New Mars Forums

I really don't give a flip if Sara Goudarzi didn't do her homework.  She's not the one who flew.

Congratulations, Anousheh Ansari, and welcome back.  I can't wait to get the print.  May you have many happy returns.

Stella, I hope you're next, complete with pop-art portrait.

Sounds like a good idea.  The name of any examples in the national government of either nation currently eludes me, though.

Where's the fun in that? :?

The curmudgeon is right!  All hail the power of the curmudgeon!

Aerovator will not work as advertised.

It is relatively simple to derive that there is some minimum tip velocity at which the fully deployed system is stable.  From there, one can then use that formula to find that there is some minimum altitude at which the tip's kinetic energy plus its potential energy is greater than the kinetic energy of a circular orbit.  This is the "working aerovator" regime of parameters, and cjchandler is right: it really exists.  There is an entire range of deployed configurations that are stable and can suspend a vehicle on its way to orbit.  Further, the drive situation for the fully deployed aerovator is more favorable than the "catherine wheel" plan shown in the cited Wikipedia article.  The only inflection in the curve of the tether occurs at its pivot.  (The picture in the article, with two inflections on each arm of a working aerovator, is physically impossible even if the aerovator can generate lift.)  So, it won't spiral, and the tension should be sufficient to turn it using a central motor.  The spin rate is only a few dozen rpm when fully deployed, so the fully deployed tether won't exceed the speed of sound until it's well clear of the lower atmosphere.

The trouble is that it can't be deployed.

The tip speed is smaller for shorter tethers.  However, it's impossible to reel it in to the Earth's surface because the minimum tip speed doesn't decrease fast enough as the tether is reeled in to keep the tip speed below Mach 6 in the lower troposphere.  I can't see it surviving that at <10 km elevation.  Also, the additional drag of supersonic travel without the compensating tension of the fully deployed tether will cause the tether to start winding around its driver once the reduced line tension falls below the aerodynamic drag (which it will at some elevation less than 10km without a HUGE end weight to keep up the tension - and it could still disintegrate at > Mach 6 anyway). 

If there's no way to reel it in, there's no way to real it out, either.  Using the catherine wheel configuration won't eliminate the problem - it will just change the winding points.

Now, it is theoretically possible to lower the aerovator into place.  Fully deployed, it's lower reaches never exceed the speed of sound due to the reduced angular velocity requirements.  However, any rocketry capable of doing this already exceeds the capabilities of the aerovator it's hauling.  (By its nature, the aerovator can only lift a fraction of its total mass into orbit.)  And any linear space tether capable of doing the job is already performing more efficiently.  Balloon deployment can't provide the necessary torque for a central driver and the fuel requirements for a catherine wheel driver are prohibitive at best without a steady source.

An aerovator is only superior to other launch technologies if it can be deployed from the surface.  It's useless for Earth.

However, not everywhere in the solar system is Earth.  Hmm...  I wonder where we could put it without those pesky tropospheric air densities?

Watch, nothing!  Get out your calculator, pencil and paper.  It's time to crunch numbers.

I want to know if this thing could work.

Oh my. 

Not only was Errorist correct in principle, but it's possible there may be no water ice on the moon after all. 

What's next?   :?

Believe it or not, this is a reasonable suggestion. 

Nuclear weapons leave isotopic signatures, and we have enough information about the uranium/plutonium sources used by various countries to be able to identify some of them.  After a nuclear strike, dirty bomb or thermonuclear (provided it was insufficient to destroy our capability to do so), there's a fair chance that we'd be able to identify the supplier of the original nuclear material. 

North Korea is making its own plutonium, which will have distinct isotope ratios determined by their enrichment process.  If we could verify those ratios in the residue after a nuclear attack, it would be reasonable to assume the North Koreans were just as responsible as those who perpetrated the attack, whether they deployed the bomb or not.

Say, isn't Epsilon Eridani a star with a dust disk observable at infrared wavelengths?  I wonder how a gas giant fits the current models for such disks.

Hmm...

Does this mean that moslems are now supposed to be as uncharitable as atheists?  Darn...  I have so much trouble keeping up with new stereotypes.  Do you mind if I just take your word for it?

As for the idea of a "jihad" being more of a spiritual quest than a call to run out and kill people, that's actually how most modern moslems use the term.  ("Crusade" has a similar history and modern usage.)  Islamic extremists are relatively unique among modern moslems in how narrowly they define jihad.  However, there is a precedent for this in the history of their religion which predates their radical reformation movements of the 18th, 19th and 20th centuries (Wihabi, etc.).  Back at the time of the Crusades, Islam was rather violently introduced to another religious institution, Christendom, which had not only throroughly incorporated this same idea of holy war but had its own armies.  Christendom was a united entity then in the same way that Islamist nationalists and other extremists are calling for today.  It was an aggressive major power, willing and able to force itself upon innocent people for no other reason than that it was entitled, taking both what was God's and what was Ceasar's.  And it remained that way for several hundred years.

During those centuries, christians were the scourge of the world.

This is what radical islamists so desperately want to become: the new "Christendom".  They want our submission - not to God, but to them.  Jihad has ceased being a spiritual struggle and become a means to an end for them.   But first, they still need to convince everybody that their definition of Jihad is the corect one.  They've already done a very thorough job at convincing predominantly christian nations of this, because we know exactly what they're talking about in spite of the weasel wording.  The only question left is, will they convince the rest of Islam?

The resemblance of the orbital photographs is eerie. 

However, I do wonder if volcanism or impact shaped the final form of either crater's edge. 

Although we won't know for certain until we can get the rover up to some of those outcrops, what rocks are visible from Opportunity's current vantage appear shocked, just like at every other impact crater it has visited.  So, I'm willing to say that an impact was what originally dug out the hole.   

I'm not willing to say it formed the "bays" on the crater edge, though.  As your pictures show, there's nothing unique about them in comparison to Crater Lake.  It's entirely possible that both features were shaped by the same factor, which clearly does not require an impact crater.

This is a very interesting observation, RG.

Well, damn if that ain't a simple solution to the whole problem.  Why didn't Senator Frist think of that?

Interesting.  From satellite images, I had expected Victoria to have a ring of higher albedo material around it, but these images show that the crater ring has a relatively complex structure, actually consisting of two or more concentric rings/arcs extending around at least a quarter of the crater rim.

Why the concentric structure?

Hmm....