Selfies with dinosaurs – the angry birds of the chalk era

I managed to take a selfie with ‘real’ dinosaurs the other week, thanks to some clever SFX. Cool. But in other ways it wasn’t too remarkable – because the latest science says these remarkable creatures, who once dominated the earth and whose chief badass was Tyrannosaurus Rex, are still with us today. We call them ‘chickens’, and usually pressure-cook them in secret herbs and spices.

Alioramus, an early Tyrannosaur. Not huge...but I wouldn't want to meet a hungry one without a Stryker to hand, even so. Click to enlarge.

Alioramus, an early Tyrannosaur. Not huge…but I wouldn’t want to meet a hungry one. Click to enlarge.

That’s right. Birds aren’t ‘descended from’ dinosaurs. They are dinosaurs - specifically, a type of theropod that survived the comet extinction and spread to fill a variety of ecological niches today.

Most of their Cretaceous-era (‘Chalk-era’) relations, such as T-Rex - also a theropod – couldn’t fly. But that didn’t stop most dinosaurs being brightly coloured, feathered (mostly) three-toed, hollow-boned, bipedal egg-layers. Just like birds. And, of course, that means dinosaurs were almost certainly warm-blooded. Like birds. Angry ones. (Go download the app.)

All this was brought home to me a few weeks back when I visited an exhibition about Tyrannosaurs – a long-standing dinosaur family of which T-Rex was one of the last and largest – in Te Papa Tongarewa, New Zealand’s national museum. I’ve already posted about the first part of the experience. The other part was the fabulous high-tech special effects that the museum used to bring their subjects to life.

That included some live action green-screen type SFX, fed back to museum-goers on huge screens - like this one. That’s me on the right, being checked out by my new friend Dino. Cool.

I'm on the right - a selfie I took with my SLR, green-screened and slightly foreshortened (uh.... thanks, guys) with some dinosaurs. Cool!

I’m on the right with SLR to my face in this selfie, green-screened and horribly foreshortened (uh…. thanks, guys) with dinosaurs.

I often walk on the Wellington waterfront. Until now, I'd never met dinosaurs on it... More green-screen fun.

I often walk the Wellington waterfront. Plenty of seabirds to see there, but until now, none of their ancient cousins. More live-action SFX fun in the T-Rex exhibition. I was lucky to take the photo - these things were moving. Note the feather coats and bird feet.

Velociraptor mongoliensis reconstruction, apparently life-size, which is bigger than I'd have thought (most of them were about the side of an annoyed turkey).

Velociraptor mongoliensis, apparently life-size, which at approximately 2 metres snout-to-tail is bigger than I’d have thought. Most of them were about the size of an annoyed turkey. Another hand-held ambient-light photo (note movement blur in the guy behind the display).

The whole exhibition, really, wasn’t about T-Rex. It was about what dinosaurs have become for us; symbols of total badass, which stands slightly against the fact that by the Cretaceous era they were actually feathered, bird-like and really pretty fluffy looking, including the ones that would have eaten you.

All this is a complete turn-about from earlier thinking. Victorian-age scientists looked on dinosaurs as slow, stupid, splay-legged, tail-dragging, cold-blooded lizards, doomed to extinction. The word ‘dinosaur’ remains a perjorative today in some circles for this reason. They were wrong, though in point of fact there HAD been large, splay-legged, exothermic animals in the Permian period (299-251 million years ago). There were two main land animal families at the time – the Synapsids (mammal ancestors), which included the fin-backed Pelycosaurs, like Dimetrodon. And there were the Sauropsids (reptile and dinosaur ancestors). Then came a Great Death, bigger than the one that ended the Cretaceous, that killed 90 percent of all life on the planet in less than 100,000 years. The jury’s out on what caused it, though climate change played a part. All the Synapsids died out, with the exception of a few species such as the Cynodonts, now regarded as mammal ancestors.

Reconstruction of Troodon by Iain James Reed. Via Wikipedia, Creative Commons attribution share-alike 3.0 unported license.

Reconstruction of Troodon by Iain James Reed. Via Wikipedia, Creative Commons attribution share-alike 3.0 unported license.

Dinosaurs came into their own two ages later, the Jurassic – and flourished particularly in the Cretaceous. By this time they were as far from their reptile ancestors as mammals were. Dinosaurs were feathered not for flight, but for display and insulation. They laid eggs in nests. They had hollow (pneumatised) bones. They fell into two types; Orthinischians (bird-hipped), which included the big quadrupedal herbivores; and Saurischichians, lizard-hipped dinosaurs which included the theropods and – paradoxically – therefore birds. Indeed, some of the Cretaceous theropods, like the various species of Troodon, were originally classified as early birds, which they weren’t. But only birds survived the K-T extinction event, 65 million years ago, apparently because they were small.

