Author Topic: Rapid Interstellar spaceflight, exploration and,colonization  (Read 12309 times)

Offline Fsci123

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First of all i am new to this forum so i would like to say: Hello...

I am currently designing two interstellar vessels for a simulater i am trying to make it relatively realistic... The first craft is a fully automated cargo vessel designed to be dissasembled by automata into a base once at the destination... It will travel at 0.3c... The second is crewed and a lot smaller it caries 75 crew and travels at 0.5c it too like the first vessel will be dissasembled at the destination... Both craft utilize fusion engines that require 21H+32He fuel... My main problem is figuring out how much energy would be used to accelerate the craft and for how long does this energy need to be applied... And the G forces that will be experienced on flight...

Offline khallow

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Why so fast? Why not say, 0.001C to 0.01C? Generational ships are a valid alternative here, especially if humans happen to be very long lived (given that you have "automata" remaking stuff without human input, this wouldn't be much of a stretch technology-wise).
Karl Hallowell

Offline Fsci123

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Why so fast? Why not say, 0.001C to 0.01C? Generational ships are a valid alternative here, especially if humans happen to be very long lived (given that you have "automata" remaking stuff without human input, this wouldn't be much of a stretch technology-wise).


By time such a craft may arrive at its destination we may have either gone extinct or killed eachother off or developed better technology to get their at speeds of .999c so... Pretty good waste of time and money there... ???

Offline aceshigh

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accelerate your craft at constant 1G. That will provide artificial gravity inside the ship and reach 99% of light speed in a few months.

just use MS Excel... 1G = 9,8 m/s².

at the end of the first second, the speed is 9,8m/s
at the end of the second second, the speed is 19,6 m/s

on another column, translate that speed to km/s

finally, multiply 9,8 *60 to get what speed in m/s the ship will reach in one minute. That result * 60 will tell the speed after one hour. That result vs 24 will tell the speed after one full day of acceleration. That result vs x will tell the speed after x days of acceleration. Make X so that your speed get as close but of course, doesnt go beyond 300.000 km/s (or 300.000.000 m/s)


Btw, I dont think its possible to tell you how much energy is needed to accelerate the craft unless you tell us its mass and how efficient the fusion engines are.

Offline QuantumG

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just use MS Excel... 1G = 9,8 m/s².

at the end of the first second, the speed is 9,8m/s
at the end of the second second, the speed is 19,6 m/s

on another column, translate that speed to km/s

For people who can't do algebra.
Human spaceflight is basically just LARPing now.

Offline Fsci123

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1.261×10^11 grams

Offline alexw

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1.261×10^11 grams
    To four significant figures??

Offline alexterrell

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This is how I learnt it at school, and these equations are ingrained:
v = u + at
v^2 = u^2 + 2as
s = ut + 1/2 at^2

and E = 1/2mv^2

v = end velocity, u = start velocity, a = acceleration, s = distance, E = energy.

You also need to account for increase in mass at you approach c
http://en.wikipedia.org/wiki/Mass_in_special_relativity

It is quite amazing how much energy you need to accelerate a large ship to >0.1c. A 1000t cargo craft at 0.3c needs 9E21 Joules (neglecting relativistic mass). That's Earth's current electricity output (2 TW?)  for 142 years. 


Offline khallow

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Why so fast? Why not say, 0.001C to 0.01C? Generational ships are a valid alternative here, especially if humans happen to be very long lived (given that you have "automata" remaking stuff without human input, this wouldn't be much of a stretch technology-wise).


By time such a craft may arrive at its destination we may have either gone extinct or killed eachother off or developed better technology to get their at speeds of .999c so... Pretty good waste of time and money there... ???

If you're racing to get somewhere first, then just send a payload of a few grams of those "automata" at high speed and forget the rest. There's a vast energy cost to moving a significant fraction of the speed of light. Else, if you just want to get there and aren't worried about being first, then the slower speed is much more affordable.
Karl Hallowell

Offline Fsci123

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I recalculated the mass and it comes out to: 4.26127×10^7 kg

Offline baldusi

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There's the problem of shielding for gamma rays (at .1c everything is high energy), and to slow down. Unless you want keep going forever you should be able to slow down. Use the rocket's formula.

