Colonized Interstellar Vessel: Conceptual Master Planning

Void · 2014-06-07 17:09:41

That may be all that there is, and really I do not want to sidetrack you away from what you are speculating on.

However, what if humans could live indefinitely? That might change the plans in some cases.

http://www.sens.org/

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

http://www.youtube.com/watch?v=qMAwnA5WvLc

This is part of why I reccommend converting a comet around Sol in it's Oort cloud, to a hollow world as part of a mission to Alpha Centauri. It could prove true that some who did that work would still be alive to do it again for a comet around Alpha Centauri, if it has comets, which I would have to guess it might.

There are also "Brain in a bottle" with a new body later plans, and also multi-genomic organisms which upon seeding an ocean would progressively give birth to higher and higher organisms until humanoids. (With no oxygen, they would have to breath blood from plants which would supply it, a symbiosis of humanoid and plant). Massive genetic engineerin required for that, far beyond us at this time.

My nerd time for the weekend is probabbly exhausted, talk to you later.

JoshNH4H · 2014-06-07 17:43:47

Hey Void,

It's no trouble at all, and I am always glad to see your responses. I certainly have made errors with my physics and math in the past, and certainly will again. I won't lie and say I'm an agreeable person; I think that there are many on this board who would agree that I am argumentative, at times to a fault

I was surprised that the sail mass is as high as 5 g/m^2, but comparing to the Sunjammer is 25 g/m^2, so I suppose that actually represents a significant improvement.

The first thing I'll do is to show my logic for the number as I presented it.

The parameters of note are:

Power of the Sun (P): 3.86e26 W
Assumed mass of the craft (m/A): .010 kg/m^2 (10 g/m^2, 5 g/m^2 of sail and an equal mass of sail and payload)
Speed of light (c): 299,792,458 m/s
Starting radius (r1): 30,000,000,000 m (.2 AU)

From physics:

integral[F*dr]=1/2*m*v^2

F is Force
r is radius (and dr is the infinitesimal difference in radius)
m is total mass of the craft
v is the velocity of the craft at infinity

The integral should be evaluated from the starting point to infinity.

On the left is the definition of work, and on the right is the equation for kinetic energy. I assumed that gravitational effects, both from the speed of the orbit and the gravitational attraction of the Sun are negligible, because if the solar sail is going to provide a meaningful portion of the velocity required to get to another star they would have to be.

Force from light impinging on an area and then being reflected perfectly by a sail is:

F=2*(P/4*pi*r^2)*A/c

Where the term in parentheses represents the insolation (W/m^2) at radius r from the Sun.

Therefore we have:

integral[2*(P/4*pi*r^2)*A/c*dr]=1/2*m*v^2

Extracting constants from the integral and reorganizing:

v^2=P/(pi*c)*(A/m)*integral[dr/r^2]

Where:

integral[dr/r^2]=-1/r

Evaluating as I said I would:

integral[dr/r^2]=1/r1

So, we have:

v^2=P/(pi*c*r1)*(A/m)

Plugging in I calculate a velocity at infinity of 37 km/s, the same as I calculated originally (I'll admit, I rounded down unnecessarily to make a point). This should not be regarded as a precise figure but an order of magnitude estimate; The escape velocity of the Sun at .2 AU is much higher than this. For a sail in orbit I don't know how much difference this will make, but it becomes a difficult to calculate kinematic question.

The nearest star is 4.22 light-years away, or about 4e16 m away. At 37 km/s, this would take about 34,000 years; If the sail and ship mass combined were reduced to 1 g/m^2, the speed would increase to 117 km/s and the journey time would fall to about 11,000 years. The radius of the Sun is about 700,000 km. Let's say that instead of leaving from 30,000,000 km (43 solar radii) we leave from 1,400,000 km (2 solar radii). This increases the speed to 541 km/s and the trip time falls to 2300 years. If you drop the mass of the craft by another factor of 10, the speed will rise to 1,711 km/s, and the trip time will fall to 740 years.

