Quote from Paradigmnoia

Obviously technology will improve, and must improve or we would have colonized off world places more often already. However, once we start to pull new technologies out of a hat,

I have not pulled any technologies out of a hat. I avoided doing that in the above analysis. I have not speculated much and not proposed anything that is physically impossible. Everything I cite has been proposed and discussed in detail by experts at places like NASA. Other than cold fusoin, most of what I discuss is a straightforward extrapolation of existing technology. The space elevator is a good example. It cannot be made now, but it is within reach. It violates no laws of physics.

Conditions on Mars are now known in great detail thanks to the Martian explorer robots. The weather there and the hazards are well understood. We know that people can survive in space, because they have -- in the space station. We know that robots can "withstand a large temperature interval, it must be impervious to dust and various kinds of radiation" because they do that already, in space telescopes and on Mars. The make-up of asteroids is less well known, but we know that they have a great deal of precious materials, and we know approximately how many there are.

We know that mining in 20 years or 50 years will be almost all be done by robots, because it is already, in first-world mines. The trucks drive themselves. The excavators are mostly automatic and they take only one person, replacing hundreds of people.

Quote from Paradigmnoia

People won't probably be beamed to Mars, etc, but maybe they will. (Star Trek used beaming people to places as a device to eliminate television

Obviously that is impossible as far as anyone knows. Nothing like it on any scale has been accomplished, unless you count quantum cryptography and spooky action at a distance. Which, I suppose you might count, but the scale is different.

I did not include antigravity in the discussion. If we had it, LEO access and planetary exploration would be a cinch. We could do it on an industrial scale in ten years! It would be great, but as far as I know antigravity machines are impossible.

I find discussion like this more interesting when you stick to known technology and near-term extrapolation. I do not even bet heavily on helium-3, because the experts dispute how much there is available on the moon, and how well a helium-3 reactor might work. Many of them say it is promising, so it should be noted.

Okay, I did let myself go, here:

"If you could assemble elements, it would be nifty to build a Dyson sphere, capture solar wind, transmute it, and use it to assemble entire planets. That's thinking big! That would be a handy material to make the sphere itself out of, since it happens to be headed out in all directions anyway."

Ya' gotta love Dyson spheres! Every solar system should have one.

Well mass, velocity and inertia haven't gone out of style.

Voyager 2 popped through the asteroid belt from Earth in something like 80 days, was moving at something like 55000 km/hr, but was quite small and light (720 kg) compared to a decent sized (worth getting) nickel-iron asteroid, and had no means to slow down, stop, and turn around (two out of three of which need to happen on both ends in order to deliver an asteroid).

True that a lump of metal-rock can be pushed around a lot harder without breaking it, but a lot more pushing is needed to move it and 'stop' it effectively also.

There must be a cool spreadsheet or graphic display somewhere that lets one fiddle with the parameters to see what would be required in terms of time, energy, accelerating and decelerating, etc. for moving heavy objects from one place to another in the solar system.

JedRothwell

Click for WAV file: Son, your ego is writing checks your body can't cash!

-Top Gun

Quote from Paradigmnoia

Well mass, velocity and inertia haven't gone out of style.

Voyager 2 popped through the asteroid belt from Earth in something like 80 days, was moving at something like 55000 km/hr, but was quite small and light (720 kg) compared to a decent sized (worth getting) nickel-iron asteroid, and had no means to slow down, stop, and turn around (two out of three of which need to happen on both ends in order to deliver an asteroid).

I wasn't suggesting that a massive object such as an entire asteroid might be propelled at 1 G, or 20 G. I meant space ships. That would take much less energy than propelling an entire asteroid. I do not suppose they would be in a hurry to deliver an asteroid for processing. It could take months or years. Actually, I suppose the processing will be done on site, and only the precious metals or nickel iron steel delivered. You would leave the rest behind.

Perhaps thousands of years from now people will have the ability to propel massive objects such as asteroids at 1 G continuously. I cannot imagine how! Perhaps with anti-matter? I suppose that would also give people the ability to send manned missions to nearby stars. I believe you could reach Alpha Centauri in about 5 years at that acceleration (5 years for the passengers). I do not think fission or fusion rockets with conventional propellant such as hydrogen could operate continuously for 5 years. The mass of propellant is too large. But I think they could operate for interplanetary distances and times.

