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Wow, what a masterfull analysis RobS, I'm impressed. I would also point out that when transportation reaches around the $2.5 million per ton mark transportation costs have probably droped to the point to which public and private corporations can afford to make serious investments in Mars, and if it ever reaches the $.5 million per ton private individuals financing their own way to Mars becomes a possibility, especialy with the increased prosperity we can expect to have by this time. This may mean that we could expect the growth from 100-1,000-10,000 to happen at a much more rapid rate than the inital establishment. Although the physics of space travel may put an upper limit on the number of people/cargo that can be transfered per year, regardless of the finances.
And I partialy agree with your assesment on GCNR and their use. I am unsure as to how reusable such a engine would be (they certianly are going to require some uranium refuling), however there is no reason that if the engine is signfigantly reusable that it couldn't use H2 produced on the Moon/Mars/Phobos. The bigger issue to me the issue of travel time/vrs payload cost. Taking a faster/more energy intensive path is going to require signifigantly more fuel. In addition faster transits mean a faster approach on Mars which will make aerobraking more difficult or impossible, which would mean you would need to take fuel to slow down again as well. All this extra fuel may end up massing considerably more than the extra food/LSS/consumables you would have to take. Higher ISP engines are of course almost always worth it, but faster trip times may not be.
For cargo I still think the choice is clear, solar sails all the way. In the beginning (pase 2 in your post) throw away solar sails could have a big advantage. Once orbital tugs are avaliable on Earth/Mars the could also be reusable (giving us a handy way to bring cargo back from Mars), and if the could be manufacture on the moon the advantage would be massive. This could dramaticly drop cargo cost much earlier in a colony's development.
As for getting down to $100,000 per tonne a long enough space elevator MIGHT do this. If the cable is long enough you can just wait for the right time and just let the thing hurl the parsel at Mars. But at this point further reductions in cost are likely less important as the cargo itself is probably worth considerably more than $100,000 per ton. Since it is probably high-tech manufactured goods/highly refined minerals as by this point the cheaper commodities are probably manufactured on Earth.
Stormrage, Indeed you could (and probably should) surround the reactor with lead or other heavy/dense metals (esp. Tungstun) in an effort to try and contain/control the Gamma radiation. Indeed my favorite anti-matter engine/reactor design (the lightbulb design) relies on this tactic. However, realisticly even with thick dense lead shielding you are not going to be able to capture all of the Gamma radiation, as some of it is Extreamly high energy (practicly cosmic ray's often over or around 1000 keV). Containment of photons of this level of energy is difficult to impossible. Of course a more conventional magnetic containment system is unable to capture the Gamma radiation at all, but may do slightly better at capturing some of the high energy pions.
In terms of safety seperating the crew from the reactor is probably the best bet. Radiation decreases via the inverse square law so distance is generaly more effective than shielding. But even for interstellar drives the rate at which anti-matter would be used is rather small and the radiation released is little more troublesome than that of a more conventional nuclear fission/fusion reactor of the same strength, so I don't susspect that will be a stoping issue.
The amount of energy per gram of anti-matter is actualy both a simple and complex question.
Simply Matter-Anti-matter reactions produce the energy equivelence of the matter anihlated. Via E=MC^2 that's 1.8e17 J/kg that's about 2 orders of magnitude (100 times) more energy then released by fusion (2.6e15 J/kg) and about 10 orders of magnitude more than gasoline and most other chemical fuels (4.2e7 J/kg). Making anti-matter by far the highest energy density fuel we have ever produced and since it relises total conversion of matter, quite possibly as high a energy density that can practicaly exists.
However M/AM reactions produce alot of kinds of energy that is simply very hard to contain and control, and thus very hard to convert into usefull energy. About 1/3 of the reactions energy is released in the forms of Pions traveling at signifigant fractions of the speed of light. Pions interact very weakly with normal matter and are therfore very hard to contain, especialy at the speeds they are traveling after an M/AM reaction. Another 1/3 of the reaction energy is high energy gamma radiation which is also difficult to control, though not as bad as the Pions. The last 1/3 of the energy is other muons which are more easily controled. So at best most anti-matter engines are only going to be able to utilise perhapce around 50% of the total energy created, still pretty good.
