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Austin Staley, The civil war was all about states rights against the federal government rights. Slavery was used by the Union as cover.
Of course states right played a role in the civil war, but slavery was one the key reasons why the states were worried about those rights. They feared that the North would use the majority they had just achived in the federal goverment to abolish slavery. The civil war was also a reaction to the tariffs the North had imposed on certian goods, which harshly effected the South (who's economy was based mainly on exports). There were a number of reasons the Civil War was fought, but slavery and the disequality bettwen the North and South were definetly among them.
Also calling capitalism to be a modern day form of slavery is an old trick of the socialist. Slavery is where a person is owned as property by an other human. The master makes the slave do work for him in extange for food and shelter. The big thing is that the slave is owned by the master and has no choice but to do what he is told. No freedom of choice, or movement, and being property is what defines a slave.
Don't put words in my mouth. I never said this, and I don't belive it. My argument is that an unhealthy disparity in the wealth of the rich and poor is a bad thing and can eventualy lead to a leftist revolution. I think such a revolution would be a bad thing, so we should strive to avoid it.
Now under capitalism people are free to make choices, they work for money, are not property, and have freedom of movement. A person working for low wages in a bad job, has the freedom to find a better job. If he was a slave he could not do what he wanted to do. If you dont like your job find another, not educated then go to shcool, get the skills and get a better job. In America no one is a slave, you are free to do what ever you want. That what is so great about America, so stop hating America because you cant make it, and stop thinking of your self as a slave.
Let me set the record straight, I am not a communist/socialists. I firmly belive in Capatilisim and Democracy. Furthermore, capatilisim has been fairly good to me. I recently recieved a $50,000 windfall because a large coporation purchased an chemical milling system improvment that I had a hand in developing. I am pretty secure in my place in the middle class. However, I have also been abroad, particularly to parts of Latin America and have seen the results of a capatilist system that gets out of control. I do not want to have to live in an armed complex or higher a bodyguard because of fear of the poor, which is a fact of life in those areas. This is what leads to my worries about America.
That said, I do take some issues with some of your points in your last paragraph. We are very free here in America, but that does not mean everyone is free to make ANY economic decision they would like to. Not everyone is intellegent enough to go to college. Some idiots are born into vast quanitites of wealth (Paris Hilton). I would never be a good mechanic, and my mechanic would probably never be a good lawyer. Such is life, we are not all equal in our apptitudes and abilities, and so the station is life we end up with is not equal.
Nor is the economic system completely fair. As long as capital has existed there have been people who try and abuse the rules to there profit and everone elses detriment. Trusts, monopolies, price fixing, labor laws, ect.. have all been used in the past and present by the wealthy to secure their wealth and get even more of it. The also use their capital to buy the lawmakers and use the goverment to help secure their position. This is another battle we constatly face to ensure that capitilisim truely is fair.
You don't need to hit a 'significant chunk'. At interplanetary speeds, a grain of sand less than a millimeter across will puncture a gasbag. You're *not* going to get a gasbag from planet to planet without it hitting any cosmic dust on the way.
Even encounters with millimeter scale particles are extreamly infrequent in space. Especialy interplanetary space. There is simply an extreamly large amount of space and a small amount of matter to fill it. You're just not likely to encounter any signifigant particles of any size. "Cosmic dust" is non existant, unless you are referring to the stray particles the sun spews out. This "dust" is realy just a sprinkling of stray nuclei, and hardly worth worring about.
A self-sealing gasbag is an interesting idea; can you point me to any developments giving us hope that such a technology is possible? Of course, it would need to self-repair almost instantaneously, because any puncture would powerfully blast the air out of the small hole, very rapidly ripping the hole open wider and wider with the force of the escaping air.
The simplest concept I could come up is to simply suspend a great deal of water-vapor inside the bag. In the envent of a puncture, the water vapor will turn to ice at the sight of the breach, plugging the whole. More conventional typical sealing polymers could be use.
However, the rip would NOT have to be plugged instantly. Any well designed gasbag is going to have a cohesive strength far larger than the bursting pressure within it. In other words, if would be made out of some sort of rip-stop material. So the bag would not "burst" if punctured.
I'd be interested in any figures and numbers on how fast sublimation would occur. I was wondering about the rate myself, and we can't really determine the feasibility of this method without crunching the numbers.
Hmm... I'll have to look up the statistics for nitrogen at these conditions. After I get the figure for the amount of energy necessary for the phase change, it's pretty simple to calculate. Suns radiated energy vrs. surface area.
RIZ4ROCKET, I have to admit I am having a hard time grasping your point. Let me restate what I think, and where I think we are in disagrement.
My gripe with America is the current increase in standard of living/amount of wealth bettwen the rich and the poor in America. Which is already large, and currently increasing.
