Dawn, death, and ion drives

Dawn takes off, September 27th 2007 (KSC/NASA)
Dawn takes off, September 27th 2007 (KSC/NASA)

Last week, NASA’s Dawn space probe, which first launched back in 2007, finally ran out of fuel and has been declared dead. Regular readers will know that Dawn has been a great source of information and inspiration for me as I have been creating the future world of Far from the Spaceports, Timing, and the in-progress The Liminal Zone. So it seemed fitting to me to do a kind of tribute to Dawn here.

So here’s a timeline of key events:

  • September 2007 — Launch
  • February 2009 — Mars Gravity Assist
  • July 2011 — Vesta Arrival
  • September 2012 — Vesta Departure
  • March 2015 — Ceres Arrival
  • June 2016 — End of prime mission
  • July 2016 — Start of first extension
  • November 2017 — Start of second extension
  • November 2018 — No remaining fuel: mission ends
Enhanced colour image of Ceres (NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)
Enhanced colour image of Ceres (NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)

Of course, Dawn is not going anywhere – it will remain in its current orbit around Ceres for decades at least, until some combination of inevitable gravitational perturbations distorts that orbit enough that it eventually crashes into the surface. But there will be no more navigation from Dawn, no more course correction, no more photos or science information.

I want to talk a bit about Dawn’s ion drive, in the connection of storytelling, but if you want pictures and information about the mission findings, the best place to start is the NASA site, which has separate pages for Vesta and Ceres.

So, the ion drive. Most craft up to now have used chemical rockets – two or more chemicals are stored separately, then mixed to form a high-energy burst of propulsion. For example, the latest SpaceX SuperDraco engine uses the two liquids nitrogen tetroxide and Monomethylhydrazine. The net effect is that the spacecraft is pushed with high acceleration in a particular direction. After this engine burn, the craft coasts with no further propulsion for days or months, until it’s time for another correction. Astronauts in the craft have to endure short periods of high g-forces, followed by long periods of weightlessness. The engine burns have to be very precisely calculated for direction, force, and duration, so as to minimise the need for subsequent burns. Once the fuel is gone, it’s gone, and each burn takes a fair proportion of the fuel stores.

Falcon Heavy launch, February 6th 2018 (SpaceX via Wikipedia)
Falcon Heavy launch, February 6th 2018 (SpaceX via Wikipedia)

What does this mean for storytelling? Well, most of the journey is spent at zero acceleration, coasting towards your destination without burning fuel, and without any sense of up or down. It took the Apollo astronauts about three days to get from the Earth to the Moon (and the same back again, after doing stuff on the lunar surface). As and when SpaceX or whoever sends another rocket there, it will still take about three days – the time taken is a result of the coasting period without power, not the force of the engine. And because of the long zero-gravity sections, you need to be fairly well-trained to manage this.

SpaceX 'Starman' orbit (SpaceX Twitter feed)
SpaceX ‘Starman’ orbit (SpaceX Twitter feed)

Now consider a trip to Mars. In February of this year, SpaceX launched a Falcon Heavy rocket, with payload of a Tesla car and suitable contents. It left Earth orbit and headed out on an orbit that goes out past Mars, but at a slight angle so that the two never intersect. Each orbit takes 557 days to complete, so at this point not even one has been finished. The payload – a Tesla car – passed by Mars orbit a few days ago, after about eight months.

The Hermes rocket from the film The Martian (http://the-martian.wikia.com)
The Hermes rocket from the film The Martian (http://the-martian.wikia.com)

Now, this rocket had not reserved enough fuel to slow down and enter Mars orbit – it was a vivid proof of concept for SpaceX, not a real attempt to land on the Red Planet. But basically, if a human crew does the same journey in the same rocket, it will take them about eight months to get there – eight months of zero gravity, unless rocket design changes to include a kind of pseudo-gravity produced by rotation, as in the Hermes spacecraft in The Martian.

Getting out into the solar system on chemical rockets just prolongs these figures. Potential astronauts have to cope with months, if not years, of isolation and low gravity. It is just not viable to send people there, which is why the present focus has been on sending hardware and instruments.

Schematic diagram of ion drive (NASA/JPL)
Schematic diagram of ion drive (NASA/JPL)

Enter the ion drive, as used on Dawn and a handful of other craft. It is, in some ways, the opposite of a chemical rocket. It produces small amounts of drive thrust continuously for a very long time. NASA estimates that the thrust of the engines on Dawn is roughly the same as what you feel when you hold a piece of paper on the palm of your hand. It’s quite useless for getting off the Earth’s surface – you really do need something powerful for that – but as a way to get you from Earth to Vesta… or Vesta to Ceres… From a standing start in free space, Dawn would take about four days to go from 0 to 60 mph. But that ion drive just keeps piling on speed. Dawn’s engine ran for a total of about 2000 days during the mission – over 5 years.

Artist's impression, Dawn at Ceres (NASA/JPL)
Artist’s impression, Dawn at Ceres (NASA/JPL)

Now, if you have an engine that is always-on, your whole picture of the solar system changes. Let’s suppose you keep accelerating to the mid point, then flip over and decelerate the rest of the way, so that you get to feel a constant gravity all the way. Then further is more efficient. In twice the time you can go four times the distance. Or, to put the same thing another way, to go twice the distance takes less than one and a half times the time.

Of course, Dawn’s motors were still early versions of the design, with a low thrust output even at maximum. For my stories, I’ve assumed that the design can be enhanced to give an acceleration equivalent to 1/20 of that at Earth’s surface – considerably less than what you get on the moon. It would take some getting used to, but it means that your body and brain have a clear sense of up and down, and all those physiological functions that need gravity have a good chance to keep going! What does this mean for travel time?

  • Earth to Mars takes between ten and twenty days, depending on their relative position at the time of launch
  • Earth to Ceres takes about 3 weeks
  • Earth to Pluto takes about three months
Timing Kindle cover
Timing Kindle cover

That works for storytelling – it’s not very different from journeys that people would take by sail back in the day. For example, an 18th century trip from England to India would take something like four to six months. Once the Suez canal was open, this reduced to about two months. People will put up with a journey like that for all kinds of reasons. So that’s roughly how you can imagine the solar system of my science fiction novels – a bit like our world was in the days of sail and early steam ships.