So, yes: Using an obscenely lightweight sail unfurled obscenely close to the Sun, you can technically achieve interstellar transit times under a thousand years. NASA's Advanced Concepts Office (Take note of who's doing these calculations, by the way... NASA's Advanced Concepts Office studies just that: Advanced Concepts, not necessarily practical designs) probably used a model which took gravitational effects into account, and this may or may not have made it easier to achieve these trips. But I don't think we're necessarily in disagreement here.

Lasers make this easier, of course. But propulsion with a lightsail is actually very inefficient because most of the energy of the light is reflected. For example, to accelerate the 250,000 tonne ship I mentioned in my previous post to 1% of the speed of light over one hundred years would use a laser power of 2e13 W; Given a high-end laser efficiency of 10%, that's 2e14 W, which is about ten times the power currently used by all of humanity put together. Concentrated sunpower might be a better solution, but even that is a pretty tough one.

This isn't the only poorly thought out but popular propulsion system. Look at all the people who think VASIMR could be used to move people!

Void · 2014-06-09 10:09:08

Obviously, a profit is required to a budget of money or meat and vegetables, but lacking the ability to adapt is typically a dead end eventually.
Zero percent efficiency is useless to us. However we know that a generator cannot be 100% efficient, it is necessary for some energy to pass into the universe, heat dispersed to an increasing volume, a falling background temperature.
Both the sun and Hydrogen bombs are fusion reactions. So a solar sail is a part of a fusion drive, a partially natural (We did not build it) drive.
The fact that solar sails might be 10% efficient is not necessarily important. If they were 0% efficient, or near 0% they would be a complete waste of time.
I must wonder how efficient is a nuclear bomb is in transferring it’s energy to an Orion Propulsion unit. It does not matter that much
I think that both you and I have a hard time imagining a completely Solar/Laser driven interstellar mission. My hope is that to satisfy various useful purposes, Solar/Laser can be a component, and the Orion another, and magnetic braking another.
I see something in your post that I do not understand (Other than the complex equations)
Quote: "The escape velocity of the Sun at .2 AU is much higher than this".
http://en.wikipedia.org/wiki/Oort_cloud

The Oort cloud (/ˈɔrt/ or /ˈʊərt/;[1]) or Öpik–Oort cloud,[2] named after Dutch astronomer Jan Oort, is a spherical cloud of predominantly icy planetesimals believed to surround the Sun at up to 50,000 AU.[3] This places the cloud a quarter of the distance to Proxima Centauri, the nearest star to the Sun. The Kuiper belt and the scattered disc, the other two reservoirs of trans-Neptunian objects are less than one thousandth of the distance. The outer limit of the Oort cloud defines the cosmographical boundary of the Solar System and the region of the Sun's gravitational dominance.[4]
The Oort cloud is thought to comprise two regions: a spherical outer Oort cloud and a disc-shaped inner Oort cloud, or Hills cloud. Objects in the Oort cloud are largely composed of ices, such as water, ammonia, and methane.
Astronomers conjecture that the matter composing the Oort cloud formed closer to the Sun and was scattered far into space by the gravitational effects of the giant planets early in the Solar System's evolution.[3] Although no confirmed direct observations of the Oort cloud are made, it may be the source of all long-period and Halley-type comets entering the inner Solar System, and many of the centaurs and Jupiter-family comets as well.[5] The outer Oort cloud is only loosely bound to the Solar System, and thus is easily affected by the gravitational pull both of passing stars and of the Milky Way itself. These forces occasionally dislodge comets from their orbits within the cloud and send them towards the inner Solar System.[3] Based on their orbits, most of the short-period comets may come from the scattered disc, but some may still have originated from the Oort cloud.
Structure and composition[edit]
The Oort cloud is thought to occupy a vast space from somewhere between 2,000 and 5,000 AU (0.03 and 0.08 ly)[9] to as far as 50,000 AU (0.79 ly)[3] from the Sun. Some estimates place the outer edge at between 100,000 and 200,000 AU (1.58 and 3.16 ly).[9] The region can be subdivided into a spherical outer Oort cloud of 20,000–50,000 AU (0.32–0.79 ly), and a doughnut-shaped inner Oort cloud of 2,000–20,000 AU (0.03–0.32 ly). The outer cloud is only weakly bound to the Sun and supplies the long-period (and possibly Halley-type) comets to inside the orbit of Neptune.[3] The inner Oort cloud is also known as the Hills cloud, named after J. G. Hills, who proposed its existence in 1981.[10] Models predict that the inner cloud should have tens or hundreds of times as many cometary nuclei as the outer halo;[10][11][12] it is seen as a possible source of new comets to resupply the tenuous outer cloud as the latter's numbers are gradually depleted. The Hills cloud explains the continued existence of the Oort cloud after billions of years.[13]
The outer Oort cloud may have trillions of objects larger than 1 km (0.62 mi),[3] and billions with absolute magnitudes[14] brighter than 11 (corresponding to approximately 20-kilometre (12 mi) diameter), with neighboring objects tens of millions of kilometres apart.[5][15] Its total mass is not known, but, assuming that Halley's Comet is a suitable prototype for comets within the outer Oort cloud, roughly the combined mass is 3×1025 kilograms (6.6×1025 pounds), or five times the Earth.[3][16] Earlier it was thought to be more massive (up to 380 Earth masses),[17] but improved knowledge of the size distribution of long-period comets led to lower estimates. The mass of the inner Oort Cloud has not been characterized.
If analyses of comets are representative of the whole, the vast majority of Oort-cloud objects consist of ices such as water, methane, ethane, carbon monoxide and hydrogen cyanide.[18] However, the discovery of the object 1996 PW, an asteroid in an orbit more typical of a long-period comet, suggests that the cloud may also contain rocky objects.[19] Analysis of the carbon and nitrogen isotope ratios in both the long-period and Jupiter-family comets shows little difference between the two, despite their presumably vastly separate regions of origin. This suggests that both originated from the original protosolar cloud,[20] a conclusion also supported by studies of granular size in Oort-cloud comets[21] and by the recent impact study of Jupiter-family comet Tempel 1.[22]
[

