[bossa]

The "Oh my god particle" was a proton that packed the wallop of a brick falling on your toe. Imagine a giant spacecraft where every atomic particle packed that same energy. If you hit one spec of dust the entire machine would vaporize.

I suspect that the easiest form of interstellar travel could be a modular device made from miniature robotic probes propelled by solar sails. These devices could assemble themselves into a much larger machine at the destination.


https://www.fourmilab.ch/documents/OhMyGodParticle/

[WPRESTO]

The "Oh my god particle" was a proton that packed the wallop of a brick falling on your toe. Imagine a giant spacecraft where every atomic particle packed that same energy. If you hit one spec of dust the entire machine would vaporize.

I suspect that the easiest form of interstellar travel could be a modular device made from miniature robotic probes propelled by solar sails. These devices could assemble themselves into a much larger machine at the destination.


https://www.fourmilab.ch/documents/OhMyGodParticle/

The problem with Solar sails is the exponential decline in solar light as you move out, By the time you get as far as Pluto, it is so weak it's essentially useless.

[Auzzie-Phoenix]

I'd think that the ion drive they used on a pre-existing craft would work better than the sails. Don't remember which thing they sent up into space uses it, but it was pretty big news at the time.

[bossa]

The problem with Solar sails is the exponential decline in solar light as you move out, By the time you get as far as Pluto, it is so weak it's essentially useless.

Agreed. Setting Masers or Lasers up along the way to give the sail a boost might help but it certainly wouldn't allow people to go where no one has gone before.

---------- Post added 13-08-15 at 01:06 PM ----------

There is that new EM drive that is being developed. That may well turn out to work.

But I suspect that it will be impossible to traverse the Oort Cloud without collisions.

[MD Optofonik]

Until a means of transporting at extreme speeds and the ability to withstand collisions with even tiny space items are developed, speculation of interstellar space isn't really of much use. Yes, it's fun to speculate but don't get wrapped up too serious in something we'll never see in our lifetime.

We'll not see it in our current state of genus much less our lifetime, methinks. The amount of time needed for interstellar travel would be so vast it would span evolutionary changes to our fundamental taxonomy. After the number of eons in space required to reach another solar system homo sapien would no longer be part of the passenger manifest of whatever craft (another topic entirely as Tom touched upon) we departed in; our very genetic memory would cease to exist in its current form. It would take 165,000 years to reach Alpha Centauri. Living all that time in the alien environment of a space craft would require rapid evolutionary change for long term survival in interstellar space.

It would take about 30,000 years just to get to the other side if the Oort Cloud, the "on ramp" for the the journey to other solar systems. Travel to other solar systems is never going to happen, we are an earthbound species and need to wake up to that fact so we can start figuring out how to keep our home intact.

[cmar]

The problem with Solar sails is the exponential decline in solar light as you move out, By the time you get as far as Pluto, it is so weak it's essentially useless.

That's true, but I wonder how much acceleration you could build up by then, after all you're not going to loose that momentum in space. The problem of course is slowing down at the other end, or making mid trip course corrections. Coming back is a problem but I assumed that a colonisation trip was always going to be one way.

Living all that time in the alien environment of a space craft would require rapid evolutionary change for long term survival in interstellar space.

I read a scifi story once about this, the problem was that long after they left, mankind discovered the warp drive, and aftere a time, the lost sub light ship could not be found. So when they finally reached the next star system people were already living there and had for thousands of years. Very sad.

[WPRESTO]

Once the ship is "gliding," too far from any star to collect sufficient light with collectors, they'll still need a continuing way to generate enough power to keep themselves alive - heat and light, and enough light to illuminate a space large enough to grow food,probably hundreds of hectares. They'll also need power to run recycling machines for waste, oxygen and water generation or purification. Many sci-fi movies have the dead bodies of humans ejected into space, but on a journey lasting 10,000 years or more that would waste too much organic material, so there should be machinery to convert dead humans into plant nutrients. Presumably the power source would be some sort of nuclear generator tethered but safely away from the main craft, a fusion reactor of course, as that would provide energy enough for a journey of tens to hundreds of thousands of years. What is the lifespan of the best nuclear power plant built so far on Earth? How much water does it take to operate such a plant? What would be involved in launching such a facility into space?

Note above a question raised about the problem of crossing the Oort cloud without hitting something. This raises an issue I mentioned far back in this discussion: getting people to grasp scale (in my case by students). Consider the asteroid belt between Mars and Jupiter: How dangerous is it for a satellite to pass through? What is the probability of hitting something? The asteroid belt has a volume estimated at 16 trillion-trillion cubic miles. So if there were a trillion asteroids large enough to damage a satellite, each would occupy a volume of about 16 trillion miles. The average space between them would greatly exceed the distance between the Earth and Moon*. No problem there, and no worry about striking something while passing through the Oort Cloud which is vastly (VASTLY!!!!!) larger than the asteroid belt. However, space is not empty. There are a variety of molecule-atom realm particles out there, generally at unimaginably minute density, but there are great clouds of "gas" with significantly higher densities. The densities are still tiny by Earth standards, but the clouds are huge, light years across, so going through one might cause wear-and-tear on the outside of a ship.

