Star Mummies…

Rameses II - Mummy

How will we adapt to interstellar travel? Rocket Pioneer, Robert Goddard, speculated on interstellar travel back in 1918. He saw two options – if we can release atomic energy then asteroids or small moons could be used as large starships travelling at reasonable speeds. Alternatively, if atomic energy proved impossible, he pondered…

[…]will it be possible to reduce the protoplasm in the human body to the granular state, so that it can withstand the intense cold of interstellar space? It would probably be necessary to dessicate the body, more or less, before this state could be produced. Awakening may have to be done very slowly. It might be necessary to have people evolve, through a number of generations, for this purpose.

In the latter case he suggested solar-boosted hydrogen/oxygen rockets, with interstellar speeds of just ~5-15 km/s. That’s 60,000-20,000 years per light-year. The pilot would need to ‘wake’ occasionally for course corrections – though Goddard had suggested an automatic navigation system back in 1907-1909 using photo-cells, a system used on the “Mariner” probes – so would be re-animated every 10,000 years on trips to nearby stars, and every 1,000,000 years or so, for longer trips.

Goddard had worked on solar-powered ion rockets back in 1909. But he didn’t consider light’s own pressure to push solar-sails. If he had, then the 1,000 year missions to Alpha Centauri suggested by Greg Matloff would’ve seemed a natural improvement over the deca-millennial missions chemical rockets implied.

Of course we know atomic energy can be harnessed – if we so dare. Yet the idea of flying between the stars as mummified cryogenic life-forms has a strange allure. To travel the stars so, we would needs become like human-sized ‘tardigrades’ or ‘brine-shrimp’, both of which can undergo reversible cryptobiosis in a mostly dessicated state. Even if we can’t do so (reversibly – it’s not too difficult to make it permanent), might there not be intelligences “Out There” who have done so? What if we found one of their slow sail-ships? Would it seem like a funerary barge, filled with strange freeze-dried corpses?

Fusion Rockets to Mars… Part 2

John Slough’s Fusion Driven Rocket could reach Mars in 30 days, though for the first missions a more achievable 90 day flight time, and 210 day Round-Trip time, is touted.

Roadmap to a Fusion-Driven Rocket with a 90 day trip from Earth to Mars [pptx slides from Pancotti]

Mission Design Architecture for the Fusion Driven Rocket [paper from 2012 describing the architecture of such a mission]

The Fusion Driven Rocket [NIAC Phase II presentation by Slough, Pancotti & team]

The following diagram illustrates the propulsion system basics:


To achieve fusion, the fusing material needs a rapid input of energy and high density conditions – conflicting demands as the energy wants to drive the materials apart. Such conditions can be achieved briefly by dynamic means – in this case, by imploding metal foils (“liners”) onto a small Field-Reversed Configuration (FRC) ‘plasmoid’ composed of fusion fuel. A plasmoid is a self-shaped structure of plasma (ionised matter is ‘plasma’), which in an FRC pulls itself ever tighter via its own magnetic fields. Thus it naturally drives itself towards high density, until it loses too much energy to radiation and unravels. Before the plasmoid does so, it is compressed by magnetically imploding liners to fusion conditions for long enough to react a significant fraction of the fuel, releasing much more energy than the liners input into the plasmoid. Much more.

For the initial design, as described, the Fusion-Driven Rocket’s ignition system is driven by a solar-array, with no attempt at extracting fusion energy from the plasma stream. Eventually an auxillary power source not restricted to Sunlight will be needed for the Outer Planets, but to get to Mars and the asteroids, a solar array is the least development heavy power-source. The fusion reactions occur once a minute or so, due to the charging time of the compression system, and the current design is very conservative in system components – the solar arrays get 0.2 kW/kg, while the capacitor system stores 1 kJ/kg and so on. Thus a deliberately conservative design based on what we can build now – the only novelty being the fusion engine.

That final NIAC presentation has this rather optimistic development timeline:

FDR RoadMap

…the optimistic point being that it’ll be a “NASA Mars Flight Program” that implements the Fusion-Driven Rocket. I wonder.

Fusion Rockets to Mars… Part 1

While there are perfectly workable concepts for sending humans to Mars by using chemical or nuclear thermal rockets (NTRs), neither option gives spectacular performance. Initial Mass in Low Earth Orbit (IMLEO) is the relevant performance metric and fortunately there’s several quasi-complete designs using both chemical propulsion and NERVA class nuclear thermal propulsion that we can refer to.

First design is Wernher von Braun’s 1969 design, using NERVA class NTRs, which sent a crew of 12 to Mars – and brought them back – in two separate vehicles, landing six on the surface in two 50 ton Mars Excursion Modules (MEMs), all for an IMLEO of 726 tons per vehicle, or 1452 tons total.