I think this is a bad thing, firstly because it is mildly unjust. While some inequality is necessary for a properly functioning capatilist system, the amount we have is much greater than what is necessary. It provides an indentive to perform and achive. However, this does not mean that all levels of disparity are just. The currently wealth seperation in America is reaching the point where it is unjust. Some individuales to have so much wealth (for example Bill Gates) while some other individuales have next to nothing. Bill Gates has more money than he could every concievably use in his lifetime. A wise man once said, "You can only eat so good." This is especialy unfar because that wealth could be more equitably distributed without a meaningfull effect on Bill Gates (or any of the other super-wealthy). He could literaly have several orders of magnitude less money and still be just an motivated to perform and achive.
While the unjustness is enough reason for this to be a bad thing, there are other reasons as well. Such a unequal distribution of wealth also leads to an unequal distribution of power, especialy political power. For a democracy, especialy a representative democracy, to perform well power must be as equaly distributed as possible.
Unequal distribution of wealth also means that money is spent less effectivly than might otherwise be possible. Regan and his "vodoo" economics are just wrong headed. Increasing the amount of money the wealthy has can allow them to increase their holdings and with it increase the supply of good and services, which can in turn increase the number of people employed and the rate at which they are employed and increase demand. But even an elementry student of economics can see how this is wrong. Demand drives an economy, not supply. Increasing the amount of money the general public has increase the amount they can consume, which drives up supply (and thus back to demand) much more effectivly.
A greater seperation in wealth can also be linked to the larger amount of violence in 3rd world countries. I've been to parts of Latin America, and I know first hand how this can be the case. The wealthy (superwealthy compared to there peers) must live in armed complexes and travel with guards, because the danger from the poor is so great. But there focus on security has not made them any more safe. Only by increasing the pors standard of living can they remove the incentives which makes crime such an attractive option to them. This demands solving the wealth inequities present.
This leads directly to my final point, the ultimate outcome of an increasing seperation of wealth will eventualy lead to a leftist revolution. There are countless examples in history, and it is happening right now in Africa (Zimbabwe and even South Africa) and Latin America (Venezuela). These revolutions are not necessarily violent. But they DO generaly lead to the masses taking from the rich by non-economic means (legislation, capitulation, or force). These revolutions, even the most non-violent ones, I think we can agree are thing we would wish to avoid.
In the end, wealth must be distributed fairly bettwen the rich and poor for the safety of the rich and their wealth.
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Your first counter point seems to be that the US had Slavery (obviously an inequality in wealth) for a very long time, and did not lead to revolution. Firstly this is wrong on its very face. There were numerous slave revolts in US history and the civil war was fought over this very issue. Second, slavery was is some ways a less widespread distribution of wealth than we see in someparts of the world today. Slaves were a minority population, and in those times the desparity bettwen the wealthiest people and the slaves was not as great as it was today. Even so, one could argue that the general desparity bettwen the wealth of the rich North and poor South was one of the causes of the Civil War.
The second counter point I seem to be able to draw is that modern standerds of living are high enough so that the poor have no reason to revolt. I would first point out that this has not stopped modern revolutions in other parts of the world, despite the fact that the stanards of living are much higher now then they were in the more classical revolutionary periods. It is the relative diffrence that is most important, not the diffrence from some arbitary "comfortable stadard of living."
The last counter point I see is that modern techniques can easily put down revolts. Again, this has not proven to be the case in other parts of the world today, nor has it been in any time in the past. Sometimes a revolution succedes, sometimes it does not, but the amount one side is armed does not seem to play a part. In the end, people and there motivations, not weapons, are the driving power in any revolt. Not only manpower, but a popular revolt can drive a democratic upset, or lead a military faction to stage a coup. Society is in the end made up of people, it is only natural for those people to make the decisions as to what sort of society they want.
I've frequented these boards for a number of years now, and it never fails to strike me as curious as to the number of frankly crazy people we seem to attract. Most common seem to be people suffering with various degrees of what appears to be paranoid schizophrenia. The most obvious is Rick Dobson (International Space Agency guy) but there have been a number of others (some of which still sometimes frequent this board so I won't mention them by name).
While on some level it is intresting and faintly amusing to see these people, I often worry about them, and how they manage to function in society. I'm curious as to what everyone thinks attracts these people, and what, if anything we can do to help them/prevent it.
Sorry for the double post, but I decided to take a look at the requirments for a Titan space suit. Heat transfer through a plane is governed by this equation:
Q*A=(k*dT)/L which is just a re-worked modle of the one in my earlier post.
The human body has a surface area of <2m^2, so we will use that as an pesimistic estimate of the amount of area we have to deal with. Again, dT is ~200K. Aerogell would also work well for suits, but we might want something a little sturdier, so we will go with a high density plastic. Most of which have k values of ~.5w/(m*K). I figure about 2cm of insulation is the best one could hope for, without the suit becoming to terrible bulky, so we will go with that. This means that heat is lost at a rate of ~10kW.
This may not be so bad. Methane has about ~50MJ/kg of energy so, you would have to burn only .2g of methane a second to get this much heat. And .8g of oxygen a second to combust it with. I'm going to go to bed now, so I'll leave it to you guys to figure out what volume of gas this would require on Titan, to get that much methane.
