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I am in agreement with RobS. Most cargo transport will be driven to the absolute lowest prices possible, which I think will rule out a traditonal cycler. To many stages and far to much equipment to truly be cheap for cargo transport. RobS is right that for general cargo transport Solar Sails will likely become the cheapest option.
The solar sail has many advantages over other methods. If travel time is not of greatest importance you can launch the cargo whenever you wish. It may take a while to arrive, but allows you to continue launching cargo all the time instead of only every 26 months. Since a solar sail uses no propelent there is no payload penalty to launching even at conjuction, it just takes longer to get there. Also it is a method scalable to whatever launch vehicles are most efficent. Lastly there is no reason that a solar sail could not be reused. Once returned to earth orbit they could be met by another outbound cargo container and begin the journey again. Once mass produced the sails may be cheaper than the cost to put them in orbit in the first place, so it may make sense to simply dispose of them, but ever ounce that is not spent lifting the sail may be spent lifting something else instead.
The biggest problem with using any such anti-matter catylised system within an atmosphere is still radiation. Most practical fusion reactions produce lots of neutrons which are highly penetrating and deadly, and the pions and Gamma radiation from the anti-matter reactions are likewise deadly and highly penetrating. Shielding is heavy, and the best solution is to simply seperate the engine from the rest of the craft. Both of course make an atmospheric craft difficult to impossible. And the potential for contaminating our atmosphere is still there.
You hit on my point exactly, any natural impact of this sort would have to be from a source outside our solar system, and thusly given these sizes and the distances invovled, incredibly rare. (BTW I was refering to the escape velocity very close to the sun's surface ~600km/s about as fast as you can go and still remain within the solar system.
Problems with prediction of the results are my only issue though. Extensive study of the inner geology of Venus (very hard to do), would certianly be necessary and even then I am dubious. And I agree that it should be possible to accelerate an M type asteroid to the necessary velocity to the Orion method.
As Venus terraforming methods go, I don't think this one is half bad. Even if you only increase the rotation velocity and blow off some of the CO2 atmosphere, it would be worth it. Although I agree it would still be a long term proposal as you wouldn't want to be on the surface for quite a while. Another problem might be the release of other undesirable chemicals, along with H20, especialy sulfur, which venus already has to much off.
The only conceptual problem I see with this plan is that it would be very hard to impossible to determine what exactly the consiquences of the impact will be untill after the fact. I mean collisions of this velocity haven't happened in the recent history of our system. Indeed 1500km/s is more than double the velocity needed to escape from our solar system so any natural impactor would probably be extrasolar in nature. Also by there very nature these sorts of impacts leave little evidence behind with which we might determine exactly what might have happened, if an impact of this sort had occured previously.
But perhaps in the future it will be possible to predict the consiquences via advanced computer simulation. But I still have my doubts. The consiquences of such an extream impact will probably be impossible to predict untill they actualy happen.
The key word here is assume. I'll become a beliver when someone can give me some hard verifiable experimental evidence that such things exist. Untill then I shall remain a skeptic.
Nickle is a tough (hardness 4), dense and relativly unreactive. But I'm not sure it is ideal for must uses. Primarily because it is so rare and is overkill for most uses. Even if you are mining asteriods iorn is going to be much more common, and so it makes sense to alloy it with Nickle for most uses and the alloys are supperior in most cases anyways. Nickle is also usefull as a chemicly resistant coating or wear surface coating to plate other metals with. Compared to actulaly refining the stuff this realy isn't that complicated a process (I should know, I do some work in this industry) and can be done in an electroless manner in Nickle's case. In short, nickle is just to valuable to use alone in hand tools and the like. While the simplicity of carbonly deposition is nice, I don't think it justifies using such a (realitivly) scarce resource when some other, more common metal or alloy would suffice.
However, the refining methods you talk about are what the industry curently uses to achive purified nickle, which does speak in its favor.
I don't want to be rude, but none of this helps to explain how the Enterprise (or any other FTL ship) gets around the sevear violations in causality it can cause. Hypothising about quantum theory this or quantum string that is all well in good. But eventualy you have to start talking about real things with real measurable attributes, which then have real and unavoidable consiquences that tends to make these sorts of things impossible.
