New Mars Forums

Yes, the Mars Bunny!  That gave us days of fun.  It was revealed to be a scrap of fabric from the balloon package.  More important, it gave us information about the wind on Mars - information the probe did not have instruments to collect.

No, I don't.  In fact, you're the very first person I've seen claiming that. 

Do you have a source you can recommend for this information?

Your astrological zodiac sign corellates with your risk of traffic accidents.

It's been replicated, so it must be true.   

Actually, being an Aries, I can appreciate this.  Over the years, I've run off the road, hit other cars - one in a parking lot... I even hit a house once.  Why, I was in a near collision just yesterday.  I never figured I was fulfilling some cosmic destiny.  I just thought my driving stank.   This makes me feel much better.   8)

I wasn't aware that there was a limit to the number of people you could put on a cycler.

I can’t (believably) downplay the difficulties inherent in asteroid mining, but I think you’re understating the relative problems of obtaining material from the lunar surface.  They are such that obtaining the same material from asteroids is at least a competitive proposition.

Your own “who cares if it consumes more fuel if the fuel is free?” argument could be applied to any trip you like - from Earth, from the moon, or from an asteroid - so long as fuel is available at the point of departure.  Getting to an asteroid in the first place need not require any more (or less) fuel than getting to the moon – it all depends on the target.  So, comparing outbound delta-v lends no obvious advantage to either method.  And, while the rockets required for either approach will be large (I’ve never seen a sounding rocket with a 19+ MT payload), the vehicles required to reach and mine an asteroid need be no larger than those needed to reach and mine the moon if you send both in the same quantity.   

So, yes, if you can write off the fact that large vehicles are needed for travel to/from the moon, then I can write off the fact that the same size vehicle will be needed for asteroid mining, too.

I also take issue with your assertion that we can’t move an asteroid. 

Oh, we can’t move Vesta, or even Eros.  But we could come home with something the size of 2002 AA29.

An asteroid of this size, with a minor diameter of less than 60 m and a mass of less than 250000 MT, would have a gravitational acceleration of around 0.000002g (utterly negligible).  A minor axis rotation period of less than 7 hours would completely negate this, and anything faster would tend to spin loose regolith off of the asteroid.  Lashing to the asteroid with a few hundred meters of spectra line is not an incomprehensible feat (and it can be done without ever needing any other means of latching on), and is all that is necessary to deploy a low thrust engine.   The hydrogen/oxygen rocket fuel needed to spin-up the asteroid is determined by the change in angular momentum required.  The fuel required is only 300 kg of H2/LOX to crank it up to a 7 hour period from a dead stop.  With 10MT fuel or more, you could spin the asteroid clean for prospecting.  With a few times more fuel, you could spin it apart and see what’s inside (which is what I recommend for anything larger, BTW).  An equally efficient use of the same fuel is to bring the asteroid’s spin to a near stop on all axes so that solar power can be employed.

19 MT of fuel – your suggested lunar supply payload – can eliminate the whole “spin BAD BAD!” objection for asteroids of 300m minor diameter or larger. 

Once 24:7 solar is available for months at a time, there’s no reason to remain limited to chemical rocketry for propulsion.  Unfortunately, electric rocket propulsion with exotic fuels will not do the trick, either – the fuel needed to bring 2002 AA29 to Earth in less than a year exceeds the GTOW of a Saturn V rocket at the asteroid surface, even using relatively efficient engines.  Not that this isn’t equal to the mass you proposed launching from the moon over one year with 250 times the potential payoff, but it does move beyond the “just write off the fuel” regime.  You can’t write off the fuel if the fuel is the only thing you’re hauling.

To effectively move the rock, a means must be found to use the asteroid material for fuel, just as you proposed using lunar material for fuel.

This is where one might care about asteroid volatiles.  However, that would require actually hauling refining equipment out to the asteroid, and assumes that the asteroid of interest is volatile rich – even if what you’re really after is nickel-iron.  There’s a better way.

Time for some vaporware.  :twisted:

The weight (gravitational force, not mass) of 1000 MT of asteroid material in the asteroid’s gravitational field is only 20N.  If you can get it free, it doesn’t take much to get it clear of the asteroid.  And that can be spun, too.  Using an electric motor with a reel of rope, you can get that 1000 MT mass whirling at 100 m/s – at stresses within the capability of spectra rope – and throw it off of the asteroid.  Releasing that sling at the right angle will impart new rotation and a rearward motion of 40 cm/s.  160 just like it – two thirds of the mass of the entire asteroid – will give you enough velocity to get the lonely remaining chunk of asteroid into earth orbit.  But each of those outbound chunks also has double the velocity needed to reach earth orbit.  If you send two even larger chunks at a time, themselves connected by a smaller sling capable of 100 m/s, one of the chunks can be thrown off to decelerate the other into earth orbit.  In this way, half the mass of the asteroid can be sent to earth orbit 1000 MT at a time, instead of just the last 1000.  If the part reaching earth is the part with the sling, a recovery crew can re-orbit it the same way by flinging off another chunk.