I can say with supream confidence that there will be no life boats or escape pods. Space is a harsh mistress, and if something goes wrong with the main vessle, then the entire crew will likely go down with it. There simply isn't room in realistic space vessle for entirely redudant life support system of the durations necessary for serious space travel, much less redudant propulsion systems. That's just the way it is.
We've talked about this ALOT before (do a quick search for Orion to see) but to me three big questions come up.
#1. Economy - Highly enriched Uranium/Plutonium is expensive, very expensive. Thus the 1000's of nuke Orion requires are not going to come cheap no matter how you manufacture them. Not to mention the expense to design and test this new class of nuclear weapon. Despite the fact that they might be of realitivly small yeild they will have to be the most precise nuclear weapons devices in history, as misfires or underfires cannot be allowed. In the end it may turn out that the Orion is not as economical as other possible lift methods.
#2. Politics - Orion, by it's very nature, is a serious violation of many political treaties. Not to mention that other nations would rightly be a little worried if some nation started mass producing thousands of new nuclear warheads and then placing them in orbit. Not to mention the enviromental actives concurns about enviromental damage.
#3. Engineering - Orion is an outragous concept, and will certianly present incredible engineering challanges, landing not the least of them. It may turn out that it is not even technicaly possible/practical.
For these 3 reasons I have to say that while Orion is a neat Idea, it's not viable in our current political enviroment.
I'm with GCN on this one, I think what he says about the long term goal being the development of reusable medium lift systems for all three Major worlds is dead on. With that under our belt the entire solar system will be much easier to grasp. And I think that is one of the major points to the president's space program. It sets us back on that track and away from diddling around in orbit.
And I'm also inagrement with those who stated that a lunar "shakedown" is a VITAL precursor to any Mars Mission. Those guys are going to be out there a long time with no possibility of rescue and little for resupply. Their stuff, especialy their LSS just have to work, no questions asked. The best way to ensure this is to throughly test it in as hostile an enviroment as you can safely find, for which the moon qualifies well. It's absolutly imparative that you test things in the manner you intend to use them, and the Martian Mission madien flight is NOT the time to find out what is going to go wrong.
As to the duration of any such test mission, I am realitivly indifrent. Idealy the LSS should be tested to ensure that the perform to the maximum expected duration before use. A permenant manned base makes sense to me however since if we decide to go their, it would only be a small additional cost.
Lastly, I emphaticly regect the notion that there is no more science to be done on the moon. There is a LOT more science to be done on the moon, just the science to be done is not easily acomplished in a short week or two. We wouldn't still be sending orbiters and probes there if this was not the case. And what it has to teach us in terms of additional mission experience is priceless.
In short we should go to Mars, be we shouldn't be in such a hurry to go their that we shoot ourselves in the foot in the process. Better to build up to so by the time we do it, we do it right, and we do it for good.
As a side note, this delay, especialy if it turns out to be as long as the last one, pretty much rules out any possibility of another Hubble repair mission and certianly cause much difficulty in deciding what to do with the ISS. This all makes me think this may be some subtle ploy by Griffen to get the shuttle retired sooner rather than later, or maybe this is just wishfull thinking.
I don't have the right back ground to make an educated guess at the rate the ultracold enviroment would sap heat from a habitat, other than to compare it to the rate other devices lose their heat energy. A conventional Dewar flask loses it's heat MUCH MUCH more slowly than the 500W or so I was estimating for a colony. The Dewar's I have delt with generaly return only a fraction of a liter to room temperature a day, maybe 1/100 of their total volume at worst. Now obviously we can't reach that level of insulation in a large realtivly light-weight colony, but my estimate is still conserative by >4 orders of magnitude from that optimal situation. Quite a comfortable margine.
I don't belive their could possibly be a problem with the colony losing heat faster than it could generate it. If you have sufficent energy there is realy little practical limit as to the rate you pump it into the system. Heaters can be very small for the amount of energy they pump out. A 500W heater would realy be chump change. Short of some drastic disaster such as a breach a large breach in base's wall that lets the surrounding atmosphere pour in (which would definetly be a bad thing), it's hard to imagine such a situation.
