Clean Nuclear Launches? 838
AKAImBatman writes "When it comes to launching millions of pounds of material into space, nearly everyone knows about the Orion Project. Blow up a series of nuclear bombs under your dairy-aire and ride the explosion on up. Unfortunately, the Orion spewed out so much radiation that it just wasn't a feasible launch option. If we want commuter trips to space, we're going to have to find another way. Well, it turns out that NASA's been doing quite a bit of research on Gas Core Nuclear Rockets, an ultra-powerful nuclear rocket that puts out almost no radiation. This research has spurred a fascinating new generation of ideas on reaching the cosmos. Could inexpensive cruises to the moon happen within our lifetimes?"
Full text! (Score:1, Informative)
Project Orion originated at General Atomics in San Diego, a company (later a subsidiary of General Dynamics) founded by Frederick de Hoffman to develop commercial nuclear reactors. It was de Hoffman who persuaded Freeman Dyson to join Taylor in San Diego to work on Orion during the 1958-59 academic year.
Ulam and Everett's idea was modified so that instead of propellant disks, the propellant and bomb were combined into a single pulse unit. Plastic was chosen as the propellant material, not only because of its effectiveness in absorbing the neutrons emitted by an atomic explosion but also because it breaks down into lightweight atoms such as those of hydrogen and carbon which move at high speed when hot. This approach, in tandem with the pusher plate concept, offered a unique propulsion system that could simultaneously produce high thrust with high exhaust velocity. The effective specific impulse could theoretically be as high as 10,000 to one million seconds. A series of abrupt jolts would be experienced by the pusher plate, so powerful that, if these forces were not spread out in time, they would result in acceleration surges that were intolerable for a manned vehicle. Consequently, a shock absorbing system was devised so that the impulse energy delivered to the plate could be stored and then gradually released to the vehicle as a whole.
Various mission profiles were considered, including an ambitious interstellar version. This called for a 40-million-ton spacecraft to be powered by the sequential release of ten million bombs, each designed to explode roughly 60 m to the vehicle's rear. In the more immediate future, Orion was envisaged as a means of transporting large expeditions to the Moon, Mars, and Saturn.
Taylor and Dyson were convinced that chemical rockets, with their limited payloads and high cost, represented the wrong approach to space travel. Orion, they argued, was simple, capacious, and above all affordable. Taylor originally proposed that the vehicle be launched from the ground, probably from the nuclear test site at Jackass Flats, Nevada. Sixteen stories high, shaped like the tip of a bullet, and with a pusher plate 41 m in diameter, the spacecraft would have utilized a launch pad composed of eight towers, each 76 m high. Remarkably, most of the takeoff mass of about 10,000 tons would have gone into orbit. The bomb units ejected on takeoff at a rate of one per second would have yielded 0.1 kiloton; then, as the vehicle accelerated, the ejection rate would have slowed and the yield increased, until 20-kiloton bombs would have been exploding every 10 seconds.
It was a startling and revolutionary idea. At a time when the United States was struggling to put a single astronaut into orbit using a modified ballistic missile, Taylor and Dyson were hatching plans to send scores of people and enormous payloads on voyages of exploration throughout the solar system. The original Orion design called for 2,000 pulse units, far more than the number needed to reach Earth escape velocity. In scale, Orion more closely resembled the giant spaceships of science fiction than the cramped capsules of Gagarin and Glenn. One hundred and fifty people could have lived aboard in relative comfort in a vehicle built without the need f
in case/when the IIS server gets /.ed.... (Score:5, Informative)
Opening the Next Frontier
by Anthony Tate
Part 1: The Frontier Spirit
America loves its legends. George Washington in Valley Forge. The Wild West. World War II. The Man on the Moon.
But lately, it seems the legends have stopped.
Sure, we have the Internet to play with now, and computers are changing the world in ways we can scarcely grasp as of yet. The Soviet Union is no more, and despite our current travails with terrorism, a certain comfortable familiarity has us in its grip.
