Interstellar Travel - Possibilities and Human Physiology

I am interested in the potential for Human Interstellar Travel. Questions that need answers are (but not limited to):1. Is interstellar travel even possible?
2. How quickly could we get to a near star?
3. What technologies would be either theoretically possible or other (lunatic fringe)?
4. Presuming we go, what life forms would it be required to tag along?
5. What physiological/genetic changes should we consider for H. sapiens space travel?My current thinking is that we go to the nearest star and build a space station there, if there is no planet/moon that could be colonized, and then use that as a jumping off point for further hopping. If we could go at 0.5c it would take about 10 years. Colonizing Mars could act as a technological and physiological experiment station.BTW, I am not a big SciFi fan, but I do think we will eventually colonize the galaxy, without FTL travel.This is just a first draft of such a thread and there will be a lot of biology involved and technical pieces.

Thread moved here from the Proposed New Topics forum.

Does anyone know about Solar Sails?Simple question (which is beyond my biological mind).If you accelerate a body to 0.5c in space and turn off the engines, how long would it take for the "friction" of space to slow it down? Or why does space travel require continuous burn of engines (which I have read elsewhere)?Biological questions.How do we keep muscle tone up for extended periods of time? Anyone have any ideas on birth in space and the effect on infants? Is artificial gravity a reality or just Sci Fi?

The space probes we have headed out burned for a very short while and have coasted ever since. I am unfamiliar with the "friction of space" concept that would slow them down over time.Travel with continuous (low level) acceleration is better if you can do it. The burn at the beginning and end is what we are stuck with until we get better engines, but they're working on it.Sails are good because they provide continuous acceleration without having to carry fuel or engines, but their effectiveness decreases with distance from the sun. They are experimenting with that too.

This one interested me the most.First on the list are the life forms that we already take with us everywhere, our normal human flora (e.g. skin flora, gut flora). As for supplementary life forms, a minimum requirement would be seeds for high protein plants such as soy beans that can be planted once you reach the destination or grown hydroponically. For in flight, genetically engineered algae and yeast could serve as a nutrient rich food source. Unicellular life forms are the most effecient and the least picky. I see no reason why we would need large plants or animals in flight to supply food. One could certainly argue that there are psychological reasons that we need plants and animals with us.

There are small amounts of interstellar hydrogen, not to mention micrometeors in the Oort clouds and other small dust particles. This would produce drag, but I don't know if it would be significant at relativistic velocities.

In the absence of gravity, lots of exercise where force is applied to the person. Modern astronauts strap themselves down to treadmills and bicycles. The bones need to experience a force load in order to keep bone density.This can also be solved by accelerating at >0.5 g or having a cylindrical ship that spins to produce centrifugal force. I don't think there would be any problems pre-natal, but I have no idea on post-natal health. The only "artificial" gravity we can produce is centrifugal force. Just think about those carnival rides where the ring of cages spins around and pins you to the back of your little cage.

I don't know about 'drag' from them but they do become significant at near c speeds. They become high energy cosmic rays and micrometeors become massive bullets.

What would be a reasonably safe speed?Could a nuclear power plant be feasible?

Depends on the shielding. You would need a thick physical barrier to shield you from micrometeors. You would also need shielding from radiation. As Ned points out, at relativistic speeds the amount of deadly radiation increases. I don't know if magnetic shield would suffice for all sources of radiation. You might need more cadmium control rods if a fission reactor is exposed to external neutron sources, but other than that I don't see why you couldn't use one.