One last note, obviously the rate of heat loss is most variable with respect to the size of the base we are talking about. Large bases would obviously lose more heat (having more to lose) but lose it more efficently having less surface area for their volume. If there is going to be a problem with heat it is going to be with space suits, like you said. Which have the most surface area and the least possiblity for insulation.
I still think the everone is overstating the hardship the cold would cause. Warming the base Nitrogen atomposhere from a chilly 93K to a comfortable 300K (27*C) only requires ~6kJ a mole or about ~250J/L. In comparison electrolisis of a comparable amount of water requires ~200kJ/L (~3.6MJ/mol). Clearly heating the interior air is a minor energy requirment. And waste heat from a reactor could be used for this purpouse. Even assuming heat is lost at a realitivly high rate, say 2L worth of air returns to surface temp a secound, we still are only looking at energy use of considerably less than a kW, which realy isn't that signifigant.
I won't argue with most of the other points though. Titan is certianly difficult to get to and the lack of sunlight and low G aren't that great. BUT it's great abundance of organic resources still make it an atractive target.
I imagine things would be tough on Titan, but not entirely impossible I imagine. While it's distance from the sun probably pretty much entirely rules out using solar energy for anything, that may not be as bad a problem as it sounds. Besides some heat energy and light for plants an intial exploration mission would not utilise much solar energy in any event.
The super-cold nature of the planet does pose some worries, but is not necessarily insurmountable. For one, it means that any power-plant that relise on thermo-electric conversion (right now virtualy all of them) will be able to relise much greater efficency than anything we could do here on Earth or in Space. And while the outpust would probably require lots of insulation and active heating, I suspect that this energy burden would be pretty mild in comparison to some of the high energy activities we talk about on these forms, such as the many various means of fuel production, which practicly all require energy intensive hydrolisis. Modern insulation is quite effective and I suspect will perform well even in the face of Titan's tempetures, I mean we have no problem keeping the shuttle fuel sufficently chilled in Florida, it the exact same problem only in reverse. Furthermore even with the higher efficencies of the reactors on Titan, I suspect there will be pleanty of heat energy remaining to chill the colony.
Having to power lights to grow plants is troubling, but probably unavoidable anywhere in the solar system beyond the orbit of Mars. So Titan is not alone in this challange. However Titan has most (if not all) of the key elments for life readily on hand unlike most other destinations. Oxygen, Carbon, Hydrogen, Nitrogen are all present in large quantities and generaly in readily usable forms (Ammonia, Water, Methane, ect). Titan has alot to offer the rest of the solar system and itself in terms of abundent organic mineral resources.
To mean the biggest challange is still getting there. A long trip no matter how you do it. And the thick atmosphere makes take-off more of a challange as well, but does make aerocapture possible.
I wish the China good luck, but they have a long hard road infront of them. It took NASA a good 10 years to go from man in space to man on the moon, and that was with the US devoting a much more signifigant portion of it's budget (a not insifigiant portion of the US's GDP realy) then either the US or China is now.
Now while the Chinese have the ground already broken in for them the engineering obsticles bettwen them and the moon are no diffrent then they were for the US. An incredibly difficult challange. Best case scenarior they are another 10 years out at which point hopefully the US will be nearing fruition with it's return to the moon plan. More realisticly it will probably take both the US and China a little longer than that. We could end up seeing a secound space race though. I'm all for it, a little compatition is a good thing.
One thing that certianly will be needed is some kind of stationary ballon to sample the weather at high altitudes and potentialy act as a long range attenna.
Come to think of it, monorails suspended between cable-guyed skeletal towers like those we suspend powerlines from here on Earth, should be feasible on Mars.
This is not a terrible idea, although I'm not sure that constructs as flimsy as telephone polls would be able to support a heavily laden train. But certianly Mar's low gravity will make some incredibly large suspession type structures possible.
However there is still the issue of the incredible distance you have to cross. In terms of land area Mars as big as Earth and so we could be talking about projects similar in scope to the US's transcontinetal railroad or the Soviet transiberan railroad. We could be talking about thousand of kilometers of track here.
