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Wednesday, June 26, 2019

Reading List: The Voyage of the Iron Dragon

Kroese, Robert. The Voyage of the Iron Dragon. Grand Rapids MI: St. Culain Press, 2019. ISBN 978-1-7982-3431-0.
This is the third and final volume in the Iron Dragon trilogy which began with The Dream of the Iron Dragon (August 2018) and continued in The Dawn of the Iron Dragon (May 2019). When reading a series of books I've discovered, I usually space them out to enjoy them over time, but the second book of this trilogy left its characters in such a dire pickle I just couldn't wait to see how the author managed to wrap up the story in just one more book and dove right in to the concluding volume. It is a satisfying end to the saga, albeit in some places seeming rushed compared to the more deliberate development of the story and characters in the first two books.

First of all, this note. Despite being published in three books, this is one huge, sprawling story which stretches over more than a thousand pages, decades of time, and locations as far-flung as Constantinople, Iceland, the Caribbean, and North America, and in addition to their cultures, we have human spacefarers from the future, Vikings, and an alien race called the Cho-ta'an bent on exterminating humans from the galaxy. You should read the three books in order: Dream, Dawn, and Voyage. If you start in the middle, despite the second and third volumes' having a brief summary of the story so far, you'll be completely lost as to who the characters are, what they're trying to do, and how they ended up pursuing the desperate and seemingly impossible task in which they are engaged (building an Earth-orbital manned spacecraft in the middle ages while leaving no historical traces of their activity which later generations of humans might find). “Read the whole thing,” in order. It's worth it.

With the devastating events which concluded the second volume, the spacemen are faced with an even more daunting challenge than that in which they were previously engaged, and with far less confidence of success in their mission of saving humanity in its war for survival against the Cho-ta'an more than 1500 years in their future. As this book begins, more than two decades have passed since the spacemen crashed on Earth. They have patiently been building up the infrastructure required to build their rocket, establishing mining, logging, materials processing, and manufacturing at a far-flung series of camps all linked together by Viking-built and -crewed oceangoing ships. Just as important as tools and materials is human capital: the spacemen have had to set up an ongoing programme to recruit, educate, and train the scientists, engineers, technicians, drafters, managers, and tradespeople of all kinds needed for a 20th century aerospace project, all in a time when only a tiny fraction of the population is literate, and they have reluctantly made peace with the Viking way of “recruiting” the people they need.

The difficulty of all of this is compounded by the need to operate in absolute secrecy. Experience has taught the spacemen that, having inadvertently travelled into Earth's past, history cannot be changed. Consequently, nothing they do can interfere in any way with the course of recorded human history because that would conflict with what actually happened and would therefore be doomed to failure. And in addition, some Cho-ta'an who landed on Earth may still be alive and bent on stopping their project. While they must work technological miracles to have a slim chance of saving humanity, the Cho-ta'an need only thwart them in any one of a multitude of ways to win. Their only hope is to disappear.

The story is one of dogged persistence, ingenuity in the face of formidable obstacles everywhere; dealing with adversaries as varied as Viking chieftains, the Vatican, Cho-ta'an aliens, and native American tribes; epic battles; disheartening setbacks; and inspiring triumphs. It is a heroic story on a grand scale, worthy of inclusion among the great epics of science fiction's earlier golden ages.

When it comes to twentieth century rocket engineering, there are a number of goofs and misconceptions in the story, almost all of which could have been remedied without any impact on the plot. Although they aren't precisely plot spoilers, I'll take them behind the curtain for space-nerd readers who wish to spot them for themselves without foreknowledge.

