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?"
Technological innovation (Score:3, Interesting)
We're definately a long way from the V2 when some simple hydrogen would be ignited, and then Bob would be your uncle.
Radiation can be beneficial and should not be feared. Of course there will be some potential for accidents and some minor radiactive pollution, but it's all worth it in the case of scientific progress. We don't have clean water or clean air, and you don't city inhabitants rioting, or do you?
Within our lifetime? (Score:5, Interesting)
I highly doubt it. As the last twenty years have shown, it's not the level of technology that determines how easily we get into space, it's the cost. And concepts such as these, while interesting to think about and develop, are ultimately going to take that many more decades to become proven.
Add to all this that the public would need a near-100% safety record in order to buy into a space tourism industry, and we're looking at more decades added onto the R&D and testing.
However, this kind of engine if developed properly COULD lower costs for putting satellites in orbit. So what's our benefit in the end? Lower satellite TV, telephone, and internet costs perhaps... But that's being optomistic.
But the design itself? Neat.
I Don't Know About This... (Score:-1, Interesting)
It will never happen (Score:5, Interesting)
The environmental whackos go nuts (and let slip the lawyers of war) when you launch a totally sealed reactor, can you imagine what they would do if you wanted to launch something that *gasp* released radioactive gasses into the atmosphere?
Comment removed (Score:5, Interesting)
Footfall! (Score:3, Interesting)
No radiation == Nuclear war (Score:3, Interesting)
the explosions clean and as small as they wanted.
This scared the shit out of them. They
puposefully did not pursue that line of
development for fear of weapons applications.
Re:Public Perception (Score:4, Interesting)
Re:Two Words (Score:5, Interesting)
The danger in the event of catastrophic failure comes solely from a possible dispersal of the fissile material.
We have reactor designs now that simply can not result in the reaction going critical. It'd actually be much safer now than it was in the 70s.
The only reason you're not allowed to talk about these things, even to educate the public, is the same reason you're not allowed to promote nuclear power generation. It's simply career suicide for any public official to broach the subject.
Provided the radiation from their rocket stays at what the specs suggest, this is no more inherently dangerous than the operation of any of the dozens of nuclear reactors currently commissioned in the united states. (not counting nuclear naval craft)
The public's irrational fear of all things nuclear is the only opponent that killed nuclear technology. It has nothing to do with actual science or statistical risk.
Re:Two Words (Score:3, Interesting)
Re:Orion was not a launcher proposal (Score:5, Interesting)
Re:Cant we just (Score:2, Interesting)
here's [wired.com] a nice general article on the subject.
There are other designs. (Score:5, Interesting)
Admittedly, the basic ground-to-counterweight-above-sync-orbit design has great potential. But there are other designs with less cost, extreme materials, and risk.
For instance: A section of cable in low orbit, spinning end-over-end so that each end periodically dips into the stratosphere at approximately the average local wind speed. Fly up to it, hook on as it goes by, and get lifted into orbit. Balance the momentum by bringing back a payload of space-mined material on the other end.
Build it so that if the orbit decays it will break up on reentry rather than crashing, keeping its own mass low enough that it won't create another Cretaceous event by spreading tons of red-hot debris throught the upper atmosphere if it comes in. (But if you get your spin right you can design it so that it tends to be pushed UP if the active guidance fails.)
Use a near-circular orbit if you want to lift a lot of payloads to near orbit (where you can use slower engines - like ion or light-sail - to achieve high orbit or escape), or an eliptical orbit for fewer payloads to a higher initial launch.
Lots of ways to do the active guidance:
- Control the spin with currents through the cable to electron guns and collectors at the ends working against the earth's mag field.
- Small attached light sails - For orbital elements, spin, attitude, AND killing vibrations.
- Ion thrusters ditto - and you can collect reaction mass each time an end dips into the atmosphere.
- Control, solar power plant, etc. at the center, which never enters the atmosphere. (Elevator/cable-crawler to get there from the ends.)
Lots of other systems are possible, too.
