The International Astronautical Congress is in full swing in Prague today, with regular updates flowing over #IAC2010 on Twitter and the first session of interstellar import now in progress as I write this. It’s a session on interstellar precursor missions that includes, in addition to Ralph McNutt (JHU/APL) on the impact of the Voyager and IBEX missions, a series of papers from the Project Icarus team ranging from helium-3 mining to communications via the gravitational lens of both the Sun and the target star (no specific target has yet been chosen for Icarus).
Claudio Maccone will be summarizing where we stand with the FOCAL mission, envisioned as the first attempt to exploit gravitational lensing for astronomical observations. But I’ll turn today to Marc Millis, who will wrap up the precursor session with a discussion of the first interstellar missions and their dependence on things we can measure, such as energy. The notion here is to look at the energy required for an interstellar mission and to weigh this against predictions of when those energy levels will be accessible and available to be used for space purposes.
Energy Needs Drive Spaceflight
How to get a handle on energy growth trends? Millis uses annual data on the world’s energy production from 1980 to 2007, calculating the ratio of each year’s energy production to the preceding year, then finding the average and standard deviation of all 27 of these years. How soon until Earth becomes a Kardashev Type I civilization — one capable of mastering all the energy reaching the Earth from the Sun? Acknowledging the wide span of uncertainty in the result, Millis pegs the earliest year this could occur as 2209, with a nominal date of 2390 and a latest date of 6498. A constant growth rate is assumed, which balances depletion of natural resources against unforeseen advances in new energy sources, leaving growth rates relatively stable.
Fascinating as they are in their own right, I won’t go through all the numbers (I’ll link to the paper when it becomes available online). But note the key factors here, which are the total amount of energy produced by our species and the proportion of that energy devoted to spaceflight. For the latter, Millis compares the annual Space Shuttle launch rate against the total annual energy consumed by the United States, finding that the maximum ratio of Shuttle propulsion energy to total US energy consumed occurred in the year 1985, equaling 1.3 x 10-6. The average ratio over the years 1981 to 2007 is 5.5 x 10-7. Millis then takes the maximum ratio (over an order of magnitude greater than the average ratio) to calculate the earliest opportunity for future missions. What he calls the Space Devotion Ratio is thus 1.3 x 10-6.
The Alpha Centauri Calculation
When could we launch a 104 kilogram interstellar probe to Alpha Centauri based on these calculations? Assume 75 years as the maximum travel time that might be acceptable to mission scientists and assume a rendezvous rather than a flyby mission, acknowledging the need to acquire substantial amounts of data at the destination. Millis extrapolates from existing deep space probes to arrive at a putative mass, adding the needed margins to ensure survival over a 75-year transit and the substantial communications overheard to relay information to Earth.
As to propulsion options, Millis works with two possibilities, the first being an ideal case that assumes 100% conversion of stored energy into kinetic energy of the vehicle (think ‘idealized beam propulsion’ or even some kind of space drive), the second being an advanced rocket with an exhaust velocity of 0.03c. We thus wind up with two sets of figures, again based on energy availability. Millis then converts the propulsion energy figures into equivalent world energy values, using the Space Devotion Ratio he first calculated earlier for US space involvement.
The result: The earliest launch for a 75-year probe is 2247, with a nominal date of 2463. This assumes idealized propulsion; i.e., a breakthrough technology like a space drive. Fall back on advanced rocket concepts and the energy requirements are much higher, with the nominal launch date of the probe now becoming 2566, the earliest possible date being 2301.
Strategies for Interstellar Research
The play in the numbers is huge, the uncertainty in the results caused by the wide span in possible energy production growth rates. Interestingly, Millis’ finding that the earliest interstellar mission will not be possible for two centuries coincides with earlier estimates from Bryce Cassenti and Freeman Dyson based on economic and technological projections. We can, obviously, adjust the numbers based on our projections of technological growth, and as with any projection, sudden changes to world economic patterns would be a substantial wild card.
But Millis argues that in the absence of a single technological solution, it would be premature to focus on specific propulsion options to the exclusion of other, more theoretical alternatives. For that matter, it would be foolish to be inhibited by the ‘incessant obsolescence’ postulate (a term that Millis himself coined), noting that earlier missions may well be overtaken by faster ones launched at a later date. Instead, what he calls ‘cycles of short-term, affordable investigations’ targeting key questions whose answers we can hope to find today are the best way to proceed. And that means continuing our investigations of everything from the already operational solar sails to technologies that today seem impossible, such as travel faster than the speed of light.
Hi Folks;
Regarding high mass specific sunlight or star light power sequestration, it seems to me that our best prospects is to use low cost space based inflatable reflectors. My brother John and I have spent several years developing and refining our IP portfolio which involves ultra-portable high mass specific natural resource collection apparatus that can be used on land, water, underwater, underground, and in space based and planetary environments.
With 0.5 mil metalized Nylon or Mylar stock, we can produce solar concentrators that have a mass specific power output of 10 kilowatts/kg at 1 A.U. from the sun.
It seems that someone really needs to consider space based solar collector powered; beaming stations, anti-hydrogen production, and the like. With solar output of [4 x (10 EXP 26)] watts, we could do wonders as far as very high gamma factor star ship designs are concerned. Whether L’ Garde, Begalow Aerospace, NASA, the ESA, the USAF, and/or JAXA jump on the space based inflatables bandwagon, the opportunity too far to profound to neglect.
