Have you ever gone to a carnival and tried out the shooting gallery: the ones where you use a BB gun to plink over metal duckies as they swim across a shelf in the back of the booth?  Even if the carney has not messed with the sights so the BB does not go where you think it will, you may have found hitting a moving target to be a challenge.

If the carnival shooting gallery isn’t challenging enough, try skeet shooting – with a rifle, not a shotgun – and you’ll get closer to the challenge of shooting a space ship from one planet to another, let alone from one star to another.

Galaxy M1 Courtesy NASA

I found a comment left on one of Greta van der Rol’s blog posts interesting: the discussion was of a space ship coasting to a stop in space because the engine failed.  This will not happen, but he asked, “Coast to a stop – relative to what?” And he made the point of my next post in an elegantly succinct manner. The biggest issue in flitting around space is that everything is in motion.

If we board an aircraft in New York and fly to London, noodle around for a week then fly back; New York is almost always right where we left it.  We can use landmarks, compass headings & distance and now GPS satellite signals to travel from one point on our globe to another with little risk of missing our mark – unless we’re using iMaps: then it’s hard to say where you will end up!  But in outer space – even interplanetary space – things are very different. Everything in our solar system orbits around our sun.  We can use the sun as one fixed point of reference, but everything else is in motion and moving from one place to another requires a lot of complicated mathematics to calculate a trajectory that will put us in the place our destination will be when we get there.  In marksmanship terms, we must “lead the target”: shoot for where it will be, not where it is now.

Once we leave our planetary system, things get a bit more strange, for our sun is no longer a fixed reference point; our solar system is in motion relative to the rest of the galaxy.  If you think finding your car in the shopping mall parking lot is a challenge, how would you feel if sections of the lot could move around?  What if light pole 6B was not guaranteed to be 4 rows to the left of the Penny’s main entrance, but could be closer to Sears when you were ready to leave?  That would throw a wrinkle into things wouldn’t it?  I’d be using the valet parking for sure!

We hop on an interstellar space ship bound for a distant star, noodle around for a few months collecting souvenirs and photographing the local flora and fauna, then head back home.  But wait: home is not where we left it!  Now what?

As Sci-Fi writers we can simply type, “Ensign Saunders, plot a course.” and we’re on our way.  No need to wallow around in the details of interstellar navigation.  But, isn’t this a bit like saying, “I have a calculator, why do I need to learn the multiplication tables?”  Sometimes, as a writer, wallowing in the details can add depth to your writing. So, how might we chart a galaxy so that our ships could reliably navigate through it?  What would we use for landmarks when the land is fluid?

Navigation by Coordinates.

There is a galactic coordinate system in use now. The galactic coordinate system is a celestial coordinate system in spherical coordinates, with the Sun as its center, the primary direction aligned with the approximate center of the Milky Way galaxy, and the fundamental plane approximately in the galactic plane. It uses the right-handed convention, meaning that coordinates are positive toward the north and toward the east in the fundamental plane.^[1]This is a great way to plot celestial bodies as viewed from Earth, but I think we’ll find its usefulness limited once we start bebopping about in other neighborhoods.

Star Maps

A computer model of the galaxy could, with sufficient memory and processing power, keep track of the gazillion stars and other celestial bodies in our galaxy.  Such a computer will need to be powerful enough to make Oak Ridge National Laboratory’s Titan supercomputer (which resides down the road from me in Oak Ridge Tennessee, and is currently the world’s fastest computer) look like a child’s toy.  But if you can plunk down a You Are Here pin on the map, you could calculate a course that will put you in the right spot when your destination gets to where it will be when you get there… and, hopefully, avoid hitting anything substantial while en route.  This is fine if you have a careful record of where you have been, but how do you figure out where you are if you’re not sure?

Navigating by Beacons

A network of beacons or satellites that emit a constant signal could be established and used as guide posts.  Of course the beacons will be moving along with everything else, but if LaGrange points are chosen so the beacons can float along in relatively fixed positions relative to the rest of the galaxy their guidance should be useful.  The bigger problem is that radio signals will take tens of thousands of years to span interstellar space and laser disperses quickly.  Both signals are likely to become lost in the galactic background noise, making them of use only at relatively close range anyway.  And the cost of setting up and maintaining a system of intergalactic lighthouses… let’s not even go there!

Pulsar_Chandra Crab

A better system would be to use powerful, natural phenomena as sign posts.  Like pulsars.  The European Space Agency’s Ariadna initiative is examining the feasibility of navigation relying on millisecond pulsars; rotating neutron stars that spin faster than 40 revolutions per second.  Each star is unique in its timing interval.  Locate three of them in your proximity and you can triangulate your current position on that wondrous computerized star map your ship carries around.  A ship with optical sensors could do this autonomously.  Galactic GPS.

Using pattern recognition software and constellations comes to mind as well.  But again, as we travel around, and view the constellations from different angles, their shape will change.  That pat-rec software will have to be really sophisticated to handle that!

Other Ideas?

My money is on the pulsars and a star map in a bio-mega-super computer, but I’d be very interested in hearing any other ideas you might have.