Where is the next legend? Where is the next frontier? Or are we just going to go comfortably off into retirement?
If the 'entertainments' of the kids these days are any indication, no way.
Extreme sports, fun little things like 'base jumping' and other diversions indicate that the next generation of Americans are harkening back to their roots in a big way. America is ready for the next challenge, refreshed, revitalized, and shaking off old fears and inhibitions.
But what could have caused our recent doldrums?
Why have we not gone back to deep space, that logical 'Final Frontier,' for so many years after Apollo? I believe it was a confluence of several factors, most of which have now passed, that caused us to huddle close to the bosom of Mother Earth for these past decades.
Part 2: What went wrong.
To be blunt, it was the 70's.
After the turbulent change of the 60's, the 70's were just a hard time for America. The Cold War dragged on and on, no end in sight. Vietnam was a horrible, bloody mess, deeply misunderstood to this day, and bitterly divisive even in the aftermath. Watergate destroyed the faith of millions in their own government. The Oil Embargo shocked the economy as well, causing the nightmarish condition of 'stagflation.' Cultural upheaval became the norm as gains in civil rights were cemented into place.
With that litany of bad news, there is little wonder that the public lost interest in space. When you are scared for your job, your children, and whether or not your paycheck next year will still cover the rent, idealism and exploration goes out the window.
Also, lets be honest, landing on the Moon in the 1960's was an incredible feat. That entire rocket, the whole plan, was designed, built, and flown using less computing power than you have in your PC. Genius level effort was used to make that program possible, and the chance of disaster was perilously high, even by the comparatively relaxed standards of the day. In other words, Saturn was ahead of its time, by many years.
If it wasn't for the Cold War imperative to beat the Soviets, we'd probably be looking to go to the Moon right about now, all things considered.
Add in the fact that science itself was throwing up massive roadblocks, and there is little surprise to be had from the seeming 'retreat from space.' The rocket fuel used in the Saturn V moon rocket at launch was BETTER than the rocket fuel used to launch the Space Shuttle today. Why is that? Well, it's simple: The chemical fuels used in the Saturn V are among the best fuels that chemistry allows. Science is remarkably inflexible: unlike in the movies we can't just 'whip up' better rocket fuels. Chemistry is pretty stubborn that way.
So, exploring further in space was not important to the country while we had other problems to deal with, and making rockets better than the SaturnV was pretty much impossible.
So, NASA went sideways for a while. The Space Shuttle is a remarkable system, but it is at its core a compromise. So while it is good at many things, it is great at nothing. But nonetheless, the Space Shuttle kept America in space, and slowly we were building momentum to move forward once again away from the Earth.
Then Challenger blew up (and now we've lost Columbia and her crew as well).
Now, to the doughty folks who made Apollo fly, that disaster would have been a learning experience, and development would have continue
Launches? (Score:5, Informative)
Dairy-aire? Derriere. (Score:4, Informative)
2 entries found for derriere.
derriere also derriere ( P ) Pronunciation Key (dr-ar)
n.
The buttocks; the rear.
Also:
No entry found for dairy-aire [tripoli.org].
It's like the difference between a segway and a segue. One is a normal word used in English, the other is an amalgam coined for some other purpose.
Re:last link /.'d already (Score:3, Informative)
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Re:Two Words (Score:5, Informative)
One of these things is not like the other.... (Score:5, Informative)
Re:Two Words (Score:5, Informative)
Look at some of the more recent space elevator designs [www.isr.us].
Basically, the elevator would be made out of a ribbon so light and with such a surface area that it would fall to the earth like a peice of paper. At least that section of the ribbon that doesnt burn up while entering the atmosphere.
A space elevator isnt like the ones you read about in Kim Stanley Robinsons Mars trilogy.
Re:Public Perception (Score:2, Informative)
A bit of physics would help to sort out the harmful radiation from the helpful radiation.
If radiation had feelings, they would be hurt.