The Oort cloud perhaps having billions of suitable objects in it may have an edge of 50,000 or more AU. Perhaps we are corresponding but not communicating well, lacking a common understanding.
There are probably two speed limits of Solar/Laser. One is tied to the amount of energy the sail receives, the other is the amount of energy the sail can receive without being destroyed.
The one trick I am happy with is that if you could propel a sail with payload to an Oort cloud object you have options for what to do with the retained sail materials. You can use the materials to make a base on/in the comet, or you can use some of it to further outfit your interstellar mission.
In it's best case such a comet could be poised 1/4 the distance to the next star. It could be hoped that star had a similar configuration and might have an Oort cloud out 1 light year. So your interstellar mission in a best case might be a 2.4 light year crossing, not 4.4 light years. This along with the life extension mentioned previously will make it more probable that a person might launch on a mission from one solar comet to an alien comet and live to reach the alien comet and build a habit on it or around it.
Selected objects in an Oort cloud might be in elliptical orbits. Doing magnetic braking, I would expect a starship to enter an alien stars sphere of influence in an elliptical orbit. It most likely will have exhausted much of its reserves, and will need an easy target, one that would not require powerful landing craft. An ideal sized comet in an elliptical orbit might do for that.
While you might choose to use an Orion fusion bomb drive to travel a full 4.4 light years, it is apparent to me that you must increase its mass pyramid, in order to function, and it will not leave behind any mass on the Solar Oort cloud comet with which to kindle a civilization.
I see better value in a combined method.
Obviously I am cutting the interstellar trip into pieces. Mars or Titan to Oort, Cross from Sol(Oort) to Alien(Oort), eventually access the entire alien system from the base in the Alien(Oort) object.
Non-Bomb fusion power would or another real power source would have to exist at the comets. Otherwise it cannot be a good plan.
I will seek to understand the communications in your equations, you already know that is not how I do my thinking for the most part.

JoshNH4H · 2014-06-09 10:34:00

Actually, the efficiency to which I refer is the electric-to-light efficiency of the laser, not that of the propulsion. As I said, propulsion using lightsails is typically very low efficiency. The efficiency of light sail propulsion can be said to be equal to the rate of change of kinetic energy divided by the light power applied to the craft.