Did smarts play a part for dinosaurs? Apparently not. They were relentlessly tiny-brained. And the fact that dinosaurs flourished for tens of millions of years, out-stripping the mammals of the day, suggests that – despite our own conceits – intelligence wasn’t required for a survival advantage. But it’s possible they were smarter than we think. Their surviving cousins, today, offer insight. Crows are as pea-brained as all birds. Yet they can solve complex logic puzzles. So maybe dinosaurs had a different sort of intelligence from us.

More on that soon. But for now I’ll leave you with a final look at one of the biggest predators of the dino-era – the magnificent T-Rex, as seen in all good museums… especially one near me, just now. A feathered, hollow-boned, six-tonne carnivore with bird-feet, jaws with the strength of a hydraulic ram – 3000 kg worth of bite – driving home 15-cm long teeth. Speaks for itself, really.

The real thing - Tyrannosaurus Rex, King of the Tyrant Lizards, in all his glory. Another ambient light, hand-held photo of mine.

The real thing – Tyrannosaurus Rex, King of the Tyrant Lizards. Another ambient light, hand-held photo of mine.

Copyright © Matthew Wright 2014

Why this week’s comet landing is way better than celebrity butt-fests

This week’s landing on Comet 67P/Churyumov-Gerasimenko was a landmark in space history – not because the comet apparently bore a passing resemblance to the Kardashian backside that was competing for place in the news, but because surface gravity on 67P is about one millionth Earth’s. You don’t land so much as drift in and try like hell to stay there.

Potential landing sites on the double-lobed Comet 67P/Churyumov-Gerasimenko. Copyright ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Potential landing sites on the double-lobed Comet 67P/Churyumov-Gerasimenko. Copyright ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Add to that the fact that the cometary surface is like a rugged boulder-field and you have a recipe for Ultimate Challenge. That’s what made the landing so risky - and why ESA’s Philae lander was equipped with harpoons, ice-screws, and a down-firing thruster. When they failed, Philae landed on the comet, then bounced a kilometre back into space before the comet’s lazy gravity pulled it back. It was also a funny sort of bounce because the comet isn’t a sphere – it’s more like a dumb-bell. When Philae came down a second time, it bounced again before eventually settling.

For me the three-bounce landing (at 15:34, 17:25 and 17:32 GMT on 12 November) has a wow factor well beyond landing on a comet for the first time e-v-a-h. It’s also about gravity – and that means it’s about Einstein, one of my favourite physicists. Let me explain. Gravity doesn’t just cause celebrity butt-sag, after a while. It’s also why the comet’s where it is today. Fact is that 67P/Churyumov-Gerasimenko experienced a gravitationally-driven orbit change in 1959, when an encounter with Jupiter dropped its perehelion (closest approach to the Sun) from 2.7 to 1.3 astronomical units, giving the comet its current 6.45 year period. That’s why it’s where it is now.

Gravity is also how ESA got the probe to the comet. It was boosted, during a decade-long journey, by gravity assist manoeuvres, swing-bys of Earth and Mars that exploited space-time curvatures around the planets to accelerate the probe (three times) and decelerate it (once), without burning a single gram of fuel.

Ain’t physics neat. So just what is gravity? This looks like a stupid question. Actually, it isn’t.

Rosetta's long odyssey to the comet - with slingshot gravity boosts from Earth and a de-boost from Mars. NASA, public domain.

Rosetta’s long odyssey to the comet – with slingshot gravity boosts from Earth and a de-boost from Mars. NASA, public domain.

The thing is, we think of gravity as a ‘force’. But actually, according to Einstein, it isn’t. We just perceive it as such. Here’s why. Science started looking at gravity in earnest when all-round super-geek Sir Isaac Newton worked out the math for the way gravity presented in everyday terms, which he published as part of his Philosophiæ Naturalis Principia Mathematica in 1687. His gravitational theory worked (and still works) well at everyday level – you could calculate how apples might fall, figure out planetary movements and so on (the key equation is    F = G \frac{m_1 m_2}{r^2}\ , which defines the force between two point-sources of defined mass.) Newton’s triumph came in 1838 when astronomers realised that Uranus wasn’t quite where it should have been, based on the tugs of the known planets. French mathematician Urbain Leverrier and British mathematician John Couch Adams, independently, reverse-engineered the data to pinpoint where an unknown planet should be – and sure enough, there it was. Neptune.

Albert Einstein lecturing in 1921 - after he'd published both the Special and General Theories of Relativity. Public domain, via Wikimedia Commons.