Someone posted a handy table of interplanetary travel time at 1 G:

Not assuming any time taken for orbital maneuvering, turning halfway 180° to decelerate, assuming closest distance of planets (and Luna) to the Earth, and not accounting for fuel burn (i.e. literal constant 1g acceleration):

• The Moon / Luna:
  Closest to Earth: 356,577 km
  Travel time (at 9.80665 m/s², no deceleration): 2h 22m 12s
  Travel time (at 9.80665 m/s², decelerating halfway): 3h 20m 24s
• Mercury:
  Closest to Earth: 77.3 million km
  Travel time (at 9.80665 m/s², no deceleration): 1d 10h 52m 48s
  Travel time (at 9.80665 m/s², decelerating halfway): 2d 1h 19m 12s
• Venus:
  Closest to Earth: 40 million km
  Travel time (at 9.80665 m/s², no deceleration): 1d 1h 5m 2s
  Travel time (at 9.80665 m/s², decelerating halfway): 1d 11h 28m 48s
• Mars:
  Closest to Earth: 65 million km
  Travel time (at 9.80665 m/s², no deceleration): 1d 7h 58m 5s
  Travel time (at 9.80665 m/s², decelerating halfway): 1d 21h 13m 1s
• Jupiter:
  Closest to Earth: 588 million km
  Travel time (at 9.80665 m/s², no deceleration): 4d 0h 11m 2s
  Travel time (at 9.80665 m/s², decelerating halfway): 5d 16h 2m 2s
• Saturn:
  Closest to Earth: 1.2 billion km
  Travel time (at 9.80665 m/s², no deceleration): 5d 17h 25m 1s
  Travel time (at 9.80665 m/s², decelerating halfway): 8d 2h 20m 24s
• Uranus:
  Closest to Earth: 2.57 billion km
  Travel time (at 9.80665 m/s², no deceleration): 8d 9h 6m 0s
  Travel time (at 9.80665 m/s², decelerating halfway): 11d 20h 24m 0s
• Neptune:
  Closest to Earth: 4.3 billion km
  Travel time (at 9.80665 m/s², no deceleration): 10d 20h 7m 48s
  Travel time (at 9.80665 m/s², decelerating halfway): 15d 7h 52m 48s
• Pluto:
  Closest to Earth: 4.28 billion km
  Travel time (at 9.80665 m/s², no deceleration): 10d 19h 31m 12s
  Travel time (at 9.80665 m/s², decelerating halfway): 15d 7h 1m 12s

https://space.stackexchange.co…ast-will-1g-get-you-there

More thoughts on this --

Quote from JedRothwell

If you tap into the energy of the descending cars with something like a conventional electric railroad or maglev, you can use the electricity generated by the descending cars to drive the ascending cars up. The net cost is practically zero, assuming the mass of freight is the same in both directions.

I suppose it might be many centuries before a mag-lev version is possible. That would call for a heavy track on a solid tower. The designs they are talking about now would be with sheets of material about the width of a newspaper, very thin. They would flap in the wind. Cars would climb them with friction rollers.

With a friction roller version, perhaps you could accomplish this with something like a battery or fuel cell. It would discharge while climbing, and recharge while descending. The net energy expended would be roughly the same as on a 36,000-mile long horizontal track, with no wind resistance.

A massive tower with mag-lev tracks would be much faster with higher traffic capacity.

I do not think the mass of freight would be the same in both directions. At first, most of freight would go up, as planets are colonized and large space stations are built. Decades later, I suppose there would be massive heavy industry in space. That seems like a good place to put it. The rent is free, space to build factories is unlimited and rent-free, and raw materials such as steel will eventually be far cheaper and more abundant. I suppose things like automobiles, robots, steel beams and other heavy equipment will be manufactured in deep space or in geosynchronous factories and then lowered to earth, with a net positive energy balance if you can recover the energy, instead of using friction brakes. Not that we would need the energy, but why not use it if the net flow downward is in the same range as today's containership trade (1.7 billion tons per year)?