Here’s a short extract from Timing, in which journey time gets discussed a bit. Meanwhile, RIP Dawn!

Then, quite suddenly, I had been sent all the way to the Jovian system. That would have been fair enough after the local jobs, but it turned out to be a false alarm. One of the analysts thought he had seen a recurrence of an old scam, running out of the Callisto hub. So off we had gone – a long journey for both Slate and I, and when we left Earth orbit the planetary alignment meant there were no friendly stopovers to break the journey.

Once we got there, the two of us had poked around, wormed our way into this module and that, but found nothing. To be sure, we confirmed that the reported irregularities were real. We had easily managed to find the batch runs where the credit had gone missing, by comparing input and output. It happened every time a specific input value was missing or unreadable, and a default value had to be assumed. But the chosen default looked right and we couldn’t find root cause. The code was non-standard, and frustratingly weird, but there was nothing obviously suspicious. The logs were so skimpy as to be almost useless. It did not seem to be the kind of task that needed our skills, nor to be as much of a problem as the analyst had first thought.

When it was over, and having drawn a blank, we sent a summary report down to the Finsbury Circus office, suggesting that perhaps it would be more effective to send an accountant. We had managed to get four weeks out of the work, but it still felt like a long drag for not much return. To be fair, it was unusual for the analysts to make a mistake like that, so I was professionally polite rather than curt. Then it was time to warm up the engines of our sloop, the Harbour Porpoise, and off we set on the homeward leg.

I was all set for a boring journey back down the gravity hill to Earth, but Slate found an orbital option which would take us right past the Scilly Isles. That settled it. We deserved a reward for our fruitless diligence. So we changed the navigation plan, sent some messages ahead, and here we were. Elias, my manager back in London, had made a token protest at the diversion, but I told him that the Harbour Porpoise needed servicing and the delay was unavoidable.

Anyway, a couple of hours signal lag meant that we were already en route by the time his answer came back. We just said that we didn’t have enough reaction mass for such a radical course change. It might even have been true, though I was careful not to ask Slate for a technical analysis, and she was just as careful not to offer one.

Regardless of that, we weren’t minded to listen. Slate and I both reckoned that we deserved the break. Six weeks of voyage out to Callisto, and four weeks of fairly dull work had not made us receptive to a tedious trip straight back home again. It would mean nearly three months’ travel time for just one month of work, and we weren’t about to just put up with that without an argument.

Tesla Starman (SpaceX Twitter feed)
Tesla Starman (SpaceX Twitter feed)

Ultima Thule

Today’s blog is focused on the next target of the New Horizons probe, which back in July 2015 sent back such remarkable pictures of Pluto and Charon. But before that, here’s a quick reminder of this week’s Kindle Countdown deals for Far from the Spaceports and Timing – £0.99 / $0.99 for the next couple of days. Follow these links…

New Horizons route, including Pluto and Ultima Thule (Wiki)
New Horizons route, including Pluto and Ultima Thule (Wiki)

Right. New Horizons. After the Pluto flyby, the natural question was, what next? There was enough fuel and energy reserves to consider a small course change… but to what end? Pluto is at the inside edge of the Kuiper Belt, a tenuous and very sparsely populated volume of space. Over the last few years, we have been steadily gaining information about some of the contents, many of which have hugely elongated orbits. The big prize out there is the possibility of a really sizeable planet, acting as a gravitational shepherd to coax the smaller bodies into resonant patterns.

Planet 9 has not yet been found, but several smaller bodies have. And one of them, catalogue number KBO 2014 MU69 , happened to be well placed for New Horizons. So, an appropriate course change was made as Pluto dwindled into the distance, and KBO 2014 MU69 – now provisionally renamed Ultima Thule – became the next goal.

Current New Horizons view of Ultima Thule (NASA/JHUAPL/SwRI)
Current New Horizons view of Ultima Thule (small dot on right-hand frame) (NASA/JHUAPL/SwRI)

But distances out in the Kuiper Belt are large, so there has been a considerable wait. Ultima Thule is about 12% further away from Earth as Pluto is. The actual flyby will occur on January 1st next year, and at this stage we still don’t really know what to expect. The Hubble telescope orbiting Earth shows Ultima Thule as just a slowly moving point of light. New Horizons is about 33 million miles away from it – about 1/3 the Earth-Sun distance – and still can’t resolve it to more than just a point source. We cannot make out any surface detail. We don’t know if it’s roughly spherical, or irregular, or even a little cluster of fragments all moving together. Just about all we know is that it’s less than 40 km across, and although very dark by the standards we are used to in the inner system, is slightly more reflective than expected.

Artist's impression, New Horizons and Ultima Thule (Steve Gribben/NASA/JHUAPL/SwRI)
Artist’s impression, New Horizons and Ultima Thule (Steve Gribben/NASA/JHUAPL/SwRI)

After sending the Pluto and Charon data home, New Horizons went to sleep for a couple of years, with a wake-up call in June for some of the instruments and a course correction. It is now being prepared as best we can for the encounter. It’s a fascinating problem – light or radio signals take around 6 hours to cross the gulf between us and the probe, so there is no possibility of direct control.  Any reply takes another 6 hours to get back. The systems have to be set up in advance, according to our best guess of what will be there. The final course changes will occur in mid December, when the ground crew wil decide just how close to steer towards Ultima Thule. In one sense, the nearer the better… but the higher the risk that the probe will make brief, catastrophic contact with some fragment of rock and ice. On the day, the probe will whistle by at over 30000 km/h, so there’s no opportunity for second chances. Whatever sequence has been set up in advance, will be played out without modifications. After that, New Horizons will spend the better part of two years streaming the data back to Earth. So although the rendezvous will be a New Year treat, we shall have to wait a long time until we get any high-resolution images or other data.

