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Using Fusion To Propel an Interstellar Probe
astroengine writes "We've heard of nuclear pulse propulsion being the ideal way to travel through interstellar space, but what would such a system look like? In the 1970's, the British Interstellar Society's (BIS) Project Daedalus was conceived to fire pellets of fusion fuel out the rear of an interstellar space probe that were ignited using a powerful laser system. The 'pulsed inertial confinement fusion' wouldn't be 'vastly different from a conventional internal combustion engine, where small droplets of gasoline are injected into a combustion chamber and ignited,' says Richard Obousy, Project Leader and Co-Founder of Project Icarus. Now, building on the knowledge of Daedalus, the researchers of Project Icarus have prepared a nifty animation of a fusion pulse propulsion system in operation on the original Daedalus vehicle."
http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)">Project Orion from the 1950s
Unless we figure out something that allows us to beat light speed even the nearest star is 4 years + away.
I really don't get the fascination with naming space projects after a failed attempt at flight. If there's one thing Icarus didn't do, it was "[build] on the knowledge of Daedalus!"
If you want a vision of the future, imagine a youtube comments section scrolling - forever.
Don't they have them interstellar gates that they can just jump through? Ask their scientists to the famous Dr.Nicholas Rush.
And theoretically, you can get to 0.01c with solar sails. The original calculation is a bit screwy since it assumes a solar sail with mass including payload of 1 kg per square kilometer. But it ignores the effects of the Sun's gravity well. Acceleration deep in a gravity well and for which the vehicle escapes the gravity well results in more delta v than acceleration outside of a gravity well. This is called the Oberth effect. Further on down, someone cites a researcher who supposedly came up with a beryllium sail that could achieve 0.03c.
Simple - you turn the craft around and use the same propulsion mechanism to decelerate.
"Nukular" hysteria will kill it.
Remember when we launched Cassini with a radioisotope thermo-electric generator?
"OH GOD IT'S GOING TO SPLODE AND KILL EVERYONE!!!111ONE"
Every time I see shit like that, I want to slap people.
--
BMO
Well you just accelerate in the other direction to slow down. It takes almost as long to slow down as it did to get up to speed ('almost' because you are now lighter having lost some mass) so you need to start braking early, and in fact you may well spend half your trip accelerating and the other half decelerating.
And it's not as simple as 'send out probes while you fly past' either, otherwise your probes need to be able to decelerate from whatever speed you are doing down to a slow enough speed to land on / orbit the planet, which isn't easy if you are already going at any decent fraction of C. Using the planets gravity will help to some extent, but I think even that has its limits.
Fusion would provide a higher specific impulse than fission - in theory. Due to the large weight of the laser systems and the fuel tanks though, it isn't clear that in a practical design a fission rocket wouldn't be better
Its pretty easy to imagine a fission rocket that used it's fuel pretty efficiently, then used the waste products as reaction mass in an ion drive. . (you might even be able to use the fuel as a structural material before you burn it)
If you are willing to use a solar system based drive laser you can do even better. A soft X-ray laser (say 1 KeV) only needs a 100nm thick sail but has far fewer diffraction problems than a optical launch laser.
I found this rather smart gentleman's video (however, regarding the fictional propulsion system from the movie Avatar) disproving - scientifically - the possibility of interstellar travel in reasonable time frames.
http://www.youtube.com/watch?v=D6H1TxRGLUc
If the only way you can accept an assertion is by faith, then you are conceding that it can't be taken on its own merits
Eh? This is a more exotic form of propulsion -- afraid I don't see your point there.
And it's perfectly suited to slowing down -- the reason the mission profile was a fast flyby is because no matter what drive tech you dream up, decelerating your vehicle takes exactly the same amount of fuel as accelerating, which means not double the fuel, but even more to accelerate the vehicle + the deceleration fuel, to say nothing of the necessarily more massive vehicle to hold the more fuel. Until you can get fuel down to a mass fraction less than, say, 50%, that's simply ridiculous. It also increases transit time.
Example math at 75% mass fraction: (Note that I'm unaware of any concept approaching this for interstellar (5-10 ly) travel on the order of human lifespan -- from Wikipedia, Daedalus would be 92% for a 50-year flight, Orion would be 75% for a ~200-year interstellar flight.) And all simplifying assumptions here are conservative -- you'll actually increase fuel and mass more than this...
