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Posts posted by Moonguy

  1. In the LONG term (millions or billions of years), survival of humanity, and perhaps a number of important plant and animal species, will mean thriving somewhere else besides Earth.


    In the short term, it will be very interesting to see IF humans can live indefinitely in a space colony.


    Your "abandonment psychology" theory is absurd. Living in a space colony is far riskier than living on Earth. Few people would be willing to risk their lives that way. However, if it can be shown that it is perfectly safe, comfortable, and maybe even fun, then people may get in line to try it out.


    Your premise of preserving species through space colonies is plausible enough if you assume the colonies are successful. Remember, this thread started as a discussion about asteroid mining to build colonies. That takes money. The 'species survival' angle sounds good until you realize it is FAR cheaper and more certain if you just get rid of nuclear weapons, stop butchering the environment and put an end to pointless warfare. I could think of a few other measures to ensure human survival that have nothing to do with space colonization. My point is that the people you expect/hope to pay for colonization will not be impressed by esoteric arguments. They want money for their money. That is why space colonization has failed as a potential advance for humanity.

    I truly wish it were otherwise. I have my own visions for space colonization, but I have to let people know that I respect their money before I spend it. . .

  2. The goal of humanity is to develop rotating space colonies with artificial gravity and shielding from cosmic rays, that are self-sustaining (grow plants and raise animals for food), and recycle everything. A space colony should be able to repair itself using materials fabricated from asteroid metals.


    A convenient place to build such colonies is among the asteroids, so ice and metals from the asteroids can be used to build more space colonies and enlarge existing ones. In a sense it would be healthier to live on a rotating space colony with one full g gravity, than on Mars with such low gravity that your body would be weakened.

    The 'goal of humanity' is to survive. There has never been an adequate answer to the question of how space settlements, in any form, enable the Earth-bound majority of 'Humanity' to survive. What has been presented is the assumption that settlements guarantee survival even if Earth-bound humanity destroys itself. It is abandonment psychology at its worst: 'YOU might get blown up, Earthling, but at least I will be safe in my tin can. . .' Can you wonder why space colony advocates aren't taken seriously anywhere outside of the advocacy?

  3. I see little use for bringing materials from asteroids back to Earth. One of the things that makes space travel so costly is starting out with such a huge expenditure just to make it offplanet with enough resources to do anything. If asteroid resources stayed in space for use in space, our costs for working in space go way down.


    As far as NASA expenditures, they've always paid big returns in technology and engineering advancements. And why wouldn't we want offworld expenses to be met with offworld resources? Do we need to strip this planet to explore the rest of the system?

    It would be possible for a colony to finance itself if thousands of people simultaneously invested their money in businesses here and then committed the dividends to supporting the settlement's import needs. Since asteroids have the physical resources, they would import energy in the form of power panels. The settlers would then concentrate on making their own consumer goods.

  4. Moonguy, perhaps you have solved the Fermi Paradox. There is no way for people to thrive in space. To make a living in space, people need energy and resources. If there is energy, resources are available. Solar energy in the asteroid belt is iffy; the only alternative is fissionable material, unless controlled fusion is possible.


    Given energy water can be split into hydrogen and oxygen, and ion engines can be used to conserve fuel. Asteroids should provide metal to build and repair spaceships and space stations, and must provide expendable resources. Although, recycling everything is required, some things will unavoidably escape into space. Mostly, resources are required for population growth. Is there any need to sell things minded on asteroids to Earthbound people? Even if a population can survive without trade, they like to trade for luxuries they do not or cannot make.


    Is there something that limits this potential space faring population? IDK of anything.

    Yes, there is a big limiter: the fact you are spending other people's money to start these things.

    taxpayers, corporate investors, business lenders, stockholders all want the earliest returns for their cash invested. It is not about greed. It is about the cost of money to the people 'lending' it.

    Even NASA does not have the prerogative of spending other people's money without regarding the cost of that money - and taxpayer dollars are, functionally, a form of loan. Those 'other people' live on Earth and will for some time. They need to be satisfied the project they are paying for at least has an even shot at making good.

  5. I'd think asteroids in the main asteroid belt would have regular orbits like the planets and regular launch windows. In addition, it is always possible to launch to get to some asteroid at any time. Moreover, launching from a planet costs much more fuel than from an asteroid.