Inflatable systems for exoplanetary settlements would be ideal also, especially when considering future materials such as CNTs, BNNTs, Graphene, and other extremely high strength and refractory materials.
Now we know of the primary solar power output as EM radiation. Might there exist some sort of hidden fields or forms of radiation produced by nuclear reactions such as the Proton-Proton sequence? I do not think we can rule the possibility out although due to conservative principles of thermodynamics, such a hidden energy form would likely entail a form of hidden mass at the level of QCD physics or below that does not result currently observable general relativistic effects.
“technologies that today seem impossible, such as travel faster than the speed of light”
Sorry, to correct you and/or Marc Millis, but, to state it crystal clear: The laws of physics — or, if you want, of contemporary physics (but saying so doesn’t lead to anything useful) — *imply*, that traveling faster than the speed of light *is* impossible. It does not *seem* to be impossible. Founding strategies for interstellar research on something the law of physics exclude, is not helpful.
After all, sparkly hyperspace unicorns only seem impossible with today’s technology. MORE RESEARCH FUNDING PLZ!!!
@Duncan,
How about the “laws” of physics, as we understand them today, imply that Faster than light travel is impossible.
Our science isn’t at the stage we can accurately say it’s totally impossible.
This article confirms that we should spend our money on research rather than premature missions. The same should apply to manned exploration of the solar system. Use the money to figure out how to do it right. No more Venture Star/Orion money pits please.
@Greg
The theory of relativity as formulated by Einstein has been shown to be consistent with the outcomes of many pertinent experiments, from small scales up to the distances of far away galaxis — it *is* state of the art. In this theory we have this certain upper limit for the velocity of all material things and energy: the speed of light in vacuum.
Because of this situation — the stage our science is at –, traveling faster than the speed of light *is* very well impossible. This is an implication of the laws of physics, and we can accurately say it.
Greg: our knowledge of astrogeography isn’t at the stage yet where we can totally exclude the possibility that there is a crashed alien spaceship full of wonderful alien technology at the north pole of Triton. Doesn’t mean it is worth funding an expedition to go retrieve it though.
Why 10^4 kilograms? Isn’t that a little high? I’m sure the first probes will be smaller, maybe more like 10^3 or 10^2 kg.
It should be noted that the cost of the energy for Shuttle is incredibly small. If we compare NASA’s budget to the total GDP of the nation, we get something two orders of magnitude bigger than 1.3*10^-6, actually something like 1.5*10^-4. Part of the problem is that most of the money goes into fabricating new rocket parts. A much better comparison would be the airline industry, where jet fuel costs are currently around a third of the ticket price. There’s no way we’ll get interstellar travel of any kind without mastering reusable spacecraft (or, some kind of cheaply produced expendable) where fuel costs are a sizable fraction of the total costs.
So, we have about four orders of magnitude of improvement on the numbers for the first interstellar probe. Plus, it may be that the fuel costs less than the energy contained in the fuel… for instance, Uranium 235 costs around $5000/kg, but releases about 20 million kilowatt hours of energy, which amounts to about $2 million worth of electricity at the residential level. So there’s another 2 or 3 orders of magnitude improvement on performance.
I think the first interstellar probe will either be very much smaller than our current probes, or will be propelled by something like a fission fragment rocket. Since the fuel costs about $5000/kg, it wouldn’t be impossible for such a spacecraft to be built using today’s budgets, assuming the technology for a highly efficient fission fragment rocket is developed. Heck, it’s not impossible to be able to breed the fuel in the rocket, so it may be possible to use natural uranium or thorium, which is even cheaper ($10/kg?).
And the first probes may not even slow down or may slow down without propellant (i.e. interstellar medium braking of some kind), which makes things even easier (as far as energy use, not actual science).
Well, I’ll say it again… FTL is a red herring. Who cares whether a race between me and the wave front of a laser pointer gets to anywhere first (from the perspective of a referee at the finish line)? Besides, even if one did accomplish the feat, all it means is that we’ve found a way to violate causality, not gone FTL. FTL is a pretty meaningless objective since known physics does not preclude getting from A to B as soon as one wishes. If the energy (and safety) conditions are worrisome the correct response is to find either new physics or evidence that spacetime can be other than simply connected. Neither requires nor makes meaningful the concept of FTL.
Lots of people do enjoy speaking the language of relativity but without understanding what it actually means, which is actually far more subtle and interesting that FTL based on 1950s sci-fi. My apologies in advance if this comes across as insulting to anyone — it is unintended.
Why the focus on energy? Making hydrogen to fill the fuel tanks is a very minor part of the effort required to launch a Shuttle. Even refining He-3 for an Icarus-type vehicle would be only a modest fraction of the whole project.
A more general yardstick might be computation cycles (including in wetware). Every aspect of spaceflight – and much else – requires those. The amount of computation done by our civilization has been increasing rapidly according to Moore’s Law (although the fraction of it devoted to spaceflight has declined). One could probably get some more optimistic projections this way.
Since energy production (& consumption) tends to be proportional to GDP, one thing that changes the equation is if GDP grows faster. Also, improving the ‘Space Devotion Ratio’ accelerates things. While the first is largely a political question, the second is (at least partly) something that can be attacked technically. But, perhaps a Tau Zero PAC is in order?
