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Well stochiometricly, yes I am making that assumtion of complete combustion, but the inefficencies due to incomplete combustion are already accounted for when the inefficencie of the engine is factored in. I know this is kind of a cop-out, but there is no simple way to calculate what amount of methanol is combusted without knowing the specifics of the actual engine, and even then it would be a factor you would half to test for to get a realy good answer.
However, a methanol (or methane) powered closed cycle engine, such as a would be on a martian rover would probably perform better than a more conventional disel or gasoline powered engine in terms of incomplete combustion. This is due to several factors, first methanol and methane are much smaller molecules than those in traditional fuels, meaning there are fewer bonds to break per unit of fuel.
Secoundly, methanol contains within it some of the oxygen for combustion already within it, which leads to less formation of CO, and less incomplete combustion. This is why methanol and ehtanol are somtimes added to conventional fuels as "cleaning agents."
Thirdly, by the very nature of a closed cycle engine, any products that are not fully combusted the first time around cycle through the engine and are combusted again.
I did not mean to imply that air was injected into the cylinder at a 2:3 ratio, only that that was approximatly the ratio at which it was consumed. However most spark ignited engines approach equilivency ratios of 1, or stochiometric ratios, as I indicated earlier. Indeed, the only statistics I could find for the performance of a closed cycle engine was for a diesel engine, which had a equivilence ratio (in this case of consumption to actual consompution) I calculated to be 1.2, which is typical for a normal chemical ignited engine. A methanol engine should perform better than this, but even so 1.2 is well within the amount I compinsated for with inefficency.
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Another factor in the martian enviroment which favors the combustion engines, is the abscence of nitrogen in the atmosphere. Without nitrogen, no energy is wasted forming various nitrous oxide compounds (NO, NO2, ect...)
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Another note about methanol, pure methanol has a freezing point of -98*C, which should rarely be a problem in an insulted tank. But the methanol/h20 mixture we are likely to use (<90% methanol) has an even lower freezing point of -145*C, and is not likely to ever freeze.
As for forming methanol, it is fairly easily done with methane and water vapor in the presence of a nickle catylist. I can go into the specifics if you like.
I think there is some misconception as to how a hovercraft actualy works. It does not blow out so much air that it supports itself by that lift alone, that would be more like a VTOL vehicle. A hovercraft works by containing a region of high pressure air within a curtain of high pressure air that is being blown out through the skirt around the vessel. The skirt only puts out enough air to maintain a region of higher pressure around the edge to contain the inner area. The craft is actualy supported by the high-pressure air inside.
I don't see any reason why it could not work on mars (or anywhere else for that matter, even in a vacume). But I don't think it would be very efficent. Certianly drawing in enough low-pressure martian air to support the craft would be a problem.
I'm sorry you don't like my calculations but they are correct and they do take into account other gasses in the oxygen/fuel mixture. The problem with internal combustion engines is not fuel but oxygen to burn the fuel. My calculation is based upon a very small engine and assumes that only 20% of the cylinders gas intake is oxygen.
How does combustion of methanol yeild 20 MJ/kg? Combustion in what size engine?
What size engine do you plan on using to get 50kw day and what percent of that engines intake volume do you think will be oxygen/fuel?
You are just simply incorrect on this. My method of calculation comes from simple stochiometric analisis of the situation. The only variables are the necessary energy consumption of the rover, and the efficency of the engine. Good estimates can be found for both of these figures. Where do your estimates for oxygen taking up 20% of the cylinder come from? At what pressure is the oxygen at? And in what condition is oxygen storred in the tank (pressure, temp, ect)? Knowing that volume of the tank is nice, but without some more data, I cannot figure out how much oxygen is actualy in there. I would be happy to do some calculations to show how your figures for combustion and fuel consumption work out, but without this data, I cannot even attempt it.
The combustion of methanol yeilds 20 MJ/kg. This is based upon the bond energies in the rectants (methanol) and the products (CO2 and Oxygen). It is a simple thermodynamic constant. It is the same on Mars as it is on Earth. And it is the same in a small engine as it is a large. It would take quite a lot of space to work out the calculations, but here is http://www.avogadro.co.uk/calculations/ … tm]website that shows how it works out. It gives a value in kJ/mol, I'll convert it to MJ/kg for you here.
680kJ/mol x 1mol/32g x 1MJ/1000kJ x 1000g/1kg = 21.25MJ/kg
Yout take the enthalpy of combustion -680kJ/mol (from the website). It's value is negative because the combustion gives of heat, but we can disregard that for our purpouses. Dividing by the molar mass of Methanol, 32g/mol gives us the amount of energy in kJ/g the conversion from kJ to MJ and g to kg cancle out, so our answer comes out to 21.25, even better than my initial estimate of 20MJ/kg. I should also point out that the enthalpy of combustion of methanol is EXACTLY the same as that of the reaction that occurs inside a methanol-oxygen fuel cell. In fact, while the method of reaction is diffrent, the equation is exactly the same.
I did not discuss engine size, in my post, because it is not relevant to the amount methanol and oxygen you need to combust to get 50 kWh/day, which is strictily an issue of efficency and thermodynamics. However, it's mass and volume would be considerably lower than that of the fuel cells you would need to get a amount of energy. A ICE can generate as much as 1000W/kg of mass (including transmition), but a heavy duty and more complex engine such as on the rover might get only 500W/kg. Turbine engines can perform much better, as much as 1-6kW/kg, but there design could be tricky, and there transmitions are typical much heavier. A Methanol-Oxygen fuel cell can only generate about 100W/kg, 5 times less than an ICE.
Anyways to Generate 50kWh/day you need an engine capable of generating 2kW. An ICE that could do this would mass only 2kg! The fuel cells would mass 20kg. I do not have figures for size on hand, but it is fairly obvious that the ICE would be smaller as well.
As to the specifics of the engine design, I'll admit, I have little clue. I am an chemistry student, not an engineer. However all the engineering is in the end based upon the chemistry I illustrated above. The fuel consumption is dependant upon the efficency of the engine, the amount of power that you need to generate, and thermodynamic constants. With good estimates for all these, a good estimation of fuel consumption can be generate without actualy designing the engine.
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While doing some research for this post, I did come across some intresting statistics. It may turn out that a turbine engine may be one of the best energy generation methods. Not only can they potentialy offer the greatest power density, a turbine engine also has greater efficency than a ICE, potetialy comparable or even greater than that of fuel cells.
