Colonizing the Solar System

[Eclipse Now]

Is it a different kind of radiation? Isn't there intense solar radiation on the surface of Mars and the Moon, and yet people are talking about bases there?

 

Yeah, I say we start at the moon and launch stuff from there. I hear there is water on the moon after all? Silicon for Solar PV, water, a few volatiles for other components.... everything we need for a space program AND a much lower gravity well to get out of.

 

Water Found on the Moon | Wired Science

[Moontanman]

Yes it is a different type of radiation, Jupiter has huge intense band of "vann allen" type radiation caused by the intense magnetic field of Jupiter, electron bombardment in the Jovian system is harsh enough to kill a human in a few minutes. The Earth traps solar radiation too and has Van Allen belts but they are orders of magnitude less than those at Jupiter.

 

Jupiter Radiation Belts Harsher Than Expected

 

Wapedia - Wiki: Magnetosphere of Jupiter.

[CraigD]

Surely one of the main drivers of the really HUGE exponential scenarios is the self-replicating "robots" described in the scenario's above? Do you think they have to be self-aware or approaching human level awareness of their surroundings (even given different senses etc), to be able to do their job? Or could they be partially directed? Or will good old fashioned human beings get out there in habitats to manufacture these energy sources?

My guess – and a low-confidence guess it is – is that the factory robots I describe in “in a 1,000,000 times more energy rich civilization” would be not very dissimilar to present day unmanned spacecraft, capable of performing many tasks fairly autonomously, but, far from having human-like self-awareness, having essentially no planning capability. To paraphrase an old joke, when it comes to manufacturing, creativity has fewer practical applications than you might expect. ;)

 

As for being self-replication machines in the sense long described in literature, I think much of the expected difficulty, and to some extent, mystique, of making such systems comes from the assumption that such machines need

1. Be of a single design
   
2. Be completely autonomous
   

When these requirements are removed, it seems to me that our mundane world has been full of self-replicating machines for the better part of a century or more, since machine-power began being used in nearly every stage of manufacturing processes, from mining to final assembly. Take practically any manufacturing processes, and imagine simply remote-controlling the human parts of it, and you have, in principle, imagined a processes that, once vacuum and radiation-proofed, can be done remotely in space.

 

:) I’m being a bit sneaky in saying “simply remote-control the human parts”, as remote-control robots that actually can do the things we take for granted a human can, such as pick up and precisely position a wide variety of objects, twist a screwdriver, turn a wrench, or clean up a mess, are barely in their infancy. However, I see no hard barriers to eventually achieving what I imagine, and no requirement for true artificial intelligence.

Also, has anyone ever used actual anti-hydrogen or is that still just theoretical?

Cold neutral antihydrogen has been successfully manufactured and stored for short periods in significant quantities since about 2002, with significant improvements in technology through about 2005, and continuing. Several good histories of this are available online, such as CERN’s “antimatter factory” website.

 

Although its feasibility for energy storage has been confirmed, at present antihydrogen is much too expensive to produce and in demand for experiments to use as an engineering fuel. The present-day cost and efficiency of manufacturing antihydrogen (and, occasionally, antihelium) is staggering, leading researchers in the field to note that it’s cost is on the order of $50,000,000,000,000/gram, and all of the antimatter manufactured to date, at the cost of $100 of millions, is about enough to power a single light bulb for a few minutes – were it still around.

 

It’s also proven somewhat harder than anticipated to store antimatter. Although “trap” storage devices that can store neutrally charged antimatter such as antihydrogen with very low power requirements (ordinary disposable batteries are commonly used, because they’re cheap and reliable) have been designed and built, methods or cooling antimatter sufficiently that it can be held in them have proven successful, maximum storage times are on the order of an hour. Charged antiparticles have been successfully stored with on the order of 100 days, but even very cold, can’t be stored as densely as neutral antimatter

The Jovian system will be a harsh environment for even robots much less humans. The radiation is quite intense, and complex computers are vulnerable, humans are out of the question.

I agree, though like the Earth’s radiation belts, Jupiter’s are fairly well-defined, and un-leaky, so as long as humans and vulnerable machines stay out of them – the wiki article you link, Moontan, mentions NASA’s HOPE study concluding that Callisto, the outermost of Jupiter’s large moons, is within the human safe zone at about 1,880,000 km out, while Ganymede at about 1,070,000 km, isn’t. My guess is that any humans living near Jupiter – and, assuming the need for human control of much of the operation, the benefits of having people as close to the worker robots might outweigh the risks and costs – wouldn’t be on the surface of a large moon, but either a very small one or none at all.

 

As demonstrated by the success the long-duration Jupiter orbiters Galileo, despite having been built in anticipation of about 1/3 the radiation encountered, the engineering problems presented are not insurmountable.