Hi Folks;
I will likely never throw in the towel regarding the possibility of FTL travel. For all we know, there may exist forms of real mattergy that are not general relativistically coupled to 4-D Einstienian Special Relativistic and General Relativistic space-time-mass-energy.
Even if C is an absolute limit for Standard Model and MSSM fermionic and bosonic corporeal material, many possibilities await our civilization, perhaps beyond current reckoning.
Consider the following obvious math and following scenario.
The lifetime of a black hole assuming only Hawking Radiation releases and no mass-energy intake is:
t = (2,560)[G EXP 2][M EXP 3]/{h [C EXP 4]}
t ~ [(M/M0) EXP 3][10 EXP 66] years where M is the mass of the black hole and M0 is one solar mass.
Since black holes radiate away their energy in the form of Hawking Radiation emissions, black holes can be said to have a surface temperature, which for black holes of ordinary stellar mass scales and larger is very, very low.
The temperature of a black hole is as follows:
T = [h [C EXP 3]]/[8 pi k G M]
where h is Planck’s constant, c is the speed of light, k is the Boltzman constant, G is the universal gravitational constant and M is the mass of the black hole.
As we already know, we can see that, as the mass of the black hole decreases, its surface temperature increase in an inverse and linear manner.
The point is that black holes with a large mass are so dimly radiating that if a civilization where to set up shop around a black hole of suitable mass, the Hawking Radiation Emissions would be so small, that there would be very little risk of injury or damage to the inhabitants and infrastructure so disposed.
A black hole large enough to safely contain a colony outside of its photosphere would need to have a mass of about 10 EXP 15 solar masses.
If such a black hole could be constructed artifically or produced by super-cluster inward galaxy and star migration, the possibility of setting up extreme special relativistic gamma factor orbital habitats is plausible while at the same time, extreme gamma factor inertial intergalactic space might be possible. To the black hole habitat and the extreme gamma factor space craft, the effective travel velocity for the space craft in both reference frames could be (gamma)C where gamma is extremely large.
Our distant descendents might not relate to the concept of only sub-light speed velocity limits in the way we relate to because as long as the black holes can live or be maintained, a space craft might
leave a habitat travel to another similar black hole one billion light years away, and come back in 100 years habitat reference frame.
I have thought about the details of how such a habitat could maintain its orbit but that is beyond the scope of the limited spade here.
I hope FTL travel, warp drive, extra-dimensional short cuts, macroscopically induced space craft tunneling, worm hole short cuts, and multiple space time connectivities pan out, and if they do, well “Great!”. If they don’t, I still say “Great!”
We have been in the space age for only about 1/2 of a century, and we know have the quality forum of Centauri Dreams where interstellar travel is rationally discussed and is intellegable by anyone who has completed high school mathematics. This reality should spur the nay sayers not to causally disregard the prospects of interstellar manned space travel. I for one absolutely refuse to do such
If a scientist in 1750 was asked in how much time he thought we’d land on the Moon I’m pretty sure he would have thought way later than 1969.
About FTL, it seems that physics are not absolutely excluding it : breaks in spacetime, quantum teleportation …
As Robotbeat and Geoff point out, energy is pretty near irrelevant for interstellar (or any) flight. What is needed is an engine that can pull off the feat, and the fuel that it requires. We have no idea what the engine will be like, that will require a lot of those cycles Geoff mentions. We have some ideas about the fuel, because there is a limited number of suitable elements, but the specifics will of course depend on the engine. If it is He3, bummer, very expensive. If it is Uranium, Thorium, or Lithium deuteride, it will be a negligible part of the cost and we can start producing it now. The only way energy may become relevant is if the engine runs on a “rechargeable battery”, such as an antimatter storage device. I consider this very unlikely.
Hi All
Deuterium is ~1/10,000 of hydrogen out there in the Solar System. And hydrogen is ~1/9 the mass of water. Thus a mass of deuterium requires processing ~90,000 times that mass in water. If we can fuse deuterium and get a Vex of ~0.035c, then we need 19 times the empty mass of a probe vehicle to be deuterium fuel to get to 0.1 c. Thus we need to process ~1,710,000 times the vehicle’s mass of solar system water to get the fuel we want to launch that vehicle to Alpha Centauri in 44 years. Assume a 10 ton probe/drive combination. Thus we need ~17,100,000 tons of water, which sounds like a lot, but it’s just an ice-cube ~265 metres on edge. Not so bad.
The Moon has an estimated ~600 million tons of water at at least one of its poles. Interestingly the Moon’s deuterium fraction is probably much higher than solar system average, due to differential escape of light water as vapour from impacts was hanging around before being cold-trapped. Perhaps a 10-100 fold enhancement, thus requiring a much lower amount of water processing.
So while the “energy value” of the deuterium is hefty, the cost of extraction might actually be much less. Assuming we’re not trying for utterly gargantuan fusion propelled probes, the launch time could be significantly closer than Marc’s analysis implies.
Hi folks. Might be some confusion here. The earliest energy calculations are based only on kinetic energy without any inefficiencies or propellant considered. This is the lowest estimate which cannot be bested by other options. If you don’t believe it, run the numbers yourself. And with that, a colony ship is the first possible, around the year 2200. A modest probe (75 yr to Alpha Centauri) becomes affordable around 2450. Granted, society might be able to devote more than one-millionth of their energy for such a mission, and that is a fair question. The result, if it’s 10x higher: 2090, and 2340, respectively. Also, this study does NOT address FTL. If you really want to see what the REAL physics has to say on that, check out Chapters 14-16 in “Frontiers of Propulsion Science.” That’s why that book is there so you can see the details for yourselves – and where the exact lines of debate remain. The information is now there! Check for yourself.