Wrong: a disasterous shockwave is IMPOSSIBLE (Score:2, Informative)
Sorry to disappont the Kim Stanley Robinson fans, but this simply isn't the case.
Even if the SE breaks at halfway, we're not going to get a catastrophic shockwave. You have to consider the material to know how it's going to behave. First, this thing is VERY light weight. It's also VERY thin. Not much displacement means not much shockwave. Not much weight means it will be easily dampened by the atmostphere.
After a break, yes, the end near the break will start off at a pretty high velocity because of the tension that it was under. But -- and this is part of the design -- carbon is combustible and will BURN UP in the atmosphere if it's travelling too fast.
There is NO WAY that a falling CNT ribbon will be catastrophic, even to those right underneath it.
You'd be better advised to worry about payloads that might fall off it. But even these would be engineered to have re-entry systems for just such an eventuality.
--
LiftWatch.org [liftwatch.org] - Space Elevator News
Re:Two Words (Score:5, Informative)
Here's where education is important. Do you understand what "going critical" is? Very specifically, it's a build up of heat from a "melt-down". (A "melt-down" being when a nuclear reaction gets out of control and produces excessive amounts of heat.) Usually reactors are highly contained units. All that extra heat builds up pressure that has to go somewhere. Thus the containment itself can produce a big explosion. Still, it's more like an industrial boiler exploding than a nuclear bomb. The only radiation is from any radioactive material that gets ejected. (Usually not much, and cleanup isn't too large of an issue.)
Now in a nuclear rocket, specifically a Nuclear Thermal Rocket, heat is what we want. Assuming the reaction goes beyond the safeguards (which should be impossible), you can simply increase power to the turbopumps and flow more fuel through the reactor. This will end up providing far more thrust than originally intended (read: serious KICK IN THE PANTS), but the melt-down will not become critical.
Re:Two Words (Score:4, Informative)
You neither need to grow a 35000km buckytube, nor do you need to reach a 100% CN-loaded ribbon.
Composites will be made with a higher and higher CN loading, and once a certain percentage is reached (feel free to check the NIAC 2 paper [spaceelevator.com] which draws this line quite clearly), you'll have elevator-worthy material. At the rate CN loading in composites has been increasing in the past decade or so, we should [hopefully] have elevator-worthy material in about 2 years.
Cheers.
Re:Two Words (Score:5, Informative)
Because the Turbopumps are in a different part of the craft. Did you read the article? Turbopumps push a steady stream of fuel from the tanks to the core where the core heats the material to PLASMA. Don't suppose you know how hot plasma is, do you? I'll try to explain it this way: The reactor is DESIGNED to run under what would be considered melt-down conditions in a normal reactor. More heat from the reactor means more energy transfered to the fuel, which means more thrust. If you cut the thrust, the backend of your rocket will melt and fall into the ocean. The ocean will provide a new moderator that will stop the reaction completely. The reactor will still be contained in its shielding, so little to no radiation will be exposed to the underwater environment. (Not that underwater volcanos don't already put out enough of that.)
But that's all besides the point, the point was, if it DID go critical, and it DID explode, that would be inherently WORSE then if the shuttle just blew up.. You said:
"Thus the containment itself can produce a big explosion"
Doesn't that one statement agree with what I'm saying?!
No. Because you took two different designs and equated them. Nuclear engine != Nuclear powerplant. A powerplant exists under pressure. It can only operate within certain heat tollerances before a boiler explosion (and it IS a boiler explosion) happens.
A nuclear engine exists in a state where ALL the heat is being transferred to fuel. More heat is actually a GOOD thing in the engine as it provides more thrust. The problem with a runaway reaction (which doesn't just happen by itself, sorry to say) is control. You're now sending your astronauts on a trip to the moon when all they wanted was to achieve orbit. That's a problem. In many ways that's less of a problem than a failed chemical booster which would simply explode, or fail, or just about anything else. Assuming the craft survived the initial failure (not likely), a chemical booster helpfully drops you back to Earth at terminal velocity, on an unknown vector.