Another thought that came to me is that methanol is probably generaly supperior to methane as a chemical fuel, regardless of the method of how it is used. Not only is methanol easier to store than methane, it's also allows you to shift more of the fuel mass over to methanol, since less oxygen is need for combustion per unit of methanol. Now overal, you do need more fuel, due to methanol's lower energy density, but it is certianly a very viable option.
The problem with your numbers Dook, is that your method of calculation is simply incorrect. Combustion only takes place in a small fraction of the space a cylinder, the rest of the space is taken up by other gases which are heated by the combustion and expand. Only a small spurt of fuel is injected every cycle, and even in our terrestial atmosphere (which is only ~20%) oxygen, only a small fraction of that is actualy combusted. On a mars rover, the vast majority of the volume of the cylinder will be filled with inert CO2 gas from the surrounding atmosphere.
Here is a better way to calculate the fuel consumption of a combustion engine.
I'm not sure what you have calcualted for daily energy requirments for a martian rover, but the estimates I have seen tend to run around 50 kWh/day or 180 MJ/day. Combustion of methanol yeilds 20 MJ/kg, giving a daily energy requirment of only 9kg/day or 126kg over a 2 week expadition.
Methanol combusts according to the following equation:
2CH3OH + 3O2 -> 2CO2 + 4H2O
giving you a ratio of 3O2 atoms for every 2 Methanol atoms. Since the atomic weights of methanol and oxygen are the same, the necessary ratio of oxygen to methanol is a simple 1.5. Thus, you need 189kg of oxygen for a expidition.
All of this assumes 100% efficency in your engine. Of course, ICE while they have other possative attributes, the best of them only average around 40% efficenct due to a number of issues (friction, incomplete combustion, ect...). However, even with this rather large inefficency taken into acount, ICE still do fairly well, needing 315kg of Methanol and 473kg of O2. For a total tankage of 788kg of fuel over a 2 week stay. This is a little heavy, but certianly do able. Even with higher inefficency figures for a ICE engine of 25% it is still a achiveable 1260kg.
Now, I'm not sure how that ~12 million in^3 of O2 is measured (is that 12 million cu. in at STP?), but in any case the the ammount of fuel necessary for a ICE is certianly do able.
Now, I did all these calculations for Methanol, but methane gets slighly better results (due to it's higher combustion energy), however the tank for will probably be heavier. Which one is actualy supperior probably depends upon the exact specifications of the vehicle.
I wrote about this a long time ago http://www.newmars.com/forums/viewtopic.php?t=3451]here
But to sum it all up again, I think the problems with navigation are overblown. With good maps, and a internal navigation system, it should be fairly difficult to impossible to get lost on Mars. Certianly a full blown GPS system is overkill. Just practice the same orientering skills we do on Earth.
I don't normaly double post, but I didn't see your reply untill my was posted. Weird that we would make such similar and opposing positions in such a short period of time.
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Anyways, about gas-stations, it occured to me that if you had a ready supply of water back at the gas-station there would be no need to haul the water back with you, which could signifigantly increase the rovers range. When you are carrying the water you are essentialy having to lug a full tank of gas both ways. The water at the station could be provided by a local source, or transported from another source in a logistic train sort of style.
Also while I don't favor batteries, a potential solution to having to hang around and wait for them to charge up is to have a ready set there waiting for you, which the reactor had already charged up. You get there, pop out your batteries (which should be simple), pop the new ones in, set the old ones to charge, and away you go.
I appolgise for some of the confusion I may have caused, I have a tendicy to see "fuel cell" and think battery, when in fact the two are very diffrent things. While batteries are almost certianly unworkable, fuel cells may very well be usable, however I still favor a ICE for a number of reasons.
While it is true that fuel cells are more efficent than conventional combustion engines, you must have a fuel cell that is signifigantly larger than the internal combustion engine you could get away with. This allows for a more powerful engine, that is both smaller and lighter than it's fuel cell counterpart. A more powerful engine gives you both greater mission capacity, and a greater safety factor. I especialy belive that a high performance engine will be critical for a martian rover, to allow it to travers difficult terrain while carring heavy loads.
Another issue with fuel cells is the issue of fuel purity. The high efficency fuel cells that most propose to use are fairly sensative to their fuel make-up, if stray chemicals (such as CO) were to get into the tanks, it could damage or even disable the fuel cell. ICE engines are pretty much immune to this problem, they will run on just about anything that is combustiable, and it is hard to imagine a chemical injecting that could damage the engine.
Another point in favor of ICE engines is relability and safety. While a ICE may have more moving parts that a solid state fuel cell, these are devices that have been around for about a 100 years, their operation is very well understood, and they can be designed very reliably. Fuel Cells, being more recent technology, cannot bost the same relability that an ICE can. Also, if the engine was to break, repair is at least conceviable, unlike with advanced fuel cells where repair is pretty much impossible.
All this is not to say there are not drawbacks to an ICE as opposed to fuel cells, but I belive they can be minimised. Fuel cells have the potential/necessity to be linked in series which allows continued power generation in the event one of the devices fails. However, due to ICE supperior power/weight ratio, you could simply carry a back-up engine, and still come out ahead of the fuel cells.
The increased inefficency of ICE as opposed to fuel cells could also be minimised by the proposal I made. With fuel eliminated as a cause of concurn by a towed reactor/ISRP the supperior power/weight ratio of ICE engines becomes more atractive.
But again, to me the best argument in favor of a ICE is the ability to have a more powerful engine. Mars is a rough and rugged planet with no roads and pleanty of obsticles. Rovers will be called upon to carry heavy loads over difficult terrain. If your rovers engine is not powerfull enough to cross a section of terrain or a steep gradiant there is nothing you can do about it. That part of the planet is simple inacessable. A ICE allows you to have a more powerful engine for much less mass than any other sort (well I guess a rocket engine would beat it, but...) and that to me is what is most crucial.
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As to other power sources, I'm all for their utilisation, but we have to face the facts. RTG are great, and have excelent energy density and fuel efficency, but would have to be much to heavy to generate the necessary power.
Batteries have good fuel efficency, but there power to weight ratio is weigh to low to make long range travel possible. And they suffer from many of the same problems I listed with Fuel Cells above.
