New Mars Forums

Don't know if Tom's still reading this at all but the reason why succession would never happen today is that the conservative "majority" in southern states is actually quite small.  They only have a 10% advantage or so at most.  This is quite different then the ACW where the percentage supporting succession was much higher.  If presidential electoral votes were allocated proportional to the votes in the votes in the states (instead of the winner take all system we have now) this would be much more obvious.

I'm not sure what you mean here.  D-D fusion about twice as hard as He3-D, but both are about an order of magnitude more dificult than simple D-T.  This is determined by their Lawson Critera.  Which is the product of a reactions optimal plasma density, temperature, and rate at which energy is lost (or confinement time).  He3 is not intrinsicly easier to contain then anyother sort of fusion fuel.  It has a better Lawson Critera primarily because it has no (or at least very few) neutron to lose heat with.  And so it's optimal conditions are a bit better than D-D fusion (and signifigantly better than p-B11) but again, considerably worse than D-T.  If "ease of containment" is the deciding issue, then D-T wins hands down.

Any reactor is going to have to be shut down from time to time for maintance, this is just simply the way life works.  That is why nuclear fission reactors are always built in twos or threes (or more).  The same will be true for fusion reactors.  Heck, it's true for pratical any large scale power-plant.

I am far from convinced that the irradiation is going to be a big enough factor to offset the many order of magnitude increased cost of He3 fuel.  Fuel for D-D (and to a lesser extent fission and D-T) is so low as to barely even enter into the costs.  But that is because even Uranium is less than $100/kg.  We would be lucky to get He3 for 1,000 as much.  So at $100,000/kg and 10MW/kg, that's $10/kW for fuel alone.   Coal produces ~10kW/kg and cost $50/MT so ~$200/kW.  Plug in whatever you assume for He3 costs for your own comparision, but I can't imagine it being competative.

With proper selection of reactor materials neutron radiation is not that signifigant a problem.  Neutron activation isn't going to cause a fusion reactor to crumble over night.  Indeed, I would be much more worried about potential material fatigue from exposure to Such high temperature plasma then neutron flux.  The biggest problem is that exposed materials have to be disposed of as low-level nuclear waste, but in the end this not that great a cost, at least not compared to He3 costs.

But if we are going to consider D-He3 fusion, we should not compare it simply with D-T fusion, but with D-D fusion which is achiveable at about the same temperatures.  D-D fusion produces considerably less neutron radiation than D-T and has a better power/weight ratio (almost as good as that as D-He3) and uses no expensive fusion fuels (indeed, you could potentialy collect He3 from the reactor if you wished).

Furthermore, D-He3 is not completely aneutronic either.  Some D-D reactions will occur, producing some Neutron radiation.  He3-He3 fusion would be completly aneutronic but you're fuel requirments would double, and you lose the specific power advantage.  It also requires an even higher temperature.  If you were to consider it, you might as well consider something like p-B11 which is also completely aneutronic.  While it's ignintion temperature and containment requirments are higher then D-D or D-He3, the gap is not as big as that bettwen D-T and D-D fusion.

No, I'm talking real economic growth here, already adjusted for inflation.  Basicaly in 50 years we can expect there to be 4 times as much 'wealth' around in the US.  So if we continue to spend about the same percentage of our 'wealth' on space operations, we will get 4x as much bang for our buck so to speak.

Put another way, we can expect the realtive price of space travel to drop as our society becomes more wealthy.  Sort of like how two or more car households are common in the US now, not just because Cars have become cheaper to make (although they have) but because there is more 'wealth' out there in the world for people to spend on Cars.  Similar examples could be drawn with computers or telephones, or pretty much any good/service you care to name.  We have more of practicaly everything now then we did in the past because our society has grown more wealthy.

For example, the value of the US dollar has inflated a dramatic amount since the begining of the century, however our society is obviously vastly richer.  One hours worth of work today purchases much more valuable goods then an hours worth of work in 1907.  Obviously those goods are better in quality and the like, but put another way, a person has to work much fewer hours today to meet the necesseties of life than a person in 1907 did.  Or for that matter a person in Africa (a much less wealth society) does today.

The same things will apply to rockets.  They will probably cost approximently the same amount (in 2007 relative dollars) in 2057 as they do today (assuming no new advancments in space travel).  But we will have much more money to spend on them.  Their cost, as a percentage of the total US economy (or goverment budget), will be much less.  For example, the Apollo program cost ~135 billion (in 2006 dollars) spread out over 10 years, so say 14 billion a year.  NASA's 2008 budge is some 16 billion this year, considerably larger, despite the fact that NASA gets a much smaller percentage chunk of the Federal budget now.  Simply because our society is so much more wealthy now than then.

Hoppers are a great method for adding planetary scale mobility to a Mars Mission, but they are fairly massive and not as reliable as a rover.  Idealy you want to have two hoppers ready for deployment at any one time in case one brakes down.  Their fuel consumption is also considerable.  They are a great idea for a established based, but not a Rover replacment IMO.