Encyclopedia Astronautica: Von Braun Mars Expedition – 1969

Von Braun 1969

The second design, using chemical rockets, was developed by NASA in 1971, with the same crew (6) and MEM (50 tons) as a single Von Braun NTR vehicle. Total IMLEO was 1900 tons.

Encyclopedia Astronautica: NASA Mars Expedition 1971

A more recent design, developed by Robert Parkinson, launched a crew of five towards Mars in three vehicles based on Shuttle-era technology – the European Space Agency’s Spacelab module (which actually flew) and the Orbital Transfer Vehicle (which was studied extensively, but never launched.) Two of the vehicles, Orbiter 1 & 2, massed just over ~210 tons each, while the unmanned Lander Assembly, carrying the MEM, massed 194 tons. Total IMLEO would be 615 tons.

Mars in 1995! (1980-1981)

[Artwork by David Hardy]

I am deliberately avoiding Robert Zubrin’s “Mars Direct” in this discussion, as it requires In Situ Resource Utilization (ISRU) to fuel up the Mars Return Vehicle, thus skewing the comparison. However incorporating ISRU is, in principle, possible for the design I wish to discuss next: the Fusion Driven Rocket.

Fusion Driven Rocket
Fusion Driven Rocket

Revised Habitable Zone… a Revisit.

Ravi Kumar Kopparapu and colleagues [Habitable Zones Around Main-Sequence Stars: New Estimates] have revised the 20-year old work of Kasting, Whitmire and Reynolds [Habitable Zones Around Main-Sequence Stars], with two seemingly minor changes with surprising effects.

Firstly, they’ve extended the range covered by the model to include stars below the 3700 K limit of the previous work, towards the much cooler 2600 K realm of very low mass Red Dwarfs. The very coldest hydrogen-fusing stars are still white-hot – Red Dwarfs drop down to just ~2300 K at the H-fusing limit of 0.08 solar masses, and 2600 K is hit by 0.09 solar mass stars. Secondly, they’ve improved the modeling of the greenhouse effect created by CO2, which has produced some startling changes in results. Earth ends up near the inner edge of the Habitable Zone – instead of 0.95 AU, the inner edge for a Solar-like star is ~0.99 AU and is even further out for redder stars. Ravi has provided a calculator of the effects on his web-site…

Hab Zone Calculator

…the default is the Sun, with an effective Temperature of 5780 K and 1 Solar Luminosity, and an Inner and Outer Edge of the Habitable Zone of 0.9928 and 1.6886 AU. Push the Calculator to 7200 K and the Edges become 0.9451 to 1.5285 AU. Drop the temperature to 2600 K and the range changes to 1.0883 to 2.1238 AU. So what’s going on? Why the changes? The peak radiation frequency of the spectrum is proportional to the effective temperature – hotter stars peak towards the ultraviolet, while cooler stars peak towards the infra-red. Planetary atmospheres are more effective scatterers of higher frequencies than lower frequencies – the cause of the blue daylight sky – and this means under a bluer spectrum, a planet is cooler, or warmer under a redder spectrum.

The Inner Edge is hit when the surface temperature runs away from our temperate ~288 K (15 C) and climbs towards 340 K (67 C), causing a wet stratosphere and eventual dessication of the planet via hydrogen loss. The Outer Edge is reached when no amount of extra carbon dioxide can further increase the surface temperature – adding more just reflects heat away. In fact at 35 bars the CO2 will condense into liquid at 273 K, but becomes opaque at lower pressures before then.

Interestingly if Venus was as far from the Sun as Mars most of its atmosphere (~90 bars CO2, 2 bars N2) would begin condensing rapidly. A turbulent atmosphere, full of convecting plumes, would carry heat away from the hot surface to space… rapidly. In a couple of decades, the place would probably find an equilibrium at something close to CO2’s critical point, about 304 K – just 31 C. An ocean of liquid carbon dioxide about 120 metres deep would form, though much of it would eventually percolate into the regolith creating a very exotic “ground-water”. Ultimately bright CO2 clouds might form and drive the temperatures lower, towards full condensation of the atmosphere…

Induced Torpor for a Trip to Mars?


New idea being funded for Phase I NIAC research, to be undertaken by aerospace firm, SpaceWorks, led by John Bradford. Phase I is for feeling out the next steps in developing the idea to a higher “Technology Readiness Level”, the standard for assessing practicality of concepts that NASA uses. The SpaceWorks NIAC abstract has the following description of the stasis-equipped Mars vehicle:

The habitat is envisioned as a very small, pressurized module that is docked around a central node/airlock permitting direct access to the Mars ascent/descent vehicle and Earth entry capsule by the crew. We believe the crew habitat mass can be reduced to only 5-7 mt (for a crew of 4-6), compared to 20-50 mt currently. The total habitat module volume would be on the order of 20 m3, compared to 200 m3 for most current designs.