Rate of change of kinetic energy:

d/dt(KE)=d/dt(1/2*m*v^2)=m/2*d/dt(v^2)=m*v*a (chain rule)

Where a=F/m (Newton's Second Law)

d/dt(KE)=F*v

From my previous post,

F=2*P/c

Where P in this case is the power of the light incident on the craft. We have:

d/dt(KE)=2*P*v/c

And the efficiency (n) is equal to:

n=d/dt(KE)/P=2*P*v/c*1/P

n=2*v/c

This equation does not take into account relativity, so in reality the efficiency is never greater than 1.

The light power-to-kinetic-energy efficiency of the craft accelerating up to 3% the speed of light will top out at 6%. The efficiency over the course of the flight will be lower than this because the acceleration phase will mostly occur when the speed is less than the top speed.

My guess (and it is just that) is that an Orion propulsion system would have an efficiency of maybe 25-50% in getting the energy of the bomb into the craft; But beyond this high powered bombs are quite easy to build, we've done it an unfortunate number of times already in our history.

The Oort cloud is a nice place to stop by and refuel. I would think that it should be inhabited before we start seriously thinking about taking thousands of years to go to other star systems. It is quite far, so the technologies used to get there make good beginnings. By that time we may even be able to make a star of sorts to heat up these worlds and terraform them, or just to generate energy.

Void · 2014-06-09 13:59:23

Wow! We agree on something and arn't pressing the red button on anything else!

Some speculation has it that there could be Mars sized worlds, but another person on this board has pointed out that a non-defferentiated smaller body might be preferable.

For the Oort cloud I tend to hope for a right size world which could be hollowed out and held together with gravitation, and have null gravitation in the center of the hollow, where indeed structures as have been discussed and proposed could host humans in happy fashion.

Fusion power will be needed though, or something as good.

Void · 2014-06-09 16:33:58

After considering your arguments . I'm I yield to a large degree . if an Orion ship uses hydrogen bombs . Sequential refueling makes sense. I will still say that solar sails sent to oort cloud objects and recycled there may be of benefit, if it can be accomplished. But not to tow a large payload.

Last edited by Void (2014-06-09 16:48:41)

JoshNH4H · 2014-06-09 16:41:21

It had to happen eventually

Oort cloud bodies make a tremendous stepping stone to other solar systems, nearly halving the required distance. And I can't help but imagine that sky surveys will show the existence of some rogue planets out there which we will be able to use as stepping stones. From a colonization perspective, these are really no worse than Oort cloud bodies, and perhaps better, seeing as they stand a better chance of being rocky.

People are always so down on fission. Why? It's a great technology, and fusion is so hard to do.

GW Johnson · 2014-06-09 17:06:46

A properly-designed Orion propulsion system uses nuclear devices that are shaped charges. You want essentially all the released energy to go into a spindle-shaped pair of oppositely-directed spikes, as collimated as possible. With a fission device, this is all about the design of the neutron reflector wrapped around the device. With fusion, I dunno. Maybe no one does. You'd have to ask the weapons lab guys this question.

Your pusher plate intercepts the spike pointed at the ship, so yes, control of bomb orientation is quite crucial. If the pusher plate intercepts the full spike, the energy efficiency is 50%, which is the maximum. Intercept less, your energy efficiency is lower. How "spiky" is your shaped charge, how much is in each spike, how big is your pusher plate relative to the spike that hits you as it arrives? Those are the questions that determine your real efficiency.

GW

Terraformer · 2014-06-09 17:08:05

Josh, have you read Lockstep, by Karl Schroeder? It's set on rogue planets, which hibernate every month for 30 years to allow them to keep a civilisation together using fairly slow (for a starship..!) travel...

Though, if we've colonised the Oort cloud, it's pretty much a given that we have fusion. Perhaps, with torchships, trade could be sustained between colonies that are less than a couple of light months apart?

JoshNH4H · 2014-06-09 17:34:47

GW, as I understand it it is also possible to increase the propulsive efficiency of the Orion system simply by locating more mass at the two "poles" of the system than elsewhere.

