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Monday July 4th 2011


Notes & Queries 3/5/10

Nuclear Cannon A Descendant of Orion

The new Carnival of Space is now out, from which I’ll focus on Brian Wang’s interesting notions on nuclear propulsion. The power behind the indispensable Next Big Future site, Brian has been writing about an Orion variant for some time now, one that should be able to get around the nuclear testing restrictions that put Orion itself into mothballs. A 1963 treaty effectively ended Orion’s prospects, and in 1974 the Threshold Test Ban Treaty was signed, prohibiting the testing of nuclear devices with a yield exceeding 150 kilotons. What can we do with a 150 kiloton upper limit for underground devices, and how does it relate to pulsed propulsion?

Wang envisions building what he calls a ‘nuclear cannon,’ capable of launching heavy payloads into Earth orbit. A 150 kiloton nuclear device is placed at the bottom of a two-mile shaft, packed with boron and other elements that will be converted to plasma. The 3500 ton launch projectile is placed on top. The explosion of the nuke launches it, with a chemical charge being used to quickly fill in the shaft as soon as the projectile clears it, the idea being to contain contamination. Figuring $10 million for the projectile and the propellant to launch it, plus another $20 million for construction of the shaft, Wang calculates launch costs in the neighborhood of $10 per pound, far cheaper than current launch options including the low-ball Russian Dnepr, a three-stage converted ICBM.

We’re not talking human missions here (not at 5000 G’s!) but heavy lift of the basic supplies for industrialization, with our standard launch systems being reserved for more fragile supplies and astronauts. Here’s Wang’s summation of the project’s cost and potential savings:

…100,000 tons of cargo delivered to the moon would be worth $5 trillion at the best prices today. 200,000 tons delivered to orbit would be worth $1 trillion @$5000/kg. If this could be done at one tenth the cost it is still worth $100 billion to orbit and $500 billion to the moon. Getting to one tenth of current costs is an optimistic ten years away and billions in development. The cost is to find a location like another remote island to sacrifice the underground area for nuclear launch similar to the areas sacrificed for underground nuclear testing. However, with proper preparation and a dome with a door and charges to speed the collapse of the shaft, there would be no radiation into the atmosphere.

It’s an intriguing notion, and not out of line with other industrial activities:

Other industries like oil, gas and coal regularly contaminate salt domes and underground and above ground locations. This would be safer and cleaner than those continuing operations. We would use nuclear bombs that are costing money to be maintained in storage and have a risk non-peaceful use. There is no risk of damaging EMP because damaging EMP occurs when a nuclear device is exploded at high altitude.

Interesting concept! Read more about the details here. And be aware that the regular postings of the Carnival of Space, which Brian handled this past week, are a good place to keep up with insights from space bloggers. This week you’ll find, in addition to the nuclear cannon and related links, a mind-boggling look at a Martian avalanche, a discussion of bad science in the movies (Apollo 13 and Contact stand out as exceptions to the rule that Hollywood invariably botches the science in the service of dubious plot lines), and Russia’s allocation of about $16 million for nuclear space projects this year, with plans to increase to $580 million over the next nine. Is the Russian initiative a keeper, and will it inspire new nuclear technologies from the West?

An Eerie Silence Indeed

Prolific author and physicist Paul Davies (Arizona State) will be offering an online lecture on March 31 covering our current SETI work and the prospects for extending it in new directions. His new book The Eerie Silence: Are We Alone in the Universe is just out this month from Penguin. Davies offers up an overview of our quest for extraterrestrial intelligence in a thoughtful piece on physicsworld.com, one that encapsulates the history of the discipline and asks whether we shouldn’t be thinking of expanding our horizons. It’s always interesting to note that current SETI research is almost all privately funded, with the 350-dish Allen Telescope Array now under construction growing from the philanthropy of Microsoft co-founder Paul Allen, and numerous activities coordinated by the SETI Institute and other sources working the sky on a regular basis.

Davies has his doubts that a scenario like Carl Sagan’s Contact, in which a civilization elsewhere in the galaxy beams messages to establish dialogue and provide wisdom, is really credible:

A major problem with Sagan’s thesis is that if there are any aliens out there, they almost certainly have no idea that the Earth hosts a radio-savvy civilization. Suppose there is an advanced alien community 500 light-years away – close even by optimistic SETI standards – then however fancy their technology might be, the aliens will see the Earth today as it was in the year 1510, long before the industrial revolution. In principle they could detect signs of agriculture and construction works such as the Great Wall of China, and they might predict that we would go on to develop radio astronomy after a few centuries or millennia, but it would be pointless for them to start signalling us until they obtained positive evidence that we were on the air. This would come when our first radio signals reached them, which will not be for another 400 years. It would then take a further 500 years for their first messages to arrive. So Sagan’s scenario might be conceivable in another millennium or so.

More likely that we pick up a beacon, one designed to sweep the plane of the galaxy, one sending out a civilization’s last wishes, perhaps, or calling attention to anyone who receives it that there are others who have survived their technological infancy. Even so, Davies doubts we would find the brief ping of a beacon amidst the sea of incoming data from our antennae. Better, perhaps, to look for signs of technology like Dyson spheres or other large-scale astroengineering projects which might change the spectral character of a host star.

Even changes confined to a planet’s surface may be detectable in the not-too-distant future in the form of industrial pollutants or other weird molecules in the spectrum of the planet’s atmosphere. The Kepler mission should soon produce a tally of Earth-like extrasolar planets that would be a natural target list for a future space-based optical system with this capability. We must also be alert to the possibility that an alien community might produce very different by-products than humanity – perhaps ultra-energetic neutrinos in the peta-electron-volt (1015 eV) range or intense bursts of gamma-ray photons from matter–antimatter annihilation that would be too concentrated to come from any plausible natural source.

So many questions arise from all of this and Davies works over them all, from extraterrestrial artifacts (and how to discover them if they exist in our own Solar System) to post-biological intelligence and the dangerous trap of anthropocentrism, in which we use our own civilization as a model for what an extraterrestrial culture must be like. Davies wonders whether biological intelligence won’t give way to new kinds of ‘thinking systems,’ artificial intelligence and genetically modified neural networks merging to create a new kind of sentience. Physicist Frank Wilczek calls such a development ‘quintelligence,’ and Davies thinks it might be found in intergalactic space, exploiting low temperatures and all but impossible to spot via SETI.

And what about right here on Earth?

As a final example of what we might look for, an alien expedition or migration wave may have tampered with terrestrial microbiology, perhaps creating its own shadow biosphere to assist with mineral processing, terraforming or energy production. Also, if the aliens really wanted to leave a message for posterity, implanting it in the genomes of micro-organisms might be a better strategy than sending out radio signals from a beacon. Using viruses or living cells as information repositories has many advantages: biological nanosystems are self-replicating and self-repairing, and have the potential to conserve information for millions of years. Some genes, for example, have remained largely unchanged for more than a billion years.

In any case, it’s hard to disagree with Davies’ notion that we now need to widen the search beyond radio and optical methods in the new hunt for astroengineering and technological footprints beyond our own. We’ve come a long way since the 1959 paper in Nature by Giuseppe Cocconi and Philip Morrison that first advocated a systematic search for alien radio signals. Frank Drake’s use of the 26-meter dish at Green Bank (West Virginia) was the start of a hunt that may well occupy us for decades more and perhaps centuries. My guess is that it’s the longest of long-shots, but then I think intelligent life is uncommon in the galaxy. My hope, though, is that we do find it — nothing would please me more than being proven wrong by a solid SETI detection.

This article was originally posted on Centauri Dreams