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I don't know, I just have a hard time buying it. I mean it's not like the neutron radiation from conventional D-T fusion is that intense. So you have to replace parts of the reactor every 5 years or so, big deal, the parts would have to be maintained anyways. It is an additional cost, but surely it would not be greater than the extream cost involved in importing He3 from the moon. Even with highly evolved infastructure on the Moon, it would still be a very expensive proposition.
I think one of the aspects of fusion power that people have not considered is how it should dramaticly drop the price of electricity. People like Zubrin and others look at the current value of electricity, calculate how much energy D-T or He3 fusion could generate and spout, Egad! we could make money importing the stuff from the moon/mars (I think at one point Zubrin even advocated importing Deutrium from mars...).
But if fusion technology is achived, the price for a kWh should drop dramaticly, I mean thats one of the reasons we are developing it, right? I mean sure, deutrium is pretty expensive today, but thats because it is only refined in small scales. D-T fusion would increase the demand for it, which would seem to increase it's cost, but in-fact it should go down, as it enters mass-production AND the cost of electrolisis goes down with the price of electricity. Most projections have the fuel being a mear 1% of the electricity cost. He3 will be hard pressed to beat this figure.
Another problem with He3 energy from the moon is the whole chicken and egg delima. You don't need massive moon mining opperations unless you have He3 reactors, and you don't need He3 reactors unless you have the massive moon mining opperations producing He3. So a succesfull operation would not only have to run on a cheaper kw/KH basis then D-T fusion (a feat in and off itself), but also have to pay the cost of both constructing a reactor and the infastructure to suport it. I think this level of capital investment is the real killer. No new nuclear reactors are being built due to the steep up-front costs to construct them (for that matter few coal plants are being built for the same reasons). Instead natural gas plants are being built because a new plant can be built cheaper, even though it costs slight more per kW to produce the electricity.
I'm even question He3 utility in space. Again, while it is supperior to D-T in terms of specific impulse, and emits no neutron radiation, the fuel is still going to be costly. D-T may be slightly less efficent, but when your ISP's get up into the thousands (or even the millions) these diffrences become less important. For most inner system travel the fuel is going to be mostly inert hydrogen anyways. And this hydrogen can easily double as a neutron shield for the crew as well. In addition the crew will have to be shielded from space-radiation anyways, so the additional shielding does not necessarily have to be that great. So the question becomes, is the additional cost of the spacecraft's fuel worth the improvments in efficency? The answer is not a cut-and-dried yes, IMO.
Yet another point is that He3 fusion is not totaly free of neutron emission. While the He3-D reaction produces no neutrons, D-D reactions can be expected to happen witihin the reactor (although at a very low rate), and these reactions will produce some neutron radiations.
While I'm mentioning D-D fusion, it is yet another competor to He3 fusion that has not been mentioned yet. It's fuel costs should be even lower then that of D-T fusion (no need for lithium to make tritium), and it emits less radiation as well. It even produces He3 as a byproduct! I think D-D fusion will be the primary fuel for secound generation reactors, and our source He3 might come from them! It's potential in space is nearly as good as well. Other types of heavy element fusion (such as D-Li) could also be considered, if neutron radiation is truely such a problem (D-Li produces no neutrons).
I love the concept of He3 mining, but looking at it realisticly, it doesn't seem very practical.
Meh, H3 fusion is nice and all, but I wonder if mining it would ever be a truely worthwhile investment. I mean sure it's superior to D-T fusion (better kw/KG, no neutrons), but do these advantages realy make up for the steep diffrence in cost? I mean, the stuff has to be gathered up out of great quantities of dirt on the moon, and then shipped back to earth. This would make it very expensive. Surely conventional D-T fusion, or for that matter any other kind of fusion not relying on non-terrestrial elements, would be much cheaper. This would more than make up for the rather minor disadvantages (having to deal with the neutron radiation), invovled.
As the current political situation stands, the American space program is in a deadlock. President Bush's new space inative is a good start, but it seems to be a long term inative and not destined to bring in new results anytime soon.
I don't think we can really expect John Kerry to shake things up either. He will probably just leave us with KSC opperating as is and the US space-program quietly fadding into the dust.