Nuclear isomers hold much promise, but the technology is still in it's infancy, and not even close to being ready for a mars mission. In addition, gamma radiation would be a serious concurn.
Likewise with fusion. The technology is simply not there. In fact, they are further behind than nuclear isomers are. In any case, a fusion reactor is likely to be far to large to put on a mobile vehicle, at least for the forseable future.
Anti-matter does deserve some serious consideration I think, however. Seriously! The amount of energy stored here is obviously enourmous, and we can already create and store small quantities of it for signifigant lengths of time (days). Penning traps are not incredibly massive, and it is conceivable at least that a trap small enough to fit on a rover and store the anti-matter long enough for a rover mission could be designed. The anti-matter could then be slowly released into a tungston block, where it would react and heat the block up. The tungston would be sumerged in a coolant, which it would heat and power a turbine. The block and the coolent should take care of most of the radiation as well.
This is not to say that anti-matter doesn't still have serious problems. It's never going to be cheap to produce for one. I think CERN said that they might be able to produce it at the cost of 100,000W for every 1W of anti-matter, a HUGE improvment, but still incredibly expensive. But I don't think it should be dismissed out of hand. It certianly is a potetial power source in the future.
GCNRevenger covered most of what I was going to say, I'll just extend it a little bit.
- I think you have misunderstood me on the whole fuel cell/solar power bit. What I am saying is that there is no way you could power a long range rover with solar power alone. Fuel cells work fine as a energy store, and you could surely power a long range rover off of them, but no way are you going to gather enough energy with solar cells to charge them up for continuous opperation.
I perfer chemical energy to fuel cells as energy store due to their greater energy density, and the easy with which they can power a high-performance engine. However fuel cells do have some things in their favor, for one, recharging them via hydrolisis is much simpler then the sabatier process necessary to produce more chemical fuel. Either could readily be charge up by the nuclear power system I proposed.
- The point of the system is to produce great quantities of fuel, which is the biggest limiter, to allow unlimited range. The sabatier process does not produce enough oxygen for optimal combustion in any case, so an additional means of producing oxygen will probably be necessary. The fact that the crew can breath the excess is just gravy.
- As I said above, the reason I favor a chemical power store (such a Methanol and O2) is it's greater energy density. Despite the need to carry both the fuel and the oxygen, chemical energy is still signifigantly more energy dense than either fuel cells or simple batteries. But either is certianly do-able. Both would eliminate the need for a ISRP, but I'm not sure this would make up for the loss in efficency. Also, the hydrogen for the sabatier process would probably be stored as water (reclaimed from the engines after combustion), and broken into hydrogen only when necessary, to avoid having to carry hydrogen tankage.
- While this system is probably to heavy for an inital mission, there is no reason at all it could not be sent on a latter mission, or to an established base camp. Idealy the trailers could be hitched right up to one of rovers already sent to Mars, making it an easy expansion of mission capabilities.
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GCNRevenger, I like your "gas-station" idea. Kind of like how you can cross a desert, or climb a mountain by setting up a chain of supply stations along the way. It would be even more ideal if the stations were set up next to a convient source of H2O, so that hydrogen losses could be made up for. These gas-stations would be natural steping stones to full-fledged bases in the future, an ideal way to expand.
A nuclear powered exploration vehicle is possible but not efficient when compared to a combined fuel cell and solar powered one.
I don't know about that. It's probably not possible to power both propulsion and life support systems off of solar power alone. It is difficult enough to manage propulsion alone of a system on Earth, let alone on Mars, where the sunlight is weaker. Adding the power requirments of life support, and it is pretty much impossible, especialy when you need a high performance engine to move a realitivly heavy rover over rough Martian terrain. I mean look at the Solar Racers, those things use every weight saving trick in the book and still have some difficulty a single rider over smooth roads.
But fuel cells augments with solar power are propably far more efficent when it comes to being an energy store than a nuclear reactor, since the reactor has to carries all the fuel necessary for its entire life in addition to a heavy reactor. So in the short run, fuel cells (and chemical stores) are supperior. But nuclear power offers potential unlimited range, which other sources cannot match for any amount of mass. So in the long run, nuclear power is more efficent by default. The question is, will rover excursions be long enough to make nuclear reactors worth it. I think initaly no, but eventualy yes, you will want rovers that can traverse the entire planet if necessary.
Where does the crew move out to when the reactor is running?
Under my proposal the reactor is carried on a detachable trailer which is depositied a safe distance from the manned rovers (behind a hill or something) and then activate remotely. After the reactors buisness is done, they deactivate it, go back, hitch up the trailer, fuel up and move out. The rovers themselves are chemicaly powered, with the reactor producing the necessary fuel for them.
Failing that, a reactor would have to carry some neutron shielding to protect the crew. This is probably do-able (vehicles on Earth do it) but it would adds mass, and would best be avoided.
Oxygen can be produced. How so? The carbon dioxide to oxygen conversion machines produce such a small amount that it would take 144 of them to produce enough oxygen for one sleeping human.
With the several kW of power that a nuclear reactor would provide, you can utilise much more industrial methods of oxygen generationg. Such as the sabatier process and electrolisis or carbon dioxide electrolisis. The sabatier process will be necessary to produce fuel in any case.
Also the weight of the smallest reactor is one ton at least. This means that you have less than a ton to build the rest of the vehicle out of or it won't be within the Mars Direct weight limit.
This is very true. I figure the reactor and propelent plant would probably mass as much as 5 tons as more. The probably could not be brought on an inital mission, but they would be ideal items to bring on a later mission or a cargo mission.
Methane powered? I thought you were promoting nuclear power?
Chemicaly powered rovers, that tow a nuclear reactor that the utilise to produce fuel when necessary.
However, another idea is a larger "expedition class" rover that would be powered by nuclear power alone. It would trail either a cargo trailer with water and supplys or a drilling rig to get some more water. A pair of such rovers could probably traverse the entire planet safely.
It becomes more difficult to build a robust tank the bigger the tank becomes. Building a small robust tank that only has to hold say 10 cubic feet of air is much easier than a larger tank that has to hold 100 cubic feet of air at the same pressure. I have no doubt that a small tank could be built to withstand practicaly any force that could be subjected to it, but a large tank is a diffrent story. For any compressed air vehicle to have any kind of range it is going to need a pretty big tank, under fairly high pressure. On mars this is even more true as the requirments for endurance and performance are more stringint then they are on earth, all of which pressure a larger tank. Since you are also seeking to keep mass down, this is yet another pressure that makes for a rupture prown tank.