Offline aceshigh

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Why so fast? Why not say, 0.001C to 0.01C? Generational ships are a valid alternative here, especially if humans happen to be very long lived (given that you have "automata" remaking stuff without human input, this wouldn't be much of a stretch technology-wise).


By time such a craft may arrive at its destination we may have either gone extinct or killed eachother off or developed better technology to get their at speeds of .999c so... Pretty good waste of time and money there... ???

If you're racing to get somewhere first, then just send a payload of a few grams of those "automata" at high speed and forget the rest. There's a vast energy cost to moving a significant fraction of the speed of light. Else, if you just want to get there and aren't worried about being first, then the slower speed is much more affordable.


not exactly a race... but it will just HAPPEN that if you have a slowboat, by the dozens of years (even generations) that will take to reach your destiny, humanity technology will have evolved enough to reach there faster. So any travel that takes "generations" is quite useless imho.

Offline DarkenedOne

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Why so fast? Why not say, 0.001C to 0.01C? Generational ships are a valid alternative here, especially if humans happen to be very long lived (given that you have "automata" remaking stuff without human input, this wouldn't be much of a stretch technology-wise).


By time such a craft may arrive at its destination we may have either gone extinct or killed eachother off or developed better technology to get their at speeds of .999c so... Pretty good waste of time and money there... ???

If you're racing to get somewhere first, then just send a payload of a few grams of those "automata" at high speed and forget the rest. There's a vast energy cost to moving a significant fraction of the speed of light. Else, if you just want to get there and aren't worried about being first, then the slower speed is much more affordable.


not exactly a race... but it will just HAPPEN that if you have a slowboat, by the dozens of years (even generations) that will take to reach your destiny, humanity technology will have evolved enough to reach there faster. So any travel that takes "generations" is quite useless imho.

Technology eventually reaches its limits.  One cannot simply assume that in a generation or two technology would of improved significantly.

Offline Patchouli

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Why so fast? Why not say, 0.001C to 0.01C? Generational ships are a valid alternative here, especially if humans happen to be very long lived (given that you have "automata" remaking stuff without human input, this wouldn't be much of a stretch technology-wise).


By time such a craft may arrive at its destination we may have either gone extinct or killed eachother off or developed better technology to get their at speeds of .999c so... Pretty good waste of time and money there... ???

If you're racing to get somewhere first, then just send a payload of a few grams of those "automata" at high speed and forget the rest. There's a vast energy cost to moving a significant fraction of the speed of light. Else, if you just want to get there and aren't worried about being first, then the slower speed is much more affordable.


not exactly a race... but it will just HAPPEN that if you have a slowboat, by the dozens of years (even generations) that will take to reach your destiny, humanity technology will have evolved enough to reach there faster. So any travel that takes "generations" is quite useless imho.

Technology eventually reaches its limits.  One cannot simply assume that in a generation or two technology would of improved significantly.

A slow boat ship will almost certainly be beat by a faster ship launched later.

I can think of a few ways to over come some of the limitations described as insurmountable.

First combine methods of propulsion.

Here is how I'd go about the problem.

For the out bound part near the solar system a laser or mag would be used as shown in the movie Avatar.

For cruise use a Bussard ramjet enhanced with antimatter.

Even without antimatter and break even fusion it could make a useful brake and maybe even top off the propellant tanks for fusion rockets.
http://en.wikipedia.org/wiki/Bussard_ramjet


Breaking the Bussard scoop could be expanded and hydrogen strored vs burned or a solar sail deployed the star at the destination will have solar wind.
Then use standard fusion or antimatter rockets for the finial breaking.

I think if the technology is refined enough a cruise speed of .20 to .80 c depending on beam power and if you have antimatter should be possible.