So things for the next 4 years look pretty bleak. No matter who wins the next election, not much is likely to change for the better. But maybe there is light at the end of the tunnel. What politicans should we be looking out for in 2008 to realy breath some life back into NASA. Howard Dean has been noted as a strong space supporter, but are there any guys on the Republican side of the isle?
Wouldn't the use of CO2 reduce the efficiency?
Over what coolant and why? I assume at pressures at or bellow a one bar I assume CO2 would behave as an ideal gas and the main differences between the gasses would be their heat capacity. The heat capacity would be related to the gas constant. The main efficiency loose I see is the need for a compressor. Or would it be possible to build a condenser for CO2 on mars given its low temperature. I assume the pressure would have to be fairly high for the CO2 to liquefy. And if you had a condenser can you build a pump to pump liquid CO2. If you could build such a pump how reliable would it be.
The only real problem I see with using CO2 as a coolent is it's potential to transfmutate into radioactive isotopes. If it were to leak back into the atmosphere, or even worse into the life-support systems, that might be an issue, but on the whole, a rather low-priority one. Of course, the same thing is true for praticly any other coolent you might care to use (water, argon, whatever), except for helium which has an extreamly low neutron cross-section and does not transmutate very easily. But as nuclear reactors are designed NOT to leak there coolents, and it doesn't seem likely that any coolents leaked in such a manner could find there way into the life-support systems, this is all pretty much a non-issue.
It would be pretty much impossible for a reactor to get CO2 up to the temperatures at which it would decompose. If you DID get it hot enough, you probably be more worried about what was happening to your fuel and there containment (are they melting?) then the CO2 decomposing. It just doesn't decompose very easily. For use inside a reactor it should be just fine.
Now CO2 going into a liqued state is more of a concurn. Most mission are planned for the "tropical" regions of mars, where the temperature should stay above CO2 freezing point, but there could always be a cold-snap. It could also potential turn into a liquid if it is under pressure, but not heat, this might happen if you had to kill the reactor, for example. But since (as far as I know) CO2 is only being planned to be used as a coolent, and not a moderator, neither of these issues is truly critical. When the reactor resume opperation, it would naturaly heat-up and return to the gasous phase.
In addition, the Specific Heats of gasous CO2, Helium, Argon, and Nitrogen are all fairly close to one another. You might get a little more efficency out of Helium or Argon, but the diffrence isn't all THAT great.
All that said, I agree with Mr. GCN, you don't want to be adding coolent to you reactor during a mission. It a realitivly small weight saving (especialy if you are using a gas), and it introduces a whole other dimension of things that could go wrong.
Edit: posts by RobertDyck
http://newmars.com/forums/viewtopic.php?id=6101]Nuclear Rocket
Using CO2 as a coolent would fix the problem of aquiring coolent, but as it is vuneriable to changing into various radioactive isotopes, a secoundary cooling loop would probably be required. Or perhaps the CO2 could be vented frequently and replaced, although I am unsure as to how this contanimation might effect the mission.
I had also not considered radioactive dust inflitrating it's way back into the closed enviroment. I suppose this would be possible. Of course dust control is going to be a major issue in any event. some method of controling it will have to be found.
This would only be an issue if the reactor had a major meltdown. Which is possible, but unlikely for PWR and other types (they would need to both completely lose control of the reaction and lose coolent. More likely is some sort of coolent leak, in which case water is superior as it would quickly freeze and would be unlikely to find its way into the closed life-support system. Radioactive CO2 might pose a small risk of inflitration, but probably not a major one. It might complicate some of the plans for using the nearby martian air for fuel and such applications though.
However, even with the threat of nuclear contamination, I still think the biggest concurn would be loss of power. An early mission would be hard pressed to find juice for life-support without their nuclear reactors. And lack of air and heat would kill long before minor radiation contamination would. I'm not trying to downplay the threats posed by a possible nuclear accident, just saying that when added to the loss of power and life-support, radiation is a secoundary concurn on the martian enviroment. Any reactor will have to be reliable first and lightweight secound. The decision should not be made on the basis of which reactor has the potential to meltdown, but on which one is overall the most reliable and lightest.
Ahh well whatever is most efficent in terms of kW/Kg, be it PBR, PWR, BWR, whatever. In terms of safety and most other considerations they will all probably come out about the same for any non-terrestial enviroment.