Interesting questions Sarawak,Here is my take on them: I will answer these three in my explanation below:I assume you are asking if interstellar travel will ever be possible for the human race. If that is the case I would have to say a resounding yes, based on past human progress and technological innovation.The real question is not if but how. There are several ways we can approach this problem. One is that if we use current technology the only way to get to the stars is by using a generational ark due to the long duration of the trek.The fastest interstellar spacecraft in our current arsenal is Voyager 1 which is travelling at 38,600 miles per hour away from the solar system. This is a mere 0.0058% of the speed of light and would require approximately 639,643,679 years to get to even the nearest star of Proxima Centauri at 4.2 light years (24,690,246,000,000 miles) away. Even using a generational ark it is unlikely that a human society living in such close confinement and under such extreme psychological and physical stress as this would survive. Additionally, this independent human society would be more limited in its resources than that of human society on Earth and in the hundreds of thousands of years it would take to travel to this nearest star; it is more likely this slow-moving ark would be surpassed by possibly speed-of-light vehicles created by the much more accelerated and advanced Earth-based civilization. So I chalk this scenario up to being highly unlikely until we can increase the speed of a spacecraft significantly. The only hypothetical vessel that I could see doing this is one which uses interstellar matter/energy (and possibly a supply of matter/antimatter) to supply a continuous "burn" or acceleration throughout its trip. Problem is that it would also require a deceleration to keep it from overshooting its destination. Also, the more massive the vessel (and this space ark would have to be massive to provide a self contained atmosphere/ecosystem for a whole human society) the more energy would be required to accelerate and decelerate it. Just food for thought.If we could increase the speed 100-1000 fold maybe through the use of slingshoting ourselves around the Sun/Jupiter several times in a row (though the g-forces alone would probably kill any large organisms including humans), this would reduce this effect but truly until we can get to near light speed travel i.e. 80-99% the speed of light, interstellar travel to even the nearest stars would be an excruciatingly slow process.I think the real answer to this paradox lies in bending spacetime itself rather than traveling "through" space. If we can bend spacetime itself and create wormholes to other portions of the galaxy and universe the enormous distances between them would evaporate. However, the energy (dark or otherwise) required for this venture would be enormous and much beyond our current technology much less our understanding. However, I think that the answers to the question of interstellar space flight might found through research into the infinitively small realm of quantum physics than just with the study of the macroscopic world of cosmology and astrophysics (though they are all intricately linked together as a whole). Again I believe it is not a question of if interstellar space flight is plausible but rather when will it occur in human evolution. The question depends on whether we are going to a world with or without preexisting life. If the latter, than we should bring with us the minimal necessary life to produce a stable and self-sustaining ecosystem i.e. plants, bacteria, animals, etc. If the former, than I would suggest bringing absolutely zero life (except ourselves) onto the planet, so as not to risk causing an ecological disaster to the world with this already pre-existing life. Even then, our very presence (and all the organisms i.e. bacteria, etc in and on our bodies) could jeopardize and possible exterminatethe pre-existing life on this planet. I would vote for going to a hospitable planet with no life on it to avoid this possible catastrophe to a preexisting ecosystem. The question is how can we achieve speeds of 0.5c? Either way I think a self-contained ecosystem on a space vessel would be required and until human life spans can be substantially extended that generational ark type vessels may be required until we can find a way to bend spacetime itself, thus eliminating this problem completely (though opening up other space and time paradox in its wake).Just my thoughts.Edited by DevilsAdvocate, : No reason given.Edited by DevilsAdvocate, : No reason given.

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For me, it is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring.
Dr. Carl Sagan

Two things more.1. Cannot a slingshot mechanism be used for deceleration?
2. A habitable planet, IMO, will almost definitely be occupied by some life forms. Without any data (nobody has any), I think all planets with appropriate physical conditions will be inhabited. If we are worried about native life forms, we might as well stay home, or stay in space. I think the universe in crawling with life.

It's actually simpler than that. In order for a planet to be habitable it must have oxygen. For a planet to have oxygen it must have life. Specifically, it must have photosynthesizers that are producing oxygen. Oxygen is a very reactive element and it disappears quickly if it is not constantly replaced. In fact, our planet has massive iron sediments which marked the emergence of oxygen producers on our planet. The sediments themselves illustrate that lifeless planets will probably have massive oxygen sinks that will have to be filled before oxygen levels can increase in the atmosphere. Short term terraforming will probably be very difficult and energy intensive.

I'm guessing that you mean habitable by us because otherwise your statement is wrong. There is life now (inhabitants) on earth that doesn't need oxygen at all (the opposite in fact). It maybe that to have life more complex than single celled you need oxygen but that is not for sure either.

Since we are the travellers of interest, I thought this was assumed.