 

The strong, extended magnetic field responsible for Jupiter’s radiation belts are the reason why it’s attractive for the “energy mining” I describe, because they provide a means of converting the kinetic energy of bodies orbiting Jupiter into useful energy - in essence, with the addition of relatively small lengths of conductors, Jupiter and its ring/moon system can be used as a giant, already-spinning electric generator. Using it this way will eventually de-orbit whatever body you extract energy from, but not before you’ve gotten all the energy needed for the next step of the larger project.

Is it a different kind of radiation? Isn't there intense solar radiation on the surface of Mars and the Moon, and yet people are talking about bases there?

As Moontanman noted, the radiation levels on the surface of lunar or Martian surface are many times less than those in Jupiter’s radiation belts.

 

As for it being a different kind of radiation, I’d say it’s a difference in quantity, not quality. In both cases, and also with the Earth’s Van Allen belts, the major source of radiation are high-speed protons emitted by the Sun (there’re electrons, too, in different belts, but with about the same speed and much less mass, they’re much lower energy, so not as significant a threat). Jupiter, or any planet with a significant magnetic field, captures these protons, concentrating them in higher densities than the usual solar wind, resulting in belts with more dangerous radiation than in space or on moons and planets. Also, since belts segregate particle by charge, bodies in them can accumulate charge, which can literally lead to sparks flying (also mentioned in Wapedia - Wiki: Magnetosphere of Jupiter).

Yeah, I say we start at the moon and launch stuff from there. I hear there is water on the moon after all? Silicon for Solar PV, water, a few volatiles for other components.... everything we need for a space program AND a much lower gravity well to get out of.

As the greatest accumulation of material near Earth easier to lift into space than from Earth, the Moon is a major resource in space-engineering projects on the scale we’re discussing.

 

However, it’s important to note that, despite it being easier to lift material from the Moon’s surface than from Earth’s, it’s far from easy. Lunar escape velocity is about 2400 m/s, vs. Earth’s 11200, so ignoring complications, it takes about 5% ([math]\left( 2400 / 11200 \right)^2[/math]) as much energy to lift the same mass from the Moon as from Earth. This is still a lot of energy, especially until you can build an efficient device like an electric mass-thrower to do it, and until something like that’s accomplished, also requires a lot of resources. Taking the ca. 1970s Apollo LEMs as examples, about half of the mass of their ascent stages were fuel/propellant – which on the volatile-poor Moon, must almost certainly be imported from Earth at the usual great cost.

 

I think it’s important to take look at space engineering from a high-level, strategic perspective. Just as 19th century industrialists were wise to build factories connected by rivers and railroads to coal mines, large-scale space engineers need to build their factories near large sources of easily usable energy. The main idea of my “in a 1,000,000 times more energy rich civilization” speculation is that the kinetic energy of the moon systems of giant planets is such a source, and a possible step toward using the much greater but less easy-to-get-a-lot-of-power-from source of the Sun.

[Eclipse Now]

Except that the ultimate goal of anti-hydrogen seems to be mainly sci-fi today. :(

 

What was the Kim Stanley Robinson propulsion system using materials gathered from the gas giants themselves? Are we saying that harvesting the gas from Jupiter is now out because the equipment required to do that would be "nuked" by radiation?:confused:

[Theory5]

A space elevator is cool, but have you ever read any books by Ben Bova? (excellent fiction writer, he writes stories about exploring the solar system, a few notable books are mecury, venus, mars, jupiter, and The Sam Gunn Omnibus and all the stories overlap to create one universe.)

A space elevator could be built on the equator, and as was mentioned in a previous post (To tired to go back and find it) wouldnt the space elvator collapse?

The Answer is possibly, but the way to build a space elevator is to create thin strands of a really strong wire, maybe buckyball wire, and build a space station far enough in space. The trick will be to pull thread down from the sky, while also bringing it up in rockets or something, and effectivly create a rope where the space station is pulling up on the rope and the earth is pulling down. And as like in one of Ben Bova's books I think 'terrorism' might be a threat (without the nanobots :-) )

A question I have though is, dont the van allen belts produce enough radiation to be harmful?

[Eclipse Now]

I'm not sure about Earth's Van Allen belts affecting the space elevator, unless there were people required to stay in those Belts. How high are the belts? Surely not high enough to affect the station at the end of the 36k km long elevator?

 

But in the KSR books the Martian space elevator came down, and because it was built quite thick as it came into Mars to crash, with the base of it being pulled around by rotation of Mars, it gradually accumulated speed like a giant whip. The majority of it ended up crashing down around the equator a couple times the speed of sound, with the detonative force of a series of small nukes! (taking out everything within a km or so of the impact line). That was a great moment in storytelling, but also a rather horrible idea when considering the potential impact on earth. What would something like that do for ocean tsunami's around Bangladesh, India, Indonesia, the Carribean, America's and Northern Australia? Yeeeeouch!