As yet I haven’t written about what life might be like in a suitably protected environment out in the Kuiper Belt… maybe this encounter will be the seed of another book, in the way that the flyby past Pluto and Charon has contributed to The Liminal Zone. And here, just for a bit of fun, are someone’s first impressions of the settlement on Charon, extracted from the early sections of The Liminal Zone

Nina walked steadily along the winding curves of Lethe towards Asphodel. The house AI had finally told her where Lance’s quarters were situated in Acheron, and had transferred directions onto a hand-held to direct her there. From space, the overall shape of the Charon settlement had been clear – five sinuous linear habitats, following curves in the underlying terrain and joined radially to Asphodel. When you were actually down here, it wasn’t nearly so neatly divided. There were extra little corridors and alcoves which broke up the superficial symmetry, and little tunnels that dived underground and then resurfaced at unexpected places. She was glad that the little hand-held router buzzed faintly at junctions to tell her which way to turn.

Changes… and Kindle Countdown deals

A short post this week, mainly consisting of two extracts, one each from Far from the Spaceports and Timing. These are both on Kindle Countdown deals from this Friday, October 26th, for one week, price set at £0.99 / $0.99 depending which side of the Atlantic you’re on. More of that later… here are the extracts.

The main characters are Mitnash (Mit) and his AI persona partner Slate. in this extract, Mit and Slate are recovering from a difficult episode in which Slate was hacked by a shady individual known as The Wise Man…

Far from the Spaceports (follow this link)

Far from the Spaceports cover
Far from the Spaceports cover

“Slate, how much do I talk to you without knowing it?”
She was amused.
“All the time, Mit. You murmur to yourself while you’re thinking, and you subvocalise throughout the day. There’s very little about your thought life I don’t know. Or your fantasy life. You’re whispering to me almost all the time.”
I sat back, bouncing a little as I forgot to adjust the move for the low gravity.
“It’s nice. I like it. It makes me feel very intimately connected with you. Why? Does it worry you?”
“Not with you, no. If I can’t trust you, I might as well give up now. But I suppose that means you know all sorts of things that I have never told Shayna.”
I considered that soberly, while she was tactfully not replying. It was definitely something to think through on another occasion.
“But anyway, when the hand-held had been compromised, and that other thing was quizzing me, I started to wonder how much I was giving away. Or how much the Wise Man was learning without me knowing.”
“While you were in his quarters, he would have had a direct link from the hand-held into his main system. It was a very old model Ziggurat, like I said before, not very responsive at all. Male gendered, but only just. Badly set up and very poorly programmed. But he has the name Hunn Gravfelt, which at least shows that one of them has read a few decent books. Very arty. But anyway, once you left there, he had no way of querying the hand-held until you got linked up to a ground system. He’s a shady character, but not a very competent one.”
“I suppose the big question is how much information he now has.”
“Yes. But actually, we don’t know for sure what he was able to derive while you were on Agnes. We deliberately left a lot of material out in the open, so he would find it easily enough. We now have to wait and see where that turns up. Like the breadcrumbs in the old children’s stories.”
“But he doesn’t know anything I said on the way home?”
“No. There was a very large data packet all ready to be sent back, but it was never buffered. Do you want to know what was in it?”
I stayed silent and thought about it for a long time, and Slate stayed silent with me.
“Don’t tell me the details. But do run through it again, and tell me if I was about to give away anything critical to the job. Or that might have put Shayna at risk.”
There was a very short pause.
“Nothing like that. If Yul Yulsson was a voyeur, and if he’d ever received it, he could have had some fun with it, for sure. But he would not have learned anything of real value. There’s actually more about me in the packet than Shayna.”
“Hmm. Best not to tell her that, if you don’t mind.”
“This can be our secret.”
I moved to the cabin, pulled out some of the new pieces of clothing which, so far as I could tell, would help me fit in at the Frag Rockers bar a lot better than the formal garb I had worn to see the Wise Man.
“Slate, who’s leading at Frag Rockers tomorrow?”
“A prog rock fusion band called The Descenters. The keyboard player and drummer are locals, from St Martins and Tresco respectively, and the rest are from Ceres. They have a very big fan book on SystemPlus. They’re best known for extremely long concept gigs. They lost their way a bit with Trails on Topological Notions – the twenty-eight minute triangle solo called Geodesics confused even their best fans. But then the electro-gamba player left, and they built up their reputation again.”
“Will I like them?”

Next up, in another book, Mit is discussing a recent shipwreck with his friend Parvati…

Timing (follow this link)

Timing Kindle cover
Timing Kindle cover

I wanted human company again, so I stretched and went in search of Parvati. She was brewing chai as I wandered in to the kitchen. Seeing me, she doubled up the amounts, found a second mug, and arranged some savoury crackers and a red and yellow striped cake on a tray.
“Did you and Slate get anywhere?”
I shook my head.
“Total blank. The figures don’t tell us any more than the basic alert message we got from Finsbury, and they won’t let us access the code yet. There’s almost nothing we can do until we get there.”
We moved back to the bridge and enjoyed the snack together.
“Chandrika just picked up the latest from the wreck site for Selif’s ship, if you’re interested?”
I very definitely was interested. We finished the crackers, and she sliced two generous portions of the cake.
“They’ve made available the results from the data recorders. There’s nothing at all unusual until about three minutes before the crash. At that point, Selif took the vessel’s riding lights offline and uploaded an amendment to the nav plan.”
“Presumably to avoid being identified by the duty porters?”
“Most likely, yes. You’re not supposed to disengage them, but people do. As you say, he was motivated to slip in without attracting attention. It’s also uncommon to amend the plan at that late stage, but it happens. Anyway, the upload was completed successfully, taking only the expected lag. Except that a couple of seconds later, both recording devices ceased gathering data. At the same instant. That is unheard of.”
I looked at her.
“How did that happen?”
“The maintenance log for the recorders showed that Selif had skipped two routine services. So they highlighted that in the report, and almost immediately the manufacturer put out advisory notices basically denying all responsibility if people ignore the recommended schedule. So the official version simply lists an open verdict.”
“Is there an unofficial version?”
She grinned.
“Of course. Chandrika, why don’t you tell them?”
“To be sure. I heard this from one of the personas on Martin’s. He works part-time with a man who’s an expert on the embedded systems in boat engines.”
I nodded. It was a highly specialised area, and one that I knew next to nothing about. But it made sense that a man with those skills would have an opinion on data recorders.
“Well, he said two things. One is that a full restart cycle for those boxes is about half a second longer than the time from the point of failure up until the impact on Teän. And the second thing is that there are only two known exploits for that model of recorder which could bring down both boxes together. One of them cannot possibly have anything to do with this case: a different ship configuration altogether. The other one happens to rely on a routing plan change.”
I sat there, absorbing the news. It made sense that these units would go into an automatic reboot mode if they went dark for some reason. Normally that would restore them to full operation in plenty of time to carry on doing their job. But in this case, the boat had hit Teän before they had started up again. I stirred in my seat, but Slate beat me to it.
“That’s very precise timing on someone’s part. Does anybody think it is just a coincidence?”
“Oh, Slate, the official verdict is open. Nobody is suggesting anything.”
We all laughed together.
“Either it was phenomenally bad luck on their part, or…”
I paused, and Parvati continued.
“Or else someone wanted rid of them, and found a clever way to do it.”