A more intresting question to me is what sort of reactor would be simplest to build on mars. I have a feeling that it will be some sort of water cooled operation if only because the cooling medium will be easy to come buy and replace. I also tend to think that convential fuel rods will be easier to construct on mars rather than fuel pellets a PBR uses.
Any ideas where I can find some more good info on other liqued metal cooled reactors? I know the russians used them some (I think they even put some in there submarines), but thats about it.
Good article, I normaly don't like wired's reporting but this one was pretty decent.
However, I am uncertian as to if a Pebble bed reactor is optimal for an early mars mission. As this reactor has to be sent up from earth, it needs to be pretty weight efficent in terms of kW/kg. I have a feeling that a conventional water cooled reactor is going to beat it here.
In terms of safety I don't see a pebble bed or other gas-cooled reactors are going to have much of an edge either. Since the martian air is unbreathable and the planet is already bathed in higher than normal radiation a meltdown is of little concurn. The biggest worry with any reactor malfunction is going to be loss of necessary electrical power. I don't see how a pebble bed reactor is going to be any more reliable than a conventional one.
OTOH, the thing will probably be easier to fix if it doesn't blow-up in the first place, but modern well designed PWR (pressurised water reactors) don't do that in the first place. Worst case scenario, the vent radioactive steam, which is not a scary issue in the martin enviroment. As a plus, it would probably be easier to replace the vented water then it would be vented helium.
Just some thoughts.
Crackpot Index for gravity wheel.
-5 Point Starting Credit
53 = 53 Staments that are widely aggreed to be false, 1 point each
340 = 170 staments that are clearly vacuous, 2 points each
510 = 170 staments that are logicaly inconsistant, 3 points each
25 = 5 thought experiments that contradict real experments, 5 points each
50 = 5 new terms invented without defence (or even explination), 10 points each
20 = 2 claims that relativity is misguided, 10 points each
20 = 1 use of science fiction as fact 20 points
50 = 50 points for claiming your theory is revolutionary without concreate testable predictions.
Total: 1063, must be close to a new record!
Based from evaluation of website linked in orginal post.
I doubt the ISS station is built to withstand the rather large force required to kick it into Martian orbit either.
Well I think there is some potential to make a profitable show based upon a mars mission, I mean the logistics wouldn't be hard, I assume you're probably tapeing pretty much everything going down, so you'd just have to get the astronauts and the mission control/administration folks to give little interviews or whatever on what was going down, and you could have a 1 or 2 hour weekly TV show pretty cheaply, I mean realy the majority of you're costs would be editing (that is if you ommit the HUGE cost of the mission itself).
Unfortuantly even the most wildly succesful show wouldn't be able to cover the cost of a mission to mars. And lets face it, you're not going to be able to have a show popular enough to sustain excelent ratings for the 2 or 3 years that the mission would take.
I expect Catapults would suffer some of the same problems that rail-guns do. Namely that it would be VERY hard to design a payload that could survive the stress of being accelerate to escape velocity in such a short period of time.
Soph - um actualy what you're talking about is EXACTLY what is done. In modern pressurised water reactors (PWR), the fuel rods (where the nuclear reactorion actualy takes place) are moderated with water, which also takes in the heat produced. This heat is then used to turn a turbine just the same as in a fossil fuel plant. Not all this heat can be used in this manner, and it must be disposed of in some other means, usualy by a cooling tower, a nearby river, or even a cooling lake. Many fossil fuel plants require cooling facilities for the same reasons.
Here's a diagram of PWR to make it all clearer.
http://www.tva.gov/power/wbndiag.htm]click here
Unforchently Soph, the creation of anti-matter takes (at least) twice as much energy as can be found in the anti-matter created. This is due to conversion of baryons (protons and neutrons) and leptons (electrons).
Creation of anti-particles must go something like this.
energy -> particle + anti-particle
So you need to particles worth of energy. To create one instance of anti-particles. This is because the baryon or lepton number must remain constant. The baryon number is equal to the number of number of baryons (protons or neutrons) minus anti-baryons (anti-protons or anti-neutrons). Ditto for the leptons number (electrons-positrons). In either case, this number must stay constant, so for every anti-particle created a normal particle must also be created, so that the baryon (or lepton) number stays the same.