– Thanks, and enjoy!
PS – The reason ENERGY is used as the comparison is that it is the most fundamental currency of physical transactions. Propellant is also an issue, but even the propellant ultimately requires energy.
Check the details yourselves !
The assumptions about energy growth and the energy requirements for interstellar mission are just red herrings and probably off by so many orders of magnitude that they make little sense for thinking about such missions and their purposes.
Even if we could send probes out at teh speed of light, the time to get any useful data back within a lifetime limits the radii and number of targets.
Wouldn’t it be more fruitful to spend resources on imaging instead, allowing much further penetration into the galaxy for the information gained? What would be the best approach to image a world with various levels of resolution? Given that we might have discovered an earth-like world in the next few decades, what might it cost to view that world in high resolution? What are the resolution limits? For the time and costs, could we get useful imaging much faster/cheaper than a probe, or not?
I agree that there’s always the potential for wild cards (such as “sudden changes to world economic patterns”) when discussing future projections. In fact, I think the largest wild card of all would undoubtedly be whether we find an unambiguous bio-signature in the atmosphere of a nearby extrasolar planet. Once detected, I don’t think we’d be able to stop ourselves from finding a way to get there to see what it is.
Also, just to comment on Marc Millis’ comment (reaffirming that his energy estimates are the most efficient possible — since they are based purely on the kinetic energy requirement of a probe)… This essentially means we only have two possibilities to reduce our projection dates of a first interstellar mission: (1) devote more of our world energy production to such a mission, or (2) lower the mass of the probe.
Going back to my first statement, I really think finding a nearby alien biosphere would certainly provide the motivation to devote a greater fraction of our world/domestic GDP to an interstellar mission — perhaps up to 100 times more. And, since I believe life is probably abundant out there, perhaps the key to getting an interstellar mission off the ground quickly is simply a matter of finding an inhabited planet in the first place. So, investing in bigger and better telescopes might be the key to securing future funding for an interstellar space mission.
@James M Essig
“forms of real mattergy that are not general relativistically coupled to 4-D Einstienian Special Relativistic and General Relativistic space-time-mass-energy”
Honestly, I don’t know at all what you mean by certain matter being *relativistically coupled* to, well, what? To the four-dimensional space-time according to Einstein’s theory of relativity? If this, then no way. If not this, than a very, very skeptical “hmm”.
@TK
“FTL, it seems that physics are not absolutely excluding it : breaks in spacetime, quantum teleportation”
Again, honestly, I don’t know, what “breaks in spacetime” are — science fiction? yes, I know this from science fiction –, and the latest research about quantum physics (quantum entanglement etc., you know) does not give any prospect of faster than light travel of material things.
People … pleazzzze!
Arthur C. Clarke made a suggestion once–I don’t know if this is original with him–the idea is that it does not take infinite energy to travel at .8 lightspeed, or at 1.2 lightspeed. So if we could find a way to accelerate from .8 lightspeed to 1.2 lightspeed without accelerating through the intervening velocities, we could avoid the infinite energy requirement of 1.0 lightspeed.
Has anybody done any serious mathematical investigation of that possibility? Thanks.
@Duncan,
You do realize as we advance our understanding of the Universe the so called “laws” do change. Even using Einstein’s ToR it is possible to move space faster than the speed of light.
What I’m surprised at is your inability to try and speculate and test the boundaries, most ideas will be shot down because people are not familiar with ToR, but there are ones as Marc has pointed out that can be looked into and we should keep an open mind. After all that’s just good science, test everything, even if it appears to be true.
@Greg
What you are talking about, “to move space faster than the speed of light”, is not correct, because space does not “move”. The expansion of the universe — if this is what you mean (otherwise, please, tell) — is completely different from the movement of things inside the universe.
And you being surprised at my inability to try and speculate etc. Well, you don’t know me, you only consider what I said about the question of travelling faster than light. It has been mentioned here already, if I remember correctly, that the physicist and Nobel laureate Richard Feynman said, “you should have an open mind, but not so open, that your brain falls out”. *This* is my way.
Thinking, that contemporary physics does not exclude travelling faster than light, or some future physics will perhaps make it possible, has nothing to do with an open mind, but with a mind shutting itself off from science and from facts.
An instructive lesson from the history of science (the laws do change):
According to Newton’s physics there is no upper limit for the velocity of material things. Traveling to Alpha Centauri in, say, one year, is “principally” possible. Wow, great, space is ours! But then Einstein showed there is an upper limit for velocity, and this travel is not possible. Uuh, what a great and nasty restriction!
Now, applying my ability to try and speculate and test the boundaries, let us have an open mind, and assume, that the Next Major Physics Breakthrough (TM) will bring one more great and nasty restriction. Instead of getting *only* new possibilities and shiny opportunities, the universe is messing around with us.