Why the Countdown deals? Well, the last day of October marks the last day of my current job in London. I shall be opening a new phase of working life up in Cumbria. Expect more posts about life up there.

So it seemed fitting to post some extracts, and to discount on Kindle, my science fiction series where coding, AI, and financial fraud in space are the main themes.

But I’m not saying goodbye to that style of writing! As regular readers will know, The Liminal Zone shares a lot in common with those books, though it has a different focus and is set a couple of decades further in the future. And behind that, the third in the Spaceports series is toddling along, tentatively named The Authentication Key at present.

Next week’s post will still be from London, but the one after that will be from Grasmere. And don’t forget… there’s a week of Countdown deal on each of Far from the Spaceports and Timing!

Invasion, migration and assimilation

Cover - 1066 and All That (Goodreads)
Cover – 1066 and All That (Goodreads)

Last weekend, a whole bunch of people, including a number of my online friends, have been remembering and reenacting the events surrounding the Battle of Hastings – 1066 and All That. It so happens that everyone I know who was at Hastings the other day favoured the Saxon side, from which perspective Harold is a fallen hero, who came so close to repelling the invaders in the south as well as the north. But I suppose that a great many of the participants took the Norman side, and so found themselves once again victorious.

In fact, most people I know prefer the Saxons, and harbour a deep-seated wish that things had gone differently. Perhaps this comes from a desire to cheer on the underdog, or from hearing about how viciously the Normans set about securing the land they had claimed (especially in the north). But I suspect it is also because we were brought up on tales of Robin Hood and his Merrie Men, striving as disenfranchised and downtrodden Saxons against their wicked and uncouth Norman overlords.

Hastings reenactment 2016 (Getty images via BBC)
Hastings reenactment 2016 (Getty images via BBC)

I have to admit that, personally, I struggle to see the Saxons as unequivocally the nice guys in our history. My own historical preference is earlier, often swimming in the uncertainty and veiled mystery of times before the written word gave us its particular perspective. And from my view, the Saxons (and Angles, etc) are new arrivals who themselves had claimed a new land by often violent methods. The tales of Arthur and his Companions, stripped of their courtly Medieval topcoat, tell us of a time when British and Welsh leaders tried to protect their homes from wave after wave of incoming aggressors.

Statue King Arthur at Tintagel (Trip Advisor)
Statue King Arthur at Tintagel (Trip Advisor)

Ultimately their stand was a failure – from south to north the Saxons defeated and occupied British land, and the points of resistance were only sandcastles in a rising tide. Perhaps the last to fall was Dunmail, in what we now call Cumbria. As this last king of the British lost his last battle, his last few loyal men took his crown and cast it into Grizedale Tarn, so the new usurper would not have the satisfaction of claiming it. Like Arthur, the promise is that Dunmail will – one day – arise again to claim his crown and kingdom.

Grizedale Tarn from Dollywaggon
Grizedale Tarn from Dollywaggon

So – making what I suspect are controversial statements – I kind of feel that there was something karmic in the events of 1066. The Saxons had arrived and pushed aside the earlier occupants, and now something very similar was happening to them.

Now, arrivals into a country are a curious thing. It’s worth thinking about how we reconstruct what happened. In the past we have had to rely on written perspectives, often put down on paper, papyrus, or clay many years later by the winners or their ancestors. Or we look at archaeological remains, which by their nature can only say so much about their owners. Did the same culture adopt new artefacts quite suddenly? Or did a new culture simply reuse the same things as their predecessors? Nowadays we can have a bit more insight from DNA testing, and the outcome of this has sometimes supported and sometimes challenged prior expectation. More of that later.

DNA map of Great Britain (University of Oxford via The Independent)
DNA map of Great Britain (University of Oxford via The Independent)

There are basically two ways that new arrivals interact with those people already there. Sometimes there is violent displacement of the old by the new. This seems to have happened in Bronze Age Britain, where there is hardly any genetic continuity between the Beaker People and their Neolithic precursors – the great stone monument builders have left almost nothing of their genetics throughout most of Britain. This DNA result rather overturned the prior thinking that the change represented a peaceful transfer of ideas.

Other times the old and new quietly absorb each other and are enriched by the process, playing out on a national or regional level the process of human reproduction, with all its delights and difficulties. Newcomers might arrive for all kinds of reasons, martial or peaceful, but after a few years one finds a fusion of the two emerging – a child of both originals.

A beaker of the Beaker People (Natural HIstory Museum)
A beaker of the Beaker People (Natural HIstory Museum)

Now, at the time of arrival, nobody knows what will happen, and it’s natural for the current inhabitants to fear and deride the incoming hoard. So the Saxons did to the Normans.. so the Britons did to the Saxons… so the Neoliths did to the Beaker People… and no doubt so the Neanderthals did to the Homo Sapiens clans. We still see this played out today, as nationalist politics finds innovative ways to arouse anxiety about “the other”. They’ll take our jobs… they’ll impose their religion… they’re not like us… slogans about “the other” can be found in pretty much every part of our world, fuelled by migrations and flights from war and famine. Personally I remain optimistic, and look for the creative fusion of cultures rather than the catastrophic collision. But looking back at history, it takes effort to find creativity, and we humans don’t always manage it.