Terraformer, I have not but that sounds quite interesting. And I don't know if I would say that it's a given that we have fusion. One could envision the use of Orion style propulsive systems, or Nuclear Salt Water Rockets.

I don't doubt that trade can be sustained over long distances, for some items, but it's worht asking what those items would be that make it worth it. What does one ball of ice and rock have that's worth sending to a different ball of ice and rock?

Terraformer · 2014-06-10 05:56:51

Luxury items, people, microchips if we can't afford to put a chip fab in a colony of a few thousand people...

Unless you intend to run your civilisation on starlight, I imagine you'd have fusion. On the plus side, achieving a very high grade vacuum in space isn't difficult, and in the absence of gravity, we should be able to build quite large reactors. 100m diameter polywells, perhaps?

Tom Kalbfus · 2014-06-10 07:53:53

JoshNH4H wrote:

...
The Oort cloud is a nice place to stop by and refuel. I would think that it should be inhabited before we start seriously thinking about taking thousands of years to go to other star systems. It is quite far, so the technologies used to get there make good beginnings. By that time we may even be able to make a star of sorts to heat up these worlds and terraform them, or just to generate energy.

The problem with stopping is that it takes more bombs to stop.

Here is a Daedalus Starship

Daedalus according to the original concept was supposed to reach 12.5% of the speed of light in these two stages on a one-way fly through mission. Another use for such a vehicle would be as a cargo ship for a generation ship. Now the CIV according the the illustration uses the bottom stage of this vehicle, so the bottom stage is capable or reaching 6.25% of the speed of light, and assume the CIV has the same mass as the upper stage of the unmanned probe, that means a generation ship could reach 6.25% of the speed of light and have no way to slow down once it reaches the system. Since they'll want to slow down and it uses the bottom stage only both for acceleration and deceleration their top speed is going to be 3.125% of the speed of light. Now if we can build this starship (the CIV) we can also build a Daedalus Star Probe as in the above illustration. This Daedalus can reach 6.25% of the speed of light and if we launched it for instance 20 years into the CIV's trip, it would catch up with the CIV in 40 years after its launch, at which point the upper stage would separate from the lower stage and slow down to 3.125% of the speed of light, and the fuel it would have use to slow down completely can otherwise be used as additional cargo space for resupply 40 years into the mission. The Daedalus is then discarded since it is out of fuel.

I think two resupply probes can visit the CIV at around 1/3rd and 2/3rd of is mission. At 3.125% of light speed it takes 140.8 years to reach Alpha Centauri, that means it can receive a resupply probe 46.94 years into its mission and one 93.87 years into its mission. Since the Daedalus travels twice as fast it can cover twice the distance as the CIV at a given amount of time. So if we launch the first Daedalus Resupply Ship 23.47 years into he mission, it will travel twice the distance in 23.47 years as the CIV traveled in the previous 23.47 years so it catches up 46.94 years into the mission, the second Daedalus probe is launched 46.94 years into the mission and traveling twice that distance in the next 46.94 years, it reaches the CIV in 93.87 years, its possible to do one more resupply a third Daedalus can be launched almost halfway into the mission about 70.4 years into the mission, it catches up with the CIV just before it begins to slow down into the Alpha Centauri System, some supplies are offloaded into the CIV, and unneeded garbage is dumped into space to minimize mass and the whole CIV slows down into the system. Resupply intervals are 46.94 years, 93.87 years and 140.8 years, it one likes another resupply ship could be launched could arrive 46.94 years after the colonists have arrived in system, it travels at 3.125% of the speed of light and is launched at the same time as the second resupply ship, since it doesn't travel as fast it can carry a payload equal to the first CIV, the payload could even be another CIV to take care of an expanding population within the system, so it would be launched unmanned.
The same principle would apply to Orion type hydrogen bomb starships, only that the resupply ships would have to be much larger to take advantage o fusion's greater energy.

Last edited by Tom Kalbfus (2014-06-10 07:56:35)

Void · 2014-06-10 08:10:45

Terraformer,
Do your calculations suppose a full trip of 4.4 lightyears, or a more optimistic "Best Case" of 2.4 light years starting at a Oort cloud object around our sun, and ending at a eliptical object orbiting Alpha Centauri?