The interesting thing about that mass-figure is that SpaceX’s Falcon Heavy should be able to throw a capsule of that mass, with sufficient aeroshell for braking and fuel for landing, to Mars. Such a One-Way ride, with 4-6 months of the interplanetary cruise in torpor, would be for colonists only or for cheap crew transport, if a separate return system is available. Call it the Martian “Sleeper-Car (Coach Class)”. If we got serious about colonizing Mars, then it might be a bargain basement approach used by smaller groups wanting to stake their own claim on the Red Planet. Presently the cost would be ~$200 million, factoring in the cost of developing the torpor system, but with a successful fully-reusable version of the Falcon Heavy’s lower stages (the Mars-Injection Stage would be slung into a “never-to-return” trajectory by just doing its job) the cost might drop significantly. Mass-production would allow thousands to launch to Mars, One-way, for perhaps ~$1 M/person.

Presently Mars isn’t very hospitable, but with sufficient motivation, we could build a thriving colony in one (or more) of the vast lava tubes that have been revealed via orbital cameras. If C/2013 A1 (Siding Spring) were to smash into a Martian Polar Cap, 19 October 2014, then the release of water vapour and carbon dioxide (presently enclathrated in the Cap or frozen in the soil) might induce a shift to a more clement Mars, as I have blogged previously. We might then find the motivation to fly the “Sleeper-Car” to Mars.

Starship Century: My Account

Starship Century – Right here, Right Now

The Starship is still about 100 years away, but we will begin building it this century. This was the message that Gregory Benford and his mirror-twin, James Benford, were proclaiming together, with the help of notables of both science and science fiction. And me. Just how I got involved is another story, suffice it to say, I know a lot about starships, at least about every variety that has ever been seriously proposed.

The choice of venue and the timing were serendipitous – the Arthur C Clarke Foundation and the University of California in San Diego (UCSD) had been working together on the Arthur C Clarke Center for Human Imagination, and the UCSD is the alma mater of a surprising number of modern day Science-Fiction writers. Over the month of May a variety of events were scheduled, notably a conversation between John Lethem and Kim Stanley Robinson on May 14, but the biggest would be the Starship Century. Not coincidentally there is also an associated book, though when I began working on my chapter contribution over a year ago I had no inkling of the event coming up. The details came together quickly, and are a credit to the organisers, especially Sheldon Brown and his team. The event proper was on May 21 & 22, but a UCSD function the night before set the scene, with the Chancellor and Sheldon Brown explaining what the Arthur C Clarke Center was and how it came about. UCSD is the alma mater for a surprising number of contemporary SF writers – not just the Benfords, but also David Brin, Kim Stanley Robinson, Neal Stephenson and many others – so the idea of Arthur C Clarke’s legacy finding a home there seems fitting.

I had arrived in San Diego that afternoon (May 20), after crossing the Pacific with a tail-wind for 12 hours, and had shared a Shuttle bus to the La Jolla Shores Hotel, where the invited speakers were staying, with John Cramer. I had met John briefly at the Orlando 100 Year Starship (100 YrSS), but had corresponded with him on-and-off for some time. He gave me a quick update on his retrocausality experiments (see his Alternate View column for details) and then we arrived. I grew up on Queensland’s Sunshine Coast so seeing the Pacific, but looking West, took a moment of reorientation. Once checked in I needed to stretch my legs so I walked up the nearest street to the local Cafes and shops, only to run into fellow contributor to the book, Ian Crawford – another alien in this strange land of California. We discussed exoplanets and the fate of ocean planets, whether they would dry out or remain drowned, over the aeons. Returning to the Hotel to get dressed I ran into Greg Benford – who briefly I confused with his brother Jim, as he was wearing a tie – and had an inkling I might be slightly over-dressed.

As with 100 YrSS, much of the discussion and interaction happens “off screen”. I spoke to so many people, several of whom told me amazing things, but I then promptly forgot what was on their name-badges. Familiar faces I quickly caught up with, especially Al Jackson, who has a multi-decadal career with NASA going back to the beginning and co-wrote classic papers on interstellar flight through-out the 1970s. Al astounded me by saying he only managed to see one live launch from Cape Canaveral – STS 135 – even though he had worked with many of the Apollo crews in the 1960s. A new face for me was SF writer Allen Steele, whose work I knew of, but hadn’t managed to yet read. A mutual friend, Winchell Chung, has written up much of the technical details of Allen’s novels on his “Atomic Rockets” website, and has also advised Allen on his more recent works. Other new faces, for me, were the poly-math Eric Hughes, who wrote for “Wired” in the hey-days of Cyber-Punk in the early 1990s; Mark Canter, who is a former editor of “Men’s Health” magazine and these days writes SF novels with a more anthropological basis, and John Chalmers, an astrobiologist who has worked with Stanley Miller on the chemical origins of life. The audience of Starship Century was of stellar quality, how much more so the speakers.

