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#726 Re: Life support systems » Long Term Health Effects - Life on a low grav, rusty planet » 2004-08-23 13:09:33

Sitting behind a desk is a rough simulation of lower gravity.

Does that mean my dreams of space travel have already been partially fulfilled?   big_smile

#727 Re: Interplanetary transportation » Da Vinci in the Running - Let the Space Race Begin! » 2004-08-23 13:06:05

Dangers in launch: Saskatoon potential target should rocket stray

http://www.canada.com/saskatoon/starpho … ...c7e9657

IMHO, Llewelyn is an old stormcrow.

He should learn the proper form for prophesies of this nature: "Either the balloon will launch, and Saskatoon will face destruction, or the balloon will not launch and Saskatoon will be spared."  Llewelyn wants to have it both ways at the same time.   :down:

#728 Re: Science, Technology, and Astronomy » Rutan's SpaceShipTwo! - one passenger, orbital... » 2004-08-19 13:41:21

Burt Rutan never jokes, you turkey. You, maybe--but him, never.

big_smile

That's good, Dick.  Tell us another.

#729 Re: Martian Politics and Economy » New Euthenia and the Rule of 150 - Maintaining Social Cohesion on Mars » 2004-08-19 13:34:27

There is precedent for the idea of restricting settlement population in order to reduce the need for a police force.  The United States abounds with small towns whose residents consider their town "too small for a police force," and that's just one example.  Apparently, small community size is one factor in reducing crime.  (Crime is arguably a reflection of social stability.)  There needs to be some degree of isolation from larger communities, though - either physical or cultural - or the social advantages of a small community can be lost.

The kind of physical isolation required isn't very much.  You just need enough that people know where they don't live.  Requiring a road trip of more than a few minutes between neighborhoods would do. 

I should point out, though, that there is no economic advantage to small community size.  Also, 150 is neither the largest population with a low crime rate nor the largest stable unincorporated community. 

But it's not the lowest, either.  It's acceptable as an arbitrary population for the type of neighborhood you propose.

I'm still concerned with the interaction between neighborhoods, as well as the idea of planned creation of daughter settlements.  Keeping inter-warren relations open enough that they can all be considered to be one settlement could prove problematic.  If you can do that, why do you need an arbitrary(?) upper limit for the settlement population?  I think it would be easier to keep expanding indefinitely using the same pattern, neighborhood by neighborhood, than to expend the effort required to start a whole new settlement.

New Euthenia should leave that investment to its emigrants.

#730 Re: Martian Politics and Economy » New Euthenia and the Rule of 150 - Maintaining Social Cohesion on Mars » 2004-08-18 15:31:42

So, you're going to restrict people to their neighborhoods, then, when everybody finally finds their niche in the warren, bust the neighborhoods up and shuffle half the people off to new warrens in a new location. 

If you don't intend to allow social contacts to survive the birth of a daughter settlement, what's the sense of applying the Rule of 150? 

The Rule of 150 applies most accurately to social contacts, not architecture or urban planning.

#731 Re: Not So Free Chat » Conscience getting in the way? » 2004-08-18 14:49:30

I am uncertain if I would put the argument in such absolutist terms.  (Lest I find myself arguing that my sister, whose life was saved by a pharmacist refusing to submit to prescription procedures, had a "right to die" and it was the pharmacist's job to kill her...) 

However, I think that you're correct about duty being the important concept here. 

The pharmacy regulations in most states are set up to allow deviations from procedure, but those deviations are allowed on the assumption that they can be justified by the fulfillment of the pharmacist's duties.  If the pharmacist isn't doing his job and is just taking advantage of the system to express himself, that's bad.  He should go take up art for self expression instead and leave his patients alone.

Can you imagine something like this happening on a Mars mission?  "Sorry, Commander, but 'clinical depression' is just short for 'character failings'."  Egad!  A sense of duty that actually includes the job a person is supposed to be doing would need to be strongly encouraged, even screened for.  And a severe enough failure to act should be punished.