Albert Einstein lecturing in 1921 – after he’d published both the Special and General Theories of Relativity. Public domain, via Wikimedia Commons.

But as science began fielding more data, it became evident that Newton’s equations didn’t account for everything – which is where Albert Einstein comes in. His General Theory of Relativity, published in 1917, is actually a theory of gravity. General Relativity supersedes Newton’s theory and portrays gravity by a totally different paradigm. To Newton, gravity was a force associated with mass. To Einstein, gravity was not a force directly innate to mass, but a product of the distortion of space-time caused by mass/energy, which bent the otherwise straight paths of particles (‘wavicles’), including light.

The proof came in May 1919 when British astronomer Sir Arthur Eddington measured the position of Mercury during a solar eclipse. Mercury’s perehelion – the closest point to the Sun – precessed (moved) in ways Newton couldn’t account for. Einstein could – and the planet turned up at precisely the place general relativity predicted. Voila – general relativity empirically proven for the first time. I don’t expect that Einstein leaped around going ‘woohoo’, but I probably would have. And general relativity has been proven many, many times since, in many different ways – not least through the GPS system, which has to account for it in order to work, because space-time distortion also causes time dilation. (If you want to live longer, relative to people at sea level, live atop a mountain).

Einstein’s key field equation, as it eventually evolved, is G_{\mu\nu}\equiv R_{\mu\nu} - {\textstyle 1 \over 2}R\,g_{\mu\nu} = {8 \pi G \over c^4} T_{\mu\nu}\, - which I am not going to explain other than to point out that it could be used to calculate the space-time distortion caused by the mass of, say, a Kardashian butt. This would be a hideous waste of brain-power, but at least means I’ve managed to put both Einstein’s field equation and a reference to society’s shallow obsession de jour in the same sentence. As an aside, I also think Einstein got things right in more ways than we know. I don’t say this idly.

Philae lander departing the Rosetta probe for its historic rendezvous with the comet. Copyright ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Philae departing the Rosetta probe for its historic rendezvous with the comet. Taken by the orbiter’s OSIRIS camera. Copyright ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

One of the key things about both Newton and Einstein is that their theories treated clumps of particles – a mass such as the Earth for instance – as if the gravity originated in a mathematical point at the centre of the mass, even though the gravity (‘space-time distortion’) is produced by every particle within that mass. And that works perfectly at distance. But in detail an uneven distribution of mass –  a mountain range, for instance, or even a celebrity butt – can introduce local pertubations. Small – but calculable. It’s because of ‘mass concentrations’ that satellites we put around the Moon eventually crash, for instance.

Which brings me back to the science adventure on 67P/Churyumov-Gerasimenko, 28 light-minutes away outside the orbit of Mars. With a long-axis diameter of around 5 km and a composition of loose rocks held together by ices, 67P/Churyumov-Gerasimenko doesn’t have enough mass to bend space-time much. It has, in short, almost no gravity. Orbiting it, as Rosetta has been doing since 6 August, is more like a lazy drift around it. To land is more akin to docking than anything else. There’s not a lot to hold Philae ‘down’, and it doesn’t take much to bounce off. To that we have to add the dumb-bell shape of the comet’s nucleus, which produces complex (if gentle) space-time curvatures, meaning a ‘bounce’ on the comet isn’t going to be a simple parabola like a ‘bounce’ on Earth.

All of which underscores the tremendous technical achievement of the landing – bounces and all. The final lesson? Don’t bother with celebrity butt. Einstein and comets are FAR more interesting.

Copyright © Matthew Wright 2014

Did T-Rex really have feathers and taste of chicken?

Think dinosaurs and the first thing most of us imagine is a large two-legged carnivore with 15-cm teeth, power-shovel jaws and dinky forelimbs. A beast of prey that spent most of the Upper Cretaceous going ‘raaargh’ and having absolutely anything it wanted for breakfast.

Tyrannosaur jaws. Makes Jaws look like Mr Gummy. Photo I took hand-held at 1/25, ISO 1600, f.35. Just saying. Click to enlarge.

Tyrannosaur jaws. Makes the Great White look like Mr Gummy. Photo I took hand-held at 1/25, ISO 1600, f3.5. Just saying. Click to enlarge.

It was thanks to those jaws and 6-metre body that Tyrannosaurus Rex – named such in 1905, over a decade after the first fossils were discovered – was captured by popular imagination well before it became the surprise anti-hero in Jurassic Park.