With a little education, you should be MORE scared of chemical rockets than nuclear ones.
Re:Public Perception (Score:2, Informative)
Well, any coal-burning plant accident that kills even one person will have been more of a catastrophe than TMI.
Your facts are outdated (Score:2, Informative)
You need to read about more recent deployment plans for the space elevator. Start here [liftwatch.org].
Things you got wrong:
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LiftWatch.org [liftwatch.org] - Space Elevator News
Re:Two Words (Score:3, Informative)
You're missing something, then. It needs to be strong in the radial direction (resist push/pulls) It has no need to be thick whatsoever.
It will be wide at the top, but still not thick. It's a ribbon, not a cable.
It'd burn up in the atmosphere. Too much surface area, and not enough thickness to insulate the heat.
Re:Two Words (Score:5, Informative)
That is right, the US self-destructed a rocket right after launch and the RTGs survived intact, were recovered and the material was in good enough condition to be reused.
Nuclear propulsion is our ticket off this rock. The only thing in our way is ignorance of the technology.
Oh, and yes, IAARS.
Re:New idea for causing massive damage! :) (Score:4, Informative)
In fact the WTC towers were capable of (mostly) surviving 9/11, if only there had been better fire retardants on the supporting columns - which had been recommended repeatedly, particularly after the 1993 attacks. Nobody said that was a worry for another day, either, they just didn't want to pay for it.
So, bad example.
-Graham
Critical (Score:2, Informative)
Reactor use delayed neutrons to be controlled critical. Reactors can be very well controlled in this range. It is when a reactor/bomb/tank etc becomes critical with prompt neutrons that things become problematic.
That said the gas fuel reactor is an excellent design that should be put into operation when a few more issues are worked out.
Re:Public Perception (Score:2, Informative)
Re:Two Words (Score:3, Informative)
part(s) of the core of Chernobyl 4 melted down. [kyoto-u.ac.jp] (though i'm not entirely sure if this was due to a runaway reaction producing too much heat, or due to external heating from the graphite moderator fire started by the steam explosion. nor am i sure which would be the worse thing.)
what basically happened was that the molten core material had to melt its way through its containment (what there was of it). in the process, of course, it became diluted [usnews.com] with molten whatever-it-had-just-touched matter. this can't go on forever without the core matter going subcritical; the "china syndrome", melt-through-the-planet scenario presupposes some mechanism for the fissile material to stay homogenous and concentrated, and i for one can't think of any.
Re:Two Words (Score:3, Informative)
As far as meltdowns go, you forget one thing. As the core melts surrounding materials, it mixes with them and this causes a certain amount of moderation, slowing down the nuclear reaction. Many new reactor designs incorporate moderating materials directly into the containment vessel so that even under a full and uncontrolled meltdown, the moderation caused by these materials is enough to slow the reaction and prevent a breach. New reactors can survive an full catastrophic failure of all systems simultaneously and still not allow a breach of the containment system.
Re:I can imagine the protests now... (Score:3, Informative)
My preference is to argue from the standpoint that these activities are worth the risk. Attempting to convince people that serious consequences are impossible is a fools errand. Making them realize what cowardly little twits they are seems like it ought to be far more productive. That craft did not represent enough danger, in my opinion, to outweigh the value of the mission. I would still say that after looking at pictures of children with cancerous thyroids after the ship self-immolated to dust over a Florida suburb. Risk is necessary.
My suspicion is that Nuclear technology will get nowhere in the United States until people stop calling it that, due to the huge political movement to make sure no one uses anything with "nuclear" in the name, regardless of the safety, degree of research, or degree of oversight. I'd propose scientists start using some other word, like "happytronic", but this would probably be seen through as "hollow PR from the nuclear industry". (That's another thing. People promoting nuclear energy are often derided as "Nuclear Industry Shills", but people attacking it are never successfully labelled as "Coal Industry Shills", despite the fact that's who they're primarily helping. How is this?)