Day One, May 21, began with breakfast watching the breakers and discussing interstellar matters with James Benford. Instead of the UCSD Shuttle ride, I had a lift with Jim and Allen Steele as another passenger. Arriving, the puzzle was where to sit. With so many luminaries in attendance, one doesn’t just sit next to Freeman Dyson without introduction. Jim, Greg and Sheldon Brown [video] opened the day officially, and I sat back to listen to Peter Schwartz, [video] renowned Futurist and long term strategist for some very large companies, discuss the scenarios of the future that might get humanity to the stars.

Peter covered three basic scenarios, though many more can be generated. The full details can be found in the “Starship Century” anthology, but in essence three ideologies could launch us to the stars. Firstly, “God’s Galaxy”, which implies a future Earth dominated by religion, sending forth missionaries to the unconverted of the Galaxy. Secondly, “The Dying Earth”, in which we’re seeking a second home, basically the back-story of “Firefly” and countless other SF treatments. Thirdly, “Interstellar Trillionaires”, in which the ultra-rich of a fully developed interplanetary economy launch forth for adventure or curiosity’s sake. Of course, what applies to us, might also apply to other civilizations, with the logical implications for Fermi’s Paradox. Peter’s response to that, was to suggest that “They” might be too sparsely spread in space-and-time for it to yet be an issue.

Next up was Freeman Dyson [video], who has a deserved reputation as a big thinker, as well as at least one near-miss with a Nobel Prize. In interstellar matters, his seminal popular piece “Interstellar Transport” (1968) described one of the few interstellar propulsion systems we could almost build now – nuclear fusion pulse propulsion. What I hadn’t realised was that the testing ground for “Project Orion”, the USAF/NASA nuclear pulse rocket, was in San Diego – of course, the test models only used high-explosives, but the video available of those tests is quite inspiring. Since the heady days of the 1960s, Freeman has argued more for biotechnology playing a role in our interstellar plans. His lecture covered several ideas he has produced over the last 50 years, namely plant-derived habitats that we might grow on the cold bodies of the outer solar system, and the most efficient means of getting between the stars – send information. Eventually, he suggests, we might launch “biosphere seeds” to other star systems and grow new habitats for Earth-derived life as well as ourselves. Naturally this had ethical reactions from the audience as well as the rattling of chains by the Ghost of Fermi – if we can do it Out There, why hasn’t Someone done it here? After the lecture, during a break, I suggested to Ian Crawford that we might not know our biosphere’s genome well enough to tell if such a scenario hasn’t happened here.

If Freeman Dyson created controversy, the next speaker, Robert Zubrin [video], practically invited it by daring to suggest that Greenhouse warming might be preferable to billions of people living in poverty. Zubrin’s talk covered the economic Big Picture of what was needed to create an interstellar capable civilization, but also provided a chance for Robert to vent spleen about more radical environmental ideologues who are promoting what was once called “Nazism”. Naturally he has a book which covers that particular argument, so I will refer the reader to that for more details. On interstellar matters, he made a powerful case that 100 to 200 years of continued development would see humanity ready to set forth to the stars in the first generation of fusion-propelled starships. My one quibble was the “Energy at Retail Prices” fallacy being used to estimate the economic scale of interstellar flight – a 1,000 tonne spaceship moving at 0.1c and using energy at 10% efficiency would cost $125 trillion in energy bought at the retail rate of $0.1/ The problem is that one doesn’t buy energy for a starship and just charge up the batteries. Instead a starship is more like an energy generator – using either solar energy or fusion fuels – and this requires a wholly different economic measurement. The estimates can vary significantly as a result.

Neal Stephenson’s talk [video] was something else again. Not what I expected from an SF writer at all. Instead of Big Picture discussions, he described a vast 20 kilometre Tower that he, and his Arizona State University team, have designed. His talk was thus a detailed look at an advanced theoretical engineering design study in progress. The challenge of such an immense structure, possibly hundreds of millions of tonnes of steel, working in such a changeable environment as the Earth’s atmosphere is fascinating, as is the associated novella in the anthology. But how does it relate to interstellar flight? Naturally the first thing I thought of was as an anchor for a space elevator. Greg Benford suggests another use, in the anthology, but in the current design there is a big empty volume – for future use. A space to fill, for the next generation’s imagination. A reminder, like the Pyramids became, that what one achieves in the present, will look different to the people who come after you.

