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Workable Fusion Starship Proposed
Adam Korbitz writes "A former colleague of Edward Teller — father of the hydrogen bomb — has published a new paper proposing a design for what could be the first practical fusion-powered spacecraft (PDF). As described at Centauri Dreams, the design has certain similarities to MagOrion, a 1990s-era proposal for a nuclear-powered spaceship with a magnetic sail and propelled by small-yield fission devices. The proposal's author also has links to the British Interplanetary Society's Project Daedalus, a 1970s proposal for an unmanned fusion-powered interstellar probe designed to reach 12% of the speed of light on its way to Barnard's Star."
Workable Fusion Starship Proposed
If it's only a proposal, how do we know whether it is "workable" or not?
Colorless green Cthulhu waits dreaming furiously.
a deuterium fusion bomb propulsion system is proposed where a thermonuclear detonation wave is ignited in a small cylindrical assembly of deuterium with a gigavolt-multimegampere proton beam,
that has to be right up there with back to the future. I mean, it has a frickin' gigavolt-multimegampere proton beam
what with how sparse the ISM is, i cant personally see that that would be workable
I have designed a spaceship that uses a scoop to collect amazon affiliate codes.
It will be able to reach Barnards star in a matter of hours.
See here:
http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)
and here:
http://nextbigfuture.com/2008/12/micro-fusion-for-space-propulsion-and.html
I'm all for ideas like this but we won't be building things like this until we, as a planet, have a permanent manufacturing presence in space.
Moon colony, orbiting L5 colony, whatever it is it must be permanent and able to manufacture using locally sourced materials because building something like this from within the gravity well doesn't make economic sense.
"Bah!" - Dogbert
Edward Teller hired my Dad into the Physics department at UC Berkeley and I remember him as a gentleman - he was occasionally at our house. Once my parents had a costume party and Teller was provided with a bird costume - he did not want to wear the mask so he had these big white wings on. The SF Chronicle columnist Herb Caen ran a story the next day saying that Teller was dressed as the angel of peace. Until Teller died a few years ago, my Dad would occasionally travel to Berkeley to visit with him.
One of my grad school profs worked on a project like this. The concept involved a ship farting (for lack of a more appropriate term) out a series of small fusion bombs. When they went off the heat would cause the shielding at the rear of the ship to sublimate, and this ablation process would drive the ship. As I recall there were only two teensy problems with this: 1) even with the best shielding material available today, the intense heat from the detonation would still cause the maximum heat in the shield to occur at a depth greater than the surface (i.e. the shield would come off in great blobs instead of the slow steady ablation required for thrust) and 2) the amount of anti-matter required for the devices was only about a million times the total amount ever produced on Earth.
But apart from that it worked like a champ.
He took a duck to the face at 250 knots.
Actually it's too dense. At high speeds (significant fractions of lightspeed) a magnetic scoop acts like a very effective braking system in interstellar gas. A Bussard type ramscoop rocket could only be expected to reach about 0.12c even with highly efficient engines.
ah yes, it would have helped if i had read the ramscoop wiki rather than reading the name and guessing what it meant
. . . speeding through their neighborhood whilst "farting out a series of small fusion bombs."
They will come looking for us.
"Hey, Earthling, is this your flatulent spacecraft that fouled our air? We'd just like to return it to you, by chucking it at one of your major cities."
Schroedinger's Brexit: The UK is both in and out of the EU at the same time!
All the interesting places are either within reach now or too far to go there at ANY speed. What we really need is to find a way to autonomously survive in space for a long time.
no not at all u have it completely wrong
as u approach the speed of light
time at that velocity "slows" down
so if something is 6 light years away .5 light speed
and u are going
then it takes 12 years
so on earth 12 years would pass for it to arrive
however if u were on the ship it would take less then 12 years to arrive
in the extreme case if it was 6 light years away
and u were going light speed then on earth it would take 6 years for the ship to arrive
but if u were on the ship it might take seconds or no time at all
so the ship still moves and time in that frame of referance slows down but remains the same else were
... Edward Teller, the self-described father of the hydrogen bomb.
Other people who worked on the project tend to disagree with that title.
This ain't rocket surgery.
Please read up on Relativity sometime. There are a number of decent resources on the subject.
As is, you've just lowered the IQ of everyone who read this post....
Specifically...
The time dilation effect on an object is irrelevant to an observer at its point or origin. It WILL reach its destination, unless it's aimed wrong, or hits something really hard.
No, there is no such speed as you propose in your second conjecture.
Time dilation is a wonderful thing. It helps to shorten trips from the point of view of the traveller. But it doesn't change the trip at all from the point of view of an observer back at the start point.
Unless, of course, you're carrying one end of a wormhole with you on the voyage. Still doesn't change the voyage from the point of view of the observer back home, but can have some interesting effects later (if, that is, you consider time travel interesting, of course).
"I do not agree with what you say, but I will defend to the death your right to say it"
From your post, you don't make it 100% clear, but I suspect your understanding of time dilation might not be 100% accurate.
