Geoff and I discuss space travel

Re: [Neo-Swashbucklers CC2] Pilgrims

Tampico Jack wrote: There are some key concepts here. First, I think it will be relatively easy to get to near light speed.

Geoff: Well, that's the easiest part, but there are relativistic complications.

Tampico: Almost any source of thrust will work since thrust in space is cumulative.

Geoff: Not thrust, which is a force being utilised to change a velocity, but*velocity* is cumulative. ie the speed that you build up remains evenwhen thrust ceases according to the First Law of Motion. This is true for any speed we have been able to obtain thus far, however when you get to speeds that are up around C you run into some obstacles. According to General Relativity, mass increases as in proportion to speed and theoretically, at C, becomes infinite. So acceleration due to thrust will drop as speed approaches C as the thrust is trying to Delta V a mass that is increasing constantly at high percentages of C. There is also friction to consider. At speeds we have been able to reach,friction from interstellar hydrogen is insignificant, however as we get faster, the number of impacts per unit time will increase and will ultimately have a retarding effect (ie Drag) on the passage of the vessel through space.This also brings up the problem of meteoric and cometary material. To reach the stars requires passage through the Oort Cloud, which is believed to have a relatively high particle density and there are certainly a lot of stray objects. Now as the Hitchhikers Guide to the Galaxy says, space is really, really, really, big, however at any speed approaching that of light, it wouldn't take an impact from an object much bigger than a dust mote to cause serious damage to a physical structure - punch a hole straight through it or simply destroy it utterly. Radar won't let you 'see' that far ahead, since you are travelling at close to light speed and relativity also says that can't travel faster, your radar range will progressively reduce as you approach C. Time contraction is the only favourable outcome of travelling at high percentages of C and is one of the factors of relativity that has actually been demonstrated, which suggests that therest of it is at least somewhat likely to be correct...So that's the EASY part, but having your ship SURVIVE travel at that speed for more than seconds is a much more significant problem.One solution that has been offered is to fabricate a large mass of something solid, (perhaps ice) and mount it on the front of the ship as a sort of armoured shield, to absorb impacts while shielding the actual ship from them. Whether there would be enough heat from friction with interstellar hydrogen to melt it has not been established.

Tampico: Second, getting to the brink of light speed will be worthless if there is ever a way for tyrants to travel faster than light speed. There needs to be a maximum speed and that maximum speed must be attained inexpensively so that the main cost of the travel is the time spent.

Geoff: There is presently no even theoretical way to exceed C. Short of a breakthrough into some new realm of physics, this is unlikely to change.

Tampico: If there is a habitable planet 8 light years away, and I can travel there in 9 years, I would sign up tomorrow and go.

Geoff: If there is a planet 8 light years away, it will take rather more than 9 years to reach it. Remember that even if you can accelerate to C orsome significant percentage, it will take some time to accelerate to itwith a small thrust source (assuming the mass problem I mentioned is notan issue) then you will also need to DEaccelerate so I would suggest itwould take rather longer than 9 years, perhaps as much as 20-25.

Tamico: Someone wanting to tax me or force me into their empire would also have to travel 9+ years and then they would have to defeat me and return back on another 9+ year trip. What tyrant would do that?

Goeff: Concur. I believe I made that point in my earlier response.Wars are conducted to gain something for the warmaker. If there is nothing to gain, and I believe the cost of transport over interstellar distances of war materiel and warships etc would be, literally,astronomical and such a war would doubtless cost more to wage than any possible tangible gain that might eventuate. It's been hypothesised that trying to do so would likely bankrupt said Empire and lead to its collapse.

Tampico: Besides, I would leave a note when I left saying that if I am followed that I would destroy all improved property before the arrival of my pursuer. Interstellar travel will be the end of tyranny if there is a maximum speed of travel.

Geoff: Very likely INTERSTELLAR tyranny, however there is nothing to stop some new self styled Hitler or Bonaparte from starting up on the new world.We take all our human failings with us when we go anywhere.

Tampico: I am also pretty confident that we will find habitable planets in various sized solar systems. If the star is larger than our sun, then perhaps the planet will be proportionally more distant from the star.

Geoff: There is as yet no mechanism to detect Earth like planets even around nearby stars (ie under 10LY) though it is possible to detect PLANETSaround other stars (this has been done) the only ones that have been reliably proven to exist are Jupiter type gas giants - clearly not habitable. Whether other more earthlike worlds also exist in company with them has not been demonstrated - though one could postulate that the existence of one may suggest it to be possible at worst. I concur that there are very likely to be earthlike planets 'out there' but it will be difficult to find one without actually going there to look. This will doubtless require space probes that are sufficiently long lived to reach a star system and send back real data - a mission that could easily last 50 years or more even to nearby stars. Such an undertaking would be a true 'generational' mission, with the people who began it passing the responsibility for its completion to their successors. One wonders if NASA's proposed moonbase would include an astronomical telescope of significant aperture - ie bigger than the Hubble. If it did, it *might* be possible to discover if extra-solar, earth sizedplanets exist. The problem of micro-meteorites will be solved someway possibly by being dissolved by some sort of force shield around the craft.That would be the ideal, however there is not presently any known method of producing such a phenomena - it would clearly require a breakthrough in both theoretical physics and engineering - I suspect that even if itis eventually possible, the power requirements would be staggering.

Tampico: Tyranny will suffer a blow in a less direct way also. If you look at the improvements made on the US East Coast in employment from 1800-1900 it gives a good indication of what could occur. Employers in Boston, for example, did not just become more kind hearted during that period. I think that they knew that they had to pay a livable wage and had to improve working conditions or they would risk losing employees to the frontier. The same will happen when mankind starts pioneering new planets. Even tyrants will have to soften their tyranny for those who remain or risk losing them to the frontiers in space.

Geoff: Possibly. Or you will get what Heinlein, McCaffrey et al postulated -the adventurous will migrate to new frontiers and the 'sheeple' will remain in their safe little cubby holes. Overcrowding might well bemore of an incentive to migrate than oppression (and one is frequently aproduct of the other).I don't know if you read SF at all, but 'Decision at Doona' by Anne McCaffrey postulates just such a situation. An overcrowded world that is 'dormitised' into a complete urban complex, with complex rules of behaviour and etiquette and 'Proctors' watching for any 'social crimes'being committed and punishment consisting mostly of reductions in rations.