As for actually getting purchase on the asteroid in zero-g, if you’ve got the 10 MT of spectra rope necessary for the larger sling, you’ve got enough to wind it around 2002 AA29 approximately 130 times.  Just bola the thing and tie yourself on. 

The whole process can be accomplished with outbound payloads no greater than 19 MT.  I’d guess about three to five per year per 1000 MT payload per year.

The current theory is that any element available in a naturally occurring ore on earth can be obtained from a naturally occurring ore on Mars.  However, because of Mars's geological history, some ores will be rarer or more common than on Earth. 

Iron ore, for example, will be everywhere.  Mars clearly underwent banded iron formation just like Earth (all the iron in its oceans precipitated out in less than a hundred million years, forming an iron rich layer of rock), but wasn't buried very deeply.  The iron content of the surface dust is relatively low grade, but still useable if nothing better is available, and high grade iron ore was literally lying around all over the surface where the Opportunity rover landed.  In certain locations on Mars, practically all you need to mine iron is a broom.  Certain industrially valuable salts are also lying around for the taking. 

You will likely be more interested in the minerals expected to be rare.  The current theory is that as the first Martian lakes evaporated and got more and more concentrated, they became acidic.  They probably wouldn't have eaten your boots off, but you would not have wanted to wade barefoot in one.  All of that acid destroyed some minerals in the soil which are now rare on Mars. 

Clays are destroyed by strong acids, and clays are now found only in the mountains of Mars where they escaped submersion in the acidic lakes and souring soil of the lowlands.  Clays are an important component of arable soil, and it may be worthwhile to go into those mountains and mine clay for agriculture.

Carbonates, like lime, are destroyed even by the weak acids that find their way into acid rain.  They did not survive the acid age of Mars, not even in the mountains.  No spectroscopic observations have ever confirmed the presence of carbonate deposits on the surface of Mars.  And carbonates are even more fundamental to agriculture than clays.  Many essential plant nutrients are most readily absorbed as carbonates, and they are practically the only source of some nutrients in soil agriculture.  Even algal and hydroponic agriculture requires carbonates.  Carbonates are so vital to agriculture that if they can't be obtained locally then they will have to be manufactured.  A limestone mine (or factory) on Mars would be something worth having.

*bump*

There's a new method of thermoacoustic cooling being developed.  Check out the You-tube video of this water hammer heat pump.

It's not clear whether the thermal cycle involved is a Sterling Cycle or Malone Cycle acoustic analog, but what is clear is that heat is being transferred from the rotor body (and the reservoir/room it's in) to the exhaust.  The heat source is not friction.  This thermal cycle can be used for refrigeration as well as heating.

An equally important observation is that the use of liquid cavitation as a sound source is more efficient and produces far more acoustic power than piezo-electric sources.

I think it's got potential.

Technically, it's what Scientific American magazine describes, but yes, apparently I misread the article.  (It wasn't hard.  Darn Editors.  :? )A quick check with other sources reveals that, while McMurdo is having another outbreak this year, it is not nearly as bad as 2003.  However, my search did reveal another interesting phenomenon.

There's an outbreak recorded this year, 2006.  There was a major problem with an outbreak in 2003, and I found outbreaks recorded in 2000, 1997, and mention of a case in 1994.   

It might just be sampling error, but this is starting to look like a pattern.

Is this the "three year Crud?"

WTF?

Researchers have recently developed a multijunction photovoltaic cell with 40% efficiency.  That's double the efficiency of the best silicon solar cells, and about four times the average performance of silicon cells.  This is, of course, not the most efficient solar cell in existence, but it may soon be among the best currently available.  These cells are notable because they are relatively easy and practical to manufacture. 

The article in the link talks of only using these devices in concentrator arrays, but there's no physical limitation that would prevent them being used alone.  That's code for "so expensive that they're only cost competitive with a concentrator."  However, having a consistent manufacturing process can make them publicly available, and the increased price is unlikely to exceed the savings on interplanetary transportation for a smaller array.

This could become an important off-the shelf technology for space exploration.

To what intractable basic physics problems and show stopper details are you referring?

Good. 

I admit I wasn't expecting liquid water, but water vapor outgassing in the last decade was the only explanation I could ever come up with for the sharp, crisp gaps in this micro-imager photo from Purgatory Dune at Meridiani.  That left a high albedo deposit behind, too, but you'll notice there's no evidence of flow as in the MSSS images.  I fully expected our first water well on Mars would be a gas well or an ice mine.

Liquid water on Mars.  I love it when Mars proves me wrong.   8)