Adrian Mann has done it again, as witness his illustration of a gas mining operation on Uranus, reproduced below. The idea, as explored by Adam Crowl on Discovery News this morning, is to acquire vast amounts of helium-3 to supply not only Earth’s energy needs but the fusion engines of the Project Icarus star probe. I love Adrian’s work and particularly his Project Daedalus images, on display along with much of his other work in his online gallery. What he manages to do is to take an engineering concept and translate it into images that are both accurate yet stunning. It’s easy to forget, until he reminds us, that hard-nosed equations and their resulting designs can lead to extraordinary vistas, a result that reawakens the sense of wonder.
Image: Balloons, like those shown here in the atmosphere of Uranus, could be used to harvest helium-3 as starship fuel for Project Icarus. Credit: Adrian Mann.
Adam Crowl is a frequent Centauri Dreams contributor, but he’s also deep in the Project Icarus effort, serving as its module lead for fuel and fuel acquisition. And fuel is the heart of the problem. Deuterium (hydrogen with an added neutron) and the isotope of helium known as helium-3 (containing one less neutron than helium-4, or regular helium) create the kind of reaction Icarus needs. The method is preferable to the fusion of deuterium with tritium because the latter releases about 80 percent of the fusion energy in the form of high-energy neutrons. To avoid that kind of heat transfer to the engine, the original Project Daedalus team focused on deuterium/helium-3, which continues to be the method of choice for the Icarus designers.
But where to get the helium-3, which is found only in tiny amounts on our own planet? You might think the Moon would be useful, given that the solar wind has deposited perhaps as much as 2.5 million tons of the stuff in the lunar regolith. But Icarus has had a long look at lunar mining, and finds that the energy needed to extract it would be greater than what it would eventually produce. That leads us back to the gas giants — Project Daedalus focused on Jupiter for helium-3 extraction, conceiving of a giant mining operation using floating factories in the atmosphere.
But Uranus may be the better choice, and that leads to quite an interesting infrastructure. Here’s Adam’s take on the advantages of Uranus, and the technology needed to exploit them:
…as a mining site it has several advantages. The surface gravity, which is defined from the 1 bar pressure level in a gas giant’s atmosphere, is 90 percent that of Earth’s and the speed needed to reach low orbit is lowest of all the gas planets. Uranus’s rings are also high, thin and not showering the atmosphere below with a hail of meteors, unlike Saturn’s.
Accessing the gas riches of Uranus will require nuclear power, however. Designs exist for nuclear powered ramjets that could fly indefinitely in the atmospheres of the gas giants — this might prove a viable means of keeping an extraction factory aloft. Else we’ll be back to using balloons like “Project Daedalus,” serviced by nuclear ramjets.
An atmosphere composed of a cold gas mix that is lighter than helium and not much heavier than hydrogen, means that hot-air ballooning will need to be used. That the oldest technology of flight will find a role supporting the latest, fusion propulsion, has a certain poetic justice.
Getting the fuel home, where it can be used domestically as well as for tanking-up starships, could provide an early pay-off for developing a fusion propelled starship.
That payoff could involve a major change to how our planet gets its energy. Adam looks at world energy demands, which have increased historically at a rate of 2.5 percent per year. By 2100, which for the purposes of argument is chosen as the earliest date for the launch of a star probe like Icarus, 14,000 tons of deuterium/helium-3 fuel would supply world energy demand for a year. The same infrastructure that would return helium-3 from Uranus (conceived as a high-speed freighter built on fusion principles) would offer a continuing source of fuel on our own planet. Making such a case will be a key issue for the Icarus team, because finding the commercial incentive to develop Uranian gas mining is the only way to conceive of it happening.
Are there other options? Sure, and Project Icarus is examining them. If pure deuterium fusion can be put to work — this assumes finding ways to confine the excess neutrons in the plasma created by the reaction and holding down damage to the reactor walls — then we can look much closer to home for deuterium. Now we have a further incentive for a return to the Moon:
Unlike helium-3 we know the moon has large amounts of hydrogen, as ice, and a significant fraction of it will be deuterium. The moon’s low gravity also means that water composed of regular hydrogen and oxygen will escape quicker than heavy water, perhaps leading to a concentration of deuterium in the water of the moon. We won’t know until we return to the moon for a closer look.
We can also look at the fusion of boron-11 and hydrogen, a reaction that is hard to sustain and perhaps impossible to adapt for propulsion purposes. But so far the odds continue to favor deuterium/helium-3, which leads us invariably to the outer Solar System. Taking a long-term look at our possible future, the creation of an infrastructure that can mine the atmosphere of a gas giant would have to make financial sense in terms of energy production at home while serving as a testbed for the technologies that would push much deeper into space. The Daedalus designers glimpsed that infrastructure thirty years ago. We now re-examine their thinking to tune up the concept and bring it into line with the latest in fusion research.