I sometimes wonder about anti-matter as a power source. Of course producing it will always be horendusly expensive, even with increased efficency, and we currently have no easy way to store quanties of it. So using it for power would seem impossible.
However, we can excect at least an order of magnitude increase in efficeincy of production (still terribly expensive) and long term portable storage methods do not appear to be to tricky to create. I sometimes wonder if anti-matter might become a viable form of power for space travel before fusion does. Certianly there is no problem in converting it back into energy. It might happen that we solve the problems of anti-matter transport before we solve those of fusion.
I think building a conventional train with tracks and what not on mars would prove to be extrodinarily difficult. While the idea certianly has its merits, its something for the later stages of colonisation when the population of mars is in the hundreads of thousands of people range.
I think an imporant point that people are forgetting is that Mars is a huge planet (as much land area as Earth) with surface features that match and/or exceed anything we have here as well. Indeed land travel across some of Mar's surface features (like the Valles Marineris) may not even be possible without some gigantic feets of engineering. Building even a realitivly small streach of rail (in comparison to the size of the planet) could be prove to be a huge undertaking. You must first survey the rout, as heavily laden trains cannot directly climb tall hills or take sharp turns. Then you must grade the course, as trains moving at high speeds don't deal well with bumps and dimps. Of course any terrain features that get in your way must be delt with by being filled in, bridged, or tunnled as appropriet. I'm not saying that such a project is impossible, but the effort required will be very great, and the distances you might want to traverse could easily dwarf anything every attempted here on Earth.
I think RobS plan for a land train or convoy of vehicles is much more sensible for the beggining. It is how bulk transport is handled in places like northern Canada and Antartica where similar chalanges are faced. A track for a land train is much simpler to rout and grade since they are not bothered by bumps or dimps, can make sharp turns, and can generaly climb much steaper hills than trains. It is allows a natural evolution of transport. First sporadic transport by all terain exploration rovers, then mild roadmaking and cargo transport by such vehicles, then convoys, then finaly true road trains.
The question as to nuclear of chemical propulsion is a tricky one. Both have their advantages and disadvantages. I tend twords nuclear propulsion though. A nuclear propelled land train could circle the planet indefinetly for years on end without refulling. Also, without the need to carry fuel a nuclear train could transport more cargo, this become especialy evident on very long trips.
I often think the problem of AI is a lot like the problem's we are having with Fusion, only worse. If fusion has been 20 years off for 50 years now, it seems like a good AI has been 100 years off for the same length of time. I am pesemistic, intellegent autonomus programs have proven to be very difficult to make. Not necessarily because we lack the necessary hardware to create them (although this is certianly part of them problem), but because the programs are so complex. More powerful hardware does not seem to make these programs any easier to design.
I think it's telling that although our computing hardware has increased by litteraly an astronomical degree since the beginning of the space age, the computer programs that controle say that Deep Impact really aren't that much more complex then the ones that controled Viking or Voyager.
The problem is that there is a limit to how complex dependable programs can be, and this limit hasn't increased much. Most of the so called advancments in computer programming (OOP or whatever) have had little effect on the difficult in developing a complex program and no effect on how reliable complex programs are. I fear that for the next 20-50 years at least we are going to be stuck with what we have now. Robots that opperate mostly via Remote Presence with some minor autonomy when Remote Presence is not possible. The program necessary for a machine to make the correct decision in the wild and unpredictible frontier of space exploration is simply to great.
I really don't have much to add to the discussion here. No doubt a conventional war bettwen the US and China would be much as you say. The US has such an overwelming advantage in both sea an air-power (especialy sea) that it is hard to imagine China gaining any ground in an invasion of Taiwan or any other overseas location that we might care about. Thats not to say that such a victory would be bloodless, war never is, but the US would assuredly be the victor.
The problem is that China is not some two-bit third world nation like Iraq or Bosnia that we can bully around, because in the end they have little to no means of striking back at us. This is not the case with China, who is a nuclear power. Just as was the case with the US and Russia during the cold war, it seems likely that any conventional war would soon escelate lead to the use of nuclear weapons.
