Black Holes, Starships and Antimatter

Some interesting papers by Prof. Louis Crane and his Ph.D student Shawn Westmoreland

Are Black Hole Starships Possible?

…the right answer being “Yes! But they’re really hard to actualise.”

A note on relativistic rocketry

…Shawn refines previous work on just how high an exhaust velocity can be achieved by an antimatter-matter pion-rocket. Previous estimates were surprisingly low – Ulrich Walter computed a mere 0.2084 c, while Robert Frisbee computed ~0.33 c. Westmoreland gets a more hopeful 0.5804 c for a pure pion exhaust, and somewhat higher for basic pion-rocket plus thermalised gamma-rays re-radiated as collimated heat.


Categorical Geometry and the Mathematical Foundations of Quantum General Relativity

…some of Louis’ work on merging Quantum and GR Theories. Hawking radiation is the most relevant result of our best efforts to merge the two and Louis is one hard worker amongst many trying to crack this particular physics puzzle. If he achieves the goal then we’ll have a better idea of how to actualise black-hole star-ships.

Photon-rockets, particularly gamma-ray photons, are inherently high-energy affairs. Raw light requires 300 MW for every measly newton of thrust and Hawking radiation from low-mass black-holes may be the only way we know of converting raw mass into energy on the scale needed. A gamma-ray reflecting material or metamaterial would make the task much easier, but at present such a substance is “unobtainium”.

So what if we did have such? In that case we would need to focus about a million TONS of pure energy into a space small enough to cause it to gravitationally implode into a black-hole. For comparison the Sun puts out about 4.3 million tons of energy per second, but fuses 610 million tons of hydrogen to do so. Not an easy task then if we tried to do so with a super-hydrogen bomb. Coherent gamma-rays are needed, focussed on an infinitesimal target at a gargantuan energy production scale.

Once we have such a black-hole its energies will be of the right frequency to make more black-holes, but of insufficient power. Some kind of “gamma-ray battery” or “capacitor” will be needed to accumulate energy. Enclosing the gammas in a gamma-ray reflecting sphere might do, but the pressure would be unimaginable.

Consider: a photon perfectly reflected off a mirror imparts twice its incident momentum to the mirror. A single kilogram of energy is 90,000 trillion joules, all of which bouncing around would impart ~600 MN of reaction force per bounce on the enclosing volume. Multiply by 1 billion to get our needed energy supply and that’s 6E+17 newtons of reaction for each bounce of the contained photons. Divide by 3 if there’s no directional bias and that gives the average total force experienced by the walls in any direction. The speed of light divided by the linear dimensions of the volume gives the number of bounces per second. Multiply that by 6E+17 N. A mirror ball 3 km across, would experience 100,000 bounces per second, thus the total force is 2E+22 N. A pressure of ~28.3 billion bars.

We’d need some pretty impressively strong stuff to manage that! Of course the outward pressure declines with the inverse cube of the enclosure’s diameter, thus making it a more manageable ~28.3 thousand bars when ~300 km across. Considering the scale of the energies involved that’s manageable!

Is it a Bird? Is it a… Dinosaur?

Archaeopteryx, Archie to his friends & fans, is the world’s most famous ‘transitional fossil’. Until very recently Archie was believed to be a proper bird, definitely on the bird side of the dinosaur/bird transition. Very akin to dinosaurs and other ‘saurians’ – crocodilians, thecodonts, dinosauromorphs, and other diapsids – but definitely a bird. The bony tail, the mouth full of teeth and the lack of specifically ‘birdy’ bits of anatomy should have made people pause to consider a better definition of what makes a bird. Feathers won’t do. Lots of dinosaurs have those, or something like them.

Now Archie has another feature in common with his non-avian dinosaurian kin… slow-growth. Reported here in the New York Times, the latest examination of Archie’s bones indicate it grew at dinosaur pace NOT bird pace. Interesting. So just what makes Archie a bird?