Lunch at the “Starship Century” Symposium was provided by UCSD, allowing attendees to remain nearby, adding to the discussion and trading of ideas and concerns. Certainly I appreciated the chance to catch up with friends and faces from the other side of the Pacific, as well as meeting new people. Having read people’s novels, books or scientific papers for years, then meeting them on Facebook or email, I felt like I knew some of them already. Meeting authors that I had grown up with like Larry Niven, Joe Haldeman or David Brin was something I was getting used to, as I was more eager to discuss their interstellar ideas than succumb to fan-shock. I finally had my ideas about Larry Niven’s fusion-shield, from his “Known Space” stories, confirmed by the source, but didn’t quite get to talk to David Brin about the Fermi Paradox during the whole event.

The afternoon of the first day was thematically about “New Space” – what we’re doing, as a species, in the near term of a commercial nature. Of course, this was largely from the North American perspective. Patti Grace Smith [video], one of the senior Regulators of “New Space” in Washington DC, spoke about her role in helping commercial space efforts by creating a more operator friendly legal environment. Patti also gave a summary of the key-players in commercial sub-orbital and orbital commercial space efforts, the most prominent being “SpaceX”, while the most secretive has been “Blue Origin”, whom Patti has encouraged to be more open.

Once we’re in orbit the only way is Out – into the wider Solar System. Chemical propulsion isn’t up to the task, so Geoffrey Landis [video] made the argument that Nuclear Thermal Rockets (NTRs) will be the “Workhorse of the Solar System”. Geoff’s presentation was based on material presented previously, to more technical audiences, and the technical reports he referenced are also widely available. So he focussed initially on the long history of the NTR in astronautics – dating back to the late 1940s and almost brought to operational readiness by NASA’s Nuclear Engine for Rocket Vehicle Applications (NERVA) rocket program, before being shelved in the early 1970s. Since then research has focussed on newer materials and newer testing techniques of reactor designs, largely via computer simulation and hot hydrogen gas experiments to simulate the operating environment of engine components. An important point is that NERVA-style NTRs allow transport of humans and their machines in reasonable time-frames all the way to Jupiter. Inside the orbit of Jupiter there exist many sources of the chief NTR propellant – hydrogen – usually in solid form attached to oxygen as water. Conveniently water has many other uses for human beings, thus will be in demand.

That key point lead neatly into the next presenter’s talk [video], Chris Lewicki of “Planetary Resources”, who gave an intriguing overview of the next steps for one of the first “asteroid mining” companies. Chris had clearly covered the material many times before, showing a polish that only comes with practice. The Inner Solar System has abundant energy from the Sun, and convenient chunks of material orbiting in free space in the form of asteroids (and dead comets), but the first task is prospecting and finding the most convenient resources to retrieve from their distant orbits. Thus “Planetary Resources” plan of building small satellites with autonomous control, to minimise ground-control costs, and many of them, to achieve savings via mass-production. Interplanetary prospectors that are cheap enough to crash into an asteroid if that’s what the mission requires. Eventually the quest for precious high-value materials in space to return to Earth, such as the Platinum-Group Metals (PGMs), will also have the side-benefit of producing great volumes of useful in-space materials, such as high-grade iron-nickel metal and water. In time the Inner Solar System could have a viable network of resource trading, with PGMs being dropped back to Earth via “whiffle-balls” of foamed metal, and storage depots of liquid hydrogen for NERVA-style NTRs carrying people to the Moon, Mars and the asteroids.

Panel: The Future of New Space [video]

With those thoughts in mind the day ended with a special presentation and viewing of a small fraction of Arthur C Clarke’s paintings and memorabilia, now at the Geisel Library. Seeing promotional material from “2001: A Space Odyssey”, signed by the actors and similar items made me mindful of the vast legacy that Clarke’s work had inspired. In the nearly 50 years since he began working with Stanley Kubrick on 2001, we have achieved but a tiny part of what the 1960s imagined possible — a reminder of the difficulty of making dreams real.

Intense conversations ate up the hours after the scheduled activities, shadowed by my awareness that I was to be the first speaker on Day Two. My sleep was a broken few hours, an hour at a time, looking at the clock, while my sub-conscious was working on arranging what I would say. Needless to say, I have no idea how the delivery looked [video], as I covered slide-after-slide of starship concepts – most of which are covered in the anthology. One gratifying aspect was being able to point out several starship designers in the audience – Freeman Dyson nodded approvingly when I discussed his Interstellar Orion from 1968, and I covered Al Jackson’s role in the development of the Laser-Powered Ramjet. As a parting note I mentioned the “Ultimate Starship” – my personal suggestion, based on the late Robert Forward’s idea of a neutrino-rocket, to use electroweak unification physics to convert ram-scooped mass directly into a neutrino-jet. One day I will need to write the paper.

