Monday, 13 August 2018

Is Relativistic Space Flight Possible – Review of an Article in Acta Astronautica

Is Relativistic Space Flight Possible – Review of an Article in Acta Astronautica

Here’s a summary of an interesting paper in Acta Astronautica, called “Pros and cons of relativistic interstellar flight, by Oleg Semyonov, a retired professor at State University of New York, Stony Brook.  He looks at the possibilities for relativistic interstellar space flight, based on currently accepted mainstream physics (i.e. exotic possibilities like warp bubbles or wormholes are not considered).  However, if these exotic possibilities do interest you, try reading a couple of blogs on that subject:

Faster than Light Travel with the Alcubierre Drive - Part 2:

I will skip the detailed physics and mathematical derivations in Professor Semyonov’s paper, as any interested party can check those out in the original article.  Hopefully, I have been able to give a reasonably accurate sense of what the author proposes, but you can always go to the source for more information.


Possibilities for Relativistic Spacecraft, Using Standard Physics

As far as the actual propulsion of a realistic interstellar craft goes, the author concludes that matter-antimatter annihilation is the only realistic choice.  Ordinary fuels, right up to thermonuclear propulsion, simply don’t have the energy density required to accelerate a ship up to relativistic speeds (greater than 10% of the speed of light, or .1c).  That being said, they would still be useful for travel within the solar system.

This is because these methods release relatively little energy compared to their mass, and since the reaction mass (fuel) must be carried along with the ship (until it is consumed), most of the energy goes into accelerating the fuel itself.  This is why standard chemical rockets are so big, relative to their payloads.

The problem only becomes worse as really high velocities are attempted, as the energy required to accelerate a mass to a given velocity scales as the square of the velocity in Newtonian physics and this issue is exacerbated in relativistic physics, as the actual mass of the rocket goes up with velocity (i.e. m = m/sqrt(1-v**2/c**2)).  So, it is vital that the fuel have as high an energy density as possible.
So, how would such a craft work?

·       First off, you would need to create fuel, likely in the form of anti-hydrogen.  Where hydrogen has a proton being orbited by an electron, anti-hydrogen has an anti-proton being orbited by an anti-electron (positron).  Currently, anti-protons are made by irradiating metallic targets with high energy protons. Those are then slowed down and combined with positrons (from a separate source), producing anti-hydrogen.  The production rates and efficiencies of the current processes would have to be improved by many orders of magnitude, or new processes would have to be invented. Naturally, it would take a lot of energy to create a substantial amount of anti-hydrogen.  Ultimately, solar energy would seem to be the most likely source for that.

·       Then, the anti-hydrogen atoms would be prompted to combine with each other to form anti-hydrogen molecules, in a similar way that hydrogen atoms combine to form hydrogen molecules (H2).  Those would then be super-cooled to produce a liquid or solid form.  Since the resulting anti-hydrogen molecules are diamagnetic, they could be stored via magnetic containment (a magnetic field gradient), so that they wouldn’t interact with the normal matter, annihilating before ever reaching an engine (and blowing up your spacecraft in the process).  Transporting the fuel from storage to engine would also have to make use of some sort of magnetic field processes.

·       The energy stored in the anti-hydrogen could be used to propel the craft via a few possibilities:
o   A photon rocket, using gamma-ray level energy photons (created by electron-positron annihilation), reflected against a mirror, creating a propulsive reaction force.
o   A meson rocket, using charged pi and mu mesons, produced by annihilating protons and anti-protons, which then become the reaction mass for the propulsion of the ship.
o   A high energy (relativistic) ion rocket, the author’s favoured choice.  It seems that this method is more efficient at converting annihilation energy into propulsion energy than the first two, and also has better beam alignment (i.e. the beam can be made nearly parallel, and thus provide more efficient thrust).

·       The author models a number of cases for a hypothetical craft’s mass and the  power level of its reactor, giving expected speeds attained and acceleration durations until half the fuel is consumed.  It is necessary to hold back a good amount of fuel, in order to decelerate once the target location has been reached.