I thought I covered that in another thread. You could not possibly produce enough anti-matter to eliminate all the CO2 or sulphur in Venus's atmosphere it would take the entire out put of the sun for several thousand years to acomplish such a task. Nor can you selectivly chose to eliminate just the sulphur via such method. It would take much less energy to simply eject the stuff from the planet. I like the idea of heating the planet up until CO2 starts to reach escape velocity, though I imagine this would take quite a while, and you would lose what little water vapor remains
As for all this Drexlerian nanotechnology, see my response in the other thread. The chemical relam realy doesn't work like that. And as much as I like the ideas of "grey goo" and "miricale/utility foam" I'm afriad such machines are quite beyond the relm of plausibility.
I hate to bust your bubble, but nanomachines of the kind you describe are completely impossible. You have to understand what the molecular/atomic relm is like. At anything close to room temperature (much less the hell hole that is Venus) atoms are constatly moving, colliding, and vibrating in constant random brownian motion. The idea of "claws" that could "grab" certian atoms and manuver them into position is impossible. Molecules themselves do not hold a single stable shape but in most cases constatly fluctuate betwen a variaty of stable and unstable shapes and configurations. Most models are only of their most common and stable configuartion/shape not their only one. Indeed a great many chemical reactions call upon a chemicals ability to fluctuate from it's most stable configuration to one in which a chemical reaction can occur.
BTW, please use a more readable color for your posts!
Well the hard and fast limit for anti-matter production is twice the amount of energy it contains, for every particle of anti-matter you create and equal of matter must also be created. I am also dubious about utilising anti-matter to be found in the so called "quantum foam" they don't call these things virtual particles for nothing.
If you want to look for a sci-fi energy solution I think anti-matter is a dead end. What you realy want is some method to directly and toataly convert matter into energy. Figure out how to do this, and you are set.
As for FTL travel I'm afraid it may forever be a pipe dream. No one has every detected a tachyon or any other sort of FTL particle, which is good because of all the nasty causality problems such a particle could generate.
Well it is realy hard to beat the efficency of traditional turbine. Most of the work I have seen involves using a MHD to augment a traditional turbine system. In this fashion they can get some fraction of that 10-20% efficency on top of the turbines already excelent efficency. I'm not sure of what efficencies a MHD could eventualy reach. But I do know that it has quite a long ways to go before it challanges the allmight turbine.
It also has a very, very neat trick... it would use an MHD generator. The Uranium would actually get so hot it would become a plasma, and a plasma moving through a coil can be coaxed into producing electricity directly with no thermal-turbine-electricity conversion. The high operating temperature also radically reduces the radiator size needed... You thusly produce much more electricity per pound of reactor then a conventional solid-core one.
The only problem I see is that the MHD generators I have read about have relativly poor efficency (10-20%) when compared to conventional turrbines. Although I suppose their reduced mass and size would help to compinsate for this in space applications. I'm also worried by the potential for criticality in a location other than the reactor.
Oh not the "we have to flgiht test the LSS box!" argument again... Thats really getting kinda lame. Why exactly does a machine that handles gasses going to behave lots different with or without gravity?
If you absolutely had to flight-test it, it would probobly be easier to build a satelite and cram it in there with a CO2 & H2O tank to mimic human respiration products.
Because you have to test things in the manner (or as close to the manner) you plan to use them, or it's realy rather pointless. In the case of the Hab LSS system it has to function for two years without the possibility of major repair, in two very hostile enviroments and undergoing some of the most violent permutations (launch and re-entery) imaginable. Testing the Hab in conditions as similar to these as possible is vital for a succesfull mission.
And the Hab LSS is more than just a simple machine that handles gasses. Life support is interdepenat on virtualy every aspect of the hab, especialy the enviromental seal and the power systems. Since one minor failure in one system can easily cause a major failure in another it is also critical to test all these systems together.
This is why I am in favor of doing a Moon "shakedown" using as much as the Mars mission technology as possible. I guress this is kind of off-topica as the shakedown doesn't have to be launched immediatly, but the soon the better IMO.