The journal paper the NYT reported on is:

Was Dinosaurian Physiology Inherited by Birds? Reconciling Slow Growth in Archaeopteryx

…available for free from the PLoS.

Archie remains justly famous as a ‘transitional form’ between the other ‘reptiles’ and birds. He’s just not as birdy as we once thought.

A Moistened Moon II

Over at the Planetary Society blog Emily Lakdawalla gives us a more detailed account of just how and what was found on the Moon…

The “Water on the Moon” Hoopla …part 2

…which explains a lot of the current ambiguity in the data. So is there another data point that might help resolve the issue?

The Bone-Dry Moon Might be Damp …discusses research on volcanic glass found in the Apollo moon-rocks and regolith samples. Apparently the glass has 50 ppm water, but lost ~95% during eruption, thus originally had ~750 ppm, which is close to Earth’s mantle value and the high end of the new observations. So the Moon has (some) water. Of course 0.075% doesn’t sound like much, but if all the water in the Moon’s mantle erupted then it really would have seas and a steam atmosphere. For comparison, Earth’s oceans, all 1.35E+9 km3 of them, represent just 0.15% of the Earth’s mantle’s volume and 0.05% of its mass.

Deuterium fusion Starships II

Enzmann Starship

earlier post… Deuterium fusion rockets

Attaching a starship to a great big mass of frozen deuterium seems a good idea, in light of Dr. Friedwardt Winterberg’s updated e-print from June…

Advanced Deuterium Fusion Rocket Propulsion For Manned Deep Space Missions

…of course the trick is igniting the reaction and getting a high fusion-burnup fraction out of the fuel-target. Not so easily done, but Winterberg’s work makes the prospects look good with sufficient effort. The estimated exhaust velocity is fairly high, a bit over ~4% of c, [according to Brian Wang it can go as high as 6.3%] which means a 120,000 ton starship attached to 12,000,000 tons of deuterium can do a delta-vee of ~0.2 c. With an efficient magnetic sail that means the journey speed approaches ~0.2 c, albeit with the mass-penalty of the sail. Perhaps a plasma-magnet can be formed at such speeds, with a quite different decceleration profile to the mag-sail, since the artificial magnetosphere balloons to match the plasma ram-pressure. Essentially the size goes up as the relative speed goes down, thus allowing a more-or-less constant braking force. A decceleration of 0.1 m/s2 will bring the vehicle to a halt in ~19 years over about 1.9 light-years from 0.2 c.

In case you didn’t realise it’s a LONG way between the stars. Fusion-ship trip-times are decadal at best.

PS Even a Vex of 6.3% c, the maximum burn-out velocity is just 0.28 c. While that’s an incredible 84,000 km/s it does still mean that the nearest star, Proxima Centauri, is at least a 15 year trip.

A Girl With Familiar… Feet

Ardipithecus is a hominid species from Ethiopia, discovered in 1994 but only just revealed in her full glory by the team who have laboured for 15 years to pull her bits together to give us a clear image…

Ardipithecus Girl from Scientific American

Credits: Illustrations by J.H. Matternes

…and who does she remind you of? For me those divergent big toes remind me instantly of Oreopithecus bambolii, the putatively bipedal ape from Sardinia & Tuscany, who lived during the Miocene. Marcel Williams has made the case for Oreopithecus being a hominid, if not a direct ancestor, of humans – maybe he’s on to something.

Current Reading

Larry Niven & Eric Lerner “Juggler of Worlds” – sequel to “Fleet of Worlds” in which we see several classic Beowulf Schaeffer stories from Sigmund Ausfaller’s PoV. If you know what I mean then you’ll want to read this one.

Damien Broderick’s “K-Machines” – sequel to “Godplayers” in which we learn more about the latest Player in the Contest of Worlds… and just w.t.f. the Contest is all about.

Just starting on Paul MacAuley’s “The Quiet War” – a Brit-SF writer who I have overlooked while wasting time reading Ken Macleod and Stephen Baxter apparently ;o)

Hobbit may not have been…

Human?

