New approach to space travel

[bowman316]

Ok, So I think we all pretty much agree that it is pretty much impossible to travel near the speed of light, and even doing so, it would take hundreds of years to travel between planets in out universe. But I think we are just thinking about space travel in the wrong way.
Any being that wants to travel hundreds of light years needs to plan for being on that ship for hundreds of years. They would need to grow their own food, probally have a huge reserve of nuclear power, to both power the ship, but also power lights to grow food. Which will also replace oxygen on the ship.
Basically Imagine a mini planet, that you can steer in a certain direction. The people living on this ship would go thru many generations before they find another planet with life, but they would be a self sustaining ship. As long as they had plutonium.

Why do we assume that a 100 year journey would be impossible?
I think we are just too narrow minded on this aspect of space travel. Maybe another civilization lives for 1,000.

 

[MeteorWayne]

This really isn't about SETI, so I'll probably move this to another forum. When I do so, I'll leave a copy here for a few days though. Just have to figure out where it belongs.

Meteor Wayne

 

[drwayne]

Unexplained?

 

[MeteorWayne]

, No I'm thinking SB&T...it is after all a valid way to look at what it would take for interstellar travel.

 

[williammook]

Investment in rockets reduces the cost of rockets, just like investment in computers reduces the cost of computers. The figure of merit for computers is the cost per computation. The figure of merit of rockets is the cost of momentum. Momentum is speed times mass. These two characteristics can be unwound in a rocket into two related factors, the cost of lift and the cost of temperature. A large high temperature rocket built cheaply outperforms a small low temperature rocket built expensively. Often by a large margin.

Why haven't we seen the advances in rocket technology that we have seen in computing and consumer electronics? Well, the first is that all space faring nations have powerful anti-proliferation treaties in place. Rocket knowledge unlike computing knowledge is largely secret. This makes progress difficult and important factors of performance unappreciated. So, a new approach to space travel need not cost the government anything. All they need do is declassify all the presently classified rocket technology, and teach in open courses aspects of propulsion that make it clear to every interested party what is needed to achieve the next level of performance. At that point, we will have effective investment in rockets and space travel.

Despite the lack of growth in rocket performance over the past 40 years, the first 40 years of rocket development proceeded by growing the fundamental measure of performance - cost per unit momentum. Rockets got bigger and faster at a greater rate than their costs increased. This lead to increased rocket performance.

Then, advance was cut short as a matter of national policy.

Back in the 1940s Werner vonBraun in his debriefing to the US Army outlined humanity's position in the cosmos and how rockets will impact that;

1) suborbital flight (ICBMs)
2) orbital flight (communications satellites)
3) lunar flight (lunar military base - world peace)
4) mars flight (off-world colony)

This is what he thought we could in his generation.

But the history is informative, and tells us a lot about how the future will proceed, once that future is permitted to proceed.

Interplanetary, and interstellar navigation with rockets transcends the Earth. It is also a matter of gravitational potential. All people of Earth are at the same gravitational potential in the universe. That's why we can walk, sail, fly, ride, around the world with very little energy.

This means that any development in space affects all people equally throughout the entire Earth. This naturally gives rise to global effects and once space based infrastructure is in place, global appliances or services.

Here's how we proceeded;

1920-1940 Suborbital rockets of increasing range and payload
1950-1960 Small orbital rockets (multi-stage)
1960-1970 Large cislunar rockets (large-multi-stage)

Here's how some thought we would proceed back in the day;

1970-1980 Very large interplanetary rockets (nuclear thermal)
1980-1990 Super-large interplanetary rockets, asteroid deflection (nuclear pulse)
1990-2000 Planetary sized solar pumped laser arrays & light sails, nearby interstellar travel (slow boat travel)
2000-2050 Large mass compressive collision to form engineered black holes (high-speed travel)
2050 - beyond - Advanced

This development would have cost less than the Vietnam war

In the meantime other developments unforeseen in the 1960s have opened up other avenues that are quite exciting - these developments make possible radical shifts in the way rockets are approached. One such development is MEMS rockets (Micro-electro-mechanical-systems rockets)

Microscopes can be used to see viruses on a slide.

A pattern can be projected backwards through a microscope to create very tiny pictures the size of viruses. This was the basis of the microdot - the spy tool of the 1920s.

Integrated circuits use the optics of microscopes to project tiny images onto chemicals that react to the pattern of light to etch patterns in metal, crystals and so forth. These tiny and precise patterns can be layered together. In this way virus sized patterns can be etched- and this technique allows the creation of virus sized electronic circuits.

Recently, tiny gears, ratchets, pawls, you name it, have been made.

This is the basis of the inkjet printer, and the HDTV plasma screen, and the HDTV DLP screen, and so forth.

Even more recently, tiny arrays of rocket engines have also been made.

At $1 per square inch, and 50 pounds per square inch - commodity rockets are well on their way to fruition. You can lift things more cheaply with these arrays than tires. They also last longer than tires - having more hours of use.

Because each engine is the size of a dot on an HDTV screen, and because there are tens of millions operating in parallel, they are supremely safe and reliable.

And, because of the geometry of small things - and the nature of rockets - their thrust to weight ratio is far superior to macroscopic rockets. Rocket thrust goes up with exit area of the rocket. Rocket weight is a function of the volume of material used to make a rocket. Make a rocket smaller and its thrust goes down more slowly than its weight.

A block 1 foot on a side occupies 1 cubic foot and there are 6 sides each 1 square foot six square feet total - six square feet of area for each cubic foot of volume. Triple its size to one cubic yard, and you have 54 square feet of surface area (6 x 3 x 3) and 27 cubic feet of volume (3 x 3 x 3) two square feet of area for each cubic foot of volume.

MEMS rockets will allow us to repeat the same developments we saw from 1920s through 1960s for personal rockets if we let it. Advanced GPS guidance and advanced computing also allow the development of pilotless flight systems at a cost that rivals that of packages. Relative size independence of MEMS based systems may mean that rocket based packages may be a possibility. Not a single rocket, but millions of rockets on a propulsive skin surrounding the vehicle to produce all manner of propulsive effects.

Another development, laser rockets, have the potential to improve on the performance of nuclear rockets, both nuclear pulse and nuclear thermal by increasing their temperature. Some scientists have shown that laser energy by itself may be used as a rocket dispensing with propellant altogether, and attaining large fractions of the speed of light.

MEMs based laser rockets, when combined with advanced laser beam steering technologies produce a very interesting range of possibilities.

As mentioned previously each advance in rocket performance has unintended consequences which led to an advance in human capabilities that changed the world. Then, real advances ended as concerns about proliferation ended public discourse of relevant details. Even so, the developments during the period of growth, when combined with knowledge about our place in the cosmos tells us much about how continued advance will change humanity.

WORLD PEACE
In the 1945 to 1955 the development of ICBMs and nuclear explosives made the entire world a battle field. This led to a cessation of large-scale global hostilities and a range of treaties to end nuclear and missile proliferation. From 1900 to 1950 the world had four major global confrontations. From 1950 to 2010 the world has had only regional conflicts of limited scope. This is the result of rocket technology. Marrying more advanced technologies to this basic system provides even more advanced weapons systems that provide the possibility of the unmanned battlefield turning warfare into trans national police actions - we have already fought several wars with few than 1,000 killed.

WORLD BUSINESS
In 1955 to 1965 the development of larger more capable multi-stage rocket made satellites possible, both piloted and unpiloted. This led to the development of weather satellites, navigation satellites, communication satellites, spy satellites - together these may be called information satellites. They gave rise to global services, GPS, Sirius, XM, global telephone, television, internet links. This gave rise to international business. Development continues at this level of rocket performance. Satellite networks (Teledesic) have been proposed that communicate between satellites. This follows on from point-to-point (Telstar) then to one-to-many (Sirius, XM, DirecTV) leading many-to-many (Teledesic).

