Is star travel practical in theory now?

[EinsteinPD]

     Hi all. Star travel is generally considered to be impractical, due to the large distances involved. However when I looked into the distance problem, I saw it was not really the distance, but the time required to cover the distance, that is important. And, I saw that the time required could in theory be made as small as desired, by employing Dr. Albert Einstein's experimentally proven Time Contraction principle. In theory, as the starship approaches light speed, time slows down for it. The energy for the constant acceleration required could in theory be supplied by a submarine propulsion type two stage nuclear reactor. The reactor heat energy would convert water into ultrahigh pressure steam, and the starship would be propelled by steam jets.

     I wrote and published an ebook titled Starship To New Earth NOW on this subject. The book and I were vigorously attacked on numerous grounds, none of them technical. it seems the idea that star travel might be practical, and that a person with a science Ph.D. might dare write on it here, is very disturbing to some people. My purpose is not to disturb, but to shine some light on the subject, which I consider quite important. Once star travel is achieved, then so is colonization of other Earth type worlds.

      The book discusses why star travel is generally considered so impractical now, that it is not even being attempted. The mind set situation now is similar to that which delayed  Christopher Columbus before 1492. It was the enormously large reward to risk ratio that made the King and Queen of Spain decide to finance Columbus's voyage, that discovered the new world. It is the inconceivable value of an entire new Earth type world, that will belong to whoever goes there and claims it, that I expect will lead to eventual funding of a starship.

     The actual starship may very well be quite different from the one that my book describes; that does not bother me a bit. My book is a pioneering attempt in the direction of practical star travel, and its purpose is to attempt the opening up of the subject for discussion. If you are at all interested in star travel and colonizing Earth type worlds, then you should take a look at this book. If you don't think it worth $3.99, then just return it within the free return period.

     Thank you for your interest in reading this post, it is appreciated.

     Phillip Duke Ph.D.

Space Shuttle Atlantis. Not a starship, but a big step in that direction.

[kamas716]

Seems like you'd a need a heck of a lot of water to convert. Since IIRC, as you start approaching the speed of light mass increases, which then requires even more energy to cause accelleration.  Then, when you get to your destination you would need to decelerate.  Do we have the technology to build something that could survive the stresses?  You would need to bring equipment to build a sustainable environment, or at least the mining/manufacturing equipment to build it once you got there.  Any problems that come up during the flight or once arrived would need to be taken care of within the ship, there would be zero help available.

So, yeah, with current technology, I'd say it's impractical.

[ManuelGarcia]

To use nuclear fission to accelerate to a speed that would allow the trip to the nearest star in a human lifetime would require a mass-ratios of between 1,000 and 1,000,000. Assuming the 1,000 could be achived that means you would need 1,000 pounds of propellant per pound of pay load. The Apollo space capsule weighted about 37,000 pounds so it would take 37,000,000 pounds of water propellant. To get up to a small fraction of the speed of light, and there wouldn't be any to decelerate it. To both accelerate it and decelerate it, you would need 37,000,000,000 pounds to accerate both the space capsule and the water for deceleration. But this is an empty space capsule, which does not have enough room for passengers and the food they need for a decades long space trip.

So no we don't currently have the technology to send people to the stars within a human lifetime.  We don't even have the technology to send a robot that doesn't need food and water to the stars within the lifetime of the people sending it.

[EinsteinPD]

     Thank you kamas 716 for your post. As the speed of light is approached, the water fuel mass also increases, the same as the starship's, so the mass increase affects cancel. Information on nuclear sub propulsion system boiler steam pressure is classified, and without this the amount of water required cannot be reliably estimated. The starship leaves from the space station, and could tow an iceberg behind if for fuel if necessary.

     The acceleration is limited by the crew's ability to withstand it. A constant acceleration of one or two g's achieves close to light speed in just a few months, A little transit travel time until half way there, and then the ship rotates 180 degrees, and decelerates at one or two g's until the destination is reached.

    You are quite right about the necessity of a sustainable environment. On the ship its life support system ptovides that, in theory New Earrh will provide a reasonably suitable, sustainable environment, or it will not be colonized.

     Yes, the travelers will be on their own, but the onboard computer plus the crew's extensive training and supplies, will hopefully allow them to overcome any problems that may come up.

     Star travel is not necessarily colonization, and in theory colonization is considerably more difficult than star travel. But its rewards are also much greater.

     If you would like more details, please see the book, or Post. Thank you again for your reply. Your interest is appreciated..