Would it not be more feasible, cost wise, to research high density energy sources such as Antimatter, compared to an infrastructure of transporting 14,000 tons of He3 a year from the outer planets back to Earth? I think an antimatter factor would be considerably less costly.
“We can also look at the fusion of boron-11 and hydrogen, a reaction that is hard to sustain and perhaps impossible to adapt for propulsion purposes.”
Can you clarify this, Paul? There are several teams currently working on real pB11 devices, primarily designed for aneutronic electricity production — what are the reasons such devices, if successful, wouldn’t be adaptable to propulsion? (At the very least, one should be able to power any sort of electric propulsion system.)
If we find a mars-sized planet in the outer solar system, beyond the Kuiper Belt, it might be the easiest place in the solar system to mine 3He. The planet would have to be large enough to trap 3He for the life of the solar system, which would depend on its mass and the temperature of its exosphere.
Getting there would be an issue, but this whole discussion assumes we have fusion rockets.
I wouldn’t rule out Neptune as a source of fuel. If you’re assembling the ship in the inner solar system, and *if* you have a way of braking packages at the bottom that is insensitive to approach velocity, then the combined delta-v of escape velocity and injection into transfer orbit is actually lower for Neptune than it is for Uranus (it’s because Neptune is farther out).
Greg, because energy is the limiting factor for interstellar ships, not mass, and because the minimum-energy mass ratio is about 5.0, then there is no mass-related cost saving in antimatter, but there is a considerable increase in energy-related costs (antimatter is more expensive to make). If you really needed to go much faster than about 0.1c, then you’d be forced to abandon fusion and go for anti-matter, but for 0.1c and 5.0 mass ratio, fusion is the cheaper option.
“By 2100, which for the purposes of argument is chosen as the earliest date for the launch of a star probe like Icarus, 14,000 tons of deuterium/helium-3 fuel would supply world energy demand for a year. The same infrastructure that would return helium-3 from Uranus (conceived as a high-speed freighter built on fusion principles) would offer a continuing source of fuel on our own planet.”
This sounds remarkably like the justification for mining the moon for meteor impact platinum for fuel cells in a hydrogen fuel economy. Technology is rapidly obsoleting the need for platinum for fuel cell membranes in the pursuit of inexpensive systems. Even if he-3 fusion was demonstrated today, it would take a long time to get this distant, and possibly fragile, supply system going. I suspect orbiting solar power satellites would prove cheaper to build than hypothetical He-3 fusion reactors, and they are demonstrated technology, so the main issues are the economics.
I could certainly see that fusion rockets would be fantastic for opening up the solar system, and that might be the justification for major He-3 mining in the future, although I wonder if direct manufacture might be an economic alternative.
Helium-3 may be great as a fuel source for a ship like Icarus, but using it as some sort of goal or excuse for space exploration is just wrong.
There are NO working fusion reactors on the Earth. Confinement fusion, like ITER, will never be economically viable. Sustained break-even (or positive power output) is decades away (and has been for decades…) Other forms of fusion power (like Bussard’s Polywell and laser confinement) may have potential, but compared to ITER they have no funding.
A Helium-3 powered reactor is further in the future and involves an even greater leap in technology.
Then there’s the question of why go into space to get He-3? It would be cheaper, in the long run, to produce He-3 in fission reactors. We don’t even have an infrastructure to support space industries while we do have the infrastructure to process fuel rods.
If you’re going to go out into space to collect a potentially useful spacecraft fuel (and energy source) collecting antimatter in high Earth orbit or Saturn makes more sense. At least we know how confine anti-matter and how to make an anti-matter rocket (just add some matter and point it away from your face).
Del,
The cost of Antimatter production could be considerably brought down if we actually constructed “Antimatter factories” particle accelerators that are designed to catch and store anti-protons and positrons.
As often as the helium-3 mining trope gets dragged out to justify Moon-mining there seems to be a misunderstanding about the nature of fuel acquisition – a source is to be preferred if it is a net energy gain to acquire. From Uranus it is a next gain, several times over, even using high-speed freighters. From the Moon it’s a net energy drain by a small factor. But antimatter is a net energy drain by, at the most optimistic, about 10,000 fold. Piling on more fusion fuel to achieve the same delta-vee is to be preferred up to 0.5c and probably a bit beyond. Even giant laser pushers are a better option. Not until someone proves a highly efficient production means does it make sense.
Surely, Li-H and B-H fusion reactions have more potential for interstellar travel, since they can be both (a) stored as fuel rods, allowing arbitrarily high mass ratios and hence velocities, and (b) [possibly] be used more easily in a Ram-augmented interstellar rocket?