WORLD VIEW
From 1965 to 1975 the development of very large multi-stage rockets made lunar travel possible. Human travel far from Earth and looking back at a remote and distant globe with no borders - a jewel in a desolate cosmos (Apollo 8, 1968) released an idea of the Earth as a single place. This combined idea combined with planetary data available for the first time in the history of science - resulted in the Gaia hypothesis (James Lovelock) - this is the Earth as a single organism. These ideas, along with images of Earth gave rise to the environmental movement.

At this point progress ended.

But we can see what the future holds for us once progress resumes;

The discovery that the dinosaurs were destroyed by asteroidal impact combined with our ability to deflect asteroids away from collision, and the idea of Gaia, naturally gives rise to the idea of intelligence and technology arising as protector of life on Earth. The ability to move the Earth by engineering repeated encounters between an asteroid Earth and Jupiter, enlarging the Earth's orbit over billions of years so that as the sun grows ever brighter, the Earth's environment is maintained also naturally emphasizes our role as a protective intelligence of Earth's life.

Aggressive development of space launch capabilities from the 1970s through the end of the 20th century would have naturally led to the development of large space power satellites - and the difficulties we have with global warming would have been easily addressed as a consequence.

The development and proper use of technology will be considered in light of its impact on ALL life on Earth and its impact on our ability to spread life across the cosmos and maintain life across the cosmos. A small highly engineered self-contained world flying freely in space, is the model for our technological future. In that view we move our technosphere -all the hardware that makes industrial life possible- off world to protect our biosphere.

Here is how it will proceed;

1) ICBM - world peace - suborbital - UN
2) info-sats - world understanding - orbiting - Internet
3) lunar travel - world view - large chemical - Environmental movement
4) interplanetary travel - world protector - nuclear/laser - world paradise
5) interstellar travel - world progenitor - laser light sail - making new worlds
6) cosmic travel - world seed - engineered black holes interacting - implementing new cosmos - Matrix

This all stems from the fact that our intelligence depends on a vast complex of natural systems for its maintenance. This natural system occurs only in exceedingly rare instances. Technology has the capacity to shape the natural world to support life, and hence us. This is true whether we build a fire on a cold winter day, or build a communications satellite network to turn the world into a wireless hotspot.

It is also true that early in cosmic history life as we know it could not exist. Also, at some point in the evolution of the cosmos life as we know it will once again be impossible. This leads to a cosmic paradigm for all life. Namely, enjoy the life you have, as you seek to extend the tenure of life beyond our allotted time. Programs to achieve this have already been published (Frank Tipler - Anthropic Cosmological Principle) Here, the very basis of life is shifted from carbon based life forms to emulations, and computers are made to run those emulations - computers that operate efficiently and easily in the cosmic conditions present in that distant age. In a sense the cosmos is accurately remembering us. This goes well beyond virtual reality since the elements within the computing system evolve in time maintaining all the richness and diversity of the earlier epoch, despite conditions not conducive to life as we know it at all.

Throughout all of this rockets and laser light sails, as well as engineered black holes that convert mass directly into bursts of gravity waves - creating a graviton rocket of extremely high efficiency - are all sufficient for our needs. Tipler, Thorne, and others have even opined as far back as 30 years ago, that time travel is possible around properly structured spacetime. How do we structure spacetime? Miniature black holes that dance around one another. How do we make those? Compress large shaped blocks of iron-56 to very high density by colliding them at 1/3 light speed or more. How do we do that? Laser light sails used for slow boat interstellar travel.

Each step opens up the potential of the next one - if we are brave enough to take it.

Since the 1940s we have instituted specialist reviews of technologies and their impact on our war making abilities and eventually on all of society. By the 1970s the plug was pulled on moon travel and the continued development of rockets. Research continued, and offending notions were marginalized in the public mind. However the potential is there, all it takes is our willingness to embrace our future despite the challenges that future places upon cherished ideals of the past.

Rockets are enough.

It is us we have to change to realize the future we deserve.

 

[MeteorWayne]

Too long a post to read through the whole thing yet, but a few comments.

One other major factor you didn't mention is that the volume of space launches wasn't, is not, and likely not be high enough to acheive the economies of scale that have led to cheaper computers for many decades to come.

"1950-1960 Small orbital rockets (multi-stage)" more like 1959-1967

MW

 

[MeteorWayne]

As I said, this thread doesn't belong in SETI, so I will move it to SB&T. I'll leave a copy here for a few days.

 

[bowman316]

I don't know what that long post had to do with the original post. I guess I was poposing having a self sustaining ship, that could grow food, replace CO2 with O2. Breed animals, and the whole time be traversing the universe. The inside of the ship would be like Noah's arc. 2 of every animal. Imagine a ship the size of the mother ship from independence day.

you may need to spin it to make artifical gravity. Or just live in 0 gravity. But This is something you could actually do. As long as you have a nuclear, or solar power source. The hard part would be building the ship, which you would have to piece together in space most likely.

 

[redbert]

I'll transition this to SETI;

bowman316 and illiammook,

If we can do any of these ideas; could other ET civilizations have done it also?


"if there was one star faring race in this galaxy (spreading at about a thousandth of the speed of light: 0.001c) that existed any earlier than the last 1% of the universes history, they would either have made it here or at least we would have detected them already"


"Where are they?" -Fermi

 

[williammook]

Too long a post to read through the whole thing yet, but a few comments.

One other major factor you didn't mention is that the volume of space launches wasn't, is not, and likely not be high enough to acheive the economies of scale that have led to cheaper computers for many decades to come.

"1950-1960 Small orbital rockets (multi-stage)" more like 1959-1967

MW

The volume of demand is a function of cost and availability. Lower cost, greater availability both lead to greater demand. It is not unusual for experts to not see the size of markets for new technology. In the 1800s the New York Times wrote that the telephone was a great technological achievement and could imagine that one day every city might have one. In the 1950s IBM famously projected that global demand for their new computers might be 10 to 15 total.

These projections were accurate in their day, just as yours is accurate today. However, lower launch costs, improve availability, reliability, of launches - and demand will rise dramatically.

Let's look at something I've studied to some extent. There are over 400,000 people worth $30 million or more. Out of this cohort one or two every year - for a while - purchased a flight aboard a Soyuz.

If failure rates dropped to 1 in 200 rather than 1 in 20 and costs dropped to $2 million per flight instead of $20 million per flight - if training was less rigorous, if operators were more market savvy, global demand for personal orbital flight would swamp present commercial launch volume. The revenue earned by such a service would exceed that of the Concorde - and certainly justify the development of an orbital vehicle that achieved these ends. Such a vehicle would be a new approach to rocket launch.

Reusable launchers built around MEMs rocket technology have the capacity to achieve all these ends.

Ambitious space infrastructure must treat the launcher technology as part and parcel of the infrastructure being developed and build the needed technology with the needed economies of scale into a project and financed along with the project. Iridium and Teledesic failed to meet their targets because they did not do this and died as projects because they demanded too much of space launch without examining the cost of achieving the launch rates and reliabilities needed to make the project work. Each of these projects alone would again have swamped the demand for space launch in the period they were put into place. Doing this is no different than say building a dam in a remote location and having the construction company factor the cost of the roads, bridges, and company towns needed to support construction along the way. Hoover dam, the Panama Canal, built a huge infrastructure to support the primary structure. Massive satellite networks of satellites are possible and can provide a wide range of services, communications, navigation, power - on a global scale. They also create a huge demand for space launch. Any project involving massive satellite networks will do well to factor the cost of developing the appropriate launch technology into the cost of the overall project. Failure to do so will doom such a project to failure, just as failure to plan appropriate support would haved doomed terrestrial projects.