Going back to DNA, there are still limitations. We can now – tentatively, and extrapolating from individual cases – identify where intercourse has combined the heredity of two cultures. So we know that the DNA map of Britain correlates pretty well with some historical events, and not with others. We know that pretty much all humans outside Africa have a significant percentage of Neanderthal DNA. We know that a teenage girl’s finger from Siberia shows her to be the child of one Neanderthal parent and one Denisovan parent, some 90,000 years ago. But what we don’t know is the circumstances of the intercourse. Was it a socially sanctioned event, even a personally consenting one? Or was it something darker, the result of forced prostitution or rape? DNA cannot tell us, but that’s the kind of detail we would like in order to uncover the interactions of peoples. It’s one of the great anxieties of mankind – do the newcomers arrive in peace or war?

Siberian cave where the girl's finger was found (Bence Viola/Max Planck Institute for Evolutionary Anthropology)
Siberian cave where the girl’s finger was found (Bence Viola/Max Planck Institute for Evolutionary Anthropology)

Back to life on other planets…

Our solar system - comparison of sixes (BBC)
Our solar system – comparison of sixes (BBC)

It’s a while since I added to my occasional series concerning the exploration of life on other planets, so here are some thoughts about the giant planets in our solar system. Largest of all is Jupiter, followed by Saturn, then Uranus and Neptune. Each of these has a collection of moons, but I’ll deal with them another day. We also know of a number of exoplanets of this size circling other stars – big planets being easier to detect than smaller ones, other things being equal – but that’ll be the subject for another day.

These large gas giants are characterised by hugely deep atmospheres, in which the pressure rapidly builds to intolerable levels as you drop down through it. It is unclear whether there is a hard surface at any point, or whether the gases of the upper layers simply get progressively denser and more viscous with depth. With no obstructions to stop them, wind currents circle the planet and stir up giant storms that can last for decades. It is not an obvious place for life to thrive.

Spacehounds of IPC - cover (Goodreads)
Spacehounds of IPC – cover (Goodreads)

Science fiction writers have, nevertheless, speculated about life here. Some authors simply ignore what we know (or were writing at a time when much less was known), while others try to weave their stories alongside the facts as we understand them. Typical of the first is EE (Doc) Smith, who was never shy of hypothesising life anywhere, and took great delight in speculating how environmental pressures would shape an alien race’s outlook on life, as well as their physiology. He placed several races on gas giants, including Jupiter. Such races, in his view, would be not only squat and strong – to cope with the gravity – but arrogant and condescending towards the weaklings of other worlds. A large part of Spacehounds of IPC deals with a long-running war between the hexans and the Vorkuls, inhabiting two opposing cities and fighting an impeccable war against each other. The Earthlings help resolve the fight by siding with the more morally upright side – they have little enough in common with either, but the hexans turn out to be unacceptably vicious and ruthless.

The Algebraist - cover (Goodreads)
The Algebraist – cover (Goodreads)

Iain M Banks, on the other hand, tried to take a more nuanced view. A couple of his books – including The Algebraist, for example – present life on gas giants as essentially floating, by analogy with oceanic creatures here on Earth. Different kinds of life coexist at different levels of the multi-layered atmosphere. Some of these interact, for better or worse, and others never meet.

Current scientific thinking is less optimistic about life of these giant planets, preferring to think about their moons. That’s a subject for another day. But there was a fascinating piece of analysis I read recently, trying to tackle the question of whether denizens of the gas giants would develop space travel. Basically, the rocket problem is that of managing your fuel. You need a certain amount of fuel to send your object of interest – the payload – up from the surface to orbit. But the payload has a protective casing, which you don’t need in orbit but which weighs something. Then there’s the fuel you’ll burn, and the container holding it… and these also weigh something. So you need more fuel to push up all that lot… and so on. Think back to how small the Apollo moon landers were compared to the entire Saturn V launch system.

The most fuel-efficient way to accomplish this is to have booster stages that are used in the early part of the flight, and then detached when empty to reduce weight for the next stage. Until the advent of reusable vessels like the Space Shuttle, and more recently Elon Musk’s launch vehicles that return to a soft landing, all of these lower stages were single-shot throwaway items. Now, that’s a problem for us here, but in turns out to be a much bigger problem if you are starting from a larger planet. Even one twice Earth’s mass would present difficulties, and Jupiter has about 300 times the mass. Musk’s Falcon Heavy rocket can place about 50 tons of payload into low earth orbit. Taking off from Jupiter, the same rocket could only get 40 kilograms into space. Would a race of beings living on one of these gas giants – even supposing they wanted to look through dense layers of cloud to see what was outside and spark their curiosity – have the resources to embark on space exploration?

One of Cassini's last images of Saturn (NASA/JPL)
One of Cassini’s last images of Saturn (NASA/JPL)

Weather – away from Earth

Last week I talked about weather on Earth, both in fact and fiction. This week, suitably enough, it’s time to think about the other planets in our solar system. And there’s plenty to talk about.

Dust storm front, northern latitudes of Mars (ESA Mars Express)
Dust storm front, northern latitudes of Mars (ESA Mars Express)

The obvious first place to start is Mars – the atmosphere is thin there (ground level on Mars is about the same as 30 km altitude here, high above the Himalayan peaks), but it’s well able to have weather patterns. There are seasonal changes, with the polar ice caps (frozen CO2, or dry ice, rather than water ice) growing and shrinking as the planet tilts one pole or the other towards the sun. Then there are erratic changes, such as dust storms which can build up over a substantial area. The Martian opened with one such storm, and the book version had a second which threatened Mark Watney’s journey towards rescue (the film skipped over this one). In the real world, back in the summer, one such storm of vast proportions cut off communication between NASA’s Opportunity rover and mission control. The problem here is not actually caused by fierce winds buffering the craft, but that the dust has blocked its ability to capture sunlight and so generate electricity (the exact problem Watney faced late on in The Martian).