I don’t consider He-3 to have much potential for high velocity (0.6c) travel.
While fusion powered star ships makes sense, I doubt once we have industrialization in space, that man-made fusion energy will be competitive with natural fusion energy for power generation.
Adam, I’m not arguing for He-3 mining on the Moon. The concentration is so low and you would have to process too much regolith. But is the net energy argument valid when you have abundant solar power. If you double the size of a solar concentrator then yes, you double the energy input. But you didn’t have to transport that fuel to the Moon. The sun delivers it for free so the cost of input is more about how much it would cost to construct that mirror from lunar materials and the time and material needed to set it up.
Greg,
Even if our primary energy source (fossil fuels) could be converted to antimatter with 100% efficiency, all the fossil fuels left in the ground would not hold enough energy to fuel a crewed interstellar mission.
Hydropower is not growing. Fission power is in decline. Fusion power is non-existent. Wind and terrestrial solar power are growing, but are still marginal primary sources of energy and may always be. Good wind sites are limited, and terrestrial solar must compete with other land uses.
Space solar power has been promising (in theory) for decades, but so far not one kwh has been produced for industrial use. Launch costs and costs of photovoltaic materials need to fall by several orders of magnitude for this industry to become a reality. This dream has become as elusive as beyond break even fusion power.
To get quantitative about it, a successful crewed interstellar craft traveling at 0.1 c for decades is unlikely to mass less than a modern nuclear submarine. One needs onboard power, radiation shielding, consumable stores, recycling systems and so on. Lets say it masses 20,000 tons. So in motion it has kinetic energy of 10^22 joules. Note that no drive is 100% efficient in converting thermal energy to kinetic energy. Also note that one needs to decelerate at the destination, perhaps a magnetic sail would do the job, but even that system adds more mass.
A barrel of oil contains about 6 gigajoules of energy. There are circa 10^12 economically recoverable barrels of oil left in the ground. A total of only 6 x 10^21 joules! Economically recoverable coal and natural gas resources are of the same order of magnitude as oil, not to mention that all of these are required to maintain the current population at their current standard of living.
Bottom line, breakthrough primary energy sources are needed just to maintain current civilization through the end of this century. If we can do it, maybe we get to the stars. If we can’t, 2100 will look a lot like 1900, but with a much higher human population and less biodiversity.
Does anybody know if the schemes that use small amounts of antimatter to induce fission and then fusion in deuterium-tritium are also capable to fuse helium3 and deuterium ?
Given that we have no economically viable working fusion reactors (let alone for helium3) , anti proton induced fission and fusion looks like the only viable alternative.
Hi Tobias
We know D-3He can be ignited by near-term technologies. The p+11B reaction is somewhat more difficult to ignite (though maybe not as bad as once thought) and the lithium reaction has other issues negating its practicality. Both reactions are much less power dense than D-T, D-D or D-3He for realistic driver energies and/or confinement conditions, depending on your ignition scheme of choice.
The problem for interstellar travel requirements with fusion reactions that needs to be addressed is the specific power of the proposed reaction. To get to Alpha Centauri via fusion power, within a century, means a specific power of 100s of kilowatts per kilogram of vehicle mass. Gargantuan fusion machines massing thousands of tonnes but putting out a mere gigawatt of jet-power aren’t going to get you to the stars in a reasonable time.
Years ago, in the early 1960s, a JPL study pointed this out – “The Feasibility of Interstellar Travel” by Dwain Spencer and Leonard Jaffe. Worth tracking down. There’s two versions – the original short report and an extended report, delivered at a symposium, which looks at generic fusion rocket performance. Another interesting piece is Appendix A., by John Trenholme, to the 2003 report on VISTA, the interplanetary ICF vehicle. Discusses spacecraft scaling for high performance missions.
Fusion propulsion to the stars is NOT easy.
Mining He3?
That makes me wonder how many (kilo)grams of He3 the US could of recovered from nearly 60(?) years worth of (decaying) tritium used to make 10000 nuclear warheads fusible?
Joy,
I am not suggesting to use pounds of antimatter nor as replacement as a source of energy. Using just milligrams in an antimatter catalyzed fusion or fission could reduce weight of a interstellar probe. There has been several designs that utilize this, NIAC had a antimatter sail and then Penn State had there ICANN spacecraft.
Adam,
You don’t need to make antimatter on Earth – you could collect it around the Earth or around Saturn (James Bickford’s work:) https://centauri-dreams.org/?p=1569
https://centauri-dreams.org/?p=1567
Certainly more feasible and realistic than going out to a gas giant to collect He3.