Say the distance from Earth to another star is 1 light-year, and we manage to accelerate a probe to an average speed of 0.1*c (1/10th the speed of light). For the sake of our thought experiment, let's assume the probe comes back, too, for a total trip distance of 2 light-years.
On earth, 20 years will have passed--it's a simple, easy "distance = rate * time" kind of thing. No time dilation to consider.
If you placed a clock on the spaceship, though, you'd see some time dilation effects on the moving clock. It would have experienced less than 20 years' worth of time passing. So if your Earth-bound clock and your space clock were perfect, and you synced them up before the trip started, they would be out of sync when the ship got back.
Remember, in your own reference frame, you don't experience any time dilation. The fact that the ship is travelling fast doesn't make clocks on Earth run slower.
If this isn't clear, go read the Wikipedia article on time dilation, and read the part where it talks about muons decaying as they travel from the upper atmosphere to the surface of the Earth. That's the easiest example to understand, I think, as long as you get how radioactive decay operates.
Hmmm, if we can't build lasers and power supplies like that on Earth, even given tens of years and billions of $, how soon will these be doable in outer space, with 100% reliability.
The old project Orion looked into atomic kabang propulsion. There were a few major showstoppers-- two dud impulses in a row and the pusher plate goes flying off into space. No way on Earth to test it. Which is kinda important for a device that has to be 100% reliable with no misfires.
Also the idea of discharging all those Joules in 10 nanoseconds is mighty ambitious-- just the inductance of the objects limits the rate of current rise to a whole lot more than that.
Dude...you've got what appears to be about a 50px kinda round thing in a crater, and your first assumption is a man-made biosphere? Well, I've got about a hundred pictures of alien spacecraft for you to look at then....
Seriously though, different planets have vastly different conditions, so it's no surprise you don't see things like this on Earth. I'd say it's essentially a sand dune. There's a _lot_ of similar formations on Mars. In fact, there's a few more on the string of pictures that original is from:
http://ida.wr.usgs.gov/html/m15012/m1501228.html
There's one in the first image, there's some somewhat similar phenomenon in the second and third, there appears to be one in the fourth, two in the fifth, and part of one in the sixth.
But it seems to me that going faster and faster you reach a point where although it might only take the probe x number of years to reach the star, on Earth it takes significantly more time. Therefore in the case of an unmanned probe, since it's time passage on earth that matters, at a certain point it's not desired to have the probe go any faster.
Actually, it's the other way round; from the point of view of someone on Earth, clocks on a rapidly moving spacecraft appear to go more slowly.
The actual time dilation factor, known as the Lorentz factor, is a simple 1/sqrt(1 - v^2), so for your vehicle going at .12c the difference in speed in clocks is 1.007 --- as you say, negligible. An observer on Earth sees a second metronome on the vehicle tick every 1.007 seconds.
This usually works out to your advantage. Passengers on a fast-moving ship will have less time to get bored, and there'll be less wear and tear on the structure. A sufficiently fast moving ship can cross the galaxy in subjective days (see A World Out Of Time by Larry Niven), although you're still going to get to your destination at least 100,000 years later. (You'd need a Lorentz factor of about 5000000 for that, which means you'd need to be travelling at 0.99999999999998c.) OTOH you run into severe navigational problems: such as the inability to dodge oncoming obstructions. Because, of course, the faster you go, the less warning you have of them...
Because they are all dead or going to be soon.
That was very interesting as I knew what was going on with the associated news stories that are planted but never knew it was so aptly named. I wonder , do the movie promoters pay the people to do the articles, or are they just lazy, and if somebody writes free copy for them, they jump all over it.
As far as the Nuclear drive, my brother ( who is a Nuclear Engineer ) and I have discussed it for over 30 years and though it might work, it could also end up buried somewhere with a message "Do not open until Christmas 40010".
If you read the proposal, you'll note that the proposed method of working in space seems to be that the rocket engine actually fires in two directions - first, it fires a very high energy plasma beam AT THE SPACESHIP, which, in the vacuum of space, turns the whole assembly into a Gigavolt capacitor. THEN the spaceship fires a GV proton beam back at the rocket. This proton beam then ignites a classic fission explosion (using Deuterium-Tritium), but "very small", and this DT explosion ignites a second, much more explosive Deuterium-only fusion explosion AWAY FROM THE SPACECRAFT. Repeat one million times per second, or as needed.
What could possibly go wrong?
If that's not exciting enough, the whole plasma/proton beam doesn't work on earth, so, hey, we use a disposable argon laser, which can generate a lot of power, but (sadly), is really inefficient. But wait, we can fix that! All you have to do is set off a small hexogene explosion around your rod of solid argon, and the laser will suddenly work at 80% efficiency. Oh, repeat that every microsecond or so.
Honestly though, if you can get past the insane energies involved, he's come up with a rather brilliant way to use readily available fuel (Deuterium, as opposed to Deuterium Tritium, which is hard to come by), and using a whole chain of events, make the process really efficient (i.e. you need a lot less mass to make all this work). And, since your main burn is fusion (which consumes the fission by-products), not a lot of radiation to speak of (oh, well, there are some pesky neutrons, but who doesn't like neutrons?)