Others in this series:

Science Fiction Fact & Fancy: Space Travel
Science Fiction Fact & Fancy: Propulsion-Engines
Science Fiction Fact & Fancy: Propulsion-Exotic
Space: A Really Dangerous Place to Live
Science Fiction Fact & Fancy: Navigation

I recently post another of my Science Fiction Fact & Fancy posts that talked about the hazards of living and working in outer space – I mean, beyond the obvious, absolute vacuum thing.  Today I found this trailer for a new movie about to come out called Gravity, and I thought it was worth tossing it in here as a follow-up to that post.  See… told ya!

If it won’t play, watch it on YouTube:

Others in this Series:

Science Fiction Fact & Fancy: Space Travel
Science Fiction Fact & Fancy: Propulsion-Engines
Science Fiction Fact & Fancy: Propulsion-Exotic
Space: A Really Dangerous Place to Live
Science Fiction Fact & Fancy: Navigation

We often think of outer space as being a great big empty nothing littered with trillions of stars and their attendant planets.  All big enough to avoid and with lots and lots of empty void between them.  Other than having to traverse the vast distances, empty space offers few dangers, right?  Very wrong!  In this episode of my on-going series about the fact and fancy of science fiction we’re going to take a look at what life for human beings would be like in outer space.

Orbital Space Dangers

First, let’s look at the area of space with which we are most familiar: that shell of space immediately surrounding our own planet.  The most prominent problem here, or in any part of outer space, is the awesome destructive force of a near perfect vacuum.  Any craft sent into space must be built to resist the forces of the interior atmosphere wanting to rush out into the vacuum surrounding it.  Even a pinhole in the hull can turn into disaster if the material is not strong enough to resist the erosive, tearing forces of hydrodynamics as the air screams out the hole.

Orbital space has another main issue: space junk.  Human beings have become experts at trashing virtually every environment they can get to, including the space around our planet.  NASA says that currently there are approximately 6,300 tons of man-made debris orbiting the earth; some as small as a fleck of paint, some as large as the defunct Vanguard 1 satellite.

What harm can a fleck of paint do?  When it’s traveling at 17,000 miles an hour, even a paint fleck can do serious damage.  Early in the space shuttle program, during the STS-7 mission, a tiny paint fleck hurtling through space hit a shuttle window, causing so much damage the entire window had to be replaced.  There are tens of thousands of junk bits in Earth orbit, some just flakes of paint, but some are nuts or bolts, tools lost by space walkers, discarded fuel tanks or rocket stages of previous space craft, even whole satellites. Read the rest of this entry »

This week I will continue with my examination of space travel technology, focusing on propulsion; but this time looking at the less commonly discussed and written about technologies.  Again, I remind you, reader, that I want only to help understand current theory – perhaps open some doors – not quash your imagination.

Solar Sail Propulsion

via www.NASA.gov

As a sailboat enthusiast from way back I know well the elegance and economies of using wind to power a craft.  But light?  Yes.

The idea of powering spacecraft with sails harnessing the “solar wind” was first proposed by Johannes Kepler who observed that comet tails point away from the Sun and suggested that the sun caused this effect. In a letter to Galileo in 1610, he wrote, “Provide ships or sails adapted to the heavenly breezes, and there will be some who will brave even that void.” ^[1]

The technical term is Solar Radiation Pressure and it is made up of photons (light) and elemental gasses.  The sails must be mirror-like reflective to utilize the photon energy.  Although the SRP or “Solar Wind” blows at (or near) the speed of light, its actual impetus is rather low.  It will take HUGE sails to pull a space craft of any size through the heavens.

Two launch conditions are being considered both assume that the craft itself will be either boosted into orbit on a rocket or built in orbit.

The first is to unfurl the sails (see video below) and allow the Solar Radiation Pressure to do a slow-but-steady push on the sails.  The craft will pick up speed as the SRP continues to “blow” against it.  But, high speeds would probably not develop before the craft is so far away from the sun that the push it gets is diminished.  Best speed with this is estimated to be 90 km per second (km/s).  A modification of this is to use microwave or laser emplacements to give the craft a “shove” at certain points to bring the speed up to 30,000  km/s (1/10 the speed of light) and bring interstellar travel into the realm of possibility. Read the rest of this entry »

Via Wikipedia commons

In my last post on this topic (Space Travel) I mentioned that many Sci-Fi authors borrow heavily from naval vessels and aircraft in depicting the behavior of space craft in their writing.  And while this sometimes irritates me too, I encouraged authors to write what they dream; don’t pay too much attention to us hard-SciFi’ers, because something is impossible only until someone does it.  And humankind has done the impossible many times already.

However, for those who would like to put a more factual edge into their Sci-Fi writings, I will continue to look at some of the specific areas that draw fire by being more science fantasy than science fiction and ways to lessen this by employing currently viable technologies as a starting point at least.  This week I want to look at propulsion systems: engines.  Because this is a blog post, not a treatise, I’ll need to keep it brief and select the most suitable topics – or serve espresso and cookies with each reading to keep you from wandering off. Read the rest of this entry »

The learned men in particular site the laws of physics holding up such ideas as bodies in motion, vectors of thrust and the lack of resistance in the vacuum of space.  Others point out that aerial combat craft use air and wings to swoop, dive, roll and dodge during maneuvers.  But in space there is no air, so swooping will be all but impossible.  The designer also focuses on the vacuum and its terrible anti-pressure effects on structures that float through it. He claims that aircraft carrier sized ships traveling through space are highly unlikely just because of the structural logistics involved. Read the rest of this entry »