·       There are a number of graphs showing the results, so I will just give an ideal type case as an example.  Assuming that the craft can achieve a 50% efficiency rate for turning anti-matter annihilation energy into propulsion, can achieve an ion exhaust velocity of .5c, has an initial mass of about 1000 tons (including fuel), and can put out power at 100 terawatts. 
o   A rocket velocity of about .3c could be reached by the time half the fuel was consumed.
o   The acceleration time would be a bit under 3 years.
o   Therefore, a trip to a nearby star (say 4 light years) would take about two decades (3 years accelerating, 12 years cruising at .3c, and 3 years decelerating).

·       Note that the graphs also show cases for consuming 75% of the fuel, and for other combinations of rocket mass and power.
Of course, this all assumes that humanity (or some significant part of it) would be willing to devote the enormous resources needed for the task and could come up with the requisite technologies.  Which leads into, the next section.


Problems for Relativistic Spacecraft, Technical and Otherwise

Some important issues would have to be dealt with, even after developing the required technologies for fuel production, propulsion and other spacecraft considerations.  Key among these are heat and ionizing radiation.


When you generate power, you produce waste heat.  That is true of any thermodynamic process.  Direct propulsion via annihilation of anti-matter would be no exception.  The reactor and turbine walls would accumulate heat, and that heat would have to be dissipated into space.  That would have to be done via thermal dissipation, radiators in other words.

The efficiency of a relativistic ion engine increases as the temperature drop across the engine increases – i.e. you want at hot engine and a cold heat sink.  However, the amount of heat per unit area (and thus the radiator’s mass) that can be radiated away by a radiator goes up strongly with temperature.  So, for propulsion efficiency you want a cold heat sink (radiator), but for purposes of dumping waste heat with minimal mass, you want a hot radiator.

A trade-off between these goals will be necessary, but this will be a practical limitation on the spacecraft’s ultimate useful power production, and therefore ultimate achievable velocity.

Ionizing Radiation

Interstellar space contains rarefied gases, as well as dust particles of various sizes.  These materials are at concentrations that are extremely low compared to any vacuum we can create on Earth, but they can become a problem to a craft plowing through them at high velocity, especially relativistic velocities.

The situation is equivalent to being at rest and being battered by a strong wind; at high speeds  the gas molecules and small particles pack tremendous energy.  At relativistic velocities this can become equivalent to hard ionizing radiation.  A traveller in a ship moving at .5c, with little shielding, would receive a dose of radiation equivalent to being in the middle of a nuclear reactor.  So, an astronaut would receive a lethal dose of radiation in minutes, if not seconds.

One approach to the problem is to keep velocities well below .3c or thereabouts.  The other is to shield the rocket with mass, much as we shield nuclear reactor cores.  A strong magnetic field generated in front of the ship could help with charged particles, but dust grains would likely require a shield of solid material.  Both would add mass to the ship.  Also, turning maneuvers would be dangerous, as the ship could come out of the shadow of its protective shield at such times.

Social Factors

Various social factors are also important, both for individuals and society.

At the societal level, the most obvious problem is money.  Will humanity be willing to spend the sort of money required to explore interstellar space?  Just producing anti-matter in the required amounts would be enormously expensive, not to speak of the cost of developing reliable spacecraft of such advanced technology.

Also, as the human race becomes richer and more advanced, there simply may be no need or desire for interstellar exploration.  With a steady-state sustainable population, there may be little interest in colonization and no demographic pressure from an expanding population.

We can already see this in the technologically advanced areas of the world, where the birth rate has largely dropped below replacement.  On the other hand, the development of an artificial womb could create entirely new set of demographic pressures, so we can’t be too sure how the demographic issue will play out over the long haul.

At any rate, as the author points out, the human race has done some pretty fantastic things over its history, such as populating far-flung islands tens of thousands of years ago, with very primitive sea-faring craft, and no navigational technology or knowledge to speak of.  The U.S. put a lot of resources into landing humans on the moon (then shrugged and moved on to other things).  Other examples could be listed.  So, it is hard to predict the political will of a society, let alone the future human species.  Many unexpected, even strictly not rational, things can happen, given enough time.