Now you can reverse this reaction (ie. particle + anti-particle -> energy), but obviously this results in 0 net energy, so you're not getting anywhere.
Of course this is all in an ideal situation. In reality we can't produce reactions that come any where close to the thoretical maxium efficency of the above equations. Currently the efficency of the creation of anti-matter is around .000004% with some potential to raising .02% in the near future.
And the reverse reaction (anti-matter annilation) is actualy not completely efficent either. Some of the energy is going to go into the creation of neutrino's which interact very weakly and will escape with some of the energy. Some of the muons and pions will have to much energy to be captured and will escape as well (they will later decay into gamma radiation, but to late to be of use to us). So this reaction is actualy not going to be totaly efficent either.
As for collecting anti-matter from space. Apparently anti-matter is quite rare in our corner of the universe. I don't think we've even detected any naturaly occuring out in space, there certianly isn't enough to power a space-ship. I've seen a few studies saying the same is true for harvesting matter from fusion in interplantitary space as well. Matter is more common inside the solar system, but in any case this would be a very slow method of travel. Solar sailing has much more potential.
??
As far as I know the existance of tachyons is still hypothetical. I haven't heard of any successfull detection of Cerenkov radiation or any other indicator of there existance. If you've got some reports on there discovery please forward them to me.
But you know, why you think about it, not finding evidence for there existance isn't supprising. I mean consider:
m = m0 / SQR(1 - v^2/c^2)
m = relativistic mass
m0 = rest mass
v = velocity
c = speed of light
So, if you're velocity is greater than c, v^2/c^2 is greater than one and becomes negative. Giving you an imaginary mass. Which of doesn't make a heck of a lot of sense. The example I gave below was just hypothetical, you could replacy tachyons with hyperdrive, quantum tunneling, warp driver, or whatever you want, the concept remains the same.
Well that's one possibility. However, do not forget that the vast, VAST majority of evidence is on special realitivites side. So more likely that the Grandfather paradox being an example of a fundamental misunderstanding of physics, is that events which can cause such a paradox (ie, FTL travel) are simply not possible. Rememeber we still lack clear and concreat evidence of FTL travel or communication, it's all mainly theoretical with very little (or very skimpy) proof to back it up.
All FTL methods of communicaton/travel can cause the grandfather paradox when the situation is right.
An exert describing how and why (find the whole thing http://sheol.org/throopw/tachyon-pistols.html]here)
"We can describe this effect by idealizing FTL to be "instantaneous", and describing how the more familar time dilation implies this effect. But remember, the same points apply to any FTL speed, you just have more messy arithmetic to grind through.
Consider a duel with tachyon pistols. Two duelists, A and B, are to stand back to back, then start out at 0.866 lightspeed for 8 seconds, turn, and fire. Tachyon pistol rounds move so fast, they are instantaneous for all practical purposes.
So, the duelists both set out --- at 0.866 lightspeed each relative to the other, so that the time dilation factor is 2 between them. Duelist A counts off 8 lightseconds, turns, and fires. Now, according to A (since in relativity all inertial frames are equally valid) B's the one who's moving, so B's clock is ticking at half-speed. Thus, the tachyon round hits B in the back as B's clock ticks 4 seconds.
Now B (according to relativity) has every right to consider A as moving, and thus, A is the one with the slowed clock. So, as B is hit in the back at tick 4, in outrage at A's firing before 8 seconds are up, B manages to turn and fire before being overcome by his fatal wound. And since in B's frame of reference it's A's clock that ticks slow, B's round hits A, striking A dead instantly, at A's second tick; a full six seconds before A fired the original round. A classic grandfather paradox.
Note, this is NOT a matter of when light gets to an observer, it is NOT an optical illusion. It is due to the fact that, in SR, the question of what occurs at the "same time as" something else is observer dependent.
As A fired that first show at tick 8, the bullet effectively teleported from A's gun to B's back instantly --- instantly according to A. But for B, who was moving at 0.866 lightspeed WRT A, B was hit in the back by the bullet 4 seconds BEFORE the bullet was fired. And again note, this is NOT due to the optical illusion of lightspeed delay in viewing A's turn-and-shoot; the light form that event wouldn't reach B until MUCH later, not tick 4."
As you can see the problems with causality and simultaneity at a distance don't specificly lie with the FTL travel, but the rest of the universe. Any FTL situation could cause a grandfather paradox similar to the one above.
