Category Archives: Blog

Interstellar Travel: Laser Sails and Tractor Beams

Interstellar Travel: Laser Sails and Tractor Beams

If Einstein is right, then it’s impossible to get to Alpha Centauri in less than 4.3 years.

If Newton is right, then getting there in a fraction of a human lifetime, though possible, is extremely difficult. Tsiolkovsky’s Rocket Equation tells us you would need an immense amount of propellant and an immense amount of energy to throw that propellant at high speed out the back of your ship. As in, $100 quadrillion dollars worth of antimatter per passenger.

It would be much simpler if you could leave the energy and propellant source behind. But how?

Enter the laser sail. Nutshell: light exerts pressure when it reflects off an object. Assemble a bunch of lasers and aim them at your ship. Turn the lasers on and they’ll accelerate your ship. Keep the lasers turned on until you reach your cruising velocity, then turn the lasers off. Your ship will coast at your cruising velocity until you reach Alpha Centauri.

Problem. How do you slow down?

In Avatar, ISV Venture Star carries antimatter engines to slow down on the approach to Pandora. Other powerful rocket technologies would work. By only needing to fire the engines when arriving, you cut your fuel requirement by 75%. We’ve cut the cost to a mere $25 quadrillion dollars of antimatter per passenger. Maybe there’s a cheaper way.

You could use aerobraking. The ship dips into the atmosphere of a planet or other large body and uses atmospheric drag to slow down. The Motie ship in The Mote in God’s Eye dives into the atmosphere of its destinatation star. Can it work? In theory, but you’re coming in at 40,000 miles per second or faster, and missing your insertion trajectory by just a few degrees either way can send you into a fiery death (and catastrophe for the planet or star you’re impacting at 0.2c) or hurtling off into space with no chance to get back to your destination.

Philip Norem’s galactic magnetic field turnaround concept. HT: Winchell Chung at

Back in the ‘60s, Dr. Philip Norem pointed out that if you charge your ship, the galaxy’s magnetic field will turn it. You can approach Alpha Centauri from behind. The lasers back at Earth will know when you’ll be in position, and can fire again. This time, the Earth lasers will slow you down. The only problem is if you haven’t mapped the galaxy’s magnetic field well enough, your ship wouldn’t turn onto the correct trajectory, the Earth lasers will miss, and your ship will coast into space with no chance to get back to your destination. Even if you can tune your ship’s charge to deal with unexpected galactic magnetic field strengths along your flight path, you still have to go a long way out of your way. (guesstimating from the picture to the right, 15-20 light years).









Physicist and science fiction writers Dr. Robert Forward came up with another way to use Earth-based lasers to slow your ship. It requires two concentric disc mirrors stacked together, with the smaller disc on the Earth side and the larger disc on the destination side. The smaller disc needs mirrors on both sides.

To decelerate at the destination, first detach the larger disc from the smaller. When the laser beam strikes the larger disc, light reflects and hits the smaller disc. This slows the smaller disc to a stop at the destination. The larger disc sails off at a fraction of light-speed into interstellar space.

Robert Forward’s three-stage there and back again laser sail concept. HT: Winchell Chung at

And if instead of one small disc, you use a medium and a small disc, you can make a round trip. Use your laser to return the small disc to Earth while the medium disc remains at your destination. See the picture to the left.

The biggest drawback is that the large (and medium) discs can only be used once. Thousands of square miles of mirrors wouldn’t be cheap. Still, it’s the best of these options.

Is there any other way to slow down at Alpha Centauri?

Yes. Tractor beam. (Ctrl-F for “tractor beam” after you follow the link. Huge thanks to Winchell Chung, Atomic Rockets’ proprietor, for all his work, including the three images I grabbed for this post).

Wait, aren’t tractor beams as impossible as faster-than-light travel? And even if they weren’t, how much energy would it take for a tractor beam on your ship to grab Alpha Centauri or one of its planets to slow down?