Re:Two Words (Score:4, Interesting)
Or perhaps my irrationality extends to thinking that when the pigeons around the UK's nuclear waste processing plants are so radioactive they would be classed as nuclear waste [greenpeace.org] themselves if they were inert. Internal contamination of the pigeons was found to be beyond safety levels set by the EC in the aftermath of nuclear accidents.
The problem with nuclear power is that it is made by humans and they have a habit of fucking up on a grand scale.
In theory it's all safe and dandy.
In theory, theory and practice are the same.
You should read some of the US Nuclear Inspectorate documents.
Our own inspectorate says [nirs.org] that "British Energy's downsizing has seriously compromised nuclear safety."
I could go on and on and on. But you know that already.
Re:Two Words (Score:5, Interesting)
There are two reasons for making it 91000km long when all you technically need is 35000km.
One: because you need a very large and unfeasible mass at the top if you want to balance 35000km of cable hanging below GEO with a weight located, say, 1 meter above it. You need a significantly smaller weight at the top if you want to balance it at 91000km.
Two: (which brings us back to our point of discussion) If you go as far as 91000km, you can slingshot payloads as far as jupiter and its moons [www.isr.us]. If you build even higher, at 140000km you can get as far as pluto.
Of course, the first thing you'd want to send to your destination is a pre-fabricated and spooled SE to deploy there, so you can send stuff back...
Re:Two Words (Score:2, Interesting)
The less people know about nuclear power the more afraid they are of it. I've done refuelings, defuelings, ion exchanger replacements, nuclear instrument detector replacements within the primary shield tanks, and a lot of nuclear decons and cleanups and have never had a fear or recieved much exposure. I don't recall the exact amount but it was under 3 rem total lifetime. The navy was not really worried about money though, the civilian world may be different.
Re:Two Words (Score:3, Interesting)
However, a space elevator on mars might be more feasible, (the moon would be the first option, but it spins too slowly for geosynch to work).
I think Charles Sheffield is probably closer to a workable idea.
For example, not an elevator, but stairs: big rotating disk satelites in orbit (where plane of rotation is along orbit and gravity well). You have to get to orbit yourself, but once there, you can gain altitude by grabbing a rotating disk, and riding it up. if you need delta v, start by grabbing the disk closer to the center, and then move outwards until you have the tangential velocity you need. Likewise, to descend, grab the disk on the outside, climb inward as you descend, and let go at the bottom.
In likelyhood, these would not be disks, but semirigid tethers, like gigantic bolas in space. As long as there is as much going up as down, it should run perpetually. Put several at different altitudes, and blast into space without using a rocket.
He also suggests having these in very LEO, so that tethers dip into the upper atmosphere. Minimize the air-resistance by having the tethers rotate as if they were gears wrt the atmosphere. This might let you use a ram-jet to rendezvous with the tether, skipping the whole "riding a stick of dynamite into orbit" aspect. However, the G forces would be a bitch: probably infeasable for humans w/o getting fancy (basically, you hop tether-spokes, getting just a little push from each one).
My favorite part of the article.. (Score:3, Interesting)
Re:Two Words (Score:3, Interesting)
"Exceedingly long" is a bit of an understatement. The length you're talking about (with just more elevator for a counterweight) is roughly 12 times the earths radius. Even with a counterweight system, the distance to geosyncronous is almost 6 earth radii. So, aproximately, you need a cable that completely encircles the earth when laid flat, and is strong enough to support its own weight when hung on end. I don't see that kind of strength-to-weight ratio being produced any time in the near future. And even if you produce the material, you've got to produce it in stupefying quantity, and get it all up to geosyncronous by some other means.
So I don't see a space elevator being economically feasible for a very, very long time, and certainly not before other launch means become so cheap as to eclipse it anyway.
Re:Public Perception (Score:2, Interesting)
A) breeder reactors. The US doesn't allow processing of spent fuel into safer forms because there's concern that the plutonium could be a problem. France does this with their spent fuel.