Terraformer · 2014-06-10 08:26:06

What calculations...?

If you're talking about my comment re. trade, I'm talking about trade between objects that are only a few light months apart at most. Which would mean a one way trip would take over a year, unless you're willing to breathe liquid for a few weeks at each end and travel at high relativistic velocities... as well as having a sufficiently powerful beam to push you like that. Plus the extra week it takes you to transfer to the planet after arrival, because I'm sure people won't want to let WMDs come within a few light hours of the planet, with lasers on standby to destroy anyone who does...

Which reminds me of the Centauri Dreams post on an interstellar railroad, consisting of beam stations along the route to allow very high speed travel.

Void · 2014-06-10 08:53:32

Your schedule for resupply ships.

Terraformer · 2014-06-10 09:01:49

What? That's Tom...

JoshNH4H · 2014-06-10 09:32:30

While there may not be as many metallic elements, or the same quantity of them, in the Oort cloud, I'm sure there will still be enough Uranium to provide for a good amount of power if we need it.

The problem with fusion, IMO, is that it's not an incremental jump in technology but rather represents technologies totally unlike any that have come before. It's not impossible, but it is surely more difficult. Fusion is obviously possible, and will probably have been perfected by the time we get to the Oort cloud, but it never hurts to remember that Fission is still a viable option.

But then, I'm still holding out that NILFr ends up as a moneymaker...

Tom, the idea is that rather than going straight from colonizing the inner system to colonizing new solar systems, we expand gracefully and then launch a mission only when we've already developed to the outer edge of this solar system. Then we colonize on, perhaps making waystations in interstellar space, and go from there. It might take longer, even twice as long, or three times as long, but it's much less strenuous on any given person.

Void · 2014-06-10 10:09:49

What? That's Tom...

oops! Well you all look alike to me

Terraformer · 2014-06-10 10:11:57

Uranium needs to be concentrated into useful ores in order to really be useful. You're talking about processing entire kilometer wide comets to get a tonne of uranium (according to either Islands In The Sky or Entering Space...).

However, there's always the possibility of worlds with geothermally heated oceans, if large enough.

Void · 2014-06-10 10:14:03

The problem with fusion, IMO, is that it's not an incremental jump in technology but rather represents technologies totally unlike any that have come before. It's not impossible, but it is surely more difficult. Fusion is obviously possible, and will probably have been perfected by the time we get to the Oort cloud, but it never hurts to remember that Fission is still a viable option.

So try both, settle for less if you have to.

Helium 3 from the Moon, enriched heavy Hydrogen from Mars. I believe that there is a greater percentage of it in the water of Mars than Earth.

I think Helium 3 makes a cleaner (Radiation) explosion. At a lower temperature as well? The benefits of Helium 3 for bombs seems ambiguious to me, but its worth thinking about.
http://en.wikipedia.org/wiki/Helium-3#E … _abundance
A more standard fuel would likely be better, if you wanted to refuel periodically while moving from the inner solar system to the Oort cloud.

Last edited by Void (2014-06-10 10:21:42)

Tom Kalbfus · 2014-06-10 11:29:55

JoshNH4H wrote:

While there may not be as many metallic elements, or the same quantity of them, in the Oort cloud, I'm sure there will still be enough Uranium to provide for a good amount of power if we need it.
The problem with fusion, IMO, is that it's not an incremental jump in technology but rather represents technologies totally unlike any that have come before. It's not impossible, but it is surely more difficult. Fusion is obviously possible, and will probably have been perfected by the time we get to the Oort cloud, but it never hurts to remember that Fission is still a viable option.
But then, I'm still holding out that NILFr ends up as a moneymaker...
Tom, the idea is that rather than going straight from colonizing the inner system to colonizing new solar systems, we expand gracefully and then launch a mission only when we've already developed to the outer edge of this solar system. Then we colonize on, perhaps making waystations in interstellar space, and go from there. It might take longer, even twice as long, or three times as long, but it's much less strenuous on any given person.