I have looked at the potential of a global wireless internet delivered by a satellite. This network will cost on the order of $25 billion to erect and that includes the construction of a fleet of reussable heavy lift launchers. The revenue earned by such a service exceeds $83 billion per year. A company like Boeing or Lockheed that partnered with a communications company to gain say 30% of this total, would earn more money each year from this project once realized, than the entire world spends per year on space launch. This would be a gam changing sort of development and usher in the next era of space development. Of course, those who worry about missile proliferation and control - might worry about such a development. However, that just leaves this innovation to others if we do not stand up and say we will lead.

Engineers and experts twiddling their thumbs and whining about launch volume miss this rather important point.

1959-1967? haha - why argue over precise dates? That's why I used a decade by decade accounting. It is quite accurate 1959-1967 rounded to decade is 1950-1960 decades - haha so, I'll stand by my earlier statement.

For example why did you start your counting of space launch in 1959 when everyone knows Sputnik orbited the Earth in 1957 and the US countered in 1958? haha - why those dates when we look at capabilities? These developments didn't arise whole cloth out of nothing! Eisenhower worried that vonBraun would use an Atlas test in 1956 to orbit a satellite and bring unwanted attention to our missile programs and repeat the losses our atomic programs suffered with the Rosenbergs. The Horizon debriefing calling for an orbital missile occurred in 1948 - but it was the decade of the 1950s that big multi-stage rockets were developed with orbital capabilities first - so I'll stick by my decade by decade accounting.

 

[williammook]

I'll transition this to SETI;

bowman316 and illiammook,

If we can do any of these ideas; could other ET civilizations have done it also?


"if there was one star faring race in this galaxy (spreading at about a thousandth of the speed of light: 0.001c) that existed any earlier than the last 1% of the universes history, they would either have made it here or at least we would have detected them already"


"Where are they?" -Fermi

Anything said about ETI is speculation since it is done in the total absence of any evidence. You are familiar with Fermi. Are you familiar with Drake? Dyson? Clarke? Sagan? Kardashev?

Drake is famous for an equation that estimates the numer of ETIs. It consists of a rate times a lifetime and a number of factors. This is like figuring out the number of lightbulbs by looking at the rate lightbulbs are made and figuring out how long they burn. So, if you make lightbulbs at a rate of 100 per hour and they have a lifespan of 2000 hours - then you have 200,000 lightbulbs. The factor comes in when we want to know the color of the light bulb. Say half are red. So we have a factor of 0.5 or 50% - so our formula is

number = rate x factor x lifetime = 100/hr x 0.5 x 2,000 hours = 100,000 red bulbs

Now, Drake did a similar analysis of star systems...

number of ETI = rate of star formation x factors x lifetime of ETI

The factors include,

percentage of stars with planets
percentage of planets that support life
percentage of life that attains intelligence
percentage of intelligences that attains technical capabilities
percentage of technical species that attains space travel

Now none of these factors is known in principle, but they can be found out using the appropriate science. Which makes the equation important. At present, the number is large or small depending on whether you're an optimist or a pessimist - real pessimists say we're not space faring and the number is zero. lol. Optimists say the nearest space faring species to us is no less than 200 light years away. I say the nearest ETI is in the next galaxy. That is, ETIs are common on the scale of the cosmos Rare on the scale of galaxies.

Here's why.

I'm an optimist on all factors except intelligence. That's because intelligence requires multi-cellular bodies, requires brains. Look at the history of life on Earth. When conditions were right for life - life arose immediately. But it was single celled for nearly half of the history of life on Earth. Specific conditions called the oxygen crisis led to a die off and the development of multi-celled life forms and then to their subsequent domination - in the forms of multi-celled plants and animals. Then it took nearly half the age of life on Earth for big brains to be developed.

This suggests that big brains are hard for evolution to produce.

Which suggests they are rare.

It took nearly the age of the universe for us to attain our brain power - and we might have been the lucky ones.

So, that's my take on the Drake equation - and my best guess when speculating about alien life forms.

Even so, some are less pessimistic than me. They are optimists who see the bar scene in star wars, or read Larry Niven's Draco Tavern, or see ten-forward on TV, or even Douglas Adams' Restaurant at the End of the Universe, and say yeah, that's how it should be! They ask- where are they? - with a passion!

Fermi's question was a cautionary one. If lifetimes are short - the number is low. The atomic power that makes interstellar journeys possible - also makes atom bombs possible.

Some say, where are they? We modify our environment on a large scale. An interstellar or intergalactic species would modify their environment on a large scale. Even if we're not being visited - Where are the giant Exxon signs?

Kardashev created a scale to rate such civilizations. This is a logarithmic scale with 10 billion as the base. This rates civilizations as to type - type zero is one megawatt - what you get when you organize 10,000 people, or 1,000 animals to a common purpose. 1e16 watts is what the Earth intercepts. One planet's worth. We use about 1e15 watts - so we're about 0.7 on the Kardashev scale. 1e26 watts is what the galaxy puts out - this is Kardashev type 2. 1e36 watts is what a large fraction of the universe puts out - this is Kardashev type 3. A single individual puts out about 100 watts of useful work. A kardashev -0.2 civilization. A cellular organism is near -1 on the Kardashev scale.

So, are there any K1? K2? K3? civilizations?

Astronomers look out into the cosmos and it all looks natural. So, where are they? in a larger context.

Dyson says wait a minute - how do we know what is natural? We might be like an anthill living under a giant Exxon sign, and we look up and see that sign and think its a part of nature, since we are clueless how to make an Exxon sign, and why such a thing - larger than our entire anthill - would ever be built even if we knew how to do it.

This was one of the points of his famous Dyson sphere - a sphere of space stations orbiting the sun intercepting ALL the light from the sun - would be a K2 civilization - but from the OUTSIDE - it would look like a red giant! In fact, at the time there was no natural explanation as to why certain red giants would be the size and temperature they were (a surface temperature around 72 degrees!)

But your point is rather more poignant than that. Why aren't ETIs visiting Earth? They must not have the capacity to travel the deeps of space. That's your conclusion. Well, this is where Clarke is interesting. Stars are as common as sand grains on a beach. Life might be as common as life on a beach. Technology may exist that allows ETI to span the galaxy as easily as we can walk a beach. Where are they? Well, anyone asking this question, according to Clarke, is like a microbe inhabiting the surface of one of the grains - asking where are they? and concluding that moving from grain to grain is impossible! The point is, put yourself in the position of a creature capable of walking down the beach. Do they stop and examine every single grain of sand and commune with every single microbe on each? No! They scan the beach, and find things of interest, perhaps an attractive bather of their own species - and walk across the billions of grains unaware of the range of life beneath their feet.

Clarke concludes that we are rather nearer apes than angels in the grand scheme of things - and shouldn't really expect much attention from our betters until we better ourselves.

Then Clarke expands on that slightly by saying thinking we're nearer apes than microbes gives a lot more credit than we likely deserve.

Some have replied, But where are the other microbes?

Recently some sci-fi writers have observed the long history of life in the cosmos. The Sun is a population 1 star. It has metals. Its planets have metals. We're made of metals (carbon is a metal in this context) - Population 1 stars are made of older population 2 stars. Pop 2 stars are made of hydrogen. Metal is made during the supernova explosion of a pop 2 star. It took have the age of the universe for pop 1 stars to form. It is unlikely that there was any life before pop 1 stars got started - and they all got started about the same time.

Now cast your mind to the Kalahari desert. Most of the year its dry. But there is a rainy season. When it rains in the Kalihari - there is a fabulous springing forth of all manner of wildflowers, insects, and so forth - they live fast and die young - and fall back into the desert.

The point is, all these life forms are synchronized to the day - water comes.