Hope your design allows assembly and/or fueling on orbit, else you get to develop a new heavy lift rocket for that. :)
Now at least for daedalus, I'm pretty sure R&D (fixed cost) and fuel costs were the majority, making it cheaper to launch, say, 10 flyby missions than 1 stopping mission. In that case, wouldn't it be hella illogical to send stopping missions to a spot we're not even sure has interesting planets, rather than exploring 10 candidate systems, and eventually sending a second (or later) generation mission (with greatly reduced chance of failure, and somewhat improved efficiency) to the interesting ones?
Really, I've done the math, and even a Heinlein torch (i.e. direct mass-to-energy conversion) requires huge mass fractions of fuel. (Of course, say what you may about his politics ;), but Heinlein's science was usually pretty much right, and this was no exception -- just had to run the numbers to satisfy myself. Read Time for the Stars -- as far as I'm concerned, one of his best juveniles -- if you haven't...) It sounds like you're seriously considering Star Trek drive tech as a mild case of optimism, but it's really pure bullshit, and there's not a damn thing in physics to make one suppose that we'll ever get anything like that.
I found it a rather tedious video (the narrator could stand to speak at least twice as fast). But the propulsion system is never described in the movie Avatar, so he's just making a lot of assumptions. (I don't believe Alpha Centauri is ever mentioned by name either -- another assumption).
Either way he doesn't disprove anything: he sets up a strawman (his assumptions of how the Avatar starship worked) and knocks them down again. In the context of that strawman, he's right (at least, I assume so -- I skipped over a bunch of that video). But that's not to say there aren't other mechanisms for getting from here to there in reasonable (for some values of reasonable) time frames. Indeed there are, although they may be impractical for engineering or economic reasons, not scientific ones.
-- Alastair
40 years ago, the idea of triggering fusion with a laser seemed promising. That's what Lawrence Livermore's Nova laser was supposed to be for. But laser ignition didn't work as an energy source.
Maybe someday, but not yet.
Sure, it looks cool, but is that the only thing you've produced?
http://en.wikipedia.org/wiki/NERVA
'NERVA demonstrated that nuclear thermal rocket engines were a feasible and reliable tool for space exploration, and at the end of 1968 SNPO certified that the latest NERVA engine, the NRX/XE, met the requirements for a manned Mars mission. Although NERVA engines were built and tested as much as possible with flight-certified components and the engine was deemed ready for integration into a spacecraft, much of the U.S. space program was cancelled by the Nixon Administration before a manned visit to Mars could take place. NERVA was considered by the AEC, SNPO and NASA to be a highly successful program; it met or exceeded its program goals. Its principal objective was to "establish a technology base for nuclear rocket engine systems to be utilized in the design and development of propulsion systems for space mission application".[1] Virtually all space mission plans that use nuclear thermal rockets use derivative designs from the NERVA NRX or Pewee.'
Since we can't actually build a fusion drive, this seems like a much more promising technology.
If you do a fly by, doesn't that give you only a matter of hours to pass through the solar system and do what you want? If light take 8 minutes to reach the Earth, and this is about 0.12c, then presumably a 50 year trip becomes less than a day of visiting time?
Granted, research is being conducted before entering the solar system and presumably in the years after passing through. But in principle, it seems so fleeting.
http://xkcd.com/678/
And they combine the knowledge from both Daedalus and Icarus, I'm guessing they'll call it Helios. Wild guess.
There is no -1 Disagree.
Because there is no such thing as a propellantless propulsion system? The closest you could get would be light, and the thrust you get some shining a laser out the back is negligible. All of our current 'electric drives' function by ionizing a light inert gas, or heating it to a plasma, before propelling it out the back using an electromagnetic or electrostatic field.
Yeah, you'd spend only a day within 1 AU of your target, x however many probes you deploy to pass through on more-or-less parallel trajectories (18 for Daedalus). But remember Earth's orbit is a tiny bit in the middle of the solar system, and you'd have a month or more of observations equivalent to sitting in Earth orbit watching $OUTER_PLANET or better. It'd be an insanely huge advancement of current knowledge of other systems -- not as big as entering an orbit and watching for years, to be sure, but I think the advantage it gives your future missions would be well worth the 50-year delay -- I'm not suggesting we give up on that at all, just that stopping is so expensive we need to make the most of that investment with a sortie or two of flyby missions.