An example from my freaky mind: The next breakthrough implies, that our brain is principally not able to understand certain sophisticated aspects of the universe, and evolution cannot change this; the breakthrough has to do with deep-set parts of biology, physics, and mathematics (remember Goedel) combined. But don’t fear, it’s only science fiction.
stephen: Unfortunately your question simply doesn’t make any sense. I have no idea how to parse the supposition of an infinite acceleration and, more to the point, I respectfully suggest you read up on relativity and you will understand that 1.2c or any FTL for that matter is neither necessary nor particularly meaningful as a concept. This goes back to my earlier comment in this thread.
c is not a “speed” in the way we ordinarily think about it and it is certainly not anything like a speed limit sign on a highway. It is unfortunate that c is commonly known as the speed of light, which may have came about because of Einstein’s first description of special relativity was made in those terms.
What we know as c is simply the constant of proportionality between time and the (3) space dimensions of our 4D spacetime. That is, to convert from seconds to meters requires units of meters/second in that constant quantity, as in s^2=-ct^2+x^2+y^2+z^2 where s^2 (s squared) is the invariant spacetime interval for all inertial observers. All massless particles travel along a null world line that appears (from the point of view of us massive objects) at the velocity c when we make a local measurement.
I expect that this explanation may appear like so much gobbledygook but it can be pretty easily understood by reading some introductory material on relativity.
Basically, c is not a speed limit and there is “merely” the need for propulsion (or energy) to get anywhere you want as quickly as desired.
Greg: Do *you* understand what FTL means??
Duncan Ivry :
About quantum teleportation the point is that it might be possible for information to travel FTL, if you have the information then who cares about material things ? (you can build them again almost identically with sufficient informations)
About breaks in spacetime i’m not referring to science fiction, the only science fiction books that I read are Asimov’s and he doesn’t really address the issue … In the Elegant Universe Brian Greene states that string theory allows spacetime (not Einstein’s !) to break and then fix itself. Greene, Morrison, Strominger and others discovered this studying Calabi-Yau spaces.
We all know that as good as is Einstein’s work it doesn’t reflect the sheer reality of the cosmos so don’t be that close minded …
@ Ron S.
“Greg: Do *you* understand what FTL means??”
As much as my undergrad degree in physics allow me. Is there a point? As far as I know there are no FTL physicist’s, just speculation at this point.
Hi all,
Motivation is a key issue here, as it is in many human endeavors large and small, societal and individual. These are interesting calculations, but even if it becomes economically feasible to send a mission to Alpha Centauri this does not necessarily mean the societal motivation will exist to do so. For example, as many of us know and are dismayed by, the world’s energy usage is higher than it was in the 1960s and yet we are doing less, not more, in terms of human (not robotic) space exploration than we did several decades ago. Furthermore, significant advances in materials science, biotechnology, computers, over 1960s levels have not translated into humanity traveling further distances, or even the same distances, away from planet Earth compared to our mid 20th century excursions.
What we desperately need is the same level of enthusiasm and public involvement in securing our future in space as was displayed to make sure that the Hubble Space Telescope was not discontinued.
My question to you all is this: How do we motivate large associations of people to get them firmly behind the goal of deep space exploration and colonization?
@TK
Thank you for your answer.
Regarding information: It’s a misconception that information is kind of non-material, which would imply that certain restrictions (which? why just the speed limit?) for material things do not apply. Information is always “incorporated” as matter or energy and cannot be transmitted faster than light. And, yes, I know that “information” has several meanings; I talk about physics.
Regarding breaks in spacetime: String theory has the state of being very speculative — yes: very. It’s very far from being a useful and accepted part of physics. When you say someone “discovered” something “studying” something related to string theory, and that “string theory allows …”, I have to say, sorry, it’s a case of “*only* in theory”. There are no experiments and no observations (not in experiments and not “outside” in the cosmos) — no *real* discoveries –, and there are no testable predictions. It still doesn’t imply anything for realitity.
Regarding being open or close minded: Please, be open minded enough to recognize how serious physics works, and where the line is between useful speculations and useless pipe dreams.
@stephen
“Arthur C. Clarke made a suggestion … accelerate from .8 lightspeed to 1.2 lightspeed without accelerating through the intervening velocities …
Has anybody done any serious mathematical investigation of that possibility?”
Yes, but first a clarification: A *mathematical* investigation alone is not enough, because in this case we have to use mathematics as a tool of physics. Otherwise it would make no sense saying “accelerate from to” and talking about “energy”.
Well, “we” did this already at school and later at university studying mathematics and physics. There is no way going from under light speed to over light speed.
@Alex Tolley
Jill Tarter determined that micro arcsec optical resolution should be possible for a space telescope based on the clarity of the local interstellar medium. The primary mirror of a micro arcsec telescope would have to be 120 kilometers in diameter. Not a small undertaking, even if done with several much smaller mirrors and interferometry. You still need a very big optical array in space. But certainly much easier than any sort of interstellar travel.
What this means is that for a planet 40 parsecs (130 lightyears) away, you could resolve features as small 6000 km, such that a planet similar to earth would have an angular diameter twice the resolution of the telescope and you could (sort of) image continents and oceans. What would such images look like? We have a model at hand. The minor planet Pluto has an angular diameter just twice the resolution of Hubble. Even so we have (fuzzy) maps of Pluto, generated with long observations and brilliant computer image enhancement.
http://en.wikipedia.org/wiki/File:Pluto-map-hs-2010-06-a-faces.jpg
Is this worthwhile? You bet! A telescope that could image could also do some nice spectrography looking for life signatures. There are about 30,000 stars within 40 parsecs of sol. Ok, admittedly, 99% of these stars are not very sun-like, most are red dwarfs, some are very young, some are very luminous, and some are white dwarfs. Even so, there are certain to be quite a large number of extrasolar planets in this volume to study, including many around very sun-like stars. Plenty of astronomy to be done in the long interval between now and whenever sending an interstellar probe becomes possible.