The answers, respectively, are no and wrong question.

Tractor beams may be possible. If a light beam with carefully tuned properties hits an object, the beam can pull the object toward the light source. Or, as first envisioned by physicist Victor Veselago, surfaces with negative refractive indices (NRI) are another. If you hit an NRI surface with light, the light would exert negative pressure on the surface, pulling it closer rather than pushing it away.

Granted, both concepts are far from implementation. But if either one works…

Scenario: lasers near Earth accelerate the ship toward Alpha Centauri. The ship coasts for a while. Then one of the following scenarios occurs:

  • The laser controllers at Earth calculate the date the ship needs to start decelerating, and about 4.3 years before that date, the laser controllers fire a beam of tuned laser light that will pull the ship toward Earth, i.e., decelerate it.
  • Just before the deceleration start date, the ship deploys an NRI sheet. Earth’s lasers fired 4.3 years ago. The laser light strikes the NRI sheet and decelerates the ship.
  • Both tuned light and an NRI surface are used.

Regardless of scenario, the result is the Earth-based laser acts as a “tractor beam” and slows down the ship at Alpha Centauri. No shipboard rockets, no aerobraking, and no galactic magnetic field surfing required. You could also use the Earth-based laser to accelerate the ship back to Earth at the end of the mission.

(Of course, the ship is trusting that Earth will turn on the laser beam at the right time. But for my purposes, that’s great. Stories come from where things can go wrong).

Whether the tractor beam approach is better than Dr. Forward’s multi-stage structure would come down to cost. Big throwaway mirrors may well be cheaper than giant banks of tunable lasers or big NRI sheets. Especially because we would only need Earth-based lasers to slow our ships until the human colony at Alpha Centauri builds its own bank of lasers to decelerate incoming ships and accelerate ships back to Earth: not many missions to pay off the R&D costs for tunable lasers or NRI sheets.

Even in deep space, money talks.


“Take the Shilling” in CYBORG CITY ebook bundle – preorder now – on sale September 29, 2017

Ebook bundles are a great way to find new authors in genres you love. My novel Take the Shilling will be part of the Cyborg City ebook bundle (Amazon, Kobo, and more presale links at Bundlerabbit). That’s 11 exciting science fiction stories for just $3.99! Here’s the full list of titles.

– “T.I.N. Men” by Russ Crossley
– “Club Anyone” by Lou Agresta
– “Take the Shilling” by Raymund Eich
– “Technological Angel” by Barbara G.Tarn
– “Walking on a Sea of Clouds” by Gray Rinehart
– “Demon Days” by Carl S. Plumer
– “Coffee Cup Dreams (A Redpoint One Romance)” by J.A. Marlow
– “Inside the Sphere” by M. L. Buchman
– “Imposters” by Blaze Ward
– “Programmed for Danger” by Karen McCullough
– “The Suit” by David Sloma


Go to your preferred ebookseller to preorder now or buy on September 29. Enjoy!

In Memoriam: Jerry Pournelle

Some people you might never meet in person, but you get a strong sense of who they are from their writing. Sf writer, computer enthusiast, and technology strategist Jerry Pournelle, who died last week at the age of 84, was one of those.

You’ve probably heard of his first collaboration with Larry Niven, the 1974 novel The Mote in God’s Eye. It’s probably the best novel to not win either the Hugo or Nebula (beaten for both by LeGuin’s The Dispossessed). Don’t take my word for it, Robert Heinlein called it “possibly the finest science fiction novel I have ever read.” (And if you find Robert Heinlein’s praise a strike against it, both my blog and my sf are probably not for you). Having first read Mote after reading almost everything Niven had written to that point in my life, Pournelle’s distinctive worldview was quite clear. Sf had featured galactic emperors before, but in a “once upon a time” fashion, obscured from our present era by mythic epochs. Pournelle’s galactic empire emerged quite clearly from an alliance between the US and the USSR’s combined spacefleet (!) and a monarchial human colony world. And not only was it a real galactic empire, but a high church Christianity was its state religion! Definitely against the grain of most ’70s sf, with its rational computers governing spandex-clad, hedonistic atheists.