    AFAIK the only metal likely to be on asteroids that might be worth mining is iridium, and that is doubtful even if they found pure iridium nuggets. I believe, the other rare elements aren't expected to be on asteroids. Thus, I believe you are right Moonguy, mining asteroids to send stuff to Earth is unlikely to be economically feasible.


    The only possible scenario I can think of for that to change is if people decide to migrate into space stations, but that is only sci-fi ATM.


    Much of the attraction to asteroid mining has been focused on the low escape velocities from asteroid bodies. Main Belt asteroids are no exception even though they are much larger and more massive than NEO's. The problem is the larger delta-V needed to transport masses of processed materials back to Earth from that region of space. Worse: the only reasonable method for transport would have to be a chemical rocket of some sort burning a propellant manufactured on site. Highly doubtful the rewards would match or exceed the cost.

  6. Has any solar sail/motor type of device has ever been built and worked on earth, experimentally ?

    Sort of a Crooke's radiometer, with the radiation-pushed half of a spinning sail exposed to sunlight and the returning half shaded, all perhaps in high vacuum ?


    If half the globe of a Crooke's radiometer is shaded, would such be an equivalent of a solar sail motor ?

    Japan's space agency, JAXA, has successfully flown a probe to Venus using a solar sail called IKAROS. Solar sails must now be regarded as a 'proven' technology - TRL 9 or 10. It remains to be seen how large they can be made. Since solar sails rely exclusively on solar photon pressure to operate, there is no 'motor' as we usually think of, such as an 'ion drive' would have.

    A radiometer-based engine would be close to the elusive 'perpetual motion' machine. The problem is any mass of propellant would have to be expended at great velocity or be extremely large. There are mechanical limits to how fast a radiometer can spin with existing materials. Still, iI is an intriguing thought. . .

  7. Mining asteroids is HOW we will become a space-faring species. They are a handy supply of ice which can be converted into water, air, and fuel, and they have many useful metals and such.

    Every solid planet in the Solar System has water on its surface or (in Venus' case) in it's atmosphere. There is no longer any great concern about being able to provide future settlements with water. The major planets have the advantage of more regular launch window availability than asteroids. Regular deliveries of a product is important to keeping costs manageable. Asteroids offer relatively limited options for marketable materials. Only those metals for which we have markets on Earth are reasonable for development. In-space markets could appear in time, but they do not exist yet and asteroid mining, by itself, will not change that. Sorry to be so negative, but it is important to stay connected with reality if we intend to change that reality.

    I regret I was not on this forum when this was first posted. . . Timing is everything!!

  8. Once again, a very nicely done piece!!

    You can imagine how useful this is for operations at Mercury. Not only is Mercury the best environment for operating sails, it is the best for their fabrication as well. A facility on Mercury can mass produce ail material from local sources (including the polymides) and build fleets of sails for a fraction of the cost of identical Earth-launched counterparts.

    Sails launching from Mercury's orbit have the benefit of at least six times the photon flux. As a result, a given payload mass launched from Mercury will develop the needed velocity much faster than the same mass being launched by the same sail from Earth's orbit. Alternately, much larger masses can be transported if we are ok with more cruise time.

    It's the money involved that matters.

    If you look at the equipment that would be needed to build sails, it is way less than that needed to build 777 aircraft or even cars. The only difficult task is stowing the 4 square kilometer sail for launch. If you are launching from a planetary surface with no atmosphere, the task is easier. If the sail is constructed in orbit by a self-positioning assembly jig, it is only really a matter of joining spars (and mast, if there is one) to a control/docking hub and then attaching the sail material rolled out from cassettes. Most of the jig would be open space-frame structure while only a few elements would be dense concentrations of machinery.

    The only real limiter to solar sails is how much payload we can launch for a given mission from the planet's surface. Here again Mercury has the advantage.

    What evolves from this is huge potential for economical mass transport all over the Solar System.

  9. ii I think it's very interesting that a rouge planet could have a hydrogen atmosphere and water oceans due to internal heat and greenhouse effect of hydrogen... makes for some interesting bio chemistry speculation... VENUS IS A SLUT...evil.gif

    '. . .rouge planet'? Planet's wearing lipstick?