Jim Benford [video] covered the concept of Microwave Sail-Ships, giving a fascinating look into his experimental work in the late 1990s, with twin-brother Greg, using carbon-sails in vacuum chambers, made to do amazing things via concentrated beams of polarized microwaves. Jim, like Greg, is a physicist, an alumnus of UCSD, but an applied physicist who has literally written the book on high-power microwave systems, like the million-watt RADAR regularly used by the world’s armed forces. Thus he is well able to discuss the practicalities of propelling sails to interstellar speeds via beams of microwaves and has written several papers covering the economics of micro-wave starships. An elementary conclusion of the Benfords’ experiments is that a conical sail can very effectively ride a polarised microwave beam and be spun so it is self-stabilising. A less encouraging finding is that the cost of energy will dominate interstellar missions at high speeds. Before we can reach the stars we will need to create abundant energy supplies.

Next up was John Cramer [video], a physicist from the University of Washington, well-known to SF fans via his “Alternate View” columns in the “Analog” science fiction magazine, as well as several novels. John focussed on the use of wormholes to allow rapid transit to other star systems. Simply put, wormholes are “tunnels” between two regions in space-time, compatible with Einstein’s equations of General Relativity as one possible mathematical solution. Outside a wormhole itself, observers would see two “ends” of the one space-time structure. Whether wormholes exist or not is a matter for astronomical observation, as larger wormholes should produce distinctive gravitational lensing patterns that astronomers might be lucky enough to see. If the connection formed between the two ends of a wormhole is shorter than the distance through regular space-time, then passing through the wormhole allows apparently faster-than-light travel, though nothing ever exceeds lightspeed locally. Thanks to time-dilation — the slowing of time experienced when approaching lightspeed — a time-lag can be developed between the two ends if one end is sent to a distant star. For example, if a one end is accelerated to a time-dilation of 7,000 (0.99999999c), then only 75 minutes is required for the travelling end to appear to travel 1 light-year from the stationary end’s point-of-view. John Cramer discussed how this might allow a network of rapid-transit wormholes to be set-up throughout the Galaxy – with the caveat that the network can’t be allowed to form a “Closed Time-like Circuit,” else this might destroy the wormholes via amplifying quantum fields.

Before lunch, British astronomer Ian Crawford [video], a fellow member of “Project Icarus”, discussed what we might find amongst the nearer stars, out to 15 light-years. A planetary system probably exists around every star, something we can say with statistical confidence thanks to the work of the “Kepler” exoplanet detection mission, but discerning every planetary system will require improvements on current techniques. And we almost certainly haven’t found every small star within 15 light-years yet, as the 2013 discovery of a brown-dwarf binary at just 6.5 light-years should remind us. Ian made the forceful point that even with vast telescopes able to image those many new planets and stars, there’s only so much we can learn via telescopes. If we find a planet showing all the signs of life, we will only know more by actually going there – via robotic proxy, in Ian’s opinion.

Once we do go, will we survive? This was the after-lunch opener from Paul Davies [video], who posed the puzzling question of how terrestrial life might interact with truly alien life in another star-system. Could they co-exist, with no biochemical compatibility at all? Could they share common simple biochemicals, but foreign genetic and protein chemistry? Or could the two integrate in ways we haven’t yet imagined? Even more intriguingly, Davies suggested that we might already co-exist with “alien” biochemistries on Earth – organisms might exist in niches that otherwise exclude our kind of biology. A suggested location might be at temperatures higher than what known microbes can tolerate, or in highly alkaline fluids, such as what seeps from ocean thermal vents. Davies has suggested, in more than one book, that any life on Mars shares a common ecosystem with Earth, due to the trade in meteorites between the planets over the aeons. Mentioning this sharing of life between planets produced an out-burst from Robert Zubrin, who is an advocate of interstellar transfer of life throughout the Galaxy. A credit to Davies, his response was more interested curiosity than the reflexive dismissal Zubrin seemed to expect. His answer was that we simply don’t know enough to rule out the possibility and they should discuss it more later.

The Benfords encouraged researchers to be present in the audience, with divergent points-of-view. Despite their difference these all share a desire to bridge the space between the stars, but differ in details of how and why we’ll go to the stars. The next speaker unified the many voices by sharing his sense of wonder at the Universe, through a living work of art – Jon Lomberg [video] and his Galaxy Garden. Long-time readers of “Centauri Dreams” will know of Jon Lomberg’s artwork for Carl Sagan’s “Cosmos” in the 1970s and his Galaxy Garden in Hawaii. Having Jon share it with us, a guided-tour in slides, was inspiring and drew multiple rounds of applause from the audience. As Jon put it, we can be Citizens of the Galaxy now.