Could it be life on the cosmic scale is similarly synchronized? The cosmos is teeming with life around every corner, in every variety - but they are at precisely the same age as us technologically - synchronized by some external event. Say, the development of pop 1 stars combined with the explosion of gamma rays from the center of our galaxy a few billion years ago. The trilobites died out and that die out is not correlated with rare Earths of a meteor impact - some think a gamma ray burst did them in. If the gamma rays came from the supermassive black hole at the center of our galaxy - ALL life in the galaxy may be synchronized just as life in the Kalihari desert is synchronized.

Sci fi writers have recently speculated that there are plenty of technical civilizations and that they are all on approximately the same scale as us - and the moment we begin crossing the cosmos - we will run into them. Or if we avoid developing our space faring capacity for generations more - then we will run into them on Earth - and they will rightly view themselves superior.

In this case, life in the galaxy will be very much like life in the Kalihari - it will live fast and die young! The great depth of time of the cosmos will be meaningless. At least within the galaxy - since the synchronizing event destroyed the advanced species that may have existed before. Extra-galactic civilizations in this case will be a ringer - where are the K3s? haha.

Even here there is astronomical evidence to suggest that there are older and more capable civilizations out there. A Smithsonian survey of galaxies shows that galaxies occur at the edge of bubbles of darkness. Some scientists speculate that there were super-string explosions that pushed material in the early universe into this form. I have suggested that there are galaxies in these bubbles, they have just been turned off by their owners. The spherical form comes from the fact that the K3 civilization is economising its use of resources. Why let the stars burn freely if you can harvest the fuel for your use? Why waste it with fusion which is only 10% efficient when 100% rest mass is available?

Even our astronomers know that there was a time before which life was impossible in the universe. There will come a time when life is again impossible. When all the stars burn out. This knowledge will be well known to a K3 civilization. What are they going to do with that knowledge? That's right, turn off all the stars in reach, and organize the material world to survive for the long haul. The Smithsonian surveys reflect this. Of course the ants in the anthill look at the Exxon sign and come up with a natural explanation! haha..

Where are they?

They are in the cosmos - in great variety and in great multitude. Why are they not in your life? in your world? Why should they be?

 

[williammook]

As I said, this thread doesn't belong in SETI, so I will move it to SB&T. I'll leave a copy here for a few days.

SETI - is search for ETI - Kardashev took the question of this post very seriously and came up with his scale of ETIs as a result. This is a useful question if you wish to move beyond electromagnetic spectrum in your musings - though John Kraus would hate me saying that! haha.. Even Sagan speculates about vonNeuman probes in his work with Shklovski Intelligent Life in the Universe.

Will my postings here in response to comments be transferred when you erase this?

 

[williammook]

I don't know what that long post had to do with the original post. I guess I was poposing having a self sustaining ship, that could grow food, replace CO2 with O2. Breed animals, and the whole time be traversing the universe. The inside of the ship would be like Noah's arc. 2 of every animal. Imagine a ship the size of the mother ship from independence day.

you may need to spin it to make artifical gravity. Or just live in 0 gravity. But This is something you could actually do. As long as you have a nuclear, or solar power source. The hard part would be building the ship, which you would have to piece together in space most likely.

This is a 'generation ship' used in 'slow-boat' interstellar travel. This was proposed in the 1920s by John Bernal. Its basically a space colony with a nuclear reactor and a nuclear rocket. It can also be moved by laser light sail. I spoke of this in my response.

http://en.wikipedia.org/wiki/John_Desmond_Bernal
http://en.wikipedia.org/wiki/Bernal_sphere

The US DOD did a study on building an interstellar ark in 1958. Freeman Dyson reported on it in his book - Infinite in All Directions. It was an 8 million ton Orion type spacecraft that used depleted uranium as its pusher plate, so when it arrived at its destination, the 100,000 settlers would have plenty of fuel to build nuclear power stations for their industrial infrastructure. This was a survival mechanism in the event we had a global thermonuclear war and environmental degradation was such that life on Earth was doomed.

Lighter weight versions are possible. Self sustaining colonies - which are the basis for interstellar arks - may mass as little as 500,000 tons and have 5,000 people aboard, according to NASA studies. Each colony requires about 100 tons per person. Ten billion people would require 1 trillion tons of material.

The asteroids between Mars and Jupiter mass about 3e18 tons. Only 1/3,000,000th of the asteroid mass are needed

To build these stations, and the means to move them between worlds requires rockets. Immensely capable rockets.

A self sufficient space colony becomes an interstellar ark when attached to a propulsion system capable of moving it between stars.

The most efficient way we know of to do this was proposed by Robert Forward back in 1983. A thin film high efficiency PV device absorbs sunlight and reflects solar wind - which holds it stationary above the solar surface. A high efficiency free electron laser emits a portion of the absorbed energy in a collimated beam. That beam passes through a lens system out near the orbit of Uranus - reflecting a portion of it to maintain its position - transmitting the bulk to a target heading out to a nearby star.

The target is a light sail that reflects light to produce propulsive effects.

150 megawatts of light is needed to produce 1 newton of thrust. The light sail is 5x more massive than the payload it carries. So, this is 600 tons per person. So, 1/500,000th of the asteroid belt would be needed to produce enough space arks and light sails for 10 billion people. Another 1/500,000th of the asteroid belt would be needed for the solar pumped laser array and so forth.

An 8 million ton ship requires 8e10 newtons of thrust. That's 1.2e19 watts of laser energy. With an overall efficiency of 20% that's 6e20 watts of solar energy. At 3 million km radius from the sun, 3.4 MW per square meter of sunlight. So, 6e20 watts requires 1.76e14 sq m - 176,000 sq km. a disk 7,478 km across. The entire surface of the sun is 34,587,221 times larger than this.

A thin film a few microns thick would total a few hundred million cubic meters fabricated into this toal a volume only a few hundred meters across. Ditto for the light sail, and lens. Large areas, thin film, low mass.

The laser array and lens are used by many many starships over time. A 40 year lifespan and 3 months per boost - means 160 ships are supported per laser array. At 3 tons per cubic meter the mass of this system is equal to 30 ships.

Accelerating at 1 gee - requires a boost time of 4 months to get to 1/3 light speed. 1/3 light speed gets you to nearby stars in 15 to 25 years. Laser arrays AT the stars slow the ships down. The very first ships use a staged lightsail approach devised by Bob Forward to slow down. These ships carry the parts for a return beam. Once in place, travel between stars in decades is possible.

3 ships per year - each carrying 100,000 people - are supported by this laser array. 3,300 such arrays - allow 10 billion people to fly between the stars in 10 years - which is basically everyone flying between stars constantly.

A network of such arrays deployed on star after star after star - creates an expanding wave that moves at 1/3 light speed from Earth. As the arks spread out they become thinner and less dense.

Once we have the technology to build these things, and dispatch them, there is little difference between sending one forth and sending 100,000 forth into the cosmos. That is, personal interstellar travel will happen, if it happens at all.

Everyone indeed will go to the moon! (the moons of endor!)

Only 100,000 arks each carrying 100,000 people support 10 billion people.

Where are they?

Separation between stars is about 5 light years in the Perseus Arm where we live. This means that in about 100 light years - or 301 years from the date we start dispatching interstellar arks - even if we dispatched every single one of the Earth's 10 billion inhabitants of that era - there would be fewer than 2 arks per star system! In only 10 years there are only 3,000 arks per star system.

Range (LY) Stars Arks Time (years)
10 33 3,030 31
20 268 373 61
30 904 110 91
40 2,144 46 121
50 4,188 23 151
60 7,238 13 181
70 11,494 8 211
80 17,157 5 241
90 24,429 4 271
100 33,510 2 301

The Galaxy is 100,000 light years across - and the cosmos 10,000,000,000 light years across.