I also predict that most field crops will be grown in space, and shipped as finished product, such as flour. This makes more sense than growing it in food factories on earth. The light is free; there is unlimited space; and you can more easily make the atmosphere CO2, which the plants prefer. Assuming we have cold fusion, the light will cost nothing to generate in a food factory on earth, but the LED lighting equipment will cost something, and it will be an engineering problem. Food factories work best with 24-hour lighting, which is what you get in geosynchronous orbit at zero cost with no equipment. Growing tomatoes or roses in space would be more difficult because they have to brought to market more quickly, although a large fraction of cut flowers sold in the U.S. today are growing in giant plant factories in Europe, and shipped on airplanes, so it might work.

I predict that outdoor agriculture will be extinct in 50 to 100 years. It already makes no sense. Food will either be grown in food factories on the ground or in orbit. Not outdoors. The U.S. is the world's largest agricultural exporter. Number two is . . . the Netherlands, which has practically no land area, because they use indoor food factories. The potential savings in land area, water, energy and fertilizer are tremendous.

I hope that meat is grown in vitro. That is cleaner and healthier than today's factory farm animal production, and less cruel. It takes up little space and it does not call for light, so I suppose it will be mainly on the ground.

Space based factories are also a good place to manufacture computer chips and other products that require a vacuum and clean room. It is pretty clean in deep space! Not a lot of dust or gas.

As I said, the concept of pollution or cleaning up mine tailings is meaningless in deep-space extraction and manufacturing. That is another reason it would be cheaper. I suppose you would set up shop on a large asteroid and then extract iron and nickel, purify it, and fabricate steel beams, engines, automobiles or whatever was called for in purchase orders from Earth or Mars. You ship the finished goods. You would keep doing that for decades or centuries until the iron is played out and the asteroid was reduced to rubble. Then you abandon it. Any toxic pollution or mine tailings would be left orbiting where they have been since the solar system formed. Perhaps if there were newly created radioactive garbage or gaseous material that might possibly reach a populated planet, it would be safer to drop the whole thing into the sun. The point is, pollution as we know it would be meaningless.

You would not want to create massive amounts of tailings or dangerous pollution in a geosynchronous factory. You wouldn't want to accidentally drop something like 10 tons of arsenic or plutonium back on earth.

The concept of energy efficiency and conservation would also be meaningless. It would mean something with cold fusion, because the reactors would cost money and they would wear out eventually. But if you used something like solar energy concentrated with Mylar mirrors as a blast furnace, you could easily tap gigawatts of heat at practically no cost. The mirrors would probably last for centuries. There is no dust or wind.

Finally, the earth now has tons of dangerous radioactive waste (radwaste) from fission reactors and nuclear bomb manufacturing. People are wondering what to do with it. They are talking about building structures that will last for 10,000 years. I see no need to do this. Assume that a space elevator is constructed, and then improved, and improved, until hundreds of years from now it is a tower structure with mag-lev propulsion. Assume that it has become far more reliable than any mode of transport today; it has gone for a century without a single serious accident. At that point, you can package up the rad-waste in heavy lead-lined containers. You could probably make them so heavy they would survive falling back to earth by accident. Anyway, you ship them up the elevator. You might store them on the Moon if anyone thinks some of the radwaste might have economic value and it might be extracted someday. If people decide it is too dangerous and will never be worth anything, maybe drop it into the sun. Or bury it in a played-out asteroid mine.

Quote from H-G Branzell

A self-supporting solid tower could theoretically be built with a carbon fiber structure. But in addition to its own weight the tower also will have to carry the major part of, if not all the weight of the mag-lev rail. The magnets and supporting structure for the rail will weigh in at several hundred kilograms per meter. Multiply this with 100 000 000 meters and you will find that the the cost and weight of the rail will be prohibitive (leaving science fiction out of the argument). The enormous weight of the rail will also increase the cost for the supporting tower to a level that on its own will make any budget snap.

Or, as Arthur Clarke put it, blimps will never fly faster than the speed of sound. Yes, we know that.

Quote from H-G Branzell

So why would it be important for humans and their robots to zip around in space to the extent that you are suggesting? It depends on our ultimate goal and this is a goal that we must set up.