  10. Tanks are heavy but you could use inflatable reservoirs.


    once when I was younger I thought that on say a moon base a U bend of water could provide a efficient an quicker airlock until I realized that as air pressure decreases so does the boiling point of water until it goes directly from ice to vapor. On somewhere like Titan it would freeze.

    I get the idea of a 'U-bend' airlock. Wouldn't it work if the astronaut enters it when it is full of fluid, then pumps out the fluid replacing it with either the outside atmosphere (Mars or Titan) or vacuum (Moon or Mercury)? The concept presented here seems aimed at reducing the 'pump-down' time by eliminating the need to pump out air, which is a power-hungry way to go. Fluids are better because they don't need to be pumped. Just open a floor drain to a tank positioned lower than the air lock and it runs out via gravity.

  11. I hope this will be on-topic: Would the extruded panels with corrugations necessarily require an 'outer' skin? Oriented in line with the thrust axis, I would think the corrugations would provide adequate stiffness against panel flutter. For thermal insulation, half of the tank circumference is naked to the air but could easily be protected with spray-on foam. This would also tend to 'smooth' the surface of the tanks and reduce friction losses.

  12. Looking at this concept, I am reminded of how Titan's atmosphere contains more than enough Hydrogen Cyanide in concentration to kill a person. You do not want this stuff on your suit, so this might be an excellent way to clean off spacesuits using a fluid that reacts Cyanide into harmless agents. I'm not sure water will do that, but maybe something resembling a dense fluid ('gel') or a series of different fluids?

  13. I bet CIA saliva is flowing over this juicy tidbit, and I expect a movie will soon appear with a similar, future, hand held technology being used to interrogate terrorists, criminal suspects, or (stealth version) political rivals. Soon someone will report aliens are scanning our brains from orbit, they no longer need to abduct a person for examination.

    Never mind the CIA. I can see where wives would really go for this idea! Stalkers too, for that matter. . .

    Do they already have hand-held MRI machines?

  14. It seems they wouldn't use most the fuels we use, since most of what we use is not even as good as liquid hydrogen. Seems to me liquid Hydrogen would be the worst fuel they might use, while antimatter is the best fuel. Although, if these were hypothetically the worst and best(energy to volume ratio) fuels they are willing to use, then couldn't they have more dense versions of these fuels as well? For example if hydrogen gas is good then a more compressed hydrogen would be better?

    Logical. I imagine they would have the awareness to appreciate antimatter over Hydrogen. . . They may have better insight as to how to manage antimatter as a propulsive energy source. A caveat: We may be talking about several intelligent species and there may be vast differences in how they approach the matter, technologically speaking. That said, they all still have to work with the same elements and physical laws we do. Maybe there is an 'all roads lead to antimatter' reality we just have been a little slow in appreciating. . .

  15. Yes, near the end of its' life the sun will lose much mass and the outer planets will continue at the same speed which may cause them to spiral away from the sun. They could fly off into interstallar space.




    "When the helium is exhausted, the Sun will repeat the expansion it followed when the hydrogen in the core was exhausted, except that this time it all happens faster, and the Sun becomes larger and more luminous. This is the asymptotic giant branch (AGB) phase, and the Sun is alternately burning hydrogen in a shell or helium in a deeper shell. After about 20 million years on the early AGB, the Sun becomes increasingly unstable, with rapid mass loss and thermal pulses that increase the size and luminosity for a few hundred years every 100,000 years or so. The thermal pulses become larger each time, with the later pulses pushing the luminosity to as much as 5,000 times the current level and the radius to over 1 AU.[109] Models vary depending on the rate and timing of mass loss. Models that have higher mass loss on the RGB produce smaller, less luminous stars at the tip of the AGB, perhaps only 2,000 times the luminosity and less than 200 times the radius.[108] For the Sun, four thermal pulses are predicted before it completely loses its outer envelope and starts to make a planetary nebula. By the end of that phase - lasting approximately 500,000 years - the Sun will only have about half of its current mass."


    O.k. Thanks!

    It would seem this supports the basic notion of planets escaping stars as they go through this process. . . It would further seem that this has happened many millions of times in cosmic history, which further suggests there are millions of free-floating planets out there.


    Now, what I'm wondering is how to detect them. Reflected light is not an option, so I am wondering if internal heat would be detectable at interstellar distances for planets like Earth or Mercury or even Jupiter. . .

