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#1 Re: Human missions » Future of Space Shuttles - How could the Space Shuttles be used? » 2002-05-03 00:48:45

As RobS points out, the lunar elevator would only have to extend to the L1 Lagrange point. So its length actually has nothing to do with the moon's rotation period, in the manner that the geostationary altitude has to do with the earth's rotation period.

#2 Re: Human missions » Mars Mission. Step 1 » 2002-05-03 00:37:17

It is science. Its a biological response to a reduced gravity environment. We know for a fact that astronauts who spend considerable amounts of time on the space station, eg. Russian cosmonauts on Mir, suffer from reduced bone density. Consequently they have trouble standing up when they return to earth and they have to go through a program of rehabilitation. The effects wear off after a time as the body is reacclimatized to earth conditions. The question is whether humans and animals who have been born in a reduced gravity environment can ever acclimatize to the gravity on earth. Will their bone density increase?

As an aside, its a reasonable assumption that people born in space will only develope sufficient bone density and muscle to function in their environment.

#3 Re: Human missions » "NASA...You have a problem..." » 2002-05-02 11:08:09

Why does the American military have to get involved in space? Worried about an attack from a hostile nation? It all becomes a self-fulfilling prophecy. The Pentagon foresees a hypothetical threat and puts weapons in space. Other countries feel threatened by American power and consequently also put weapons in space, thereby posing the threat which led to the Pentagon putting weapons in space initially. And we all dance around in nice little circles.

I was happy to read about the Chinese space ambitions on www.spacedaily.com. I thought it might finally get the American space program back on track by giving the US some healthy competition. But I had forgotten about the Pentagon's paranoia. Notice by the way, how all articles on SpaceDaily regarding China are in a section named "Dragon Space". Nice and threatening, huh?

#4 Re: Martian Politics and Economy » KSR Constitution Articles 1 and 2 - Legislative and Executive Departments » 2002-05-01 00:49:40

I think this brings up an important point, which is that if a society isn't progressing then it is degressing. Most societies are continually progressing and if one society stops progressing then relative to the other progressing societies, it is degressing. A society can not maintain its status quo without falling behind in the world.

#5 Re: Human missions » "NASA...You have a problem..." » 2002-04-24 00:20:54

I agree that NASA shouldn't limit itself to solely Mars exploration, but from a scientific point of view Mars is much more interesting than the moon. In geological terms, the moon is just a distant lump of icy rock whereas Mars has had and might still have significant geological activity. But as you mention, there are still worthy technological challenges in going back to the moon.

#6 Re: Human missions » Future of Space Shuttles - How could the Space Shuttles be used? » 2002-04-22 02:56:44

Hi RobHazlewood, assuming that the moon rotates about its own axis every 29 days, then a lunar geosynchronous orbit would be about 90,000 km above the moon's surface. This might be a problem as the elevator would extend out of the moon's sphere of influence (SOI) which extends to about 67,000 km. (For comparison, the SOI of the earth extends to 323,000 km with respect to the moon and to 920,000 km with respect to the sun.) The SOI is a measure of the region around a body in which its gravitational attraction is dominant. Granted, its only a qualitative measure and so it might not be a problem at all. I don't know...but its something to keep in mind. Of course, the problem of a lunar elevator could be simplified if you aligned the elevator cable with the axis of the earth-moon system.

Hi Phobos, just to clear up some points. The lunar elevator would extend from the moon's surface up to a lunar geostationary orbit. Thus, you would still have to travel from LEO to the lunar geostationary orbit (a distance of about 300,000 km) before you could hook up to the lunar space elevator. Have I understood your idea correctly, RobHazlewood?

#7 Re: Life on Mars » Mars Sample Return - Threat of back-contamination » 2002-04-04 13:14:45

There are links to several interesting articles. But there is one thing that I haven't been able to find. One of Zubrin's arguments is that the earth is continuously bombarded by martian meteorites and that there is a high probability that microbes could survive a trip aboard such a meteorite from mars to earth. Hence, if there are microbes on mars then we have almost certainly been exposed to them already. What are the counter-arguments to this point of view?

