Workable Fusion Starship Proposed 260
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."
To save time & skip the pdf (Score:5, Informative)
See here:
http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) [wikipedia.org]
and here:
http://nextbigfuture.com/2008/12/micro-fusion-for-space-propulsion-and.html [nextbigfuture.com]
Re:Oxymoron? (Score:5, Informative)
Then a miracle occurs... (Score:3, Informative)
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.
Re:Ramscoop design? (Score:5, Informative)
Re:Human starship has already landed on Mars? (Score:1, Informative)
It's just the splash from an impact, probably a meteor. Imagine this:
http://www.core77.com/blog/images/drop_splash.jpg
but with the material property changing mid splash, possibly from the heat of impact.
Earth has them too, but we have more erosion due to weather:
http://www.geocities.com/zlipanov/impact_craters/impact_craters.html
Re:Relativity and time dilation make my head hurt (Score:2, Informative)
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
Re:Relativity and time dilation make my head hurt (Score:5, Informative)
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.
Kinda optimistic (Score:3, Informative)
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.
Re:Emphasis on 'Workable Fusion' (Score:1, Informative)
Re:Human starship has already landed on Mars? (Score:5, Informative)
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 [usgs.gov]
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.
Re:Relativity and time dilation make my head hurt (Score:4, Informative)
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...
Re:My memories of Edward Teller (Score:4, Informative)
The SF Chronicle columnist Herb Caen ran a story the next day saying that Teller was dressed as the angel of peace.
An interesting story about a man who was awarded the first Ig-nobel prize for peace: [improbable.com]
Re:My memories of Edward Teller (Score:5, Informative)
But the root of the problem between Teller and Oppenheimer was that Oppenheimer opposed the hydrogen bomb (fission/fusion) and Teller was all for it. That made Oppenheimer an enemy to Teller.
Teller, instead of leaving it as a difference of opinion as to whether such a powerful weapon was needed, went on the attack and set out to discredit Oppenheimer.
In the cold war it was pretty easy to make Oppenheimer seem subversive. The time was paranoid and anyone with a different opinion was suspect. Others set out to paint anyone as communist who they didn't agree with. Teller used it to his advantage to silence and discredit a rival.
Who knows if Teller or Oppenheimer was right. No fission/fusion device has ever been used in war. The only devices that have been used were the ones that Teller and Oppenheimer and many others invented.
However, a good person, a patriot, and someone who in spite of his own misgivings about the kind of weapon he helped develop, did it anyway and in so doing probably saved hundreds of thousands of American lives, had his own life destroyed because Edward Teller was on a personal quest for his own glory, his own stature, and his own place in history.
Edward Teller was an asshole. He took it personal that Oppenheimer opposed developing the hydrogen bomb and set out to destroy Oppenheimer for it.
Re:Woah (Score:3, Informative)
According to google, it will take 50 years [google.com] 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.
Re:from the article.. (Score:1, Informative)
He says, "Jigavolt." But we spell it,"Gigavolt."
Re:Relativity and time dilation make my head hurt (Score:3, Informative)
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.
Re:from the article.. (Score:3, Informative)
Protons and photons are different tho. I doubt your torch has a proton beam.
Re:Ramscoop design? (Score:3, Informative)
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.
Re:from the article.. (Score:3, Informative)
Gigawatt is correctly pronounced jiggawatt. And it's 10^9 watts, not 2^20.
Damn kids.
Re:from the article.. (Score:5, Informative)
Gigawatt is incorrectly pronounced jiggawatt.
Fixed that pronunciation fubar for you.
In English, giga is pronounced with a hard-g (as in "giggling girls give gifts"). Check the Oxford English dictionary, or any other English dictionary if you don't believe me. There was an attempt by the US NBS to redefine it to use a soft-g (as in "giant giraffe giblet gin"). http://en.wikipedia.org/wiki/Giga#Pronunciation [wikipedia.org] Thankfully, this hijacking attempt to a new and wrong pronunciation has been quite unsuccessful - I have worked with a great many American scientists and engineers over decades, and every one of them uses the correct hard-g pronunciation (so do the newsreaders on US TV, even). I work in R&D at a fairly large US-centric multinational, and I have yet to hear anyone pronounce giga as "jigga", not even MBA-handicapped marketing types. And it's really hard to imagine an executive saying "jiggabuck" instead of gigabuck - the audience would crack up completely...
If you want to pronounce giga with a soft-g, then please use French...
And it's 10^9 watts, not 2^20.
Indeed it is. Giga means 10^9 numerically, by definition. Alas, we are still fighting against recent attempts to hijack it to a new and wrong numerical definition.
Re:Ramscoop design? (Score:4, Informative)
Nope: http://www.iceboat.org/seasons/08-09/index1-29-09-1.jpg [iceboat.org]
"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 [wikipedia.org]
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.