am »
So that lever the engine pushes back is free floating without telemetry?
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Offline yinzer

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Re: Why the VASIMR hype?
« Reply #309 on: 10/07/2009 02:42 am »
From an older document on NASA's website
Quote
However, while experiments proceed, a
major physics objective continues to be the
demonstration of plasma/field detachment after
expansion in the magnetic nozzle.

They have done tests where they put a probe in the plasma flow before it detaches and measure the force exerted on the probe, but that's not the same thing as the thrust that an actual VASIMR would provide.
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Re: Why the VASIMR hype?
« Reply #310 on: 10/07/2009 03:20 am »
So it's not a simple matter of including sensors in the engine mountings?
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Offline yinzer

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Re: Why the VASIMR hype?
« Reply #311 on: 10/07/2009 03:41 am »
No, you could include sensors in the engine mountings.  That's the traditional way to do it.

But the VASIMR people don't have an engine yet, and their magnetic nozzle needs a really big vacuum chamber to realistically test.  Hence their current hopes to do in-space testing.
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Offline Danny Dot

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Re: Why the VASIMR hype?
« Reply #312 on: 10/07/2009 03:51 am »
Someone needs to teach the world a cold 235 reactor is less hazardous than the hypergolic fuels we use all the time in satellites."


That isn't true

Jim:

Are you referring to the very thermally hot RTGs and their Pu-238 fuel or a cold, never-used U-235 fueled power reactor?  There is a big difference between the two. 

Danny:

Cleaning up a cold and intact U-235 reactor after an accident is no big deal.  Cleaning up a hot U-235 NERVA reactor being used as the first stage of a rocket was examined by intentionally redlining and blowing up a NERVA engine at Jackass Flats, NV, back in the 1960s.  This was described in James Dewar's two books on the NERVA program entitled “To the End of the Solar System” and “The Nuclear Rocket”.  Just go to Amazon book section and type in Dewar’s name.  Bottom line was that the NV clean-up crew waited about three weeks for the really radioactively hot core materials pieces to abate their radiation outputs, then they moved in donned in their bunny suit PPE and had the test stand ready to go again in a couple of weeks.  Using KSC for a cold U-235 launch should be safer than supporting an RTG powered payload.  However, for a first stage NERVA launcher I’d move these operations to a Pacific Ocean island until enough operational experience is obtained.

http://www.amazon.com/End-Solar-System-Nuclear-Rocket/dp/189495968X/ref=pd_sim_b_1


Somebody actually blew up a hot uranium reactor on purpose just to prove the clean up would be nasty  >:(

He could have just used a gigger counter on one that was just shut down for a bit.   What kept the darn thing from melting down.  No wonder the public doesn't trust the US Government with nuclear powerplants.  If they go around blowing them up without a containment vessel just to prove it is not a good thing to do while airborne, we need to go back to gas fired lamps or something.   I change my mind on nuclear power if this is the best we can do to not kill our selves with this technology.

Ain't no way we can ever launch live reactors through the atmosphere.  At some point a launch failure creates a nuclear waste land some place populated.  The impact point is going to go to go to some place not nice as the launch vehicle achieves orbit.  Firm no-go and always will be in my book.  Again we shouldn't be trusted with lunching a cold reactor if at some point we thought of launching a hot one for more than 2 seconds.

It is one thing to put an intact hot reactor on the ocean floor when a sub fails for any reason, it is quite something else to put one at the base of the Eiffel Tower during a launch failure.

Danny Deger
« Last Edit: 10/07/2009 03:54 am by Danny Dot »
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Online Robotbeat

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Re: Why the VASIMR hype?
« Reply #313 on: 10/07/2009 04:12 am »
I think they were trying to prove that it WASN'T that big of a deal to clean up. Nowadays, the anti-nuke crowd makes it seem like it would always take "infinite" resources to clean something like that up (which it would after their endless, frivolous lawsuits).
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Offline mlorrey

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Re: Why the VASIMR hype?
« Reply #314 on: 10/07/2009 04:18 am »
My understanding is that the physics and especially the engineering of their magnetic nozzle are still not completely solid.  It certainly has not been demonstrated.