What makes us ‘man’? Aside from gender-specific bits, I mean humanity has some distinct features to its nearest relatives, the Chimpanzees and Gorillas. We talk, make and keep things, and we have this curious need to drape artificial fur over ourselves. We make bargains, we trade and we imagine the Unseen.

But what about the ‘men’ who came before us? What separated them from the other Apes? When did they go from being ‘just an Ape’ to being ‘Super-Ape’ aka Humans?

The co-discoverer of Homo floresiensis, Peter Brown, is now reported to cast doubt on the Hobbits being Homo after all…


Hobbit species may not have been human

…but they weren’t ‘just apes’ either. They made tools, probably used fire, and somehow ‘sailed’ to Flores in the first place. Until c. 300,000 years ago no human species did more than that either – as far as we presently know. Brown’s point, which I agree with, is that Homo floresiensis shares too many characteristics with earlier hominids, like Australopithecus, to be lumped into genus Homo on the basis of tool/fire/raft use alone.

That’s an interesting point. It implies that such technology didn’t evolve just the once. We aren’t as unique as some have suggested as a solution to the Fermi Paradox…

The Mach-Lorentz Thruster

Prof. James Woodward has spent more than a decade working out a Machian theory of inertia which holds the promise of a propellantless space-drive able to turn power directly into motion. Brian Wang, at Next Big Future has covered Paul March’s exposition of Prof. Woodward’s work…

Mach Effect 4: More Mach Effect Answers

…the hoped for efficiency is 1 N thrust per watt of power. That may not happen, but what about more modest thrust/power levels? What if we can get 1 N/kW? Consider the high-powered VASIMR we’ve discussed here, running with 200 MW of power. At top-gear, when it’s exhaust velocity is ~300 km/s, it’s using about 150,000 W for every newton of thrust. An MLT getting 1 N/kW and massing 200 tons, with that power supply would accelerate at ~1 m/s2. Where does that get us? Mars, when it’s at opposition and ~0.5 AU, is just 6.3 days travel away, while Pluto, at it’s aphelion at 50 AU, is but 63 days away. Nine weeks.

What about further goals? The Sun’s gravity-focus is 587 AU away, minimum – just 31 weeks. A small fleet of MLT propelled ships could drop gravity focus telescopes to spy, at high resolution, on all the nearby stars, confirming whether they have planets worth launching probes to. And those probes? Results from Alpha Centauri would be just 18 years away – including the time required to signal back. Results from Tau Ceti would be just 36 years away. In just 100 years we’d be hearing back from stars 42 lightyears away.

AfterLives

Mankind’s first Science-Fiction, tales of visionary quests, let humans tread the pathways of the Immortals, gods and heroes. More recent varieties of SF have often focussed on the not-too-far-off here-and-now, but Big Stories and big themes lure even the hardest of hard SF writers back towards the eschatological and metaphysical. All sorts of “after-lives” have been imagined by SF writers, great and small. Alan Boyle, at his Cosmic Log, has pointed readers to the curious little collection of AfterLife tales by neuroscientist David Eagleman, Sum: 40 Tales From the After Lives. Other After-Life possibilities have been described…

(i) Resurrection as a Cyborg – One of the earliest versions of this SF trope, aside from “Frankenstein”, is a curious set of short stories about a Professor Jameson, by Neil R. Jones, who orbits his coffin in space and is revived by intelligent robots some 40 million years in the future to join them in a series of adventures. “Brain in a Vat” stories have followed ever since.

(ii) Resurrection on another planet – Most famously the late Phillip Jose Farmer‘s Riverworld series, upon which 36 billion people are resurrected via high technology – though no one at first knows this – and struggle to survive-in-style by taking charge of the resurrection machinery. Humans have ‘souls’ called wathans, but these are non-conscious when detached from the body, which has to be reconstructed by mass-creation technology that converts energy into matter.