Never mind the fact that – if we DID meet one, Lost World-style, a bullet or two would turn the hungriest T-Rex into T-Rug. Still, the point that humans are Earth’s all-time apex predator didn’t stop T-Rex speaking to nineteenth and early twentieth century concepts of animal machismo. It was still one of the most dangerous animals to walk this planet. And that made it scary to imagine a meeting. Especially for someone not equipped with a Remington Model 700 BDL. Or running shoes.

Part of the magic came about because Tyrannosaurs died out at the end of the Cretaceous, some 65 million years ago. And that remove in time has given them mythic status. We know them only through bones. Our imagination fills the gaps. And that’s why we keep re-inventing them, even as science and new discoveries, together, unravel an increasingly clear picture of what they were like.

Guanlong Wucaii - an early Tyrannosaur from China. Photo I took hand-held at 1/3 second exposure, ISO 800, f 5.6. I held my breath.

Guanlong Wucaii – an early Tyrannosaur from China. Note the feathery coat. I took this hand-held at 1/3 second exposure, ISO 800, f 5.6. Yes, that’s a third of a second. I held my breath…

Let me explain. To nineteenth and early twentieth century science, dinosaurs were scaly, lumbering, tail-dragging reptiles of which the most ferocious – and certainly the hungriest – was the Tyrannosaurus Rex. That name, ‘King of the tyrant lizards’, said it all.

An 1863 reconstruction of Iguanodon vs Megalosaurus - complete with Iguanodon's thumb-bone wrongly placed as a nose spike. Classic Victorian-age thinking. Public domain, via Wikipedia.

An 1863 reconstruction of Iguanodon vs Megalosaurus – complete with Iguanodon’s thumb-bone wrongly placed as a nose spike. Public domain, via Wikipedia.

The image came out of nineteenth century ideas of ‘progression’ and the ‘tree of life’ (a pre-Darwinian notion) which helped shape popular concepts of evolution as directional ‘advance’ from reptiles to dinosaurs to mammals, each ‘superior’ to the last and thus dooming its dull-witted predecessor to extinction. It was a mind set that took decades to shake – hence the dispute in the 1980s over whether dinosaurs generated internal heat endothermically, like mammals and birds, as asserted by Robert Bakker.

The actual answer, of course, was staring us in the face all along – and Bakker was right, though it wasn’t until the early twenty-first century that enough fossil evidence had been collected to convince the whole scientific community.

Dilong Paradoxus, an early Tyrannosaur. Photo I took hand-held at 1/13, ISO 800, f 5.0.

Dilong paradoxus, an early Tyrannosaur. Photo I took hand-held at 1/13, ISO 800, f 5.0.

We’d known for a while that birds were related to dinosaurs – specifically, theropods, which is the same dinosaur group T-Rex hails from. But the truth didn’t emerge until the early 1990s when increasing numbers of fossils were found in China with clear feather impressions. All, initially, were theropods – the bird ancestors and cousins. But then, earlier this year, a dinosaur species not associated with the bird descent line was found to be also feathered.

Dilong Paradoxus - a reconstructed model. With feathers...

Dilong paradoxus – a reconstructed model. With feathers…

The old idea of dinosaurs as reptiles had already been under fire. And suddenly the truth became obvious. They weren’t reptiles at all. Dinosaurs, like birds, were feathered. Not for flight, mostly, but for insulation – and, doubtless, display. Not only that, but we already knew dinosaurs all had the same skull structure as birds, the same specific skeletal features including pneumatised bones – and half the dinosaurs were, in fact, bird-hipped. They laid eggs in nests. And if it looks like a bird and tastes like a bird… Well, the reality is that birds aren’t descended from dinosaurs. They are dinosaurs. We’ve even discovered the genes inside the chicken genome that atavistically give chickens dino-jaws with teeth, instead of a beak.

The fact that birds are surviving dinosaurs resolves a lot of questions. Want to know how dinosaurs lived? Look out the window at sparrows. Want to know if they were endothermic? Stick a thermometer in a chicken’s – er, well, anyway, you get the idea.

Think Velociraptors were like Jurassic Park? Think again. They were about the size of a large turkey...and looked like this...

Think Velociraptors were like the ones portrayed in Jurassic Park? Think again. They were about the size of a human….and looked like this… And NO, it is NOT going to get its temperature taken, thank you.

As for our King of the Tyrant Lizards? Well, it turns out that T-Rex was among the last of a long family of Tyrannosaurs, not all of which were quite as big and ferocious as the Big Guy. They all had feathers – not for flight, but for insulation. They all laid eggs. They were all bipedal. And their tails didn’t drag – tendons kept them agile. If you met one, you might think it was a funny looking bird. One that wanted you for lunch.

Here's the diorama - Velicoraptor mongoliensis, Dilong paradoxus, and, off to the right - yup, their close relative, Gallus Gallus. A chicken.