Other aspects of the Niven-Pournelle collaborations that have a strong (to me) Pournelle fingerprint are the identity of the virtuous pagan in Inferno, the techno-feudalism of Oath of Fealty, and the battle to save high-tech civilization in Lucifer’s Hammer.

He also wrote solo novels and stories in the CoDominion/galactic emperor setting of Mote, edited the There Will Be War series (being republished and continued by Castalia House), blogged about computers and politics, and a lot more. Whatever the topic, you could tell Pournelle had wrapped his mind around it and had something important to say.

But the single most distinctively Pournelle thing I ever read isn’t sf at all. It’s A Step Farther Out, a collection of “essays on technology, civilization, and saving the world” that mostly appeared in Galaxy magazine during the editorship of Jim Baen during the ’70s.

For those who weren’t there or don’t remember, the ’70s were much like today–an era when the elites proclaimed that the good times (for the 99%, that is) were over, when the most sensible solution to energy shortage, nuclear power, was demonized by facile word-flingers in the pay of anti-American propaganda machines; when we were told that only massive economic redistribution (again, from the upper parts of the 99%, not the elites, to the world’s impoverished billions) could stave off catastrophe.

Pournelle demolished the doom-and-gloom narrative in about a hundred pages.

Then he pointed out how we could get to space, and how we could live once we got there.

While I’m not convinced by the asteroid mining “cash on the barrel” arguments for space settlement, I still think space settlement is utterly possible. Pournelle’s essays are a major reason why… and a major reason my blood boils when I see the self-centered incompetence and corruption of the Western worlds’ ruling class.

I’m pretty sure Pournelle’s blood boiled at that too.


KDE’s krunner is even more awesome than I thought

When I switched to Linux, one of the reasons I adopted KDE as my desktop environment was the krunner launcher. Hit the Alt-F2 hotkey (or remap it to Alt-Space or the “My Favorites” button on a Microsoft Natural 4000 keyboard) to open the krunner interface, and start typing the name of the app you want to launch. Or the file you want to open in its default app. Or the folder you want to explore. Or the arithmetic you want to quickly calculate. Or… you get the idea. Krunner is incredibly powerful and much faster than moving a mouse, clicking on a menu button, moving down, moving over, and clicking.

But just the other day I discovered something even better about krunner. If no window has focus, just start typing the app name, file name, etc. and krunner will open automatically. No hotkey required. Think of the hundreds of millliseconds I can save multiple times a day….

Okay, not the most amazing lifehack ever, but still cool.

There Goes My Streak

After correctly predicting the last four SFWA Grand Masters (here and here), I missed badly in 2017. No, it wasn’t Dan Simmons. Instead, Jane Yolen won this year’s honor.

My overall response is meh. Nothing against Ms. Yolen, but I think she’s the first Grand Master whose books I’ve never read. Wait, check that, we have some of her “How Do Dinosaurs….” series of children’s books around the house.

Time to climb back on that horse (or that limb) and make a prediction for 2018. Not Simmons again; instead, I’ll predict someone whose sf output from the ’70s and ’80s had moments of great strength, and who has dominated the blockbuster fantasy mindspace for about 20 years now. (Remember, the F in SFWA stands for “Fiction and Fantasy”):

George R. R. Martin.


Congrats to C.J. Cherryh, 2016 SFWA Grand Master!


Congratulations to C.J. Cherryh, multiple award-winning author of Downbelow Station, Cyteen, the Faded Sun series, and a bunch of other sf and fantasy works. Here’s a link to the official announcement

I’ve now predicted the last four SFWA Grand Masters. Click on last year’s prediction post and follow the links back from there.