Also, the larger and weaker the tank, the more likely it is to rupture in an explosive fasion, then it is to contain the site of the leak and take of like a rocket. A weaker tank has (obviously) less body strength, and so is not able to withstand the forces trying to expand the size of the whole, so the whole expands rapidly and the tank ruptures.
Thridly, you would be supprised by the kind of pressures a vehicle can experince during a traumatic accident. Although much less speed is involved then in a bullet impact, much, much, much greater mass (tons as opposed to grams) is involved, so often times the force is much greater.
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In a CA vehicles favor, the lower martian temperatures would make it easier to compress and store greater quantities of air. Also, since you generaly do not have to worry about two-car accidents, the magintude of possible accidents is greatly reduced.
I'm not trying to say that CA vehicles are impossible, they are very possible. I just doubt they would be usefull as replacments for long range rovers. As vehicles with tanks of practicle size will not have the necessary range or performance. For scooting around the base, they might be great.
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Oh, and for some who are confused, the point of a CA vehicle is not that you compress air as you go and use that to power your engine. You use the compressed air as an energy store, using your bottle tank of it to power you vehicle. You then travel to your base (where you persumably have excess power), and fill up the tank from a compressor.
One of the problems I see with using compressed air is the potential for a disterous explosion if the tank is somehow punctured. If the tank was to be punctured, it would probably rupture in a horendus explosion that would put anything that any chemical engine could conceviable produce, because there is little way for a chemical engine to release all that energy at once.
The same problem exists for another potential energy store, flywheels. If for some reason the flywheel was to be damaged, you could have a serious disaster when all the energy was released at once.
But if you can succesfuly contain that energy, compressed air could probably be usable, for short distances at least.
I think the key to long range ground travel on mars will be convoys of chemicaly powered vehicles towing nuclear reactors and propellant plants. This should help to solve the problem of neutron radiation. When a nuclear reactor is shut down, the neutron flux is MUCH lower, pretty much negligable, so it could be towed a short distance from a vehicle. When the convoy starts to reach the limits of there fuel endurance they can stop, setup the reactor and propelent plant, fill it with their surpluse water, and move a safe distance away and carry out scientific activities. They activate the reactor remotely, and in a short period of time, it will have produced more than enough fuel to fill up there tanks. At which point, they can remotely shut down the reactor, approach it, fill up there vehicles, and move out. Oxygen could be produced at the same time as well.
The only remaining problems I see would be how to deal with the reactor waste heat (probably bulky and heavy radiator fins), and having a rover buff enough to tow the assembly which will probably mass several tons (just bigger rovers). Neither of these seem insolvable.
This would permit a convoy of methane/methanol powered ground vehicles to travel as long as there supplies of hydrogen/water (which should be recycled) and consumables last. Another limiter would be human endurance, both in the rather cramped quaters of a rover, and existing on an atmosphere of pure Oxygen, which is probably a bad idea for long periods of time.
Failing this, there is no reason why a chemicaly powered vehicle could not simply tow a large fuel tank behind it to help increase endurance.
The only problem with ground transport on mars is that some large sections of the terrain are probably dowright impassible, such as the Marineris canyons. Many obsticals can probably be avoided, or bypassed, but Mars also has some extream surface features that are contental in extent, and getting around them is bound to be very difficult.
It's not entirely true that we have only done the air-bag thing on mars. Both Viking landers landed sucssefully using mainly rocket engines for lift.
Also, on the thin atmosphere on mars generates so little lift, I do not think wings will be realy practicel there. The wing surfaces would have to be incredibly big, and the plane would have to very fast just to get off of the ground. Given Mar's low gravity, I think a verticle approach is probably the best.
Cant we just dump that white elephant into the pacific and do some real exploration??
Hmm... just like with Skylab eh? The Aulstralians weren't realy happy about that one.
Seriously though, the joke does bring a good point to mind, the public is not likely to be happy if the money put into ISS goes to waste either. Realy a lose-lose situation.
Alot of material here, this might require more than one post...
Thats what you get for trying to debate two groups of people at once. FWIW, I agree with you on the whole Mars Direct v. DRM thing. I would recommend picking up a copy of Mars Direct though, it's definetly worth the money.
In the long run, cargo and crew probobly ought to be separated as you say... but this is not the long run. You really have to weigh the extra expense of developing two different vehicles. Plus, a cargo mission and a human mission, without the aid of heavy tugs, do share alot of hardware in common. They would anyway probobly use the same launch vehicle at least to reach orbit, they will probobly use similar landers as the airbag landing aproach is not good enough for cargo, they will use the same OMS engines & aerobrake shield most likly... Putting some of the cargo and humans together saves having to send an additional cargo flight, and for pure cargo missions a HAB-less HAB lander/shield on the same launcher makes sense.
You are right, a crewed and a cargo mission will share much of the same equipment, which is why it makes even more sense to seperate them early on. The primary cost is the R&D of a new item, not just building and instance of it. And since they share so much of the equipment in common (same HLV, similar TMI stage, similar decent vehicle), paying the small additional cost to build, for example, a TMI stage that can do a minimum energy transfer orbit for the cargo or a faster one for personel makes more sense, since building another TMI stage is just a fraction of the cost of designing one that can do both (or two similar ones).
Now, while it might cost slightly more to send two missions, you get many other benifits for this as well. Primarily safety, if you seperate non-vital cargo from the primary mission, thats more mass you could spend on safety equipment. It also helps to bring the overall mass down, which helps to mitigate the cost. Also, by splitting your mission like this you reduce the risk that a single accident will ruin the entire mission. And finaly of course, you end up with more mass on Mars, which is always a good thing.
I also disagree with you that a 500km exploration radius from the landing site is good enough; we want to explore Mars, ALL of Mars, and that means going almost anywhere on the entire surface. Not 500km, but 5,000km would be a good figure if you are going to limit yourself to one site. A rover with that kind of range short of nuclear powerd would be impractical.
Well I would argue that is an aweful lot of ground to cover, ~785,000km^2. A team would be hard pressed to cover even a fraction of that in the two years they are to cover it. They would have to cover over 1,000km^2 a day to do it all (assuming a 500 day mission).