Two theories have been proposed to get around this. First is the multiple universe theory. Unforchenetly, short of causing a grandfather paradox, this theory seems impossible to prove and some of it's consiquenses (such as there exists universes where no consicous observer has ever lost conciousness?) are hard to swallow.
The other theory, Novikov self-consistency principle, is little better. To me it amounts to little more than arm waving in saying that time-travel cannot effect future events, because it can't. And it sacrifices free will to boot.
But I try and perserve and open mind, and I'm eager to here why other means of FTL travel might be able to get around these problems.
Don't completely dismiss the Ukraine Radiological Institute results. There is some truth there. The rates of thyroid cancer in areas effected by the fallout have risen dramaticly. For example my girlfriend's mother who lives in Minsk, Belaruss as well as her best friend and about half the people in their Church have thyroid cancer. Thankfully, my GF's mother and her best friends cancer is not malignet. However, not all there friends at the church have been so lucky. To my knowlege one has died from the cancer, and several have had to have there thyroid's removed in response. I worry constantly about my Girlfriend, a native Belarussian, who lived in Minsk up untill 1999. She was only 4 at the time and should be at a much greater risk than her parents. I'll be the first to point out here that the plural of these ancedotes is not data. But to say the disaster didn't have a signifigant harmful effect on people's health and lives is not true. It's surely effected my life and I don't live anywhere near the Ukraine!
I still belive in nuclear power, as does my girlfriend, but it a tool we must treat with respect. And we shouldn't idly dissmiss dumping nearly 200 tons of radioactive material (like what happened at Chernoable) as no big deal! Thousands had to be rellocated and over a hundred lost there life directly due to the incident. It IS a big deal, and we should be carefull with these tools.
As anti-matter is offten brought up in respect to propulsion, I thought it would be benificial to discuss it here.
In order to deal with anti-matter you first have to get anti-matter. Fortunatly they're aren't any anti-matter mines lying around and the stuff must be made.
http://www.engr.psu.edu/antimatter/Pape … i.pdf]Here is a good website about it. but I'll summerise.
The energy necessary for the creation of anti-matter is bound by the laws of physics. The entire mass energy of the anti-matter must be provided, and unfortunetly, the manner in which this is done is usualy very inefficent. The cost can then be expressed like so:
cost=(kg*Ma*c^2)/n
Where kg is energy cost, Ma is mass of anti-matter, c is the speed of light and n is the efficency of the anti-matter production system. The theoretical max of n is 1/2 due to the conservation of baryons (for every anti-particle you create you must create a real particle counterpart).
As you can see cost is strongly dependent upon the efficency n. However, n tends to be incredibly small, right now around 4e-8 giving a cost of $62.5 trillion per gram of anti-proton (assuming energy costs of $0.1 kW-hr). This is much to high to be of pratical use today.
The people at CERN seem certian that they could improve this by 3 or 4 orders of magnitude. But even a n of 2e-4 gives a cost of $25 billion per gram. Which is about 1,000 times more expensive then an equivelent amount of energy in chemical propelents. Even at theoretical max of n=1/2 and a cost of only $5 million per gram, it only starts to approach chemical propulsion's cost. And of course, we can't even come close to this level. So large (kg>or more) amounts of anti-matter are out of the picture until energy costs become much less than there current prices.
But with the improvments projects requiring smaller amount of anti-matter (in the micro to nano range) become possible. I let you guys look over and discuss that part.
I've looked into possibilties of neutralisation, but they don't look promissing to me. Flourine, like other hallogens, is very soluable in most compounds. There are only a few exceptions, such as BaF2, MgF2, PbF2. All three of these have fairly low Ksp (solubility constant) as well. In any case, precipitating the flouride ions out is not going to work well. The precipitate will simply sink and slowly dissolve as well. Perhaps it might be possible to capture it in big nets, but this seems highly dubious to me. I'm a chemistry major, but admitdly do not everything. Even-so, I don't know of any other means of removing flourine from aquious solution. Even today, flourine is produced by electrolisis of HF acid. HF is created by disolving Fluorspar (CaF2) in Sulphuric Acid (H2SO4) btw.