Well obviously fusion bombs have come before, and the only example of fusion technology that works for us is fusion bombs. The interesting thing about fusion bombs is it takes the same amount of fission-ables to trigger a small one as to trigger a large one, we just need more deuterium for the larger ones, this argues for larger ships that can carry the most people for a given number of fission cores. So the question becomes, how much Uranium is there in the solar system? This is where Mars might possibly come in, because Mars at one time had water, and flowing water might have concentrated Uranium ore in seems, Earth also has Uranium but it is at the bottom of a larger gravity well, and their is environmental impact that needs to be considered in mining it. On the other hand there is plenty of sources in the Solar System for deuterium, we can probably make hydrogen bombs in space, and for an interstellar mission we'll need a lot of them, way more than has been in our entire arsenal during the height of the Cold War, but there is no reason why we couldn't build more. One Idea is to build the CIV first and use it as a space station to house the workers that mine the materials and build the bombs in space. A CIV equipped with a fission rocket could perhaps travel to the asteroid belt, and mine out Uranium or deuterium, make tritium, build enough bombs and the storage magazines for them and the giant pusher plates, then we could be on our way to Alpha Centauri.

Tom Kalbfus · 2014-06-10 11:33:12

Void wrote:

The problem with fusion, IMO, is that it's not an incremental jump in technology but rather represents technologies totally unlike any that have come before. It's not impossible, but it is surely more difficult. Fusion is obviously possible, and will probably have been perfected by the time we get to the Oort cloud, but it never hurts to remember that Fission is still a viable option.
So try both, settle for less if you have to.
Helium 3 from the Moon, enriched heavy Hydrogen from Mars. I believe that there is a greater percentage of it in the water of Mars than Earth.
I think Helium 3 makes a cleaner (Radiation) explosion. At a lower temperature as well? The benefits of Helium 3 for bombs seems ambiguious to me, but its worth thinking about.
http://en.wikipedia.org/wiki/Helium-3#E … _abundance
A more standard fuel would likely be better, if you wanted to refuel periodically while moving from the inner solar system to the Oort cloud.

Deuterium-Tritium has more neutron output, some of these neutrons will hit the pusher plate, and there has been talk of using pusher plate material as fuel for the nuclear reactor on the CIV, after all it has to generate 1360 watts per square meter of artificial sunshine for 140.8 years.

Void · 2014-06-10 12:32:00

I do not endorse the following because I am not equiped to evaluate it. However it does sugget that perhaps the fission part of a Hydrogen Bomb can be discarded, and small Hydrogen bombs crafted.

http://bourabai.kz/winter/mini.htm

Further, in my ignorance I am permitted to suggest the use of Lithium in fusion: (It has been suggested for fusion rockets already).

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

So far I only have to endure an occasional attempt at humiliation or distant threats on this board, and there are many who cannot afford to look foolish, so I will take the chances.

Supposedly they are testing last ummer to see if it works, it uses 3 Lithium Rings. It either did not work, or it is smart to say that it did not work.

http://txchnologist.com/post/4720466431 … e-to-three

Of course with Lithium, you would not be able to obtain your propellant just anywhere.

Perhaps you could preposition it at various locations using solar sails

Too bad it must not have worked out.

Last edited by Void (2014-06-10 14:32:45)

Void · 2014-06-10 14:38:01

Since I am in a hole I will keep digging:

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

Some of these are interesting, and they mention the Orion.

Lithium from the Moon?
http://www.jstor.org/discover/10.2307/7 … 3842444231

Heavy Hydrogen from Mars?
http://www.newscientist.com/article/dn2 … 5cMr6r00iw

Although I don't expect that it would be that hard to use Earth hydrogen either. But it doesn't hurt that the heavy Hydrogen on Mars is already concentrated.

Most hydrogen atoms contain just a proton and an electron, but some contain an extra neutron, forming deuterium. On Earth, deuterium is much rarer than hydrogen – for example, in our oceans one in every 6420 hydrogens also has a neutron. As deuterium is thought to have been produced in the big bang, it should have once appeared in similar abundances on all the planets in the solar system.
That's why the new discovery by Curiosity, which landed in an area of Mars called Gale crater on 6 August, is intriguing. After heating a soil sample to 1100 °C and analysing the resulting vapour, Curiosity's Sample Analysis at Mars (SAM) experiment found a deuterium-to-hydrogen ratio that is five times higher than that on Earth: one deuterium for every 1284 hydrogens.