Joy, an interesting perspective which leads to the question; If such vast amounts of transport useful energy can be mined from Uranus, what other demands would need to be met before the money went into interstellar probes? I think it’s realistic to expect that such mining would initially be started to supply commercial demand, starships would happen decades later.
Andrew,
If human nature remains the same, a good default assumption, people are unlikely to spend more than 1% of their energy budget (money) on interstellar missions. Also, they are unlikely to support projects that take much more than a decade to build.
Current world energy production is circa 5×10^20 joules per annum. A fast crewed interstellar rocket mission would require circa 5×10^21 joules per annum for a decade to construct, fuel, and launch. (My assumption is that construction costs and fuel costs will be at least 5x the kinetic energy of the starship in flight) The world economy would have to expand another thousand fold for this to happen . This is extremely unlikely without something as breakthrough as mining fusion fuel from gas giant atmospheres, and moving most industry off Earth.
While such developments probably do not violate any laws of physics, they might simply be beyond the ability of our species to organize. For the past few decades, it has been easier to find funding for billion dollar casinos than billion dollar telescopes. Why should the future be different?
My guess is that if Earth life forms (or our AI machines) ever do reach other stellar systems, they will do so on the wings of solar sails — like dandelion seeds in the wind, resting dormant through passages of thousands of years. As with America’s Cup sailing, such efforts would not require a species wide mobilization, merely the marginal private economic activities of a few wealthy individuals.
PS: I have a modern sailboat. I joke that it is my spaceship, not much of an exaggeration. It is much more than a rudder, lines, blocks, and sails. Monitoring of all the onboard systems at once is simply beyond human capability. (diesel, refrigeration, desalinator, wind generator, radar, SSB, VHF, weatherfax, satphone, water pump, depth sounder, navigational computers, wind instruments, GPS, emergency beacons, bilge pumps, windlass, lighting, ventilation, powered winches, entertainment systems, oven/range, antifoul protection, zinc anodes, macerator …)
I need an onboard AI! As on the ISS, most of the crew time in transit is spent on systems inspection, maintenance, and repairs. Hard to imagine how much more demanding a crewed starship would be.
Hi FrankH
The antimatter Bickford seeks to collect masses ~1 kg at most. Enough to ignite fusion reactions perhaps, but not for primary propulsion. Also the collector is very large and in orbit around Saturn – about the same level of difficulty as mining a gas giant IMO.
Joy,
Agreed, I wouldn’t expect to see fusion powered starships or even probes until such systems were being used for driving thousands of commercial vessels around the solar system, and I wouldn’t expect that until the solar system was well occupied.
By the end of this century perhaps we’ll see a colony on Mars, but travel to and from there will be with solar or conceivable fission powered ships, then maybe in the 22nd century we might see the outer system being exploited, and only then, with the lower solar flux and greater distances of the outer system, will someone decide that an economic argument can be made that fusion power beats solar power, and in the same way that fossil fuel superseded wind in ocean transport, we might then see a transition to fusion ships that zip around the solar system at accelerations approaching 1g. Only after that’s happened will a little bit of that energy be made available for interstellar flight.
Oh, and by then we’ll have such good telescope technology that we’ll know all the planets in all star systems out to a couple of hundred light years anyway, and will have a reason to send probes to any with O2 rich atmospheres.
the images are all pretty and stuff, but I think, if one wants loads of He3, and doesn’t have the can opener, best thing to do is to irradiate
Li6+n->He4+T,
T->He3+e-+neutrino
you will have to wait a few decades for the second reaction to complete, but, as I said, we don’t have the can opener of gas giant mining colonies yet. And we might require the very He3 to get there and build them.
@Joy. It is not human nature. during 1960’s NASA budget went up to 4.41% in a few years, and the back. And I am sure the human nature remained unchanged. I’d bet, that if th motivation were right, and the prevailing political doctrine were not ‘greed is good’. we would have no problem to spend more than 30 % on space expansion.
For example, when I asked my friends, relatives and colleagues (biased sample, I admit), how much of their income would they be willing to spend on building a self- sufficient mars colony, the most answers were between 1/3 and 1/2. some were above, and some were exactly zero. None were 1 % or 0.5 % at most.
erraata : “and the back” should be “and then back”
Joy
if one of the closest stars in 40 light years would have a planet with life maybe it would go faster.
Denver -very good point about the tritium decay. Let’s not forget that H-3 decays to He-3 with a 12.3 year half-life.
As well as all the weapons with decaying H-3 in their warheads, there is ternary fission (producing H-3) occuring in every nuclear power plant in the world. Also tritium is produced via neutron activation, particulary in heavy-water moderated reactors.