I recently finished reading Footfall a decent work of "Hard" science fiction by Larry Niven. **Minor Spoiler** which involves the use of a Orion type space battle ship being launched in a counter offensive against the aliens. Not terribly unrealistic IMO, though I did wonder where they got the thousands of nukes to power the silly thing. Its a good (if some what off the wall) example of a potential use of Orion. If your intrested in the Orion concept you should read it just for that, I can almost guarantee that you will like it.
Now I agree with some of what the article says. Modern advances do make Orion look better than when it was orginaly concived. Especialy with regard to new and smaller nuclear weapons. But many of our nuclear advances won't help at all. For example, MT and tenths of MT devices are MUCH smaller and cheaper then they used to be, but these sorts of weapons are really to big for nearly all Orions.
But in the end I agree with what GCNR has to say. The development and mass production of new nuclear devices, even realtivly small ones, will be objected to seriously by both Americans and the world at large and may be violations of critical arms control treaties such as SALT, PTBT, and Outer Space Treaty.
Realise that for any Orion system you are talking about a signifigant increase in the current US stockpile of about 10,000 weapons. At 900 or so weapons a pop other countries can not help but be nervous about a 10%+ increase in the US stockpile, even if they are of "relativly" small yeild (although there is nothing small about the yeild of a 2kt device). We would certianly be nervous if China or Russia start such an increase, and rightly so. And this is just for one launch.
But the concurns don't just stop there they get worse. Not only are you talking about constructing nearly 1,000 new weapons, you are also placing them in orbit where the could be delivered at any time without warning on opposing nations, just like the old soviet FOBs. Such a first strike weapon is incredibly scarry, so much so that the US was considering striking first should the USSR chose to deploy it.
Now I am not overly concurned with the threat of multiple nuclear detonations, even hundreads of them within out atmosphere. If detonated in a sufficently remote area, it probably could be safe. However, the general public is NEVER going to allow the it. That I can also pretty much guarantee. I myself am slightly worried about the dangers of high-altitude EM pulses on our electronics.
And the cost is likely to be enormous. Nuclear weapons aren't cheap. And developing and constructing a entirely new line of weapons system is even more expensive. I haven't seen any cost analysis, but I would be supprised if it came up much cheaper then current systems. And if doesn't cost less, then what realy is the point. It is going to take some time. We just aren't geared up for that kind of production anymore.
I like project Orion and Nuclear weapons in general. Nukes, along with landing on the moon are the two greatest scientific/engineerign achivments of man to date. But even so we must be realistic in our application. Divert an incoming asteriod, sure. Use to rise from earth? No way.
I secound the comment that there is lots of science to be done on the moon. It is by no means "been there done that." I don't think anyone on this board would be happy if we landed a couple of times on Mars, then packed up and said, "well, we've learned all there is to know." There is always more to know, and the moon is far from reaching the point of dimminishing returns.
On a more practical aspect the moon can teach us ways of doing things that will be vital for our later trip to Mars. And do so in a much safer manner. An abort from the moon is only a couple of days. On Mars it is years, and a critical accident will spell doom.
The moon gives us a safe and stringent testing ground for virtual all critical aspects of a Martin mission. Reactor, rover, hab, spacesuit, and perhaps most criticaly, long term life-support. Neither the US nor Russia has every fielded a the sort of long term regenerative life suport system that will be critical for the opperation of this mission. If we had to use the systems we currently have developed (such as for the ISS) our astronaut would be very dead right now. And I said before (perhaps in this very thread), if you don't test things in the manner you plan to use them, what is the point?
As fora permeant base building on the moon. I think there is some pay off to be made here as well. Learning to build things via on-planet resources is another new challange for us. While some the methods used on the moon will be diffrent then those used on mars, many lessons may still be learned. And while safet is not as big a factor, cost certianly may be. Building a base on the moon well be much cheaper, so it's a cheaper place to learn. Also, developing a cheap reusable method of access to the moon will likely assist in developing the much more robust method that it necessary for mars.
In reality the US and the world at large can easily afford to do both. Especialy if some cuts are made in some of the absurd defence spending that is made both here and abroad. I say go to mars, but that doesn't mean we shouldn't go to the moon to.