Project Daedalus, FWIW, would have had 20m telescopes on it for the observations while approaching and leaving, so you'd be getting damned good observations from lightyears away. And slingshotting the main space craft around the target star for a flyby of another nearby star (for more results perhaps 100 years along) is a real possibility, though AFAIK it wasn't really in the Daedalus profile.
The strategy of doing flybys before orbiters before landings is exactly what we've done in most of our own solar system -- and while I don't have data to back me up, I'd say the results we've gotten from orbiters wouldn't be near as good if we hadn't had the flybys to know what's worth looking at, and therefore what sort of science package we should fly.
We can build lasers that can hit supersonic missiles moving erratically at 10 km from an aircraft, I think hitting a slow moving projectile from less then 100m is the least of this projects worries.
I may agree with what you say, but I will defend to the death your right to face the consequences of saying it.
Soapbox youtube videos are meant for people with a greater attention span than I have. Let me know when the book version comes out.
So, a really basic animation that practically anyone can do is worthy of a Slashdot story - why?
Yes, because Beryllium is such a nice material to work with.... I hope they stick with mylar.
Every experiment which ends in a big bang is a good experiment.
For the record, you are suggesting we put a ship close enough to the Sun to use its gravity well to catapult us out? I mean, how close do you suggest? Do you like it rare, well done or charcoally?
Why? He's done us a valuable service. I now know that bestsdcard.com is not a company that I'd want to do business with, so they've gained a line in my hosts file to make certain that I never accidentally visit their site. I just bought some SD cards, so I probably won't need to for a little while, and next time I'm looking then I won't need to check the reputation of this site, I just won't see it at all.
I am TheRaven on Soylent News
They build a ship that can reach the nearest star in 100 years. Off it goes.
25 years later, they build a ship that can make the journey in 50 years. Off it goes.
74 and a half years later, they build a ship that can make the journey in a day.
Hopefully there's no one in "suspended animation" or "space children" on the first two ships, otherwise they're gonna be pretty pissed off.
This is why getting people to commit to the effort to build an interstellar probe is pretty much a non-starter. We're perfectly happy to wait for the "breakthrough breakthrough" thankyouverymuch.
.
Prisencolinensinainciusol. Ol Rait!
Technical term for "propulsion achieved by firing pellets from the rear".
"Be nice, veer left, and never stop thinking" Iain Banks - Walking On Glass
even the nearest star is 4 years + away.
Don't bother telling them. People who think we'll be journeying to other star systems and colonizing them someday really have no appreciation of just how vast and empty space is. When I was a kid my ignorant teachers used to teach us that the next solar system was just beyond our own, and that one day we would be going there (along with cities on the moon, etc.). When I got older and began to learn from non-moronic sources, I realized just how silly that really was. Our fastest probes today take some 9 years just to reach Pluto. At that rate, it would take that same probe 120,000 years to reach even the nearest solar system--a mere 4.2 light years away.
And you're right, even if we were to come up with some incredible propulsion breakthroughs, it still wouldn't help all that much. If Einstein was right, near light speed is as good as it gets. And that would still make all but our closest galactic neighbors practically inaccessible.
For all practical purposes, we are alone--and will continue to be. But the dreamers don't want to hear that, of course.
SJW: Someone who has run out of real oppression, and has to fake it.
priorities people
petroleum funds ultraconservative wahhabi islam, coal gives us air pollution, fission?: fukushima, etc
yes, fusion will have radioactive byproducts too, but not the 10,000 year half life variety (i believe it is a decade or two for the worst... tritium is it?)
and yes i know the other standard answer: we already have fusion power, it's called the sun (solar panels... petroleum and coal even are fusion energy storage vectors, give or take a couple million years)
and please don't give me the boutique sources
we need fusion plants, on terra firma, asap
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
The Fission powered Orion was possible with 1960's era tech and would be even easier now. Plus there is no reason to think that we won't eventually acheive useful fusion. For instance, Tri-Alpha is talking about breakeven energy within 2 years...
This tech is really the ONLY interstellar tech that is reasonable with our current understanding.
I know where they can get a couple of hundred thousand tons of radioactive water to fuel it...
The correct term is defecation.
Well, while "life" could be common, we might be one of the only "intelligent" species out there.
Intelligence is probably pretty rare because until it is very advanced it tends to be a detriment. Growing our brains is extremly energy intensive and needs many years. Even on earth life formed almost immediatly once the oceans formed but it took billions of years to get to us.
