Tuesday, 4 December 2012

Sailing the Quantum Sea on a silicon wafer.

 The voyager has finally poked its nose into interstellar space having finally pierced the Helio sheath it not quite out of the Solar system yet but it is out of the sun's atmosphere and it's electromagnetic influence the probe is still affected by the sun's gravity which stretches out at least as far as the Oort cloud.

It is a contender for man's greatest achievement, to date, the process which led to Voyager 1 started with the harnessing of fire, works through the Bronze and Iron age

The major obstacle to going on for longer is the Radio Thermal Generators, that power current probes. The current generation use Plutonium Oxide, with a change of source it may be possible to increase the life span from 25 years to a couple of hundred or more, that isn't going to get a probe to the stars or even to the Oort cloud. The features of interstellar space are vast in may be the other than the frozen rocks no meaning full science will left to be done to the atmosphere of another star is reached.

A vehicle that is going to make a sensible dent on deep space investigation is going to either have to live a long time or go very very fast. The current fastest object sent out from the sun is New Horizons which is on its way to Pluto and beyond, after its last engine burn it was at 58,536 km/h (36,373 mph) the nearest star is 39,900,000,000,000 KM away. That is 681631816 hours or 77761 years. So something launched in 77549 BC would be getting there about now. At that time Moden Humans had been around about 13,000 years and had migrated as far as Indian perhaps a bit further but not Europe or the Americas. This is the time of the Toba event, which nearly wiped out humanity. It was a very very very long time ago to travel a cosmologically insignificant distance.

To get the journey down to something a probe could do in 1000 years we means to go 70 times quicker. That is 4097520 km/h and assuming you can reach that speed very quickly but at 1g acceleration it would take, 116142 seconds or 1.34 days. Doesn't seem to bad till you realize that requires an enormous amount of energy and by any known method of propulsion an awful lot of reaction mass to throw away.

That is still 1000 years which isn't a practicable time scale, but if we cannot do better, then it maybe what we have to try. Though if we can accelerate for over a day at 1g, it likely we could keep on accelerating for the entire journey. We would quite quickly get into the speed region where relativistic affects begin to have a serious effect. The most obvious effect would be the that the probe would never reach the speed of light, the other that the subject time for the probe would be reduced meaning that what looked like a 5 year journey looking from Earth would appear to be a much shorter journey for the crew.

The closest star is Proxima Centauri at 4.24 Light years and assuming the probe was going to stop there rather than fly through the journey would take about 7 years viewed from earth whilst the probe would only experience just over 3.6 years. That based on numbers I got from The Relativistic Rocket which shows the calculation, which are considerably simpler than you might imagine.

However, as the site notes, to use a rocket to provide such an acceleration is in practice impossible. There are however several possibilities which do not involve any fanciful Physics. I'm not saying they are possible but nothing in current physics rules them out.

There are lots of different techniques which have been seriously looking at by NASA in its Breakthrough Propulsion Physics Program
Most of these explore some fairly radical physics ideas, which cannot be actively ruled out at the moment.  Some of them allow the speed of light to be bypassed as is done in Star Trek with a Warp drive, others just allow for constant acceleration in one case using a chunk of matter with negative mass.

For the more conservative system the speed of light is going to be the limit but we have already run robotic missions far longer then is needed to get to the nearest star if 1g can be achieved. Even within a single human lifetime it should be possible due to the time dilation effect to dispatch colony ships. Were some of the original crew will still be alive on arrival, even if their peers who stayed at home will not.

Failing all these it's going to be a very slow slog out to the start using generation ships, which is going to be very big, IMHO an asteroid of any size would be the base on which the ship was built. The nightmare for such colonists is to set off on a long journey only to arrive and find that a new technology was invented after they left, which allowed a faster journey and their target already has a colony, though it might be possible to call at the first ship on the way break the bad news to them and shuttle them to the target or improve their drive. May save a lot of time if they have already gone a significant way with significant resources. Though why tell them why not just be the first space pirates?

The one thing that we can be sue will not work is cryogenics, it will never be cold enough to stop the gradual breakdown of chemicals after a prolonged time the stored system will break down. The next possible would be to take copies of our genome and grow new bodies at the far end then implant them with stored copies of our minds, that would take only two new technologies. We could simplify it by producing babies and letting humanoid robots raise them this would mean storing all the data digitally where it can be copied and rewritten to stop it decaying and while it is currently not possible to build a custom genome and an egg from the component chemicals or grow that egg to a kind of birth, it is a technology we are starting to work towards for other purposes. Such as preserving endangered species. When can even take a very large chunk of Earth's biota with us.

We are still going to need a power supply to keep that digital data in tact but here the random Quantum noise that would play havoc with stored biology may come to our aid with the Casimir Effect which can produce energy from the quantum vacuum and may be one source of propulsion.

If we have to do it this way, which is the best candidate at the moment, it is going to take a very long time to get to the nearest start and the distance across our galaxy is 25,000 times as great so that is a long time multiplies by a big number, in other words a long long long time. That is just across our galaxy our nearest neighbour is about 25  times further than that and we are still only next door. Some of the lower estimates for the number of galaxies in our universe is 125,000,000,000 even Star Trek never planned on getting to the next galaxy.

It is a big big universe and the reason nobody has come to say "hello", does not that there aren't millions of intelligent species in this galaxy alone, the chances is are they are a long way away

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