At the individual (or small group) level, the main problem is probably the duration of space flight, even if relativistic speeds can be achieved.  Will any crew be able, or willing, to spend a lifetime on a mission?  If a habitable planet is discovered, will it be possible to send a large enough group there, to make a self-sustaining colony?

How about AI?  Can we send intelligent machines in our place?  Maybe, but even this is questionable.  A journey to any but the nearest stars would take hundreds, maybe thousands of years.  We don’t really know how long any machine can be kept in suspense, then rebooted to a satisfactory operating condition, let alone something as complex as an AI capable of doing useful work after centuries of interstellar travel.  Perhaps they would be just as prone to entropy and breakdown as we biological machines are.

Could this be the answer to the Fermi Paradox – interstellar travel is just too difficult and expensive for any civilization to bother.  Maybe once you make your planet cozy enough, you just have no interest in leaving.  Or, perhaps it just takes too long, and everyone dies or becomes inoperative (including AI) long before the journey is over.  Personally, I hope those things aren’t true, because I still wonder what’s our there, and would like to get a closer look, or at least hope that my descendants do.
Pros and cons of relativistic interstellar flight, Oleg G. Semyonov, Acta Astronautica 151 (2018) 736–742

Now that you have read about a the near-term scientific prospects for interstellar travel, you should consider reading some Science Fiction.  How about a short story, also about interstellar travel.  It also features one possible scenario to explain why we haven’t met ET yet (as far as we know, anyway).  Only 99 cents on Amazon.

The Zoo Hypothesis or The News of the World: A Science Fiction Story

In the field known as Astrobiology, there is a research program called SETI, The Search for Extraterrestrial Intelligence.  At the heart of SETI, there is a mystery known as The Great Silence, or The Fermi Paradox, named after the famous physicist Enrico Fermi.  Essentially, he asked “If they exist, where are they?”.

Some quite cogent arguments maintain that if there was extraterrestrial intelligence, they should have visited the Earth by now. This story, a bit tongue in cheek, gives a fictional account of one explanation for The Great Silence, known as The Zoo Hypothesis.  Are we a protected species, in a Cosmic Zoo?  If so, how did this come about?  Read on, for one possible solution to The Fermi Paradox.

The short story is about 6300 words, or about half an hour at typical reading speeds.

Alternatively, consider another short invasion story, this one set in the Arctic.  Also 99 cents.

The Magnetic Anomaly

An attractive woman in a blue suit handed a dossier to an older man in a blue uniform.

“Give me a quick recap”, he said.

“A geophysical crew went into the Canadian north. There were some regrettable accidents among a few ex-military who had become geophysical contractors after their service in the forces. A young man and young woman went temporarily mad from the stress of seeing that. They imagined things, terrible things. But both are known to have vivid imaginations; we have childhood records to verify that. It was all very sad. That’s the official story.”

He raised an eyebrow. “And unofficially?”

“Unofficially,” she responded, “I think we just woke something up that had been asleep for a very long time.”

Wednesday, 8 August 2018

SF Action and Romance -Kati of Terra, Books 1, 2, and 3 on Kindle Countdown this week (and a Free Gothic Short Story)

SF Action and Romance -Kati of Terra, Books 1, 2, and 3 on Kindle Countdown this week (and a Free Gothic Short Story)

All three Kati of Terra books are on Kindle Countdown this week (August 9 to 16, 2018), a great value at 99 cents each, this week only (regular $3.99 each).  Enjoy all the adventure and romance, in a galaxy far, far away.

Also, the gothic short story “Beyond the Blue Door” is free this week.