#732 Re: Planetary transportation » Combining the Rover and Hab - Go RV'ing! » 2004-08-18 13:44:27

Inflatable/deflatable habitats could indeed be the answer to the size problem.  Not everything has to be the size and complexity of the full Transhab package to be useful.  I'm a little worried about performance during repeated inflation & deflation cycles, but inflatable systems can accomodate that if designed properly.

#733 Re: Interplanetary transportation » Is Earths Magnetosphere acting like an ion trap? » 2004-08-16 13:20:55

This could be a good idea for near-Earth applications.

How do the Van Allen belts compare to the solar wind?  I know they have a comparable or higher ion density.

This is a cool idea.   cool

#734 Re: Human missions » Human Base on Venus - An Engineering Challenge » 2004-08-13 14:12:49

Maybe some day an orbital station would pave the way to a human presence in the atmosphere, and I suppose some day maybe on the surface (though I have my doubts anyone will ever try it).

         -- RobS

JP Aerospace had an idea for manned exploration of Venus using their airborne Dark Sky Stations as bases.  I suspect that such a plan could work in tandem with their Airship to Orbit system, provided it could operate properly on Venus. 

All it would have to do is work as advertised.  There's a lot of disagreement on whether the systems proposed by JP Aerospace can do that, but I believe they can.

#735 Re: Not So Free Chat » Same-Sex "Marriage" - Carried over from the old 'Kerry' thread » 2004-08-12 15:19:52

All sins are equal in the eyes of God, Clark.

Jerry Falwell's may be another matter...    big_smile

#736 Re: Life support systems » Nutrition » 2004-08-12 15:05:45

Me!   big_smile  Collards are better, though.

I am surprised to see that they contain more calcium per calorie than milk.  Probably because of milk fat...

#737 Re: Life support systems » Nutrition » 2004-08-11 15:45:12

Two fields besides nutrition might offer insights on the “less food = more performance” hypothesis: Sociology and Child Care.

Regarding the extreme end of the dietary spectrum, starvation, I have some personal observations.  As a foster parent, and a former victim of child neglect myself, I can offer anecdotes from my own experience suggesting that neglect – and starvation is common in neglected children – does indeed temporarily accelerate certain aspects of intellectual development in children.  Unfortunately, this tends to come at the expense of retarding development in other areas, and if the neglect is allowed to continue even those intellectual skills that were briefly enhanced will plateau.  In spite of having single areas where they excel, neglected children tend to do less well on developmental and intelligence tests.  For example, I taught myself to cook my own food at the age of three, but could not talk or understand eye contact.  I’ve no indication that these shortfalls are the result of lack of intellectual interaction with parents, either.  Some of the poorest fed children you’ve ever seen still had playtime with Daddy and Mommy.

So, in general, if you want to teach your child to bake at age three and think you can accomplish this by using starvation to motivate him a little, buy yo’ ass a breadmaker and leave yo’ kid alone.  It won’t work.

Apparently, food is quite tightly tied up with group social dynamics as well as intellectual development.  Its effect on group morale should never be underestimated.

I strongly recommend that you read Jack Stuster’s book, _Bold Endeavors: Lessons from Polar and Space Exploration_ from the US Naval Press.  (ISBN: 155750749X)  It’s an analysis of the sociology of crews serving in extreme environments.  IMHO, it’s one of the most important books a space travel enthusiast can read.  If you think that people should go to Mars, read Zubrin.  If you think that you personally should go, read Stuster. 

Stuster’s book has an entire chapter devoted to food.  The condition of an isolated crew’s food can determine morale as much as any other factor of their working conditions.  Morale determines crew productivity – arguably more so than average intelligence.  It’s generally considered better to overfeed crews and accept the small loss of efficiency this causes than to underfeed them and risk sparking a mutiny – and bad food has been cited in more than one account of mutiny.  Ask yourself this: in the absence of combat, would you prefer a bunch of fat & happy ordinary Joe’s pulling for you, or a bunch of lean & hungry geniuses scheming against you? 

Zubrin claims that the crew will be one of the strongest mission components, and Stuster’s analysis supports that claim.  But you’d better feed them.

#738 Re: Not So Free Chat » Predictions for 2004 - Got one? » 2004-08-10 15:18:38

Nothing says "Vote Bush" like someone freely and without opposition talking about the 'American Gestapo' on a message board for the whole world to see.