Spoiler warning: Plot and/or ending details follow.  
  • In chapter 7, Alma says, “The Titan II rockets used liquid hydrogen for the upper stages, but they used kerosene for the first stage.” This is completely wrong. The Titan II was a two stage rocket and used the same hypergolic propellants (hydrazine fuel and dinitrogen tetroxide oxidiser) in both the first and second stages.
  • In chapter 30 it is claimed “While the first stage of a Titan II rocket could be powered by kerosene, the second and third stages needed a fuel with a higher specific impulse in order to reach escape velocity of 25,000 miles per hour.” Oh dear—let's take this point by point. First of all, the first stage of the Titan II was not and could not be powered by kerosene. It was designed for hypergolic fuels, and its turbopumps and lack of an igniter would not work with kerosene. As described below, the earlier Titan I used kerosene, but the Titan II was a major re-design which could not be adapted for kerosene. Second, the second stage of the Titan II used the same hypergolic propellant as the first stage, and this propellant had around the same specific impulse as kerosene and liquid oxygen. Third, the Titan II did not have a third stage at all. It delivered the Gemini spacecraft into orbit using the same two stage configuration as the ballistic missile. The Titan II was later adapted to use a third stage for unmanned space launch missions, but a third stage was never used in Project Gemini. Finally, the mission of the Iron Dragon, like that of the Titan II launching Gemini, was to place its payload in low Earth orbit with a velocity of around 17,500 miles per hour, not escape velocity of 25,000 miles per hour. Escape velocity would fling the payload into orbit around the Sun, not on an intercept course with the target in Earth orbit.
  • In chapter 45, it is stated that “Later versions of the Titan II rockets had used hypergolic fuels, simplifying their design.” This is incorrect: the Titan I rocket used liquid oxygen and kerosene (not liquid hydrogen), while the Titan II, a substantially different missile, used hypergolic propellants from inception. Basing the Iron Dragon's design upon the Titan II and then using liquid hydrogen and oxygen makes no sense at all and wouldn't work. Liquid hydrogen is much less dense than the hypergolic fuel used in the Titan II and would require a much larger fuel tank of entirely different design, incorporating insulation which was unnecessary on the Titan II. These changes would ripple all through the design, resulting in an entirely different rocket. In addition, the low density of liquid hydrogen would require an entirely different turbopump design and, not being hypergolic with liquid oxygen, would require a different pre-burner to drive the turbopumps.
  • A few sentences later, it is said that “Another difficult but relatively straightforward problem was making the propellant tanks strong enough to be pressurized to 5,000 psi but not so heavy they impeded the rocket's journey to space.” This isn't how tank pressurisation works in liquid fuelled rockets. Tanks are pressurised to increase structural rigidity and provide positive flow into the turbopumps, but pressures are modest. The pressure needed to force propellants into the combustion chamber comes from the boost imparted by the turbopumps, not propellant tank pressurisation. For example, in the Space Shuttle's External Tank, the flight pressure of the liquid hydrogen tank was between 32 and 34 psia, and the liquid oxygen tank 20 to 22 psig, vastly less than “5,000 psi”. A fuel tank capable of withstanding 5,000 psi would be far too heavy to ever get off the ground.
  • In chapter 46 we are told, “The Titan II had been adapted from the Atlas intercontinental ballistic missile….” This is completely incorrect. In fact, the Titan I was developed as a backup to the Atlas in case the latter missile's innovative technologies such as the pressure-stabilised “balloon tanks” could not be made to work. The Atlas and Titan I were developed in parallel and, when the Atlas went into service first, the Titan I was quickly retired and replaced by the hypergolic fuelled Titan II, which provided more secure basing and rapid response to a launch order than the Atlas.
  • In chapter 50, when the Iron Dragon takes off, those viewing it “squinted against the blinding glare”. But liquid oxygen and liquid hydrogen (as well as the hypergolic fuels used by the original Titan II) burn with a nearly invisible flame. Liquid oxygen and kerosene produce a brilliant flame, but these propellants were not used in this rocket.
  • And finally, it's not a matter of the text, but what's with that cover illustration, anyway? The rocket ascending in the background is clearly modelled on a Soviet/Russian R-7/Soyuz rocket, which is nothing like what the Iron Dragon is supposed to be. While Iron Dragon is described as a two stage rocket burning liquid hydrogen and oxygen, Soyuz is a LOX/kerosene rocket (and the illustration has the characteristic bright flame of those propellants), has four side boosters (clearly visible), and the spacecraft has a visible launch escape tower, which Gemini did not have and was never mentioned in connection with the Iron Dragon.

Fixing all of these results in the Iron Dragon's being a two stage (see the start of chapter 51) liquid hydrogen fuel, liquid oxygen oxidiser rocket of essentially novel design, sharing little with the Titan II. The present-day rocket which most resembles it is the Delta IV, which in its baseline (“Medium”) configuration is a two stage LOX/hydrogen rocket with more than adequate payload capacity to place a Gemini capsule in low Earth orbit. Its first stage RS-68 engines were designed to reduce complexity and cost, and would be a suitable choice for a project having to start from scratch. Presumably the database which provided the specifications of the Titan II would also include the Delta IV, and adapting it to their requirements (which would be largely a matter of simplifying and derating the design in the interest of reliability and ease of manufacture) would be much easier than trying to transform the Titan II into a LOX/hydrogen launcher.

Spoilers end here.  

Despite the minor quibbles in the spoiler section (which do not detract in any way from enjoyment of the tale), this is a rollicking good adventure and satisfying conclusion to the Iron Dragon saga. It seemed to me that the last part of the story was somewhat rushed and could have easily occupied another full book, but the author promised us a trilogy and that's what he delivered, so fair enough. In terms of accomplishing the mission upon which the spacemen and their allies had laboured for half a century, essentially all of the action occurs in the last quarter of this final volume, starting in chapter 44. As usual nothing comes easy, and the project must face a harrowing challenge which might undo everything at the last moment, then confront the cold equations of orbital mechanics. The conclusion is surprising and, while definitively ending this tale, leaves the door open to further adventures set in this universe.

This series has been a pure delight from start to finish. It wasn't obvious to this reader at the outset that it would be possible to pull time travel, Vikings, and spaceships together into a story that worked, but the author has managed to do so, while maintaining historical authenticity about a neglected period in European history. It is particularly difficult to craft a time travel yarn in which it is impossible for the characters to change the recorded history of our world, but this is another challenge the author rises to and almost makes it look easy. Independent science fiction is where readers will find the heroes, interesting ideas, and adventure which brought them to science fiction in the first place, and Robert Kroese is establishing himself as a prolific grandmaster of this exciting new golden age.

The Kindle edition is free for Kindle Unlimited subscribers.

Posted at June 26, 2019 11:47