With an ocean containing twice as much water as Earth’s oceans, Europa is a high-priority target for astrobiology. But the presence of water alone is not what gives the Jovian moon such interest. After all, we’re learning that icy worlds beyond the snowline can feature oceans beneath the surface, and we’re learning more all the time about oceans all the way into the Kuiper Belt, as the ongoing investigation into what lies beneath Pluto continues.
But Europa, like Enceladus, offers us substantial water in direct contact with a rocky seafloor, and that’s a telling circumstance. What excites astrobiologists is water in the presence of the organic compounds that can become components of biology. The third factor is energy, which Europa has in abundance thanks to the tidal pull of Jupiter, causing flexing of the seafloor that may well be driving hydrothermal activity. Chemical compounds produced from interactions with Jupiter’s magnetic field may also be useful as an energy source.
In June of 2016, NASA’s Planetary Science Division began an early study into a Europa lander. Having a lander here is an exciting thought because study of Europa’s surface shows the periodic breakthrough of oceanic materials that then re-freeze, icy plates that spread apart during this process and so-called ‘chaos’ terrain that may contain frozen material from the interior. A lander here could tell us much about what lies under Europa’s frozen crust.
Image: Enhanced-color image mosaic from Galileo showing crosscutting lineae, multiple wide, dark bands where the surface has spread apart (right), and chaos regions (left) where the surface has been disrupted into blocks of material. Image is approximately 200 km wide. Solar illumination is from the upper left. Credit: Figure 1.1 of the SDT report.
The Europa lander work is in its infancy. This is a Science Definition Team report that, as this JPL news release explains, is a routine part of any mission, used to work out the feasibility and scientific value of the concept. The team’s report, involving 21 scientists, was submitted to NASA on February 7. Its goals: To characterize the surface and subsurface of the Jovian moon, supporting future robotic exploration; to assess the habitability of the moon by analyzing its surface; and — the primary goal — to search for evidence of life.
We haven’t developed a full-blown life detection strategy since the days of the Viking landers on Mars, so it’s heartening to see the emergence of a document that makes recommendations on the scientific instruments required and analyzes the systems needed for landing here. We need to get a payload onto the surface without benefit of heat shields or parachutes, given the lack of an atmosphere, and it’s hard to see how this could be done with missions like the current multiple flyby mission scheduled for launch in the 2020s.
That mission is separate from the concept lander now being considered, but it gives food for thought. Flybys, of which the former mission includes at least 45, will be profoundly useful in imaging the moon’s surface at high resolution and investigating its composition. But multiple high-speed flybys make it challenging to slow a lander for safe arrival on the surface. The lander report, therefore, takes a different route, using gravity assists within the Jovian system — at Callisto and Ganymede — to reduce velocity relative to Europa. From the report:
The first Europa gravity assist would mark the beginning of the final mission phase before landing, and the spacecraft would now be exposed to much higher daily radiation doses than before. The first Europa gravity assist would be designed to insert the spacecraft into a Europa-resonant orbit, and ΔV-leveraging maneuvers would further reduce the spacecraft’s velocity relative to Europa (Campagnola and Russell, 2010). This velocity reduction would make the low-energy (or three-body) regime accessible to the spacecraft, in which the gravitational interplay of Europa and Jupiter would enable the carrier to reside in the vicinity of Europa for the full duration of the surface mission. This final part of the tour trajectory, from first Europa flyby to landing, would take approximately one month and would set up the lander delivery to a 5 km periapsis altitude at a target state relative to the landing site.
Image: Example tour trajectory showing a Jupiter arrival and transition to Europa. Credit: Figure 10.5 of the SDT report.
After that, we have deorbit and landing, as pictured below.
Image: Deorbit, descent and landing sequence showing the final stages before touchdown on Europa’s surface. Credit: Figure 10.6 from the SDT report.
This is tricky business, using tethers to lower the lander from the descent stage in a ‘sky crane’ configuration before touchdown, with the descent stage impacting at a safe distance from the lander:
Prior to touchdown, the lander stabilizers would be deployed. As the lander is set onto the terrain, the stabilizer legs would contract as needed to both maintain contact with the ground and enable the lander body to remain flat. Contact of the lander body with the surface would trigger release of the bridle. The stabilizers would then be locked in position to yield a stable lander configuration for science operations.
The Europa lander report will be discussed at two upcoming meetings designed to get feedback from the scientific community. The first, on March 19, occurs at the 2017 Lunar and Planetary Science Conference in Texas. The second, on April 23, will take place at the Astrobiology Science Conference (AbSciCon) in Arizona. As early in the game as this is, The Europa Lander Study 2016 Report (JPL D-97667) makes for absorbing reading, and I recommend downloading and reading it on a tablet for convenience.
Gaining a human foothold on another world — Mars is the obvious first case, but we can assume there will be others — will require a search for resources to support the young colony. In today’s essay, Ioannis Kokkinidis looks at our needs in terms of agriculture, whether on a planetary surface or a space-borne vessel like an O’Neill colony or a worldship. Happily, his first reference, to Lucian of Samosata, has deep science fiction roots. The author of several Centauri Dreams posts including Agriculture on Other Worlds, Ioannis graduated with a Master of Science in Agricultural Engineering from the Department of Natural Resources Management and Agricultural Engineering of the Agricultural University of Athens. He holds a Mastère Spécialisé Systèmes d’informations localisées pour l’aménagement des territoires (SILAT) from AgroParisTech and AgroMontpellier and a PhD in Geospatial and Environmental Analysis from Virginia Tech. He now lives in Fresno CA and works for local government, while continuing to pursue his interest in sustaining human life outside our own planet.
By Ioannis Kokkinidis
Introduction
About noon, when the island was no longer in sight, a whirlwind suddenly arose, spun the boat about, raised her into the air about three hundred furlongs and did not let her down into the sea again; but while she was hung up aloft a wind struck her sails and drove her ahead with bellying canvas. For seven days and seven nights we sailed the air, and on the eighth day we saw a great country in it, resembling an island, bright and round and shining with a great light. Running in there and anchoring, we went ashore, and on investigating found that the land was inhabited and cultivated. By day nothing was in sight from the place, but as night came on we began to see many other islands hard by, some larger, some smaller, and they were like fire in colour. We also saw another country below, with cities in it and rivers and seas and forests and mountains. This we inferred to be our own world. We determined to go still further inland, but we met what they call the Vulture Dragoons, and were arrested. These are men riding on large vultures and using the birds for horses. The vultures are large and for the most part have three heads: you can judge of their size from the fact that the mast of a large merchantman is not so long or so thick as the smallest of the quills they have. The Vulture Dragoons are commissioned to fly about the country and bring before the king any stranger they may find, so of course they arrested us and brought us before him. When he had looked us over and drawn his conclusions from our clothes, he said: “Then you are Greeks, are you, strangers?” and when we assented, “Well, how did you get here, with so much air to cross?”
— Lucian (ca. 125-180 AD), True Story, chapters 9-11 translated by A. M. Harmon (1913).
Lucian of Samosata’s most famous work, True Story, defies easy categorization. He most likely wrote it as a parody of the travel novels popular during the Antonine Era and more specifically Antonius Diogenes’ now lost The Wonders Beyond Thule. Modern critics have called it the first surviving work of both Science Fiction and Fantasy, and ironically it is the only work of both genres that is part of the school curriculum in Greece today.
We can see that already from the earliest work of science fiction space colonization, war and agriculture are important themes. Alas, unlike Lucian’s description, who like Herodotus implores us to go and travel to the places he just described to see for ourselves that he is telling the truth, neither the Sun, nor our Moon nor Venus have an Earth-like biosphere. The use of technology, though, can allow us to produce agricultural products necessary for human survival on other celestial bodies, provided that these bodies can provide in easily available form the resources that agriculture needs. This article at first describes in general terms what sort of resources agriculture can provide, and then lists the important elements and their forms necessary for an artificial ecology to function.