[EinsteinPD]

Manuel Garcia thank you for your Post. I do not know how you arrive at the fuel/payload mass ratio of 1,000. With nuclear energy in general the situation is of course much more favorable than with chemical energy. Without presently classified data. the amount of water fuel required, and therefore the fuel/payload mass ratio, cannot be reliably estimated. I prefer not to make a "guesstimate."

The starship leaves from the space station at a constant one or two g acceleration, and if necessary it could tow an "iceberg" for fuel (the ice fuel could be stored outside the starship).

The entire trip would take considerably less than a year for the occupants, due to time contraction. I give a Table with numbers re time contraction, and there are references, please see the book.

Time contraction works for the starship and its occupants, but NOT for those left behind. For those left behind the aging situation is as you state, except for the few closer stars, like the Alpha Centauri binary, only 4.3 light years away. Other than for the closer stars, the starship's designers and financiers will die of old age before the starship arrives.

Thank you for your Post. Your interest is appreciated.

[ManuelGarcia]

For fission reactors classified or not the maximum energy output is approximately 0.1% of the total mass-energy of the reactor fuel, this limits the effective exhaust velocity to about 5% of the velocity of light.  That can be used to calculate the mass ratio to get to 10% of the speed of light as about 1,000. The 0.1% is the theoretical maximum and so the 1,000 would be the smallest ratio. In real world applications it would be higher. The advantage of towing ice is that at least you don't have to accelerate the tanks. But that is still a lot of mass to accelerate. The time dilation factor at 0.1 c would only be 0.995. So ignoring the time in acceleration and deceleration that is 40 years to Alpha Centauri by earth clocks and 39 and half on the spaceship clocks. To go faster would increase the amount of propellant needed. This is why so many sci-fi stories which don't have FTL use Bussard ramjets as they don't have to carry their own fuel. But they do depend on having the technology to cause fusion just by magnetic fields in space, whereas now we can't even do a break even fusion in a lab.

[EinsteinPD]

Manuel Garcia thank you for your Posts. Please explain how you arrive at the statements in your last Post's first two sentences. Thank you.

I point out that there is no reason why the uranium reactor fuel cannot in theory be replaced in space with new fuel, as often as may be necessary.

Your time to Alpha Centauri is I believe much too large. If you very conservatively figure several months to accelerate close to light speed, at say 2g's, a little transit time, and then deceleration at 2 g's.the trip there from Earth would take a maximim of only about one year. However, if as you state only 0.1 light speed is obtained, then your 40 years is OK.

It is always possible that limitations related to propulsion, or other considerations, may make the starship I describe impractical. I wrote the book to create interest in practical spaceflight now. The specific method is not written in stone. Jules Verne and H.G. Wells both shot their space travelers out of a cannon. It may be that hydrogen fusion energy is required? Or some other method may be discovered, such as UFOs evidently employ?

In any case, as long as star travel is considered impossible period, there will be zero consideration regarding it. That is the present situation.

Due to your interest in the subject, which is very much appreciated, why don't you look at the book? In addition to propulsion, I discuss life support, crew selection, new Earth colonization, life on other worlds, etc. You can always return the book for free.

Thank you for your interest, and your Posts. They are very much appreciated.

[ManuelGarcia]

The 0.1 percent conversion of U235 is well known. It can be calculated from the fact that one atom of U235 when split releases 215 Mev.  I remembered it from school but 
http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/u235chn.html#c3 shows and several web pages show the 0.1% 

http://chemwiki.ucdavis.edu/Physical_Chemistry/Nuclear_Chemistry/Fission_and_Fusion
http://discovermagazine.com/2010/jul-aug/24-numbers-nuclear-weapons-bomb-stockpile-peace
http://en.wikipedia.org/wiki/Nuclear_fission

My calculations ignore the the reactor's and fuel masses. It assumes that the 3,700 is all that has to be sent to the stars.  Current technology was that 3,700 could carry 3 people and enough supplies for about 3 weeks. There is no way to refuel after leaving.

Now even at 0.1c the ship would need shielding from the particles in space which are travelling relative to ship at 0.1c. Shielding requirements go up as the speed goes up, increasing the weight, thereby increasing the fuel/propellant required making it more expensive to go faster. Some other people who understand fuel mass ratios have proposed a multistage system so that when one reactor has used up all its fuel it could be ejected and the next stage used. But even then it would be tough to get to 0.1c.

Now with advances in techology hopeful some humans will get the stars, if we ever get techology can easily make antimatter so that we get 100% conversion instead 0.1% for fission and 0.7% for fusion then it might be possible. 

So I am sticking with answer that at our current level of technology we can't send anything to stars within a human's lifetime.

I think I am finished here.