They should, it adds another back-up in case you aren't able to redveous with the orbital module for some reason, you can still escape back to the martian surface.

I tend to think of NASA's DRM III as an improvment to Mars Direct.  You really can't upgrade mars direct without losing critical elements of it's design philosophy (ie get to mars cheap and fast).

The DRM incoporates almost all of the important engineering details from Mars Direct (conjunction class missions, some ISRU) the only major diffrence is the use of Mars Orbital Redevous (like Apollo) as opposed to Mars Surface Rendevous (which was considered but discarded by the Apollo program).

No scramjet has reached the development point where it could be deployed in a vehcile the size of the one we are talking about.  We are still quite some time away from a scramjet that could be used in a missle, much less a something of this size.  As for ramjets, the SR-71's Pratt & Whitney J58 are very much like the sort of engine we would like to use, but a more modern version would probably be signifigantly more powerful and fuel efficent.

As for a comparision of power, air-breathing engines in general are about an order of magnitude less powerful than rocket engines like the SSME.  We talking like ~1500kN for the SSME and ~150kN for the most powerful turbojets.  But thats okay, since unlike the SSME the turbojets do not have to push their payload straight up against earths gravity (they can use lift for assistance), and since they don't have to carry there (heavy) oxidiser, they are much more fuel efficent (ISP ~2000) so you can afford to take longer.

I disagree with the praticality of kinetic energy weapons.  Firstly as you state to achive continuious coverage you can't have just one or two of these weapons in orbits, but whole constellations of them.  Otherwise they won't be instantly avaliable and their practical value is lost.

Secoundly, the destructive power of KEM is often vastly overstated, it is very hard for reasonbly sized renetry vehicles to retain all of their velocity in the lower atmosphere.  In the end most studies I have read result in KEM with explosive values on marginaly greater then TNT.  It is true that their penetration characteristics would be remarkable, but our targets could alway dig deeper.  2m of steel or 10m or so of granite would stop just about any weapon.  Also similar effects could be achived by rocket boosting conventional weapons.

Lastly, pin-point accuracy with KEM is going to be VERY hard to achive.  Your talking about a hypersonic vehicle which had only a couple of secounds (at best) to narrow in on its target.  Meanwhile it skin is ablaiting away from the intense heat of re-entery.  Controling such a munition during it's terminal phase will be very difficult, and I don't see how any sort of detection mechanisim could last exposed to renetry.  It's like trying to mount a camera on the underskin of the shuttle during re-entery, only harder.

I mostly agree with these points, but this is exactly why degrading our conventional forces makes the threat more credible.  I don't think Iran or N. Korea have any doubt that the US would respond to an attack.  The question to them is how.  If we reduce our forces to the point where nuclear retaliation is our most attractive option, then they will be more detered by it.

For example if N. Korea or Iran was some how to launch a nuke at the US or a US friendly target (Isreal or S. Korea) the US very well might not respond with nuclear weapons.  Nuclear weapons have grown to be a weapon of last resort, and since we could defeat these nations without using them, we would be pressured into doing so.

Also if the leader of the nation in question is insane, then really the US's weapon arsenell has little effect on their behavior either way.  More or less conventional or nuclear weapons aren't going to change things.  So I feel we can only make rational plans for dealing with rational leaders.  Irational leaders are going to do their own thing regardless.

I think the ABM system we have/are developing is a waste of money for this very reason.  Iran or N. Korea are only going to have an extreamly limited number of weapons and some unreliable (at best) ICBM delivery systems.  That they many not even be able to load their weapons onto (they may be to heavy).  In this case delivering them via some-other means (freighter, sub, whatever) makes a lot more sense, and our ABM system is a waste of money.  This is why a credible doctrine of MAD is much more valuable.  A ABM only protects against ballistic missles (and has not done a very good job at that), but a credible MAD policy protects against virtualy all potential strikes.

Outside of Canada, Mexico, Australia, and South America all of our allies are reachable by Plane or IRBM (or even shorter range missles) so tactical ABM systems like the Patriot and Ageis are our only defense against these sorts of attacks.  It is very difficult for space based systems to intercept these sorts of attacks, which don't get and stay high enough for them to be effective.

I think you are very wrong here.  We've focused on mid-course/terminal phase interception of ICBMs because it is the simplest way to defeate these weapons.  Hitting them in any-other phase is VERY difficult.  Their realy is no simple and cheap solution to this.  Large constilations of KE interceptors or constilations of laser or other weapon platforms would be both difficult and expensive to design.  And they still don't ensure the safey of our space assets, which are still vunerable to the likes of ground based lasers.  I still belive the best way to combat this threat is with a credible MAD policy to deter them.  Face it, if an enemy is going to launch some sort of WMD at the US in the end all the defensive systems in the world are probably not going to prevent them from getting one in someway.