Besides there is no need at all to ever go so slow even today.
Pulsed fusion technology onlya a little far out can reach 12% c.
http://en.wikipedia.org/wiki/Project_Daedalus

Heck even ol Bang Bang something we could build today if we had to can do a lot better then 0.01c.
An atomic Orion can do 3 to 5% c a fusion Orion 8 to 10% c.
http://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propulsion%29
« Last Edit: 05/18/2011 03:46 am by Patchouli »

Offline khallow

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not exactly a race... but it will just HAPPEN that if you have a slowboat, by the dozens of years (even generations) that will take to reach your destiny, humanity technology will have evolved enough to reach there faster. So any travel that takes "generations" is quite useless imho.


Sure, it'll be something of a gamble. But building the infrastructure to power a vehicle to a significant fraction of the speed of light is not trivial. For example, suppose I'm racing a future vehicle of the sort described in the first post, a 75 man vehicle that travels at 0.5C. Let's suppose that due to marvels of technology, this vehicle only weighs 100 tonnes per person for a total payload mass of 7500 tons. You still have to convert to energy, roughly 1200 tonnes. This would be over 20 trillion tonnes of TNT equivalent.

If you had 600 tonnes of antimatter and perfect conversion into velocity, then that'd be good enough. If you were doing it with a perfect deuterium reactor, you'd have to have at least 16,000 tonnes of deuterium (roughly 7% mass to energy conversion during fusion). That's just to service the energy requirement of the payload's velocity! For He3, you'd need somewhat more mass, because it has lower mass fraction to energy conversion.

I haven't even touched the rocket equation. Nor have I decelerated my vehicle. But 0.5C already looks ridiculously expensive for what you get.

And what does happen to my generational ship, if someone gets there first? Well, if I arrive within a few centuries to a few millennia, there's still probably a lot of good real estate to choose from. If someone used von Neumann machines to transform the system quickly or bred billions of people from vats, well, they might have done that anyway, if I had arrived first. It's hard to defend yourself against vastly superior firepower when you have delicate infrastructure. A budding colony, or generational spaceships isn't going to make much difference.

The point is that generational ships have vastly lower energy costs due to the much slower speed. While they need to be designed to weather centuries or millennia in space, any colony that the fast people build would probably need to be pretty well engineered too.
Karl Hallowell

Offline aceshigh

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the point is... if you cant do fast enough, for economics or technology, just dont do it.

better wait until you develop the tech. Hopefully, something like Woodwards Mach Drive :)
« Last Edit: 05/18/2011 03:12 pm by aceshigh »

Offline Tass

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And what does happen to my generational ship, if someone gets there first? Well, if I arrive within a few centuries to a few millennia, there's still probably a lot of good real estate to choose from.

Why'd you need "real estate" at that tech level at all? A generation ship is already a self supporting space habitat. All you'd need is sunlight and materials for expansion. And there is enough of that in a solar system for quadrillions of humans. Taking a few hundred years will be no problem at all for the first interstellar flights because even if someone beat them there by a hundred years it will take something like 30 doublings to use up the readily available resources, and even with extreme economic and population growth thirty doublings take some time.

Of course, eventually exponential growth does defeat the growth of reachable resources which must necessarily be cubic. So I expect in the end, the edge of civilizations bubble of influence will actually be made up of exceedingly expensive ships doing significant fractions of c. But for the first adventurous interstellar flights, before we are even done constructing the Dyson swarm at our own solar system, no worries. There will be plenty of resources left where ever you go. There will be resources at home too, but that won't stop some from expanding for expansions sake.   

Offline khallow

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...there's still probably a lot of good real estate to choose from.

Why'd you need "real estate" at that tech level at all? A generation ship is already a self supporting space habitat. All you'd need is sunlight and materials for expansion.

Note what I bolded above. Currently, humanity needs a broad spectrum of elements and materials for themselves and their technology. They also need some sort of power such as fairly intense star light. So where can you get both? That restricts your choices.

Suppose such a ship arrived now in the Solar System. There aren't that many places with both of the above mentioned resources. Earth is by far the best place, even restricting our attention to just the combination of solar power and broad element coverage and availability. No closer place to the Sun has broad element coverage. Mars has decent coverage, but half the solar intensity of Earth. Venus could be terraformed into a better choice, but it currently is limited in resources. The asteroids look pretty good, but they for the most part have even lower light intensity than Mars (there are closer asteroids, but they suffer from low volatiles).