Hmm... I'd have thought it said "Forget the polls and emigrate"...   sad

Hmm... Predictions for 2004:

World oil production will plateau.  Prices will continue to rise with only minor, intermittent relief.

No oil will be teleported out of either Antarctica or the Alaskan National Wildlife Refuge to alleviate the situation.

Bush will not win the US Presidential election, but the outcome will be disputed, with the hooplah again centering around some battleground state where "the electoral college wronged us!"  (Ohio...)  roll  This time, smelling blood, the Republicans will actually have the gall to bring the dispute before Congress, with no resolution before January 2005. 

Clark's presidency will thus not be decided this year.

Kerry will finally take a true stand on space exploration, courageously facing down opposition to his plan.  We'll hate it.

Alaska will not secede from the United States of America, but more people will begin to hope they would and leave us alone. 

There will be another out-of-season hurricane.

There will be more mysterious noises on the ISS, followed shortly by NASA's mission control. 

and last but not least...

I will play Clark's Lotto Numbers.

What can I say, I have a psychic affinity for disasters.   sad   :;):

P.S> How can I alter the timestamp on this post to make it look like I posted it in January?   big_smile

#739 Re: Not So Free Chat » New Bush quote. . . - :-) » 2004-08-10 14:28:12

No, not all.

That could be what we need: more stupid rich people.

:laugh:

#740 Re: Not So Free Chat » Peak oil » 2004-08-10 14:25:02

I'm taking a course on renewable energy sources this fall.  Looks like I got there just in time!   :up:

#741 Re: Interplanetary transportation » Fusion for Ground Launch - Is it theoretically possible? » 2004-08-09 15:07:28

Post Script for Jim:

Another difference is that we might be arguing two different threads under the same topic.  Can't really say I care about VTOL vs. HTOL.

#742 Re: Interplanetary transportation » Quantum entaglement as propulsion - Interstellar spaceflight possible? » 2004-08-09 14:45:29

I think that it lasts until one of the particles are observed, basically until they interact with other particles.  I don't think that it can be used to excite particles, just to synchronize their quantum spin states.

Interesting.

Here's an example of a possible means for getting energy out of spin state transitions.

http://www.newmars.com/forums/viewtopic … ...5;t=130

Bell's Inequality (which I think applies to entanglement... could be wrong) simply predicts better than 50/50 odds of corellation for spin states, not exact corellation, so there ought to be an efficiency loss involved.  But if Hafnium 178 can be continually reset to spin state m=2 using quantum entanglement (and then later excited to release that energy), it would be the same as transferring net energy by entanglement, even if the excitation required to release it occured on the other end.

Don't expect everything you put in on the ground to come out at the ship, but there could be enough to run a rocket engine.

#743 Re: Interplanetary transportation » Fusion for Ground Launch - Is it theoretically possible? » 2004-08-09 08:00:20

Suppose, instead, we compared one squirt gun with an exhaust velocity of 1 m/s and another squirt gun, otherwise identical, with an exhaust velocity of 100 m/s. The volume and mass of water squirted is identical; only the velocity differs. So which delivers the most thrust?

Clearly, the answer is the gun with the most powerful spring (or however squirt guns do it) In other words, exhaust velocity is directly proportional to thrust, when mass of water (or, in our case, propellant) is identical.

And so it becomes clear that exhaust velocity and hence thrust, and hence deltaV, is directly proportional to Isp, everything else being equal.

Ah.  We may be coming down to the difference in our arguments.  The difference appears to be what we're holding equal.

A little earlier in this discussion, I posted that entropy and the mechanics of power transfer was a prime reason why a thermal rocket powered by a vented reactor was less thrust efficient than a rocket based on a direct reaction.  Euler called me on it, and two posts later I had to back down from that position because I hadn't allowed for differences in reaction mass between the two types of engine. 

If you insist that the two types of engine must each have the exact same reaction mass, then the entropy objection is again valid, and I can now go back and stand by my earlier assertion.

I'm not going to take that option, because I'm ultimately more interested in thrust and the power required to produce it.  Reaction mass is incidental to me, so I'm not bothering with the assumption that reaction mass is constant.