Here’s the diorama – Velicoraptor mongoliensis, Dilong paradoxus, and, off to the right – yup, their close relative, Gallus gallus domesticus. You don’t think I’m the ONLY one to make chicken jokes when discussing dinosaurs, do you?

Of course the world of the dinosaurs is long gone – not because they were doomed to be out-evolved, but because their environment changed, literally with a bang. And that comet-driven extinction, 65 million years ago, didn’t just kill dinosaurs. It killed just about everything. Of the dinosaurs, only flying examples – the birds – survived.

All this was brought home for me, graphically and with a lot of special effects, when I went to check out an interactive exhibition in Te Papa Tongarewa, New Zealand’s National Museum. It’s where the first Iguanadon bone ever found is held – it was brought to New Zealand in the 1840s by Walter Mantell, son of the discoverer – and it’s where I took these photos. And if you want to see me personally dodging Tyrannosaurs and see others prancing along the Wellington waterfront – well, I took some photos…

More soon.

Copyright © Matthew Wright 2014

Putting this week’s space tragedies into perspective. It’s ROCKET science, folks

I started writing this post after the Orbital Sciences rocket explosion earlier this week. Unmanned, nothing hurt except pride and stock price. I was going to begin with a joke about how the sound of a rocket blowing up is spelt.

Buzz Aldrin descends to the lunar surface, 20 July 1969, illuminated by light reflecting from the regolith. Photo:NASA.

Rocket science in action. Buzz Aldrin descends to the lunar surface, 20 July 1969. Michael Collins, in his autobiography, Carrying The Fire, figured the mission had a 50/50 chance. Public domain, NASA.

Then news came of the Virgin Galactic tragedy during test flight on Friday, and it didn’t seem right. Appalling news and certainly not something to joke about. In such moments we have first to think of the family, friends, and colleagues of those affected.

To me both accidents underscore the fact that rocket science is – well, rocket science. It’s gained that repute for a reason. We’ve long fantasised about space-flight becoming as routine as jumping into the car. But the laws of physics – particularly, the way the energy curves rise – tell me that reality is otherwise, especially when we think of going into orbit or beyond. While it’s tempting to put the Antares booster failure down to use of left over Soviet moon rocket motors from the 1960s, the fact remains that all rockets, and especially those required to boost something into orbit or beyond, are high-tech engineering that push the limits of materials physics. And complex systems, inevitably, fail in complex ways.

The problem is the energy curve, which is exponential. On the face of it, rockets are simple – so simple that medieval technology could produce them. Something burns in a combustion chamber, hot gases rush out a nozzle at one end and push the rocket in the other, thanks to the Third Law of our friend Sir Isaac Newton.

The penultimate firework - JATO units, seen here thrusting a B-47 into the skies. Public domain, via Wikipedia.

The anti-penultimate firework – JATO units, seen here thrusting a B-47 into the skies in the mid-1950s. Public domain, via Wikipedia.

Unfortunately it doesn’t scale up well. The Royal Arsenal, at Woolwich, was able to make fireworks into battlefield weapons by the turn of the nineteenth century, the ‘Congreves’ fired at Fort McHenry to produce ‘the rockets’ red glare’ of the US national anthem. But powder rockets were limited by chemistry. Other chemical reactions – liquid oxygen and an oil fraction, for instance – offered more energy, and by the first decades of the twentieth century, engineers were working on liquid fuelled rockets.

The problem engineers hit was mass ratio, the difference between the mass of an empty and fuelled rocket. This is everything in rocketry. The equation is R = (Mpt/Me) + 1, where R is the ratio, M is mass in kg, Mpt is propellant mass, and Me is empty rocket mass. It’s important because of the other rocket equation, Δv = Ve*lnR, where Δv is total change-of-velocity capacity, Ve is exhaust velocity and R is mass ratio. Ln is the natural logarithm of X, the exponent to which the transcendental number e (2.7182818…) has to be raised to equal X, which in this equation is R. See what I mean about rocket science? 

OK, enough geek porn. The point being that the lighter the rocket vs fuel mass, at all times, the better off you are. A rocket with half-empty tanks is lugging wasted mass, and that is a killer when it comes to the energy needed to reach orbit.

Atlas booster with Mercury MA-9 atop. NASA, public domain.

Atlas booster with Mercury MA-9. NASA, public domain.

That’s why Convair’s SM-65 Atlas booster, developed from 1951, was an aluminium balloon that dropped two engines on the way up. It’s why the Saturn V Moon rocket had three stages, renewing that mass-ratio every time it dropped an empty stage.