(iii) Resurrection via Time-Travel – The Light of Other Days, a mind-blowing collaboration by Stephen Baxter and Arthur C. Clarke, uses wormhole-based time-viewers to record the lives and DNA of every person who has ever lived, and every foetus ever miscarried or aborted, and then nanotechnology to ‘resurrect’ them. Fortunately the human race, enhanced by wormhole direct-neural links, has figured out how to move en masse to other planets, to accomodate the resurrectees.

(iv) Souls as particles – Bob Shaw, in his Orbitsville trilogy and several short stories, pondered the possibility that the ‘soul’ might actually be a new kind of particle, a ‘mindon’, created by complex living matter. In the Orbitsville trilogy this idea has cosmological implications that explain much of the mystery of the alien Dyson Spheres.

(v) ‘Soul wave’ – SF is about asking “what if…” and David Brin rather cleverly asks “what if the old Jewish myths of ‘golems’ could be for real?” in his book Kil’n People. Duplicates of living people in clay, animated by a high-tech copy of an individual’s “soul-wave”, have transformed society. One Person can now do the job of a multitude, though with the drawback that one’s ditto only lasts for a short time before turning back into inert clay slop. And what’s the status of a ditto whose flesh-and-blood original has died? Are they legally alive? And where do “soul waves” go after?

(vi) What if “Death” is some kind of predator that only you can see – and avoid? Or the Angel of Death is an alien? Ian Watson poses these conundra in his tale Deathhunter, which is now 28 years old, but still enjoyable, especially the twist at the end. Nothing is as it seems in Watson’s AfterLife.

(vii) End of the World as Gateway to the Other World – which has several variants. On the one hand is the Omega Point scenario, in which the collapsing Universe allows an infinite number of experiences to be experienced in a finite ‘time’. William Shatner (James T. Kirk to “Star Trek” fans) has written a series of novels (“Quest for Tomorrow”) in which the protagonist has a direct line to the Omega Point, who may (or may not) be God. Thus Heaven is in the final fractions of a second – yet infinite in experienced time – of a collapsing Cosmos. Alternatively, the Big Crunch might be hostile to life, and Life might need to escape this Universe to live forever, as in Charles Sheffield’s tale Tomorrow and Tomorrow.
Another variant is the idea of the End of the Earth as a Gateway, which features in Brian Stableford’s The Walking Shadow. A complicated tale, which sees Paul Heisenberg, a professional ideologue, “jump” unexpectedly through time by becoming a silver statue in a kind of time-stasis in front of a whole stadium of people. This causes others to follow suit, ultimately journeying to the end of all life on Earth as-we-know-it billions of years from now, then travelling beyond it after Earth has been taken over by “Third Phase Life”.

More to come…

Anchiornis huxleyi

Dinosaurs and birds were kin, so said Thomas Huxley in the 19th Century. Now a new dino-bird, Anchiornis huxleyi honours his insight and gives us a closer peak at a form between dinosaur and bird…

(from The Guardian)

Dating from before that timeless DinoBird Archaeopteryx, this newcomer is closer to dino than bird. Not all dinosaurs were involved in the origin of birds, mind you, since it was a small twig of the Dinosaur Family-Tree which eventually became birds as we know them today. Most big dinosaur groups – the sauropods, the horned dinosaurs (ceratopsians) and various fleet-footed plant eaters (duckbills and iguanodonts) – had diverged from the meat-eating theropods way, way back in the Triassic, long before the dino-birds took to the air. Yet even the ceratopsians are known to have produced feather quills on their tails, so that particular “birdy” aspect had evolved very early indeed. Some lines of evidence hint the dino-birds came from a warm-blooded common ancestor with the crocodilians, who lost a fully divided four-chambered heart as an adaptation to holding their breath on river-bottoms. Only more fossils will tell us what kind of creature became the crocs, dinosaurs and birds – and maybe even the pterosaurs.

Bristol University’s coverage… Origin of birds confirmed by exceptional new dinosaur fossils
Science News’ coverage… Feather-covered Dinosaur Fossils Found