This also suggests to me that Mars has lost 80% of it's Hydrogen from water to space during it's lifetime.

Last edited by Void (2014-06-10 21:59:12)

Tom Kalbfus · 2014-06-11 21:47:42

Lithium is sort of scarce, though I might be easier to make pellets out of something that is solid a room temperature. It would be best if a starship could run on something that wasn't scarce. My idea for colonization goes something like this:

1. You build a Daedalus Space Probe, but instead of sending it on a fly through mission you have it slow down and investigate the planets in the system, this means the first stage gets the ship up to 6.25% of the speed of light and the second stage slows it down again. At 6.25% of the speed of light it would take 70.4 years to reach Alpha Centauri.

2. Now Daedalus is not s stupid probe like the kind we've sent to Jupiter or Saturn, it contains Artificial Intelligence and a number of robots, so after spending 5 years in the system exploring the planets, out of native materials such as asteroids, it builds another Daedalus Space Probe and another bottom stage for itself as well as mining the fusion fuels it needs to both starships to make another interstellar voyage, lets say it takes another 5 years to do this Now both Daedalus Space Probes launch from the Alpha Centauri System to head to two other star systems.
Barnard's Star 6.5 light years away and Ross 154 which is 8.1 light years away. So it takes the First Daedalus 104 years to reach Barnard's Star and it takes the second probe 129.6 years to reach Ross 154

3. Now at Barnard's Star the probe makes another copy of its self plus a bottom stage plus fuel and heads to the two nearest stars from there, which would be BD-12 4523 AB at 9.1 light years and 61 Cygni at 9.5 light years it would take the first probe 145.6 years to reach BD-12 4523 AB and the second probe 152 years to reach 61 Cygni.

4. At Ross 154, the two nearest stars are Lacaille 8760 at 7.4 light years and CD-46 11540 at 7.7 light years it would take the two probes from there 118.4 years to reach Lacaille 8760 and 123.2 years to reach CD-46 11540.

5. Average distance between star systems is 7.5 light years which takes 120 years to cross.

So if the launch date is 2060, we arrive at Alpha Centauri by 2130 by 2140 two Daedalus probes depart the Alpha Centauri System and arrive at Barnard Star and Ross 154 by 2270, by 2422 we have 4 probes at BD-12 4523, 61 Cygni, Ross 154, and Lacaille, by 2430 we launch 8 probes from those systems to arrive at 8 other star systems by 2550, by 2560 we have 16 probes and they travel to 16 nearby star systems by 2680, by 2690 we have 32 Daedalus probes that travel to 32 nearby star system and arrive on 2810, by 2820 they become 64 probes and they travel on to the next nearest star systems arriving on 2940 by 2950 they become 128 probes which travel to 128 nearby star systems and arrive by 3070. We'll assume an imaginary wavefront of probes expands outward at 3.75 light years per 120 years.

By 120 years its at a radius from Sol of 3.75 light years
By 1000 years the wavefront will be at 31.25 light years with about 330 star systems in it, but will have probes at only 128 of those stars
By 2000 years the wavefront will by at 62.5 light years with about 2640 star systems to explore There will be 26615 probes by then with more probes than their are stars to reach, so by this point every reachable star within this wavefront will have been reached and the number of stars reached will be a cubic function of distance from Sol rather than how many times the number of probes has doubled. Lets say we have six generation ships, we want to design them so they are launched at the same time as the first probe is launched to Alpha Centauri and each one travels in six directions from Sol catching up to the wavefront in 2000 years which is 62.5 light years away by then, There will be probes at every star system within this radius by then and each generation ship will divert towards the best of 440 candidate systems which will be investigated by the multiplying probes. This requires an average velocity of 0.0326 of the speed of light, each generation ship will monitor the data returned by the probes and head towards the most Earthlike planet found by the probes, the best of 440 star systems for each of them. this is all within the capabilities of fusion powered starships, What do you think of this?

Last edited by Tom Kalbfus (2014-06-11 21:52:47)

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