Kati 1 - Escape from the Drowned Planet
Kati and Mikal's escape from the alien slaver Gorsh.
Amazon U.S.:
Amazon U.K.:

Kati 2 - On Assignment on the Planet of the Exalted
Kati and Mikal follow the trail of justice to the planet Vultaire.
Amazon U.S.:
Amazon U.K.:

Kati 3 - Showdown on the Planet of the Slavers
Kati and Mikal must battle Gorsh on his home turf.
Amazon U.S.:
Amazon U.K.:

Kati 1 - Escape from the Drowned Planet

In saving her small son from alien abductors, a 24-year-old Earth woman, Katie, finds herself abducted instead. She awakens from a drug-induced coma on a spaceship, in a room full of children, both human and alien, and two other women, younger than she is. The young women adapt to the situation as best they can, keeping the youngsters calm and entertained. But, when a drugged alien man wearing a uniform is added to the captive cargo, it becomes clear that this is an intergalactic slave operation.

The slave traders implant their captives with “translation nodes” in order to allow communication among various groups. These are living entities, normally docile, merely enhancing certain brain functions, such as language acquisition. However, Katie discovers that she has accidentally received a very special “granda node”, a long-lived node with its own cantankerous personality, including a fondness for criminality and lethal weaponry. Fortunately for Katie, it also values its freedom. With its help, she escapes on a fringe planet, dragging the peace officer along—also at the granda’s suggestion.

She finds herself on a strange world, with a somewhat deranged personality, quite possibly a killer, in her head, and partnered with a man from an advanced civilization who abhors killing. He is a Federation Peace Officer, captured by the slavers while attempting to bring them to justice. His task is complicated by the fact that he has sworn to avoid the taking of sentient life during the performance of his duties. He can and does, however, make vigorous use of non-lethal weaponry. Since, before leaving the ship, Katie had promised to help her co-captives gain their liberty, she and the alien peace officer find that they have a common cause.

But first they must find their way off the primitive planet and get to the Federated Civilization, avoiding the slavers who have been left on the planet to re-capture them. Their flight is complicated by the fact that the planet has had a global warming catastrophe some centuries back – the locals refer to it as the Drowned World. This has forced the inhabitants to revert to a pre-industrial state of development; however, they are a wily and resourceful people, mostly helpful, but they can also be dangerous.

Kati (to mark her escape, she adopts a slight name change) and Mikal seek a Federation beacon, which had been hidden on this planet ages ago, to aid in situations such as this, (in accord with a longstanding Federation policy for fringe worlds). They must embark on an arduous trek across two continents and an ocean, seeking the temple that holds the beacon. They travel on foot, by cart, by riverboat, by tall sailing ship, and on pack animals, always pursued by the dangerous slavers.
They must rely on their wits, guile, charm and acting abilities to avoid recapture, while their chasers have advanced technology and ruthlessness on their side. Fortunately, they are able to make many friends who help them along the way, and their quest becomes a series of adventures, both frightening and funny, and involving a cast of engaging characters.

To complicate matters, Kati finds herself falling in love with Mikal, the strange, handsome and amusing alien. He seems to be reciprocating, though they both struggle against an untimely romantic entanglement.

Will Kati and Mikal escape from the Drowned Planet? Can they ultimately bring the slavers to justice, as Mikal has sworn to do? Can they free the remaining captives of the slavers, as Kati has promised to do? Read this book and the rest of the series to find out all.

At about 200,000 words (equivalent to a paperback of about 400 pages), the book is an excellent value.

Kati 2 - On Assignment on the Planet of the Exalted

After narrowly escaping the pursuit of the slave trader Gorsh on Makros III, the Drowned Planet, Kati of Terra has arrived on the planet Lamania, the home world of her alien companion and fellow escapee, Mikal r’ma Trodden. The bureaucracy of the Lamanian Social Services, however, insists that the two be separated for half-a-Lamanian year, to ensure that this Wilder woman is not being exploited by her more urbane lover, who is also a Star Federation agent. In principle a worthy policy, it has left Kati without Mikal’s company while dealing with the loss of her connection to her young son Jake, and the knowledge that she will never be able to return home to Earth.