B) new designs. The currently operating reactors are very old designs. New designs are available that are far far safer than the already very safe reactors that we have. But, no new plants are being built, so we're stuck with the older designs.
There you go, I'm glad that you're a supporter of nuclear energy now. Get to work writing your congress critters to build the political support that is needed.
Re:Public Perception (Score:5, Interesting)
The kind of stuff we have to deal with from nuclear power plants is nasty. WAY nastier than anything which comes out of a traditional power plant.
Which is why we have to figure out how to get the stuff into space cheaply so we can jettison it into the sun. No geology to think about. No tectonics or water flow, just pure fusion energy cooking the bejesus out of our toxic waste.
What excellent Logic, Why aren't you rich? (Score:2, Interesting)
What about a tornado? Ever seen 1 house left standing in the middle of rubble that used to be a neighborhood? It happens.
Ever visited a debris field?
What's the difference between 30#s of open cell foam vs 30#s of a Lego contruction falling to the ground from 30,000? Does this explain the passport? Can I make you believe it? You can't have it both ways.
Oh, and according to 10/2000 IRS data Average taxable income was $43,172. The top %50 of wage earners pay %84.01% of all income taxes. Sounds like the "financially advantageous" aren't the ruling class. Soon, the majority of voters will pay no income tax, just watch.
The same people who vote yes for "Raise taxes on everyone but me" will prefer to have tax "refunds" for money they never paid, then to have space exploration, or scientific advances. Maybe I can agree with Trolling4Dollars that people can be made to believe almost anything.
Democracy alone is a group of 5 wolves and sheep discussing what's for dinner. It needs to be tempered with equal treatment, equal freedoms for all by Law.
Re:Public Perception (Score:5, Interesting)
Not all at once in one place.
Coal and Petrochemical based air pollution has killed tens of thousands to hundreds of thousands at younger ages than they would have otherwise died, and cars and tobacco have killed TENS OF MILLIONS of people this century, and yet you think that the HUNDREDS of reactors in current operation in North America whom haven't killed a SINGLE HUMAN BEING yet - are a bigger badder threat.
Stupid dumb public. And they bitch like hell when we try and keep their asses in High School all the way through until grade 12.
Re:Two Words (Score:5, Interesting)
"going" critical: All nuclear reactions (not nuclear decay) are critical. In order for a self sustaing nuclear to occur, a critical mass of fissible material must be present. If the mass falls below critical the reaction will extinguish. Decay will still occur and generate heat, abliet much less.
Melt-down: A melt-down happens when a reaction goes out of control and produces sufficient amounts of heat to cause the core the liquify (melt down). When a core melt-down happens, there is not a damn thing on this planet (that I know of) that can the molten (and getting hotter by the second) glob that used to be the core.
It has been theorized that if this happens, the molten core will burn through the earth until it reaches water. Upon contact with the core the water will turn into steam and create what is in effect a steam cannon, blasing the core back up the hole and showering bits of the core for miles around.
On irrational fears (Score:2, Interesting)
1)Many governments around the world, including the US government, put humans in unsafe radiation environments, which they knew to be unsafe, either to test the effect on the humans or because they didn't care. A significant number of people in the US military died because of this. There was a show on Nova about the Bikini Atoll nuclear tests, where the sailors watched the explosions from the decks of their ships. Many of those died.
You might say that this is all in the past, but look at how the Gulf War Syndrome patients have been treated by the US and UK governments. The symptoms are there, but nobody knows what causes them and so they just deny the effect and keep exposing more and more soldiers to whatever it is that causes the illness.
Look at how the US and UK governments deny the harmful effects of depleted uranium. DU munitions are not very radioactive, but the dust that is released when they burn finds its way into the human body very easily. Once inside, it can not only irradiate the body but also have other toxic effects associated with heavy metal. The military's OWN practice is aggressive decontamination of anything that is exposed to DU ash, but this is denied in official reports.
So in the absence of reliable independent reports, it is very difficult to accept these assertions of safety.