The goal is obvious to me. The goal is to increase or knowledge, power and wealth a million-fold. As I said, it is the same goal that led prehistoric people to occupy northern Europe, and to cross the Pacific ocean. It is what we do. It is why our species did not go extinct millions of years ago. The only thing we have going for us is our insatiable curiosity and our drive to make things, do things and go places no one has gone to before. All species have this drive to some extent. In college, I worked on a project measuring this exploratory behavior in guppies. But we humans do not have many other survival skills.

Quote

The goal is obvious to me. The goal is to increase or knowledge, power and wealth a million-fold. As I said, it is the same goal that led prehistoric people to occupy northern Europe, and to cross the Pacific ocean. It is what we do. It is why our species did not go extinct millions of years ago. The only thing we have going for us is our insatiable curiosity and our drive to make things, do things and go places no one has gone to before. All species have this drive to some extent. In college, I worked on a project measuring this exploratory behavior in guppies. But we humans do not have many other survival skills.

The main drive humans seem to have is for uncontrolled reproduction. And that will probably be their undoing, long before Mars is available to colonize and even if it were, how long would it take to overpopulate it also without a lot more enthusiasm than we already have for birth and population control?

Quote from seven_of_twenty

The main drive humans seem to have is for uncontrolled reproduction. And that will probably be their undoing, long before Mars is available to colonize and even if it were, how long would it take to overpopulate it also without a lot more enthusiasm than we already have for birth and population control?

Reproduction is not uncontrolled. The population boom is largely over. The cohort from age 0 to 20 has been stable for the last 20 years in most of the world, and elsewhere it is growing slowly. The population as whole is still increasing rapidly, but that is because older cohorts over age 40 are living longer. Once those cohorts reach natural longevity (around age 80), the population will stop growing, and it may even decline slightly. To put it another way, the birth rate in the third world, and infant mortality, are now at the same level they were in the U.S. in 1963. The health care gap and longevity gap between the first and third world is rapidly closing.

Infant mortality is the best predictor of population growth. The lower it falls, the more children survive, and the less likely it is that parents will have many children. To reduce population growth, you must reduce infant mortality and increase education for girls. Once you accomplish that, the problem largely solves itself. It also helps to reduce poverty. Worldwide poverty has been reduced tremendously in the last 50 years, especially in the last 30 years. Extreme poverty may be extinct in another generation. This has been accompanied by increased education: over 80% of the adult population in the world is now literate. Illiteracy among people of normal intelligence will soon disappear.

For details, see:

More material wealth and less pollution would enhance these trends. If we had food factories capable of feeding everyone with as much food as they wanted at a much lower cost than today, and in vitro meat production, then poverty and infant mortality would decline rapidly. Granted, obesity would increase -- as it has in Mexico, China and some other countries. Also, farm employment would fall drastically. That would be a problem. It is the kind of problem we should prefer to malnutrition. Solutions always have drawbacks.

Quote from H-G Branzell

Saturday night entertainment

Mars movie:

https://www.imdb.com/title/tt0199753/

The box office is open 24/7.

Display More

By The Holy Zarquon!

That's a real BAD movie.

BAD in the meaning of it's just a stupid Hollywood approach to MARS.

If somebody finds that movie entertaining... Well, that depends on the preferences of each individual

Try "The Mars Mini TV-Series" by National Geographics. (YT-Link for selected countries)

(Hint: Elon Musk has a cameo there)

If it is not free in your country or from your TV-Provider, it's worth buying it.

I've watched that twice.

The intro is written by Nick Cave and Warren Ellis and tells you everything/make you feel what you can expect on Mars

(182 seconds is the smallest distance from Earth to Mars for EM-Signals. ~3 Minutes.)

No. You maybe mean 'Interstellar' by Christopher Nolan. (IMDB score 8,6)

But there's a Black Hole, not a Quasar.

'Interstellar' is one of my favourite movies.

'Mars' is a realistic, near future approach to Mars (Year 2033). (IMDB score 7,5)

H-G-B linked to "Red Planet", a IMHO real bad movie. (IMDB score 5,7)