Month: October 2007

Early Oceans of Venus – space – 10 October 2007 – New Scientist Space

Venus is currently drier than a bone. But the high deuterium ratio in the atmosphere hints at isotopic fractionation of a LOT of water in the deep past. Enough for a shallow ocean, or perhaps a deeper one with a bit of tweaking. That’s uncontroversial in most planetological discussions, but what is difficult to determine is just how long that primal ocean lasted for. David Grinspoon and Mark Bullock have suggested strongly that clouds would allow an ocean to last at least a billion years or two, making Venus habitable much longer than previous estimates of a mere 0.5 billion years. In that time enough oxygen might have accumulated from dissociation to give life an oxygenic head-start…
Did Venus’s ancient oceans incubate life? – space – 10 October 2007 – New Scientist Space

…theoretically spores from microbes can be lofted into space electromagnetically and because Venus has no observed magnetic field the atmosphere interacts directly with the solar wind. Life could then be blown outwards to Earth, Mars and even a wet, warm early Titan.

Cosmic ray deflector – space – 13 October 2007 – New Scientist Space

Getting around the planets has one major challenge – cosmic rays. A continual shower of high-energy particles that electrocute cells with every passage through our bodies is a slow way to get cancer and degrade one’s nervous system. Now an engineer has a better idea…
Forget rockets – go to Mars in a cosmic fruit bowl – space – 13 October 2007 – New Scientist Space

…electrostatic deflection of the particles, at least the lower energy ones that do the most damage because of their overwhelming numbers.

Forecasters predict morning drizzle on Titan – space – 11 October 2007 – New Scientist Space

Dreary mornings on Titan…

Forecasters predict morning drizzle on Titan – space – 11 October 2007 – New Scientist Space

…that lurid orange sky that Huygens showed us could really get to me after a while. A light rain would be a welcome change. When Bussard fusors are up and running a shuttle to Titan would take 11-13 weeks, much better than Cassini’s six-plus years.

Ultra-sized Constructions

Air-filled habitats 400,000 km across

Science fiction has explored super-sized habitats of various kinds – Dyson Spheres, Alderson Disks, Ringworlds, Orbitals, and so forth. All of these suffer from one basic fatal flaw – they can’t exist. Solid structures that size can not be made from any known materials and oftentimes the structures are dynamically unstable. For example, both the solid Dyson Sphere and Ringworlds orbit a central star at super-orbital speeds to generate spin-gravity – unless we’re talking a Bob Shaw Orbitsville made of gravity-generating unobtainium. Now a basic fact of physics that a shell/ring will feel no gravitational effects from masses within it and so that orbital position is unstable to small perturbations – eventually it will run into its star.

So what can be built instead? And how big can it get? Karl Schroeder’s Sun of Suns features a 5,000 km wide air-filled sphere made of carbon nanotubes – which is roughly the limit based on the strength of nanotubes. And carbon is the strongest material in great abundance in the Universe. Theoretically there could exist ridiculously strong “materials” made of higgsinos, monopoles and black holes, but all require some glossing over the difficulty of making the stuff and the unknown physics behind some of the claims. For example, the Solar Queendom stories of Wil McCarthy feature a sun-spanning ring made of collapsium – material made of stabilised mini-black holes. Essentially the black holes are arranged so they eliminate their mutual gravity and inertia and they recycle their Hawking radiation – all of which is very fringey physics. Fun, but dubious.

So I wondered just how big a gas filled object could get before it got into trouble with gravity. A volume filled with a gas at constant pressure and temperature (on average) has a limiting size known as the Jeans radius – the point at which the gravitational potential of the mass of gas equals twice its kinetic energy. In equations that’s:

3/5GM^2/R = 3NkT

where G is the gravitational constant, M is the gas mass (kg), R the volume’s radius (m), N the number of gas molecules, k Boltzmann’s constant, and T the gas temperature in Kelvin. Of course the mass, M, equals N*(mu), where (mu) is the molecular mass of the gas. With a bit of rearranging all sorts of interesting bits of data fall out of the equations – a gas sphere of Earth mix, pressure and temperature starts collapsing under its own gravity when it’s 34,761 km across. If we change the gas mix – say 50:50 helium/oxygen – and lower the molecular mass, the radius goes up. If we decrease the pressure the radius also goes up. For that heliox mix at 0.4 bar pressure the sphere is about 229,000 km in radius.