2)If only we had a way to quantify the danger posed by radiation we might not have this problem. However quantify it we cannot. Because of the random nature of radiation damage, it is very difficult to study. We know the effects of large doses fairly accurately but small doses require large population samples, and it is difficult to expose large populations to controlled doses of radiation.
The greatest danger posed by small radiation doses is genetic damage that can lead to cancer. We don't know how cancer works or how the human body normally prevents it. We don't know what enables humans to survive the genetic damage caused by the natural radiation environment. We can't even measure genetic damage. We know that USUALLY, small doses of radiation have no effect but don't know why SOMETIMES they do or what is a safe dose.
At its root, the fear of low level radiation is similar to the fear of other carcinogens. There is no way to quantify or track exposure because just ONE unlucky mutation could lead to a deadly cancer, but we have no idea which mutations these are or how to find them.
So what I would say is that those people who want to talk about irrational fears of the population should rationally counter some of these points. Most people who are pro-nuclear cannot counter them. They don't know anything about how radiation exposure is measured (except that it's in REMs), what the natural background radiation is in REMs, how many Curies are contained in coal ash, etc. etc. etc.
Re:Global Slowing - not significant enough to worr (Score:3, Interesting)
Incidentally, the earth has an angular momentum of about 9e33 kg-m^2/s (I might be off by a factor of two), for all those interested. For comparison, a 6000 pound (about 3000 kg) truck moving 30 m/s (about 70 mph) only has an angular momentum about the earth center of about 6e11 kg-m^2/s. A 10000kg spacecraft moving at 3000 m/s at 30000 km altitude, though, has 1e15 kg-m^2/s. Launching one spacecraft - just ONE - at this rate will take off about 4e-12 seconds of earth rotation per year. So, yeah, I guess that's small, but it's real!
Re:Two Words (Score:3, Interesting)
Pure carbon nanotubes have the required strength-to-weight ratio. The only question is how long before we can develop a composite that binds CNTs together into a material that retains enough of the strength of pure CNTs. Steady progress is being made. Keep an eye on LiftWatch.org [liftwatch.org] for regular updates on this and related techs.
Re:Public Perception (Score:1, Interesting)
There are bad places to build underground repositories. From a geologists perspective, for example, Yucca Mountain isn't that great. You only need a quick glance at a geologic map to make your your heart skip a beat -- all those lines crisscrossing the area are mapped faults that were active in recent geologic history. It's also only 1/2 step away from being an active volcano field, climate there may be highly variable over relatively short spans of geologic time, and the design of the repository makes it susceptible to ground water related problems.
Among better ideas: do bury in very deep boreholes in continental crust that has been stable since at least the precambrian, far below the top of the water table -- the deeper the better -- and perhaps below a layer of impermiable strata. Water becomes scarce at extreme depths, circulation is limited (high pressures affect the permiability & porosity of rocks), the water carries very high concentrations of salt & dissolved ions (so it's not useful as fresh water because it's not fresh at all), and fractures that might allow water movement heal themselves relatively quickly due to the high heat and pressure.
There has even been research involing the use of heat generated by short-lived radionuclides high level waste to melt a very small volumes of granitic rock around the high level waste, which would shortly cool to form a very durable casket to last hundreds of millions of years. There are other apparently viable strategies as well. They're all alike, however, in that it would be all but impossible for stored waste to be recovered by people whom we don't want to have it, and unlikely for the waste to migrate from the point of disposal in any way that would likely afftect anything near the surface of the Earth for very long time periods.
The point is, geologic sequestration can work and that it is a desirable approach because if done correctly it guarantees the stability fo the waste for very, very, long time periods.
The alternatives of leaving the waste at the surface for geologically significant time periods, or trying to blast them in to space, don't seem so viable.
"Thrust to Weight Ratio" != Isp (Score:3, Interesting)
Specific impulse is a clunky way of stating exhaust velocity.
It has nothing to do with a thrust to weight ratio.
In fact, ion motors, and proposed fusion motors (google for "inertial confinement fusion" and "magnetic confinement fusion") have a very high Isp (3000 seconds for ion motors, up in the mid 100,000 seconds for fusion motors) but generate very low thrust.