Ok, who will be named SFWA Grand Master in 2017?

Dan Simmons. The award-winning Hyperion series and the Ilium/Olympos diptych are big, bold space opera with extra helpings of literary allusion. He’s also written a lot of horror and historical/supernatural. Even though not core sf, those genres do have a crossover in readers and writers and should merit consideration. He’s had a prominent career for about 35 years.

Any other candidates come to your mind? Make their case in the comments.

An Exterminator-Free Galaxy

Quoting Nick Land, expat Brit philosopher in Shanghai, “The cosmic reality visible to us is characterized by an intense, efficient aversion to the existence of advanced civilizations.” He calls whatever it is that prevents the existence of advanced civilizations “The Great Filter.” Longtime science fiction readers familiar with Gregory Benford’s Galactic Center series or Fred Saberhagen’s Berserker universe will understand what Land means when he dubs the Great Filter “the Exterminators:” Killer robots sent out to destroy advanced civilizations.

But on the bright side, Exterminators probably don’t exist, because if they did, the human race would already be extinct.

You might have heard of Von Neumann probes. A self-replicating interstellar probe journeys to a nearby star, makes copies of itself, and those copies journey to nearby stars. Repeat until you have a probe in every stellar system in the galaxy. Even if the probes’ net velocity is only 1% of the speed of light, they would reach every star system in the galaxy within 10 million years.

Given that the galaxy is about 13.2 billion years old, filling the galaxy with self-replicating probes would take but a moment of astronomical time. Look at it this way: if Earth is typical, and a planet needs to exist for (rounding) 4.2 billion years for intelligent life to develop a civilization capable of launchign a self-replicating probe, then it would take just one alien civilization arising in our galaxy in the last 9 billion years for there to be a probe somewhere in the solar system right now.

Now suppose that one alien civilization built probes with a straightforward mission: destroy other intelligent species while those intelligent species are stuck on their home planet, to ensure that one civilization can exploit all the resources of the galaxy. If true, their killer probes would have destroyed us a long time ago. Maybe even before there was an us.

Since that clearly didn’t happen, we conclude that zero alien civilizations built Exterminators.

Wait, their killer probe might be here, waiting to destroy us
No, because the Exterminator has nothing to gain by waiting. Over three thousand years ago, human beings built plainly artificial objects visible from low earth orbit. A clear signal that a species had evolved tool use and enough social organization to engage in massive engineering projects. Why wait to destroy that species? Maybe it will take four thousand years for that species to build its own Von Neumann probes, but what if it takes them four hundred? Or forty? Don’t take that chance. Destroy them now.

Since ancient Egypt wasn’t wiped out by a hundred-mile-wide asteroid impact, the sun going nova, or a never-ending army of implacable battle robots, “no killer probe” is the safe bet.

What does this mean?
Looks like the Great Filter lies behind us. Whether life is rare, or planets rarely stay habitable for billions of years, or the metabolic expense of intelligence rarely conveys a selective advantage, or tool use is rare, doesn’t matter. We are probably the only intelligent tool-using species in the galaxy. The handful of human beings who will ever get past low earth orbit will be like the Aborigines crossing the Torres Strait or the First Nations pushing south of the Ice Age glaciers, entering a vast, resource-rich realm without competition.

Except with each other, which for science fiction writers is a good thing. Fodder for a million stories….

Speaking of which, I should get back to work. Till next time.

A treasure trove of hard science fiction ideas

While researching a story I’m currently writing about terraforming, I found The Paul Birch Web Archive. If you’re looking for big, hard science fiction ideas, follow the link now and get your mind expanded. Want to speed up Venus’ rotation to give it a day 24 hours long, at the low low price of $20 trillion? Want to build a bridge across the Pacific Ocean or up to low Earth orbit? Want to sail the solar wind and interstellar medium, and reach Alpha Centauri in 400 years? Want to take a one-way faster-than-light trip into the future?