The dilution you propose would not be effective. The reaction plays out like this:
2NaOH(aq) + F2(g) -> 2NaF(aq) + H2O + OF2(g)
the reaction with HF would have no appreciable reaction (both would disolve in water). Remember for most flourine compounds it's not the acidity H+ ion concentration, but the F- ions that are the toxicity problems. Neutralising the acidity of the solution doesn't help. Besides, flourine is SO electronegative that it will litteraly attack the water breakng the O-H bonds. HF is also a weak acid, (meaing it does not dissasociate fully), so the more you neutralise the more goes out into solution.
The big problem with pad explosions is not the explosion itself (although of course those will be very bad), but the toxic release. A partialy submerged ship would obviously only increase these difficulties. Again, the launch system must be designed with the idea that a on-pad (or near-pad) explosion will occur and be designed to accept this. This is doubly true since these failures are among the most common anyways.
Well, I'm just dubious about supplying these huge ships out in the middle of the Pacific, what with the storms and what not out there. I have no doubt that such a ship could be built. It even could be protected from HF, but a wimpy coat of teflon sure ain't going to do it! Teflon is a thermosetting plastic IIRC, and it will surely melt from all the heat it will be subjected to, leaving the undersurface bare and unprotected. Even diluting the HF or percipitating the HF away will still leave you with a ship undergoing accelerated decay. Anyways, I grant that such a ship could be built, but building more Saturn V's would probably end up being cheaper than a fleet of these things. Another problem occured to me, where are you going to test the engines? No way the EPA is going to let you use the NASA sight in Mississippi (or was it Albama? I'm not sure and the name eludes me). A new site will have to built someplace remote. This applies to other new exotic big engines as well, something that needs to be considered.
Now as I said before I'm a chemist, not a rocket scientists. But I was under the impression that if you want to do a launch more with a higher ISP but the same ammount of propelent you would have either lower thrust (unaccaptable at lift-off), or higher mass consumption rates. Maybe you could point out where I'm wrong here.
Using HF in upper stages seems acceptable to me, as the quantities are generaly an order of magnitude lower, and the pollution is at high-alltiudes anyways. Of course there may be some flourine reactions with the upper atmosphere, but I know nothing about this, and won't speculate.
I have no problem with most nuclear designs though. Ironicly, they are much more eco-friendly that flourine engines.
I understand your point mauk2, but here's why I still disagree.
#1. A 60 ppm toxicity is a VERY concervative figure. Although the data I have is for fresh water, I think it is safe to assume that nearly Everything exposed to that region of toxicity would die. It's certianly high enough to kill most of us humans. From fish to whales (low probability of them being at the launch site at the time, I know), and probably most of the plankton and other micro-organisims as well. Even when it has diluted down to 18 ppm (a cubic km away), it would still be very dangerous. You wouldn't want to drink such water, you'd get very sick. Sea life wouldn't be much diffrent. So seing effects out that far is highly likely. Concentrations as low as 2 ppm are supposed to cause fluorosis in humans, and I imagine bony fishes could suffer from this condition as well.
#2. You have to plan for a worse case scenario. A typical rocket launch would spread the flourine out over a wide area. Although higher impulse fuels like what we are talking about here would spend more of there fuel at lower alltitudes right higher specific impulse=(requires) a higher rate of mass discharge. But you must plan for a worse case-scenario, that is, the rocket blowing up on the pad, or something else like that.
#3. We're not just talking about one launch here, but many. The effects are multiplied over the length the booster is in use, which I hope will end up being much longer than the Saturn series of boosters.
#4. Launches are offten proposed to take place far out in the Pacific, where the sea-life densities are generaly lower and there is good isolation from inhabeted areas. But the logistics of such an opperation make me highly doubtfull. More-likely is a launch near a convient supply island, like some place in the Carribian or what not.
#5. Technical considerations. As I pointed out earlier, HF will eat at pretty much anything, from most base metals, to glass and even concreate! How are you going to design a launch ship to deal with this extream corusivness. In fact, the entire concept of a gigantic launch ship, floating out into the deep-blue sea, and then launching a enormous rocket (the vessle itself being unmanned I should hope), gets less and less belivable the more I think about it. I suppose it's technicaly possible, but building bigger conventional rockets on land is probably a better solution.