Where are they?

Where would we be?

After the first 300 years of expansion - assuming no improvements in underlying technical capacity that speed things up - the human race will have dropped to 1 ark per star system or thereabouts - and our ability with this technology to cover every single star system will not exist. There will always be unexplored star systems. About 1 million star systems per ark - after the first 100,000 stars are explored

Even optimistic assessments of nearby species place them further than 200 light years across

Careful readers will note I have made an assumption.

That the number of humans wll never rise above 10 billion and the number of arks will never rise above 100,000 - there is a reason for this. Life aboard the ark will be limited - so while in transit, reproduction will not take place. In fact, life aboard a space ark will require strict control of population.

But new arks and new populations could be spawned at distant stars - this is a form of vonNeuman machine - with humans as part of the machine - which could fill the galaxy in a few million years - just as humans filled the Earth in a few million years.

Which means;

it hasn't happened,
or
it happened, and we just don't see it.

If it hasn't happened it could mean

self replicating systems don't exist (repressed like cancer)
we are alone (no ETIs in galaxy)
we are being isolated (zoo hypothesis)
development of life is synchronized and the oldest tech species is less than 2 million yo

this last idea results from the discovery of a super massive black hole at the center of the galaxy and the discovery that trilobites were made extinct by a global event not asteroid impact - possibly a gamma ray burster. If this was the supermassive black hole - then ALL life in the galaxy is synchronized and likely in lockstep.

 

[kelvinzero]

Ok, So I think we all pretty much agree that it is pretty much impossible to travel near the speed of light, and even doing so, it would take hundreds of years to travel between planets in out universe. But I think we are just thinking about space travel in the wrong way.
Any being that wants to travel hundreds of light years needs to plan for being on that ship for hundreds of years. They would need to grow their own food, probally have a huge reserve of nuclear power, to both power the ship, but also power lights to grow food. Which will also replace oxygen on the ship.
Basically Imagine a mini planet, that you can steer in a certain direction. The people living on this ship would go thru many generations before they find another planet with life, but they would be a self sustaining ship. As long as they had plutonium.

Why do we assume that a 100 year journey would be impossible?
I think we are just too narrow minded on this aspect of space travel. Maybe another civilization lives for 1,000.

Hi Bowman,
Preaching to the converted here.

Only thing I would note though is that we have a whole solar system to colonize here before worrying about how we get to the next one.

Sure, other stars may have more earthlike worlds, but earthlike worlds are not the way forward. They are very hard to leave or trade from. I think a world like ceres could be a much better centre for a space faring civilisation. It is basically a big ball of rock and ice only just big enough to be spherical. You cant live on it but you can build cities into it. The weak gravity has some overhyped health problems but solving these are not a millionth as hard as interstellar travel (during which you would probably also have weightlessness).

Imagine a solar system where half of these worlds had colonies built into them, Cities of interconnected spherical chambers several kilometers across, and travel times between worlds varied from years to days across an entire solar civilisation.

http://en.wikipedia.org/wiki/List_of_So ... ts_by_size.

That is a great link. I highly recommend it for dreamers.

 

[bowman316]

The only problem I see with a self sustaining space colony is the generation of water. Sure you could turn waste into water, but eventually that would run out, right?

You would have to generate new water somehow.

 

[MeteorWayne]

Sorry, 59 to 67 was a typo, should have been 57-67. I rememeber it live

 

[williammook]

Sorry, 59 to 67 was a typo, should have been 57-67. I rememeber it live

Yep!

 

[emudude]

I spent around an hour carefully reading the posts in this forum, especially the ones by williammook...those posts have made up what has been by far the most interesting read I have had in a long, long time. Thank you very much for contributing your logical analysis of past trends and extrapolating these into meaningful assessments of likely future trends...this has given me a great deal to think about indeed. :mrgreen: :mrgreen: :mrgreen: :mrgreen: :mrgreen:

 

[williammook]

The only problem I see with a self sustaining space colony is the generation of water. Sure you could turn waste into water, but eventually that would run out, right?

You would have to generate new water somehow.

With sufficient energy we would replicate the water cycle we have on Earth in the interstellar ark

http://www.nss.org/settlement/nasa/Cont ... gement.htm

There would be losses, as there are losses of air and other materials, but would would carry spare water in lakes and rivers and storage tanks. This is part of the 100 tons per person. Over a 100 year period, we would visit several stars, and wherever there was an Oort like cloud of cometary material - a Kuiper belt - we would rendezvous with an appropriate cometary body and draw whatever water we needed.

Water is rather easily recycled with sufficient energy. Energy is the product in short supply on an interstellar voyage.

On an interstellar ark this will come from laser energy beamed to the ark in transit. Propulsion beams are replaced by multi-spectral transit beams to power the station with bandgap matched solar panels. The light sail then acts as a concentrator. The power levels are far far less than those during propulsion phase. Within half a light year of the solar system, or target star, laser light is supplanted and replaced with starlight or sunlight. This is the first and last two years of the voyage.

Nuclear power will also be a likely backup. High temperature nuclear reactors form an emergency backup.

For interplanetary navigation before and beyond the interstellar beam, nuclear fusion propulsion with the light sail now acting as a propulsive canopy provides secondary thrust and navigation outside the laser beam.

http://en.wikipedia.org/wiki/Nuclear_pu ... ion#Medusa

Deuterium and tritium - a nuclear fuel - is very likely to be found in any comet's water supply. Which is important.

Water and carbon formed closed systems - as they do on Earth. Instead of gravity keeping things in place, pressure vessels keep things in place. So leakage is a problem. Loss rates and spare capacity are such that supplies will last hundreds of years with less than 20% loss.

With 1/3 light speed capability - transit times of 15 to 25 years are typical - so, periodic replacement from cometary sources is easily accomplished.

Life spans are likely to be increased to hundreds and thousands of years - so transit times are not a problem.

http://www.ted.com/talks/aubrey_de_grey ... aging.html

Improvements in Virtual Reality, and interstellar hypertext transfer protocols, provide a means for people to share realities, experiences and findings of others. So, travelling space arks will have powerful radio telescopes to keep in touch with the rest of humanity. Probes sent on ahead of piloted craft will send back models of the new worlds discovered and they will be explored digitally before folks get there. Long range sensing will also be important.

 

[eburacum45]

Excellent posts, William!
I am not sure that everything will come about quite as you describe, however.

I'm pretty sure that a generationship could not be easily accelerated at 1 g using light pressure alone; light gives only a tiny amount of momentum to a sail. Generation ships would be very massive objects indeed, and would need sails so big they would tear apart at one gravity of acceleration.

Similarly a statite light collection system would be quite tricky to balance on solar light pressure while collecting power at full efficiency- unless you can find a way to make very thin, light and efficient solar cells. Perhaps one day...

Finally Bob Forward's scheme for reversing thrust on a light sail required unfeasibly focused laser beams- at that distance the beam would spread because of diffraction until it is exceedingly feeble.

To increase the momentum transferred to spacecraft of this nature you want to use particle beams rather than just light.

 

[williammook]

Ok, So I think we all pretty much agree that it is pretty much impossible to travel near the speed of light, and even doing so, it would take hundreds of years to travel between planets in out universe. But I think we are just thinking about space travel in the wrong way.
Any being that wants to travel hundreds of light years needs to plan for being on that ship for hundreds of years. They would need to grow their own food, probally have a huge reserve of nuclear power, to both power the ship, but also power lights to grow food. Which will also replace oxygen on the ship.
Basically Imagine a mini planet, that you can steer in a certain direction. The people living on this ship would go thru many generations before they find another planet with life, but they would be a self sustaining ship. As long as they had plutonium.

Why do we assume that a 100 year journey would be impossible?
I think we are just too narrow minded on this aspect of space travel. Maybe another civilization lives for 1,000.