Achieving this wasn’t easy. In theory, a chemical rocket is simple – a tank of fuel (let’s say kerosene), a tank of oxidiser (let’s say liquid oxygen). Pump both into a combustion chamber, ignite them, and off you go. Actually, problems begin at once. Liquid oxygen (LOX) is super-cold – a light blue liquid that boils at 90.19 degrees Kelvin (-297.3 degrees Fahrenheit, -183 degrees Celsius). You have to pump it into the rocket at the last minute, because it’ll boil off fairly soon even in the best-insulated tank. You have to keep LOX away from its fuel (kerosine or liquid hydrogen, typically) until it’s needed. But sealing joints can be difficult. Early seals used Ulmer leather, which LOX tended to saturate and ignite. Today various exotic compounds are used. Duct tape is NOT among them.

Wait, there’s more. Kerosine and oxygen burns at 3670 degrees K – (3396.8 deg C, 6146.3 deg F). Even titanium melts at 1668 deg C. How do you stop your motor melting? One answer is to make a thin double-wall chamber and nozzle and use your LOX (or liquid hydrogen in a LOX/LH rocket) as a coolant, before sending it into the combustion chamber. Of course, you have to get the rate of flow right to make sure your cryo-liquid provides enough cooling – but relate that to the flows needed to burn properly in the motor.

That takes a ton of geekery. And there’s the fact that being super-cooled on one side and super-hot on the other is a Bad Thing in terms of metallurgy, one of many reasons why big rocket motors have reliable firing times, without maintenance, of minutes.

Apollo 12 lifting off. The SIV stage is the one just clear of the tower. Moments after this photo was taken, spacecraft and tower were hit by lightning. Photo: NASA http://www.hq.nasa.gov/ alsj/a12/ ap12-KSC-69PC-672.jpg

Apollo 12 lifting off. Moments after this photo was taken, spacecraft and tower were hit by lightning. Photo: NASA http://www.hq.nasa.gov/ alsj/a12/ ap12-KSC-69PC-672.jpg

That’s without considering pressures. Combustion chamber pressures in the F-1 motor that launched men to the Moon topped 70 megapascals – 1,015 psi, or around 69 times the pressure of the air you and I happily breathe at sea level. That makes ‘thin-walled’ a moot term with the only answer being – you’ve guessed it – more mass, even if you do something mathematically clever with curves and ribs to increase relative thickness.

The next problem is firing. Asymmetric combustion can cause shock waves strong enough to destroy the motor. Rocketdyne made their huge F-1 burn properly – and launch men to the Moon on the back of 750,000+ kg of thrust per motor – with tests that included igniting black powder charges inside the combustion chamber during engine firings.

Since the mid-twentieth century, developments in chemistry have offered ways of building solid fuel rockets that approach liquid-fuel energies without the mechanical complexity. But once lit, they can’t be stopped. That worried Space Shuttle launch controllers, who envisaged chunks of burning SRB crashing through the windows of the Cape control centre if there was an emergency abort-and-fly-back.

F-1 motor firing on test. Public domain, via Wikipedia.

F-1 motor firing on test. Public domain, via Wikipedia.

Wait, there’s even more to rocketry. All the thrust is at the bottom of the stack – like trying to loft a pencil balanced on your finger. One answer is to add gyroscopes (more mass). What about control vanes in the rocket blast, or wings? The former have to stand up to metal-melting blasts. The latter add drag during the initial launch phase and (naturally) mass.

The current approach is to pivot the motors, though this adds mass – and then, how do you instruct that system? Yup – gadgets that add even more mass.

By any measure, the science demands expensive and exotic materials, expensively machined to miniscule tolerances, because the engineering parameters are completely unforgiving. A near-invisible scrap of loose metal in a valve – even an over-tightened screw with a slight burr over which a wire passes and abrades – might be enough to kill a system. That’s why rocketry is so expensive. It’s why I doubt we’ll get ‘gas-and-go’ car reliability for orbital rocket launchers. To do that, we need a different technology.

For me the amazing thing isn’t that rockets fail. It’s that they don’t. Much. They are incredibly complex machines – and they do stuff that, in an everyday sense, is not ordinarily possible. To me that underscores the tremendous skill and work that goes into any launch. Very, very talented people work like Trojans, doing very, very smart things, to make sure. I salute them. They are tweaking the nose of physics, as we currently understand it. And most times, it works.

See why it’s called ‘rocket science’?

Copyright © Matthew Wright 2014

Why New Zealand doesn’t need to worry about a zombie apocalypse

New Zealand has been hit by three significant earthquakes in the last two days. Luckily not strong enough to do damage, and remote enough that even a larger shake would have been more nuisance than apocalypse. But they are a sharp reminder that we live on some very ‘shaky isles’. The next one might well bring tragedy.