Looking further ahead, IF D-T fusion power plants become the norm in the future, there will be a huge world-wide tritium fuel cycle. All that tritium will be decaying away according to its half life, producing He-3.
He-3 will simply be a by-product of the fusion nuclear fuel cycle, so no need to go elsewhere for it.
Fritz Zwicky, one of the more interesting and brilliant astronomers of the last century, had a very interesting and out-of-the-box plan for venturing around the galaxy (quoted from Wikipedia):
“Zwicky also considered the possibility of rearranging the universe to our own liking. In a lecture in 1948, he spoke of changing planets, or relocating them within the solar system. In the 1960s he even considered how the whole solar system might be moved like a giant spaceship to travel to other stars. He considered this might be achieved by firing pellets into the Sun to produce asymmetrical fusion explosions, and by this means he thought that the star Alpha Centauri might be reached within 2500 years.”
http://en.wikipedia.org/wiki/Fritz_Zwicky#Guns_and_goblins
So maybe instead of looking out for some little nuclear-powered starships or ones with really big sails coming our way, we should see if there are any star systems moving rather rapidly in our direction.
http://www.dynamical-systems.org/zwicky/Essay.html
At least with Zwicky’s idea, we won’t need to develop fusion power, as we will already be using the biggest fusion reactor in the Sol system, one that has been running without fail for five billion years and has a few more billion years left in it. Plenty of time to tour the Milky Way, plus we will be able to take ALL our resources and other comforts of home with us.
frankenstein monster said: “biased sample, I admit”
Now there’s an impressive understatement.
“None were 1 % or 0.5 % at most.”
You pick that range because that’s the reality.
“during 1960?s NASA budget went up to 4.41% in a few years, and then back”.
Yep, it didn’t stay long even at that modest level, so when the US has colonies across the solar system, all you need to do is arrange a space race with some nation that you’re already in an arms race with, though you probably still want the results back within a decade to make it possible as a political sell.
Mining on Neptune? Seems far-fetched we as a species would ever have the will to do engineering on a scale like that, considering the timeline and the costs.
Bussard’s polywell experimental reactors were ultimately targeted at the boron-11 – hydrogen reactions, if I am not mistaken. If that ever comes to fruition, then we won’t need to mine Neptune, or even wish we could mine for He-3. From what I understand, the Navy is still trying to verify his findings with the WB-8 reactor to determine if more funding should be spent on this design.
“if one of the closest stars in 40 light years would have a planet with life maybe it would go faster.”
Henk,
Only if you have a revolution in biology first. People are quite biased towards wanting to see results from what they pay for. If there is an Earth twin 40ly away (plausible), and one is able to make enough antimatter to travel at 0.5c (no comment), a starship (either human crewed or AI) would be 80 years in transit and the laser report back to Earth would take another 40 years to arrive.
A total of 120 years post launch to get data back? Not viable with current human lifespans. Almost no one cares about what will happen after they are dead. On the other hand, if the lifespan of at least a few elite people can be extended to centuries, they might develop the psychology required for undertaking such long term projects. Alternatively, if AI is developed and the AIs take over government, they might have a longer term perspective.
@Andrew W
you may test the hypothesis too. ask your friends, relatives, etc, how much they would be willing to spend on building an independent mars colony.
I predict the answer will be either >= 1/4 or zero, and virtually nobody in between.
You said “You pick that range because that’s the reality.”
That was the point, after all. To compare stated preferences with reality. To show that it is not human nature, but something gone awry in the decision process, because the policy does not match the preferences.
You said “ll you need to do is arrange a space race with some nation that you’re already in an arms race with”
You are moving the goalposts here. Now is human nature ‘invest at most 1% into expansion’ now it is ‘invest at most 1% into expansion, but if, and only if there is an expansion race, give more’
Guess what ? I am not buying it. If some circumstances can change the investment level, then so can other circumstances, and the < 1 % is thus caused by circumstances, not human nature.
I have to question, what would one be spending all that energy on? Also, if you have fusion rockets, building a starship is essentially a case of attaching one to a habitat and giving it lots and lots of fuel. That’s raw fuel, so you don’t need to convert it into energy.
Things are different if you’re using beamed propulsion powered by solar energy, of course…
@joy
Humans have built monuments that took more than a lifetime, for example cathedrals. Funding was arguably > 1% as the Catholic church extracted tithes (1/10’s) of all income.
That may be hard to repeat today, but I don’t see human nature as a barrier, rather the social systems of the time.
Tobias is right, all the talk about how much energy we are using or producing on Earth compared to what a starship would use, has no relevance at all, because the starship would produce its own energy. You need to look at the fuel. What counts is availability, containability, and technological readiness of the methods of use.