 

Make a cool movie effect though. Move over Bruce Willis in Armageddon, the elevator is coming down! Any movie title suggestions?:confused:

[CraigD]

What was the Kim Stanley Robinson propulsion system using materials gathered from the gas giants themselves? Are we saying that harvesting the gas from Jupiter is now out because the equipment required to do that would be "nuked" by radiation?:confused:

No.

 

I’d describe the vicinity of Jupiter is better described as “high wear”, rather than “out”, for spacecraft equipment. A case in point, the Galileo spacecraft, which was designed in anticipation of about 1/3 the radiation it actually encountered, operated successfully there for 7 years, from Dec 1995 to Jan 2002, and well enough to respond to commands and deorbit into Jupiter’s atmosphere Sep 2003.

 

I'm not sure about Earth's Van Allen belts affecting the space elevator, unless there were people required to stay in those Belts. How high are the belts? Surely not high enough to affect the station at the end of the 36k km long elevator?

The inner Van Allen belt, which contains the highest energy particles, extends from roughly 700,000 to 10,000,000 m altitude, so is well below geostationary orbit at about 36,000,000 m (GEO).

 

Though many descriptions of space elevators assume them to be about 36,000,000 m long, with a massive countermass “station” slightly above GEO, and attached to the ground, it’s worth noting, I think, that this isn’t the only possible design, or even necessarily the best. The advantages of having the bottom of the elevator above the ground, at an altitude easy to reach but above the thickest part of the atmosphere (say, 30,000 m altitude) has been discussed in previous threads. The advantage of having it extend far above GEO is that an object (eg: a spacecraft) released at that altitude would have more speed than required for orbit. For instance, at about 10,000,000 above GEO, an object released would escape the Earth. At about 51,000,000 above GEO, an object released at the right time would be given the extra about 2929 m/s needed for a transfer orbit to Mars. Extending above GEO is easier than extending below it, as the acceleration away from GEO is smaller than for extensions below. At 10,000,000 above GEO, it’s about 0.14 m/s/s (about 0.014 g), at 51,000,000, about 0.45 m/s/s.

 

To have 1 g (about 9.8 m/s/s) acceleration, the elevator would have to extend 1,800,000,000 m above GEO, 50 times the distance from GEO to the Earth’s surface, and almost 5 times the distance to the Moon. At about 499,000,000 m, about at the Moon’s orbit, the acceleration’s about 2.65 m/s/s (0.27 g), and an object released there would exit the solar system.

But in the KSR books the Martian space elevator came down …

 

That was a great moment in storytelling, but also a rather horrible idea when considering the potential impact on earth.

Another common depiction of space elevators is that they are very massive. However, calculation like those in “Space elevator cable mass & size calculating program” suggest that only a small difference in material strength results in space elevators being either impossible (as is the case with ordinary high strength steel), massive (as with Kevlar, with a mass of about 3.5e15 kg and a maximum effective circular cross section diameter of about 520 m), or nearly microscopic (as with hypothetical graphite “buckytube” material, with a mass of about 26200 kg and an effective diameter less than 0.001 m).

 

If materials much stronger than present days one are used to build a space elevator – which, given the difficulties bordering on impossibility otherwise, is IMHO likely to be the case if they’re every built - it’s quite possible the resulting structures will actually be lighter than air. In this case, broken cables, of which there are likely to be many, would be cause for concern about a bizarre kind of air pollution, rather than a catastrophic surface impact. Depending on its specific characteristics, this could more hazardous than a massive surface strike – imagine the effect on a jet engine of sucking in a hair-thin, kilometers long, super-strong piece of lighter than air broken space elevator!

[Eclipse Now]

If materials much stronger than present days one are used to build a space elevator – which, given the difficulties bordering on impossibility otherwise, is IMHO likely to be the case if they’re every built - it’s quite possible the resulting structures will actually be lighter than air. In this case, broken cables, of which there are likely to be many, would be cause for concern about a bizarre kind of air pollution, rather than a catastrophic surface impact. Depending on its specific characteristics, this could more hazardous than a massive surface strike – imagine the effect on a jet engine of sucking in a hair-thin, kilometers long, super-strong piece of lighter than air broken space elevator!

 

Another movie for Bruce Willis? Die Hard in a space elevator, where bringing down the space elevator and pointing it into the escaping bad guy's jet is the only way to save the day? OK, I think I need to see Star Trek to get this out of my system....:confused:

[Moontanman]

Another movie for Bruce Willis? Die Hard in a space elevator, where bringing down the space elevator and pointing it into the escaping bad guy's jet is the only way to save the day? OK, I think I need to see Star Trek to get this out of my system....:confused:

 

Don't count on it the new Star Trek is cheesy beyond belief! the directors and writers should be sent to Rura Penthe and left there to rot!