The Christ Church Cathedral - icon of a city for nearly 150 years and the raison d;'etre for its founding in 1850. Now a ruin, due to be demolished.

The Christ Church Cathedral – icon of a city for nearly 150 years and the raison d’etre for its founding in 1850. Now a ruin.

It’s to get a better handle on that looming apocalypse that GNS Science have been exploring the Alpine Fault this past few months – drilling far down to set up an early warning system that will give us some prior hint when is about to rupture. Not if, but when – this fault moves every three centuries or so, and it last ruptured in 1717. Go figure.

Well, actually you don’t have to. A study published in 2012 indicated there was a 30 percent chance of a devastating quake occurring on that fault some time in the next 50 years – before 2062. Because probabilities are calculated as bell-shaped curves, this did not mean a quake would occur precisely in 2062; it meant the quake might occur any time from 2012 (low probability) through the mid-twenty-first century (high probability), to the early 2100s (a low chance of it happening that late, but a very high probability of it happening, if it hadn’t happened by then).

This fault is thought capable of generating quakes with magnitude of up to 8.3. Huge. A Civil Defence exercise held in 2013, built around that potential, can best be described as scary. While researching my book on earthquakes, I contacted the author of the exercise – who filled me in on the details. Uh…ouch.

For obvious reasons the science of earthquake engineering is well developed in New Zealand. Some of the world’s leading systems have been invented here, notably the lead-rubber base isolator. This is designed to keep a building ‘floating’ above its foundations. When an earthquake hits, the ground moves – but, thanks largely to its moment of inertia and the reduced energy being transmitted to it, the building doesn’t. Not so much anyway. The first system was installed in the early 1980s in what was then the Ministry of Works building, and major structures to receive it since have included Te Papa Tongarewa, the national museum; and Parliament buildings.

It’s a clever idea. And tricks like this – along with a raft of others – all have to be applied quite seriously in earthquake zones. One of the outcomes, certainly as far as civil defence planning is concerned, is that the likelihood of casualties during the quake is reduced. Buildings constructed with proper attention to earthquake-proofing won’t collapse, and if they’re done right, they also won’t shed parts that crush people beneath. That’s what caused most of the casualties in the 1931 Napier earthquake, for instance, which provoked New Zealand’s first serious earthquake-proofing regulations.

Study, inevitably, is ongoing. But what I can say is that New Zealand doesn’t need to worry about a ‘zombie’ apocalypse. The ‘earthquake’ apocalypse we’re actually facing is serious enough. For more…well, you knew I’d say this – it’s all in my book.

Copyright © Matthew Wright 2014

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Is Comet Siding Spring going to turn our Mars probes into shredded tinfoil?

Shiver in your shoes, Martians! This month – specifically, 19 October at 18:28 Zulu – Comet C/2013 A1 ‘Siding Spring’ makes its closest approach to Mars. The nucleus, a few kilometres in diameter, will come a smidgeon under 120,000km from the red planet.

Mars from the Siding Spring nucleus at closest approach - a picture I made with my trusty Celestia astronomy package.

Mars from the Siding Spring nucleus at closest approach – a picture I made with my trusty Celestia astronomy package.

That’s close. Though not as close as once feared. When the comet was first discovered by Robert H. McNaught in January 2013, using the 20-inch Upssala Schmit telescope at Siding Spring observatory in New South Wales, it was thought likely to hit Mars. It was only later, after multiple observations and cross-checks, that the orbit was refined.

Good news is that this is a tremendous opportunity – and there’s a fleet of orbiting satellites up there for the purpose.  Two, the US MAVEN and India’s Mars Orbit Mission (MOM) – arrived just last week. That puts a lot of instruments in close proximity, and the Indians have plans to use MOM to check for methane on the comet as it brushes past. The Mars Reconnaissance Orbiter will use its HIRISE camera to look at the comet nucleus and activity. Mars Odyssey will check out the coma. MAVEN will make a range of observations with eight different instruments. Even the rovers on the ground, Curiosity and Opportunity, will point their cameras at the sky – Curiosity’s ChemCam, which can pick up the composition; and Opportunity’s PanCam, which will give us a visual from the surface of Mars.

More shenanigans from my Celestia software. This is a view looking from inside the coma towards Mars and the Sun at closest approach.

More shenanigans from my Celestia software. This is a view looking from inside the coma towards Mars and the Sun at closest approach.