How about emergency robotic high-gee ships, launched from Mars, or LMO (sort of like a Space "Coastguard" Rescue Service).
Catching up to a "taxi" headed out to deep space is going to be very difficult. The rescue vessle would have to have not only greater delta-V than the orginal taxi, but enough to stop and return to base. There is generaly no free return orbit for these trajectories, or if they do exist they are of very long duration. Needless to say that this would require not only a signifigant amount of thrust, but also alot of propellent. And it doesn't avoid the problem of redevous either. Better IMO to either avoid these high speed redevous all together, or have the abort option built into the taxi craft itself, which is going to increase it mass signifigantly.
Apparently both MER rovers were dropped into the Martian atmosphere within a hundred meters or so of target. If that is the case, a staffed vehicle with GPS positioning and a Mars orbit or Mars-ground mission control should be highly reliable and exact, unless some sort of Apollo-13 style accident happens within an hour or so of atmospheric encounter.
I would only point out that the rovers aerocaptured directly onto the planet rather than aerobreaking into an orbit and then landing.
I have to admit, the orbiting Cyclotron idea caught me off guard. Full points for creativity. But even a casual examination proves it can't possibly work. Most obviously there is no way to selectivly target the sulfur in the atmosphere. Anti-matter is going to react with the first partical of matter it hits, regardless of it's nature.
I guess you could still use it to remove excess carbon dioxide but the amount of mass you want to annilate is stupendously huge, and your energy requirments to annilate are thusly even more enormous. Here's a quick back of the envelope calcualtion to prove it.
I'm not sure exactly how much Venus Atmosphere masses, but since it is about 90 times as thick as Earth's (and I know the mass of Earth's atmosphere) I'll use that as a concervative estimate. 5 x 10^18 kg. That's 5 million billion metric tons. To remove all of this would require an equal mass of anti-matter. Since we don't have any anti-matter mines handy that anti-matter must be generated artificialy via cyclotron or some other (currently unknown) method. Since we are creating it we must pay the steap energy cost involved with matter (anti or otherwise), ~90PJ/kg. Thus we would have to create 449 x 10^18 PJ (that's petajoules BTW 10^15J) worth of anti-matter. Now ~450x10^18 PJ is alot of energy, 4.50x10^35J, such a huge number I don't know of any easy way to express it. But the problem is actualy much worse.
To produce any amount of anti-matter you must also produce an equal amount of matter giving us a theoretical limit of twice that amount, 9x10^35J. But we can't even come close to that. CERN facilites currently spend millions of times the theoretical limit. I'll be generous and assume advanced techniques get that amount down to only 1000 times the theoretical limit, some 9x10^38J.
The sun itself only puts out 3.9x10^26W. So, assuming you could capture ALL of that energy it would take you only 73 thousand years to remove it all. And since you can only capture a infinitesimally small fraction of the sun's energy, the idea is completely unworkable. Indeed it would take MUCH less energy to simply fling the stuff out into space then to try and annilate it.
One thing that worries me about Aldrin's Cyclers is the abort mode for the Taxi's if they miss their redevous. Most designs I have seen call for dispisable high energy chemical stages to reach the necessary delta-V to catchup up to the cycler. But what if for some reason they miss, it's not exactly an easy operation by any means. The taxi may lack the means to return their crew to Earth or even Earth orbit.
Japan could certianly afford such a program if they really wanted it. There 2005 budget was ~780 billion dollars, and this program only adds up to 2.8 billion a year, .35% of the total budget. Small potatos really.
As for there economic problems, while they are trouble some, it is easy to get caught up in them and loose sight of the bigger picture. Japan has a large and extreamly well educated population (126 million). While lacking in some critical resources it is massively industrialised, perhaps even more so than the US. While they do not have the experience in Aerospace technology that the US has, the are competivtive with us in virtualy every other important technical catagory. The country has everything it needs to launch a succesfull space program, whenever it wants.
I have to agree that the idea of dumping coal on mars as a method of terraforming is totaly bogus. No doubt extream amounts of enginnering is required for teraformation. Asteriod/comet impacts, titanic orbital mirrors, huge nuclear power plants and chemical manufacturing activity. But dumping coal? This is pretty silly.