Tough situation.  But I don't imagine the Europe or even Russia is going to be that hard nosed with the US over such matters.  OTOH like I said before a ASAT weapon is dead simple.  Just launch a "satilite" to intersect with the other satilites orbital path.  With a good ground track (which we have on most satilites) this is easy.  I still think the situation in which you have to use on is rather implausable.

I disagre Martin, the biggest problem with this sort of weapon system is that it would never be used.  The current state of affairs in the word ensures this.  The US (or any other nation) cannot attempt to deny space to it's enemies without the risk of retaliation and further escelation.  So it's a weapon without a point.  The same is true of almost any confrontation bettwen major powers today.

Introducing a new point, even if we did have such a conflict such a system would be of little value.  The Chinese (for example) have little in the way of space assets to destroy or deny.  A few spy, early warning, and communication satilites maybe.  Nothing that is going to change the outcome of any conflict.  In fact the US is far more vunerable to this sort of warfare than any other nation, as we are much more dependant on our satilites.

While I am normly all for any kind of space funding, I think this is complete bunk.  Arm space?  How?  And why?  Eactly what sort of threat are we supposed to be combating in orbit?  Right now their are basicaly 4 major space powers.

NASA, ESA, Russia, and China.

Russia and ESA are currently our friends and allies.  And China is not exatly a beligernt either.  North Korea, Iran, and Liba (the axis of evil) do not have a space program.  The Chinese are still far, far, behind us even if things did turn ugly.  All of us are nuclear armed anyways, so avoding a conflict is much more in our intrest anyways.  If things did turn ugly, the state of our (or their) space assets would be the least of our troubles.

Anyways, practical space combat would be pretty boring, nothing like Star Wars anyways. The only practical space weapon I could see us developing is a anti-satilite satilite.  Basicaly put some manuverable vehicles in a Titan or Delta and launch them.  Viola, you're done.  US Space Command already has (and maintains) a track on most signifigant objects in orbit anyways.

Anything else is stupid waste of resources.  After all, space is empty, it's only the devices in it that have any value.

Thats kind of like saying that the first step in discovering Santa Clause is finding his secret underground toy workshop.  The "mechanosythisis", that Drexler talks about is simply not possible, chemicaly.  In a way, the introductory chemistry courses that he has taken have probably done him a diservice.  VSEPR and other things which are taught on that level are, as my chemistry professor once put it, "a carefully constructed pack of lies."  They are true enough on average, but they greatly simplfy and hide how chemical reactions actualy take place.

Now I'm all for using biotechnology as a means of manufacturing chemicals, but their are limits to what biology can accomplish.  You can't refine Titanium or make steel with bacteria for example.  And the methods they use are WHOLY diffrent then the mechanosynthisis Drexler describes.  Could a bacteria be designed to produce buckytubes?  I woudln't completely rule it out, but I have my doubts.  Bacteria don't (or can't) manufacture grafite, which are buckytubes close analog.  I can't imagine what sort of chemical proccess they might use to do so, but I wouldn't completely rule it out.

I think GCRN put this best in a post of his a while back.  Not all ideas are created equal, and it is silly to treat them as such.  Without logical backing or evidence, an idea has little merit.  Simply wishing for it won't make it so.  And just because I am opposed to some ideas (those lacking technical merit), does not mean I am opposed to all ideas.  Indeed, there are a great many ideas I enthusiasticly support, mechanosythisis style nanotechnology is simply not one of them.

As for space elevators, I would defiently call myself a supporter, but a rational one.  The jury is still out on their feasiblity.  Buckytubes may or may not have the strength we need (this is much the same thing that GCRN said).  However, I would point out, that even if their strength is lower than we would like, their is still the possibility of other materials with greater strength, or simply making a cable much larger to support it's own weight.  You could actualy make such a cable out of simple steel, but it's size/taper ratio would be impratical.

On the moon and Mars I think you will find I and pretty much everyone else here in agreement that they are not only practial, but a great idea.

Clark, I'm going to respond to you're first post as I think it captures you're feelings more succiently.

This is more on the right track as to what the goverment could both affordably offer and would be more likely to attract investment.  However, you have to balance these options with what the goverment can actually praticaly offer.  A great number of these options are either praticaly impossible.  For example no one goverment could grant a monoply on space travel or lifetime patents (that would be unconstitutional in the US anyways).

But you are right that these sorts of non-monetary incentives are more likely to get a coporation to invest in space.  A similar system was used in getting the US transcontiental railroad built.  The goverment could pledge to support bond companies issued to finace space exploration.  Tax breaks and the like could also be offered.

The problem with all this though is that it assumes that space travel will become profitable in the short term, which is unlikely.  It makes little sense for the goverment to offer such guarntees towards a prizes that it itself puts up.  It might as well finace the thing directly.

I think the key to bringing the cost of space travel down is to make the bidding proccess more competative, and hold the companies more closely to those contracts.