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Given enough power to run it, a modified Fusor could be operated just like any other ion drive, only with an exhaust velocity between 250km/s and 10000km/s, depending on design.

A useable rocket engine would likely need more power than the tabletop demonstration units, because its confinement time drops when you're draining the plasma out of a rocket nozzle.  However, the tabletop units typically only use 100W to 1000W -- less than a toaster.  (The charge developed is more important than the current.)

The closest thing the rovers have to a water detector is their thermal emission spectrometers.  Both lack the mass spectrometers necessary for definitive identification of water.  Neither the Mossbauer spectrometer nor the XRF spectrometer can detect water because neither molecular water, hydrogen, nor oxygen emit at frequencies these types of spectrometer are designed to detect.  In fact, one possible test the rovers can make for water using their limited equipment is to identify a candidate target using the thermal spectrometer and check it with the alpha XRF spectrometer.  If the XRF spectrometer gets significantly lower than expected counts, it's a safe bet that it's only reading traces of dust in a matrix of something it can't detect -- like ice.

I don't understand the necessity of a $100 cutoff (or $10, or $10000) for this argument.  Launch expense seems irrelevant...    ???

I’ve done a preliminary analysis of some of the soil sample micrographs, looking at size distribution patterns in the hematite blueberries at Eagle crater.  The following mosaic is a good  example of some soil micro-photos by the Opportunity rover:

http://marsrovers.jpl.nasa.gov/gallery. … ..._br.jpg

and this non-micrograph picture of the “Berry Bowl” site was interesting  as  well:

http://marsrovers.jpl.nasa.gov/gallery. … ..._br.jpg

It’s been noted that the size distribution of these hematite concretions is not uniform or balanced. There appears at first glance to be a distinct upper and lower limit to their size throughout the Eagle Crater site, with the average size of the globules being closer to the upper limit than the middle of the  range. 

I  find that there is indeed an upper limit to the size of the hematite blueberries, which is on the order of about 3mm but actually varies significantly from sample to sample.  The largest blueberries  exceed 5mm but those are quite rare.  The average is between 2.5mm and 3mm, despite the fact that the typical median value for soil samples is usually closer to 1.5mm.

There  is an observable lower limit in several of the samples, but not all.  Further, this lower limit is not consistent from sample to sample.  I attribute this to two effects: 1) resolution limits and other  artifacts in the images which make my sampling techniques unable to discern the smallest particles,  and 2) size separation of particles due to saltation in the soil samples.

This link is an article discussing size separation of particles in a collection of vibrated granules:

http://jfi.uchicago.edu/~jaeger....ure. … ...ure.pdf

Windblown granules can be expected to behave similarly as they are deposited during saltation, though over longer time periods.

The  graph at the beginning of the article indicates what would be necessary for large particles (like  the hematite blueberries) to separate vertically relative to the surrounding grains as the soil is blown along the surface.   This data suggests that the largest blueberries would rise to the top of a vertical column of windblown grains over time as they were carried along, with the smaller blueberries remaining buried, thus segregating them according to size and concentrating the larger blueberries on top.  It also suggests that the particle separation will be influenced by relative density.

How large this difference in density is may provide an additional clue to the composition of the little  spheres.  For example, if they are porous (and thus less dense), their distribution will vary slightly from that of solid hematite granules.

The separation of sizes during saltation should leave the largest particles on top.  The size distribution is fairly sharply limited to 5mm.  This suggests that something prevented the growth of  hematite blueberries larger than 5mm. However, particles in the surrounding (possibly non-hematite) grains which are of sufficient density to separate at the same rate as larger, less dense particles will mix in evenly with those particles, concealing the smaller hematite particles amid the rest of the dust.  This accounts for the observed lower size limit and its variability from sample to sample.

Given the assumption that relative separation periods for windblown separation are proportional to those for vibratory separation, it is possible to set limits on the density range of the hematite granules in these soil samples.

Assumptions about the surrounding grains are necessary for exact density figures, but not for estimating relative density.  For example, the average density of solid hematite is 5.3 g/cc, while the average granular  density of silica sand is 2.6 g/cc. Solid hematite grains are twice as dense as solid silica sand grains. So, according to the results in the attached article, the smallest grains of solid hematite we should see always on top of a windblown mix of silica sand and hematite are those whose size is at least 25 times that of the average sand grain. Anything smaller than that would be mixed in evenly with the rest.

If the surrounding granules were 10 times denser than the hematite blueberries, the smallest blueberries would be less than 5 times the average diameter of the surrounding grains.  Similarly, if the surrounding granules were also largely solid hematite (yielding a density ratio of 1), the smallest observed diameter should be at least 15 times the average diameter of the surrounding grains. 

The smaller the smallest hematite grains are, the lower their relative density is.

My estimate is that the smallest granules are about 10 to 15 times the size of the smallest grains, but this is likely inaccurate due to limits of image resolution (the smallest grains are likely smaller than my estimate, making the actual size ratio higher).  This suggests that the hematite blueberries are not significantly heavier than the smaller particles that comprise the rest of the windblown grains.  This finding is consistent with large, solid hematite granules atop a sand composed largely of hematite.  It would also be consistent with large, porous hematite granules atop a sand composed of lighter particles, such as silica grains.  However, the lower size limit observed does not support a density ratio less than 0.7 or greater than 1.3.

In short, the hematite blueberries are about as dense as the surrounding dust.

Thanks for your time.

CME

Uh Oh!  There seems to be a theme developing here.

My own wife has already told me that she would prefer to live on Earth.  Unfortunately, this was revealed _after_ the wedding! 