The stream of particles these motors produce move very quickly, but there aren't a lot of them.
Why is a high specific impulse a Good Thing?
Recall Newton's Third Law of Motion: Every reaction produces an equal an opposite reaction. Simply put: In a rocket, the momentum of the stuff the motor accellerates out the back ("reaction mass") translates into forward momentum. The faster the stuff you toss out the back, the more bang the buck you get out of that mass.
A higher exhaust velocity means you need less reaction mass, in terms of the percentage of your starting total mass, to achieve the same changes in velocity.
Here's the rocket equation:
M(f)+M(0)
--------- = e ^ (Vd/Vex)
M(0)
M(f) = mass of fuel
M(0) = mass of space ship w/o fuel
e = natural log number, about 2.718 is fine for these purposes
Vd = desired velocity change
Vex = exhaust velocity
The "velocity change budget" for a fast trip to Mars is about 20 kps. The exhaust velocity of a good chemical motor is about 5 kps. If you plug these numbers into the above, you find you need a mass ratio of 54:1 for your Mars trip. That is, 53 tons of fuel for every ton delivered to Mars orbit. With a nuclear fission rocket motor with a exhaust velocity of 10 kps, the mass ratio is more like 7:1.
Stefan " I'm not a rocket scientist but I play one on TV" [io.com] Jones
Re:Public Perception (Score:5, Interesting)
Sometimes. Sometimes not. On my college campus there was a small (6 MW IIRC) nuclear reactor, used for instruction in the Nuclear Engineering courses. I took a tour of it once (I was in Chem E, not Nuc. E, so I never got to do any actual work with it) and heard an interesting story from one of the professors there.
They were doing a scheduled test one weekend of some of the safety systems, so they were expecting some alarms going off. One of the students walked in the door, and suddenly all of the radiation alarms went off. They got out their gear and traced it down to the student who had just walked in. Specifically, they tracked it down to his head. So they got a 55 gallon drum of water and started washing his head. After a little bit of that, the water was radioactive, but his head wasn't. After they were finished, he told them what he had done. He had gone to WalMart and bought a wick for a coleman propane lantern. He took some scisors and cut it up into fine pieces, and sprinkled it on his head (The wicks are coated with a chemical which gives it a cleaner, whiter light, and also happens to be slightly radioactive).
The amusing thing about all of this is the contrast between normal use and a nuclear power plant. 99.99999% of the coleman wicks that are sold are thrown away in the trash (or littered with near campsites) because they really are not a hazard to anyone, and no sane person would say they are. However, because he brought the one he bought into a nuclear power plant, the plant had to classify the whole 55 gallons of water as potentially dangerous nuclear waste, and they had to spend a fairly large amount of money to have it disposed of "properly". How much of the nuclear waste that's being encased in concrete and buried under miles of rock is more (or less) dangerous than what you can buy in the local WalMart?
Why nuclear power is not common (Score:3, Interesting)
Back in the 50's when nuclear power was first proposed, people talked about having electricity too cheap to meter. The thing they did not consider is that a nuclear power plant costs much more to build than a coal/oil/natural gas plant. I want to make sure everyone understands why.
First of all, the radiation given off by fission destroys inorganic materials just as happily as it destroys human tissue. Very high quality metal must be used in all parts of the reactor to prevent degradation and to prevent it from becoming highly radioactive. This is even more of a problem in fusion reactors which have a much higher flow of neutrons, and in those, the only solution will be to replace the pieces every so often.
Second, the plant must be extremely highly reliable. One reason for this is draconian public safety regulations. However you have to keep in mind that even an accident that is contained within the plant and poses no risk to the public (a la Three Mile Island) can still destroy the reactor and put the plant out of commission.
This is true because of a property of the nuclear chain reaction. Dropping all of the control rods (scramming) does not instantly shut down the reaction in the way that dousing a coal fire would extinguish it. The reactor will continue to produce heat for around an hour after it is shut down. This means that it must be cooled for that hour, otherwise it will melt and flood the building with radioactive chemicals. The Chernobyl accident was caused by an attempt to test what happens if the cooling system is disabled.