Two discussion panels concluded the Symposium. The first, chaired by Jill Tarter of the SETI Institute, featured Ian Crawford, Robert Zubrin, Geoffrey Landis, Paul Davies and myself. Our theme was “Getting to the Target Stars” [video] but with Jill as the Chair we wandered into the Search for Others who might have made the same journey. Jill gave a brief summary of false-positive detections of extraterrestrial technology, which have proven to have natural explanations. The sole exception, the distinctive spectroscopic signature of tritium, has no natural explanation – if it is ever detected. With that in mind each of the panellists made suggestions about how we might detect aliens. Robert Zubrin mentioned the distinctive radio output of a starship deploying a magnetic sail, while I suggested the Solar System be searched for dead Starships, since not everyone succeeds in their long voyages. A final task was to sum up how we thought humanity would go to the stars. A common feeling seemed to be via robotic proxies, or nano-bots. In my opinion, by the time we are ready, the distinction between “human” and “robotic” might be meaningless or arbitrary – thus my quip “Nanobots are people, too.”

The final panel was a perspective [video] by the Science Fiction writers, some involved in the “Starship Century” anthology – Joe Haldeman, David Brin, Larry Niven, Vernor Vinge – and Jon Lomberg. This was the artistic side of the event, as all these have produced visions of the starship era. The general feeling was that, given the growth in space industry that Chris Lewicki and Robert Zubrin advocated, then we would see the first star-voyagers depart in about 2200, as Freeman Dyson had extrapolated back in the late 1960s. Some envisioned the unexpected – the discovery of extraterrestrial intelligence near enough to communicate with; breakthroughs in physics that would allow rapid interstellar travel; or, as Allen Steele depicted in his award-winning “Coyote” series, the rise of a tyrant putting a nation or the world on a crash-course program of starship-building. As always, the future will surprise us, but we can prepare ourselves by listening carefully to the modern-day prophets.

Starship Century – Thinking BIG


On Day One Neal Stephenson and his team from Arizona State University presented on an awe-inspiring structure. I’m not sure I’d endorse it as a structure for space-launch, at least not yet, but a 20 km high Tower has a certain gravitas that makes it worthwhile contemplating. Certainly the exercise of designing a mega-structure (even a baby mega-structure like this Tower) will develop computational tools and experience that will help future mega-structure design, some of which will help develop and terraform the Moon, Mars and Beyond.

The mass figures were rather surprising, while the structural material choice was logical, as steel is the most abundant material we make after concrete. One estimate, before it was trimmed back, was about 2 billion tonnes. I sat next to Patti Smith, one of the chief Regulators of Commercial spaceflight, and exchanged comments with her – mostly positive, though my memory is patchy. I quickly estimated that 2 billion tonnes of steel was about 30 years of global production, but my global production figures are probably about 10 years out of date. I have a soft-spot for Colossal Mega-Structures. The automation/teleoperated machinery that building such would require could easily extrapolate to use in space, where multi-kilometre wide structures are regularly discussed. The technological spin-offs of a Space Tower would be profound – but unknowable if we never try to build it, even in detailed virtuality.

Exoplanet News & Novelty

Some interesting exoplanet news bites from around the web.

Think Outside the Box to Find Extraterrestrial Life

Sarah Seager and James Kasting are quasi-interviewed. Seager discusses the Hydrogen Greenhouse planets posited by Eric Gaidos and Raymond Pierrehumbert, while Kasting points out how difficult such worlds would be to observe. Seager also mentions her recent work on Desert Planets and how Venus missed out on becoming a still habitable planet thanks to the Runaway Greenhouse effect. Venus also doesn’t rotate fast enough to allow strong temperature gradients that might allow cooler climates near the planet’s poles.

Eyeball earths

Charles Qoi reports on Daniel Angerhausen and colleagues work on “Eyeball Earths” – planets that are tidally locked to their stars, with one face forever facing the Sun and the other forever facing the black of space. Exactly how such planets might evolve – whether their water would form a vast Ice-Cap on the night-side – is being actively researched.

Under pressure: How the density of exoplanets’ atmospheres weighs on the odds for alien life

Giovanni Vladilo and colleagues examine the effect of atmospheric pressure on a planets habitability. Thin atmospheres tend to result in oceans boiling away more easily than thick ones – thanks to the reduction in boiling point. Water being a super-star greenhouse gas is less likely to cause trouble when there’s more of other gases, like nitrogen or even carbon dioxide. Best to read the paper to get the best idea of their thesis – the URL is given with the diagram:

Overall the current trend in thinking is towards habitability – of at least part of a planet – has a wider zone around the stars than formerly believed. The inner edge might be ~0.5 AU (X4 Earth’s insolation), while the outer edge is 1.7 AU for a CO2 greenhouse, but much, much further out if there’s enough nitrogen or hydrogen to beef it up. All the way out to Saturn if the planet’s lifeforms are driven by sunlight, or all the way out if they can subsist on geothermal energy.