Interestingly, the current systems architecture of the MSR mission calls for a passive-earth capture. It has even been described as using the earth as a catcher's mit.

#8 Re: Life on Mars » Mars Sample Return - Threat of back-contamination » 2002-04-04 09:06:13

I recently came across the International Committee Against Mars Sample Return (www.icamsr.org). Prior to this, the only arguments that I heard in the debate about the threat of back contamination came from Zubrin. His arguments that the threat is highly exaggerated seems reasonable to me but it is interesting that there are many scientists of notable repute (including biologists) that disagree with him. I still support a MSR primarily because of the technologies it will demonstrate with respect to a manned mission, though I don't think it is necessary to launch a MSR prior to a manned mission. Anyone with arguments for or against the threat of back contamination?

Interesting articles by Zubrin and others on this topic can be found at www.planetary.org.

As an aside, I read an article that claimed that bacteria from the earth were inadvertantly present on the Survejor 3 spacecraft which landed on the moon in 1967. Parts of Survejor 3 were retrieved by the Apollo 12 crew in 1969 and when the parts were examined on earth, a colony of bacteria was found that had apparently survived the two and a half year stay on the moon.

#9 Re: Terraformation » Atmospheric Degeneration » 2002-04-04 03:33:56

Micheal, I've read several of your posts and I have a couple of points which I'd like to make in the same reply even if they pertain to different topics.

a) The magnetic poles are still changing position today. The magnetic declination is the angle between the geographic north pole and the magnetic north pole and this angle changes every year. You'll find the value on all good maps. The time it takes for the magnetic poles to reverse is on the oder of tens of tousands of years and not hundreds of years. This is directly supported by geological evidence: molten lava from the ocean ridges contain ferro-magnetic compounds that align with the magnetic field and as the lava reaches the ocean floor it solidifies. Thus the compounds show how the magnetic field has changed in the past. It also shows that the earth is much older than a few thousand years since we can observe the rate at which the the ocean plates move apart and hence the rate at which the lava is deposited.

b) There is other evidence besides carbon dating that shows that the earth is much older that a few thousand years. For example, the moon's orbital period around the earth (~29 days) exactly matches its rotation about its own axis. (This is why we see the same face of the moon all the time.) This would be a pretty strange coincidence. The reason is that the interaction of the tidal forces between the earth and the moon has slowed down the rotation of the moon just as they are slowing down the rotation of the earth. We can measure this decrease in angular velocity and in many thousands of years, the earth's rotation will equal the orbit period of the moon, i.e. an earth day will equal a month. (For a full explanation see "Bad Astronomy" by Plait.) This effect takes millions of years to happen and hence the earth and moon can not be a few thousand years old. There are many other examples like this that show the earth to be much older than the Bible suggests.

c) You refer to the "ancients" several times when talking about mars. How old are these ancients? Greek astronomers in bc made tables of the motion of heavenly bodies yet they seem unaware of the regular 104 year mars passage that you mention. Likewise Arabic astronomers. Then in the 16 century Kepler was able to deduce laws of planetary motion from the observed motions of the planets. This means that his data was very accurate. Why is something this spectacular not written about explicitly but only through vague references?

d) Jet streams are horizontal winds, not vertical winds. They are high-altitude, high-speed winds that usually separate the colder winds from the warmer winds. Balloonists use jet streams to travel around the world.

I will be interested in hearing your views and ideas as long as they can be backed up by evidence. If your views require the doctrine of "created antiquity", i.e. that the earth was created to look as if it was billions of years old, or similar ideas then it is impossible to refute any claim that you make and hence, we can not have a scientific discussion. smile

#10 Re: Life support systems » Power generation on Mars » 2002-03-21 09:28:02

Well said, Shaun. Nuclear power is the only way forward, at least initially. Its time that we acknowledge that nuclear power can be useful in some situations and that its not something evil and dangerous. Alternative energy sources are great on Earth, but for a Mars mission, they are impractical and risky.