Storm on Saturn seen by Cassini probe, 2010 (NASA)
Storm on Saturn seen by Cassini probe, 2010 (NASA)

Venus has ferociously fierce winds, and if ever we try to build a permanent settlement on the surface there (which personally I doubt, since orbital or high atmospheric bases would probably suffice) then they will need immensely strong anchors, and extraordinary resistance to high levels of heat and acidity. There are outline plans at present for building a lander able to survive for a few months, rather than the few hours which is all that has been achieved to date. Jupiter and Saturn have no discernible surface – probably one exists, but the pressure would be intolerable well before you reached it. They also have huge storms spreading thousands of miles across.

Artist's impression, dust storm on Titan (PGP/Labex UnivEarthS/University Paris Diderot – C. Epitalon & S. Rodriguez)
Artist’s impression, dust storm on Titan (PGP/Labex UnivEarthS/University Paris Diderot – C. Epitalon & S. Rodriguez)

But several of the moons of the giant planets are more promising. Recently, dust storms were spotted on Saturn’s moon Titan… not sand as might be on Earth or Mars, but great clouds of organic hydrocarbon molecules are stirred up into its atmosphere. So there’s definitely weather on Titan, and pretty much everywhere else we look.

Moons like Titan have been known to have atmospheres for some time, but as well as this, our solar system contains a lot of small bodies which used to be thought of as entirely airless. Closer investigation has shown that many of these actually have very thin layers of air around them. In some cases these are probably generated by underground deposits of liquid and gas which slowly ooze to the surface and evaporate. In others, we don’t yet know how they came into being. But these discoveries are reshaping how we think of our sibling worlds, and by extension the worlds we are spotting around other stars.

New Horizons image of clouds on Pluto (NASA/JPL)
New Horizons image of clouds on Pluto (NASA/JPL)

Back in 1950, EE (Doc) Smith, in First Lensman, could describe Pluto as being rocky and entirely barren. We couldn’t say that any more, not after the New Horizons probe sent back this fantastic image of air and clouds above Pluto. In Liminal Zone, my protagonists on Pluto’s moon Charon witness such changes both outside the dome where they live, and also when they look up at Pluto. Weather, it seems, is pretty universal, and will go on forming a topic of conversation for a lot of years to come.

And in a final stop-press, the existence of a new dwarf planet has just been announced. The finders were actually looking for the enigmatic Planet Nine, whose existence is suspected from a variety of gravitational anomalies in the orbits of other far-out objects. That has still not been detected, but instead they found 2015 TG387, dubbed The Goblin for simplicity. This newly recognised member of our solar system has a fantastically elongated orbit. At closest approach it is still well outside the orbit of Pluto, and at aphelion it strays 35 times as far away. It takes around 40,000 years to complete an orbit: last time it was in its present position we were sharing much of the planet with Neanderthals.

Orbit of 2015 TG387 (Roberto Molar Candanosa and Scott Sheppard, courtesy of Carnegie Institution for Science)
Orbit of 2015 TG387 (Roberto Molar Candanosa and Scott Sheppard, courtesy of Carnegie Institution for Science)

Weather – here on Earth

"Alexa, open Cumbria Weather"
“Alexa, open Cumbria Weather”

I thought I’d blog about weather today, firstly because it often matters when writing about the past, and secondly as a kind of shameless advert for my most recent Alexa skill. Let’s get that out of the way first – it’s called Cumbrian Weather, and it requests a short-range forecast from the Mountain Weather Information Service. Why not just use the built-in weather service on Alexa? Well, MWIS focus on weather insofar as it impacts outdoor pursuits such as walking, cycling, rock-climbing and so on. So the forecast includes essential things like whether the peaks are covered in cloud, what the temperature is at 750m, what height you reach freezing point as you climb up, and the like. All of which interest me, so I have accessed this data-feed and present it through Alexa. Like all my Alexa skills to date, it is entirely free to enable and use.

Rough weather on Bryher, Isles of Scilly
Rough weather on Bryher, Isles of Scilly

Which brings me nicely to the impact of weather on historical fiction. You get macro-level events that shape the whole story, such as drought, floods, a long winter, and so on. These are often used to set the scene, or the tone, for a book. Storms at sea are a staple of maritime fiction, and are a handy device for placing characters in unforeseen circumstances.

But in daily life as well as fiction, it’s also the smaller scale events that can derail the best intentions. And the nature of these events varies hugely with location. In London, where I am writing this, then the impact is often seen on transport – the famous autumnal “leaves on the track” problem which no doubt will be affecting commuters before long. A century or so ago, pollution and fog could easily combine to produce an unpleasant, unhealthy, and all-but-impenetrable smog.

Puma Mountain rescue helicopter practicing in low cloud near Fairfield
Puma Mountain rescue helicopter practicing in low cloud near Fairfield

Up in Cumbria, a night’s rain in the wrong place can end with localised floods. Storm Desmond, back in the winter of 2015, left major roads unusable, and washed away several bridges, quite apart from the impact on houses and shops. That aside, you can have a run of several days when even low peaks and ridges are invisible because of low cloud, frustrating work and movement between valleys. The various mountain rescue teams are regularly called out to succour people who have been caught by surprise up a height, and are completely unprepared for a weather change.

These more rapid, more local shifts and switches are every bit as important to fictional characters, as their real life equivalents are to us. Naturally, the particular kinds of weather change that matter to people vary from place to place – one location may have low cloud and mist, another one sudden blizzards, and a third sandstorms. It’s as well to find out what your characters might have to contend with!

Next week I’ll be having a quick look at weather on other planets. Not yet an everyday topic for most of us, but potentially it will be in a few years.

Meanwhile, here’s another quick reminder of Cumbrian Weather… available now in the UK Alexa store, and to appear soon in other stores world-wide.