But even so, since the infastructure is developed gradualy, there is no reason we have to expect to explore it all in the first couple missions. Assuming a reusable MAV takes about 6 years to develop teams could be out exploring all of Mars after only 4 missions, the secound team would just be arriving home by this time, and everyone else would have the whole plannet open to them. And the savings they would have in mass and money are huge, as are the increases in safety and science. All for only a two mission delay in getting the "real science" started.
The key to an infastructure development plan is the sooner you get the material on Mars, the sooner you can start saving money. The sooner you put the heavy science equipment up there, the sooner it can be used, and the more you can use it. And the less material that has to be duplicated in future missions, the more NEW material you can send, compounding the effect further. That is why I support infastructure development starting from day one on Mars.
There is finally a question, how safe is safe enough? How much safer does "stacking" old HAB modules, ISRU plants, and reactors make the mission? Is it not safe enough without this option? Is it worth the huge loss of science and inspiration of exploring Mars to be just that little bit "safer?" I think that it is not... Somewhere, sometime, you simply do have to trust that a system will work, and I think that one set of equipment with an anytime-return ERV is safe enough. Nobody said this would be a safe endeavour.
When exploring another planet, you can NEVER be safe enough., the question of course is what does that additional safety cost. But when doubling the amount of safety a crew has to rely upon cost you so little, why not do it? And why waste the mass on future missions by sending the same stuff you already sent to Mars before, when it is sitting right there on the planet waiting for you? You could be sending new stuff, expanding your capabilties for science and other endevors. Scattering your mission out about the planet may enable you to collect data from other parts of the planet that may not inital be avaliable, but I do not think it is worth the enormous waste in mass, nor is it as safe as single mission approaches. And by bringing new equipment to the site (instead of repeats of old), you add the ability to collect new kinds of data.
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I actualy think we are pretty close to agreement on these issues. We both understand that value of infastructure on Mars, the diffrence is that I don't see any reason to wait for some arbitrary date/technolgoy to establish a permanat base and start building the infastructure up. You get maximum benifiit from doing it on day one. As the technology advances as new methods of delivery become avaliable, by all means use them. But waiting untill those are avaliable means wasting all that money you could have saved by sending it earlier. As I showed before infastructure (like a big permanat nuke) could pay for itself very quickly, and these savings are not dependant upon advance deliver options, so why wait for them?
Just to give you an idea, this is how I would develope infastructure on Mars.
Cargo Mission 1:
A pair of pressurised long range rovers, the mass that is saved from sending them with the crew is spent of safety and reducing the mass.
Cargo Mission 2:
Heavy drilling and Earth moving equipment, with two rovers already on mars, there is no point in sending another one.
Cargo Mission 3:
ISPP, and air liquification facilities, these should help to reduce the amount of LSS equipment that has to be sent from Earth.
Cargo Mission 4:
Large Nuclear reactor, which should eliminate the need to send nukes on later missions.
Cargo Mission 5:
Reusable MAV, which gives both global range, and eliminates the need to send single use MAV vehicles.
And so on... with the exceptions of mission 4 and 5 all of this equipment is fairly low mass, probably under 10 tons. I like the idea of 20-40 ton cargo missions which gives pleant of space to send spares, supplies, back-ups of key infstructure equipment and so on. Under this plan the Mars base has much greater capabilities, and is safer overall. And little is sacrificed.
well you knwo what they say....
Theres no such thing as bad publicity.
Funny that you should say that. Normaly I would agree with you, but I don't think that saying applies in political situations such as this. When people are called upon to make a yes-no decission like about the ISS station or a political canidate, influencing them in a negative manner in not productive. This is diffrent than most product marketing, as when a person is required to make a selection from a group of choice (such as products to buy) name recognition can be more help-full then the negative conitation in some cases.
OTOH, dropping the ISS is just what the space program needs to realy get rolling again, so maybe this is a good thing in the long run.
Early on, particularly when we are in the exploration phase and not the development/colonization phase, building infrastructure shouldn't really be much of a priority, particularly when the cost of getting a pound of anything from Earth to the Martian surface is going to be so high. We should wait to begin real development until later, when launch prices have declined an order of magnetude from what they are now (either by HLLV or RLV), reuseable cargo-carrying MAV vehicles are practical, and ice deposits secured either on Mars or on Phobos & Deimos. Right now with a large HLLV rocket, a beefy/reliable/accurate but expendable lander, and an aerobrake shield on every mission, you are looking at around $1.0-1.5Bn just to get one payload to Mars.
This is why I advocate seperating cargo flights from manned return flights. To help cut costs. The cargo flights do not have to be man-rated, they can take slower orbits (requirering less fuel and a smaller heat-shield). Also cargo flights have a redudency that manned flights cannot match. If they blow up/fail you can just launch the same-stuff at the next launch window and still play with it durring some of the mission. If a crewed flight fails, you can't send those people again, they are dead. Seperating crew and non-vital equipment like this allows you to focus your safety money where it is most effective as well.
I think it is also important to note that reducing the cost to put payloads on Mars will be a gradual process just as the buildup of infastructure will be as well. So these two synergise well with each other. While the costs are high only the most vital and most dramatic cost cutting equiment can be sent (propelent plants, reusable assent vehicles). As the costs come down, more and more infastructure can be pilled up on Mars at both reduced cost AND reducing the amount of stuff you have to send in the long run. Infastructure development may cost more early on, but over the long run you should come out ahead.
The large amount of time inbettwen missions (at least 1.5 years) also makes waiting for cost-cutting less important, as the cost-cutting technology can be developed in tandem with infastructure development. There is no reason to wait for the Nuclear Electric or Solar Sail cargo stage to be developed to send infastructure. Send you first load with the first mission, then later modes can take advantage of the better modes.
So, in order to maximize scientific return and to generally "take along" the taxpaying public in exploration by proxy... seeing Astronauts taking (multispectrum) photos on the edge of Marineris, the dark sands and microbe hunting at Hellas, taking ice samples from the Martian north pole for analysis. Inspiring stuff... limiting early Mars missions without a reuseable MAV and associated fuel supplies to a single landing site is a bad idea.