When designing planetary colonization we should take note that the biosphere of Earth provides resources and ecosystem services to people through large scale cycles that are hard to replicate. It is very hard, though, to create a completely enclosed system; resource inputs of several forms will be necessary in order to maintain a system that can sustain human civilization. On Earth cultivated plants assimilate carbon from the atmosphere during the growing season, which is then released back in the short term after the end of the growing season and in the long term through the geologic carbon cycle. Until a colony reaches a very large size, which it might never reach, we will most likely try to maintain our crops in a permanent growing season, planting a crop as soon as the previous is harvested, which in turn would mean that we need to be constantly adding resources instead of allowing them to be slowly released by decomposition.
Furthermore even if we do reach a balance of agricultural inputs and outputs in our artificial ecosystem, it will likely still require a large buffer, far larger than what is being cycled every year. For example if we only use agriculture to grow food and we grow our food exclusively from plants, we only consume a small part of a plant, less than 50% of aboveground biomass for annual crops and an even smaller part of tree crops. It is simply not possible to plan to colonize a body that does not contain in significant quantities easily available elements that we need, unless we set up large scale resource transfer from outside it. I believe that I am not the first person to raise the issues below, though I have not done a systematic search in the literature. All suggestions are welcome.
Image: A fictionalized portrait of Lucian taken from a seventeenth century engraving by William Faithorne (1616-1691). Credit: Wikimedia Commons.
Resources from agriculture
Food
Food, sustenance in all forms for the colonists, is the most readily available reason given to engage in agriculture in space. Any food grown is food that does not need to be transported from Earth, not to mention that there are a variety of psychological benefits from seeing it grow. We can divide edible crops into two categories, autotrophic organisms such as plants and heterotrophic organisms such as fungi and animals. Over the last 10 millennia we have domesticated a huge number of plants of which we eat a very wide variety of plant parts but rarely the entire plant. With heterotrophic organisms we can take advantage of the non-human edible parts of a plant and convert it into edible sources, though again we do not eat entire animals, except perhaps octopuses and their relatives. There is no such thing as the perfect diet for all conditions; we need to balance the macro and micronutrient needs of humans with the available resources and the need to maintain a healthy population. Also since plants produce their edible parts on an irregular basis we also need to store and preserve food, especially to guard against crop failure.
Fiber
Usually when we talk about plants providing food and fiber, by fiber we often mean wood fiber. While we will likely see trees planted in arboretums, we are not likely to see forest style plantations for harvesting timber; colony space is too valuable and tree growth rate is too slow. Unless we can find a celestial body with forests, wood furniture will likely remain a luxury item reserved for the well off or for very specific uses where it is indispensable. Another use of wood fiber for which we will need a ready substitute is paper, it being much easier to produce paper than a factory making electronics. There is already on the market tree free paper made from bagasse, a byproduct of sugarcane processing, and several other plant waste fibers. Historically, before the invention of paper by the Chinese and its introduction by the Arabs in the 11th century to Europe, papyrus and vellum were the writing material, although it is highly unlikely that we will see vellum used in a non-ceremonial setting in space.
Moving on to other fiber uses, the most obvious one is for cloth making. Cotton fiber is the most popular of the vegetable fibers used, though other plant fibers are also used, such as flax, jute and hemp. Among animal fibers wool is the most popular, though silk and leather are also fine choices. On earth biologically derived fibers are today more expensive than petroleum derived fibers such as polyester. In practice, with the exception of Titan, celestial bodies are not known to harbor large bodies of hydrocarbons from which we can derive artificial fibers. The specific planting of crops and the selection of animals to be used in space will depend on the needs of the colony and the related infrastructure such as cotton gins that are needed to produce usable materials.
Biofuel
Before the industrial revolution most materials used for energy purposes were derived from the active biosphere, e.g. firewood. Today fossil fuels, biogenic in nature, mostly cover the energy needs of human civilization. There has been effort, though, to produce biofuels to substitute for fossil fuels since the oil crises of the 1970s. In Europe, which does not have large petroleum resources, coal has long been mined, and biofuels are subsidized by the Common Agricultural Policy. The purpose is not so much to cover energy needs with European resources but to keep farm prices from dropping too low and thus creating unhappy farmers that block the highways demanding better prices. In the US corn biofuel policy is more related to the political cycle, such as the first in the country Iowa caucus and its voters; after all the US is one of the largest petroleum producers in the world. The most successful bioenergy program in the world is considered to be that of Brazil, blending sugarcane derived ethanol into gasoline and thus abolishing the need for importing oil (Brazil is an oil producing country).
The use of biofuel in space is tied to the selection of the energy cycle for the colony. It is highly unlikely that we will use internal combustion engines to power a colony. Most likely energy sources will be either photovoltaics, which in the long term will require a plant to produce them out of silicon wafers, or nuclear, which requires an entire cycle of mining, refining and isotope enrichment. It is possible that we will see hydrocarbons as energy sources in the colony. Already there are plans to use abiotic processes to produce methane as rocket and rover fuel in future Mars colonies, and there it is possible to produce RP-1 from biological sources if a rocket is to require it. In general, though, I see biofuels occupying a niche source in a future colony. We might create biodiesel out of waste edible oils but we are unlikely to see entire sunflower plantations intended for biodiesel production.
Bioplastics
According to Wikipedia there are over 300,000 tons of bioplastics produced each year, or 0.1% of the total global plastics production worldwide. Modern technological civilization is very dependent on a variety of plastics, even inside a greenhouse (e.g. drippers). Unless the celestial body colonized has prodigious amounts of easily available hydrocarbons available such as Titan, we will need to create very early an infrastructure to produce bioplastics for colony needs or else set up a logistic chain for plastics from Earth. Generally for bioplastics the feedstock is readily available plant material, such as cellulose or dextrose, though some animal sources such as casein (a milk protein) have been used. The harder part will be creating a production line for these bioplastics from the local raw material.
Elements for agriculture
What follows is a list of major elements that are necessary for plant growth. Some 17 elements are necessary for plants to survive, though the majority are required in minute amounts often easily available in the soil or as impurities in the fertilizers. Carbon, Hydrogen and Oxygen combined are responsible for 95% of plant mass. Often, though, due to pH element deficiencies can arise despite the presence of the element in the soil.
Carbon
Carbon enters the biosphere when it is assimilated by plants through photosynthesis in the form of CO2. While there are a few methanotrophic bacteria known, it is unlikely that we will require carbon in any form except CO2 for agriculture. Plants can oxidize CO in the presence of O2 to CO2, but cannot use raw carbon. Thus if carbon is available in the environment but not in the form of CO2, we will likely need to set up processes to produce CO2 before plants can assimilate it.
Hydrogen
Plants assimilate hydrogen mostly in the form of water. Water has an important function in plants both as the solvent of biology but also as the stream that allows the transport of elements inside the plant.
Oxygen
Oxygen as an element is assimilated by plants in the form of water and CO2. It is released to the environment in molecular form by photosynthesis, which is critical for the survival of animal life. Plants also use molecular oxygen from the environment during respiration, however they produce far more O2 than they consume, and this allows heterotrophic life to exist.
Image: The colors in the spectra show dips, the size of which reveal the amount of these elements in the atmosphere of a star. The human body on the left uses the same color coding to evoke the important role these elements play in different parts of our bodies, from oxygen in our lungs to phosphorous in our bones (although in reality all elements are found all across the body). In the background is an artist’s impression of the Galaxy, with cyan dots to show the APOGEE measurements of the oxygen abundance in different stars; brighter dots indicate higher oxygen abundance. Credit: Dana Berry/SkyWorks Digital Inc.; SDSS collaboration.
Nitrogen
Plants require this element in a variety of forms but unlike the previous three they cannot assimilate it from the atmosphere. Rather they take it through the roots, more specifically through the soil solution in the form of nitrate. Nitrates, though, are highly mobile in the soil, which is why we also fertilize with ammonia, which is converted to nitrate by soil microorganisms over time. Both forms of nitrogen are typically produced in chemical factories on Earth using atmospheric nitrogen as a feedstock. In parts of the outer solar system they are available as rocks and ices.
Phosphorus
Phosphorus is another element that is assimilated from the soil solution. Unlike nitrogen, though, it is not found in the earth’s atmosphere, rather we mine phosphate rocks and fertilize with phosphate salts. Some 80% of global phosphate mining exploits deposits of biogenic sedimentary rocks of marine origin. The other 20% is of igneous origin in the form of apatite. Outside earth it is this phosphoric apatite that will likely provide our phosphorus needs
Potassium
Just as with phosphorus, potassium is mostly mined from sedimentary rocks, more specifically evaporites. While evaporites have been found on Mars and are likely present on Venus, for other bodies of the solar system we will need to locate other forms of the element and process it into the salts that plants require.