Hi Bowman,
Preaching to the converted here.

Only thing I would note though is that we have a whole solar system to colonize here before worrying about how we get to the next one.

Sure, other stars may have more earthlike worlds, but earthlike worlds are not the way forward. They are very hard to leave or trade from. I think a world like ceres could be a much better centre for a space faring civilisation. It is basically a big ball of rock and ice only just big enough to be spherical. You cant live on it but you can build cities into it. The weak gravity has some overhyped health problems but solving these are not a millionth as hard as interstellar travel (during which you would probably also have weightlessness).

Imagine a solar system where half of these worlds had colonies built into them, Cities of interconnected spherical chambers several kilometers across, and travel times between worlds varied from years to days across an entire solar civilisation.

http://en.wikipedia.org/wiki/List_of_So ... ts_by_size.

That is a great link. I highly recommend it for dreamers.

You made an interesting point about energy. That is the critical factor. You mentioned trade that's another critical factor. Energy expended at a certain rate determines power levels, and also mass flow between worlds. Gravity is a factor, location another. There is a minimum energy between worlds - Hohmann transfer orbit.

http://en.wikipedia.org/wiki/Hohmann_transfer_orbit

Ultimately we get power from the sun or some other nuclear source.

What mass flow rate is needed?

Americans in the late 20th century and early 21st century used about 5 tons per person per year. This might be considered a benchmark. When one considers that 2 tons of that is fossil fuel, and another 1 ton is basically gravel, you end up seeing that 2 tons per year supports a person at a fairly high living standard. 10 billion people living at late 20th century living standards, replacing fuel with laser energy generated in space, and replacing gravel with locally derived stuff - requires that transport of 20 billion tons of material per year.

The asteroid belt is a good choice of early stage feedstock. The belt consists of 3e18 tons of materials in 1.6 million bodies of 1 km or more.

http://en.wikipedia.org/wiki/Asteroid_b ... cteristics

If 5% of this material is industrially useful, this is 1.5e16 tons of materials. Enough to supply 10 billion people for 1 million years without recycling. If they consume at the rate of modern billionaires - 10 tons per year (principally jets and yachts and very large homes - which in this age would be personal spacecraft, and personal space colonies) - then there is 100,000 years capacity. If they consume at 50 tons per year (personal interstellar arks) then there's 50,000 years supply - but this opens up other star systems for use.

Back to our mining analysis ...

Ejecting small bodies a few dozen meters in size using solar powered electromagnetic launchers at the asteroid belt brings materials wherever they're needed - Mars, Moon, Earth...

http://en.wikipedia.org/wiki/Electromag ... nch_System

For Earth the ejectors impart the 1500 to 2500 m/sec speeds to lower the perhelion of the orbiting mass to 1 AU, oriented and timed so that the mass arrives near Earth when it reaches perihelion. This operates for four months out of a year when the Earth is in synodic range. The other 8 months out of a year, solar energy is used to process materials for shipment during the synodic season.

Rocket action is used to slow the mass as it approaches Earth. This is easily achieved by using a small solar powered electromagnetic launcher that ejects unwanted materials left over from processing on Ceres - as reaction mass to slow down the wanted materials.

The ejection speed is selected to minimize energy - 5,000 m/sec approximately - which means reaction mass is 63.2% of the total mass that started out from Ceres (or other dwarf planets in the asteroid belt)

It takes about 7 km/sec to bring something from Ceres along a minimum energy orbit. Most of the delta vee is done near Earth - which is good, because sunlight is more powerful here. Ejecting material from the asteroid slows it down.

It takes energy to run the ejection unit and 1.72 tons of waste is ejected for each 1 ton of useful material. At 5,000 m/sec means that 21.5 gigajoules is needed (about 3.5 barrels of energy equivalent) is needed to retrieve each ton of useful material into Earth orbit. The ejected material is made up of nanoparticles and fabricated so they evaporate during ejection so they do not pose a navigation hazard.

Recall we use solar energy, and also recollect that we consume 2 tons of raw materials per year to maintain a very high lifestyle for everyone. That's 43 Gigajoules per year. There are 31,557,600 seconds in a year, so each person requires 1,363 watts continuous to maintain the mass flow rate from Ceres needed. With a 50% efficient solar panel (recently achieved by Boeing's Spectrolab) this requires only 2 square meters of solar collector. Using thin film optics and high intensity photocells, this only costs $14 CAPEX - which with a 40 year life span - translates to $0.02 per ton transport cost!!! (for the energy) Similar analysis shows that each ton would cost $0.10 - ten cents ...

The raw materials enter into a sun-synchronous polar orbit - the orbits used by spy satellites - that way they may be conveniently deorbited wherever they are needed - and pass over every point on Earth every 12 hours - as the Earth rotates under the orbit.

http://en.wikipedia.org/wiki/Sun-synchronous_orbit
http://en.wikipedia.org/wiki/Polar_orbit

As these materials accumulate in a ring -

http://en.wikipedia.org/wiki/Planetary_ring

And are met by a large tele-operated solar powered factory satellite brought to orbit by nuclear pulse rocket.

http://en.wikipedia.org/wiki/Project_Or ... propulsion)#Sizes_of_Orion_vehicles

Using a microfission trigger for an aneutronic fusion device to power these vehicles, this is a way to 'burn off' our nuclear stock pile, without causing massive pollution. Only a limited number of ships are needed to lift the initial factories, which then use the raw materials arriving on orbit each day to expand their capabilities.

Teleoperation was developed for handling nuclear materials 70 years ago. The innovation of the assembly line turned 100 years old in 2008. It ushered in the modern consumer culture and the American way of life - by increasing wages of workers 5x (the famous $5 per day pioneered by Ford, workers made enough to buy the cars they made!) while increasing their productivity 10x which made Ford and his workers rich simultaneously! This is an inspirational story worthy of emulation today - and ends the historic stand off between management and labor.

The USA never adopted teleoperation into its factories. Partly because the technology was initially developed under military auspices and was partly classified. Partly too because the USA elected to give its manufacturing capacity to its allies, and its extraction capacity to its friends (while isolating its enemies from trade). This was done because of an economic truth - $1 worth of ore is made into $5 worth of metal, and that trades in $25 worth of services. Similarly $1 worth of wheat makes $5 worth of flower which turns into $25 worth of pastries. By exporting extraction and refining and concentrating on banking and retail - the USA imposed what it thought was a permanent disparity of income betwen itself and the rest of the world. This protected us in the nuclear age since poor nations don't attack rich nations. And, rich nations can afford better weapons. Things have not worked out as folks in the 1940s had planned - well they only planned for 50 years - but we haven't addressed these issues in a long long time, and most folks don't know and don't care - meanwhile, others aren't keen to educate us - especially if they benefit from our ignorance.

Raw material shortages, along with environmental costs, have increased the cost of raw materials. Automation and improvements in productivity, have increased the value of the manufacturing function. Meanwhile, internet and software have commoditized banking and retail. America has ignored this trend over the past 30 years - and has paid the price.

Anyway, teleoperation developed by the USA 70 years ago, never made it into the factories - and so - we're still using 100 year old assembly line technology - except - those who have benefited from US ignorance in manufacturing - have made progress - this paper is nearly 10 years old now

http://sciencelinks.jp/j-east/article/2 ... 814533.php

Bottom line, I don't want to hear any argument from folks who say this is sci fi - haha - long before we have fully unmanned factories, we will have teleoperated factories. In fact with modern sensing and communications and computing systems - we have the means to institute teleoperated jobs today.