I agree strongly with this, a reusable MAV vehicle should be the number one infastructure priority. Unfortunatly it is probably the most expensive to develope, and the most inherinetly unsafe. Untill a resuable MAV is deployed however, long range pressurised rovers should still give the crews enourmous amount of area to explore. Mars direct calls for rovers with 500km round trip endurance to give an example. Nuclear powered rovers could do even better, and rover endurce should be extendable with later infastructure investments (towable ISPP, extra tanks, ect). Even without the global mobility a MAV provides, the team should have pleanty to explore, more than enough to last several mission I would think. And stacking infastructure at one location offers a safety net that cannot be beat by solo missions.
I disagree, the super-light-weight space nuclear reactors are designed for high fuel burnup rates to keep their weight/size small and decay heat down, they actually do go through their fuel pretty fast and can use it up pretty quickly. A submarine reactor is a bigger, heavier beast where you obviously don't have to pinch kilograms, a small space reactor probobly won't produce full power for much longer than five or six years or so.
If the reactor is turned off (ie. chain reaction inhibited) the fuel supply should last quite a bit longer. Rember if the chain reaction is not occuring, then the fuel source is only subject to normal decay. While earlier reactors may still have limited life spans, it still offers a follow up mission double redudandcy that they could not possibly afford to take with them. This is one of the key benifits of stacking your assets at one site. It offers an increase in safety that solo missions cannot even come close to matching. A later cargo flight could possibly bring a more heavy duty/long term reactor with it which could eliminate the necessity for later missions to bring one. This could saves both weight and cost, and the earlier you do it, the more cost and weight you save, which is why it should be done as soon as possible.
For example, lets examine the advantages of landing a heavy-duty reactor on Mars. Lets assume this reactor weighs 20 tons, cost 500 million to build, and 1.5 billion to deliver on Mars, for a total cost of 2 billion. While a normal reactor weighs only 5 tons is developed for free (since one will have to be developed in any case), and is delivered on Mars at the cheaper cargo rates, which would be 300 milllion. After the big reactor is delivered on Mars and the little reactor no longer have to be delivered it will pay for itself in 7 missions, which would only take about 8~9 years under my schedule. If such a reactor could under such requirments (which doesn't seem to difficult), the economic advantages are clear, everything past those 9 years is just gravy.
I'm also pretty dubious of the usefulness of an old HAB module, which will be fairly cramped, probobly won't have that good a radiation protection, and will already have been lived in for the better part of three years and stored up to two. Later on, when signifigant "Mars-moving" equipment is available and more than basic minimal mechanical facilities are available, then you could bury the HABs and clean them out (disinfect) or patch up old LSS gear, but by then we ought to have a reuseable MAV anyway and won't have any more Earth/Mars transit HABs. Bring & bury purpose built inflatable/rigid foam filled HABs later, big ones with plenty of space designed for long life, and don't bother with the little cramped Explorer HABs scatterd around.
Well the Mars moving equipment will never get to Mars if you don't send it! But seriously the hab structures and life-support systems are going to have to be pretty heavy dutty equipment in the first place, once you reach a certian duration, there is less diffrence bettwen a hab and lss that can last for 3 years and one that can last for 6 or more. But the possible savings in mass here are great, as the hab is the single largest item that has to be sent to Mars. The cost of replacment parts, lysol, heck even an entirely new LSS are small in comparision. If the astronaut can travel in a space only lightweight inflatible hab, and transfer down in a cheap lander a great deal of mass can be saved. And it generaly results in a net increase in living space and safety, as opposed to solo missions. By the 3rd mission when there are 3 habs on mars the living space is greatly increased.
But as far as it goes, building a heavy duty hab on Mars is a great idea. The cost advantage is less dramatic then that of the nuclear reactor I mentioned earleir, but still would pay of in the long run. But again, the sooner you start on the hab, the sooner the astronauts have a safer place to stay, and the more money you can save.
i`m even thinkin we oughta configure an unmanned probe this way, munus seat, pedals, enclosure,etc.
I'm dubious about this. A recumbent tricycle still relies in large part upon it's rider for active balance, espeicaly upon rough terrian. A rover has no easy way to simulate this (I mean you could use gryscopes or what not, but that would be heavy). Without active balance, a low center of gravity and more points of stability are even more important, and most small rovers have more than enough power a 4 wheeled transport, I mean they are rolling around up there right now. Why mess with what works?
Problems I see with the idea.
#1. As the farscaper mentioned, stiffness of the suits would be a major obsticle. As an avid bike rider knows, riding a bike on rough terrain requires a good amount of physical agility over the whole body. The rider would probably spend more energy working against the suit, then he would peddling, in this is the case, walking might be a better method.
#2. High speed accidents. Falling off a bike is bad enough on Earth, but it could be disaterous on Mars where a suit rip could spell doom. While Mars has lower gravity than Earth, a heavy body in motion still has intertia, which could cause a lot of damage if the rider was to lose control, which could definetly be a problem on rocky martian soil (heck, I do it sometimes on flat concreat, so go figure).
#3. Purpouse. What exactly would these bikes be used for? On an early mission the crew should probably not be going to far away from base-camp or a rover for safety reasons. With limited destinations none to far apart, a bike becomes less usefull. Also since lopping/skipping is a faster and more efficent stride on mars, and requires little physical agility, it may be more attractive for medium range transport.
#4. Loss of toqure. On earth a rider can generate alot of toqure by using his bodys weight to push down on the pedal. This is most usefull in off-rode/rough rode riding where toqure is most necessary. On mars where such conditions are universal, the loss in gravity hurts this affect. Sandy soil also agrivates this problem.
#5. Safety. Safety must be a primary concurn on any martian mission. I mentioned these concurns earlier, but they are worth repeating. Operating a bike could be very dangerous for an its riders. It is inherintly more accident prone then walking, and produces accidents of greater severity than walking could. Because of this, biking expidtions should not be alowed to transpire long distances away from a pressurised safe area. This should apply to foot travel as well, astronaughts should not be allowed to travel solo long distances away from the help the might need if there was an accident.
Solutions for some of these problems.
#1. This is the toughest, by sitting the rider down and adding more wheels the requirments for physical agility are lessened, but not eliminated. This arangement also makes the rider lose the toqure he could gain from his weight.
#2. The solution to this problem is the same as number one. Add more wheels, and it has the same additional problems. But lowering the center of gravity and adding more stabilisation points are the only solution to loss of balance.