Ron S.: I was only quoting Arthur C. Clarke; you’ll have to take it up with him.
This wasn’t a suggestion of infinite acceleration; only the non-infinite acceleration we would hypothetically need at a velocity of (for example) 400,000 kilometers per second. I don’t know how to jump from 100,000 kph to 400,000 kph, without traveling at 100,001+ kph, but somebody might come up with something.
People have been coming up with lots of loopholes in lots of different physical theories.
Duncan Ivry :
I know what you mean about information, nothing new for me thanks, I’m talking about the hypothetic use of quantum entanglement to teleport information. People are still studying this, why is that, because they’re idiots ?
And yes strings theory is highly speculative, but also the most promising theory according to many respected scientists. On the other hand we also know that Einstein’s work is just an approximation of reality. What you say about experiments and observations is irrelevant to my point, I didn’t say “FTL is feasible” I just said don’t rule it out blindly because some promising theories don’t rule it out. But then again you might consider that the highly respected physicians working on string theories are idiots ignoring serious physics.
I’m out.
Regarding the fidelity of these estimates: Yes they are crude with huge uncertainties, so much so that only 1 significant digit is used in the final table. The odd thing, however, is that 3 separate studies all came to the same ‘2-century’ conclusion. One was a financial study, one based on technological progress, and mine based on energy. Go figure (so to speak).
The good news, is that such time means that it is premature to pick favorite methods and thus provides opportunities for all the approaches to make progress on their key unknowns.
Interesting thread and discussion.
A few observations (sorry, if I repeat others);
– The only things I know that may go FTL are quantum entanglement (though it is not ‘going’ in the strict sense) and gossip. I am not sure whether QE could transmit information, it might if you manage to create some kind of binary sets of (hydrogen) atoms in QE entangled state. Of course you would first have to get one half of each set to the other end.
– Space Devotion Ratio: it is known that as prospertity increases people spend a much greater proportion of their wealth and energy on luxury things, such as travel. The amount of energy we spend on vacations nowadays would have seemed incredible to a person in the middle ages. Likewise, to an advanced civilization, for which energy is hardly a limiting factor, it might be entirely acceptable to spend 0.1 or even 1% of its total energy budget on space travel.
– Very nitty-gritty: a KI civilization , in my knowledge, is not one that uses all solar energy that reaches to earth, but all solar energy.
– If our global energy consumption keeps growing, as it has been doing approx., at some 3% per year, we will have used up (cumulatively) all deuterium in the earth oceans and all He-3 of Uranus by 2800, all He-3 of all four gas giants by 2900, and we’ll need the entire output of the sun by 3050.
All deuterium of Jupiter will be finished by 3250, all deuterium of all four gas gas giants by 3280.
And finally, we’ll need the entire energy output of our MW galaxy by 3900.
That is what exponential growth does.
– Marc Millis’ interesting calculations confirm one important point to me: that telescopic research will always be much (MUCH) cheaper and closer at hand than interstellar travel. Within a few decades we will probably have a good overview of planetary systems plus spectral signatures of all stars within many tens or even hundereds of ly. Maccone’s FOCAL mission will bring most of our galaxy and even some neighboring galaxies (Andromeda!) within reach of planetary research, which may happen well within this century and with rather conventional means.
Remaining and very relevant question to me is then: what would be the rationale and justification behind such an expensive interstellar mission, if (improving) telescopic research will always be much cheaper? The only thing I can think of (not a small thing though) is humans actually going there to establish a settlement.
“highly respected physicians working on string theories are idiots ignoring serious physics.”
These PHYSICIANS would have to be seriously multi-talented to be working on string theory… unless it is to suture someone up in a very fancy way… sorry could’t resist.
Physicists, is what you meant I guess.
Indeed Tesh :)
I’m French and the word we use is “physiciens”, I guess that’s why I used the wrong word, sorry !
stephen: “People have been coming up with lots of loopholes in lots of different physical theories.”
I am aware that there are pretty well understand limits to existing physical theories which are waiting on new data or guidance some new insights to allow us to push further. But loopholes? What are those?
I see that my little attempt to explain something about c and FTL failed to enlighten. Let me just say this: assuming you could achieve 400,000 km/s (whatever that might mean) you would not reduce your travel time. After all, you can already reduce it to near zero by staying on this side of c.
Greg:”…just speculation at this point.”
Indeed, but there’s speculation and then there’s speculation. I’ll side with Duncan on this point.
@Duncan Ivry
“What you are talking about, “to move space faster than the speed of light”, is not correct, because space does not “move”. The expansion of the universe — if this is what you mean (otherwise, please, tell) — is completely different from the movement of things inside the universe.”
According to general relativity, locally, yes, light moves at lightspeed through the vacuum.
However, if you’re in another frame of reference, you may see light moving slower than the speed of light or faster than this speed (when time moves at different rates for you and for the light). This is the Shapiro delay.
Marc:
I don’t buy this at all. Because the energy comes from the fuel, fuel is more fundamental here than energy. You can add in the energy that is needed to mine and refine the fuel, but this being nuclear fuel, that energy will be much less than what is ultimately liberated for propulsion.