As for anti-gravity. I'm not going to be foolish and say it isn't possible. But we tend to stick with science that is well established and accepted here.
Oh we are talking years if not over a decade in most cases (sometimes several decades) to change these orbits. The solar system is a very big place and it can take a very long time for an object to get from one location to another. In many (if not most cases) you wouldn't be making a standard hoffman transfer orbit anyways, but swinging by one of the gas giants for a gravitation assist, to let you do it with less delta-V. If you didn't have a problem with waiting a VERY long time (centuries and up) you could probably find a target that would require mere m/s change in Delta V. And if you were willing to extend to milleniums even less than that.
The actualy application of force happens in a short period of time however (if you use the nuclear method). Not to many blasts are required to give the comet/asteriod the necessary boost, but after you do so, it still takes a long time for the object to get where you want it to go.
While I do agree with the assement that Solar Sails are so slow as to be completely unusable as either a primary or a back-up method of transportation for manned vessles, I do not think that the same necessarily applies to unmanned vessles. Which lack the strict time constraints of manned vessles.
A solar sail has the extream advantage of not carrying it's fuel source, this makes extreamly long durration flights possible. For example a mission to explore the asteriod belt would require a vehicle which could manuver for decades. No conventional engine can provide this duration of performance, only some sort of ion engine would come close, and even it would eventualy run out of reaction mass.
Another possible example is as a reusable ferry for cargo to Mars or some other destination. Now while it could take 5 years or more for the supplies to arrive, the vessle would be unbeatable in it's simplicty and reusibility. A NTR or Chemical ferry would require large amounts of refuling at either ends and would be much larger and much more complex. A NEP (ion drive) vehicle would also be much larger and more complex, have little to no advantage in speed and would still eventualy require refuling of it's reaction mass. Both sorts of vehicles would probably not be able to slow to Mars or Earth orbital velocity requiring a there cargo to make a tricky high speed orbital rendevous with little option for abort if something when wrong.
I guess in the end what any engine decision comes down to is the cost to deliver a cargo to some destination. While alot of research still needs to be performed on solar sails, they potentialy could perform quite well in this catagory. A solar sail has the potential to be a very cheap and reliable method of transport. No exotic or hazerdous materials are required (xenon, plutonium, uranium) neither is any complex machinery (reactors, turbopumps). The only disadvantage is there speed.
And speed is realy only a question of sail size/mass versus the size of your cargo. If you can get the sail light enough, make it large enough, and keep the cargo resonable you could realy zip. Indeed, I once read a study about a interstelar probe which launched near the sun which developed several G's of exceleration for an extended period of time.
There are also solar dynamic vehicles which operate in a similar manner to NTR, using large mirrors to reflect sunlight to heat the propellent. They can supposedly achive similar performance, but are slightly more restricted in there use (you can't use them in a planets shadow obviously).
I'm not sure about the short term feasiblity of placing an object in orbit around a planet. Changing it's orbit to simply impact a planet is often easy, depending upon the objects orbit and location often less than 2km/s is necessary, sometimes much less. However, to put it into orbit around Mars you need to reduce it's over all orbital velocity (generaly in the neighboorhood of 15-45km/s) to that of Mars orbit, some 5km/s so a much bigger change is necessary.
--edit--
This is on top of the energy necessary to change the orbit of the object to intersect that of mars as well.
Increasing a comets orbital velocity may, or may not be a better idea (I'm not going to argue the point), but it is certianly much harder to acomplish. To increase it's orbital velocity you need to aproach/land on the trailing edge of the comet. Which requires matching the objects orbital velocity, which requires ALOT more delta V. Or you could possibly time an interception with the trailing edge of the object, but these geometries would be VERY difficult to achive. Perhaps if the object was rotating you could impact it in the front and then wait till the rotation had it pointing the correct direction, but again timing the explosion would be difficult.
Sounds good. Incidently "slowing a comet down" is the ideal orbit changing situation. Since the nuke then only has to hit the leading edge of the comet, intercept gemoetries are MUCH easier and less Delta-V is required. In fact, with good terminal guidence I don't see why you could put the bomb inside a penetrator housing and blow it up well inside the comet giving an even push.