This reduces transport cost of workers, and radically improves worker opportunity. Apu needn't leave his beloved India to work at the Quickee Mart in Springfield - if a teleoperated robot technology existed. Mr. Burns could move his nuclear power plant to the bottom of the ocean, and Homer Simpson could eat donuts at a teleoperation office erected near his home. His $20,000 automobile is replaced by a $2,000 teleoperation unit - and the $1 million per lane mile road is replaced by a $1,000 broadband channel.

In the 1910s and 20s - adoption of the automobile and trucks, freed commerce from the train stations and shipping ports in America. As a result people could work and buy and sell at a far greater number of places. As a result, the combinations and permutations of work and business increased factorially as speeds increased. Allowing all people everywhere to interact in work and business provides a radical improvement in humanity's ability to create wealth - quite apart from raw material and energy limits. This is why teleoperation and space communications is a necessary adjunct to this program described here.

Bottom line here we are deploying teleoperated factories on orbit. In this way, anyone living anywhere can work anywhere else - including orbit - without a lot of infrastructure. With a steady stream of materials arriving from the asteroid belt into the 'material plane' above Earth processed into goods and food and fiber - the teleoperated factories farms and forests have a rich field of materials to operate from. Its easy to move thing through the orbital plane. Easy to keep things from wandering away via shepherd moons with engineered orbits. Easy to fabricate things in space using teleoperation and solar power. Easy to send things directly to users anywhere in the solar system with solar powered electromagnetic launchers. Products rain down from the heavens continuously - in response to satellite telephone calls - and people find work easily that is highly productive - no matter where they live.

We also easily expand the capacity of production on orbit - and this is the halfway point to anywhere. It takes 9 km/sec to lift an object from Earth orbit - only 0.5 km/sec to bring it down. It takes another 9 km/sec to cause an object to escape the solar system.

http://en.wikipedia.org/wiki/Delta-v_budget

So, teleoperated factories within a 1/10th light second of Earth's teeming population, powered by constant sunlight fed with a steady stream of rich asteroidal materials, equipped with an electromagnetic launcher technology that sends products throughout the solar system - provides a means to create wealth on a scale unprecedented in history.

And this is before automation of the tele-operated systems provides even greater wealth potential!!

The USA is keeping its missile secrets classified in the misbegotten notion that it is made safe from missile and nuclear proliferation. Even while nations as backward as North Korea and Iran build space launch capability.

We need to address again the thinking -even the secret thinking- of the post world war two era - in light of the realities of today's world - and make best use of what we are best at - to contribute again to a mighty improvement in what humanity is capable of.

The transition is seamless from the world we see today to the world I just described, to expanding beyond the confines of Earth, and beyond the confines of the solar system.

We ALREADY have all we need to carry this out. All we lack is the will and imagination to do so and the courage to talk openly about it.

MEMS based rocket arrays forming low cost highly capable propulsive skins allow the safe reliable recovery of deorbited products of space industry. Advances in this technology allow ballistic point to point transport of goods at very low cost especially if water is used as propellant and very low cost laser energy is used to energize these rockets at 1,000 sec Isp. These low cost landing systems will grow from ballistic package delivery, to ballistic personal transport, to low cost orbital access. At this point the factories, pressure vessels, farms and forests on orbit - will be joined by low cost space homes - and those space homes will become spaceships using sun orbiting laser energy to drive laser pulse rockets, and ultimately personal interstellar arks driven by laser light sails powered by sun orbiting lasers.

It a continuum we could transition to in 50 years or less. It is a continuum we could have COMPLETED by 1990 had we started when vonBraun made his recommendations to the US Army after World War 2. We took another route, and marginalized vonBraun - JFK enabled him after being embarrassed by Gagarin and the Bay of Pigs - but marginalized again by LBJ and Nixon.

We have the means, and have had the means for the past 50 years to do whatever we wanted in the solar system, and to get rich doing it. All we must do is give up a few cherished ideas that served us once, but no longer serve in the modern age.

 

[williammook]

Excellent posts, William!
I am not sure that everything will come about quite as you describe, however.

I'm pretty sure that a generationship could not be easily accelerated at 1 g using light pressure alone; light gives only a tiny amount of momentum to a sail. Generation ships would be very massive objects indeed, and would need sails so big they would tear apart at one gravity of acceleration.

Similarly a statite light collection system would be quite tricky to balance on solar light pressure while collecting power at full efficiency- unless you can find a way to make very thin, light and efficient solar cells. Perhaps one day...

Finally Bob Forward's scheme for reversing thrust on a light sail required unfeasibly focused laser beams- at that distance the beam would spread because of diffraction until it is exceedingly feeble.

To increase the momentum transferred to spacecraft of this nature you want to use particle beas rather han just light.

Thanks!

Thrust is a function of power. With total reflection it takes 150 megawatts per Newton of thrust. That's about 1.5 gigawatts per kgf of thrust - or 700 megawatts per pound force of thrust. That's where you start.

So an 8 million ton interstellar ark - the size of a super-orion - the largest spacecraft ever designed (so far) in any detail - requires 12 billion gigawatts of power to accelerate at 1 gee with light alone.

You are absolutely right about particles - but then where do you get the particles? Particles are great if you want to navigate through interplanetary space - using fusion propulsion like the Medusa - treating the reflective film now as a canopy.

The big question is, how intense can light be and not overheat the laser light sail? That depends on how reflective it is.

http://www.ecse.rpi.edu/~schubert/More- ... 20(Science)%20Giant%20birefringent%20optics%20in%20multilayer%20polymer%20mirrors.pdf

Recent advances in polymer fabrication indicate that mirrors can be made over 99.9999% efficient and be only a few microns thick! This means very high powers - very low weights. A cubic meter of polymer is about 1.25 tonnes. A micron this layer 1 meter square is 1.25 grams. A 20 micron thick layer is 25 grams per square meter.

99.9999% efficient means 1 part in 10,000 gets absorbed by the film. So, a megawatt of power per square meter of reflector means 1 watt of power is absorbed by the mirror and must be radiated as heat to the vacuum of space over 2 square meters (front and back)

This is governed by Stefan-Boltzman law

http://en.wikipedia.org/wiki/Thermal_radiation

P/A = 5.67e-8 * T^4 (watts/square meter)

Where T is the temperature in Kelvins.

1 watt per square meter = (1 / 5.67e-8) ^ (.25) = 64.8 K

Very cold!

150 Watts per square meter = 226.79 K - which is still below the freezing point of water

1500 Watts per square meter = 403.29 K - which is just above the boiling point of water - but below the melting point of polymer. PERFECT.

So, we can get between 0.1 kgf per square meter and 1.0 kgf per square meter - with modern polymer films

Now, lets look at the weight of that film - a 20 micron thick film masses 25 grams. so, this ranges from 4 gees to 40 gees acceleration - with no payload. Double the weight for rigging and so forth - and we go from 2 gees to 20 gees for a film with rigging. and we load the film up to that NET thrust ranges from 0.1 gee to 1 gee over the range of interest. This means that each square meter supports 1 kg of vehicle mass.

This means an 8 million ton vehicle requires a sail that's 8 billion square meters - about 8,000 square kilometers - operating at 150 MW to 1,500 MW per square meter - or 1.2 billion gigawatts to 12.0 billion gigawatts for the entire vehicle!!

It is interesting that a person could be accelerated at 1 gee with only 100 sq meters of film - the size of a typical parachute! A person in a stasis capsule (if such can be developed) and a highly reflective surface - can be dispatched to the stars with very little effort!

Now the light generator.

At 3 million km above the solar surface - sunlight is 2500x more instens than at Earth. 3.4 MW per square meter. That's 44 to 440 x the area of the reciever - assuming 100% efficienty. Using a GBO polymer mirror as a highly efficient optical bandpass filter - 50% efficient photocells drop to 45% efficiency, but 55% of the light is reflected away and doesn't heat the system. They are over 95% efficient - if driving a load efficiently. Even super-high efficiency free electron lasers are 90% efficient - 85.5% overall. That means that 14.5% of the energy must be radiated away as heat. This implies a temperature of 1,223 K. Well within the operating range of ceramic materials. With an overall area 100 to 1000x that of the sails they illuminate. The sail sizes might be increased in size as well, to lower their operating temperature.