Your comparison of two water guns with equal reaction mass neglects the power required to produce the thrust in each case.  Thus, it neglects to address my objection.

What about the engine power in each case?

#744 Re: Interplanetary transportation » Fusion for Ground Launch - Is it theoretically possible? » 2004-08-07 12:41:37

...the engine with lower Isp can produce the same amount of thrust while using less energy.

I now put it to you that, by the process of reductio ad absurdum, the logic of this statement can be shown to be absurd and thus false:-

What you are telling us is that if the vehicle' propellant (not engine) had an Isp of zero that would deliver the same thrust while absorbing zero energy—and also that if the propellant had an Isp of infinity it could only deliver the same thrust if it absorbed infinite energy.

So, discarding your earlier proposal and given that deltaV is shown to be directly proportion to the Isp of the propellant and in inverse proportion to the mass of the vehicle, this means that the higher the Isp for a given ship mass the better the acceleration.

Sorry, no.

The objection is about these engines requiring too much power, which is correctly inferred (but admittedly not shown anywhere in this discussion) to mean requiring too much heat.  It's not about them having too much specific impulse. 

Engine power is proportional to some power of specific impulse.  Your "reduction to absurdity" is a trivial observation regarding one data point.  (A mathematically trivial case, that is - meaning it's true but conveys no useful information.) 

You would do better to consider the behavior over a range of specific impulses that will actually give a power output, rather than at the one value that you know will not.  For example, consider rocket engines with exhaust velocities of 10 m/s (about what you'd expect from a child's squirt gun), and 1000 m/s (about what you'd expect from a rocket powered dragster). 

If you're like me, your first impulse is that the rocket powered dragster produces the most thrust.  But if the one with 10 m/s were the Hoover Dam instead?  It has an exhaust velocity similar to a squirt gun.  Adjust the gates just right, and it can put out the same power as the rocket powered dragster.  (You would have to stopper the Hoover Dam down quite a bit to reduce it to the output of a measly dragster rocket, I might add.) 

This equation gives the power of each:

P = 1/2 * F * v

So, this equation gives the thrust of each:

F = 2 * P / v

Given the same power, the engine with the smaller value of v gives more thrust.  Alternately, given a smaller exhaust velocity, a rocket engine MUST have more thrust to develop the same power.

#745 Re: Not So Free Chat » McCain defends Kerry » 2004-08-06 14:12:57

So we've got a deserter and a confessed war criminal on the ballot! Ho-ah!   :laugh:

Um, that's _two_ deserters and confessed war criminals, isn't it?

#746 Re: Interplanetary transportation » Da Vinci in the Running - Let the Space Race Begin! » 2004-08-06 14:01:13

As I understand it, they already have a pilot, and have from the beginning of thei project.

And as for recovering him after the flight, I think enough of that ingenious cloth heat shield will survive that all you'll have to do is wrap the body in it. 

big_smile

#747 Re: Science, Technology, and Astronomy » Solar System:  How Special is It? » 2004-08-05 20:32:09

At any rate, I'm looking for something tidally locked with good atmospheric circulation. Perpetual night, windy and a constant 80 degrees Fahrenheit sounds about perfect.  big_smile

There's some property for sale just south of the Union Carbide plant in Cancer Alley that you might be interested in...

#748 Re: Not So Free Chat » 9/11 Commission Report - Anyone else reading this thing? » 2004-08-05 20:14:59

*Sigh.*  You know, I like that junior senator that Dubya's daddy had for his vice president.  In spite of some bad press, he's a reasonable fellow, and I'd have voted for him instead of our current president.

They ate that man alive for even allowing the impression that he was like this.  But George W Bush - who really is that inept of an orator - gets Texas, the presidency, and possibly a second term.

Where's the justice?

<Edit Addition> Of course, it's looking like George W Bush is going to be one of our most quoted presidents.  I guess there's some poetic justice there...

#749 Re: Planetary transportation » Simple Mars Vehicle Part 1 » 2004-08-05 20:00:03

Sounds nice.  Can you link to a picture to show how it all fits together?

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