THE SOULS OF THE DAWN (The Art of Moving Stars)

Chapter 2 — Part II: The Bug Man In Blue Jeans

Catch up on Part I here.

Building a great tower is always done
One brick at a time.
Dark body of an asteroid with sun behind it attached to four flat disks.
Light Sails Towing an Asteroid

Ever wonder how a civilization could move a star? I asked The Bug this question and this was his answer.

Let us start at the beginning. Any space born race will have sever constraints on their resources and must of necessity become very frugal, whereas, any planetary born race sees space flight as virtually free after the huge effort necessary to launch a vehicle into space in the first place. This is easily seen in how each constructs and uses transportation vehicles. The planetary born use powerful engines and consume great quantities of reaction mass to get to their destinations as fast as possible. The space born on the other hand prefer using light sails. It does take more time to travel, a lot more actually, but when done properly it uses very little reaction mass.

We see an interesting affect on each race. The planetary born are quick to return to the arms of gravity, but the space born accept the fact that their life is in the vast spaces. The planetary born build large open vehicles and layer them with radiation protection while the space born build small cramped vehicles and wear their radiation protection. The planetary born eat tasteless packaged food with indefinite shelf life while the space born prepare delicacies from recycled biomass. Needless to say, the space born crews tend to favor compromise over conflict, but do not think that they are compliant when treated unfairly. Due to the shear boredom they face, they seem to be uniformly born game players and story tellers from an epoch of heroes and adventures. Also when dealing with them, be aware, many do not really have a sense of privacy and some do not even have a concept of inhibition.

Given the lifestyles of space, the light sail is the first choice for dealing with asteroids and small bodies in space. It must be noted that those living on planets generally do not have enough time to intercept these inbound dangers with anything as slow as a light sail and consequently must rely on rockets for their protection. Some space rocks are quite valuable, especially if ice is present, but most space debris is not. If you are curious about why anyone would compete over these seemingly worthless rocks, answer the question of why nations compete over farmland. It is after all just dirt.

There are some things to understand about light sails. The first thing is easy to understand, the inner surface of the sail must be highly reflective. Then we have our first disappointment, light sailing takes a tremendous amount of sail area to move a tiny amount of mass. When we finally unfurl them, we might like to think of them as shaped like a parachute to maximize the collection of light, but light does not work that way. Light must bounce off a perpendicular surface to get full effectiveness, so light sails tend to be flat with cross members holding them rigid. Our next misconception is that light sails behave like wind driven sails on ships of the sea. They do not. There is no way to tack into the light stream as we would with the wind; however, before you think all is lost, I have some good news, they can be oriented to either pull with acceleration or drag with deceleration… Lest I put you to sleep, I will let you research the technical material further on your own.

If you think you have it all figured out, I must warn you, asteroids are dangerous animals. It is rare to find a space rock that is not rotating or tumbling in at least one axis. These bucking broncos can rip sails and tangle guide cables if not stabilized. One might think that you just attach a cable and pull with a light sail to remove unwanted rotation, but one might learn an important lesson instead, as the rock winds the cable around its body and pulls the light sail toward itself. (Hopefully, we have a hero at the ready to cut the cable just in time.)

The proper way to remove this motion is to apply counter force. One clever method is to place reflective material on any surfaces exposed to the sun that travel toward the light stream and let light pressure do its magic. If absorptive material is placed on the opposing faces we can get more efficiency. This being time consuming, one might perform the setup and return later when the rotation is removed, but not too far into the future or the body will be turning in the opposite direction! Another method would be to use parabolic mirrors, maybe in a configuration converted from the light sails themselves, to super heat portions of the body and create reaction mass to counter the original rotation. Or one could generate power from solar panels on the light sail and shoot the body with lasers for the same purpose.

Having light sail travel and asteroid transport within a solar system is certainly a plus for the space born, but it is not the end of the usefulness of this technology. If the sail material can withstand a close approach to the local sun, the light sail can be used to launch vehicles into interstellar space and eventually other solar systems. The process must start in the vicinity of the star to get the maximum ramp up before the sail gets too far away to effectively use the solar light stream.

To overcome this, the light sail can be incorporated into boost stations. Unlike satellites, a light sail can be put into a stationary position anywhere it can get sunlight. It is a delicate balancing act, but not impossible if it has a good control system. Using solar panels the boost station can power lasers that can be adjusted to any direction to push light sails further and faster. Even the planetary born could use these boost stations to push dangerous bodies away from their world or maybe destroy them altogether. In addition, everyone can benefit from the energy generation, especially planetary surfaces wanting to avoid global heating. We must be realistic though, like everything that has great potential for for good, these stations also have great potential for harm. Imagine a conflict with these used as weapons.

The most impressive use of light sails would be for moving stars. It is a simple concept. Huge arrays of light sails would dangle massive objects as near the surface of a star as possible. On the surface, it looks like a perpetual motion scheme, but if you understand the energy driving the system is actually being generated by the star, it makes more sense.

Flat light sail attached to a drag mass directed toward a sun.
Light Sail above a Star Using a Drag Mass

There are of course dangers involved. A star is not a solid body, but instead multiple layers with different densities. The act of setting up a light sail with a gravity puller will induce a bulge in the outer layer of the star, and only after decades will the deformed star actually start to move. There will never be enough mass available to make the process efficient. Expect plenty of problems. Stars can be erratic. Solar flares could easily destroy the entire array in a few hours. No sail material is immune to degradation, so constant manufacturing and replacement would be necessary. Essentially, an army of automatons would be needed to make it work. The process of moving a star would take thousands of years. Probably the only thing that would actually be possible might be to knock a star into a new trajectory.

Moving the star is probably the easy part. Stopping the process would need to be performed in a controlled manner. If the light sail array were removed instantly, i.e. via a solar flare, the instability of the star would most likely be violent. One would expect intense solar flares for decades if not centuries. And of course, if we are moving a giant, we would expect anything up to a coronal mass ejection or possibly even a nova.

This story is part of the series called the The Bug Man In Blue Jeans. If you view my Lists and About data, all the other stories can be seen.

Less fictional information about Solar Sails can be found here.



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JB Johnson

JB Johnson


I am a science and technology junky and this is my place where I can share my ideas.