Friday, December 18, 2009

Fantastic Future Friday: Skipping a Century

This week I decided to jump forward about a century in human progress (or 150 years with current R&D budgets) and talk about a project for the 22nd century. I’m sure Stephanie will correct my rocket science figures so make sure to read her notes.

Two things limit space travel right now: Money and Specific Impulse. The money problem is complicated but the Specific Impulse problem is fair straight forward.

There are three types of rockets currently being used, Solid, Hybrid, or Bipropellant Rockets. Their effective exhaust speed, how fast stuff shoots out the back making them go forward, is between 4 kilometers per second and 4.7 kilometers per second. As a general rule rockets are most efficient when traveling about or slower than their exhaust speed, or Specific Impulse. Once a rocket reaches twice its Specific Impulse (it’s a more complicated formula than that, but doubling it gives a ballpark figure) its efficiency drops dramatically.

So our current generation of rockets can just break Earth’s orbit and go into their own orbit around the sun. In order to go faster they need to use a gravitation boost, which is why most space missions swing by Venus or Jupiter.

Using our current chemical rockets, trips to other planets are governed by orbital mechanics and it will take several months to reach Mars and Venus, years to go to the Outer Solar System.

Our next generation of rockets is Ion Thrusters; they use a stream of electrostatic ions for thrust. They have very low thrust so they can’t be used to go to orbit, but their Specific Impulse is much higher than the current generation of rocket. 15 kilometer per second for the NEAR probe, and a hypothetical exhaust speed is 80 kilometers per second.

As this science advances Ion Thruster powered rockets could (slowly) reach 160 kilometers per second opening up the inner solar system with trips taking a few months, mostly spent accelerating to the top speed.

To reach the outer solar system it would still be at least a year to reach Jupiter taking the slow acceleration into account. Several years to go to Saturn and beyond.

Skipping forward to at least the mid-21st century there are designs for Magnetic Field Oscillating Amplified Thrusters, using fluctuating magnetic fields to induce density waves in electric conductive media. These send magnetic fields over a material to hurl their atoms out at great speeds, around 130 kilometers per second. So a ship using this technology could reach 260 kilometers easily.

The problem with these rockets is they need a powerful energy source, current plans envision using Nuclear reactors to power these. In my book “The Setting Earth” I had them powered by Helium 3 fusion reactors.
These rockets could open up the inner solar system and reduce travel time between the planets to weeks, but it would still take months to reach Jupiter and years to go beyond.

With those limitations in mind here is the big project for the 22nd century, because my ideas for 21st century projects are too small.

In order to open up the Outer Solar System humanity will need a few really fast rockets, in order to have faster rockets we need a huge energy source. Luckily we happen to have one lying around, The Sun.

As space based solar power is advanced in Earth’s orbit we can use that on a larger scale at Mercury’s Lagrange Point, the spot in Mercury’s orbit where an object will always be between Mercury and the Sun. In Mercury’s orbit the Sun’s Power is roughly 10 times the power it is here on Earth so a large Solar Power Station could generate huge amounts of power.

Making a Solar Power Station that put Mercury and the surrounding 100 kilometers around it into its shadow could easily generate 180 terajoules per minute of power, roughly the same as the largest Thermo-Nuclear bomb ever made. This power could be harnessed to make a huge particle accelerator capable of producing one gram of matter and one gram of anti-matter. The anti-matter could be used to power more advanced rockets with a Specific Impulse of around 1,000 kilometers per second or a top speed of roughly 0.6% of the speed of light.

This would get the travel time to Saturn down to a couple weeks, and even the outer reaches of the Solar System, the Kuiper belt objects would be a few years away.

The staff of this Solar Power Station/ Anti-Matter generator would probably like a nice place to stay and that is where the size of the project helps. By only taking 90% of the Sun’s light to power the station, the same amount of light that hits Earth could be used on Mercury. By only extending the shadow of the station 100 kilometers to Mercury’s sides, comets could be placed in orbit.

When these comets come into full exposure of the Sun they will melt into water vapor. In Mercury’s orbit this water vapor will be broken into Hydrogen and Oxygen. The Solar Wind will get rid of the hydrogen and the Oxygen will slow break orbit and fall to the planet giving it an atmosphere. By constantly feeding more comets into Mercury’s orbit we can turn Mercury into an Earthlike planet with the same land mass as Earth.

With a few million people living on Mercury and nearly unlimited energy they can work on the next big project.

The speed limitation of Anti-matter powered ships is 0.6% of the speed of light. At that speed it would take roughly 800 years to reach Alpha Centauri, our nearest neighbor with stars that are sort of like our own.

To reach the stars we need an even faster ship. Having a Solar Powered Particle accelerator in Mercury’s orbit would allow us to make that.

Using the Particle accelerator as an atom smasher, it is possible to reduce over a million tons of matter into quarks and reassemble them as higgs boson particles. These particles respond only to gravity and none of the other atomic forces, so they could form a semi-stable black hole.

This artificial black hole would slowly break down emitting Hawking’s Radiation. A perfect mirror could be used to reflect this radiation making the ship attached to it have a specific impulse of the speed of light.

A ship powered by Hawking’s Radiation could accelerate at one Earth’s gravity for a year and reach 90% of the speed of light. That would put the nearest stars within a decade travel time of Earth.

With the travelers experiencing time dilation they would only feel the time it took to accelerate plus a few months, even though for the rest of the solar system time would act normally. It is kind of like college.

That is the upper limitation of rocket science. Going any faster would need to use something else, unfortunately at this time there is nothing that I see as practical to replace rockets at the present time.

In the 23rd century scientists will have to look beyond rocket science, so Stephanie your job will only be around for the next 200 to 300 years.


Stephanie B said...

Well, pooh, I could have sworn I left a comment.

Since this is all speculative, I can't say anything's impossible.

But I'm a little skeptical that Mercury is salvageable.

Project Savior said...

Oddly enough I think the perfect mirror, one that reflects 100% of the radiation that hits it, will be the toughest challenge.
Everything else I've mentioned (except the higgs boson particles) are just a matter of scale over what we are doing now.
Mercury will be a tough planet to terraform, but not the toughest. After the holidays I was thinking about exploring how to terraform the planets.