Antimatter is the hardest, it needs enormous amounts of energy to produce and is impossible to contain in any reasonable quantities. He-3 is better, but still requires energy and other resources for production. Plus, it is still pretty hard to contain with a good mass-ratio. Lithium deuteride is one of the nuclear fuels with the highest energy density, and it is solid and trivial to contain, at infinite mass ratio. It can also be mined on Earth with very low energy expenditure, compared to the eventual energy output. Unfortunately, direct LiD fusion is not feasible. Tritium breeding , on the other hand, is the most realistic of all fusion methods. Alas, it delivers only a small fraction of the energy directly to reaction products, most is dissipated in the Lithium blanket used to breed the tritium. Some of this could be recovered as electric power for an ion drive, and the rest can be radiated out the back to provide some photon propulsion. Some He3 would also be bred, and could be burned along with the tritium. Still, energy efficiency would be fairly low.
All things considered, I believe tritium fusion with Li-D as fuel is currently the most realistic way to get to the stars. It cannot be beat for technological readiness, and the lower energy efficiency can be made up for by the high mass ratio permitted by elimination of the need for a container.
“Tobias is right, all the talk about how much energy we are using or producing on Earth compared to what a starship would use, has no relevance at all, because the starship would produce its own energy.”
That’s like arguing that anything that burns fossil fuel produces its own energy and so the cost of that energy is not tied to the rest of the economy.
I’ll say it again, before we mine the atmospheres of gas giants we need to get to them (or at least we’ve got to get massive amounts of material to them including trans gas giant atmospheric shuttles) if a fusion propulsion system is good for interstellar flight, it’s going to be good for flight throughout the solar system, so you immediately have commercial competition for this He-3 fuel.
Joy wrote: “Bottom line, breakthrough primary energy sources are needed just to maintain current civilization through the end of this century. If we can do it, maybe we get to the stars. If we can’t, 2100 will look a lot like 1900, but with a much higher human population and less biodiversity.”
I would suggest you check out the Global Warming Policy Foundation (www.thegwpf.org) for news about the shale gas revolution. Together with nuclear fission, we have energy sources on Earth to last for well over a century, at least for those countries which don’t succumb to irrational fears.
Solar power is routinely used by commercial satellites, and has been so for years. Large-scale development of this power source is waiting for low-cost transport to orbit — check out Reaction Engines (www.reactionengines.co.uk) to see how this is coming along.
Obviously construction of manned starships depends upon large-scale prior space colonisation and industrialisation. Since the Solar System has sufficient resources to support a population at least 100,000 times greater than that possible on Earth alone (i.e. at least 10^15 people), this is not likely to prove to be a problem. (Several writers have produced much higher estimates, but this is my estimate at present.)
Stephen
Oxford, UK
Hi Folks;
The graphic showing the balloon for collecting Helium is absolutely beautiful. I have been back to this thread several times over the past few days just to get a glimpse of the beautiful image.
Anyone ever consider the Carbon Fusion Bi-Cycle for powering Icarus. I just thought I’d mention this because this method has been proposed for revamped ISR considerations.
I had some other thoughts for powering Icarus but they would involve very small scale thermonuclear bomblets put perhaps larger then the pellets considered for Icarus. These larger pellets might not go over well given the global ban on nukes is space, but provided most of the fuel could be made to fuse, the ideas might have some practicality.
Astronist:
I second this. Except, concerning fission (Uranium and/or Thorium), I would put millenia rather than “well over a century”. Plus, we are talking about a time when fusion power has been harnessed, making the limits of the above energy sources entirely irrelevant.
No, it is not like that at all. It is precisely because the starship would NOT burn fossil fuel that it’s energy budget is disconnected from that of the world economy.
There is no reason to require that somehow the energy budget of the starship needs to be a fraction of, or even smaller than the world energy budget. The only budget for which this is true is the monetary budget.
“No, it is not like that at all. It is precisely because the starship would NOT burn fossil fuel that it’s energy budget is disconnected from that of the world economy.”
Maybe you should re-read my comment, like oil, such fusion propulsion will have commercial applications if we’re to colonize the solar system, you should probably be happy about that, because the only way this turkey is ever going to fly is with those commercial operators putting in the money to mine the gas giants, and the State (whichever state that is) putting a little of the tax collection into interstellar probes powered by commercially available He-3, the whole thing is just way too big otherwise.
But, why would there be a limit to how much mining can be done? While Terra may only need a few hundred tonnes each year, the facilities are going to be relatively cheap to duplicate if you have significant colonies already there. The limiting factor, I think, will be how many fusion reactors you have, rather than how much fusion fuel you have…
But He3 is useful only for the lowest temperature fusion reactions, which produce mostly neutrons. Those have to be captured and turned into heat, etc — a burdensome chore that the fusion program still hasn’t mastered well in half a century.