Plus, since both life and technology requier a wide variety of elements, it is unlikley that any star much older than the sun could have formed life. Every generation of star bumps up the concentration of higer elements, systems significantly younger will not have much material to work with.
Finally, we might actually be one of the smartest creatures out there simply because we have more energy available to us. Assuming that life needs liquid water, we can plot out the "Goldilocks" zone. When you map out Sols goldilocks zone you see that it extends from about 0.9 AU out to about 3 AU depending on the size of the planet (yes Mars could have water if it were larger). So we are just barely inside the Goldilocks zone which means we have more energy available to us than most habitable planets. This means that our ecology is likely to be more complex and more agressive than most.
no on is waiting because the tech isn't good enough to make it easy. if we had the tech and the economic might to get alpha centauri, even if it took 500 years, we'd have thousands of volunteers to make history like that
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
Cosmos 954 -- when the Soviets nuked Canada!
the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff
For instance, Tri-Alpha is talking about breakeven energy within 2 years...
Last I heard, that doesn't mean the same think it does to the rest of the world. For them, break even means they measured more energy than they put into the system. That's it. That's an extremely far cry from harvesting the output energy, let alone harvesting in such a manner which is still above breakeven. Even more so, that's a long way toward then redirecting the harvested energy back into a sustainable process. And that completely ignores that their numbers represent a single, completely unsustainable burst of energy. Generally, hours to months are required before the next fusion attempt is possible. That's not even close to any sort of practicality in our lifetime.
Hell, sustainable fusion and making use of zero of its output energy, in of itself, would be an unparalleled human accomplishment that completely ignores something like another dozen feats of equal complexity are required before we can even begin to discuss viable fusion power for humanity.
I used to be completely excited about the potential for fusion power within my lifetime. After all, its always twenty to fifty years out. The reality is, that's complete bullshit. Some time ago I bothered to actually learn something of the associated science. What a complete disappointment and shattering of my nieve ignorance. Frankly, if we have fusion power in less than 150-200 years from now, especially with the borderline funding fiasco (good 'ol boy system) associated with current fusion research, it will be a literal miracle. Personally, I'm betting fusion is another 300-500 years from now, if in fact its even possible at the physical scales they are currently attempting to do so.
Good, maybe we can get the antinuclear hysterics on one side and the space nutters on the other. That would be an amusing scuffle!
the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff
...building a ship based on nuclear-pooping
Table-ized A.I.
So... if we can just circle the sun with superconducting cables and learn how to manipulate the magnetosphere (a trustworthy mutant would come in handy here), could then generate CME's pointed in the right direction to get a solar sail probe on it's way!
I drank what? -- Socrates
The "aliens" use a fission-propelled starship; I believe Stephenson got the idea from project Daedalus.
Great read, with the usual Stephenson caveat - you probably won't be happy with the ending.
Why is it the human race always defaults to a non-continuous cycle for propulsion? I mean, disregarding the historical physics/engineering obstacles, we had reciprocating steam engines before steam turbines. The reciprocating internal combustion engine is much more ubiquitous than the gas turbine. And now a proposal for a discontinuous fusion cycle for space propulsion. Don't get me wrong, I like the idea of Project Orion, especially as glorified by L. Niven in Footfall; "God was knocking, and he wanted in BAD"; and it's a great way to get out of our local gravity well, if all we have left is nukes. But in this day and age, I would think space propulsion would include a continuous fusion cycle (unless, of course, it hasn't been invented yet!). All this human cogitation about interrupted cycles leads me to believe the hand of Darwin is at work here.
Even his straw man knockdown was a bit off. Assuming a space ship has the mass of an aircraft carrier is stupid. Also he didn't even bother to check the Avatar website, it is a beam rider when leaving/returning to Sol.
Don't get me wrong, there is lots wrong with the Avatar science (walkers? everything man operated? unobtainium that you can't synthesize? ) and even stuff wrong with the antimatter engines. But the basic premise is quite doable, both beam rider and antimatter rockets can get 50% c and better in theory with "practical" construction size and mass ratios. Another 100+ years of engineering, who knows.
The Grey Goo disaster happened 3 billion years ago. This rock is covered in self replicating machines!
Chevron nine... locked.
With luck, it will look like one of these designs (with the FTL engines hopefully added on soon after)
Fusion Engines on a starship
StarTrekPhase2 - The Five Year Mission Continues!