Amazon Dot - Active
Amazon Dot – Active

A first extract from Quarry

I’ve made occasional comments about a prehistoric novel I am planning, set in what we now call Cumbria, and tentatively called Quarry at this stage, Well, I had thought that this was only at a very early planning stage, and that I wouldn’t start actually writing anything until The Liminal Zone was done and dusted – and possibly The Authentication Key (=Far from the Spaceports vol 3) as well. (For any readers waiting for those two books, fear not… they are definitely in progress…)

But as things turned out, Quarry has been nagging at me until I put something down, so here is an extract. It is probably from very near the start, if not the actual opening. Bonus points to anyone who can not only identify the high ground mentioned, but also the tarn… (tree cover in the period in question was much more extensive than now)


Quarry image
Quarry image

Bran woke, all at once as the unfamiliar sun kissed his eyes. He had bedded down the previous evening at the edge of a stand of short trees, all bursting into greenleaf. A broad swathe of grass ran down to a round pool.

The clouds had lowered as he reached the mere, and he had read that as a sign to stop. Not that the sign meant much, as cloud and springtime mist had walked beside him from the moment, two days ago, when he had started to climb up from the broad valley into the hills. The stones of a gathering circle, straddling the place where five ways crossed, had swum out of fog as he neared them, and he had turned half-left and stumbled along the ancient ridge track, anxiously placing his feet where so many others had walked, until the next cairn appeared. And the next, and the next, until he was weary of half-seen forms, and chilled by the wind and the droplets of water that clung to wool and leather, hair and skin.

The mist had stayed with him through all of that day and the next, veiling the peaks and ridges on either side. When he finally stood in the travellers’ place at Pen-y-lugh, the long lake it stood on was shrouded, the east and west shores soon fading to shapeless bands of darker grey. The townspeople, seeing the set of tools at his belt, and the tattoo of the stone-workers clan, had directed him up a gentle track. He had left the settlement again, and worked an easy way around the side of a crumpled hill.

Now there was morning sun, and a still air that left not a ripple on the circle of water in front of him. His shadow fell across it as he stood, and the trees opposite – oak and birch, hazel and holly – stood upright on the heels of their own reflections. He looked down at their length stretched out in the water, and saw below all of them an arc of grey rock, speckled with white.

He looked up again, eyes tracing the trunks and the leaves, until he was looking at the real spur instead of the reflected one. It was his first sight of the place where he would work. From here, it was a two-headed beast. A long curved ridgeback ended in those proud upraised horns. Perhaps it had once settled from the skies onto the valley wall, its fiery ardour slowly solidifying into crag and rock. Or perhaps it had welled up from the world below, forming these shapes as it contended with the outward air. Now it was cold and hard, and the snow of winter still streaked its spine and flanks.

He leaned back against the rowan tree which had sheltered him last night, and gazed, filling himself with that first sight. Somewhere below those outcrops, he supposed, his dwelling-place was waiting, though it was hidden from him by all the forest between. But his task, day after day, would be to clamber up between the beast’s paws, to find and follow its congealed veins as they wound their precious way back into the stone body. There he would tease out the best of the unformed teardrops of rock, and shape them into gifts. Gifts for war or gifts for love: each one would be a thing of beauty drawn out from the mountain.

A squirrel chattered nearby, and a family of wagtails began to dabble along the water’s edge. It was time to go; it was time to finish his journey to the quarry.


Red dwarf stars, and life away from Earth

After a few weeks in which I have been thinking about ancient Cumbria, this week I’m back in space again. In particular, this post looks at some possible locations for alien life which, until recently, were considered most unlikely. Over the last few years, thousands of planets have been identified by equipment both on Earth’s surface and in orbit. We now know that planets are exceedingly common in the galaxy, and that on average, each star has more than one planet. There are more planets near us than stars. Many of these are large in size, gas giants like our own Jupiter and Saturn – larger planets are obviously easier to detect than smaller ones – but a great many are small and rocky, more like Earth.

Artist's impression - the seven planets of TRAPPIST-1 (ESO)
Artist’s impression – the seven planets of TRAPPIST-1 (ESO)

The most extreme case we know of is designated TRAPPIST-1 (the acronym originating from the Chilean telescope which first detected them). This has seven planets, so the system is broadly like our own. And a very recent analysis suggests that each of them has liquid water at its surface, and in some cases considerably more water than we enjoy here. If we were to travel the forty light years to get there, we might well find a world which is entirely ocean.

But as well as the striking nature of the planetary system, the sun itself is interesting. Up until fairly recently, the search for life elsewhere was focused on stars which were as similar to our sun as possible. It was assumed that this was necessary in order for the associated planets would be like Earth. But TRAPPIST-1 is not at all like our sun – it is a comparatively cool red dwarf star. Red dwarfs are extremely common in space, but they are small and dim, and until modern orbital telescopes revealed the true situation, were thought to be rare.

Comparison of solar system sizes (ESO)
Comparison of solar system sizes (ESO)

Now, red dwarf stars are much cooler than our sun, between 1/3 and 2/3 of the effective temperature, so for a planet to be in the Goldilocks Zone – neither too hot nor too cold – it must be much closer to its sun. But that’s OK – in the TRAPPIST-1 system, all seven planets orbit well within the distance that super-hot Mercury circles our sun. Indeed, that system is not much larger than that of the moons of Jupiter. Red dwarfs are miserly with their energy, so you have to huddle in close to the fire to get any warmth. But along with that, they burn at their low rate for a hugely longer time than our sun will last. The hotter and brighter the star, the less time it shines for. Too short a stellar lifetime, and their might not be time for life to develop on whatever planets are around. Red dwarfs give their planets massive amounts of time to develop.

Right now we have absolutely no idea whether any of the TRAPPIST-1 planets supports life – or indeed any of the myriad other red dwarfs and their planets in our quadrant of the galaxy. But if you were a betting person, you’d be more likely to bet on life arising around a red dwarf than a super-hot star like Sirius.