(Should have included it in the wedding vows.  Dang It!)

:bars3:

It may not bode at all.  Or it may be the greatest thing for space exploration since the telescope.  Hard to say until we know whether or not it can produce enough power to reach breakeven.

As an example, just producing nuclear fusion reactions without reaching breakeven is something that can be done with an existing technology called a Farnsworth Fusor.  It's a little tabletop-sized device invented by the fellow who invented television.  It ionizes gases using static electric fields and circulates them until they accelerate to speeds/temperatures where they will fuse.  I suspect a Farnsworth Fusor produces a higher rate of fusion than they're currently seeing for sonoluminescence. 

Sadly, it's still not enough to reach breakeven and produce more power than it takes to run the reactor.

Happily, it's fascinating that we already have tested, proven technology to create a fusion rocket engine today if we just drop this foolhardy preoccupation with wanting it to bootstrap its own power source.

How will nuclear fusion turn out as a technology?  Well, that depends as much on what you want from it as on what it can give you.

So, there needn't be any causality violation.

Third: Why does it have to be faster than light?  The whole messy problem could be avoided altogether if we were just willing to settle for sublight speeds.

Second: I've seen some interesting speculations that an absolute reference frame could exist.  Relativity allows for something of the sort with rotating objects, leaving the door open for the existance of an absolute reference frame (if certain violations of conservation of angular momentum are possible).  An absolute reference frame would allow FTL travel without causality violation.

First: In strictest terms, the speed of light was never proven, per se, to be the fastest speed in the universe.  This was simply assumed as a postulate in the derivation of Relativity, and all the predictions derived from that assumption have proven true so far.  So far, the supremacy of light in the fast lane is an inductive conclusion, not a deductive one.

A gas with a low enough ionization energy can be ionized with just an electric current.  This is how an arcjet rocket engine works.  The best fuels for an arcjet usually fall into two categories: heavy molecular weight gases with low first ionization energies (which take less power to ionize but more power to accelerate the plasma) and light molecular weight gases that dissociate into still lighter molecules (which take more power to ionize but less power to accelerate the plasma).  It is not necessary to completely ionize all of the gas to start manipulating it like a plasma, but the more you can ionize the faster the exhaust velocity can be.

A spark plug from a car, run at high enough voltage in a small nozzle, could ionize a gas.  However, if you want the best performance, it’s best to shape the nozzle for optimum performance.  One of the best nozzle shapes is simply two concentric pipes (one inside the other) with the propellant flowing between them.  Each pipe serves as a high voltage electrode, and the current arcing between the electrodes flows through the propellant, ionizing it.  The current sets up a magnetic field (perpendicular to both the gas flow and current flow, but concentric with respect to the pipes) that accelerates the plasma out of the nozzle at a rate even faster than its thermal expansion would allow.  In addition to creating a suitable magnetic field, it's also important to shape the nozzle to allow maximum charge accumulation where you want it (and prevent it where you don't).

"Twisting them like tornado winds"... If only!   

Actually, if antimatter power and spin drive ever become realities, and if we can ever manufacture our own miniature Hawking-style black holes (hmm... Did I forget any "ifs"? ), then we might someday be capable of producing enough power in a dense enough package to make a gravitational field do just that.  However, the entire planet Earth does not.  The sideways component of gravity in Earth orbit due to inertial frame dragging is infinitesimal.

SBird, I'll say again that I have no reason LIGO shouldn't work.  But saying it has to be done in space because of the noise here on Earth just puts another maximum limit on the effect.  There's still an absence of evidence.

If LIGO doesn't work, it would be safe to start asking where all that neutron star energy is really going.

An excellent idea!

The Beagle probe did not reach Mars in operational condition, but satellite photos of the landing site indicate that it did not disintegrate, either.  Its components could conceivably be reclaimed at a later date.  Likewise, if automated precursors to a Mars Mission (like an ERV or probe) fail upon reaching Mars, all the equipment isn't necessarily lost.

I'm embarassed to admit I only heard of Gravity Probe B this morning, so I'm no expert...   

However, I can guess how it's supposed to work.  The component of gravity due to inertial frame dragging is in the same direction as the Earth's rotation.  The probe is in a polar orbit, which means that once per orbit it's travelling north relative to the earth and once per orbit it's travelling south relative to the earth.  So, when it's travelling north, the inertial frame dragging should appear to be in one direction, and when it's travelling south the inertial frame dragging should appear to be in the other direction.  So, the probe will be looking for some miniscule variation with a direction that  flip-flops once every orbit.  People have seen what they believe to be inertial frame dragging in celestial mechanics, and the general consensus is that the evidence so far is pretty solid, but that flip-flop effect is the one thing you can't get just watching Mercury's orbital precession.

Well, that's how I'd do it if I had a Gravity Probe...   :;):

The outcome of this experiment could be important to Humanity's future as a spacefaring species.  If inertial frame dragging as described by Einstein is real, it means that spacetime can conceivably be manipulated arbitrarily using energy in forms that we can control.  If inertial frame dragging is possible, so is warp drive.  It's just a matter of degree and density.

It's important to note that a one-way colonization mission will not necessarily reduce costs.  If anything, a one-way mission will cost more than a return mission because of all the extra equipment (and corresponding R&D) that will go into keeping their colony running successfully once they get to Mars.

A colonization mission is only guaranteed to give more return for the money, not to cost less money.

Josh,

I believe that a dedicated amateur can do exactly the type of project you're describing.  Don't give up.  Just start small, and work with expansion in mind.