I should clarify, I should have said space-time, my bad. If we agree with the Big Bang Theory then we see that space-time can expand at any rate, even faster than light.
@Ron S, Please do, it still is a free country, so far as we can tell .
@Eniac: I think the reason that energy is used as the “currency” of the analysis is because you cannot get a more conservative estimate of what is required to send an object to another star than by first considering its Kinetic Energy, KE = (1/2)mvv. Assuming a point-mass (or a non-rotating rigid body), zero starting velocity, and disregarding relativistic effects (which would raise the effective mass), I believe this is your absolute minimum energy requirement.
You want to start with the most conservative estimate in order to give the least possible energy required (in an ideal situation, of course). Then you can add in all the inefficiencies of converting fuel to energy plus the energy required to produce the fuel etc. (these will all push your energy requirement upward).
In spite of TK being out …
I didn’t say anything about certain physicists being idiots — really not, and you should not go down this path any further. It’s just that “they” didn’t get it until now. By “it” I mean things like “breaks in spacetime”, “quantum teleportation”, and more generally string theory.
Not getting it means what?
This all is *only* theoretical; it has not been observed until now, not in the laboratory and not in the cosmos. For many parts there is no idea how to perform experiments. Successful predictions have not been made. So, the important und substantial parts of good physical science are missing.
Above that merely logical and mathematical implications of theoretical, and only theoretical, models are sold as “discoveries” by some persons. And then we have people talking about certain strange things being “possible”, “because” a certain speculative theory is “allowing” it. Now, *that* is close minded.
I hope to see some fascinating breakthroughs in physics in the remaining time of my life. I remembered how amazing it was learning e.g. the theory of relativity and quantum physics — or, as revolutionary as these, in mathematics, Gödel’s incompleteness theorems. I. Want. More.
Scott, I think you mean “optimistic” instead of “conservative”?
In any case, since it is not the energy you have to supply, but the engine and the fuel, there is very little linking the amount of energy a society uses in its economy and the amount utilized by the starship. The starship does not draw energy from existing infrastructure, so it does not matter what the energy capacity of that infrastructure is. It is quite conceivable that we may build a starship that produces and utilizes more energy than our entire economy, while still only costing a small fraction of our GDP.
Without having bothered to look up the numbers, we may already have done so for a different purpose, with nuclear weapons.
I’m sorry I was being annoying; maybe “loopholes” wasn’t the best word to use; maybe you’re right, and let’s move on before I say another wrong thing. Maybe I’ll come up with something worthwhile for the next topic here… Thanks for everybody’s comments. I’ve been enjoying everything here.
I have read some recently published books on the future of global demography. In short, the interstellar stuff is not going to happen.
Energy and other resource consumption is ultimately based on population. More people and the greater amount of energy is generated to meet the increased demand. The big news is the rapid decline in fertility of the developing world. Places like India that had a fertility of 6.0 now have a fertility of 2.7 or so and are declining rapidly. The same is true for Latin America (Mexico and Brazil are already below replacement), Muslim Middle-east, and South East Asia. Only Sub-Saharan Africa continues to have high fertility. This means that global population will peak around 2040-2050 and decline slowly thereafter.
Play around with the stats and graphs here:
http://www.google.com/publicdata?ds=wb-wdi&met=sp_dyn_tfrt_in&tdim=true&dl=en&hl=en&q=global+fertility+rate
and you’ll see what I mean.
Global economic growth from 2040 on is likely to be stagnant as well. Europe and Japan, which have declining populations barely grow at all. This will be true for the “developing countries” starting around 2040, at which time they will be “developed” countries as well.
I think the greenies are going to get what they want, even though it does not come about the way they intended. I think peak everything (demand side, not supply side) is going to be reached around 2050. Global society and economy will be stagnant (but very nice!) from that point on.
Unless human population continues to grow indefinitely beyond 2050, the development of the space industrial infrastructure needed for interstellar travel is unlikely to ever be developed.
All,
Despite my highly optimistic views about the potential for rapid Human Space Travel to distant Star systems both Ron S and Duncan Ivy raise some very important points. The issue of what would FTL buy future Interstellar Travelers is a very important point to raise, and needs much more detailed research, and exploration. It may be that all FTL buys future Space Travelers is some form of time travel, perhaps to alternate Universe’s if it could be done at all which is a big if unless something like Negative Energy can be discovered and manipulated to allow for some sort of Warp Drive or Hyper Space effect. There is also the view by some Scientists that the effect of true FTL on the Human Crew of a Space Ship might actually be to accelerate time on the ship relative to that on Earth so the crew would actually age much faster on the ship at FTL velocities then people would age on Earth.
This said actual FTL travel must be differentiated from quasi FTL travel, i.e. ways around the Space/Time distance barrier entirely by somehow being able to warp Space Time, or somehow jump into a Hyper Space dimension if such a thing exists. All of this involves Black Holes, Negative Energy and the like which we are unlikely to be able to control if ever for many Thousands of Years.