The link again is The Paul Birch Web Archive. Enjoy!

“New” Fantasy Novel

Pen names are one of the many aspects of the publishing industry in flux these days. Formerly, traditional publishers would typically demand writers change pen names when switching genres. Marketplace confusion was the stated rationale: if “Max Steele” mostly wrote hard-boiled detective stories, then switched to a cozy mystery, where Grandma sets down her knitting to quietly solve a murder, his hard-boiled fans picking up the cozy would be angry at a bait-and-switch. Better for Mr. Steele to publish the cozy under a pen name like “Maxine LaFleur.”

Sensible? Maybe. But by insisting a writer use different pen names for different genres, traditional publishing effectively said readers buy based on writer, but are too dumb to pay attention to genre (cover art and back cover copy). At the same time, traditional publishing said the opposite: readers only buy based on genre, not on writer. In other words, Max Steele’s hard-boiled fans would never read a cozy, even one written by a writer they love.

But in the new world of publishing, where someone can run a world-wide publishing empire from the /home folder of his hard drive, the traditional ways of doing things are being being examined, tested, and if they fail the test, discarded. And those pen name tests? They fail.

I don’t know you, but if you’ve found my blog, I’ll assume you’re pretty darn smart :). Smart enough to notice the cover and deduce the genre before you buy a book. Spaceship? Science fiction. Soldier holding giant laser rifle? Military science fiction. Castle? Fantasy.

And if you flip the book over and read the back cover, or scroll down to the ebook product description, you’ll confirm your deduction. Scattered wormholes, half the settled galaxy, neuroscience: science fiction. Kingdom, magic: fantasy.

So the idea that readers don’t pay attention to genre is an insult to your intelligence. Since I know you’re smart, I won’t do that.

And readers don’t buy only on genre. My own buying habits prove that. You might have seen Larry Niven’s name in my Inspirations sidebar. As a teen, I was a huge fan of his science fiction, and then I discovered the Warlock stories and The Flight of the Horse. The latter is a whimsical dystopian science fantasy; the former are straight up sword & sorcery.

I almost didn’t buy those, until I realized something. They weren’t fantasy; they were fantasy by Larry Niven. His perspective, his voice, the kinds of characters and conflicts he wrote about–all that was going to be the same, whether the cover had a spaceship or a Pegasus, whether the spine had the fine print “Science Fiction” and “Fantasy.”

Maybe another way of putting it is the writer is the genre.

So, if you like my science fiction, not simply because it’s science fiction, but because of my voice, my perspective, and the types of characters and conflicts I like to write about, then I want to make it easy for you to find all my books. Even the ones with castles on the cover, kingdom and magic in the product description, and “Fantasy” in small print on the spine.

With that in mind, I’m pleased to announce the (re)release of my first fantasy novel, A Prince of the Blood. Previously published as by “Eric H. Munday” (I can anagram with the best of them), it’s now available under my name from better booksellers around the world. Read on to learn more.




A king inclined contrary to nature.

A foreign-born queen confined to the palace.

A kingdom desperately needing an heir.

Two courtiers ask Keladon, retired battlemage and the king’s bastard half-brother, to impregnate the queen. His sense of duty to the kingdom sends him to her bedchamber. But he must do far more to stop a conspiracy of magic and murder threatening the kingdom’s survival – and the woman he comes to love.

Purchasing information at CV-2 Books

Larry Niven named SFWA Grand Master

Here’s the official announcement.

Larry Niven

Larry Niven, photo by David Corby

Nothing more needs to be said. One of the writers who led me to become a lifelong sf reader is getting a well-deserved accolade. So well-deserved I predicted it three years ago. (I’m also glad to see the recently-erupting political fault lines in the sf community didn’t ding him as I feared they might).

I’ll update my most recent prediction and predict C.J. Cherryh will receive the Grand Master award in 2016.