Now the US's nuclear arsenal outweighs China's by at least an order of magnitude, and so if we should choose to retaliate China would certianly be the worse for it. But that would be small consolations for those living in major US cities such as New York, LA, Washington... exct. which would no doubt be targeted and destroyed by nuclear assault.
So lets all just hope that cooler heads prevail in both the US and China and such a thing never comes to pass.
I belive I have been a little bit misinterpreted, I don't mean to say that we should be working towards all the things you are talking about but a little realisim in terms of how quickly these things can happen. Dook is right to say that 1000+ person colonys anywhere in the next 25-50 years or so is both foolish and probably technicaly impossible. Mars, and to a lesser extent other orbital bodies are a long way away and very difficult to get to. Futhermore the requirments for self-sufficency are incredibly massive. This makes our project incredibly difficult.
But time heals all hurts, and solves this problem. Over the long hall, colonisation is possible. Thats all I realy ment to say. Colonisation is a project for the next century-millenium, not the next 20 years.
Well I think that key element missing in this discussion is the aspect of time. I agree 100% with Dook that massive moon/space/mars colonisation programs do not make any sense in the short run, say the next hundread years or so.
But if we take a longer ranged look at things, they begin to make a lot more sense, and become alot more plausible. Columbus discovered America in 1492, but it took over a century for mature self-sufficent colonys to become plentiful, and several more centurys for America to reach the high level of civilisation that it currently enjoy's.
So I agree that Mars, the moon, Asteriods whatever are not going to be the savior of our civilisation. In the Mars Trilogy KSR points this out quite clearly. There are simply way to many people on Earth to ever move a signifigant percentage off of it. We are going to have to solve our problems (population and otherwise) here.
But that doesn't mean that we can't expand our civilisation out beyond earth for other reasons. Given enough time we (hopefuly) will develope the technology and the wealth required to make this possible.
There's a neat example of what you are talking about in the Anime Bubble Gum Crisis 2060 (or something like that).
I'm still skepticle as to if it would work, but it's cool to sometimes see your ideas in action.
I think I said this before, but it bears repeating. I think entirely to much time and effort is spent on attempting to recover the upper stages of any launch vehicle. It is far more important recover the lower and any intermediate stages. They are both larger, and thus generaly very expensive and far easier to recover than the upper stages. The upper stages are the smallest and have the toughest job to do, so it makes the most sence to make them disposable of all the stages.
If our goal is to lower the cost to orbit, it might be seriously worth looking at various methods of re-using the lower stages of current launch systems, such as the fly-back boosters for the shuttle. It may be worth a high development price and lower performance if the lower stages can easily re-used. I'm worried that most of the SDV and EELV continue to focus any of there re-use upon the upper stages of the vehicle, when it should be focused on the lower stages.
I mean, yes ideal we would like to get the whole vehicle back intact, but if that is not possible, let's keep the lower stages and use disposable uppers. A great deal of our future uplift demand isn't going to be comming back anyways, indeed people or maybe a hundread pounds of samples/science equipment is all that we currently are looking at bringing back anyways, everything else is staying in space. So why all the focus on re-using the most stressed and least used componet of any launch vehicel?
Yeah, I was wondering the exact same thing. Sounds like something I would be intrested in.
I wonder if it will ever be practical to utilise high-thrust high-impulse engines such as fusion, VASMIR, GCRN ect... to radicaly reduce transit times or to increase the launch window. While it is certianly desirable to decrease the amount of time people spend in zero G, the payload penalty you have to pay for this is high. In some cases it may outweigh the reduced amount of consumables/life support system equipment you would have to bring for a regular hohmann transfer. As long as cost of transporting equipment/propelant to orbit remains a signifigant part of transport cost these methods may not make any sense even for human transport.
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Now I am not an expert on orbital mechanics, but men much smarter than I have said that a solar sail can be used for trips both into and out of the solar system. Here is a paper by Eric Drexler, while I think he is an idiot when it comes to most of his talks about nanotechnology but he is dead on in this paper on solar sails. http://www.aeiveos.com/~bradbury/Author … .html]Link is Here.