So what are we left with over the next ~200 hundred years. Gravity control or some form of inertia control may be possible by 2200. If we could do that then it may be possible to accelerate at velocities much faster then 1G (although to the crew on board the acceleration would seem like much less). If this were possible then for at least those on board the Space Craft it might seem that a trip to some place like Alpha Centauri would only take a few months instead of a a few years (ship time) if it were possible to accelerate the ship at velocities of 100-1000 G’s, while keeping the ships occupants in a comfortable 1G or less environment. Duncan Ivy is absolutely correct in that it is not at all clear how to do something exotic like this given the known Laws of Physics, but lets seem what happens to those Laws after another Century or two of refinement. We don’t even have a viable Grand Unified Field Theory yet so our understanding of the Laws of Physics are tentative at best, and subject to much change. Obviously, a breakthrough along these lines is not going to solve the issue of long travel time from the perception of people on Earth since Alpha Centauri for example is always going to be a minimum of 4.3 Light Years away given known physics and a trip going there is likely to take much longer then that, perhaps many decades from the perception of those on Earth and potentially those on the Ship as well depending on the average mission velocity.
Finally, to Marc Millis. Given your Energy calculations how do you feel about the lower end (more optimistic) view of when Humans will begin Interstellar Travel? Do you really believe that 2200-2209 ( I am assuming that 2209 is plus or minus a few years so that 2200 and 2209 are essentially identical in terms of your calculations) is viable or is this simply an optimistic boundary condition where all of the assumptions were absolutely best case? In essence, do you believe we even have a shot at 2200 for either a Kardashiev Level-1 Civilization and/or Human Interstellar Travel or is this the absolute best case earliest with perhaps 2300 or 2400 being far more viable?
As a number of posts above alluded to, perhaps the best way to kick start any Human drive for Interstellar Travel starting with Interstellar probes (perhaps as early as 2090 if the energy assumptions change) is with an Interstellar Survey project first, along with R&D on various types of advanced propulsion and breakthrough Physics projects. Various studies in recent years have indicated that for $5-$7 Billion spent over 5-7 years the U.S. could create a multi-disciplinary Interstellar Survey project that would allow us to conduct a comprehensive survey and characterization of everything out to ~60 Light Years from Sol/Terra. 60 Light Years seems to be “the knee in the curve” of what we can do given known technology by 2020
Replying to: “..how do you feel about the lower end (more optimistic) view of when Humans will begin Interstellar Travel?”
The calculations help us understand the factors that affect the answer and the scope of the challenge, rather than to suggest that these are firm limits. These estimates should be taken with healthy doubt. That such preliminary answers would provoke so much discussion is evidence of their usefulness.
The sooner we begin to take the challenges seriously, the sooner we solve those challenges.
Marc, and All,
As you may have surmised by my comments, I tend to lean highly optimistic about Interstellar Travel. Therefore, your 2209 date along with Dyson and others that fall within the next ~200 years for Interstellar Travel was very exciting, while your other dates, 2300+ and beyond were rather depressing. My generational “span of control” is about 200 years in that my Children’s Children may actually see 2200 CE, especially if average life spans are at least 150 years for those born circa 2050-2060+ as now seems likely. Therefore, while I won’t see it the year 2200 is a very real date to me, although going back ~200 years to 1810-1820 does seem like a long time ago.
How do you feel about Ray Kurzweils calculations about achieving Singularity circa 2045, and his projections that in the 21st Century Human will advance about 20,000 years given the law of accelerating development? Even if Kurzweil is only partially correct or off by 100 years it still means that Human/AI Civilization may be far more advanced circa 2200 then we can imagine today. Kurzweil continues to believe that Human/AI civilization will reach Kardashiev-1 level status by ~2100.
Finally, in past comments on this Blog I have advocated for the notion that assuming there is something worth visiting around Alpha Centauri this Interstellar destination case needs to be treated differently from the rest in that Alpha Centauri is within our “Extended Solar System Zone”. While 4.3 ly is a vast distance there may be enough stepping stone destinations between Sol/Terra and Alpha Centauri that one could adopt something akin to a lily pad strategy to get there, and therefore we need to think differently about a potential trip to the Alpha Centauri system compared to some place that might be 2 or 3 times farther out.
What I am really driving at here is the notion that at least through 2200 CE there may be an Interstellar trip to the Alpha Centauri System, and then there may be everything else. If we find something of interest around Alpha Centauri then it is close enough that it could spur a dedicated effort to get there within the next 200 years simply because it is seen as “doable”, albeit just barely, with known technology concepts, money and brute force. On the other hand if there is nothing of interest around Alpha Centauri and we have to go 10-20+ Ly’s out to reach anything of interest then it is likely that Interstellar Travel will take far longer to achieve since the emphasis will be on cost-effective and therefore more technically elegant solutions. I understand your arguments about energy, but something of interest around Alpha Centauri might force a total rethinking of how much energy we were willing to devote to the effort as well as spur other types of innovation. Of course if a Hyper Drive is invented circa 2100 then all of this becomes moot and destinations 10-20+lyr’s out become much more viable.
Bottom line. distance may be the biggest driver of demand and therefore schedule, and the farther we have to go for Interstellar Travel the more we may be inclined to stick to concentrating on our Solar System for many Centuries to come. Given this situation what may happen is a two tier approach to Interstellar Travel. Tier One Interstellar Travel might be focused on the creation of “Alpha Centauri ships and technologies”. Tier Two Interstellar Travel might be focused on “dedicated Interstellar Travel” not subject to Hybrid methods, which could take many Centuries longer. The first step is to get comprehensive survey of the Alpha Centauri system done within the next 15 years to see if there is anything worth traveling to.