A puzzling question is whether such planets can be called inhabitable by oxygen-breathers like us. Desert Planets, again, have something to say about that – they withstand a Runaway Greenhouse closer in, and avoid the negative feeback of too much snow further out. But over a narrower range than planets with more exotic atmospheres.

Starship Century

Starship Century

May 21, 22 – I will be presenting on Starship Concepts, along with some amazing speakers. Check out the link. Might be hard to be there, so… buy the book!

My talk will cover “Starship Concepts” – in the book I present them in roughly chronological order, but this time I’ll mix it up a bit. Expect Bussard Ramjets, Saenger Photon Rockets, Forward Laser-Sails, Orion, Daedalus, World-ships… and more, more, more…

Terraforming Mars… Very Quickly


Comet C/2013 A1 (Siding Spring) has been discovered to be flying very close to Mars in October 2014… very close. In fact its current orbital error-ellipse has a minimum distance to Mars of 0 – i.e. IMPACT! The error ellipse is large and the current best guess is ~119,000 km from Mars, which is very close to a terrestrial planet for any identified comet in recorded history. Jupiter, of course, has suffered two impacts in the last 20 years and probably several more have been recorded in the past without observers knowing what they had seen.

So what if the comet does impact? Firstly we know the relative speed – a whopping 56 km/s, much faster than the usual asteroid impactors. This packs about 1.568E+9 J/kg in kinetic energy into the mass of the comet. So how big is it? Estimates seem to vary. At first I read the nuclear magnitude to be the nuclear size – normalised to 10.3-10.4 in the current observational figures. Read naively, that means with typical cometary albedo of 0.035, a size of over 60 km. A whopper! However, even at its initial discovery distance of 7.2 AU a comet’s nucleus can be quite active. A spherical coma much bigger than the nucleus can form. The long-time comet observers are estimating that the nucleus is about 4 km wide. Not as humungous as I first thought, but significant if it hit Mars.

So what if it did? At a density of ~1,000 kg/m3 and spherical, then the mass is 33 billion tonnes. Total energy is ~5E+22 J or 12 million Mega-tonnes TNT equivalent. If the comet wasn’t active and we really do see a 60 km monster headed for Mars, then the energy is 3,375 times higher or 42 BILLION Mega-tonnes TNT equivalent. The truth is probably somewhere in between. Assuming the former figure, that’s the equivalent of vapourising about ~20,000 cubic kilometres of ice. The Martian Polar caps total about 3.2 million cubic kilometres, so the smaller estimates won’t affect them much – though enough to be interesting – but the larger estimate would vaporise the lot and then some. The crucial question for Mars, in the long term, is amount of dry ice and liquid carbon dioxide available in the subsurface. All around the planet we see signs of significant amounts of dry-ice in the sub-surface. What if the impact liberated enough to significantly change the planet?

Firstly, how much is needed to give Mars an atmospheric pressure that humans can tolerate, given an oxygen supply, without the need for pressure suits? At the right temperature that can be as low as ~150 mb, or 15 kPa. But let’s assume 300 mb, 30 kPa, the same as the Summit of Everest. Exploring Mars would then be like exploring Everest, rather than the Moon as it is presently. Oxygen would still be needed, but in the right places, plants would be able to grow on the surface and, given time, the planet could be made more habitable. At the bottom of Hellas Planitia – a vast deep depression – the pressure would be ~500 mb, so even more hospitable and open bodies of water could form. Probably akin to the hyper-saline lakes in Antarctica, at its warmest, but on a larger scale.

The surface area of Mars is nearly 145 million km2, or 145 trillion square metres. The surface gravity is 3.711 m/s2 which means 30 kPa pressure requires a column mass of P/g = 8,084 kg per square metre. Over the whole of Mars that’s a total air mass of 1.172 quadrillion tonnes, which sounds immense, but is ~1/3 the mass of the ice-caps. Vaporising CO2 is much easier than vaporising H2O so the energy required to liberate it requires a smaller impactor… though only through directly hitting the source. If a smaller amount is liberated, say 1/10 the goal of 30 kPa, then it might tip Mars out of its current cold climatic state into something warmer. Then we’d see the sub-surface release more CO2 over time (making the surface locally unstable from gas out-bursts) and a self-accelerating warming trend kicks in.

If it’s so easy to remake Mars, then why hasn’t it happened naturally in the past? Perhaps it has. Abundant signs of climate change exist all over the planet – sudden floods of water as ice melts have formed rivers all over the planet. But then the warming ends and the planet chills. The suspicion is that temporary warmings increase trapping of carbon dioxide by dissolving it in water, thus an “Impact Summer” is followed inevitably by the return of the Endless Winter. An Impact Summer might last a few millennia, creating some new erosion, then the glaciers and dry-ice return.

Except, if it happens this time, maybe we – Humanity – can make an Impact Summer last.