#3. While I do not see a use for bikes to engage in long range solo adventures, that is not all they might be used for. One idea that springs to my mind is the transportation of moderatly heavy equipment. A "bike" could tow a trailer of some sort which could contain addition equipment. Two such riders (perhaps in a tandem vehicle), carring additional life-support and science equipment might even be allowed to conduct recon short distances from the base (like say maybe 30k or so). This might be useful for taking multiple soil samples around the base (while the rover is out on a expedition), or montoring/repairing seismic/weather stations (although this could probably be done mostly via radio). Anything that lets the crew get more excersise is usefull as well though.
The problem with this, is that there may not necessarily exist a need to transport moderatly heavy equipment from one location to another, at least not on such a regular basis to justify a bike. And, adding mass (such as a trailor) increase the amount of toqure the riders must generate to accelerate and manuver on rough terrain.
#4. I actualy have a solution to the toqure problem though. Modern electric assitance motors already exists for bikes. They are fairly compact, pretty reliable, and can generate additional toqure for the rider. They are totaly self-contained, recharged by the riders peddling. A device such as this could be easily attached to any bike. Big/multiple tires can also help to a degree, but do big and to many, and you start to increase the amount of forces necessary to move the bike.
#5. I belive my solutions to the safety problem can be addressed by simple mission planning. No riding at high speed of dangerous terrain. Stopping is going to take longer on mars due to lack of toqure, which should be taken into consideration. No solo expiditions great distances from a base and help.
Mars Direct has some good points and some bad points. As a mission plan I think it is unworkable, but it does set the right mindset for a martian space program. IMO the Mars-Semi Direct takes most of the problems and corrects them. My biggest worry was alway crew size, Mars Direct uses a crew of 4 because that is what the mass allows, not because 4 is what is needed. 6 people is a much better number IMO.
The only infastructure changes I would make is to build up more of a plan to build infastructure at the primary base. A desirable base location should be scouted before the first mission (should not be to difficult to do with unmanned probes), and all subsiquent mission should be direct there. This makes for a small loss in science, but a HUGE gain in mission infastructure.
With a plan like this, it is possible to man the base on a more rotational bases, so that at least some of the time, two teams of 12 people will be there. I would aditionaly launch at least one unmanned cargo flight every launch window, containing vital infastructure equipment. These would allow the (larger) manned launches to focus more of there mass on important safety concurns, while extra base infastructure (which is nice, but not vital to survival), would arrive seperatly.
By infastructure I am talking about things like Rovers, Proplent plants, Greenhouse domes, extra nuclear reactors, air-liquifiers, and (hopefully), a reusable martian assent vehicle. None of these things are necessary for a succesfull mission, but there presence on Mars can multiply the effectivness of later missions. Landing at one site maximises the ability to build up this infastructure and in the long run, allows you to get more science done for your dollar.
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Some negative comments have been made about re-using old mission infastructure (habs and such) and later missions. I belive these are unwarnted. The nuclear reactors a mission would bring with them should produce usefull power for much longer than the 3 or so years that would be necessary. Navy nuclear vessles go about 20 years bettwen refulings IIRC. The habs should definetly stay air-tight, and since the missions are dependant upon life-support systems that can function independently for 3 years or so, expecting them to last longer with a little servicing is not to much to ask. In any case early missions can bring the heaviest parts (like the hab shell), while later missions may only be required to bring less heavy replacment parts. Having a team currently on the ground to determine the status of a spare hab should also help (which could happen by the 3rd mission under my plan).
Even if possible to construct it, IMO it would be the biggest of terrorist target ever and would be the reason for why I would not build one here currently even if it could be done.
I'm sorry if I came across a little bit rude, but my comments were in direct response to comments like this one. Which was EXACTLY the attitude I was talking about.
I'm all for taking terrorist considerations into acount, but they are no reason hold back a project. And I would also say that the potential for terroist launching a succesfull attack on a facility isolated out in one of the most deserted parts of the ocean, where all cargo to and from would be searched carefully, and security is omni-present, is pretty far-fetched.
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Back to the material side of things, we still have a ways to go, and it is not certian that we will get there. Most of the elevator proposolas I have seen call for wires with tensile strengths in the 120kPa range, while most of the studies conducted on nano-tubes so far are about half of that 60kPa. Quite aways from the 300kPa. And the problems of manaufacturing such tubes on such a large scale haven't even begun to be tackled.
On the plus side, most of the research being carried out on carbon nano-tubes is being done by chemical companies and universities, so the technology is fairly certian to be open to the public. Heck, outside of some radar absorbant coatings, most military materials technology is open to the public. Even the fabled chobam armor is no real secret. The exact make-up of the armor is, but there is nothing realy special about that ceramic composite armor that prevents someone else from making something like it, just the cost to develope it. And since the private need for such armors is rather minimal, no-one else has bothered to do it.
Meh... to me it's realy not worth a discussion. We still aren't there with the science to make such a space-elevator possible. Carbon nano-tubes and other such material sciences are making great leaps forward, but we are still quite away from producing wires (be they carbon filmant or otherwise) with the necessary tensile strength. Some of the test look promising, yes, but we have no idea if they will hold up when the wires are extended past the cm length, much less thousand of kilometers. And even if we had that tech behind us, we still would have to figure out a way to produce a wire of unprecendent length, and hang it from orbit. Quite aways to go.
Mars on the other hand is right there. We have everything we realy need to get there, we just need to put it together and go. An unfair comparision, IMO. One option is a mere long-range possibility, while the other is a close range with no technical obsticals bettwen us and success.
This is also a false delima, there is no reason we could not do both (well except for the fact that we could not actualy BUILD a space elevator yet).
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As for the terrorist issue. Not building something because you are afraid the terrorist will blow it up has to be some of the stupidest reasoning I have every heard. Lets not build any more tall-buildings, they are only targets! Lets not have any more children, bad people may kill them! Lets not earn and more money/buy stuff, thives will only take it. If you think like this, the "terrorist have already won." (God I had always hopped I would never have to say that).
Seriously you can't let concurns like terrorisim prevent you from going forward with a project. Be prudent and take it into acount, but continue to go forward. And a space-elevator should be pretty defensible. The plans everyone seems to be discussing calls for one isolated out in the middle of the ocean, making limiting access pretty simple. All cargo going up (or down I suppose) the elevator would of course be inspected and weighed to to the nearest hundreth of a gram. It is going into space where these sort of things are vital important. A terrorist smuggling some sort of bomb or weapon on board is pretty far fetched. And all passangers would have extensive background checks as a matter of course. Concurs about terrorisim are overblown.