While exploring her new environment, she is confronted with the realization that Gorsh has spread his tentacles into the Star Federation. She identifies and rescues a young victim of the slave trade, using knowledge gained during her and Mikal’s period of captivity on Gorsh’s ship.

She agrees to take the lead role in an undercover investigation of the venerable Federation planet, Vultaire, which seems to be implicated in the lawlessness. Apparently the members of the planet’s upper class, known as the Exalted Citizens, have grown corrupt, some of them even taking up slave-ownership, alongside numerous other vices. With three companions, Kati forms the Unofficial Investigative Team into the Conditions on the Planet Vultaire. The team members make their way, clandestinely, there, and undertake their investigation while posing as an itinerant Entertainment Troupe. Secretly, they make common cause with the downtrodden locals, including elements of the resistance to the oligarchy.

Meanwhile, Mikal, the Federation agent, is sent to explore the Xeonsaur connection to the slave trade. It has to do with a captive member of the lizard species who has been forced to navigate Slaver Gorsh’s space ship through vast distances during its slave-snatching operations. Mikal too must make common cause; he does so with a beautiful female of the reptilian/humanoid race, the life-partner to the unhappy Xeonsaur captive.

Kati and Mikal must make their separate ways and overcome separate obstacles and dangers, before re-uniting in the struggle on Vultaire. Their reunion as battlers against the slave trade coincides with the end of their forced separation, ushering in a time of new connection. However, together on Vultaire, they need all the resources and ingenuity that they and their companions have, to stay alive, and to help heal the Vultairian society, as well as the very planet itself from the sickness that the corruptions have caused.

This is a full-length novel of about 260,000 words (equivalent to a paperback of about 500 pages). Please note that the Kati of Terra novels are written so that they can be read as stand-alone books. Kati of Terra Book 2 can be enjoyed by readers who have not yet read Kati of Terra Book 1. Naturally, we encourage people to read both novels to experience all the adventure and romance of the Kati of Terra series.

Kati 3 - Showdown on the Planet of the Slavers

Kati of Terra and Star Federation Agent Mikal R’ma Trodden join forces with the beautiful female reptilian, Xoraya, and the young Tarangayan mathematics and engineering genius, Lank, to chase down the Slaver Gorsh and bring him to justice. The evil Waywardian Gorsh was responsible for Kati’s abduction from Earth, along with numerous other victims from many other worlds; among these were many small children from Earth and other planets.

Their quest begins on an obscure Fringe Space Station which houses a reputable used space ship yard, the services of which they need if they are to journey along the Space Trade Lanes. Odd and dangerous events start to shadow them while they are on the Space Station, Qupar, and never really cease during the course of their mission. It begins to look like there is much more at stake than merely bringing to justice a slaver, and rescuing the people he has enslaved and sold - an unnatural and unspeakable evil of cosmic proportions may well be at the center of events.

The group gains new members, even while it loses Mikal and Xoraya into Gorsh’s hands - Kati and Mikal are once again separated, and have to struggle to perform their tasks apart from one another. However, neither of them is a quitter; they are resourceful and in love, so no force in the universe can keep them separated for long. The manner in which they and their allies overcome the obstacles that they face makes for an exciting, amusing, and romantic tale.

This is the thrilling conclusion to the dramatic story which began in Escape from the Drowned Planet, and continued in On Assignment to the Planet of the Exalted. Kati and Mikal can now take a breather from adventure - or can they? Time will tell.

This is a full-length novel of about 260,000 words (equivalent to a paperback of about 550 pages). Please note that the Kati of Terra novels are written so that they can be read as stand-alone books, so Kati of Terra Book 3 can be enjoyed by readers who have not yet read Kati of Terra Book 1 or Book 2. Naturally, we encourage people to read the entire trilogy to experience all the adventure and romance of the Kati of Terra series.

Beyond the Blue Door

Here's a tale of a haunted house, of a sort.

Really, two haunted houses are involved. But where does the greater evil reside - in the safe family domicile of our everyday world or in the creepy old abandoned farmhouse? And then there’s the question that we must all face eventually. What lies Beyond The Blue Door?