[EinsteinPD]

Manuel Garcia, thank you for your posts and your recent reply, they are appreciated.

I have no problem with your conversion figure for U-235.

The starship would probably "weigh" more than 3700 pounds. Re supplies, in my book oxygen and food are supplied by ongoing soybean photosynthesis, in an ecosystem closed except for energy input.

Re particle shielding, being able to see a star clearly suggests the space between is particle free. And, as the starship's mass increases, particle impact affect on it decreases.

Since Uranium reactor fuel when spent is changed here on Earth, I expect it could be done in space also, with a reactor designed to make it possible there.

This all reminds me of the situation where when the Wright brothers were finally ready to put an engine on their glider, all those available were too heavy, because previously weight was never a very imporant  consideration. They designed a lighter engine, and they flew. Reactor weight has not previously been an important consideration. The starship hull is based on lighter Duraluminum, not steel. Booster chemical rockets, something like those the Space Shuttle uses, would increase speed. Reactor refueling in space, why not? Etc.

It could be you are right, but I do not think so, because the history of science shows otherwise. At this time you and everyone else I have been in contact with, are firmly convinced star travel is not possible now, because that is what they were taught, and that is the general belief. These two things do NOT make it impossible, but as long as everyone believes it's not possible, it will not be accomplished, because no one will try to accomplish it.

The present situation is that of a self- fulfilling negative prophecy. I discuss this in the book.

The starship should be built, as a prototype. Even if it cannot approach light speed, modifications may well make it possible. Look at all the failed attempts to break the sound barrier. And, the starship  should do a very good job of just zipping around the solar system. A very good job.

Thank you for your interest, it is appreciated.

Phillip Duke Ph.D.

[kamas716]

I discuss this in the book.

I can't help but get the feeling that this is just an attempt to get people to purchase your eBook, since you keep repeating that line over and over again.

[EinsteinPD]

In reply to kamas716's 29 word Post: I wrote the book to be read, and I want more readers. Whether it's purchased and kept or returned, is of no importance, as long as it is read. I gift copies as helpful. The most recent person I gifted the book to was Professor Barry Schweig (email address on request), who gave the book an Amazon.com honest 5 star review.

You can read both the review and the book free. Just be sure to return the book within the free period. Or, if you miss out on doing that, just email me, and I will gladly refund your money. I do not want you to feel you are being taken advantage of financially.

The book is detailed compared with my posts. I cannot write each entire chapter here, I do not have the time. For more complete information read the book. And then, if you "feel" the $3.99 is too much for you to spend on it, simply return it. Very easy to do electronically. No problemo.

"Trying to get people to purchase your book" by posting here would be very dumb, because so inefficient. All the people who have replied to my posts on the Starship are obviously so prejudiced against the idea that star travel might be possible, that I am simply wasting my time replying to grasping at technical straws objections. They will never read/buy this book because it goes against deeply held belief/feelings. They have a lot of company.

And, in case you think the book's subject is not important, FYI atomic WW 3 IS COMING, and with it the annihilation of the human race. Read "On The Beach" by Neville Shute, or see the movie. Do you have any idea what cobalt encased hydrogen bombs can do? The starship is humanity's only chance of survival. That is why I wrote the book.

Very truly yours,

Phillip Duke Ph.D.

[ManuelGarcia]

If anyone was to read about a project that covers the real problems of interstellar spacecraft check out Project Icarus http://www.icarusinterstellar.org/projects/project-icarus/ it dedicated to achieving interstellar flight by 2100.  But even they say it can't be done with current technology for it to work it requires fusion based space propulsion. It is unmanned and while it comes up to 10-12% of light speed it has no way to decelerate. So it would study and send back data as it passes by a star system. 

I like this image

Of the Daedalus, the predecessor of Icarus, compared to a Saturn V rocket. Daedalus was designed between 1973 and 1978. Note it has two stages.

But this design which only gets up to about 0.1 c is beyond current technology.

[patgolfneb]

The key word is practical. It may be possible. For star travel to be practical there would have to be considerable space based infrastructure. At this time we have a miniscule space infrastructure. My guess is 2200 is more likely than 2100. By then I will have been dust for 150 years. So I will enjoy my fiction books and wish my great, great, great grandchildren well.

[EinsteinPD]

Manuel Garcia thanks for the Post with interesting image. It is possible that fusion based energy is necessary, but IMO fission energy is well worth trying. It seems to me deceleration can be achieved by simply rotating the starship 180 degrees.

As long as everyone believes/is certain that star travel is not preactical/achievable now, it will not be attempted. And not being attempted, it will not be achieved. The situation is of a self-fulfilling negative prophecy.