Iron
Iron has an intermediate position between micro and macronutrients, required in quantities that are small for macronutirents but large for micronutrients. Plants assimilate iron in ferrous (Fe++) form, often from organic iron complexes that contain ferric (Fe+++) form with the expenditure of energy by the plant. Since the concentration and availability of ferrous and ferric iron depend on the soil pH and other ion antagonists in the solution, very often we see plants with iron deficiency despite a large iron concentration in the soil and the parent rock. In hydroponic fertilization and urgent deficiency interventions we tend to use organic iron so as to provide a highly available form to the plants. Organic iron, though, is not necessary if we take pains to control the pH and antagonists such as calcium, phosphorus and carbonates.
Calcium
Calcium is a micronutrient, not necessary in large quantities for agriculture. However it is often applied in macronutrient quantities in order to control soil pH. In areas of high rainfall such as the eastern US and western Greece we will find many soils that are calciferous in origin but have a low pH, because rainfall washes the Ca++ ions, lowering the pH to acid levels. Calcium is used in hydroponics to raise solution pH and it is likely necessary to stockpile and use calcium for this purpose rather than for the specific need of the plant for this element.
Sulfur
Sulfur is the opposite of Calcium in that it is used to lower soil pH. There is no shortage of sulfur concentration in agricultural soils on Earth; fossil fuel use has spread it far and wide. Pollution control measures have reduced atmospheric deposition in developed countries and it is likely that in a few decades sulfur fertilization will be necessary in some areas. So far, though, we are more likely to see sulfur in hydroponics, raising pH when it falls too low. Just as with calcium, plants do not require large quantities, but we may need to stockpile it for the same reasons.
Other micronutrients
The rest of the elements necessary are required in minute quantities and while pH is very important for their availability, their limited requirements mean that we will not need to seek them specifically. In general, micronutrient fertilization can become necessary and critical if we choose an agricultural system where we remove the entirety of the plant mass from the soil or substrate and do not allow any plant decomposition to take place, which is what we will do at first. The decomposing remains of the previous harvest are often the primary source of micronutrients for the next, even in intensive agriculture. If we remove the entirety of the crop each time, we will need to provide the elements that were mined in the process, though again, it is unlikely that we will need to search for extensive quantities.
Conclusion
This contribution was inspired by news reports of the first NASA Mars landing site selection symposium. They mentioned that along with geologists seeking interesting formations there were also colonization specialists arguing to select sites with mineral resources for metallurgy in the future colony. They did not mention plant specialists looking for areas having resources to grow plants. I did not write this contribution with Mars specifically in mind; it is intended as a general guide for all celestial bodies. Bodies with carbon dioxide in the atmosphere will not require creating it from other elements. Bodies with nitrate rocks are advantageous to those with only gaseous nitrogen in the atmosphere.
Also, while we are fortunate enough to know the surface composition of several bodies of the solar system, we just don’t know enough about exoplanets to be able to judge which are more suitable for colonization. At best we have managed to infer the presence of some elements in the atmosphere of a few exoplanets but we are nowhere near a full resource guide. Human civilization has always been dependent on agriculture for a variety of resources to survive and thrive. This will continue to be true when we move beyond Earth.
Now that the EmDrive has made its way into the peer-reviewed literature, it falls in range of Tau Zero’s network of scientist reviewers. Marc Millis, former head of NASA’s Breakthrough Propulsion Physics project and founding architect of the Tau Zero Foundation, has spent the last two months reviewing the relevant papers. Although he is the primary author of what follows, he has enlisted the help of scientists with expertise in experimental issues, all of whom also contributed to BPP, and all of whom remain active in experimental work. The revisions and insertions of George Hathaway (Hathaway Consulting), Martin Tajmar (Dresden University), Eric Davis (EarthTech) and Jordan Maclay (Quantum Fields, LLC) have been discussed through frequent email exchanges as the final text began to emerge. Next week I’ll also be presenting a supplemental report from George Hathaway. So is EmDrive new physics or the result of experimental error? The answer turns out to be surprisingly complex.
by Marc Millis, George Hathaway, Martin Tajmar, Eric Davis, & Jordan Maclay
It’s time to weigh in about the controversial EmDrive. I say, controversial, because of its profound implications if genuine, plus the lack of enough information with which to determine if it is genuine. A peer-reviewed article about experimental tests of an EmDrive was just published in the AIAA Journal of Propulsion and Power by Harold (Sonny) White and colleagues: White, H., March, P., Lawrence, J., Vera, J., Sylvester, A., Brady, D., & Bailey, P. (2016), “Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum,” Journal of Propulsion and Power, (print version pending, online version here.
That new article, plus related peer-reviewed articles, were reviewed by colleagues in our Tau Zero network, including two who operate similar low-thrust propulsion tests stands. From our reviews and discussions, I have reached the following professional opinions – summarized in the list below and then detailed in the body of this article. I regret that I can only offer opinions instead of definitive conclusions. That ambiguity is a significant part of this story that also merits discussion.
Overview
Technical
(1) The experimental methods and resulting data indicate a possible new force-producing effect, but not yet satisfying the threshold of “extraordinary evidence for extraordinary claims” – especially since this is a measurement of small effects.
(2) The propulsion physics explanations offered, which already assume that the measured force is real, are not sound.
(3) Experiments have been conducted on other anomalous forces, whose fidelity and implications merit comparable scrutiny, specifically Jim Woodward’s “Mach Effect Thruster.”
Implications
(1) If either the EmDrive or Mach Effect Thrusters are indeed genuine, then new physics is being discovered – the ramifications of which cannot be assessed until after those effects are sufficiently modeled. Even if it turns out that the effects are of minor utility, having new experimental approaches to explore unfinished physics would be valuable.
(2) Even if genuine, it is premature to assess the potential utility of these devices. Existing data only addresses some of the characteristics necessary to compare with other technologies. At this point, it is best to withhold judgment, either pro or con.
Pitfalls to Avoid
(1) The earlier repeated tactic, to attempt fast and cheap experimental tests, has turned out to be neither fast nor cheap. It’s been at least 14 years since the EmDrive first emerged (2002) and despite numerous tests, we still lack a definitive conclusion.
(2) In much the same way that thermal and chamber effects are obscuring the force measurements, our ability to reach accurate conclusions is impeded by our natural human behavior of jumping to conclusions, confirmation biases, sensationalism, and pedantic reflexes. This is part of the reality that also needs understanding so that we can separate those influences from the underlying physics.
Recommendations
(1) Continue scrutinizing the existing experimental investigations on both the EmDrive and Mach Effect Thrusters.
(2) To break the cycle of endlessly not doing the right things to get a definitive answer, begin a more in-depth experimental program using qualified and impartial labs, plus qualified and impartial analysts. The Tau Zero Foundation stands ready to make arrangements with suitable labs and analysts to produce reliable findings, pro or con.
(3) If it turns out that the effects are genuine, then continue with separate (a) engineering and (b) physics research, where the engineers focus on creating viable devices and the physicists focus on deciphering nature. In both cases:
Characterize the parameters that affect the effects.
Deduce mathematical models.
Apply those models to (a) assess scalability to practical levels, and (b) understand the new phenomena and its relation to other fundamental physics.
On all of the above, conduct and publish the research with a focus on the reliability of the findings rather than on their implications.
Details
Pitfall 1 – The Fog of Want
Our decisions about this physics are influenced by behaviors that have nothing to do with physics. To ignore this human element would be a disservice to our readers. To get to the real story, we need to reveal that human element so that we can separate it from the rest of the data, like any good experiment. I’m starting off with this issue so that you are alert to its influences before you read the rest of this article.
As much as I strive to be impartial, I know I have an in-going negative bias on the EmDrive history. To create a review that reflects reality, rather than echoing my biases, I had to acknowledge and put aside my biases. Similarly, if you wish to extract the most from this article, you might want to check your perspectives. Ask yourself these three questions: (1) Do you already have an opinion about this effect and are now reading this article to see if we’ll confirm your expectation? (2) Do you want to know our conclusions without any regard to how we reached those conclusions? (3) Are you only interested in this EmDrive assessment, without regard to other comparable approaches?
If you answered “yes” to any of those questions, then you, like me, have natural human cognitive dysfunctions. To get past those reflexes, start by at least noticing that they exist. Then, take the time to notice both the pros and cons of the article, not just the parts you want to be true. Deciphering reality takes time instead of just listening to reflexive beliefs. It requires that one’s mind be open to the possibility you might be right and equally open to the possibility you might be wrong.
EmDrive History
This history is a recurring theme of incredible claims with non-credible evidence for those claims. In all cases, the effect is assumed to be real before the tests – which reflects a blinding bias. This dates back to at least 2002 when Roger Shawyer claimed to invent a device that “provides direct conversion from electrical energy to thrust, without expelling propellant.” I was still at NASA and vaguely remember reviewing it then. Regardless of the claims, the fidelity of the methods were below average. Over the years I heard about several other tests, but never saw any data. Eventually there was a press story about tests in China, along with this photo. It turns out that this photo is not a Chinese rig, but one of Shawyer’s:
Shawyer’s device and supporting equipment are on a rotating frame, where that rotation is used to determine if the device is thrusting. Note, however, the radiator and coolant lines. Any variation in the coolant flow would induce a torque that would obscure any real force measurements. Knowing the claimed thrusting effect is small and having enough experience to guess the likely variations in coolant flow, I considered this test set-up flawed.
Regarding the Chinese tests, I did not previously know they are described in peer-reviewed articles. Since many of us did not know either, I’m listing them here along with cursory impressions:
Juan, Y., et al, (2012). Net thrust measurement of propellantless microwave thrusters. Acta Physica Sinica, Chinese Physical Society.
Due to all of the impressions below, I do not have any confidence in their data:
Assumes first that the EmDrive is genuine.
Verbally describes theory, but without predicting experimental findings.
The experiment is not described in enough detail to assess its fidelity, but is similar to the one in the photo. Regardless, there is absolutely no discussion of possible influences on the rotation from tilting, power lead forces, vibration effects, thermal effects, or others.
The behavior of the thrust stand was not characterized before installing the EmDrive. Testing the two together without first having characterized the thrust stand separately prevents separating their distinct characteristics from the data.
The data plots lack error bands.
Juan, Y., et al (2013). Prediction and experimental measurement of the electromagnetic thrust generated by a microwave thruster system. Chinese Physics B, 22(5), 050301.
Due to all of the impressions below, I do not have any confidence in their data:
The description of the experiment is improved from the 2012 paper and appears to be the same configuration. This time possible effects from tilting and the power lead forces are mentioned, but they still do not address vibration, thermal, coolant loop, or other effects.
Again, they fail to characterize the thrust stand separately from the EmDrive.
Unlike the 2012 paper, they attempt to make numerical predictions. Details are provided for their physics derivations (which I did not scrutinize). That theory is then applied to make predictions for their specific hardware, but only verbally described it, rather than showing an explicit derivation. They show plots of the predicted force versus power, but only up to 200W, where the experimental runs span about 100W to 2400W.
The experimental results do not match their linear predictions for the ratio of force-to-power. These differences are then evasively dismissed.
Juan, Y., et al. (2016), “Thrust Measurement of an Independent Microwave Thruster Propulsion Device with Three-Wire Torsion Pendulum Thrust Measurement System,” Journal of Propulsion Technology, vol. 37, no. 2, pp 362-371.
The text is in Chinese, which I did not translate, but the figures and plots are captioned in English. Therefore I comment only on those diagrams. Again, what is shown is not enough to support claims of anomalous forces:
From figures 2, 3, 6, 7, 16, and 19, it appears the prior apparatus is now hung from torsion wires instead of a rotating support from below. This time the coolant loop is explicitly shown, but in a conceptual drawing instead of showing specifics. Again, the influence of the coolant loop is ignored.
The only “measurement results” plot is “force versus serial number” – which conveys no meaningful information (without being able to read associated text).
I learned later from Martin Tajmar, that the observed thrust drops by more than an order of magnitude when the device is powered by batteries instead of the external cables (cables whose currents can induce forces).
I chose not to cite and comment on the many non-peer-reviewed articles on Shawyer’s website and related AIAA conference papers.
Shawyer eventually published a peer-reviewed article, specifically: Shawyer, R. (2015), “Second generation EmDrive propulsion applied to SSTO launcher and interstellar probe,” Acta Astronautica, vol. 116, pp 166-174. Shawyer states: “Theoretical and experimental work in the UK, China and the US has confirmed the basic principles of producing thrust from an asymmetric resonant microwave cavity.” That assertion has not held up to scrutiny. Therefore, all related assertions are equally unfounded. Instead of offering substantive evidence, this article instead predicts the performance for three variations of EmDrives that now claim to use superconductivity. From these, he presents conceptual diagrams for their respective spacecraft. He also mentions the “Cannae Drive,” by Guido Fetta, as another embodiment of his device.
Latest EmDrive Paper
The latest paper, in the AIAA Journal of Propulsion and Power, is an improvement in fidelity on the prior tests and may be indicative of a new propulsive effect. However, the methods and data are still not crossing the threshold of “extraordinary evidence for extraordinary claims” – especially since this is a measurement of small effects. With the improved fidelity of the reporting and the data traces themselves, I have to question my earlier bias that the prior data was entirely due to experimental artifacts and proponent biases.
The assessment offered below is a summary of discussions with the coauthors of this report plus a few other colleagues. Both Martin Tajmar and George Hathaway operate similar low-thrust propulsion test stands and thus are familiar with such details. George Hathaway’s more focused analysis will be posted in a future Centauri Dreams article.
The major problems with the paper are (1) lack of impartiality, (2) the test hardware is not sufficiently characterized to separate spurious effects from the test article’s effects, (3) the data analysis is marred by the use of subjective techniques, and (4) the data can be interpreted in more than one way – where one’s bias will affect one’s conclusions.
The first shortcoming of the paper is that it is biased. It assumes that the propulsion effect is genuine and then goes on to invent an explanation for that unverified effect. This bias skews how they collect and analyze the data. To be more useful, the paper should have reported impartially on its experimental and analytical methods to isolate a potential new force-producing effect from other contaminating influences.
The next shortcoming is insufficient testing for how spurious causes can affect the thrust stand. While this new paper is a significant improvement over the previous publications, it falls short of providing the needed information to reach a definitive conclusion. They use techniques comparable to engineering tests of conventional low-thrust electric propulsion. While such engineering techniques might be passable for checking electric propulsion design changes, it is not sufficient to demonstrate that a new physics effect exists. The specific shortcomings include:
Thrust stand tilting: The thrust stand has a vertical axis, where even slight changes of that alignment will affect how the thrust stand behaves. There are three parts to this, none of which are quantified: the fidelity of the thrust stand flexures and pivots, the alignment fidelity of that structure to the vacuum chamber, and the sustained levelness of the “optical bench” upon which the vacuum chamber is mounted.
Thrust stand characterization: The thrust stand does not return to its original position after tests, even for most calibration events. Additionally, the thrust stand is over-damped, meaning that it is slow to respond to changes, including the calibration events. Those characteristics (time for the thrust stand to respond to a known force and the difference between its before/after positions) are important to understand so that those artifacts can be separated from the data. These facets are largely ignored in the paper. The report does mention that the location of the masses on the thrust stand affects its response rate (“split configuration” versus “non-split”), but this difference is not quantified. The thrust stand uses magnetic dampers. Similar dampers used on one of Martin Tajmar’s thrust stands were found to cause spurious effects (subsequently replaced with oil dampers). Given the irregular behavior, it is fair to suspect that other causes are interfering with the motion of the thrust stand. The flexural bearings might be operated beyond their load capacity or might be affected by temperature.
Forces from power cables: To reduce the influence of electromagnetic forces from the power leads, Galinstan liquid metal screw and socket connections are used. While encouraging, it is not specified if these connections (several needed) are all coaxially aligned with the stand’s rotation axis (as required to minimize spurious forces). Also, there are no tests with power into a dummy load to characterize these possible influences.
Chamber wall interactions: Though mentioned as a possible source of error, the electromagnetic forces between the test device and the vacuum chamber walls are dismissed without quantitative estimates or tests. One way that this could have been explored is by using more variations in the position and orientation of the test device relative to the chamber. For example, in the “null thrust” configuration, only one of four possibilities is used (the device pointed toward the pivot axis). If also pointed up, down, and away from the pivot, more information would have been collected to help assess such effects.
Thermal effects: The paper acknowledges the possible contributions from thermal effects, but does not quantify that contribution. For example, there are no measurements of temperature over time compared to the thrust stand’s deflection. Such measurements should have been made during operation of the device and when running power through a dummy load. Absent that data, the paper resorts to subjectively determining which parts of the data are thermal effects. For example, without any validation, the paper assumes that the displacement measured during the “null thrust” configuration is entirely a thermal effect. It does not consider chamber wall interactions or any other possible sources. The paper does speculate that temperature changes might shift the center of gravity of the test article in a way that affects the thrust stand, but no diagrams are offered showing how a slight change in one of those dimensions would affect the thrust stand.
The third and most egregious shortcoming in the report is that they apply a vaguely described “conceptual simulation” (which is never mathematically detailed) as their primary tool to deduce which part of the data is attributable to their device and which is due to thermal effects. They assume a priori the shapes of both the “impulsive thrust” (their device) and thermal effects and how those signals will superimpose. There is no consideration of chamber wall effects, power lead forces, tilting, etc. As a reflection of how poorly defined this assumed superposition, the ‘magnitude’ and ‘time’ axes on the chart showing this relation (Fig. 5) are labeled as “arbitrary units.” Another problem is that their assumed impulsive thrust curve does not match the shape of most of the data that they attribute to impulsive thrust. Instead of the predicted smooth curve, the data shows deviations about halfway through the thrusting time. They then apply this subjective and arbitrary tool to reach their conclusions. Because they are biased that the effect is genuine and because their methods overlook critical measurements, I cannot trust the authors’ interpretations of their results.
Absent an adequate accounting for the magnitude and characteristics of secondary causes and how to remove those possible influences from the data, the fourth major problem with the report is that its data can then be interpreted more than one way.
Rather than evoking subjective techniques here, the comments that follow are based only on examining their data plots as a whole. To illustrate how this data can then be interpreted in more than one way, both dismissive and supportive interpretations are offered. In particular, we compare the traces from the “forward,” “null,” and “reverse” thrust configurations and then the force versus power compilation of the runs.
The data for the 80W operation of the device in the “forward,” “null,” and “reverse” thrust configurations is presented in Figures, 9c, 18, and 10c, respectively. Recall from the above discussions that this data includes all the uncharacterized spurious causes (thermal, chamber wall interactions, power lead forces, tilting of the thrust stand, and seismic effects), plus any real force from the test device. The values shown in the table below were read from enlarged versions of the figures.
Table of Noteworthy Data Comparisons Between Forward, Null, and Reverse Thrust Orientations
For a genuine thrusting effect, one would expect the results to show near-matching magnitudes for forward and reverse thrust and a zero magnitude for the null-thrust orientation. If one looks only at the “Total deflection,” all the magnitudes are roughly the same, including the null-thrust. Pessimistically, one could then infer that the spurious effects are great enough to be easily misinterpreted as a genuine thrust.
Conversely, if one considers how quickly the deflections occur, then the attention would be on the “Rate of deflection.” In that case, the thrusting configurations are roughly twice as large as the null-thrust configuration. From only that, one might infer that a new force-producing effect is larger than spurious causes.
To infer conclusions based on the deflection rates, one must also examine the rate of deflection for the calibration events, which should be the same in all configurations. The calibration deflection rate appears roughly the same in the forward and reverse thrust configuration, but more than 2.5 times larger in the null thrust configuration. That there is a difference compounds the difficulty of reaching conclusions. There are also significant inconsistencies with how the thrust stand rebounds once the power is turned off between the thrusting and null-thrust configurations, again compounding the difficulty of reaching conclusions.
Because a possible positive interpretation exists within those different perspectives, I cannot rule out the possibility that the data reflects a new force-producing effect. But as stated earlier, given all the uncharacterized secondary effects and the questionable subjective techniques used in the report, this is not sufficient evidence. Given the prominent role played by the rate of deflections, the dynamic behavior of the thrust stand must be more thouroughly understood before reaching firm conclusions.
Next, let’s examine the compilation of runs, namely Fig. 19. Based on a linear fit through the origin with the data, they conclude a thrust-to-power ratio of 1.2 ± 0.1 mN/kW (=µN/W). While this is true, the data can be interpreted more than one way. Note that the averages for 60 and 80 watts operations are the same, so a linear fit is not strictly defensible. One could just as easily infer that increasing power yields decreasing thrust, a constant 50 µNewton force, or an exponential curve that flattens out to a constant (saturated) thrust of about 100 uN. Note too that the null-thrust data (which could be interpreted to be as high as 211 µN) is not shown on this chart.
Recall too that they did not quantify the potential spurious effects, so their presumed error band of only ±6 µN does not stand up to scrutiny. Note, for example, the span in the 40W data is about ± 17µN, the 60W about ± 50µN, and the 80W about ± 32µN. What is not clear is if these 40, 60, and 80 Watt runs represent different operating parameters (Q-factor?), or if instead, these are the natural variations with fixed settings.
The pessimistic interpretation is that the deviations in the data represent variations for the same operating conditions, in which case the data are too varied from which to conclude any correlations. Conversely, the optimistic interpretation is to assume the variations are due to changes in operating parameters, but then that additional information should be made available and be an explicit part of the analysis.
In summary, this most recent report is a significant improvement, but has many shortcomings. Questionable subjective techniques are used to infer the “thrust” from the data. Other likely influences are not quantified. But also, despite those inadequacies, the possibility of a new force-producing effect cannot be irrefutably ruled out. This is intriguing, but still falling short of defensible evidence.
EmDrive and Other Space Drive Theories
First, I cannot stress enough that there is no new EmDrive “effect” yet about which to theorize. The physical evidence on the EmDrive is neither defensible nor does it include enough operating parameters to characterize a new effect. The data is not even reliable enough to deduce the force-per-power relationship, let alone any other important correlations. What about the effects of changing the dimensions or geometry, changing the materials, or changing the microwave frequencies or modulation? And then there is the unanswered question, what are the propulsion forces pushing on?
Assuming for the moment that the EmDrive is a new force-producing effect, we know at least two things (1) it is not a photon rocket, because the claimed forces are 360 times greater than the photon rocket effect, and (2) a force, without an “equal and opposite force,” goes beyond Newton’s laws. Note that I did not evoke the more familiar “violating conservation of momentum” point. That is because these experiments are still trying to figure out if there is a force. We won’t get to conservation of momentum until after those forces are applied to accelerate an object. If that happens, then we must ask what reaction mass is being accelerated in the opposite direction. If the effects are indeed genuine, then new physics is being discovered or old physics is being applied in a new, unfamiliar context.
For those claiming to have a theory to predict a new propulsion effect, it is necessary that those theories make testable numeric predictions. The predictions in Juan’s 2013 paper did not match its results. The analytical discussions in White’s 2016 experimental paper do not make theoretical predictions. The same is true with his 2015 theoretical paper: White (2015), “A discussion on characteristics of the quantum vacuum,” Physics Essays, vol. 28, no. 4, 496-502.
Short of having a self-consistent theory, any speculations should at least accurately echo the physics they cite. The explanations in the White’s 2016 experimental paper, White’s 2015 theory paper, and even White’s 2013 report on the self-named “White-Juday Warp Field Interferometer” (White (2013), “Warp Field Mechanics 101,” Journal of the British Interplanetary Society, vol. 66, pp. 242-247), did not pass this threshold. I’ll leave to other authors to elaborate on the 2015 and 2016 papers, while a review of the 2013 warp drive claims is available here. It is Lee & Cleaver (2014), “The Inability of the White-Juday Warp Field Interferometer to Spectrally Resolve Spacetime Distortions,” [physics.gen-ph].
In contrast, it is also important to avoid pedantic reflexes – summarily dismissing anything that does not fit what we already know, or assuming all of our existing theories are completely correct. For example, the observations that lead to the Dark Matter and Dark Energy hypotheses do not match existing theories, but that evidence has been reliably documented. Using that data, many different theories are being hypothesized and tested. The distinction here is that both the proponents and challengers make sure they are accurately representing what is, and is not yet, known.
If a propulsion physics breakthrough is to be found, it will likely be discovered by examining relevant open questions in physics. A relevant theoretical question to non-rocket propulsion concepts (including the EmDrive) is ensuring conservation of momentum. One way to approach this is to look for phenomena is space that might serve as a reaction mass in lieu of propellant, perhaps like the quantum vacuum. Another approach is to dig deeper into the nature of inertial frames. Inertial frames are the reference frames upon which the laws of motion and the conservation laws are defined, yet it is still unknown what causes inertial frames to exist or if they have any deeper properties that might prove useful.
Woodward Tests and Theory
In addition to the overtly touted EmDrive, there are about two-dozen other space drive concepts of varying degree of substance. One of them started out as a theoretical investigation into the physics of inertial frames which then advanced to make testable numeric predictions. Specifically I’m referring to what is now called the “Mach Effect Thruster” concept of James F. Woodward, which dates back at least to this article:
Woodward, James F. (1990), “A new experimental approach to Mach’s principle and relativistic gravitation,” Foundations of Physics Letters, vol. 3, no. 5, pp. 497-506.
A more in-depth and recent publication on these concepts is available as:
Woodward, James F. (2013) Making Starships and Stargates: The Science of Interstellar Transport and Absurdly Benign Wormholes. Springer Praxis Books.
Experiments have been modestly underway for years, including three recent independent replication attempts by George Hathaway in Toronto Canada, Martin Tajmar in Dresden Germany, and Nembo Buldrini in Wiener Neustadt, Austria. A workshop was held to review these findings in September 20-23, 2016, in Estes Park, Colorado. I understand from an email conversation with Jim Woodward that these reports and workshop proceedings are now undergoing peer review for likely publication early in 2017.
The main point here, by citing just this one other example, is that there are other approaches beyond the highly publicized EmDrive claims. It would be a disservice to our readers to let a media fixation with one theme blind us to alternatives.
Implications
If either the EmDrive or Mach Effect Thruster is indeed genuine, then new physics is being discovered or old physics is being applied in a new, unfamiliar context. Either would be profound. Today it is premature to assert than any of these effects are genuine, or conversely, to flatly rule out that such propulsion ambitions are impossible. When the discussions are constrained to exclude pedantic disdain and wishful interpretations, and limited to people who have either the education or experience in related fields, one encounters multiple, even divergent, perspectives.
Next, even if new physics-to-engineering is emerging, it is premature to assess its utility. The number of factors that go into deciding if a technology has an advantage over another are way beyond what data is yet available. Recall that the performance of the first aircraft, jet engine, transistor, etc, were all tiny examples of what those breakthroughs evolved to become. Reciprocally, we tend to forget about all the failed claims who have faded into obscurity. We just do not know enough today, pro or con, to judge.
I realize the urge within human behavior for fast, definitive answers that we can act on. This lingering uncertainty is aggravating, even more so when peppered with distracting hype or dismissive disdain. To get to the underlying reality, we must continue with a focus on the fidelity of the methods to produce reliable results, rather than jumping to conclusions on the implications.
What to Do About It
If you want definitive answers, then we must improve the reliability of the methods and data, and remain patiently open for the results to be as they are, good news or bad news. I alluded earlier to the broken tactic of trying to get answers with fast and cheap experiments. How many inadequate experiments and over how many years does it take before we change our tactics? I’ve had this debate more than once with potential funding sources and I hope they are reading now to see… “I told ya so!” Sorry, I could not resist that human urge to emotionally amplify a well-reasoned point. To break the cycle of endlessly not doing the right things to get a definitive answer, we must begin a more in-depth experimental program using qualified and impartial labs, plus qualified and impartial analysts. Granted, those types of service providers are not easy to find, where impartiality is the hardest to come by. Also, it might take three years to get a reliable answer, which is at least better than 14 years. And the trustworthy experiments will not be cheap, but quite likely far less than the aggregate spent on the repeated ‘cheap’ experiments. If any of those prior funding sources (or new) are reading this and finally want trustworthy answers, contact us. Tau Zero stands ready to make arrangements with suitable labs and analysts to conduct such a program.
And what if we do discover a breakthrough? In that case, we recommend distinguishing two themes of research, one from an engineering point of view to nudge the effect into a useful embodiment, and another from an academic point of view, to fully decipher and compare the new effects to physics in general. In both those cases we need to:
1. Characterize the parameters that affect the effects. Instead of just testing one design, vary the parameters of the device and the test conditions to get enough information to work with.
2. Deduce mathematical models from that more complete set of information.
3. Apply those models to (a) assess scalability to practical levels, and (b) explore the new phenomena and its relation to other fundamental physics.
4. On all of the above, conduct and publish the research with a focus on the reliability of the findings rather than on their implications.
For those of you who are neither researchers nor funding sources, what should you do? First, before reposting an article, take the time to see if it offers new and substantive information. If it turns out to be hollow click-bait, then do not share it. If it has both new information with meaningful details, then share it. Next, as your read various articles, notice which sources provide the kind of information that helps you understand the situation. Spend more time with those sources and avoid sources who do not.
Regarding questionable press stories, I’m not sure yet what to make of this: “The China Academy of Space Technology (CAST), a subsidiary of the Chinese Aerospace Science and Technology Corporation (CASC) and the manufacturer of the Dong Fang Hong satellites, has held a press conference in Beijing explaining the importance of the EmDrive research and summarizing what China is doing to move the technology forward.” Some stories claim there is a prototype device in orbit. If true, I would expect to see at least one photo of the device being tested in space. But we’ll see…
When faced with uncertain situations and where the data is unreliable, the technique I use to minimize my biases is to simultaneously entertain conflicting hypotheses, both the pro and con. Then, as new reliable information is revealed, I see which of those hypotheses are consistent with that new data. Eventually, after enough reliable data has accrued, the reality becomes easier to see.
Note
The cited devices have gone by multiple names (e.g. EmDrive, EM Space Drive; Mach Effect Thruster, Mach-Lorentz Thruster), and the versions used in this article are the ones with the greatest number of Google search hits.
Let’s talk this morning about the relationship of Proxima Centauri to nearby Centauri A and B, because it’s an important issue in our investigations of Proxima b, not to mention the evolution of the entire system. Have a look at the image below, which shows Proxima Centauri’s orbit as determined by Pierre Kervella (CNRS/Universidad de Chile), Frédéric Thévenin (Observatoire de la Côte d’Azur) and Christophe Lovis (Observatoire astronomique de l’Universite? de Gene?ve). The three astronomers have demonstrated that all three stars — Proxima Centauri as well as Centauri A and B — form a single, gravitationally bound system.
Image: Proxima Centauri’s orbit (shown in yellow) around the Centauri A and B binary. Credit: Kervella, Thévenin and Lovis.
A couple of things to point out here, the first being the overall image. You’ll see Alpha Centauri clearly labeled within the yellow ellipse of Proxima’s orbit. Off to the right of the ellipse, you’ll see Beta Centauri. I often see the image of these two stars identified as Centauri A and B, but Kervella et al have it right. The single bright ‘star’ within the ellipse is the combined light of Centauri A and B. Beta Centauri, at the right, is an entirely different star, itself a triple system in the constellation Centaurus, at a distance of about 400 light years.
Now as to that orbit — 550,000 years for a single revolution — things get interesting. One reason it has been important to firm up Proxima’s orbit is that while a bound star would have affected the development of the entire system, the question has until now been unresolved. Was Proxima Centauri actually bound to Centauri A and B, or could it simply be passing by, associated with A and B only by happenstance? Back in 1993 Robert Matthews and Gerard Gilmore found this to be a borderline case, calling for further kinematic data to clarify the issue.
When Jeremy Wertheimer and Gregory Laughlin (UC-Santa Cruz) attacked the problem in 2006, they found it ‘quite likely’ that Proxima Centauri was bound to the A/B pair. If this were the case, it would mean that the trio probably formed together out of the same nearby material, with the result that we could expect them to have the same age and metallicity. Laughlin and Wertheimer assumed that future, yet more accurate kinematic measurements would make it clear ‘that Proxima Cen is currently near the apastron of an eccentric orbit…’
And now we have Kervella and team, who have used the HARPS instrument (High Accuracy Radial Velocity Planet Searcher) on ESO’s 3.6m instrument at La Silla to make the call. Using radial velocity and astrometry, the researchers have surmounted the main problem with determining Proxima’s bound state. The lack of high-precision radial velocity measurements has been the result of Proxima’s relative faintness, but drilling down into HARPS data has produced a new radial velocity of ?21.700 ± 0.027 km s?1, which tracks nicely with the prediction of Wertheimer and Laughlin, and is low enough to indicate a bound state.
As we consider that interesting planet around Proxima Centauri, we now can ponder that its star is the same age as Centauri A and B, and that its age is a comparable 6 billion years, making the planet about a billion years older than our Earth. Exactly how the planet formed becomes an interesting issue as well, because we have interactions between three stars to think about. From the paper:
The orbital motion of Proxima could have played a significant role in the formation and evolution of its planet. Barnes et al. (2016) proposed that a passage of Proxima close to ? Cen may have destabilized the original orbit(s) of Proxima’s planet(s), resulting in the current position of Proxima b. Conversely, it may also have influenced circumbinary planet formation around ? Cen (Worth & Sigurdsson 2016). Alternatively, Proxima b may also have formed as a distant circumbinary planet of ? Cen, and was subsequently captured by Proxima. In these scenarios, it could be an ocean planet resulting from the meltdown of an icy body (Brugger et al. 2016). Proxima b may therefore not have been located in the habitable zone (Ribas et al. 2016) for as long as the age of the ? Cen system (5 to 7 Ga; Miglio & Montalbán 2005; Eggenberger et al. 2004; Kervella et al. 2003; Thévenin et al. 2002).
So there we are. Plenty of alternatives to ponder as we look into the origins of the nearest known planet to our Solar System. Just how the researchers tuned up the radial velocity data to avoid the problem of convective blueshift — where the star’s unstable surface can shift the observed wavelength of spectral lines – and gravitational redshift, which can likewise be misleading, is covered in the paper’s appendix. The selection of four strong very high signal-to-noise emission lines made the difference in this exquisitely tight measurement.
The paper is Kervella, Thévenin & Lovis, “Proxima’s orbit around ? Centauri,” accepted at Astronomy & Astrophysics (preprint).
I love watching people who have a passion for science constructing projects in ways that benefit the community. I once dabbled in radio astronomy through the Society of Amateur Radio Astronomers, and I could also point to the SETI League, with 1500 members on all seven continents engaged in one way or another with local SETI projects. And these days most everyone has heard the story of Planet Hunters, the citizen science project that identified the unusual Boyajian’s Star (KIC 8462852). When I heard from Roger Guay and Scott Guerin, who have been making their own theoretical contributions to SETI, I knew I wanted to tell their story here. The post that follows lays out an alien civilization detection simulation and a tool for visualizing how technological cultures might interact, with an entertaining coda about an unusual construct called a ‘Dyson shutter.’ I’m going to let Roger and Scott introduce themselves as they explain how their ideas developed.
by Roger Guay and Scott Guerin
Citizen Science plays an increasingly important role across several scientific disciplines and especially in the fields of astronomy and SETI. Tabby’s star, discovered by members of the Planet Hunters project and the SETI@home project are recent examples of massively parallel citizen-science efforts. Those large-scale projects are counterbalanced by individuals whose near obsession with a subject compels them to study, write, code, draw, design, talk about, or build artifacts that help them understand the ideas that excite them.
Roger Guay and Scott Guerin, working in isolation, recently discovered parallel evolution in their thinking about SETI and the challenges of interstellar detection and communication. Guay has undertaken the programming of a 10,000 x 8,000 light year swath of a typical galaxy and populates it with random radiating communicating civilizations. His model allows users to tweak basic parameters to see how frequently potential detections occur. Guerin is more interested in a galaxy-wide model and has used worksheets and animations to bring his thoughts to light. His ultimate goal is to develop a parametric civilization model so that interactions, if any, can be studied. However, at the core, both efforts were attempts at visualizing the Fermi Paradox across space-time, and both experimenters show how fading electromagnetic halos may be all that’s left for us to discover of an extraterrestrial civilization, if we listen hard enough.
The backgrounds, mindsets, and tool kits available to Roger and Scott play an important role in their path to this blog.
Roger Guay
I am a retired Physicist and Technical Fellow Emeritus from Boeing in Seattle. I can’t remember when I first became interested in being a scientist (it was in grade school) but I do remember when I first became obsessed with the Fermi paradox. It was during a discussion while on a road trip with a colleague. At first, this discussion mainly revolved around the almost unfathomable vastness of space and time in our galaxy, but then turned to parameters of the Drake equation. The one that was the most controversial was L, the lifetime of an Intelligent Civilization or IC.
The casual newcomer to the Drake equation will tend to assume a relatively long lifetime for an IC, but when considering detection methods such as SETI uses, one must adjust L to reflect the lifetime of the technology of the detection method. For example, SETI is listening for electromagnetic transmissions in the microwave to radio and TV range. So, L has to be the estimated lifetime of that technology. For SETI’s technology, we’ll call this the Radio Age. On Earth, the Radio Age started about 100 years ago and has already fallen off due to technological advances such as the internet and satellite communication. So I argued, an L = 150 ± 50 years might be a more reasonable assumption for the Drake equation when considering the detection method of listening for radio signals.
At this point the discussion was quite intense! When I thought about an L equal to a few hundred years in a galaxy that continues to evolve over a 13-billion-year lifespan, the image that came to my mind was that of fireflies in the night. And that was the precursor for my Alien Civilization Detection or ACD simulation.
One can imagine electromagnetic or “radio” bubbles appearing randomly in time and space and growing in size over time. At any instant in time the bubble from an IC will have a radius equal to the speed of light times the amount of time since that IC first began broadcasting. These bubbles will continue to grow at the speed of light. When the IC stops broadcasting for whatever reason, the bubble will become hollow and the shell thickness will reflect the time duration of that IC’s Radio Age lifetime.
If the age of our galaxy is compressed into one year, we on Earth have been “leaking” radio and television signals into space for only a small fraction of a second. And, considering the enormity of space and the fact that our “leakage” radiation has only made it to a few hundred stars out of the two to four hundred billion in our galaxy, one inevitably realizes there must be a significant synchronization problem that arises when ICs attempt to detect one another. So what does this synchronicity problem look like visually?
To answer this question my tasks became clear: dynamically generate and animate radio bubbles randomly in space and time, grow them at the speed of light at very fast accelerated rate in a highly compressed region of the galaxy, fade them over time for inverse square law decay, and then analyze the scene for detection. No Problem!!!
Using LiveCode, a modern derivative of HyperCard on steroids, I began my 5-year project to scientifically simulate this problem. Using the Monte Carlo Method whereby randomly generated rings denoting EM radiation from ICs pop into existence in a 8,000 X 10,000 LY region of the galaxy* centered on our solar system at a rate of about 100 years per second, the firefly analogy came to life. And the key to determining detection potential is to recognize that it can only occur when a radiation bubble is passing over another IC that is actively listening. This is the synchronicity problem that is dramatically apparent when the simulation is run!
To be scientifically accurate and meaningful, some basic assumptions were required:
1. ICs will appear not only randomly in space, but also randomly in time.
2. ICs will inevitably transition into (and probably out of) a Radio/TV age where they too will “leak” electromagnetic radiation into space.
3. The radio bubbles are assumed to be spherically homogeneous**.
To use the ACD simulation, the user chooses and adjusts parameters such as Max Range, Transmit and Listen times*** and N, the Drake equation estimate of the number of ICs in the galaxy at any given instant. During a simulation run, potential detections are tallied and the overall probability of detection is displayed.
About two years ago, as the project continued to evolve, I became aware of Stephan Webb’s encyclopedic book on the Fermi Paradox, If the Universe is Teeming with Aliens … Where is Everybody? This book was most influential in my thinking and the way I shaped the existing version of the ACD simulation.
A snapshot of the main screen of the ACD simulation midway through a 10,000 year run.
Conclusions? The ACD simulation dramatically demonstrates that there is indeed a synchronicity problem that automatically arises when ICs attempt to detect one another. And for reasonable (based on Earth’s specifications) Drake equation parameter selections, detection potentials are shown to be typically hundreds of years apart. In other words, we can expect to search for a few hundred years before finding another IC in our section of the galaxy. When you consider Occam’s razor, is not this synchronicity problem the most logical resolution to the Fermi Paradox?
Footnotes:
* The thickness of the Milky Way is small compared to its diameter. So for regions close to the center of the thickness, we can approximate with a 2-dimensional model.
** Careful consideration has to be given to this last assumption: Of course, it is not accurate in that the radiation from a typical IC is assumed to be composed of many different sources and have widely varying parameters, as they are on Earth. But the bottom line is that the homogenous distribution gives the best case scenario of detection potential. An example of when to apply this thinking is to consider laser transmission vs radio broadcast. Since a laser would presumably by highly directed and therefore more intense at greater distances, the user of the ACD simulation might choose a Higher Max Range but at the same time realize that pointing problems will make detection potential much smaller than the ACD indicates. The ACD does not take this directly into consideration. Room for the ACD to grow?
*** One of the features of this simulation is that the user can make independent selections of both the transmit and listening times of ICs, whereas the Drake equation lumps them together in the lifetime parameter.
Scott Guerin
I grew up north of Milwaukee, Wisconsin and was the kid in 5th grade who would draw a nuclear reactor on the classroom’s chalkboard. My youthful designs were influenced by Voyage to the Bottom of the Sea, Lost in Space, everything NASA, and 2001: a Space Odyssey. In the mid 70s, I was a technical illustrator at the molecular biology laboratory at UW Madison and, after graduation with a fine arts degree, I went on to a 30-year career as an interpretive designer of permanent exhibits in science and history museums.
I began visually exploring SETI over two years ago in order to answer three questions: First, why is such a thought-provoking subject so often presented only in math and graphs thereby limiting information to experts? Secondly, why is the Fermi Paradox a paradox? Thirdly, what form might an interstellar “we are here” signaling technology take?
Using Sketchup, I built a simple galactic model to see what scenarios matched the current state of affairs: silence and absence. At a scale of 1 meter = 1 light year, I positioned Sol appropriately, and randomly “dropped” representations of civilizations (I refer to them as CivObjects) into the model. Imagine dropping a cup full of old washers, nails, wires, and screws onto a flat, 10″ plate and seeing if any happen to overlap with a grain-of-salt-sized solar system (and that speck is still ~105 too large).
The short answer is that they didn’t overlap and I’ve concluded that the synchronicity issue, combined with weak listening and looking protocols is a strong answer to the paradox. When synchronicity is considered along with sheer rarity of emitting civilizations (my personal stance), the silence makes even more sense.
For scale, the green area at lower right represents the Kepler star field if it were a ~6,000 LY diameter sphere. The solid discs represent currently emitting civilizations, the halos represent civilizations that have stopped emissions over time, and the lines and wedges represent directed communications. I sent this diagram to Paul and Marc at Centauri Dreams who were kind enough to pass it on to several leading scientists and they graciously, and quickly, replied with encouragement.
Curtis Charles Mead’s 2013 Harvard dissertation “A Configurable Terasample-per-second Imaging System for Optical SETI,” George Greenstein’s Understanding the Universe, Tarter’s, and the Benford’s papers, among others, were influential in my next steps. I realized the halos were unrealistic representations of a civilization’s electromagnetic emissions and that if you could see them from afar, they could be visualized as prickly, 3-dimensional sea urchin-like artifacts with tight beams of powerful radar, microwave, and laser emanating from a mushy sphere of less directional, weaker electromagnetic radiation.
From afar, Earth’s EM halo is a lumpy, flattened sphere some 120LY in radius dating to the first radio experiments in the late 1890’s. The 1974 Arecibo message toward M13 is shown being emitted at the 10 o’clock position.
From Tarter’s 2001 paper “At current levels of sensitivity, targeted microwave searches could detect the equivalent power of strong TV transmitters at a distance of 1 light year (the red sphere at center in the diagram), or the equivalent power of strong military radars to 300 ly, and the strongest signal generated on Earth (Arecibo planetary radar) to 3000 ly, whereas sky surveys are typically two orders of magnitude less sensitive. The sensitivity of current optical searches could detect megajoule pulses focused with a 10-m telescope out to a distance of 200 ly.”
In this speculative diagram, two civilizations “converse” across 70 LY. Mead’s paper confirms the aiming accuracy needed to correct for the the proper motion of the stars, given a laser beam just a handful of AU wide at the distance illustrated, is within human grasp. The civilizations shown would most likely have been emitting EM for hundreds of years so that their raw EM halos are so large and diffuse they cannot be shown in the diagram. The magenta blob represents the elemental EM “hum” of a civilization within a couple LY, the green spikes represent tightly beamed microwaves for typical communications and radar , while the yellow spikes are lasers reaching out to probes, being used as light-sail boosters, and fostering long distance high-bandwidth communications. Each civilization has an EM fingerprint, affected by their system’s ecliptic angle and rotation, persistence of ability, and types of technologies deployed — these equate to a unique CivObject.
In advance of achieving the goal of a fully parametric 3D model, I manually animated several kinds of civilizations and their interactions by imagining a CivObject as a variant of a Minkowski space-time cone. I move the cone’s Z axis (time) through a galactic hypersurface to illustrate a civilization’s history of passive and intentional transmission, as well as probes at sub-lightspeed. A CivObject’s anatomy reveals the course of a civilization’s history and I like to think of them as distant cousins of Hari Seldon’s prime radiant. https://vimeo.com/195239607 password: setiwow!
The anatomy of a CivObject allows arbitrary time scales to be visualized as function of xy directionality, EM strength, and type of emission. Below is Earth’s as a reference. Increasing transmission power is suggested by color.
I found it easy to animate transmissions but continue to struggle with visualizing periods of listening and the strength of receivers. Like Guay, I concluded that a potential detection can occur only when a transmission passes through a listening civilization. A “Conversing” model designed to actually simulate communication interactions needs to address both ends of “the line” with a full matrix of transmitter/receiver power ratios as well as sending/listening durations, directions, sensitivities, and intensities. In addition, a more realistic galactic model including 3d star locations, the GHZ, and interstellar extinction/absorption rates is needed.
And now for some sci-fi
A few months before KIC 8462852 was announced and Dyson Swarms became all the rage, I noticed one of those old ventilators on top of a barn roof and thought that if a Kardashev II civilization scaled it up to +-1AU diameter, it would become a solar powered, omni-directional signalling device capable of sending an “Intelligence was here” message across interstellar space. I called it a Dyson Shutter.
Imagine a star surrounded by a number of ribbon-like light sails connected at their poles. Each vane’s stability, movement, and position is controlled by the angle of sail relative to incoming photons from the central star. The shutter would be a high tech, ultra-low bandwidth, scalable construct. I have imagined that each sail, at the equator, would be no less than one Earth diameter wide which is at the lower end of Kepler-grade detection.
Depending on the number constructed, the vanes could be programmed to shift into simple configurations such as fibonacci and prime number sequences.
I imagine the Dyson Shutter remains in a stable message period for hundreds of rotations. Perhaps there are “services” for the occasional visitor, perhaps it has defenses against comets, incoming asteroids, or inter-galactic graffiti artists. Perhaps it is an intelligent being itself but is it a lure, a trap, a collector, or colleague? Is it possible Tabby’s star is a Dyson Shutter undergoing a multi-year message reconfiguration?
The shutter’s poles are imagined to be filled with command and control systems, manufacturing facilities, spaceports, etc.
Wrap
We hope that our work as presented here might inspire some of you to join the ranks of the Citizen Scientist. There are many opportunities and science needs the help. With today’s access to information and digital tools, anyone with a little passion for their ideas and a lot of imagination and persistence can help communicate complex issues to the public and make contributions to science. We hope that our stories resonate with at least some of you. Please let us know what you think and let’s all push back on the frontiers of ignorance!
In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).
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