Imagine a sphere containing heliox at 0.4 bar pressure and 400,000 kilometres across – enough volume to fit almost two dozen Jupiters. Interesting thing is that the sphere doesn’t have to hold the gas in by brute strength if it’s thick enough – self-gravity of the sphere and the gas mass provides the counter-pressure. If we make it from diamond (the strongest carbon allotrope, density 3.5) then it only has to be 1,345 metres thick for its gravity and the gas’s gravity to provide sufficient counterpressure.

And the mass? Just 0.4 Earth masses for the shell, and 0.655 for the gas – thus just a bit more than an Earth mass. Such masses are ludicrously large for us mere mortals to contemplate, but for the postulated Post-humanity of current SF such a project may well appeal. And if it can be done, out in the Cosmos there may be Someone who has already done so.

Such an object would be opaque – even gas and diamond at such thicknesses is opaque, though look out for interesting refraction during an eclipse – and an ideal target for a transit search. If a civilization felt the need it might totally re-engineer its star system and populate it with potentially thousands of such objects, which would be entirely stable given suitably convoluted orbital design. A Dyson Swarm – as Freeman Dyson originally meant it – rather than a solid Sphere. Such a re-engineered system would stand out like a sore thumb to distant observers, thus providing one motive for the idea – getting the Galaxy’s attention. All the habitable volume – given suitable artificial stars within – would be another motive, but beings able to disassemble planets would hopefully have tamed the urge to runaway population growth.

The Choice

Alan Boyle posted some thoughts on the next 50 years of spaceflight at his MSNBC CosmicLog. The comments were what I’d expect from enthusiasts and cynics. A lot of doom & gloom, plus runaway enthusiasm.

I am not a moderate on the importance of spaceflight, interstellar colonisation.

Is there a middle ground? Or is there a BIGGER reason for spaceflight? How about the survival of the Universe?

Life is insignificant NOW, but in a few billion years our descendents could be shaping entire segments of the visible universe. And in a few trillion years, as the last stars die, they’ll be doing even more dramatic things to sustain Life.

One possibility is that, left to itself, the Universe will “crash” because all the quantum information that makes the laws of physics possible will be erased by black hole decay – if the Universe expands forever. Can we stop the expansion? One theory is that the current acceleration is caused by the Higgs field not being in its true vacuum state, due to the presence of baryonic matter. If Life uses baryons, via reverse baryogenesis, for power then the Higgs field will cancel out and the Universe will recollapse.

Now a Big Crunch sounds bad, but guided by Life shifting mass around on a cosmic scale, the recollapse can both provide energy for Life and a heat-sink to make that energy usable. And that infinite recollapse energy can power infinite experiential states – infinite subjective time for an infinite number of beings – between Now and the End Point.

Thus Life doesn’t have to end – if we set out and “conquer” the Universe. Don’t worry about wars between intelligent life elsewhere in the cosmos – They’re too far away for us to meet up until a few trillion years from now. Else They would be here by now, if they were closer than about 13 billion light years. And in a few trillion years we, and They, will know how to get on better than we do now.

Or else we don’t have a future.

A simple choice:

Everything – real Infinity for all of us;

or Nothing.

Bussard Fusor papers online

Oil can be made PURE GREEN by fusion power

Robert Bussard’s Polywell Fusor design is incredibly exciting for any space enthusiast because it promises REAL atomic power for spaceflight. Sure fission rockets have been “atomic power” in our minds since the late 1940s, but any fission reactor is such a cranky system and only offers thermal power generation options. Aneutronic fusion – the burning of Lithium-6, Helium-3 or protium-Boron-11 – offers something utterly different: direct energy conversion. In the case of p+B11 => 3He4 fusion/fission reactions the energy of the produced alpha particles can be turned into electricity at ~ 95% efficiency. This is a real breakthrough – or will be when Bussard gets proper funding – as electrical power can be used to heat reaction mass via relativistic electron beam guns. Ionised exhaust and no thermal contact with the reaction mass means the exhaust velocity can be pushed a lot higher, thus the vehicle can use just plain water as reaction mass.