The colonists could disperse to multiple locations across the star system, but it seems a bit risky unless there's some redundancy in the supply of materials.

There are sites which are clearly better than others and it makes sense that if someone gets there earlier (especially centuries earlier), then the choice of location will be narrowed to some degree.
Karl Hallowell

Offline Tass

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The asteroids look pretty good, but they for the most part have even lower light intensity than Mars

So? Just move stuff. The delta-v is less than for escaping from earth, and you are even able to use electric propulsion because of low gravity fields. The gravity well of a big planet is a big disadvantage.

Besides light can be concentrated. When you have this amount of technology and space based industry then it is not that big of a problem.

Thirdly if fusion power has been well developed (not such a big stretch) then you only really need a star because other objects tend to gather around it and are easier to find there. Inner Oort cloud might actually be the place to go in that case.

Offline QuantumG

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Read Larry Niven's "Protector".

Human spaceflight is basically just LARPing now.

Offline Hop_David

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The asteroids look pretty good, but they for the most part have even lower light intensity than Mars

So? Just move stuff. The delta-v is less than for escaping from earth, and you are even able to use electric propulsion because of low gravity fields. The gravity well of a big planet is a big disadvantage.

Besides light can be concentrated. When you have this amount of technology and space based industry then it is not that big of a problem.

Indeed, big enough parabolic mirrors and the "edge of sunlight" gets pushed back.

Mike Combs took this idea and ran with it in this story:
Eyes, Shining Back from the Dark.

Offline Patchouli

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The asteroids look pretty good, but they for the most part have even lower light intensity than Mars

So? Just move stuff. The delta-v is less than for escaping from earth, and you are even able to use electric propulsion because of low gravity fields. The gravity well of a big planet is a big disadvantage.

Besides light can be concentrated. When you have this amount of technology and space based industry then it is not that big of a problem.

Indeed, big enough parabolic mirrors and the "edge of sunlight" gets pushed back.

Mike Combs took this idea and ran with it in this story:
Eyes, Shining Back from the Dark.

Once you have controlled fusion you don't even need the mirror to live out that far.

A civilization that's fully adopted to deep space could in theory live in the back yard of one that lives on planets.

Though I think they might seek out M class stars vs G class stars.

« Last Edit: 05/20/2011 04:10 am by Patchouli »

Offline khallow

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Heh, now I'm in error in a way that supports my original argument. Wish that would happen more often.

Even if someone beats you first to a star system, you still can find a niche. There's probably some advantage to being the first to a new star system, but I think it's overstated.
Karl Hallowell

Offline KelvinZero

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Heh, now I'm in error in a way that supports my original argument. Wish that would happen more often.

Even if someone beats you first to a star system, you still can find a niche. There's probably some advantage to being the first to a new star system, but I think it's overstated.

A point for and against,
With a thousand year difference, if you travelled incommunicado, you would be at best a boatload of vikings arriving in america 2010. A niche would certainly be provided I expect, but not found unclaimed. I actually expect that the next thousand years will change us much more significantly than the last, because AI and genetic engineering are very likely to be mastered IMO.

On the other hand perhaps a generational ship does not ever need to leave human civilisation. It could still be only a few years behind modern developments, and since it presumably has the engineering capability to manufacture/recycle its own parts it will probably be able to produce anythng it has the plans for.

Because it is still part of human civilisation the crew members could still be managing investments on and off the ship, and through speculation could own assets on the destination even if they arrive much later.

My personal feeling is that once we can master living on an icy low gravity rock they will quickly become more relevant than earthlike worlds with their high gravity wells and atmospheres that make magnetic launch impractical.
I like the idea that has been thrown around a few times that we should aim for a certain timespan eg a decade or a generation, and simply make missions to objects that we can reach in that timescale with current technology. Before we send missions to other stars we can first have missions to kupier belt objects, then to rogue planets and so on. It may even be one of these worlds that sends the first true interstellar colony.

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