Far better to go to the higher temperature Boron + proton reaction that yields 99% alpha particles, which can be captured in a magnetic funnel and used directly for propulsion, or to induce electric currents. That’s the path to a fusion rocket, and Boron is common.
Feeling “degenerate” about propulsion systems
I was reading about brown dwarf evolution a few days ago and had a novel thought. we have been discussing anti matter energy, solar powered systems and fusion, but I though about another energy storage system that may be of value.
As ordinary matter is compressed ( say deep in a rocky planet, or in a brown dwarf) eventually the matter density reaches a point where electron degeneracy prevents further contraction.
This point has never been reached in the laboratory and would require new methods of containment.
However if we could compress matter to the point of electron degeneracy the potential for storage of energy would be enormous. This could be a non- radioactive source that could be recharged when energy was available. Or if you want to “burn it in an propulsion engine, by bleeding off a controlled amount of degenerate matter, I could imagine direct conversion of the atoms to a high speed exhaust plume . Such a plume would be much more energetic than mere chemical rockets, and much faster that current ion drive systems , – And if the containment system was light enough, we could achieve a much better “specific impulse” while not requiring a separate energy source.
Hey if we can speculate about fusion systems that don’t exist because of high temperature containment, why not consider a system that would only require a low temperature containment? and the bonus- no high energy radiation
I read about the need for fuel for these fusion engines in Daedalus and Icarus, but do we have the technology to actually build these engines? I know that the original Daedalus charter called for using near-term technology, but I am under the impression that any kind of fusion for power generation is still a long, long way off (if ever).
I have a fondness for the original Project Orion concepts because, provided we could collect enough fissile material, we could crank out the required number of nuclear devices and perhaps send a starship on its way by the year 2050.
Imagine a Project Orion style bomb pulsed ship that utilized the B-61 package at its highest setting. The weight of this bad boy is 695-716 lbs and the Mod 7 and Mod 11 have a highest dial a yield setting at 340 kilotons = 1.428 x 1015 Joules. The mass faction at this setting converted to energy is equal to [1.428 x 1015 Joules]/[MC2] ~ [1.428 x 1015 Joules]/[[(700/2.201) kg] C2] = 0.0000489.
Now assuming that the pulse rocket system is 60% efficient, the specific impulse provided by the fuel is equal to about [(2 n) – (n2)]1/2 = [(2 x 0.00003) – (0.000032)]1/2 = 0.00774591 C.
Using the relativistic rocket equation, Delta V = C Tanh [(Isp/C) ln (M0/M1)], and a fully fueled mass to final payload mass ratio of 2, we obtain a terminal pulsed rocket craft velocity of Delta V = C Tanh [(0.00774591 C /C) ln (2)] = 0.005369 C.
Using the relativistic rocket equation, Delta V = C Tanh [(Isp/C) ln (M0/M1)], and a fully fueled mass to final payload mass of 5, we obtain a terminal pulsed rocket craft velocity of Delta V = C Tanh [(0.00774591 C /C) ln (5)] = 0.01246 C.
Using the relativistic rocket equation, Delta V = C Tanh [(Isp/C) ln (M0/M1)], and a fully fueled mass to final payload mass of 10, we obtain a terminal pulsed rocket craft velocity of Delta V = C Tanh [(0.00774591 C /C) ln (10)] = 0.01783 C.
Using the relativistic rocket equation, Delta V = C Tanh [(Isp/C) ln (M0/M1)], and a fully fueled mass to final payload mass of 100, we obtain a terminal pulsed rocket craft velocity of Delta V = C Tanh [(0.00774591 C /C) ln (100)] = 0.035656 C.
Using the relativistic rocket equation, Delta V = C Tanh [(Isp/C) ln (M0/M1)], and a fully fueled mass to final payload mass of 1,000, we obtain a terminal pulsed rocket craft velocity of Delta V = C Tanh [(0.00774591 C /C) ln (1,000)] = 0.0534558 C.
We will not go higher because eventually, the Uranium and Plutonium fissile material(s) within the warheads would risk going critical. Perhaps the warhead storage configuration would involve a long space train like deposition either ahead of the main portion of the space craft such as on a forward pointing tower or boom, or the warheads could be stored between the pusher plate and the crew quarters in a large diameter drum or barrel.
The pusher plate might conceivably have a magnetic and/or electric field insulation mechanism. In order to capture as much high energy plasma from the device as possible, a Mini-Magnetospheric-Plasma-Propulsion system or M2P2 drive system might be utilized.
Assuming the craft can accelerate at a rate between 0.1 G and 1 G, the craft could be brought up to speed in under a year. The craft could then coast to the target star system.