Nuclear power is more expensive (in the US) than existing alternatives; coal and more recently, natural gas. That's a fact borne out over half a century of operating plants of all types. I think this is the real explanation for the stall in nuclear power generation in the US.
There is a term in the nuclear power industry; SCRAM. Supposedly it means "Safety Control Rod Axe Man," and is the designation for the guy who is supposed to cut the rope that drops the control rod(s) into the core to halt the reaction. Modern reactor cores involve no rope or axes, yet the term lives on because the basic physics are no different. The reality of operating a modern reactor is that SCRAMs are common; for all sorts of reasons operators find themselves in situations where it's imperative that the reactor stop RIGHT NOW. They smack the proverbial Big Red Button, if it doesn't smack itself automatically, and control rods rapidly descend into the core and stop the reaction. Nuclear "events", such as SCRAMs, are recorded by the NRC. The most recent reported SCRAM [nrc.gov] was Monday, at 12:30 ET, about 27 hours ago...
Speaking for myself, that's just too much drama. Fission cores in nuclear reactors are no joke. They are large piles and they do represent a large potential calamity. We've never, ever witnessed that potential. Chernobyl, much less Three Mile Island, did not approach the worst case. I don't have enough faith in humans and machines, operating over many decades amidst political and technological change to really believe in my heart of hearts, that existing power reactors are safe. I cannot tell you how much it pains me to admit that.
This is the primary promise Fusion offers IMHO-- because oh, it isn't nuclear, it's "Fusion", right? Which means people will actually use it.
The physics of sustaining a Fusion reaction might provide for inherent safety; without a huge amount of input power the reaction cannot be sustained. Fission cores can melt down due to residual heat even after you stop the reaction (this is essentially what happened to Reactor 2 at Three Mile Island, for example.) Fusion is a whole different kettle of fish.
Re:Two Words (Score:2, Informative)
Maybe civilian plants are different, but for us, "going critical" is akin to setting the cruise control in your car. "Going super-critical" means you're having an up-power transaction, like stepping on the gas.
Generally speaking, I don't get too concerned when someone sets cruise to 55mph.
Going "prompt" critical, howerver, is a whole other issue. It's more or less when you have a several decade per minute power increase in about a second. It's uncontrollable. But you'd probably SCRAM out anyway. So you still won't have a release of fission material to atmosphere (let alone to your secondary system). Also, you'd really, really need to fuck up pretty hard to get a reactor to go prompt critical.
Re:"Thrust to Weight Ratio" != Isp (Score:4, Informative)
Think of the nuclear rockets as ultra-powered chemical rockets. Somehow we've managed to get the hydrogen to higher velocities than was previously possible with a simple chemical reaction.
BTW, Force = Mass * Velocity2. So more velocity at the expense of mass will improve our thrust. Obviously there's an upper limit to how much velocity we can obtain, so we need to throw more mass. But if you consider that a nuclear engine can throw the same amount of mass as a chemical engine (minus some "light" electrons lost in plasma conversion), then we have greater overall force coming from our nuclear than our chemical reaction. Although, to be exact we're both throwing and pulling against the plasma. First we create the plasma which is exhausted (throwing). Then we use EM accelerators to pull on the plasma on the way out. The "pull" transfers that much more energy from the mass to the craft.
That being said, I am NOT a rocket scientist, so I can't give you exact numbers. However, the article I linked to in the story does give quite a few numbers, and a bit of googling will produce even more exact numbers. (I've seen some right down to the force per molar mass on usenet. Since I wasn't going to be building one of these things myself, my eyes kind of glazed over at that.)
YHABT (Score:2, Informative)
Don't waste your time.
Re:Two Words (Score:2, Informative)
Have you ever had an X-ray of some part of you taken? Noticed the lab coat the technician that operated the x-ray machine was wearing? If it was in a nuclear power plant, it would be designated as a _medium_ grade radioactive waste.
And the guy just keeps on wearing it. Irrational, innit?
Re:Two Words (Score:3, Informative)
And raised mutations by 600% because of radiation.