*How often are there collisions between asteroids within the asteroid belt? I found a calculation for objects one kilometer in diameter or larger. Estimated frequency with which a particular asteroid one km hits another: once in about 3 billion years. Because there may be over 100,000 asteroids that size, collisions overall take place about once every 10,000 years. So the chance of a spaceship being hit while passing through the asteroid belt is much lower than your chance of being struck by lightning (which is incredibly greater than your chance of being killed by a bear while visiting Yellowstone Park).

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Last edited by WPRESTO; 08-13-2015 at 05:42 AM.

[RoxnDox]

I think every single area in this thread has been covered in one way or another, by authors and scientists and engineers and dreamers... Many of them glossed over the hard parts with a lot of hand-waving and use of Unobtainium and such, but a lot of them took reasonable extrapolations of available technologies and went from there. One set of books I read recently did a very good job - construction of an Ark ship that took over a century to build, politics on and off Earth, building the tech base to construct the space industry to construct the vessel itself, more politics, life and politics and evolving societies within the vessel on a 10,000 year journey towards an earth-like planet (at 0.01%c), and even the physical evolution of the inhabitants (island dwarfism sort of). Very well done IMO.

(first book: http://www.amazon.com/Genesis-Ark-Paul-Chafe/dp/141659163X

Laser-pumped solar sails are also a frequent 'design'. Yes, decelerating is a problem, but there's even ways around that. See Robert L. Forward's Rocheworld series (wikipedia link describing his sail: https://en.wikipedia.org/wiki/Rocheworld#Forward.27s_light_sail_propulsion_system.

Yes, all are beyond today's technology, but many things can be extrapolated to a century or two ahead. It may not be possible, or maybe we will try and fail, but maybe we will succeed - if we try.

Jim

[Rupert]

I'd be satisfied with just getting through Friday traffic tangles in my little town of 55K people. When they figure that out, then they can work on some distant planet.

Regards!

[LeDave]

Got my new K-3 w/ grip a week ago, this week my 100 Macro WR came in.

[WPRESTO]

Glad to see a few Pentaxians are down to Earth.

[MD Optofonik]

I read a scifi story once about this, the problem was that long after they left, mankind discovered the warp drive, and aftere a time, the lost sub light ship could not be found. So when they finally reached the next star system people were already living there and had for thousands of years. Very sad.

Do you remember the title?

[Rondec]

Most science fiction stories gloss over the real difficulties with as yet undiscovered technologies that will make space travel easier. Hyper drives, warp drives -- all sorts of ways of getting somewhere else quicker. Ships capable of terraforming other planets to make them capable of sustaining human life (how hard would that really be).

Most that I have read use some type of cryogenic sleep with the space ships run by robots in the meantime. Maybe that would work, although what happens if after a hundred years the computers all crash and no one wakes up?

I wouldn't say there won't come a time when some of these things are solved, but the idea that the future will just be magic and everything will be solved is foolish. For all the technological distance we have come in the last fifty years, it still wouldn't be easy for us to go to the moon and back, much less the distances we are talking about with interstellar travel.

[WPRESTO]

Another down-to-Earth Pentaxian, HOORAY! Before we think about multi-generational interstellar travel, how about creating a permanent, self-sustaining Moon base? What would be involved in that relatively insignificant technology-engineering - required mass to lift off project?
BTW : I found an interesting article, by a celebrity physicist, speculating on energy requirements for various types of rocket propulsion. For warp drive, where you have machinery that can distort time-space ("warp" it) and therefore travel faster than the speed of light, the energy required, he suspects, will be equivalent to what is generated by an entire galaxy of stars. Of course there are problems: can you unwarp time-space after the ship gets where it wants to go, and can anything ship, or anything biological, survive in warped space-time? This is also a problem with "wormholes," a recent favorite of sci-fi (Deep-Dish 9 comes to mind). Supposedly these things connect two black holes and can transport you from one point in the universe to another vastly faster than the speed of light. Aside from the fact that such structures are in the realm of "could such a thing exist," there's the problem of whether any ship, or anything biological, or anything at all such as an asteroid, could enter a black hole and survive intact, much less get back out. I think it might be easier to land a manned space ship on the surface of the Sun and return unscathed than to enter a black hole then exit unchanged.

[Rupert]

This thread is deteriorating rapidly.....I think it's about time to...

Bring in the squirrels!


Regards!