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As to the logistics time table, I think solar sails will actualy have an advantage here. While it may take there cargo longer to arrive, I think that the logistic bottle neck will likely be getting the cargo into earth orbit in the first place. Here solar sails have are advantageous as they can be launched all year long and can be scaled to meet any cargo size.
While I agree that there will be little if any transport of raw materials. The amount of equipment necessary to build and expand a mars base is so large that this equipment will practicaly be bulk cargo transport for a long time to come. For the forseeable future there will definetly be cargo to fill all the Mars transport capacity we have and then some.
I disagree with the concept that all cargo is going to be time critical. In a sense none of it is, since at best it is going to take several months to get there untill some truely high technology options come online. So if there is some critical medicine or part that you need within a week-month, you are out of luck in anycase. So the stuff is going to take a while to get there no matter what.
And it's not like a solar sail takes THAT much longer to arrive at its destination. We are talking a year and a half to maybe 3 years. While it wouldn't make sense to keep people up there for so long, but I don't think any cargo is going to fail or any systems are any more likely to go bad due to radiation or whatever. And while there might be some cargo that might demand a more immediat travel time, for most of the infastructure enhancments, waiting a bit to get it isn't going to kill anyone.
And even with advanced options like VASMIR or GCNR or even fusion, you still pay an incredibly payload pentaly if you want to go faster or launch at any time. With a solar sail you pay no payload penatly at all, just a little time.
As for issues of cost, and acessability I think a solar sail comes out way ahead here of the alternatives GCNR talks about. A few preliminary orbital tests of Solar Sails have already been done (by the Japanese), which puts them way ahead of both VASMIR and GCNR which are little more than theoretical speculation. Furthermore the problems facing any sort of Gas Core Nuclear Reactor (which are necessary to both) are far more difficult than those facing a solar sail.
And finaly seperate transit systems for cargo (which can take a longer amount of time to arrive) and passangers will probably become necessary. Since I belive the amount of cargo will eventualy outnumber traditional cargo to such a degree that it make economic sence to invest in an alternative (and cheaper) deliver method if avaliable. In this sense solar sail has a minor advantage in that is in a sense independant of it's launch system. It does not have to be so massive as to assemply in orbit and could be scaled to meet whatever was avaliable. A GCNR or VASMIR virtualy requires either HLLV and/or on orbit assembly.
These Emotional arguments for saving Hubble would not
have happened had NASA Been Keen enough to see it coming.
I could see it coming, Since I was disappointed with descision
to not service it and bring it down. Once you look at what is
replacing Hubble you realize it's a Museum Piece by now.
How much better would NASA's desicsion have been received if they said they were going to send up a Module
to Kick it up to PERMANMENT ORBIT as a Space Monument.
I think a 2,000 mile High Orbit would keep Hubble around for what 100 years?
Who knows maybe then It will considered an archaelogical Reclic of late 20th century high tech.
I always favored bringing the Hubble down and putting it up in the Smithothian as a museum peice. It's value as a telescope may be limited, but as a peice of history it is priceless. This was (IIRC) the orginal servicing plan for it back in the 1970's when they were both designed. Unfortunantly either the Hubble got to big or the shuttle to small, so that bringing it down intact is now impossible. Here is some irony for you. The only Shuttle that would have had a cargo bay big enough to retrieve the Hubble was the recently destroyed Columbia. The others would require extensive remodification of there cargo bay.
Boosting it into a higher graveyard orbit isn't a bad idea IMO. It preserves the Hubble for a chance at historic restoration some day in the far future. And space isn't realy a terrible place to store a satilite. Although more propelent would probably be called for than in the deorbiting mission.
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It realy pains me to here Zubrin talk this way about Hubble. He presents quite the opposite point of view in his book Entering Space. There is a reason why the Hubble is the only satilite ever to be serviced. Thats because frankly it isn't worth it. New and better satilites can usualy be launched for as much or less then the servicing missions. The shuttle as a "service platform" was a joke from the get go. Maybe a true RLV would change this picture, but right now it is a joke.