Thanks again for the Post.

[EinsteinPD]

Patgolfneb thanks for the Post. Just what do you mean by "space infrastructure?" If you mean an expanded space station and more space experience, I certainly agree. At this time funding for the U.S. space program is being reduced.

My Post's title is "...practical in theory now." Once it is believed something valuable is possible in theory, it will be attempted, and being repeatedly attempted, it may well be achieved.

Based on the large literature related to UFO visual and radar sightings, a non-reaction propulsion system is possible. This might be discovered at any time, which I expect would facilitate star travel now.

Thanks again for the post. Your interest is appreciated. For much more detailed information read "Starship To New Earth Now."

[ManuelGarcia]

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EinsteinPD wrote:

 It seems to me deceleration can be achieved by simply rotating the starship 180 degrees.

---

The problem isn't orientation but fuel,from the Icarus FAQ.
One solution is to decelerate, but that increases the fuel mass required for the mission geometrically. For example, Daedalus was to carry 50,000 tonnes of fuel for its unmanned flyby. If Daedalus were to decelerate in the target system, its initial mass would have needed to be about 2.5 million tonnes.

All fuel used for deceleration has to be accelerated to 0.1c. You need to read up a spacecraft physics, such as specfic impulse, fuel mass ratios, energy density and so on.

[EinsteinPD]

Manuel Garcia thank you for your post. I posted that deceleration can be achieved by simply rotating the spacecraft 180 degrees. I posted this after you posted that it was "not possible." It is possible in theory. Why not?

FYI I am well aware of the fact that deceleration requires as much energy as acceleration. Since colonization requires a planetary landing, deceleration is required for colonization. Deceleration is no more difficult than acceleration. Both require energy. I believe adequate energy is available via fission. You do not. So be it.

As to what I "need to read up on," the fact is you strongly believe interstellar space travel is impossible now, and my refusal to share your belief has resulted in this derogatory statement about what I "need to read up on." This statement only weakens your overall position.

You are welcome to believe whatever you want, and so am I. It's obvious to me I am only hitting my head against a solid wall of disbelief here, and when I see a Posted derogatory statement, then it is time for me to consider closing the thread. I am not the least bit interested in arguing.

Space Shuttle Atlantis. Not a Starship, but a big step in that direction.

You may or may not know that at one time calculation showed the bumblebee could not fly. At one time no one ever believed man would fly, walk on the moon, etc. Regarding Daedalus, the overall project is evidently defunct now, and I would not put too much confidence in it. The very name suggests failure, because Daedulus failed. What you "need to read up on" is the history of science, and see that many times while skeptics "showed" something could never be achieved, people of vision promoted it, and eventually it was achieved.

I have spent far too much time already on this thread, so unless you have something much more substantive than telling me what I "need to read up on," or again quoting re Daedulus, goodbye and thanks again for your Posts.

Phillip Duke Ph.D.

[kamas716]

I'll probably regret this

Both require energy. I believe adequate energy is available via fission. You do not. So be it.

It's been a couple of decades since high school physics, but IIRC, the problem isn't just the mass, but the ever increasing energy to accellerate it.  While the fuel coming out the back will increase in mass at the same rate as the increase in mass of the rest of the ship, giving a constant thrust, you still have to accellerate the fuel in order to get the thrust.  As the mass increases, it takes increasing amounts of energy to accellerate that mass.

[EinsteinPD]

kamas716 thanks for your Post. In theory the fuel mass increase hinders acceleration, but also helps it to the same degree, since the fuel mass to be ejected also increases to the same degree. And, as the mass increases, time contracts. Therefore I suggest as stated in an earlier Post, the Relativistic mass affects will cancel. I could of course be wrong about this.

These Relativistic affects are not so easy to understand, and so to predict. IMHO the situation is something like trying to predict what happens with attempts to break the sound barrier. Many experts said it was impossible, and a number of test pilots died trying, but by repeatedly modifying the aircraft it was achieved. That is why I say, build a simple starship prototype and test it.

The Posters here seem to believe the necessary energy is the main problem. I believe that by carrying a sizable anount of fissionable material, and ice fuel, the energy will be adequate. If not, I expect an improved energy source will be found.

My question is, why is it so important to you to believe it's not possible? I am quite willing to say it may not be possible, but that is very far from its being proven impossible.

Best regards,

PD

[Rick_BN]

"Star travel is generally considered to be impractical, due to the large distances involved. However when I looked into the distance problem, I saw it was not really the distance, but the time required to cover the distance, that is important."

Just something I thought to mention is that time and distance are not the problem. It is the lifespan of humans that is a problem.