I agree with you Comstar, but only to a point. Attempting to educating the populace is a wonderful idea, but hard to implement. The NASA TV channel is not even brodcast in my location. And it's hard to force people to watch something they don't want to watch. Simply put, it proves to be very difficult to persaude people through education. People don't have the attention span for it, and quite frankly logical arguments can be simply lost on people who simply refuse to accept them.
A more succesful approach is one either based upon emotion (such as the one JFK used), or upon hype. But there are problems with each. An emotional approach is difficult as it depends upon both the emotional state of the nation (which is currently focused upon domestic concurns), and empasioned leadership to support them (which is currently absent). Hype has the problem of not living up to it's expectations, and being only a short-term phenomina.
I think the best rout to use is sort of a stealth approach. A renewed mars/moon space program is going to have a length period of build-up before anything can be achived, this is when it is most vulnerable. Fortunatly, due to the reduced cost, all that is necessary (in the US at least), is a president with the will to fund it and a congress to back him up. George Bush could achive this easily if he wanted to, but apparently he does not (maybe after his possible re-election but I doubt it). However, when the progrem is ready to show some results, OR is running into trouble (in danger of being cancled) is when some hype about it should be generated, in order to prolong and preserve the program. This was the downfall of the Apollo program, all the build up was on the process of getting to the moon, after we got there, their was nothing left to support it's continuation. A rewned program should seek to avoid this.
A lot of good things have been said in this thread, and I think I would like to expand upon some of them.
#1. Other international politicians.
Comstar is exactly right, the politics of other nations is also important. As a American, I natruly am more knowledgeable about the politics of my nation, so I focus upon those. Here is how I see the status of the other nations and what (little) I know about there political situation.
Russia - the only other nation with signifigant space experience. While Putin I belive has nothing against space travel, Russia is current facing other problems which he sees as more important, such as a stuggling/developing economy and terrorisim. The current political spat we are having over the middle east doesn't help things either. I do not belive Russia could currently sponsor a resurgent space-program, but they do still have the potential to contribute to other ones.
Japan - while Japan does not have extensive space-flight experience, the nation could easily aquire the technical experince necessary to create one. Their aeronautics industry is not as well developed as some of the other players, but they are easily on equal footing in terms of electronics, chemistry, and nuclear engineering. I know little about the Japanese leadership, however nor am I qualified to make a guess as to whether or not the population would support a more ambitious space program. It would be a major break from there past trend. The country itself, while suffering from an economic dowturn, could easily support an ambitious space-program, if they decided to do it.
EU - The EU has lately made great strides in space-development. While still lacking the experience of the Americans or Russians, the EU has just as much techincal experience in all necessary fields. The political situation in Europe is much more complicated than that of the US, as they lack common leadership. A sucessful program would have to convince leaders in most of the nations that it is necessary. Economicaly the combined EU can easily support such a space-program, though it would be a strugle for any single nation.
China/India - while both China and India are making great strides in technical and economic development, both nations lag far behind the ones we listed previously. While a serious space program could be a good idea for both nations, given there lack of experience, it would be more a repeat of the 1960-70 then a step forward.
Prospects for International copoeration - the ISS a sticking issue currently hindering copperation. Politicaly the US/Russia/ESA have put quite a lot into the station, and backing away from it is painfull. The situation in the middle east is obviously not helpfull as well. Bad experiences with the ISS and current political tention make it hard to convince others countries to invest in a new operation. Change in US leadership might help with the political tension, but the ISS situation is more difficult. But perhaps in 2008 with new leadership in the US, and the ISS either done with or reaching completion, it maybe time to start a new wave of political coperation.
#2. Technology and the cost of space.
Advances in space technology have brought the cost of a serious space program down enormously. I threw out the figure of 10 billion a year which, properly spent, should be enough to get things rolling. This amount is down enormously from what our space program cost us in the 1960/70s. The sum is still large, but any of the G-7 nations could afford it without trouble, to the worlds most prosporus nations it is but a drop in the bucket.
However, these costs are still far beyond what industry or private organisations can be excected to pay. The cost needs to drop by at least two orders of magnitude for it to be even remotly possible. This is hard considering that the costs have dropped by at BEST only a single order of magnitude since it's beginning. For the immediat future (say the next 20 years or so), we can pretty much count out serious coprate investment in space. The costs will only drop to there level after the national goverments have spent the big bucks to bring the cost down more, buy developing infastructure, technology, and techniques.
#3. JFK.
JFK had a number of things working for him. The cold war, democratic control of congress, and others. I'm not going to say that his style leadership is what the space-program needs to get going, however. Firstly, the costs have dropped dramaticly from what he needed, so the same level of persausion in not necessary. What would be more ideal is a President like Bush or Clintion, who could at least convince the American people not to veto the idea at the start, and had a lock on congress and so could get it funded.
Another approach is a leader who could convince the rest of the world that this is something worth doing, but realisticly I don't think such a man exists. It's hard to convince one nation, let alone others. The most succesful approach is probably for one nation to develope a succesfull program, one that can succed on it's own, and offer other nations ways to held and expand upon it. If we depend on other nations for success, the possible of faliure looms large, as it does with the ISS. If we are determined to succed on our own, but willing to accept help, not only is succes guarteed, but even more can be achived. Of course, this costs more, but that is the price you have to pay.
I hate to get sidetracked on a thread I started, but I disagree dicktice. Space travel is so expensive that realisticly it is only the national goverments have the funding necessary to truely achive anything. I am a huge space advocate, and am more than willing to give of my time and money to the community, but less face it. I don't have 10 billion dollars to give, much less 10 billion a year. And 10 billion a year is what a space program realy needs to get the ball rolling.
You and I don't that have that kind of money. Most coporations don't either, and those that do, cannot spend that kind of cash without plans for an reliable plan for an even greater return on investment. Those kinds of guarentees do not existe for a space program, and neither does the potential for a 10 billion dollar a year return.
But community organisation is good. Goverments are motivated by the people, so if we get motivated, something should get done. And your suggestion is a good idea about how to do that. A amature space movie progect is certianly do able, and might very well get people excited about space again.
But some politicans are already excited about space now, and some never will be. What we need to do is identify who is which, and support the right ones. I'm a pretty die-hard Democrat, but I would vote for a Republican in heartbeat if I knew he was going to restore our space program.