So the system has to be very highly redundant, in part to protect the public, but mostly to protect the plant.
The last problem is that if the coolant is radioactive, you can't just call in a plumber to fix the leak as you might in a coal plant. See the movie K-19 Widowmaker for the effects of radioactive coolant on humans. You better make damn sure that system doesn't leak in the first place.
So the plants are expensive. This means you want economy of scale and build one large plant instead of many small ones. This means you don't want to build these plants in the Midwest where that much power just isn't useful. You want to build them near population centers. That explains why there is no nuclear power in sparsely populated places.
The other thing is that even though uranium is much cheaper than coal per joule (because you need so much less of it), the cost of the nuclear plant makes the whole process expensive enough that it has to compete with coal for the market. This means that in places where coal is cheap (as in the United States) building nuclear plants is only sensible up to a point. As the nuclear plants drive down demand for coal, the coal gets cheaper, so there is a natural feedback mechanism.
In the United States, we are a little bit below the optimal balance. We could economically build more nuclear plants but not that many. This difference is in part accounted for by the public perception of nuclear power.
It is also accounted for by the fact that it takes ten years to build a nuclear power plant, so if you have an energy crisis NOW, building a nuclear power plant is no good. California had to go with building natural gas power plants after their energy crisis because they are cheap and fast to build. Natural gas is more expensive but that's life.
Now it should be clear why France and Japan, two countries that use nuclear power for most of their needs, are able to do so while the US cannot. It has nothing to do with progressive governments or the lack of environmentalists. It is simply that France and Japan are small, densely populated countries (compared to the US) that have expensive coal (compared to the US). So they have a lot of nuclear plants (compared to the US).
I hope that explains a few things. Now as
Re:There are other designs. (Score:3, Interesting)
Which is why one operational mode is to balance the mass, momentum, and energy by using it to DEcellerate an equal amount of space-mined material on each lift. You use it to exchange a spaceplane full of passengers for a spaceplane full of space-manufactured goods, or a spaceplane full of returning passengers for one full of tools.
But that's not the only mode. If the device is sufficiently masive and your launches sufficiently rare, you don't need to do a matching down-trip now. You can let the orbit decay somewhat due to launching your ship. Then you pump it back up later with the same ship returning from its mission. Or you can pump it back up using SLOW thrusters, lightsails, or the earth-field electric motor effect over a period of weeks.
Electric-motor pumping it with the earth's magnetic field does essentially the same job as using electric-motor elevators in a more conventional skyhook design - working against the earth's angular momentum for your orbital thrust. It just does it more slowly than a physical connection to an anchor point in the crust. And it requires you to use a space-based source of power for the motor, rather than an earth-based generating plant. (Unless you use microwaves or laser light to send ground-generated power up, of course. But why bother when you have all that sunlight?)
The important part of ANY skyhook design is to do the FIRST HALF of the launch - getting from the surfact to near-earth orbit - where the payload must be accellerated VERY RAPIDLY to overcome the one-g field and atmospheric friction. Once you're out of the atmosphere there are lots of better-but-less-immediate ways to go the rest of the way.
A spinning-cable skyhook lets you use relatively efficient engines burning atmospheric oxygen in a vehicle generating airfoil-based lift (rather than rockets spending their first g of delta-v on the gravitational red-queen's race) to get you near the atmosphere/vacuum transisition, then the energy-balanced skyhook to yank you above it. It's far more efficient than even self-contained spaceplanes and gives you most of the advantage of a beanstalk at a tiny fraction of the cost (though with somewhat increased complexity).
Re:Two Words (Score:1, Interesting)
Re:Two Words (Score:3, Interesting)
Not only that, but the lunar module impacted at a very high velocity (escape velocity IIRC) compared to launch aborts, and the RTG *still* survived. Pretty good test, IMHO.
SB