I have to disagree with mauk2 on this. Even for the smaller Saturn V rocket, the release of around 2 million kg of HF (or other flourine compounds, it's the disolved F- ions which do the dirty work, and they pretty much all disolve in water), could be expected to toxify 33 million cubic meters of the pacific (assuming 60ppm toxicity). And were talking total death in this region. The effects could easily be expected to be lethal as much as a cubic km from the sight. Given the nature of the ocean, however, this area would not be a true cubic km, but much more spread out. Maybe HF could be used in smaller amounts in the upper stages, but I think it is much to dangerous to use here on earth.
There's good reason why flourine is not used as an oxidiser. It's toxicity cannot be overstated. Flourine, be it in it's elemental form (F2) or bound up with a diffrent chemical (HF, NaF, LiF, ect...), is very, very toxic. Especialy in the huge quantities we are dealing with here. The same applies to the other halogens, to a lesser degree as you procided down the periodic table. Even realitivily tame NaF has an LD50 esstimated as low as 20mg/Kg if ingested.
The most likely product of an flourine oxidies rocket, HF (Hydroflouric Acid), is much worse. It's a weak Acid with a pH around 1.6. It's toxicity is much worse, LD50 being around 1,300 ppm for inhalation. Worse, HF acid will easily penetrate skin and attack the tissue underneath. It's also deadly to aquatic life in concentrations around 60ppm, and it's probably not good for plant life as well. Even realitivly low doses of HF (or realy any flourine compound), can result in flourosis, a condition which results in various skeletal and dental problems.
I read a case study about someone who had a realitivily mild HF burn. In this case, the person recived a small splash (maybe 5cm^2) of a low (20% HF) solution. There never was any damage to the exterior tissue, however the HF had traveled right though his skin and attacked the underling tissues underneath. Treatment was very difficult, and only quick thinking and action by the doctor prevented the man from losing his hand, and possibly his life.
Not to mention the fact that HF will attack many metals and glass. Aliens wasn't a complete lie, just an exageration. HF acid realy does errode away at glass and other materials like no other acid (except maybe aqua regent, but I disgress).
Imagine a HLV in the Saturn V class, it's lift off would spew some 2 million kg of various toxic flouride products into the atmosphere and land around it's launch site. Of course for the bigger launch vehicles the problem gets even worse. The HF would probably do damage to the launch stand (maybe even the rocket itself), even if protected, as I imagine the violace of the launch would probably errode some of this. And the entire surrounding area would be innudated with HF. It would be danagerous to approach the launch site for quite some time, and I expect much (if not all) of the plant life would die. At a sight like cape-canavral the ocean would be polluted as well. And a sea launch would be horrible resulting in massive fish-kill.
No, we don't use flourine as an oxidant for good reason. It's just to dangerous to play around with. Even during loading, cryogenic oxygen or hydrogen is (in comparison), much, much safer than flourine. Maybe if the launch pad was in the desert it might be an option, but even then I doubt it. The risks and the pollution is just to great. We'd be better off using something like orion and nuclear bombs.
Check out the MSDS (Material Safety Data Sheet) for HF here:
http://specchem-apps.alliedsignal.com/p … S/hfan.pdf
I think if the we decide that terroforming is justified, waiting would not be necessary before hand. I mean even useing the biggest baddest methods possible to change the planet it would still be probably 20-30 years before there was any appreciable change. Constructing giant mirrors, diverting asteriods, whatever, is going to take a long time.
Also, in the long run, I bet most Martian gas and water loss could easily be made-up for by the continual divertion of various commets, moonlets, tiny planets, whatever to the system.
According to the laws of physics as we know them now, faster than light travel is not possible. A warp drive, as often proposed, would require generating a huge amount of negative energy. Which is difficult because negative energy probably does not exists (if not theoreticly forbidden outright).
Anyways, a good a sight about this can be found here in the realativity FAQ. Check out the section of the "Grandfather Paradox," I found it particulary helpfull in explaining this issue to me (that is, why FTL travel can create this paradox).
There's other cool things you can do with that low-level radioactive waste, like mixing it into concreat or asphalt. It a way to dispose of it, and it could help the keep the roads from iceing, and could help the concreat to cure in cold climates or big pours.
In fact, now that I think about it, using radioactive waste to heat the concreat may help to solve some of the problems of pouring concreat on Mars (where it's realy cold).