Really? Could a magnetic scoop then be used for braking on a ship that used a different type of propulsion? Because more than half your propellant on an interstellar journey is required due to the need for braking when you get to your destination.
And yet the story's title refers to a 'starship'.
Yes, absolutely. It has been proposed as a part of laser-boosted lightsail missions to other stars. A full sized collector scoop would work in interstellar gas, but you only need a relatively small magnet if you are plowing through solar wind (er... stellar wind, since it isn't Sol?). A superconducting cable spooled out of a probe and given a current could be used as a braking system to decelerate at a destination star. I recall seeing an estimate somewhere that the peak deceleration of a relativistic craft like this hitting the heliopause would be about 12g, not comfortable but very effective and cheap way to slow down. Magnetic sails have also been proposed as a way to accelerate in the first place, but in that case you are limited to speeds less than that of the solar wind itself, so it is more suited to in-system missions.
According to google, it will take 50 years to get there, unless you're talking about a round trip. Personally, I'd just be happy with a space probe. The six years it would take to receive information from the post, and for it to receive commands, would be a pain in the ass though.
I do quite a bit. I ride the bus a lot, even though this is a great inconvenience. I would be happy to ride it if it were made convenient enough to do it. But the republican government here seems to like the idea of flooded coastal cities so they do not want to do anything to make public transit better. I use a clothesline (which is, astonishingly banned in places, which should be illegal!). I turn off lights. I dont run the AC unless its absolute unbearable without it. I recycle everything they will let me recycle. I use low wattage light bulbs. I cant afford solar panels but if the government did a solar panel installation economic stimulus they could cover the roof with them. Im doing everything i can think of.
Only 0.12c? Man, those things depreciate so fast.
The actual time dilation factor, known as the Lorentz factor, is a simple 1/sqrt(1 - v^2)
By your formula if v==1 you have an infinite factor....
I think the actual formula for the factor is 1/sqrt(1-(v**2/c**2)) where v is velocity and c is the speed of light, both measured in the same units. It's also the same for the relativistic mass of an object: Mv = M0/sqrt(1-(v**2/c**2)) where Mv is mass at velocity v and M0 is rest mass; meaning your mass goes to infinity as your velocity approaches c. Another way of looking at that is that the energy required to accelerate a mass, any mass, to velocity v goes to infinity as v->c.
But I haven't looked at this stuff in ages so I could be misremembering.
The tyrant will always find a pretext for his tyranny - Aesop
You don't have a keel in space. (http://en.wikipedia.org/wiki/Keel) The best approximation on earth would be a hot air balloon. In space you can't go faster than the solar wind without adding extra energy. You might be able to get a little by tacking between to planets but going to have some hard limits and it's not going to work with a magnetic solar sail.
I wondered why many fusion drive proposals are the slightly absurd mini-bomb machine gun kind, then realised perhaps it is because the Orion program really was that awesome in a nuclear-steam punk fantasy kind of way. However ludicrous it is to detonate 1000 nuclear warheads sequentially to reach orbit, you had to admit it'd be super-cool. http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) "This extreme design could be built with materials and techniques that could be obtained in 1958 or were anticipated to be available shortly after."
Yet these equivalent fusion-based proposals seem to be only plausible with some assumptions of technological advancement, rather than with assumptions that people wouldn't mind the irreparable damage to the earths biosphere.
I think the approach is all wrong by many proposals so far. Thing is, we can create and contain fusion right now, and you can do it your backyard (no kidding - see lower). I think a plausible fusion drive would be something like a Bussard electrostatic confinement based drive. Essentially you are accelerating ions to high enough velocity for fusion, but allowing some to escape by a neutral charged nozzle.
We don't have fusion reactors right now that break even in any practical generative fashion, however that is absolutely not necessary. Give up the need to generate power from fusion, for example use an existing fission pile to power the thing, and you start to get results. The high-velocity fusion products become a nice boost to your specific impulse, along with your exhaust velocity much higher than any Ion or VASMIR thruster for any high-energy fuel leaking out the rear.
Ditch the perfectionist science and apply practical engineering and tune the thing for efficiency. Go to the stars.
Interestingly, electrostatic inertial confinement in a hard vacuum doesn't even need reactor walls .
What makes this even more exciting is that hobbyists build electrostatic confinement devices, and even get fusion reactions. Oh, OpenSource too.
http://www.fusor.net/
http://en.wikipedia.org/wiki/Inertial_electrostatic_confinement
Now figure out how to make a drive out of a Fusor, strap some solar cells on it, and convince a private space launch company to put in orbit.
After logging in slashdot still does not take you back to the page you were on. It's been that way for 20 years.
Nope: http://www.iceboat.org/seasons/08-09/index1-29-09-1.jpg
"Modern iceboats designs are generally supported by three
skate blades called "runners" supporting a triangular or cross-shaped frame with the steering runner in front." http://en.wikipedia.org/wiki/Ice_boat#Modern_designs
Ice boats don't use a keel, but their blades do the same thing. Blades such as ice skates provide plenty of resistance in one direction much like a keel does on the bottom of a boat.