  16. The volume of an object has essentially no impact on it's gravitational pull unless it expands to the point that you are inside of it.


    If a star has 1 solar mass with a center of gravity 1 AU from a planet, the gravity felt by that planet will not change regardless of what the star does unless it changes one of those two qualities. Expansion and contraction will not change the mass nor the center of gravity, so unless the star expands to engulf the planet, the planet probably won't notice anything different about the gravitational pull it experiences.

    Don't stars blast substantial mass away from their surfaces when they are expanding?

  17. Where did you get the idea that stars would fluctuate gravitationally as they die? This could only be a result of mass fluctuation. Dying stars would change mass very slowly unless they explode (supernovae).

    ". . . unless they explode.'

    It was my understanding that stars contract and expand as they go through their final phases prior to final detonation. That has to play havoc with the stability of orbiting planets. . . some are bound to break free.

  18. Your work is impressively thorough.

    Correct me if I'm wrong, but the propellants you suggest are all sustainable from off-Earth resources? Including the 'Pmdeta'?

    It would seem this system is mechanically easier to function with in remote locations (i.e. Mars, Mercury. . .,) and it lends itself to reusable stage designs. . .

  19. The periodic table would be the same everywhere. The laws of physics would also be the same. So they would use the propellants - if any - that we use. They would encounter the same action=reaction reality that rocket travel is based on, so it follows they would develop some sort of rocketry. How long they stayed with that inefficient of a technology depends only on their imagination and socio-economic system. Specifically, do they have a means of acquiring the resources to make it happen.

  20. SPECULATION: As stars die, they go through major fluctuations in their gravitational strength. This would enable planets in orbit around those stars to escape - particularly the outermost planets. Escaping their parent stars, they would eventually become undetectable through reflected light.


    QUESTION: Would it be possible to detect these planets from infrared signals if they had internal heating?

  21. I am wondering if there are implications from this for other telescopes, such as the James Webb, that are designed for orbital stationing instead of on a solid surface. . .


    The decision to end Kepler's extended mission was economic at root. Orbiting telescopes cannot be accessed by humans without billion dollar space launches. A telescope mounted on a solid, stable surface such as the Moon or, my personal favorite, Mercury, would be accessible at a fraction of the cost. Just sayin'. . .

  22. The interesting possibility would be that if there is enough water on Mercury, and if by robotic exploration we would find out how much and accurately where water exists, a manned spacecraft could someday convert solar radiation into electricity that could dissasociate water into oxygen and hydrogen, a great rocket fuel for a return trip. This technique might also be used for a round trip to Mars and the moons of Jupiter, to get a spacecraft back, using either solar energy or atomic energy for the electricity needed to dissasociate water and create fuel. And of course water would be needed in the more distant future for the underground human colonization of Mercury near its polar regions, which also seeminly would be feasible to learn first on our moon.


    Of course water could also be manufactured on the moon, Mars, and Mercury from materials found near the surface, if there is otherwise a sparcity of water at a particular location, or if transportation of water at that location might be more costly to find and/or transport.

    The most recent estimates put Mercury's water supply into the trillions of tons. Developing Mercury's resources would be more about using them to make finished products than just exporting raw ores back to Earth or Mars. Mars has all the same resources Mercury has. What it does not have is the energy supply Mercury has. Particularly where solar heat is concerned. Mercury has twenty times the solar flux of Mars. That makes it cheaper to produce tons of whatever you care to fabricate. The fact that Mercury can send materials to Mars seven times more frequently than Earth is also a point in Mercury's favor. Individual sails are inherently more efficient when flown from Mercury than Earth - they carry more payload for a given sail area and accelerate at a faster rate than Earth-launched counterparts. Overall, transporting a mass from Mercury to Mars is cheaper than transporting the same mass from Earth.


    What I see evolving from this is a scenario where Mars and Mercury are developed more or less simultaneously. Mercury is given the tools to develop construction materials for Mars. Mars colonization would proceed at a greater pace as Earth's transportation system would be utilized more efficiently by not having to send so much deadweight


    As for asteroids. . . The delta-V advantage they have does not quite cancel the fact they are interplanetary missions with infrequent launch windows. The more their orbits resemble the Earth's, the more they share of Earth's launch window disadvantage for interplanetary missions. .

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