Take wind turbines for example. How would you erect a wind turbine with a rotor diameter of 42 meters on Mars (about 138 feet). The tower would have to be between 30 - 40 meters tall and an equivalent tower on earth weighs 25 tons. The three blades each weigh more than a ton, and the nacelle weighs about 20 tons. It will take considerable effort to lift 20 tons to a height of 30 meters, even in the low Martian gravity.

In addtion, there are several operational constraints. Wind turbines are actually very inefficient in gusty weather. They need steady wind conditions to produce quality power. Gusty weather also shortens their lifetime considerably and necessitates frequent maintenance. Also (and don't laugh) erosion of the composite wings in a dust storm could be severe. Some turbine manufacturers have problems with erosion of the wings due to rain on Earth. The erosion occurs on the leading edge of the wings and is caused by the high tip speeds , which can be around 70 m/s. It might seem strange but its true.

#11 Re: Martian Politics and Economy » Zubrin's claims about the frontier » 2002-03-21 03:40:34

Isn't it a shame how Hollywood has completely miscolored our perception of the American frontier. No doubt there were certain rugged individuals who lived in lawlessness, but by far the majority were "huddled together and dependent on each other". They might have been free in theory, but in practice their freedom was severely limited by their need for survival.

The case will be the same for Mars for a significant amount of time when resources will have to be supplied from Earth. This will necessitate a very strict society, where resources are rationalized. This doesn't have to be the result of a strict ruling body (government) but rather a natural result of their behaviour and need for survival.

#12 Re: Water on Mars » First Odyssey report!! - Finally! :) » 2002-03-06 12:09:06

Its worth noting that the maximum depth of investigation of the gammar ray sensor is about one foot while for the neutron detector it is about three feet. In other words, Odyssey isn't able to see any water below three feet of the surface. There could still be significant deposits of ice below the surface that the Odyssey just can't see.

#13 Re: Interplanetary transportation » Gravito-magnetic effect - "Breakthrough propulsion" » 2002-03-01 06:28:43

The original article on this effect is actually from 1996. Allegedly, Podkletnov submitted a paper to the Journal of Physics but later retracted it before it was published. It caused quite a bit of controversy back then and Tampere University, where Podkletnov worked, denied all knowledge of anit-gravity research. So I wouldn't hold my breath for this.

Most physicists are also very sceptical about anti-gravity because its is not a force but rather a result of the geometry or curvature of space. Hence you would have to change the geometry of space in order to nullify gravity. Its also inportant to distinguish between something that actually changes gravity and something that merely reduces its effect. For example, levitating an object in a magnetic field can easily appear to counteract gravity.

#14 Re: Water on Mars » A Soggy World ... Maybe! - Looking at a Globe of Mars » 2002-02-27 13:18:42

It may be besides the point, but I don't think you can say that life has existed on Earth for 4 billion years. What most of us would call life has only existed for the past 600 million years. Prior to that point, we only have evidence of single cells and they didn't develop a nucleus until about 2 billion years ago. smile

#15 Re: Human missions » GENERATION SHIP ..... MUST READ - Why hasn't one been built yet? » 2002-02-27 12:55:34

A couple of points on the generation ship:

1) Compared to a mars mission, the generation ship is too risky from both a financial and scientific point of view. The likelihood of success is very slim and not enough to justify the huge investment.

2) The practical problems associated with mining minerals and metals from asteroids are not something we can solve within the next five or ten years. How do you get near the asteroid without damaging the spacecraft? How do you retrieve the raw minerals? How do you refine them on the spacecraft? Most minerals have to be burnt in air or reacted with other elements to purify them. These are all significant engineering challenges that won't be solved in one try., but will take years of experience. Then of course, there is the challenge of building a spacecraft in orbit large enough to accomplish the goal.

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