Like your other statements here, you are just showing your ignorance. You saw that video posted by the other fellows here? See how the plasma has a diverging spread to it? That is because it is following the magnetic field lines of the  nozzle on exit, like an electromagnetic de laval constriction.
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Offline Danny Dot

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Re: Why the VASIMR hype?
« Reply #315 on: 10/07/2009 04:22 am »
I think they were trying to prove that it WASN'T that big of a deal to clean up. Nowadays, the anti-nuke crowd makes it seem like it would always take "infinite" resources to clean something like that up (which it would after their endless, frivolous lawsuits).

Having to wait three weeks to approach it should not have been a surprise.  We knew enough to not have to have done the test.  What type of isotope and what its half life is was well understood before the first reactor was built.

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Offline Star-Drive

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Re: Why the VASIMR hype?
« Reply #316 on: 10/07/2009 04:59 am »
I think they were trying to prove that it WASN'T that big of a deal to clean up. Nowadays, the anti-nuke crowd makes it seem like it would always take "infinite" resources to clean something like that up (which it would after their endless, frivolous lawsuits).

Having to wait three weeks to approach it should not have been a surprise.  We knew enough to not have to have done the test.  What type of isotope and what its half life is was well understood before the first reactor was built.

Danny Deger

Danny:

Here is a picture of the KIWI test and the reason for it.

"This KIWI-B type reactor was deliberately destroyed on January 1965 by subjecting it to a fast excursion.  This test was intended to confirm theoretical models of transient behavior."

And really, you've been drinking the anti-nuke coolaid yourself.  Ionizing radiation and its isotopes can be hazardous to your health in large doses just like getting across a 12kV power line can be terminal to your health, but it's not near as detrimental as the zero radiation tolerance school would lead you to believe.  Have you had your minimum daily allowance of ionizing radiation today?  It's been demonstrated in study after study that low daily doses of gamma and X-rays improves your immune system's responses to all affronts.  Something like 5-to-20 REM a year ought to do...
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Offline alexterrell

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Re: Why the VASIMR hype?
« Reply #317 on: 10/07/2009 07:43 am »
The question on clean up comes down to this. If you have Uranium, enriched to say 20% U235, scattered across the floor of the Atlantic, do you have to retrieve the pieces?

How many Soviet nuclear subs are down there?

Offline PlanetStorm

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Re: Why the VASIMR hype?
« Reply #318 on: 10/07/2009 10:17 am »
My understanding is that the physics and especially the engineering of their magnetic nozzle are still not completely solid.  It certainly has not been demonstrated.

Like your other statements here, you are just showing your ignorance. You saw that video posted by the other fellows here? See how the plasma has a diverging spread to it? That is because it is following the magnetic field lines of the  nozzle on exit, like an electromagnetic de laval constriction.


You just made his point for him. The magnetic field lines are closed loops, hence the plasma doesn't detach, hence no net thrust. I believe that the thing that remains to be demonstrated is that there is magnetic reconnection, so that a bundle of plasma and magnetic field (and hence a bunch of momentum) disconnect and flow away downstream, imparting net momentum to the rocket.

edited for clarity
« Last Edit: 10/07/2009 10:19 am by PlanetStorm »

Offline PlanetStorm

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Re: Why the VASIMR hype?
« Reply #319 on: 10/07/2009 10:27 am »
The question on clean up comes down to this. If you have Uranium, enriched to say 20% U235, scattered across the floor of the Atlantic, do you have to retrieve the pieces?

How many Soviet nuclear subs are down there?

That's not what the question comes down to. It's the fine dust blowing around in the atmosphere that is going to lead to lawsuits, not the stuff buried under hundreds of metres of excellent radiation shielding.

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