Advances in microfabrication technology may permit us to sort the solar spectra and collimate beams in laser like fashion - reflecting away inefficient photons for thrust to support the film - transmitting photons of the appropriate wavelength while shifting their phase so they're all in step. This avoids the loss mechanisms involved in the process just described, makes the system more efficient, and reduces its operating altitude - all of which reduce the area of the emitter by a factor of 10 to 20. 5 to 50x the area of the receiver. And the receiver itself may be increased in size as well - to lower its temperature - as already stated.

Alright - so we have an 8,000 sq km reflective film and an 800,000 sq km transmitting film. How far can we project the beam given we want most of the energy to hit a spot 8,000 sq km in area?

This is given by the Rayleigh Criterion for optics;

A circle 800,000 sq km in area is 1,009 km in diameter
A circle 8,000 sq km in area is 100.9 km in diameter

http://en.wikipedia.org/wiki/Rayleigh_c ... xplanation

delta L = 1.220 * f * lambda / D

Using 1 micron wavelength laser, and a diam of 1,000 km - this means

delta L / f = 1.220e-12

So, if delta L is 100 km - then f = 820 trillion km. A light year is 9.47e12 km. So, this is about 86.5 light year. Since we're travelling to nearby stars no more than 10 light years away - we're golden in terms of focusing energy to wherever we want. We can also increase mirror diameter on the ship to reduce operating temperature and range - and also gain benefits like better concentrators operating farther from the sun or star on sunlight or starlight alone.

For example an 8000 sq km mirror (100 km across) on the ship can illuminate 1 square kilometer ship area to solar intensity 89.4 AU away from the sun. This is well beyond the orbit of Pluto (49.3 AU at its most distant)

The big problem isn't beam resolution - the big problem is timing. It takes 86.5 years for something done at Earth to make its way 89.5 light years away. Coordinating things will be huge logistical nightmare - unless we're clever.

We can be clever by doing things periodically - establishing standards of operation. Think of a surfer. He or she watches the waves and catches them. So, we operate our beams so that we have specific places and times to enter them and exit them - and we coordinate these times with radio telescope traffic. This creates a background traffic to keep the mechanisms of interstellar transport running smoothly. Local system traffic can operate more freely. Long distance interstellar traffic has specific times ranges payloads and so forth. And at the interface between these two systems we have way stations, where people trade shipping positions - driving the markets of entire star systems. These way stations will be bigger than New York or Tokyo, Kwoloon or Mexico City, Paris or London or Berlin.

I calculated Earlier that the entire population of Earth could be transported off system in 10 years by using only 1/500,000th of the sun's total output and 1/500,000th of the asteroid belt's mass.

I describe elsewhere how we can use technology we have available to us today, to transform life on Earth using off world resources - and create the stage for the interstellar culture our technology is capable of providing.

In the process we live the life we deserve - while freeing our biosphere from our industrial excesses. Our mines, refineries, processing centers, factories, farms, and forests are all on orbit. We live in a residential park, powered by solar pumped lasers -fed by a steady stream of materials from orbit - with only recycling present on Earth. Eventually we recycle materials to orbit, and move to orbit ourselves - visiting the vast nature preserve - tending and nurturing it - and using it to seed our growing volume of off-world stations - that then terraform worlds throughout our system, and other systems beyond the sun. A person visiting their ancestral home on Earth is wafted by MEMs based rockets powered by laser beams into orbit using his own personal spacecraft. Entering his own personal interstellar ark, accelerating by sun centered local lasers - in response to propulsive requests to move seamlessly throughout the solar system. Making his way to the entry points of light highways between the stars, radio telescope traffic with the trading desks of many worlds allow him to buy entry as he arrives at a high premium - to be dispatched to his desired star system - spending months accelerating to 1/3 light speed - then cruising for a dozen years. Spending the time in transit to learn yet another skill, and plan another interstellar campaign - and perhaps raise another child in addition to taking care of the arks systems. Arriving at the star system he then carries out his campaign - creating more value for him and his species. Learning questing developing - living.

On a scale far larger than we live at present.

 

[williammook]

I mentioned a parachute before - silver surfer may be more appropriate. Standing atop the reflective film is more efficient and keeps you out of harms way - though you would want an efficient reflective surface in any case.

With nanotech based super-reflective skin capable of supporting life in space - combined with populations of virus sized robots circulating in our bodies - fed by abundant energy tapped from propulsive lasers - our spacesuits and spacecraft may look a lot like the silver surfer

http://www.psp-themes.net/data/media/3/ ... rfer_2.jpg

The suit would provide all the materials needed by the body, take away all materials excreted by the body, all energized by laser light.. Eyes would be protected by super responsive super reflective film also capable of presenting virtual reality in transit.

1 gee acceleration gets you to the moon in hours - mars in days - across the solar system in weeks - entering the light highways between the stars at 3% light speed - out beyond Pluto deep in the Kuiper belt - to nearby stars in decades - perhaps using advanced nanotech in every cell in the body - to put the body in a medically reversible stasis - awaking for a fraction of a second periodically - giving one the illusion of moving through space at 100s of times light speed.

Bio-subjective time - is a time dilation - different than relativistic dilation - that periodically awakens and entrances a person at the cellular level - to reduce organic needs - and subjective experience of time. Awakening 1/20th of a second ever 24 hours - provides a 1.7 million to 1 speed up of experience - without any loss of awareness. So, a 10 year journey seems to take only 3 minutes bio-subjective time. Dilation can be slaved to speed so that transit times subjectively occur in minutes - and biologically too - only a few minutes of air, water, food, etc., are consumes or processed.

This is another avenue of advance that changes the nature of interplanetary and interstellar travel - and makes the energy and material needs far less than that needed in the other discussions - about 1/1000th of capital expense and 1/1,000,000,000th the recurring cost (due to bio-dilation)

 

[eburacum45]

That's really nice; with a 1000 km diameter laser you could do a lot of really interesting things. Trouble is, you want to float these collectors on light pressure alone; this limits you to 0.78 grams of mass per square metre; a bit low.

And any light you use for power is not reflected, so can't be used to support the statite. These ultra lightweight light collectors/transmitters, so close to the star, would be affected by solar wind, which is variable and would mess up any collimation you tried to acheive. In short, statite power collection is going to be inefficient and present an unstable platform for focusing light beams.

Why not use more substantial, orbiting satellites; a few thousand or million solar satellites would soon add up to the area your scheme requires, and would be a more stable base for emitting collimated beams.

One scheme I have heard for converting light beams to particle beams is to use billions of tiny light sails which themselves impact the craft to transfer momentum. The tiny sails could even have a rudimentary steering mechanism so they consistently hit the target; this means the ship doesn't need hundreds of thousands of square kilometers of reflective sail, but a much smaller pusher plate or magnetic sail.

 

[eburacum45]

A problem with using light sails at very high speeds is the interstellar medium. Once the ship has stopped accelerating the sail can be stowed away;but during the acceleration phase the sail will be impacting interstellar gas as speeds approaching 1/3 c.

We can discount the effects of dust particles, as they will pass right through, only slighly affecting the sail's reflectivity; but interstellar hydrogen will be a worse problem. It would be like firing protons at the sail for weeks on end at a respectable fraction of the speed of light - the people at Cern would be proud to acheive such a rate. Over time the very thin polymer would degrade. At the very least, this effect will place an upper bound on the final velocity - 1/3 c is probably overoptimistic using a thin sail.