Thanks to Askmar (Emerging Technology Marketing) Bussard’s papers are available online for all to see…

IEC Fusion at Askmar

…have a quick browse, but for specific breakdowns of Bussard’s estimated costings of

  • A 4000 person colony on the Moon
  • A 1200 person colony on Mars
  • A 400 person colony on Titan

    • …all for less than the NASA budget over the same time period, then check out this one:

    System Technical and Economic Features of QED-Engine Drive Space Transportation

    …QED being “Quiet Electric Discharge” or Monster Electron Guns blasting stuff into plasma Engines.

    The transformation of the world’s power economy is a little bit harder to discern. Firstly, to minimise replacement costs and timelines Bussard proposes using D-D fusion for power extraction via the neutron flux. Neutrons would heat water, and that would directly hook-up with regular steam-plant at a pre-existing coal/fission power-plant. All new power-plant could then use aneutronic fuels and minimise thermal losses by direct power conversion.

    All sorts of liquid fuels could be made using a fusor at some point in the production cycle, without any greenhouse emissions being needed. Ethanol or methanol are good options, but eventually battery/ultra-capacitor technology might make liquid fuels an irrelevance. However hydrocarbon engines are so power dense it’s hard to see just how successful that transition will be. Fusion heating could make extracting oil from very marginal deposits highly practical and fusion-powered atmosphere processes could draw-down carbon dioxide directly from the atmosphere. In fact it’s perfectly feasible to re-form hydrocarbon fuels directly from water-and-carbon-dioxide exhausts via fusion energy. Thus oil, as a high-density energy-storage medium, might never have to be abandoned, even if it does have to be made PURE GREEN via fusion power. After all oil is essentially a natural product, used by virtually all living things to store energy – we know it as “fats and oils” as part of a healthy diet.

    A suitably high energy density storage system would make small electric aircraft perfectly feasible, and a large aircraft could have on-board fusors and essentially infinite range. By extracting deuterium from the atmosphere an aircraft could stay aloft without refuelling, resupplied by small shuttle planes. Such a system might allow larger luxury air-vehicles to fly continuous routes, loading and unloading via shuttles from airports along the way.

    Once Robert Bussard’s work is completed with a working power reactor then we’ll know if fusion power will yet save the world.

Old Testament numbers explained

The Exodus out of Egypt of the Israelites was a pivotal event for the Jews as a people, and for Judaism/Christianity as religions. Robert Silverberg’s “Roma Aeterna” series posits an alt.history in which the Jews never left – at least until 1970 (our calendar) or 2723 by the Empire’s own calendar.

Aside from interminable difficulties correlating the stratigraphy of the event, the Bible’s numbers are rather suspect. In “Numbers” we get a count of 603,550 men, 20 or older. That would imply about 2.4 million people left Egypt – it’s hard to imagine them fitting in Ancient Egypt as its population is usually estimated at about 1 million. Even harder to believe is the Bible’s claim that the 7 nations Israel was to expel were “greater than Israel” – 21 million people could not have survived in Bronze Age Canaan.

In a 1967 issue of the Tyndale Bulletin Biblical scholar John Wenham posed a rather neat solution – the “numbers” used were also words and the meaning had drifted between the composing of “Numbers” (or its source/s) and the final Redaction of the Torah we have from Ezra/Nehemiah’s day. Thus the words meaning “commander of thousands” and “commander of hundreds” (themselves hyperbole) had been shortened to “thousands” and “hundreds” and thus the later scribes had written them as numbers. This has numerous examples and parallels in the often glaringly different figures between the parallel historical books – “Kings”/”Chronicles”, “Ezra”/”Nehemiah”, and the various old scribal traditions, like the LXX, the Samaritan and Masoretic texts.

Now that John Wenham paper is online…

Large Numbers in the Old Testament

…apparently it’s a condensed version of a longer paper, but by itself it’s quite worthwhile. Makes a lot of sense out of a whole lot of quite silly theorising about multi-millions crossing the Red Sea etc. etc. Wenham figures the adult men number about 18,000 and thus the total populace is 72,000. Still a BIG population to shift across the Sinai, but we know the Hyksos moved about 200,000 on a similar exodus after Ahmose destroyed their major fortresses.