[Eclipse Now]

Hi all,

anyone read through this page? Extremely optimistic stuff about our ability to get out and explore the universe....

p2pnet news Blog Archive Want to help build a space engine?

[CraigD]

anyone read through this page? Extremely optimistic stuff about our ability to get out and explore the universe....

p2pnet news Blog Archive Want to help build a space engine? is certainly optimistic, but – with all due respect to Michael Thomas, who appears to be a distinguished computer engineer – even though many of its links are broken beyond even recovery via archive.org, preventing me from reading all the offered descriptions, I’m pretty sure it’s also unrealistic, and based on an inadequate understanding of basic physics and limited knowledge of spaceflight science fiction and non-fiction.

 

Thomas’s claim

My Linear Particle Accelerator (LINAC) atom smasher concept for electron particle propulsion is a unique proprietary invention developed over the last ten years and takes space propulsion in a direction never thought of by any scientist or organization in history

notwithstanding, the idea of using a linear accelerator or cyclotron to accelerate the reaction mass of a rocket to relativistic speed is not a new one, appearing in at least occasional science fiction stories no later than the 1960s. It’s a fairly obvious approach to the fundamental rocketry problem of maximizing specific impulse ([math]I_{\mbox{sp}}[/math]), a measure of the mass that must be expelled from a rocket (reaction mass) to change it’s momentum: by accelerating the reaction mass to a large fraction of the speed of light ©, then applying force to accelerate it more, the reaction mass is effectively greater when used than when stored as propellant, multiplying the rocket’s [math]I_{\mbox{sp}}[/math], and potentially increasing the amount of useful payload a rocket of a given starting mass can give a given change in velocity (delta V).

 

A problem with such a system, however, is that accelerating the reaction mass to nearly c requires a lot of energy, and, assuming the source of this energy must be carried by the rocket ship, is also equivalent to mass, so even assuming 100% efficiency (a tremendous overstatement), at some point (which I’ve not yet managed to calculate) increasing the propellant speed results in an increase of the mass of propellant + fuel. The machinery needed for an accelerator also threatens to be prohibitively massive compared to the propellant mass it accelerates – the SLAC, for instance, at about 2 miles (3.2 km) long, and even stripped to its essential components, must mass tens of thousands of tons, yet produces miniscule rocket thrust. So the idea that high propellant speed alone is a panacea, or silver bullet solution, to the problems of rocketry is simply wrong.

 

This is not to say that using particle-accelerator techniques in rocket motors is a bad idea, or an unexplored one. The VASIMIR motor, which has been under development since 1979 and is expected to be flown experimentally in space in the next few years is a prominent and promising example of such an approach.

 

This is also not to say that the goal of a spacecraft that can sustain acceleration of 1 g (about 10 m/s/s) is anything but awe-inspiring and worthwhile. However, IMHO, approaching this goal by searching for a radically different rocket motor is not radical enough. I believe it requires completely re-imagining the nature of a spacecraft, abandoning the idea of a self contained vessel reminiscent of an old-fashioned ocean ship, in favor of a system consisting of massive fixed (in solar orbit) facilities in which the payload/crew containing vessel is many orders of magnitude smaller than the total system. The “laser-powered light sail ship Promethius” described in Robert Forward’s 1985 novel Rocheworld is as good a speculative description of such as system as I’ve encountered, though it describes a much more modest performance of 0.01 g acceleration and 0.1 g deceleration for a maximum speed of 0.2 c on a 20 year trip covering 2 light years.

[Eclipse Now]

Just putting aside the fuel & acceleration technical arguments for a moment, what was with his calculations regarding time to Andromeda only taking 29 years? Was that relativistic ship time, while to the outside universe 2 million years has passed?

 

(He wasn't claiming some kind of Faster than light travel was he? :naughty: )

[Jay-qu]

No, you are correct. In ship time it may only take 29 years, but to the (relatively) stationary observer it would take >2.5million years

[Eclipse Now]

Woah! "Planet of the Apes" time... hey, great way to test global warming theory. Take off in a ship, buzz around the interstellar neighbourhood for a few weeks, and come back a few hundred years later. Anyone read Orson Scott Card's "Enders Game" series where one had to basically say goodbye to everyone you knew and loved if going on a "trip"?

[Jay-qu]

Yep, basically its a one way time machine. I am sure if such a technology existed there would be many willing to throw some money in the bank and come back in a few hundred earth years..

[Eclipse Now]

As they say on Slashdot: What could possibly go wrong? :naughty: