Ships: surveyor Dasher, freighter Strider, passenger Arrow. Aeroplanes: hypersonic high loader Lifter, small supersonic VTOL explorer Scout

By Björn Björklund

Summary of the Contents

This essay presents evidence of a visit to Earth by intelligent beings from a planet in orbit round a nearby star, including an important intellectual artefact which must have been left by them thousands of years before the Bronze Age: the authalic radius of the Earth. The instruments and mathematics necessary for the calculation of the authalic radius were not part of the Stone Age toolkit.

The visitors also left an indication that their ships had aneutronic fusion engines using boron-11 and hydrogen-1 as fuel. The energy released by aneutronic fusion can be efficiently converted directly into electrical energy. Because little energy is wasted as heat the interstellar ships equipped with them did not have to radiate great quantities of waste heat into space using gigantic radiators.

Most of the electrical power generated on Earth today is produced by dynamos driven by steam turbines using steam raised in boilers heated by burning coal or gas, or in fission-heated boilers.

Present research efforts are focused on the design and manufacture of prototypes of neutronic fusion powered generators in which energy released in fusion reactions will boil water to steam in boilers under pressure. The steam raised will drive steam turbines, which will drive dynamos. We are still in the Steam Age.

If aneutronic generators of cheap plentiful electric power could be developed on Earth they would enable us  to cease emitting carbon dioxide in our industrial activities and to halt and then reverse the harmful effects of climate change.

Cheap electrical power available everywhere would lower the cost of heating, cooling and lighting buildings, the cost of distilling sea water, the cost of land, sea and air transport, the cost of cultivating crops, the costs of smelting minerals and of making concrete and all kinds of manufactured products.

It would lower the cost of hydrogen so much that it became the source of energy for heavy motor vehicles, locomotives, aircraft and cars. Electrical power can be used to split water into hydrogen and oxygen. When hydrogen is burnt in air the exhaust product is water.

One of the many advantages of aneutronic generators is that they would not need great quantities of cooling water to carry away waste heat and so such generators could be installed in the vast regions of the Earth that lack rivers and are far from the sea.

An example of the demand for cooling water by existing nuclear fission generators and proposed neutronic fusion generators is seen in the design of a big fission power plant being built in England beside the Bristol Channel. A great flow of sea water will be continuously pumped into its heat-exchanger from the Channel and continuously expelled, considerably warmed by waste heat, back into the sea. And because the power plant must be protected from any big wave or tsunami a massive curvaceous concrete seawall designed to stop and turn back such waves has been built between the plant and the Channel.

If the inhabitants of Earth succeed in designing and operating many widely spread aneutronic fusion generators the landscapes and seascapes of our planet would eventually revert to a more natural state. There would be few large wind turbines on land and sea and few solar-panel farms standing on land and floating on reservoirs. There would few big power transmission lines striding across countries for hundreds or thousands of kilometres.

The book describes the designs of the interstellar ships (named above), which were determined by the work each had to do.

They  used hydrogen-1 and horon-11 as fuel, fusing it in a closed fusion chamber and directly converting the energy released into electrical power, which was used to accelerate reaction-mass backward in their thrusters. To each reaction there is an equal and opposite reaction: when the ship accelerated reaction-mass backward the reaction accelerated the ship forward. They were loaded with solid iodine to be used as reaction mass. There is a discussion about the suitability of iodine and the places on Earth where it could be extracted, such as far northern seas and the Atacama Desert of Chile.

The Dashers,  Strider and Arrow were built on a frame about 100 metres above the ground on their home planet. When completed they rose up almost empty under their own power to low planet orbits and were then loaded by Lifter spaceplanes with enough fuel to accelerate out of their orbits, to keep accelerating for some years until they reached cruise speed and, at the end of the long cruise phase, to decelerate for about two years as they approached Earth and then entered low Earth orbits at relatively low speeds. The need to carry fuel with which to decelerate increased the amount of fuel they had to hold when they began their journeys compared with the amount carried by a ship performing a simple fly-by mission. It restricted the big, heavy Strider to a lower cruise speed than that of the Dashers and the Arrow.

After Strider had entered a low Earth orbit it lowered itself to an elevation of a few hundred metres and hovered while a site was chosen for its first Earth base. Geologists in the crew boarded a small supersonic VTOL (Vertical Take Off and Landing) aeroplane named Scout, which had been carried on Strider, took off vertically and covered long distances at supersonic speed  to examine and choose sites on various locations on Earth which had already been selected  as promising by sensors on Dashers. Scout was powered by engines burning hydrogen; its supersonic speed halved the travel times of subsonic aeroplanes.

These supersonic voyages in which continents and seas were crossed were the crew’s first glorious experience of the atmosphere, landscapes and seascapes of the pristine Earth. Their Scout aeroplane breached the sound barrier and was then followed by a sonic boom or bang heard by most of the New Stone Age people dwelling in the Northern Hemisphere.

 It was the Bang that ended the Stone Age.

The geologists in Scout selected on the ground the best site for the first Earth station and anchored a docking plate in the ground. Strider went there and hovered above it while crew members on the ground used additive manufacturing equipment to make a huge light-weight tube with a matching dock. Strider lifted the tube to a vertical position and docked to its top end while the dock at its bottom end was locked with the ground dock. Strider continued to hover with its horizontally rotating propellers maintaining slight upward tension on the tube.

This huge tube and the interstellar ship above it became the subject of wide-spread Earth myths in which it was likened to a World Tree. There are Scandinavian, Chinese and Indian myths about the World Tree. A Chinese myth states the height of the tree, and the Chinese name of the so-called Tree proves that it was an artificial physical object.

The work involved in refuelling the Arrow for the voyage back to its home planet is described in some detail, including finding a source of boric acid and using fluoric acid (hydrogen fluoride) in the process of separating the isotope boron-11 from boron-10. This had to be done because boron-10 could not be used in the ship’s fusion chamber.

Fluoric acid is dangerous to humans and animals and became the subject of Greek myths about the Styx river’s “hateful” water.

Boron-11 was half of the fuel; the other half was ordinary hydrogen-1, obtained by using electric power to split water into hydrogen and oxygen and removing the isotope hydrogen-2 which is naturally present in water.

A Great Winter foretold in some Scandinavian myths is explained by complicated atmospheric events caused by the ejection of iodine as reaction mass by two of the ships when they decelerated to and accelerated from the Earth.

The departure of the Arrow and its crew of intelligent living beings, who were ably assisted by a small crew of robots, almost completes the story, but it ends by telling of the sad aftermath of a disaster which destroyed or buried the visitors’ Earth base and all of the artefacts it must have contained, including writings about physics, chemistry and their applications in technology, mathematics including trigonometry and its application in navigation, health, ethics, democracy and law. Other artefacts were chemical processing plant, metal smelting plant, instruments, devices, tools and compact machines for making things and moving and processing minerals. The artefacts might also have included treatises on architecture, music and other art.

The last few lines of the book reflect on the enormity of the loss inflicted on Earth’s people by an unpredicted volcanic eruption and tectonic shift which removed the help given us by our visitors.

1

THE GREEKS KNEW THE AUTHALIC CIRCUMFERENCE OF EARTH

One Hundred Greek Feet

In 1888 Francis Penrose, an English architect who became the surveyor of St Paul’s Cathedral, measured the length of the upper step of the front of the temple called the Parthenon on the Acropolis in Athens. An ancient Greek tradition held that the breadth of this temple in Greek feet was exactly one hundred feet, a hecatompedon. Greek ekatom means “one hundred” and pedon means “feet”.

Penrose wrote “The result of my own measurements of the breadth of the Parthenon, on the top of the upper step, is 101.341 feet on the east front … ” (Penrose, Francis. An investigation of the principles of Athenian architecture: or the results of a recent survey conducted chiefly with reference to the optical refinements exhibited in the construction of the ancient buildings at Athens — London, 1888, page 11). He measured in English feet, not Greek feet.

“The principal dimensions are as follows :— Measured. Front, on the upper step … 101.341 …” (page 12).

“The breadth, 101.34 is exactly a second of latitude at the equator. This is remarkable, and would have been a happy coincidence for Gosselm in his attempt to establish an identity between ancient measures and the size of the globe” (page 12).

“The dimension above given is perhaps a sufficient approximation for a general statement, but there can be little doubt but that the front of the temple, which was always accessible for reference as a standard, was the true Hecatompedon in point of exact measurement” (page 13).

A length of 101.341 English feet is equal to 30.8887 metres. Taking this to be the length of a second of latitude we multiply by 60 to find the length of the corresponding minute: 1853.3242 metres.

“Francis Cranmer Penrose FRS (1817 – 1903) was an English architect, archaeologist, astronomer and rower. He served as Surveyor of the Fabric of St Paul’s Cathedral, President of the Royal Institute of British Architects and Director of the British School at Athens” (Wikipedia on Francis Penrose).

He was a precise man and a perceptive one in thinking that the Greek hecatompedon was equal in length to a second of latitude. But he did miss the extraordinary significance of the length of the upper step of the front of the Acropolis: it was not exactly equal to a second of latitude at the equator, as Penrose thought: the length of a second of latitude at the equator is 30.7150 metres. The hecatompedon was equal to a second of latitude on a sphere with the authalic radius of Earth. This is a sphere with the same surface area as the Earth.

Penrose must have known the authalic radius of Earth because in 1866 the English surveyor Colonel Alexander Ross Clarke published his first derivation of the Earth ellipsoid, from which the authalic radius and the authalic circumference could be calculated. Clarke published further derivations of the Earth ellipsoid in 1878 and 1880 and in 1887 was awarded the Gold Medal of the Royal Society for his work in determining the figure of the Earth.

The International Union of Geodesy and Geophysics states that “For the Earth, the authalic radius is 6,371.0072 km” (Wikipedia on Earth radius). This is the radius of a sphere with the same surface area as Earth.

Let us do the maths: The authalic diameter is 12,742,014.4 metres. Pi times the diameter gives the circumference: 40,030,218.8310 metres. Dividing the circumference by 360 gives the length of a degree of latitude on a sphere with the same surface area as Earth: 111,195.0523 metres. Dividing by 60 gives the length of a minute of latitude: 1,853.2509 metres. Dividing by 60 gives the length of a second of latitude: 30.8875 metres. This is 0.0012 metre or 1.2 millimetres shorter than the length measured on the hecatompedon by Penrose. He measured to a thousandth of an English foot, which is equivalent to 0.3 millimetre.

Penrose wrote: “With regard to the difference of .022 between the breadths of the two fronts [east and west], even wooden measuring rods are liable to a variation at least as great as this, from changes in the moisture of the atmosphere. I found during my measurements at Athens that some deal rods which I made use of in some of the measurements, and was accustomed to verify by occasionally comparing them with a known length on the building, varied as much as 1/4300 of their length = .023 foot in 100 feet; so that if wooden measures were used by the Greeks, and we suppose that an interval of several hours elapsed between the setting out of the east end, and that of the west, during which time there had been a sudden hygrometric change, there would have arisen as much difference as exists, notwithstanding the utmost desire to render the Hecatompedon exact” (page 12).

One assumes that Penrose measured the length of the upper step of the front (east end) of the Parthenon on a cool day in shadow, not in sunlight (and therefore in the afternoon) to minimise an error that might be caused by expansion of the marble in hot sunlight.

Now we compare the length of the minute of latitude derived from Penrose’s measurement of the upper step on the front of the Acropolis with the length of the minute derived from the modern value for the authalic radius of the Earth: the former is 1853.3242 metres, the latter is 1,853.2509 metres. The difference is 0.0733 metre or 73.3 millimetres (less than a hand’s breadth in a nautical mile). The length of a minute of latitude at the Equator is 1842.9 metres.

What Penrose should have said was that the breadth of the hecatompedon of the Acropolis was “exactly equal to a second of latitude on a sphere having the same surface area as the Earth”.

The Greeks could not have found the length of a second of latitude on a sphere of the same surface area as the Earth because it was impossible for them to accurately measure the equatorial circumference of the Earth and thus find the equatorial radius. Both the polar radius and the equatorial radius are required for the calculation of the authalic radius of the Earth (Wikipedia on Earth radius).

It is interesting to note that “Both the United States and the United Kingdom used an average arcminute, specifically, a minute of arc of a great circle of a sphere having the same surface area as the Clarke 1866 ellipsoid. The authalic (equal area) radius of the Clarke 1866 ellipsoid is 6,370,997.2 metres (20,902,222 feet). The resulting arcminute is 1853.2480 metres (6080.210 feet)” (Wikipedia on Nautical mile). The United States used this arcminute or nautical mile until 1954 and the United Kingdom until 1970.

The Length of The Stade

The length given for the Greek stade varies greatly depending on the literary source, but several authors have written that it was about 185 metres.

“Scholar of Greek antiquity Carl Friedrich Lehmann-Haupt claims the existence of at least six different stades. To the contrary, astronomer and historian Dennis Rawlins makes the following claim.

“That 1 stade = 185 meters (almost exactly 1/10 nautical mile) is well established.

“The 185 meter stade, as claimed by Rawlins earlier, is the most commonly accepted value for the length of the stade used by Eratosthenes in his measurements of the Earth. This is so because a great number of authors from the first century CE onward make reference to the fact that 1 Roman mile is equal to 8 stades. History tells us that the Roman mile is equal to 5000 Roman feet, each of which is just short of the familiar English foot.

“The exact difference between the Roman foot and the English foot is uncertain, but if 1 Roman foot is taken to be approximately 11.65 English inches, then one Roman mile is approximately equal to 1479 meters.  Taking 1/8 of this Roman mile gives the length of 1 stade as approximately 184.8 meters. Again, this length corresponds to one of Lehmann-Haupt’s six stades. He refers to this most frequently accepted stade as the ‘Italian’ stade” (Eratosthenes and the Mystery of the Stades – How Long Is a Stade? https://www.maa.org/press/periodicals/convergence/eratosthenes-and-the-mystery-of-the-stades-how-long-is-a-stade).

In fact if 1 Roman foot is 11.65 English inches then one Roman mile is 58,250.0000 English inches; we multiply by 25.4 and get 1,479,550.0000 millimetres or 1,479.5500 metres. We divide by 8 and find that the length of the stade is 184.9438 metres.

But if in hypothesis we take the length of the Roman foot as 11.674 English inches we find that one Roman mile is 58,370.000 English inches = 1,482,598.0000 millimetres = 1,482.5980 metres. We divide by 8 and find that the length of the stade is 185.32475 metres. If there are 10 stades to the nautical mile we find that the length of the nautical mile derived from this stade is 1853.2475 metres. The length of a minute of latitude derived from the modern value for the authalic radius of the Earth is 1,853.2509 metres. The difference is 3.4 millimetres. We therefore propose that the length of the Roman foot was 11.674 English inches = 296.52 millimetres.

“We have no ancient measures by which to determine the length of the Greek foot, but we have the general testimony of ancient writers that it was to the Roman in the ratio of 25 : 24” (A Dictionary of Greek and Roman Antiquities, edited by William Smith and Charles Anthon, under the heading Pes, page 763).

But we have always had such an ancient measure: we can find the length of the Greek foot from Penrose’s measurement of the length of the hecatompedon: we divide 30.8887 metres by 100 and multiply by 1000 and find 308.89 millimetres.

We divide this length of the Greek foot, 308.89 millimetres by our proposed length of the Italian foot, 296.52 millimetres and find 1.0417. We divide 25 by 24 and find 1.0417.

2

STYX WATER WAS HYDROFLUORIC ACID

Hydrogen fluoride is used in separating the isotopes of boron. “The fractionated vacuum distillation of the dimethyl ether adduct of boron trifluoride (DME-BF3) of boron trifluoride” is one of the two commercial ways of separating boron-11 from boron-10 (Wikipedia on Boron). Boron trifluoride is manufactured by the reaction of boron oxides with hydrogen fluoride, HF.

The fusion of an ion of boron-11 and a proton releases much energy and very few neutrons. This is called aneutronic fusion(a-neutronic means “no neutrons”).

Aneutronic fusion is the only practicable source of energy for powering an interstellar ship. Most importantly the energy released by aneutronic fusion is carried by the positively charged end products (helium-4 ions) and be converted directly to electrical energy with high efficiency and therefore without the need to radiate huge quantities of waste heat into space from gigantic radiators. Because energy is not lost as heat much less fuel needs to be carried by the ship. And the lack of neutrons reduces the mass of shielding needed to protect the crew from radiation.

The ancient Greek author Pausanias recorded that the water of the river Styx had “wonderful properties” (Pausanias, Description of Greece, 8.18.4,5):

“… χρόνῳ δὲ ὕστερον ἐγνώσθη καὶ εἰ δή τι ἄλλο πρόσεστι τῷ ὕδατι τῶν ἐς θαῦμα ἡκόντων.

αλος μέν γε καὶ κρύσταλλος καὶ μόρρια καὶ ὅσα ἐστὶν ἀνθρώποις ἄλλα λίθου ποιούμενα καὶ τῶν σκευῶν τὰ κεραμεᾶ, τὰ μὲν ὑπὸ τῆς Στυγὸς τοῦ ὕδατος ῥήγνυται: κεράτινα δὲ καὶ ὀστέινα σίδηρός τε καὶ χαλκός, ἔτι δὲ μόλιβδός τε καὶ κασσίτερος καὶ ἄργυρος καὶ τὸ ἤλεκτρον ὑπὸ τούτου σήπεται τοῦ ὕδατος. Τὸ δὲ αὐτὸ ἐν μετάλλοις τοῖς πᾶσι καὶ ὁ χρυσὸς πέπονθε: καίτοι γε καθαρεύειν γε τὸν χρυσὸν ἀπὸ τοῦ ἰοῦ ἥ τε ποιήτρια μάρτυς ἐστὶν ἡ Λεσβία καὶ αὐτὸς ὁ χρυσὸς ἐπιδείκνυσιν.

http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0159%3Abook%3D8%3Achapter%3D18

The translation into English below by H S Jones is serviceable enough except that he mistranslates the last couple of lines by saying that under the action of Styx water “gold suffers just like all the other metals”. The Greek word that Jones translates as “suffers” is καθαρεύειν which means “to be clean or pure”; καθαρεύειν is a form of καθαρός  “physically clean, spotless”.

Translation by Jones: “ … later on all the wonderful properties of the water were learnt. For glass, crystal, murrhine vessels, other articles men make of stone, and pottery, are all broken by the water of the Styx, while things of horn or of bone, with iron, bronze, lead, tin, silver and electrum, are all corroded by this water. Gold too suffers just like all the other metals, and yet gold is immune to rust … ” (Pausanias, Description of Greece, 8.18.4,5, translated by H S Jones).

These are the properties of hydrogen fluoride dissolved in water. (In fact gold is not dissolved by hydrofluoric acid; this is a slight misunderstanding by Pausanias.) “Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. Solutions of HF are colourless, acidic and highly corrosive”. “Elemental fluorine is produced from it. It is commonly used to etch glass and silicon wafers. When hydrofluoric acid comes into contact with human skin it causes deep burns”.

“Because of its ability to dissolve iron oxides as well as silica-based contaminants, hydrofluoric acid is used in pre-commissioning boilers that produce high-pressure steam” (Wikipedia on Hydrofluoric acid).

In other words, hydrofluoric acid is used to make iron or steel boilers “physically clean” by removing rust (iron oxides) and silicates; it makes them καθαρός. Hydrofluoric acid would also remove inclusions of quartz (silicon dioxide) from gold nuggets, making the gold “physically clean”.

“Hydrofluoric acid is also useful for dissolving rock samples (usually powdered) prior to analysis. In similar manner, this acid is used in acid macerations to extract organic fossils from silicate rocks. Fossiliferous rock may be immersed directly into the acid, or a cellulose nitrate film may be applied (dissolved in amyl acetate), which adheres to the organic component and allows the rock to be dissolved around it” (Wikipedia on Hydrofluoric acid).

Styx means “hateful”.“Στύξ στυγέω“the Styx, i. e. the hateful, a river of the nether world, by which the gods in Homer swore their most sacred oaths” (Henry George Liddell, Robert Scott, An Intermediate Greek-English Lexicon).

3

THE HUGE TREE THAT HELD UP THE SKY

Scandinavian, Indian and Chinese myths speak of an enormous tree in the North that supported a solid sky and provided a way for Earth-people to visit the “Sky-people” living far above them.

But this was not a tree: it was a huge tube forming the central axis of a ground base built by the crew and robots of the big interstellar ship Strider. The tube was like a tethering post for the hovering Strider.

As well as its electrically powered thruster Strider was equipped with electrically driven, vertically rotating propellers and many electrically driven horizontally rotating propellers. These enabled the ship to leave low-Earth orbit by decreasing its velocity and gradually lowering its altitude until it was hovering about 100 metres above the ground.

The ship lowered some of its crew to the ground where they used three-dimensional manufacturing equipment to make a huge tube of fused silica 100 metres long and 3 metres in diameter. The energy used to melt the silica was supplied by an electrical cable lowered from the ship, which had great generating capacity. The tube was manufactured on Earth instead of carrying it from the home planet; this was done to reduce the loaded mass of the ship on its departure.

The tube had a door at one end and a locking-ring or “dock” at both ends, one of which matched a dock fixed in the ground by the crew and the other matched a dock in the ship. While Strider hovered it lifted one end of the tube until it was standing vertically. The end with the door was locked into the dock in the ground and the other end was locked into the dock in the ship. This was the first step in establishing a base for the ship and crew.

The tube was made of fused silica because silica is a common mineral which can be found almost pure on some beaches. Fused silica is strong and fairly light.

“Because of its physical strength, fused quartz was used in deep diving vessels such as the bathysphere and benthoscope and in the windows of crewed spacecraft, including the Space Shuttle and International Space Station”,

“Density: 2.203 g/cm3

Hardness: 5.3–6.5 (Mohs scale), 8.8 GPa

Tensile strength: 48.3 MPa

Compressive strength: > 1.1 GPa

Bulk modulus: ~37 GPa

Rigidity modulus: 31 GPa

Young’s modulus: 71.7 GPa

Poisson’s ratio: 0.17” (Wikipedia on Fused quartz).

The huge tube did not support the ship: Strider supported itself by reacting air downward with its horizontally rotating propellers and so generated enough lift to pull gently upward on the tube, putting it under slight tension. The ship was kept precisely in position in three dimensions by computerised station-keeping software which controlled its horizontally rotating and vertically rotating propellers independently.

A tube 100 metres tall allowed enough room for the vertical downflow of air from the horizontal propellers of the ship to change to a more horizontal flow and escape along the surface of the ground without obstruction.

Supplies and fuel were uplifted inside the tube, and crew, robots, machines and chemicals were let down and lifted up through it.

The huge tube with Strider settled on top of it looked like a tree: the tube was the trunk and the ship with its framework of supports for its many horizontal “hover propellers” was the crown of the tree with its many branches. The ship was about 100 metres in diameter.

Much of the work at this first base station was to use additive manufacturing equipment to make machines and devices that were too big or heavy to load on Strider at its home planet. This equipment can make metal parts from design information stored in computer programs. The quality of the parts is equal to or better than that of parts manufactured by traditional methods.

An ideal location for the station would have been in a cool temperate climate, near a beach of pure, or nearly pure, silica (quartz grains) and near surface ores of useful metals including iron, nickel, chromium, copper and aluminium.

Probably a compromise had to be reached by choosing a site where at least several of the ores were nearby. The ores had to be at the surface of the Earth because the crew of Strider could not do underground mining. There were not many of them and the machines they manufactured were fairly small. They did not need big quantities of metals and fluorite.

The things they manufactured included earth-movers, rock-crushers, metal smelters, electrolytic ore-refiners, small chemical plants and building and roofing materials. Electric motors for the machines were carried by Strider as part of its payload.

Other bases were established later in widely separated locations as Strider searched for and loaded various minerals and supplies. It carried the huge tube with it when it moved to another site so these sites could be inland ones. They did not have to be near a silica beach. There are rich mineral deposits at several sites in North America.

Before Strider reached its destination the Earth had been surveyed and explored by the small uncrewed surveyor ships called Dashers, which detected the resources that would be needed by Strider during its stay here and for the Arrow’s return voyage to its home planet, including boron and reaction-mass. Several Dashers were sent to Earth in various decades. The information they gathered was sent to their home planet and used to plan the itinerary of Strider when it reached Earth. If the distance from Earth to the home planet were, for example, five light years it would take five years for information to travel from Earth to the home planet. And it would take five years for information to travel from the home planet to the Dashers and Strider.

4

WHERE WAS STRIDER’S HOME PLANET?

Wikipedia lists about 13 stars within 10 light years of Earth and shows their planets (if any) and refuted planets.

The interstellar ship Daedalus was designed in the 1970s by members of the British Interplanetary Society to go to and fly past Barnard’s Star, 5.9629 light years away.

“Daedalus would be constructed in Earth orbit and have an initial mass of 54,000 tonnes including 50,000 tonnes of fuel and 500 tonnes of scientific payload. Daedalus was to be a two-stage spacecraft. The first stage would operate for two years, taking the spacecraft to 7.1% of light speed (0.071 c), and then after it was jettisoned, the second stage would fire for 1.8 years, taking the spacecraft up to about 12% of light speed (0.12 c), before being shut down for a 46-year cruise period” (Wikipedia on Project Daedalus).

The designers believed that the citizens of Earth would not be interested in supporting preparations for a voyage that would not be completed within their lifetimes, and this was probably a relevant consideration in the design of Strider. The scientifically advanced inhabitants of its home planet would have succeeded in extending their lifetimes to 200 years or more so they would have accepted a voyage duration of about 100 years.

Wikipedia says Barnard’s Star has only one (refuted) planet so it can be eliminated.

Wikipedia shows three stars in the system Alpha Centauri. Of these Rigel Centaurus, designated Alpha Centauri A, at a distance of 4.3441 light years, has one directly imaged habitable-zone planet candidate (candidate 1).

“Alpha Centauri B has no known planets: planet Bb, purportedly discovered in 2012, was later disproven, and no other planet has yet been confirmed” (Wikipedia on Alpha Centauri).

The hypothetical Daedalus was criticised for being too massive; its unladen mass was 3,500 tonnes. It did not decelerate and enter low Earth orbit: it flew past Earth at 12 percent of the speed of light. And it required 50,000 tonnes of fuel of which only 17 percent was fused; the rest simply acted as reaction mass and, being of low atomic weight, was less efficient than an element of greater atomic weight, such as iodine. The fuel mix of Daedalus, hydrogen-2 + helium-3 was more energy dense than that of Strider, but helium-3 is impossible to get in large quantities.

We propose that the unladen mass of Strider was about 400 tonnes and its payload was kept as small as possible. Its payload included essential machines and plant to be used on arrival to make on Earth more machines and building materials by smelting and additive manufacturing. It had accommodation for the 30 or 40 living intelligent beings transferred to it from Arrow, providing them with living quarters and preserved food and water before fresh food could be grown on Earth.

In comparison the mass of the International Space Station (which  of course is not an interstellar ship) is 420 tonnes.

Strider’s work on Earth was to carry earth-moving and loading machinery to the sites of various minerals, upload them and take them to processing plants at suitably equipped base stations.

This book assumes that the home planet orbits Alpha Centauri A, Rigel Centaurus. It assumes that the smaller ships cruised at 10 percent of the speed of light and their voyages lasted 45 years. And it assumes that the bigger, heavier Strider cruised at 5 percent of the speed of light and its voyage to Earth lasted 90 years; this slower cruising speed cut its required mass of fuel and reaction mass to a quarter of what it would have been if it cruised at 10 percent of the speed of light.

Before Arrow departed from its home planet it was prudent to wait until confirmation had been received from Strider that it had safely decelerated and entered a stable low Earth orbit with its fusion-powered generators now in low-power mode. This information would have taken 4.5 years to go from Strider to the home planet; when it arrived the Arrow, with its living passengers in suspended animation, departed. It docked with Strider, which had then been in low Earth orbit for 4.5 years, about 95 years after Strider had departed. The passengers were reanimated by robots, transferred themselves to Strider and took control of it.

5

MYTHS ABOUT THE WORLD TREE

The Ash Tree that Reached Heaven

The Scandinavian world tree was called Yggdrasil. “Yggdrasil is an immense ash tree that is centre to the cosmos and considered very holy. The gods go to Yggdrasil daily to assemble at their things, traditional governing assemblies. The branches of Yggdrasil extend far into the heavens, and the tree is supported by three roots that extend far away into other locations” (Wikipedia on Yggdrasil).

The ash tree is in the genus Fraxinus. “The seeds, popularly known as ‘keys’ or ‘helicopter seeds’, are a type of fruit known as a samara” (Wikipedia on Fraxinus). The humans who saw the ship Strider hovering on top of the huge tube, with its horizontal propellers whirring, thought that the propeller blades resembled the rotating “helicopter seeds” of an ash tree. Each ash seed is attached to a single “propeller blade” which makes it rotate as it falls from the ash tree.

The Chinese Tree of Heaven

“In some other versions, the sky ladder is a huge tree. The most noted tree sky ladder in ancient writings is Jianmu (literally meaning ‘Building Tree’). According to an account in Huainanzi, Jianmu grew in the field of Duguang. With it, the gods went up and down between heaven and earth. At midday it had no shadow; shouting to it, there was no echo. Some suggest that perhaps it was the centre of the world. In another text in Shanhaijing, Jianmu was an enormous tree with a height of 800 feet. It had no branches in the middle, only twigs curled on the top and roots twisted and gnarled. Its fruit was like the seeds of hemp, and its leaves were like those of the Mang tree” (Handbook of Chinese Mythology, by Lihui Yang and Deming An with Jessica Anderson Turner).

Chinese 建木, jiànmù is composed of jiàn “to establish / to found / to set up / to build / to construct … build, establish, erect, found” and mù “tree; wood, lumber; wooden” (MDBG Chinese Dictionary). This proves that this so-called Tree was a built thing, an erected thing. It was artificial.

Note that 800 feet is a wrong translation in the context of the ancient myth. The Chinese word translated as “foot” is chi.

 Chinese length units promulgated in 1915 include the chi with a metric value of 0.32 metre and an imperial value of 12.6 inches. This length was made as part of a modern move to join the international metric system.

But the appropriate value to use in translating chi in a myth thousands of years old is the oldest recorded value, which was the value in the Shang dynasty beginning 1600 years BC. This value was 0.1675 metre (Wikipedia on Chinese units of measurement).

0.1675 multiplied by 800 = 134 metres. This value of 134 metres is not much greater than the 100 metres of height of the huge tube above which Strider hovered.   

An East Asian Tree of Heaven

There is another notable tree with “helicopter seeds” in mythology: the “Tree of Heaven”, Ailanthus altissima. It is similar in some ways to the ash tree and therefore to the Scandinavian world tree called Yggdrasil.

“Ailanthus altissima, commonly known as tree of heaven, ailanthus, varnish tree, or in Chinese as 臭椿, pinyin chòuchūn, is a deciduous tree in the family Simaroubaceae. It is native to northeast and central China, and Taiwan”.

“The fruits grow in clusters; similar to the Ash (Fraxinus excelsior); the fruits ripen to a bright reddish-brown color in September. A fruit cluster may contain hundreds of seeds. The seeds borne on the female trees are 5 mm in diameter and each is encapsulated in a samara that is 2.5 cm long and 1 cm broad, appearing July through August, but they can persist on the tree until the next spring. The samara is large and twisted at the tips, making it spin as it falls, assisting wind dispersal”.

“The [genus] name is derived from the Ambonese word ailanto, meaning ‘heaven-tree’ or ‘tree reaching for the sky’ ” (Wikipedia on Ailanthus altissima).

Some of the crew of Strider would have travelled in small hover-aircraft with horizontally rotating propellers as they explored parts of planet Earth. These propellers looked like the spinning samaras of Ailanthus and the spinning keys  or “helicopter seeds”of the Ash (Fraxinus excelsior).

6

THE HYPERBOREANS

The crew living in Strider above the huge tube were called by the ancestors of the Greeks the Hyperboreans, which means “Above Boreas”. Hyper means “above” or “beyond”. Boreas means “the North wind” and the name is probably derived from oros, “wind from the mountains”.

“Βορέας Prob. from ὄρος, ϝόρος, wind from the mountains” (Henry George Liddell, Robert Scott, An Intermediate Greek-English Lexicon).

A dome of glass 50 metres tall and 100 metres in diameter was built up round the tube by the printing of molten glass by a three-dimensional additive-printer on a telescopic beam, which was fitted to the tube and rose up it and slowly rotated as it “printed” the dome.

Sodium carbonate serves as a flux for silica, lowering the melting point of the mixture. This “soda glass” is mildly water-soluble, so some calcium carbonate is added to the melt mixture to make the glass insoluble. Bottle and window glass (soda-lime glass) is made by melting mixtures of sodium carbonate, calcium carbonate, and silica sand. The crew would have needed sodium carbonate and silica to make an easily melted glass for three-dimensional printing of the dome. Sodium carbonate can be got from the ash of kelp seaweed and from trona, a deposit in some dry lakes.

The downward rush of air from the horizontal propellers of Strider would be like a “wind rushing down a mountain”, because the tube stood as the vertical axis of the glass dome, which was like a small mountain. In some myths this small mountain was given a name which means “crystal”: glass looks like clear crystal.

And so the crew of Strider lived “above the wind (from the mountain)”: they were the Hyperboreans.

This hollow glass dome became known in Indian mythology as Mount Meru or Mount Kailash, and in Chinese mythology as Kunlun Mountain.

“Mount Kailash (also Kailasa . . . is a 6,638 metre (21,778 foot) high peak in the Kailash Range (Gangdisê Mountains), which forms part of the Transhimalaya in the Ngari Prefecture, Tibet Autonomous Region, China.

“The mountain is located near Lake Manasarovar and Lake Rakshastal, close to the source of some of the longest Asian rivers: the Indus, Sutlej, Brahmaputra, and Karnali also known as Ghaghara (a tributary of the Ganges) in India. Mount Kailash is considered to be sacred in four religions: Hinduism, Bon, Buddhism, and Jainism . . .

“The mountain is known as Kailāsa in Sanskrit. The name also could have been derived from the word kelāsa, which means ‘crystal’ . . .

“Mount Kailash is believed to be the Axis Mundi, also known as the cosmic axis, world axis, world pillar, centre of the world, the world tree. It is the point where heaven meets earth” (https://timesofindia.indiatimes.com/travel/destinations/mount-kailash-facts . . . ).

“The term Kunlun may be semantically related to two other terms: Hundun (Chinese: 混沌; pinyin: hùndùn; Wade–Giles: hun-t’un; lit. ‘primal chaos’ or ‘muddled confusion’), which is sometimes personified as a living creature; and kongdong (Chinese: 空洞; pinyin: kōngdòng; Wade–Giles: k’ung-t’ung; lit. ‘grotto of vacuity’), according to Kristofer Schipper. Grotto-heavens were traditionally associated with mountains, as hollows or caves located in/on certain mountains. The term ‘Kunlun Mountain’ can be translated as ‘Cavernous Mountain,’ and the mythological Kunlun Mountain has been viewed as a hollow mountain (located directly under the pole star)” (Wikipedia on Kunlun {mythology}).

“Despite their location in an otherwise frigid part of the world, the Hyperboreans were believed to inhabit a sunny, temperate, and divinely blessed land. In many versions of the story, they lived north of the Riphean Mountains, which shielded them from the effects of the cold North Wind. The oldest myths portray them as the favourites of Apollo, and some ancient Greek writers regarded the Hyperboreans as the mythical founders of Apollo’s shrines at Delos and Delphi” (Wikipedia on Hypoborea).

This “sunny, temperate land” was inside the glass dome surrounding the huge tube described above.

The crew of Strider erected this glass dome round the huge tube because the location was in “the frigid north” and because it would protect crew on the ground from the constant down-rush of wind from the horizontal propellers of the ship, and would act as a greenhouse where crops could be gown in winter, though it would have to be ventilated in summer. It would keep dangerous animals away from the crew. And if it were closed to provide a fully sealed atmosphere (ventilated through filters) it would protect the crew from viruses and bacteria against which they had no immediate immunity.

To give an idea of the scale of the dome, it was about the same height as a 17-storey building. (For comparison the biggest transparent dome in the Eden Project, Cornwall, UK is 55 metres tall and 100 metres wide.)

This transparent dome was the “solid”, or apparently solid, sky in some of the myths about the world tree.

“Pindar, a contemporary of Herodotus, also described the otherworldly perfection of the Hyperboreans:

“Never the Muse is absent

from their ways: lyres clash and flutes cry

and everywhere maiden choruses whirling.

Neither disease nor bitter old age is mixed

in their sacred blood; far from labour and battle they live”

(Wikipedia on Hyperborea).

“In Greco-Roman geography, the Riphean Mountains were a supposed mountain range located somewhere in the far north of Eurasia. The name of the mountains is likely derived from Greek ῥιπή ‘wind gust’. The Ripheans were often considered the northern boundary of the known world. As such, classical and medieval writers described them as extremely cold and blanketed in perpetual snow. Many ancient geographers identified the Ripheans as the source of Boreas (the North Wind) and several large rivers (the Dnieper, the Don, and the Volga)” (Wikipedia on Riphean Mountains).

7

BUILDING STRIDER FOR ITS VOYAGE TO EARTH

Now we consider how Strider was built and how hundreds of tonnes of fuel and reaction-mass were loaded for the outward voyage to Earth from the home planet. Because of the bulky nature of some of the plant and equipment to be carried, including the Scout plane, it would have to be loaded on Strider while the ship was still on the frame on which it was built. It would not fit into a spaceplane.

An intelligent, technically proficient, peaceable species of living being, one that had invented machines to fuse ions of hydrogen-1 and boron-11, and had built ships to visit other planets of their star, would have the knowledge and the economic power to build Strider in the following way.

Strider was built from components manufactured in factories at ground level. The components were assembled on top of an open frame standing on the ground and 100 metres tall; they were lifted into position by cranes attached to the frame. When fully assembled the ship was loaded with some of the essential plant and equipment needed on Earth (the rest was made later on Earth by additive manufacturing), a small mass of fuel and a small mass of reaction-mass for the thruster.

Strider then lifted itself upward and forward toward a low planet orbit with an elevation of about 100 kilometres using electrical power generated on board to power its horizontally and vertically rotating propellers or fans while the atmosphere was dense enough for them to work, and then the electrical thruster to accelerate it to orbital velocity, which opposes the force of gravity; once in orbit the ship used very little power to stay in orbit.

The horizontally and vertically rotating propellers and the ship’s thruster were capable of lifting and accelerating the ship and its cargo and a small mass of fuel from the top of the 100-metre open frame to the 100-kilometre orbit. The open frame allowed the air from the propellers to flow downwards and sideways and so escape.

8

LOADING STRIDER FOR ITS VOYAGE TO EARTH

The cost of getting a tonne of anything to the present International Space Station above Earth is very great, the amount that can be carried to it with each “lift” is small and the time spent on each lift is considerable.

The vehicles used to do the job have been expendable chemically fuelled rockets; the reusable Space Shuttles, which were lifted to orbit by chemically fuelled rockets and had wings so they could land like an aeroplane; and more recently chemically fuelled rockets with a returnable first stage, which have reduced the cost considerably.

A different kind of vehicle was used to load Strider. It was similar to the Skylon spaceplane.

“Skylon is a series of concept designs for a reusable single-stage-to-orbit spaceplane by the British company Reaction Engines Limited (Reaction), using SABRE, a combined-cycle, air-breathing rocket propulsion system. The vehicle design is for a hydrogen-fuelled aircraft that would take off from a purpose-built runway and accelerate to Mach 5.4 at 26 kilometres altitude (compared to a typical airliner’s altitude of 9–13 kilometres) using the atmosphere’s oxygen before switching the engines to use the internal liquid oxygen (LOX) supply to take it into orbit.

“It could carry 17 tonnes of cargo to an equatorial low Earth orbit (LEO); up to 11 tonnes to the International Space Station, almost 45 percent more than the capacity of the European Space Agency’s Automated Transfer Vehicle; or 7.3 tonnes to Geosynchronous Transfer Orbit (GTO), over 24 percent more than the SpaceX Falcon 9 launch vehicle in reusable mode (as of 2018).

“The relatively light vehicle would then re-enter the atmosphere and land on a runway, being protected from the conditions of re-entry by a ceramic composite skin. When on the ground, it would undergo inspection and necessary maintenance, with a turnaround time of approximately two days, and be able to complete at least 200 orbital flights per vehicle” (Wikipedia on Skylon).

“A truly versatile propulsion system, SABRE is an air-breathing rocket engine that can propel an aircraft from zero to five times the speed of sound in the atmosphere and 25 times the speed of sound for space access . . . The SABRE engine design aims to avoid the historic weight-performance issue by using some of the liquid hydrogen fuel to cool helium within a closed-cycle precooler, which quickly reduces the temperature of the air at the inlet” ((https://www.reactionengines.co.uk/beyond-possible/sabre ).

Skylon is a spaceplane and uses its wings to gain altitude by reacting a large mass of air downward, so it makes more efficient use of fuel than a simple rocket; and it uses oxygen in the air to burn its hydrogen fuel for the first part of its ascent. When there is not enough oxygen in the  atmosphere it uses liquid oxygen carried on board.

We saw above that Skylon could carry 11 tonnes to the International Space Station, which orbits the Earth at an average altitude of 400 kilometres, and 17 tonnes to a lower Low Earth Orbit at an average altitude of (presumably) 200 kilometres, at which the mean orbital velocity needed to maintain a stable orbit is 28,000 kilometres per hour.

Spaceplanes Like Skylon

The lower the altitude of the destination orbit the greater the payload of the spaceplanes can be, but the lower the orbit of the ship the greater will be the atmospheric drag and heating upon it and the spaceplanes loading it. The Earth’s atmosphere hardly exists above 90 kilometres altitude; for international legislation “Space” is regarded as the region above 100 kilometres altitude. If the home planet of Strider were about the same size and mass as Earth and its atmosphere were similar there would be very little atmosphere above 100 kilometres altitude.

Strider was able to remain stable in a very-low-planet orbit at about 100 kilometres altitude which made it much easier to load than if it orbited at 400 kilometres.

At 100 kilometres altitude Strider had to use its thruster a little to accelerate it when atmospheric drag slowed it a little and it needed a heat-resistant “skin” to withstand the effect of atmospheric heating, but these effects were small and the thruster did not use much fuel-and-reaction-mass to oppose the drag. The ship, 100 metres in diameter, was streamlined as far as practicable to reduce drag.

(The International Space Station does have to boost its velocity regularly to overcome the small effects of atmospheric drag but does not suffer from atmospheric heating).

Spaceplanes like Skylon were needed to load hundreds of tonnes of fuel and reaction-mass on Strider in an orbit of 100 kilometres altitude. If each spaceplane had a payload of 17 tonnes, many flights had to be flown to do the loading. Skylon was designed to be capable of making 200 flights so two or three similar spaceplanes might have been needed.

Each spaceplane had to dock with Strider in turn at the ship’s orbital speed to transfer fuel-and-reaction-mass to it, but of course their speeds relative to each other were then almost zero. They gave orbital velocity and orbital altitude to the hundreds of tonnes of fuel, reaction-mass and equipment they loaded onto the ship. Strider did not have to do this, and could not have done it.

The home planet’s infrastructure supplied cheap liquid hydrogen and liquid oxygen to spaceplanes by using electricity to separate water molecules into oxygen molecules and hydrogen molecules. The electricity was very cheap.

It had the infrastructure and the great economic strength to do all this, gained largely by the use of aneutronic fusion-powered generators at ground level supplying electrical power to its factories, the products of its quarries, city buildings, homes, chemical plants, metal-ore electrolysing plants, water-distilling plants, water electrolysing plants, trains, ships and aircraft.

9

DESIGNS OF THE SHIPS

Design of a Dasher: These surveyor ships were small, unmanned and had a variety of imaging and sensing equipment, miniaturised like our CubeSats (which are the size of a shoe box), to gather the information that Strider needed. At intervals they travelled at 10 percent of the speed of light from their home planet to Earth. They did not return to their home planet.

The images and information they gained were sent back to their home planet and to Strider. Some of the more interesting images were shown on mainstream consumer television “back home”.

It would have been possible for Dashers to use helium-3 + helium-3 as fuel; this would have reduced the mass of fuel needed compared to that of a Dasher using hydrogen-1 + boron-11 and so reduced the time spent in accelerating and decelerating.

Helium-3 can be manufactured by making hydrogen-3 (tritium) and waiting for it to decay to helium-3. The half-life of tritium is less than 13 years. (The first generation of neutronic fusion powered generators of electricity will manufacture their own tritium.)

The myths with which this essay begins show that fusion of hydrogen-1 + boron-11 was achieved by the inhabitants of a planet in orbit round a nearby start. It would be possible to fuse helium-3 + helium-3 because the latter reaction is not as difficult as the former. But the slow, complicated process of manufacturing helium-3 would not have worth doing even for such small, light, very fast interstellar ships as the Dashers. They used hydrogen-1 + boron-11.

Design of Arrow: This small passenger express was designed to carry to Earth at 10 percent of the speed of light a crew of about 40 intelligent, highly educated and trained living beings who travelled in a state of suspended animation. The voyage lasted about 45 years. Arrow docked with Strider after both ships had entered a low Earth orbit.

The intelligent beings were then reanimated by robots and took control of Strider. This control by living intelligent beings was necessary because robots controlled by their own artificial intelligence would have lacked the ability to adapt to unexpected circumstances on Earth.

Arrow was designed to uncouple from Strider at the end of the mission to Earth and return to its home planet with its intelligent living beings once again in a state of suspended animation. They were restored to full conscious animation when they reached home.

Arrow  was the only ship to return home and therefore the only ship that had to be fully refuelled on Earth, though a small amount of fuel would also be stored in Strider’s tanks to enable it to rise to low Earth orbit and then accelerate to escape velocity. The fuel had to be manufactured on Earth, lifted up to Strider through the huge tube and transferred to Arrow.

A source of a suitable mineral of boron had to be found, preferably boric acid, which is free of sodium. Natural boron is composed of two isotopes, boron-10 and boron-11. They had to be separated and the boron-11 had to be lifted up to the hovering Strider and transferred to Arrow.

Boron minerals are found in many parts of the world; there are big deposits in California, USA, Turkey, South America and elsewhere. A suitable boric acid mineral called sassolite occurs in Italy, Nevada, USA and some other places.

Arrow was bigger and heavier than a Dasher but just as quick.

Design of Strider: This freighter ship, about 100 metres in diameter, was much bigger and more massive than the Dashers and the Arrow. If it were to accelerate to a cruising velocity 10 percent of the speed of light it would need a great mass of fuel and reaction mass.

A population living in a highly advanced civilisation on a planet about five light years from Earth would probably wish the voyage to be accomplished in their lifetimes. We assume that intelligent beings capable of sending an interstellar ship to Earth from their home planet would have been able to extend their lifetimes to two or three hundred years, and would accept a duration of 100 years for Strider’s voyage.

The ship’s mission to Earth involved few activities to keep its designers, its builders and the planet’s citizens interested during the prolonged cruise period. But Strider began sending audio, video and data back to its home planet soon after it arrived at Earth, compensating its builders for their efforts with images of the landscapes, seascapes, plants and animals of Earth.

Strider had to carry fuel, robots, light helicopters, the small supersonic aeroplane Scout, metal smelting and refining plant and additive manufacturing equipment to make buildings, heavy plant and machinery from ores found on Earth. On its voyage it was controlled only by robots and computers.

The tanks and bins used to hold fuel and reaction-mass in Strider were not jettisoned after being emptied, because they were designed to serve a second purpose of providing accommodation for crew, machinery and processing-plant on Earth.

A bin holding solid iodine as reaction mass might have been designed to become a small sea-going vessel or floating platform.

Boron is a solid with a very high melting temperature and so could be stored in bins. Hydrogen is a gas at typical Earth temperatures and would have to be liquified by refrigeration before being stored in spherical  or cylindrical tanks. The temperature of space is generally very low so the hydrogen would remain liquid without refrigeration during most of the voyage, but some refrigeration equipment would have to be carried by Strider to keep liquid the small amount of hydrogen remaining when the ship arrived at Earth and to liquify the hydrogen needed for the return voyage by the Arrow.

Strider and the other ships generated electrical power from energy released by the aneutronic fusion of a magnetically confined plasma of hydrogen-1 and boron-11 in a closed chamber.

When boron-11 is struck by a proton [a positively charged ion of H-1] with energy of about 500 keV, it produces three alpha particles and 8.7 MeV of energy (Wikipedia on Boron). An alpha particle is an ion of helium-4. The three alpha particles are positively charged, and so their kinetic energy can in principle be directly converted into electrical energy.

Strider used this power to eject reaction-mass at very high velocity through electrical or electromagnetic thrusters. The reaction-mass included the products of fusion (each fusion event produces three ions of helium-4) and also a non-toxic element with high atomic mass that was not involved in fusion reactions but was simply accelerated backward from the ship. In  accordance with Newton’s principle that “to every action there is an equal and opposite reaction”, the ship was accelerated forward.

To decelerate the ship as it approached Earth the reaction-mass was accelerated forward.

Design of Scout: This small supersonic aeroplane was designed to take four specialists to sites on Earth which the Dashers in low Earth orbits had detected as possible sources of necessary supplies or locations of interesting animals and plants. It had to be small and light because it was part of the cargo that had to be carried from the home planet by Strider. It was a VTOL (vertical take-off and landing) aeroplane which could travel long distances at supersonic speed, hover above interesting sites and land vertically at the most interesting ones. It had a small cargo hold for food, drink, cameras, tools, clothing, and samples of rocks and brines.

Scout was an essential aeroplane because, when it comes to the task of selecting from many promising sites the best one at which to dig or drill, no inanimate instrument, device or artificial intelligence is as good as a seasoned geologist with his boots on the ground, his hammer in his hand and his hat on his head.

Scout searched for metal ores in many countries, for boric acid in Iceland, Italy, Turkey, North America and South America and for kelp seaweed and whales in cold northern seas. Its supersonic flight halved travel times compared with those of a subsonic aeroplane.

It was seen by the inhabitants of South America when its crew examined sodium nitrate deposits in the deserts of Chile for the presence of iodine. Perhaps its manoeuverings and its supersonic booms in the skies of Chile stimulated the local people to compose myths which were given pictorial expression thousands of years later in the mysterious artworks on the surface of the Atacama Desert.

“The Atacama Giant (Spanish: Gigante de Atacama) is an anthropomorphic geoglyph on the Cerro Unitas area of the Atacama Desert, Chile. At about 119 meters (390 feet), it is the largest prehistoric anthropomorphic geoglyph … The Atacama Giant is one out of nearly 5,000 geoglyphs (ancient artworks that are drawn into the landscape) that have been discovered in the Atacama region in the last three decades” (Wikipedia on Atacama Giant).

10

CHOOSING THE REACTION-MASS

For efficiency in propulsion the reaction-mass must be an element that is easy to ionise and has a high atomic mass. But there other important considerations: it must be non-toxic, not too expensive on the home planet and easily accessible on Earth. For example, mercury has been used in small electric-propulsion thrusters on some satellites; it is easy to ionise and it has a high atomic mass. But many compounds of mercury are highly toxic, so it would be unacceptable for an interstellar ship decelerating close to Earth to eject tonnes of mercury ions at extremely high velocity toward Earth’s atmosphere.

Xenon has also been used in electric-propulsion thrusters but is neither cheap nor easily accessible on Earth, where it is found in the atmosphere in trace amounts. Several other elements have been used as reaction-mass in low-powered applications such as satellites, including the gases krypton and argon, the metals caesium, indium, rubidium and gallium and the halogen iodine.

Iodine is the heaviest of the stable halogens and is a lustrous, purplish-black non-metallic solid at standard conditions (room temperature) that melts to form a deep violet liquid at 114 degrees Celsius, and boils to a violet gas at 184 degrees Celsius. An interstellar ship accelerating to or decelerating from cruising velocity by ejecting iodine as the reaction-mass would leave a very long violet vapour-trail behind it. At thousands of kilometres a second.

Most of the reactions of iodine involve capturing an electron and becoming negatively charged. Iodine can also give up an electron and become positively charged. These characteristics make it possible to eject iodine plasma from a thruster using electromagnetic waves and/or magnetic fields or electric fields.

Iodine as Reaction-mass

Iodine might seem an unusual choice for the reaction-mass in an interstellar ship but it satisfies two requirements: the element must be non-toxic and a small crew with limited mechanical and chemical-processing resources must be able to find a source of the element (which is usually in compound form) on Earth and isolate the element.

Iodine is a solid at normal atmospheric temperatures on Earth and presumably on an Earth-like planet. It could be carried in this compact form by spaceplanes to an orbit round the home planet and could then be stored in bins in Strider. This is a big advantage over normally gaseous reaction-masses such as xenon, krypton and argon, which would have to be refrigerated to liquify them and be stored in huge spherical tanks. Some examples of the present use of iodine in small satellites follow.

American Iodine Satellite

Iodine has been chosen by NASA and the US Air Force as the reaction-mass in a proposed small satellite, a 12U CubeSat format, with dimensions of about 200 mm by 200 mm by 300 mm.

“Iodine Satellite (iSat) is a technology demonstration satellite of the CubeSat format that will undergo high changes in velocity from a primary propulsion system by using a Hall thruster with iodine as the propellant”.

“A key advantage to using iodine as a propellant is that it provides a high density times specific impulse, it is three times as fuel efficient as the commonly flown xenon, it may be stored in the tank as an unpressurized solid, and it is not a hazardous propellant … During operations, the tank is heated to vaporize the propellant. The thruster then ionizes the vapor and accelerates it via magnetic and electrostatic fields, resulting in high specific impulse”.

“The iodine thruster will allow iSat to alter its orbital inclination and elevation, opening up a wider range of mission objectives than previously possible with spacecraft of this size, such as transferring from a geosynchronous orbit to geostationary orbit, entering and managing lunar orbits, and to be deployed to explore near Earth asteroids, Mars and Venus” (Wikipedia on Iodine Satellite).

European Iodine Satellite

A Beihangkonshi-1 small satellite altered its orbit using iodine as a propellant in January 2021 using a self-contained NPT30-I2 electric iodine propulsion system developed by the French company Thrustme.

Thrustme is a spin-off company from the École Polytechnique and the French National Centre for Scientific Research (CNRS). With the support of the European Space Agency (ESA) it has developed a modular ion thruster system that is smaller and simpler than conventional systems.

The power of the electric iodine thrusters in these small satellites is miniscule compared with the power needed to accelerate an interstellar ship to cruising speed, but the successful development of the small thrusters indicates that extremely powerful iodine thrusters could be developed.

Iodine and Human Health

Iodine in small concentrations would be a benign addition to the Earth’s atmosphere and rain, because it would tend to correct deficiencies in large areas of land used for growing food and feed.

“Iodine deficiency is a lack of the trace element iodine, an essential nutrient in the diet. It may result in metabolic problems such as goiter, sometimes as an endemic goiter as well as congenital iodine deficiency syndrome due to untreated congenital hypothyroidism, which results in developmental delays and other health problems . . .

“Certain areas of the world, due to natural deficiency and unavailability of iodine, are severely affected by iodine deficiency, which affects approximately two billion people worldwide. It is particularly common in the Western Pacific, South-East Asia and Africa. Among other nations affected by iodine deficiency, China and Kazakhstan have begun taking action, while Russia has not” (Wikipedia on Iodine deficiency).

When China began correcting iodine deficiency in the diet of some of its people it obtained iodine from seaweed.

There is a permissible exposure limit of exposure to iodine vapour in the workplace, as is the case for many chemicals. The limit is 0.1 part per million (1 milligram per cubic metre of air) during an 8-hour workday. Few workplaces use iodine or its compounds in their work.

11

GETTING IODINE FROM CHILE CALICHE OR NORTHERN SEAWEED

“Iodide minerals are rare, and most deposits that are concentrated enough for economical extraction are iodate minerals instead. Examples include lautarite, Ca(IO3)2, and dietzeite, 7Ca(IO3)2·8CaCrO4. These are the minerals that occur as trace impurities in the caliche, found in Chile, whose main product is sodium nitrate. In total, they can contain at least 0.02% and at most 1% iodine by mass. Sodium iodate is extracted from the caliche and reduced to iodide by sodium bisulfite. This solution is then reacted with freshly extracted iodate, resulting in comproportionation to iodine, which may be filtered off.

“The caliche was the main source of iodine in the 19th century and continues to be important today, replacing kelp (which is no longer an economically viable source), but in the late 20th century brines emerged as a comparable source. The Japanese Minami Kanto gas field east of Tokyo and the American Anadarko Basin gas field in northwest Oklahoma are the two largest such sources” (Wikipedia on Iodine).

Extracting the trace impurities of iodine from iodate minerals in Chile would require many labourers to work in a chemical processing plant. Perhaps crew members came to a trading arrangement with the indigenous people of or near the Atacama Desert in which they were paid with useful metal objects for their work in extracting iodine from caliche.

Finding and drilling into a gas field that produced iodine-containing brine as well as gas would be impossible for a small crew of interstellar visitors. How would they know which field to drill into? Finding one with iodine would be a one-in-a-million chance.

“In 1811, iodine was discovered by French chemist Bernard Courtois, who was born to a manufacturer of saltpetre (an essential component of gunpowder). At the time of the Napoleonic Wars, saltpetre was in great demand in France. Saltpetre produced from French nitre beds required sodium carbonate, which could be isolated from seaweed collected on the coasts of Normandy and Brittany. To isolate the sodium carbonate, seaweed was burned and the ash washed with water. The remaining waste was destroyed by adding sulfuric acid. Courtois once added excessive sulfuric acid and a cloud of purple vapour rose. He noted that the vapour crystallised on cold surfaces, making dark crystals” (Wikipedia on Iodine). These crystals were solid iodine.

“Giant kelp can be harvested fairly easily because of its surface canopy and growth habit of staying in deeper water.

“Kelp ash is rich in iodine and alkali. In great amount, kelp ash can be used in soap and glass production. Until the Leblanc process was commercialised in the early 19th century, burning of kelp in Scotland was one of the principal industrial sources of soda ash (predominantly  sodium carbonate). Around 23 tons of seaweed was required to produce 1 ton of kelp ash. The kelp ash would consist of around 5 percent sodium carbonate” (Wikipedia on Kelp).

The Hyperboreans lived in the “far north”, where kelp grows well. This essay assumes that they created a glass dome round the trunk of the “huge tree” by additive manufacturing with molten glass. To make glass that was easily melted for use in this three-dimensional printing they needed sodium carbonate.

But this “far north” was not likely to have been north of the Arctic Circle; it was probably between 45 and 55 degrees North latitude. Although much kelp was collected and burned to ash in Scotland in the 19^th century, perhaps between 56 and 58 degrees North Latitude, the main reason for this was the Scottish Clearances, which were “the evictions of a significant number of tenants in the Scottish Highlands and Islands, mostly in the period 1750 to 1860.

“The displaced tenants got alternative tenancies in newly created crofting communities, where they were expected to be employed in industries such as fishing, quarrying or the kelp industry” (Wikipedia on Highland Clearances).

“Kelps are primarily associated with temperate and arctic waters worldwide. Of the more dominant genera, Laminaria is mainly associated with both sides of the Atlantic Ocean and the coasts of China and Japan; Ecklonia is found in Australia, New Zealand, and South Africa; and Macrocystis occurs throughout the northeastern and southeastern Pacific Ocean, Southern Ocean archipelagos, and in patches around Australia, New Zealand, and South Africa. The region with the greatest diversity of kelps (more than 20 species) is the northeastern Pacific, from north of San Francisco, California, to the Aleutian Islands, Alaska” (Wikipedia on Kelp forest).

“Sodium carbonate serves as a flux for silica, lowering the melting point of the mixture. This ‘soda glass’ is mildly water-soluble, so some calcium carbonate is added to the melt mixture to make the glass insoluble. Bottle and window glass (soda-lime glass) is made by melting such mixtures of sodium carbonate, calcium carbonate, and silica sand (silicon dioxide, SiO₂)” (Wikipedia on Sodium carbonate).

Kelp ash contains up to 25 percent potassium chloride, and sodium chloride, sodium carbonate, sodium sulphate, potassium sulphate, potassium iodide and sodium iodide.

A very high iodine content of 2.29 percent in dried seaweed from the Republic of Korea was reported in 2005 by the European Commission Rapid Alert System for Food and Feed; the percentage in ash obtained by burning the dried seaweed would be considerably higher. If this species of seaweed (which was not named in the report) grew in kelp forests it would be an easily accessible and fairly rich source of iodine and sodium carbonate for people skilled in working from boats, such as hunters of fish and cetaceans. They could harvest the seaweed, dry it, burn it and trade the ash to the crew of Strider.

Perhaps crew members came to an agreement with the indigenous people in a coastal area where much kelp grew offshore in which they were paid in useful metal objects for the iodine and calcium carbonate they extracted from kelp caliche. They might have used a very large boat with electrically driven propellers, supplied by Strider, to help them harvest kelp from the sea; perhaps it was the boat in Norse myth called Naglfar (see Chapter 15).

Self-guiding Ships

The Greek story of the wanderings of Odysseus describes the nature and deeds of a people skilled in voyaging across the sea in ships; they were the Phaeacians.

“And tell me thy country, thy people, and thy city, that our ships may convey thee thither, discerning the course by their wits. For the Phaeacians have no pilots, nor steering-oars such as other ships have, but their ships of themselves understand the thoughts and minds of men, and they know the cities and rich fields of all peoples, and most swiftly do they cross over the gulf of the sea, hidden in mist and cloud, nor ever have they fear of harm or ruin” (Homer, The Odyssey, book 8, line 555-564, translated by A T Murray).

“And as on a plain four yoked stallions spring forward all together beneath the strokes of the lash, and leaping on high swiftly accomplish their way, even so the stern of that ship leapt on high, and in her wake the dark wave of the loud-sounding sea foamed mightily, and she sped safely and surely on her way; not even the circling hawk, the swiftest of winged things, could have kept pace with her. Thus she sped on swiftly and clove the waves of the sea, bearing a man the peer of the gods in counsel” (The Odyssey, book 13, lines 81-90).

Perhaps this seagoing ship was lowered from the Strider and used to harvest large quantities of kelp.

12

IODINE IN THE ATMOSPHERE CHILLS THE TEMPERATE ZONE

“Enhanced atmospheric iodine levels will likely promote the formation of new ultrafine aerosol particles. The acceleration of tropospheric ozone loss due to higher iodine levels leads to a reduction in the oxidative capacity of the atmosphere and a reduction in the ozone radiative forcing. Indeed, at present, the halogen-mediated depletion of tropospheric ozone, a potent greenhouse gas, is estimated to account for 30% of ozone radiative forcing. The increase in both the formation of ultrafine particles and ozone destruction leads to a cooling effect on the climate” (Nature Communications on Rapid increase in atmospheric iodine levels in the North Atlantic since the mid-20th century at https://www.nature.com/articles/s41467-018-03756-1 ).

If Strider and Arrow used iodine as reaction-mass they would cause a period of a few years of unusually cold weather in temperate zones on Earth and unusually warm weather in polar regions where the earth was covered with snow for much of each year, where the increased cloud cover acted as a blanket.

As the ships decelerated from cruise velocity they would eject iodine toward Earth’s atmosphere. Iodic acid clusters would form in the atmosphere, providing Cloud Condensation Nuclei on which water vapour condenses, forming clouds. An influx of iodine into the atmosphere would increase cloudiness.

As Strider and Arrow accelerated away from Earth orbit at the end of their missions they ejected iodine into the atmosphere and the effects were the same as before, but the existing snow cover was not as extensive because of the previous warming effect. Therefore the increase in cloudiness would cool the area that had previously been warmed and also cool the temperate zones.

If the area chosen for the refuelling base of Strider was in an area that was normally covered with snow for much of the year the arrival of the ship would warm it up and reduce snow cover and the departure of the ship years later would cool it down and increase snow cover.

“Scientists have found evidence in tree-rings of eight decade-long coolings in the Northern Hemisphere between 4,370 BC and 545 AD. They supposed that comet dust or volcanic eruptions of dust and sulphur in corresponding dates caused most of them. Coolings beginning in 4,370 BC, 3,190 BC and 2,354 BC do not correspond with any known volcanic eruptions” (Kjeld Engvild, A review of the risks of sudden global cooling and its effects on agriculture, Agricultural and Forest Meteorology 115(3):127-137, 2003).

In this essay we propose tentatively that the 4,370 BC cooling was caused by iodine ejected as reaction-mass by Strider and Arrow decelerating toward Earth and entering low Earth orbit, and that the cooling was prolonged by iodine ejected by Strider and Arrow accelerating away from Earth several years later.

The Great Winter

“In Norse mythology, Fimbulvetr (or fimbulvinter), commonly rendered in English as Fimbulwinter, is the immediate prelude to the events of Ragnarök. It means ‘great winter’ ”.

“Fimbulwinter is the harsh winter that precedes the end of the world and puts an end to all life on Earth. Fimbulwinter is three successive winters, when snow comes in from all directions, without any intervening summer. Innumerable wars follow.

“The event is described primarily in the Poetic Edda. In the poem Vafþrúðnismál, Odin poses the question to Vafþrúðnir as to who of mankind will survive the Fimbulwinter. Vafþrúðnir responds that Líf and Lífþrasi will survive and that they will live in the forest of Hoddmímis holt” (Wikipedia on Fimbulwinter).

“In Norse mythology, Hoddmímis holt is a location where Líf and Lífþrasir are foretold to survive the long winters of Fimbulvetr”.

“In the poem Vafþrúðnismál, collected in the Poetic Edda, the god Odin poses a question to the jötunn Vafþrúðnir, asking who among mankind will survive when the winter Fimbulvetr occurs. Vafþrúðnir responds that they will be Líf and Lífþrasir, that the two will have hidden in the wood of Hoddmímis holt, they will consume the morning dew as food, and “from them generations will spring” (Wikipedia on Hoddmímis holt).

This poem implies that the Fimbulvetr was foretold. We propose that the crew of Strider foretold it, as a warning to human beings, because they knew that when their ship accelerated away from Earth the idodine it ejected as reaction-mass would increase cloudiness and chill the northern temperate zone. We also propose that the Great Winter was not necessarily the immediate prelude to the events of Ragnarök.

13

REFUELLING THE ARROW ON EARTH

When it became time to go home the Arrow could not be refuelled by the method used to load fuel for its outward voyage. The efficient, powerful, sophisticated infrastructure on the home planet did not exist on Earth: no runways suitable for high-speed take-offs; no spaceplanes. No big fuel-manufacturing factories to separate boron from its ores and then separate boron-11 from boron-10, and to separate hydrogen-1 from hydrogen-2 (deuterium).

Boron-11 has five protons and 6 neutrons in its nucleus; boron-10 has five protons and five neutrons in its nucleus; their chemistry, determined by their number of protons and the electrons that surround the nucleus, is the same but their nuclear reactions are very different.

These separations would have to be done in a small chemical plant lowered to Earth by the crew, or installed in Strider.

The Arrow was a small fast interstellar ship in which living intelligent beings had travelled to Earth in a state of suspended animation. It had its own aneutronic generator of electricity and its own thruster.

The mass of fuel to be manufactured and then loaded on the Arrow for its homeward voyage was the same as it had needed on its outward voyage: several hundred tonnes of fuel-and-reaction-mass.

The hundreds of tonnes of fuel-and-reaction-mass for Arrow had to be loaded while Strider, with the Arrow still coupled to it, was hovering only 100 metres above the ground, docked to the top of the huge tube which Earth-people likened to the trunk of a tree.

Processing Fuel for Arrow’s Return Voyage

The Arrow needed hydrogen-1 and boron-11. It might also have needed some boron-10 to replace a “used” original shield of boron-10 placed round the reaction chamber during the build to stop the very few neutrons produced in the aneutronic fusion as they left the chamber. Aneutronic fusion of hydrogen-1 and boron-11 produces a few neutrons from side-reactions.

“Detailed calculations show that at least 0.1 percent of the reactions in a thermal protons-and-¹¹B plasma would produce neutrons, and the energy of these neutrons would account for less than 0.2 percent of the total energy released” (Wikipedia on Aneutronic fusion). However, we do not know the conditions under which protons and boron-11 were fused in the fusion chambers of Strider, Arrow and the Dashers; they might have been conditions in which hardly any neutrons were produced.

Getting Boron on Earth

The most suitable boron mineral for the crew to get would be boric acid which “has the chemical formula H₃BO₃ (sometimes written B(OH)₃), and exists in the form of colourless crystals or a white powder that dissolves in water. When occurring as a mineral, it is called sassolite”.

“Sassolite is a borate mineral and is the mineral form of boric acid. It occurs in volcanic fumaroles and hot springs, as well as in bedded sedimentary evaporite deposits. Its mineral form was first described in 1800, and was named after Sasso Pisano, Castelnuovo Val di Cecina, Pisa Province, Tuscany, Italy where it was found. The mineral may be found in lagoons throughout Tuscany and Sasso” (Wikipedia on Sassolite).

“Boric acid, or sassolite, is found mainly in its free state in some volcanic districts, for example, in the Italian region of Tuscany, the Lipari Islands and the US state of Nevada. In these volcanic settings it issues, mixed with steam, from fissures in the ground” (Wikipedia on Boric acid).

“The most common ore of boron is borax, sodium borate, which is a salt of boric acid containing sodium” (Wikipedia on Borax).

The crew would have wished to avoid the task of removing sodium from hundreds of tonnes of borax, which is done by adding hydrochloric acid to the borax:

Na₂B₄O₇·10 H₂O + 2 HCl → 4 B(OH)₃ + 2 NaCl + 5 H₂O

There is nothing exotic or rare about borax, it can be bought cheaply in supermarkets and is used for various purposes in households. Boron is used in glass vessels used in ovens and in many applications as a strengthening fibre in polymers.

Separating Boron-10 from Boron-11

Boron has two naturally occurring and stable isotopes, B-11 (80.1 percent) and B-10 (19.9 percent).

“The B-10 isotope is useful for capturing thermal neutrons …  The nuclear industry enriches natural boron to nearly pure B-10. The less-valuable by-product, depleted boron, is nearly pure B-11.

Commercial isotope enrichment. “Because of its high neutron cross-section, boron-10 is often used to control fission in nuclear reactors as a neutron-capturing substance. Several industrial-scale enrichment processes have been developed; however, only the fractionated vacuum distillation of the dimethyl ether adduct of boron trifluoride (DME-BF₃) and column chromatography of borates are being used” (Wikipedia on Boron).

The term “nuclear industry” above refers to the production of energy through the fission of heavy elements. If the fusion of light elements were achieved on an industrial scale on Earth B-11 would be the more valuable isotope.

The fractionated vacuum distillation method would have been used by the crew of Strider because the alternative method, chromatography of borates, would leave them with the task of getting rid of hundreds of tonnes of sodium.

Boron trifluoride, BF₃ “is manufactured by the reaction of boron oxides with hydrogen fluoride:

B₂O₃ + 6 HF → 2 BF₃ + 3 H₂O

“Typically the HF (hydrogen fluoride) is produced in situ from sulfuric acid and fluorite (CaF2). Approximately 2300-4500 tonnes of boron trifluoride are produced every year” (Wikipedia on Boron trifluoride).

“Fluorite forms as a late-crystallizing mineral in felsic igneous rocks typically through hydrothermal activity. It is particularly common in granitic pegmatites. It may occur as a vein deposit formed through hydrothermal activity particularly in limestones. In such vein deposits it can be associated with galena, sphalerite, barite, quartz, and calcite” (Wikipedia on Fluorite).

The crew had to obtain fluorite from a deposit preferably near the surface and manufacture sulphuric acid from sulphur to make hydrogen fluoride. Sulphur can be got from some volcanoes.

“Boric acid will initially decompose into steam, (H₂O) and metaboric acid (HBO₂) at around 170 degrees C, and further heating above 300 degrees C will produce more steam and diboron trioxide. The reactions are:

H₃BO3 → HBO₂ + H₂O

2 HBO₂ → B₂O₃ + H₂O” (Wikipedia on Boron trioxide).

The crew then treated the boron trioxide with hydrogen fluoride, HF to make boron trifluoride, BF₃.

“Sulfuric acid is a key substance in the chemical industry. It is most commonly used in fertiliser manufacture, but is also important in mineral processing, oil refining, wastewater processing, and chemical synthesis. It has a wide range of end applications including in domestic acidic drain cleaners, as an electrolyte in lead-acid batteries, in dehydrating a compound, and in various cleaning agents. Sulfuric acid can be obtained by dissolving sulfur trioxide in water” (Wikipedia on Sulfuric acid).

“Sulfur dioxide is produced by the burning of sulfur or iron pyrite (a sulfide ore of iron). After being purified by electrostatic precipitation, the SO₂ is then oxidised [to sulfur trioxide] by atmospheric oxygen at between 400 and 600 degrees C over a catalyst” (Wikipedia on Sulfur trioxide).

In the distillation plant the HF and the dimethyl ether were recycled. The only waste product to be got rid of was water in the form of steam.

Separating hydrogen-1 from hydrogen-2

Hydrogen was obtained by using electrical power to split water into hydrogen and oxygen.

Hydrogen-1 is the main isotope of hydrogen. Hydrogen-2 (deuterium), which is present in water must be removed to leave pure hydrogen-1, one of the fuels of the ship’s aneutronic fusion-powered generator of electricity.

“On Earth, deuterated water, HDO, occurs naturally in normal water at a proportion of about 1 molecule in 3,200. This means that 1 in 6,400 hydrogen atoms in water is deuterium, which is 1 part in 3,200 by weight (hydrogen weight). The HDO may be separated from normal water by distillation or electrolysis and by various chemical exchange processes … The most cost-effective process for producing heavy water is the dual temperature exchange sulphide process known as the Girdler sulphide process” (Wikipedia on Heavy water).

The removal of heavy water left water that contained only H-1. Electrolysis of this water yielded h-1 gas and oxygen gas. The H-1 was used as one of the fuels used in the fusion powered electric generators of the interstellar ships.

14

THE DEPARTURE

In the course of years Strider had moved to various base stations as its crew found and processed needed resources. At each base station it had anchored itself to the ground using the huge tube, which it carried with it.

Strider could not return to its home planet because it could not be refuelled on Earth. Its crew did not have the capacity to manufacture and load a big mass of fuel.

After several years of work and exploration the time came when Strider, hovering above the huge tube, had eventually been loaded with a comparatively small quantity of fuel-and-reaction-mass and the Arrow had been fully loaded with fuel and reaction mass.

The Strider crew had been friendly with the Earth people they had met and had taught them many valuable ideas and processes. They taught them how to live lawfully in peace. They taught them  the basics of astronomy, mathematics, navigation, chemistry, physics and writing.

They had played music and laughed and danced with the Earth people.

In return the Earth people had helped in transporting materials needed by the ship and in processing and loading the fuel and reaction mass. But when all this had been done the crew members and their human friends said their farewells to each other.

And then the departing voyagers foretold that their friends would have to endure a long-lasting winter after Strider and Arrow had disappeared, and two persons (named in the Nordic myths as Líf and Lífþrasir) would hide in a wood,  consume the morning dew as food, and “from them generations will spring”. The Nordic myths called this the Fimbulvetr “great winter”.

“Fimbulwinter is three successive winters, when snow comes in from all directions, without any intervening summer”.

The summary of the myths about this winter presented in Wikipedia (see above under The Great Winter) says that “Fimbulwinter is the immediate prelude to the events of Ragnarök”. In this essay we propose that Fimbulwinter was not necessarily the immediate prelude to Ragnarök, and that Ragnarök was not foretold as an imminent danger by the crew of Strider.

The crews of Strider and Arrow could foretell the time of the Great Winter accurately because they knew that the many tonnes of iodine vapour hurled toward the Earth by their ships’ thrusters would increase the Earth’s cloudiness, the clouds would reflect the sun’s warmth and the northern temperate zone on Earth would be chilled for about three years.

But they could not foretell an eruption of the volcanic fumaroles near their “huge tree” and the refuelling base, where the crew had got boric acid as a source of boron.

The Earth people knew from the stories of their ancestors that these fumaroles had been quietly producing the white crystals known to modern chemists as boric acid for hundreds of years. There were no indications that they would not continue to do so for hundreds of years in the future. There were no signs of volcanic instability which would warn them or their visitors of an imminent violent eruption.

Lift-off

Strider rose as high above its Earth base as it could using its horizontally rotating propellers and then used its thruster to accelerate to orbital velocity and altitude. Soon it accelerated out of its orbit and all its crew moved into the Arrow. Then Arrow separated from the Strider.

Strider, with its few remaining fuel tanks and pumps and its many horizontal and vertical propellers in their streamlined frame, accelerated and went wandering off into space, alone and almost empty.

The intelligent living beings inside Arrow entered suspended animation again with the assistance of dedicated robots. Arrow accelerated using its own thruster for about two years to about 10 percent of light speed and then cruised for 40 years. Then it decelerated for about two years and finally entered a suitable low orbit round its home planet. It docked with a specialised spaceplane which took the crew safely down to the ground. The crew were reanimated, welcomed by the planet’s government and citizens and reunited with their friends.

15

THE LAND THAT SANK INTO THE SEA

We proposed above that the violent events called Ragnarök happened without warning at some time  after Fimbulvetr, the “great winter”.

“In Norse mythology, Ragnarök is a series of events, including a great battle, foretold to lead to the death of a number of great figures (including the gods Odin, Thor, Týr, Freyr, Heimdallr, and Loki), natural disasters and the submersion of the world in water. After these events, the world will resurface anew and fertile, the surviving and returning gods will meet and the world will be repopulated by two human survivors”.

“The ‘sons of Mím’ are described as being ‘at play’, though this reference is not further explained in surviving sources. Heimdall raises the Gjallarhorn into the air and blows deeply into it, and Odin converses with Mím’s head. The world tree Yggdrasil shudders and groans. The jötunn Hrym comes from the east, his shield before him. The Midgard serpent Jörmungandr furiously writhes, causing waves to crash. ‘The eagle shrieks, pale-beaked he tears the corpse’, and the ship Naglfar breaks free thanks to the waves made by Jormungandr and sets sail from the east. The fire jötnar inhabitants of Muspelheim come forth.

“The völva continues that Jötunheimr, the land of the jötnar, is aroar, and that the Æsir are in council. The dwarfs groan by their stone doors. Surtr advances from the south, his sword brighter than the sun. Rocky cliffs open and the jötnar women sink.

“The gods then do battle with the invaders: Odin is swallowed whole and alive fighting the wolf Fenrir, causing his wife Frigg her second great sorrow (the first being the death of her son, the god Baldr). Odin’s son Víðarr avenges his father by rending Fenri’s jaws apart and stabbing it in the heart with his spear, thus killing the wolf. The serpent Jörmungandr opens its gaping maw, yawning widely in the air, and is met in combat by Thor. Thor, also a son of Odin and described here as protector of the earth, furiously fights the serpent, defeating it, but Thor is only able to take nine steps afterward before collapsing. The god Freyr fights Surtr and loses. After this, people flee their homes, and the sun becomes black while the earth sinks into the sea, the stars vanish, steam rises, and flames touch the heavens” (Wikipedia on Ragnarök).

We propose that these destructive events happened near the World Tree and were caused by a volcanic eruption, earthquake and tsunami. We should pause to reflect on what a great loss was inflicted on humanity by this appalling act of violence done by moving oceanic plates.

16

REFLECTING ON OUR LOSS

In the land at the first Earth base near the huge tube called the World Tree there must have been small roads, farmlets, orchards, gardens, houses, villages, a School of Science and Mathematics with a library established by the crew of Strider, an alphabet used in an early form of writing preserved on metal or baked clay, a chemical processing plant, smelter, forge, workshops, water supply, septic tanks, quays for boats, and the locking dock-ring for the bottom of the World Tree. The crew might also have left as gifts near their former base many useful small machines, tools and cunning devices such as lathes, compasses, theodolites and telescopes.

But the greatest loss would have been the loss of continuity of learning, knowledge, democratic open government, law and peaceful behaviour in the human community.

What happened to the land near the first base station? Are its artefacts, including the huge tube which humans called the World Tree, sunk there below the surface of water and mud?

We do have an artefact left by our interstellar visitors, though in its present form it is not material, it is intellectual. It is the length of the hecatompedon: the precise and meaningful length of the upper step of the front of the Parthenon in Athens.

We may say of our visitors that they were highly intelligent, immensely courageous, accomplished in science and technology, full of good-will toward us, and unlucky.

©Björn Björklund 2024