Artist's impression, Ross-128b (ESO)
Artist’s impression, Ross-128b (ESO)

Now, 40 light years is inconveniently far away from Earth for exploration in reality or fiction. Our current generation of telescopes can find out a decent amount of information about the 7 planets of circling TRAPPIST-1, but not nearly as much as one would like. And if you consider near-future science fiction, without warp drives, wormholes, or other exotic ways to travel around space -as I do – then 40 light years is well beyond a realistic journey time. Happily, there are other red dwarfs much closer to us. One of these, which has been studied with great excitement for a few years now, is called Ross 128 (the rather boring name coming from a catalogue number). It has at least one planet (Ross 128-b) which appears to be a little larger and more massive than our Earth, and some calculations suggest that its surface temperature may well be around 21C. Ross 128 is only about 11 light years from Earth, so is getting towards the we-might-send-something-there territory.

I thought about using Ross 128 as the focus of interest in my in-progress novel The Liminal Zone, but in the end pitched for the even-closer Gliese 411 – another catalogue name, which for fictional purposes has been rebranded something more interesting. Gliese 411 is under 9 light years away, and is the 4th-closest star system to us. The planet Gliese 411b is, so far as we can tell, larger than Earth, and almost certainly rather hotter, but (probably) not so hot as to preclude interesting things there. And its proximity to us makes it a credible target for the Breakthrough Starshot project, in which tiny “spacecraft” with roughly the capability of a mobile phone are boosted towards their target by a laser beam shining against a light-catching sail. The miniature spaceships are called Sprites, and last year were tested for their ability to communicate from space after being launched from Earth. Each is just a few centimetres square, weighs just 4 grams, and costs a few tens of dollars. The entire actual cost of the mission is in the devices needed to boost these Sprites to their final speed.

Starshot’s current plans are for Proxima Centauri as target – the nearest star to us, a little over 4 light years away – and a boost to 1/5 light speed. Proxima Centauri is in fact another red dwarf star, and a very recent theoretical study suggests its planet may have a large ocean and survivable temperatures… though so far we lack real observations which might confirm or refute this, and other studies have suggested that the radiation levels are uncomfortably high for life to thrive.

My fictional version is a little more ambitious – Gliese 411 and 1/2 light speed. A journey time of about 17 years, plus the time taken for the homeward bound signal on arrival, means about a 25 year lag from lift-off to analysis of results. It’s still a long time, but less so than some space projects – it is now over 41 years since the two Voyager spacecraft left Earth, and we are still following them. A very recent theoretical study

As to what happens in The Liminal Zone once these little ships get there – well, it’s still work in progress, but hopefully you’ll get a chance to see for yourself early next year!

The Liminal Zone (temporary cover)
The Liminal Zone (temporary cover)

High Street, ancient trackways, and Romans

Ullswater, looking roughly south-west towards Helvellyn
Ullswater, looking roughly south-west towards Helvellyn

As well as Boot and the Hardknott Pass, which I’ve been talking about the last couple of weeks, I spent a fair amount of time around Ullswater while in Cumbria. It’s the second longest of the lakes (after Windermere) and has often been claimed to be the most aesthetically pleasing. For example, Wainwright called it, “that loveliest of lakes, curving gracefully into the far distance“. Be that as it may, it certainly has a wealth of natural beauty and historical interest. But the fact that at many points around its shores, the hills encroach very steeply, means that it is only thinly settled, and parts of it are quite difficult to approach except on foot or by using one of the several launches that go to and fro.

Helvellyn against the skyline
Helvellyn against the skyline

The particular part I want to focus on runs down the eastern side of the lake. It is another part of the Cumbrian network of ancient trackways – later adopted by the Romans for their own purposes. This one is now called High Street, running by the hill of that name a little further south, and ultimately connects to Ambleside… and hence Hardknott, Boot, and the coast.

The Cockpit, looking roughly south
The Cockpit, looking roughly south

My starting point, after some gentle approach climbing up from the lake, was at an ancient stone circle called The Cockpit. Nobody knows the original name, or indeed the original purpose. It probably dates from the Bronze Age, could be up to about 5000 years old and is one component of a large collection of ancient sites on Moor Divock. Whenever and whyever it was built, it lay then as now on a crossroads. A roughly north-south route from Penrith to Ambleside crosses a roughly east-west route coming across from Castlerigg (near Keswick) to the Eden Valley and Shap. The much later Romans would be making similar journeys, though they were more interested in their settlement near Cockermouth than in looking at the Castlerigg stone circle. And nowadays casual explorers like me go there.

Milepost marker
Milepost marker

So from The Cockpit you head south – like Burnmoor near Boot, the current terrain is wild and slightly boggy, but back in the days of prehistoric occupation it was rather more pleasant. There’s a long steady climb up towards Loadpot Hill, but well before you get there you can see many of lakeland’s most dramatic peaks in the distance – Blencathra, Skiddaw, the whole length of the Helvellyn ridge, and then Fairfield and others heading south. You also regularly see other signs of human occupation, from other prehistoric arrangements of stones through Roman mileposts, to a very few much more recent (and ruined) dwellings. The track itself stretches out in front of you, and there’s a real sense of walking in the footsteps of a whole throng of ancestors. You really could walk on through the Kirkstone Pass and down to the shores of Windermere, provided you were equipped for the journey.

(Former) Roman altar, old St Martin's church
(Former) Roman altar, old St Martin’s church

I didn’t do that, but turned off the ridge into Martindale, where one last historical treat awaits. The current old church of St Martin’s dates from Elizabethan times, but a church has been there since the Middle Ages. The font – which has been used there for some 500 years – was originally a Roman altar, retrieved by some enterprising villagers from somewhere along High Street. In the graveyard is an ancient yew, which some believe is among the oldest living trees in England and could be up to 1300 years old. That would probably predate the first appearance of Christianity here, and would mean that, like the Roman altar, it had once been involved in very different expressions of spirituality.

All in all a great walk, and one to revisit at some stage. And, of course, all good raw material to stir into the (pre)historical novel Quarry which is slowly coming together in my mind.

The ancient ways...
The ancient ways…
...and the ravens overhead
…and the ravens overhead

Writing, both historical and speculative