In order to arrive at Alpha Centauri, a cruise time of about 4 years/(0.0534558) would be required or about 75 years. To reach Barnard’s star, a cruise time of about 6 years/(0.0534558) would be required or about 112 years.
Thus, we can safely say that we can likely get to the stars at least where our potential energy budgets are concerned. Radiation shielding, collision avoidance, and craft slow down are important considerations, that need to be addressed.
Electrodynamic breaking could be used to slow the craft such as: 1) a conducting or superconducting coil based linear induction based reverse magnetic sail; 2) a magnetic plasma bottle sail; 3) an electro-hydrodynamic-plasma-drive; 4) a magneto-hydrodynamic-plasma-drive; 5) a reverse thrust interstellar ramjet mechanism; a charged plasma drag shoot, a CMBR and starlight drag shoot. The surface area of a CMBR drag shoot would need to be very large and would likely enable only low negative accelerations.
Bomb pulsed star ships such as one’s powered by the B-61 bomb will necessarily need to be very large in order to carry the very large number of nuclear devices as well as to provide an adequate thermal mass to absorb and/or re-use thermal energy buildup within the pusher plate. We may be talking about star ships as large as one billion tons or more when fully loaded. It is even conceivable that ship’s having an initial mass of one trillion metric tons might be required. Such ships would best take the form of multi-generation space arks that would serially drop off landing parties in solar systems the ship would pass by. That way, the ship could essentially drift forever at velocities of between 0.005 C and 0.05 C which are above the escape velocities on any galaxy, galaxy cluster, or galaxy super-cluster.
World zondes, to the extent that they can maintain a green and sustainable life support system, might essentially travel forever through space-time.
Provided that: 1) the expansion of the universe eventually slows to a stop at t = infinity; 2) somehow new real mattergy comes into existence perhaps as a result of natural zero point energy reification; 3) real boson and fermion creation due to dynamic interaction between negative potential energy and positive energy is possible; or 4) natural energy intake from higher dimensional space or space-time is possible, such a high-end Newtonian velocity space ark could travel essentially forever.
But where would we get the required fissile materials and/or depleted Uranium tamper material to make so many B-61 devices. One option is breeder reactors. Another option is lunar mining as the uranium has been detected on the moon. Perhaps uranium also exists on Mars or on Mercury or Venus. Venus would be a difficult source because of the extreme greenhouse gas based atmospheric temperature and the sulfuric acid content of its atmosphere.
Given no other option, we at least have known nuclear device packages that if produced in large enough quantities, would enable very high-end Newtonian velocity interstellar space arks.
I don’t mean to come across as a Cold War era nuclear brute, but we absolutely know how to produce the required nuclear charges to make the star ship work in theory.
With the announcement of what is approaching confirmation of a new particle beyond the Standard Model by Tevatron data mining, one of the three leading candidates for the particle would involve a force that is manifest at much higher energies than the strong interaction. Perhaps, the mass specific yield of any associated exothermic reactions is also at least some what commensurately greater. I am not at all adverse to the production of small scale nuclear explosives based on any third nuclear force, the strong and the weak force being the only two currently known, if for no other reason than that a star ship traveling at a high gamma factor would experience a constant thrust level, while any ETI civilizations located within the remains of the exhaust plume would experience greatly Doppler Red-shifted ionizing radiation. This would at least increase the safety margin.
Interesting article and discussion thread, again.
May I simply summarize by saying that future human interstellar travel primarily depends on the following conditions and challenges:
– Suitable propulsion technology (nuclear probably fusion, be it He-3/D, T/D, …);
– Abundant and cheap primary energy source (probably a fusion fuel, such as He-3, D, …);
– Human life extension capabilities (genetics, biotechnology);
– Human hibernation technology (you want to sleep through most of the journey);
– Motivation.
The last one is probably the most important one ultimately, also driving the search for solutions to the other challenges.
The ultimate motivation for human interstellar travel would be the discovery of (a) habitable (be it life-inhabited or easily terraformable) planet(s).
Therefore, as I often say, first things first. The very first step in interstellar travel must therefore be the discovery and characterization through spectroscopic analysis of (habitable and terraformable) terrestrial planets.
To quote Confucius in a slightly modified manner: every interstellar journey begins with a single light-second.
@ James M Essig June 7, 2011 at 0:17
” With the announcement of what is approaching confirmation of a new particle beyond the Standard Model by Tevatron data mining, one of the three leading candidates for the particle would involve a force that is manifest at much higher energies than the strong interaction. Perhaps, the mass specific yield of any associated exothermic reactions is also at least some what commensurately greater. ”
Where do you go to read more about this force – manifest at much higher energies than the strong interaction ?