Bad news is that this fleet of satellites took years to get up there, cost billions of dollars – and are basically irreplaceable. The nucleus won’t get near Mars. But the coma of dust and debris surrounding it will. Estimates are that during the several hours it takes Mars to pass through the comet’s coma, the planet will be peppered with about five years’ worth of normal meteor activity. It’s all small stuff – nothing more than 1cm diameter, most of them only fractions of a millimetre. But the relative speed is 56 km/sec (200,000 km/h). That’s – uh – impressive. At that speed a 1 gram mass has a kinetic energy of 15,680,000 joules, or 4.35 kwH. In human terms? Enough to run a domestic fan heater on high for a couple of hours. Woah! And that’s just one particle. There are going to be a LOT of particles skidding past Mars.

More Celestia fun; a picture I made of planetary orbits at the moment of Siding Spring's Mars encounter.

More Celestia fun; a picture I made of planetary orbits at the moment of Siding Spring’s Mars encounter.

Precautions have included adjusting orbits so the probes will be on the opposite side of the planet from the comet 100 minutes after closest encounter, when the dust is estimated to reach its highest density. The MRO shifted its orbital parameters to that end on 2 July, while Odyssey did so on 5 August and MAVEN on 9 October. Still, that’s not a complete fix – they’ll travel back around into the danger zone soon enough. Other precautions include pointing the spacecraft so more delicate components are shielded by less crucial elements. And MAVEN will be put into a partial shut-down mode. Once the danger’s past, they’ll restart the science.

By 22 October, according to mission timelines, it’ll all be over. And, if the cometary debris hasn’t shredded them into tinfoil, they’ll be back to their normal work exploring the red planet.

Is Earth in any danger? None whatsoever. Even if we were at closest approach to Mars, the comet wouldn’t affect us – but as it happens, we’re nearly a quarter-turn away from Mars in any case, just at the moment. That’s not the issue – the issue is the several billion dollars worth of science equipment we’ve got around Mars at the moment, its survival – and the science we’ll get from them during this once-in-a-lifetime opportunity.

Copyright © Matthew Wright 2014

Real physics is just weird sometimes. Like, totally.

One of my pet irks as a reader of science fiction is the way some authors play fast and loose with science. Sometimes it works. But usually, for me at least, the suspension of disbelief in SF is carried by the science as well as by story and characters. Goes with this particular genre.But that doesn’t preclude imagination. Physics sometimes gets very weird. Especially where our friend Albert Einstein is involved.

Albert Einstein lecturing in 1921 - after he'd published both the Special and General Theories of Relativity. Public domain, via Wikimedia Commons.

Albert Einstein lecturing in 1921 – after he’d published both the Special and General Theories of Relativity. Public domain, via Wikimedia Commons.

One of his principles was that nothing can travel faster than light. The end. And that’s been proven over and over and over. Of course, this spoils interstellar SF plots, so finding plausible ways around this annoying limit has been a focus for SF authors ever since Einstein came up with it. But very few have explored the weirder consequences of FTL travel.

Try this. Imagine you’ve got the most powerful telescope ever made. You can see spaceships with an instant faster-than-light (FTL) hyperdrive around nearby stars. The drive, using the Principles of Handwavium, allows them to jump from any star system to any other in zero time. That means they are moving way faster than light.

One day, your friends arrive at your house fizzing about their recent FTL journey from Earth to the nearby star 61 Cygni A, then to Proxima Centauri, then home.

Four and a bit years later, you’ve got your friends over for dinner, and your telescope pointed at Proxima Centauri. You see their ship appear around that star.

Seven years and a few weeks later, your friends are again over for dinner. Through the telescope, you see their ship disappear from around 61 Cygni A, departing on its instant journey to Proxima – where you saw them arrive all that time before, from your viewpoint

In short, you can watch your faster-than-light friends departing after they arrived, even though the trip was in normal sequence for them.

How does it work? Well, it’s all relative. 61 Cygni is 11.4 light years away, so light from that star takes that length of time to reach us on Earth. If you watch stuff going on there, from Earth, you’re looking back in time to the tune of 11.4 years.

Proxima Centauri is 4.3 light years away. Same deal for time – 4.3 years.

So what’s happening? The ship moves instantly. But light doesn’t. The light from Proxima, showing the ship arriving there, only takes 4.3 years to reach Earth, so it arrives before light from 61 Cygni showing it departing. And the ship reaches Earth before the light from either star arrives. So from Earth, you see the journey in reverse order.

See what I mean about weird? I’m put in mind of a piece of doggerel which, I’m told, has an unusual provenance of its own:

There once was a woman named Bright
Who could travel much faster than light
She departed one day,
In an Einsteinian way
And returned the previous night.

It’s not something sci-fi writers often consider. But there’s probably a story in it.

Copyright © Matthew Wright 2014