Ok, I dug out some of my old physics books and did some calculations. The formula for thermal conductivity is:
k=(QxL)/(A*dT) or Q=(A*dT*k)/L
k is thermal conductivity (in W/m*K)
Q is rate of heat transfer
L is thickness
A is area
dT is change in temperature
Silica Aerogell has a very low thermal conductivity, and is so is a good insulator. It is also very light and very strong, and so would be perfect for insulation in a Titan outpost. It has a K value of .017 W/m*K, at room temp, but that value only gets higher as the temperature goes down.
Lets consider then how much heat would be lost at a largeish Titan outpost. A half-sphere 50m in diameter, with .1m of Silica aerogell insulation. It has a total radiating surface area of ~6000m^2 and the temperature diffrence is ~200K.
This means our outpost would lose some thermal energy at a rate of ~200kW. This would be alot if it was eletrical energy, but it is thermal. Any reactor of large enough size to power an outpost of this size, would produce MUCH more than this amount of heat, with most kWe class reactors having megawatts of wasate heat to get rid of.
Thats true. 1.5 atmospheres is bound to be equivilent to a safe diving depth. And reducing that shouldn't be all that difficult, if we need to at all. The pressure could gradually be stepped up in the transit craft.
1.5atm isn't an issue at all. People can live indefinetly at those pressures, without any exotic gas mixtures or ill-effects. It coresponds to an ocean depth of about ~5 meters, which is nothing.
The real trick with the heat issue I think is trying to heat the astronaut without unnaturally heating the ground they walk on. Sort of defeats the purpose.
Insulated boots will be necessary. However, since a phase change is necessary to turn the solid surface (which is presumably mostly water) into anything else, the effect will be considerably less than you might anticipate, since the energy necessary for a phase change is considerably greater than that necessary to simply heat the water/ice.
Figuring out how to keep an astronaut crew in an environment as cold as a liquid oxygen tank is a daunting task and the technology needed is largely undeveloped, so I doubt a serious effort to design a Titan mission can be expected soon.
I wouldn't worry to much about this. Modern insulation is quite good at trapping heat, and the amount of energy needed to actively heat a habitat is quite small in comparision to other space energy uses (electrolisis, gas seperation, liquifing gasses). Dewars easily hold liquid nitrogen (slightly colder then Titan's atmosphere) in a liquid state for weeks on end with only minor heat losses. Building a larger scale version for an outpost would be more difficult, but even a small nuclear reactor would supply more than enough waste heat to warm the habitat several times over.
I did some calcuations earlier (sorry I can't find the link) and they showed that even in the face of a major leak (inflowing air at like 1L/s) the energy needs to heat it to room temperature were trival.
Your right, sorry for going off topic.
Actually I'd have to disagree with you their. Maybe the inital CAV launcher, which would basically be a cheap mass produced ICBM first stage anyways would be detectable by IR satilites, but since it's a hypersonic gliding target rather then a ballistic target it really isn't in the same ballpark as a MIRV. Especially if incorperate some basic low level stealthing features.
Now once we have the reusable hypersonic launcher, which would presumably be at least partially air breathing, then all bets are off as far as thermal bloom detection.
Well the terminal phase will always be easily detectable, but at that point it is general to late to do anything.
However, I do not think an air-breathing scramjet launcher realy changes anything during the boost phase. An air-breathing launcher still has to expend just as much energy to get into orbit as a convetional one does. Just it collects most of it's oxidier from the atmosphere on the way up. It's engines have to be just as large and put out just as much heat as conventional engines do. In fact, they are probably even more detectable then conventional ICBMs, since the air-breathing launchers larger payload demands more energy to be expended during the assent phase. So if anything it will be MORE detectable via thermal ploom then an ICBM.
I'm not sure to what extent the Russians/Chinese rely upon ground based radars for early warning, but without some tricky to implement stealth technology, these will still be effective as well.
I'm more intrested in "Realpolitik," and I think some disengagment from the Middle East, and Israel especialy is necessary. I agree that there is some chance that if Iran was to gain access to Nuclear weapons, that they would use them against Israel. But more likely they would hold them in reserve, against possible Israel nuclear attack. Looking at it from Irans position, they have no real reason to believe that the Israels won't use nuclear weapons upon them at some point in the future, unless the develope a credible counterthreat. We may see this point of view as absurde, but the Iranians (for some admitidly good reasons) probably belive this very strongly, and it is highly unlikely that we can convince them that this is otherwise.
But what does all this mean to the US? What should our position be? I think we should disenage and let other parties sort the mess out. If Iran and Israel want to trade nukes or go to war again against each other, I say let them. Israel has not been the best ally to the US (they carrier out lots of spying against us), despite the incredibly massive amount of support the US gives them in return. And our support for Israel does nothing but antagonise the other middle eastern nations.
Put another way, some 60 years ago Israel took over a section of the Middle East and made it their homeland. A large portion of the people in that part of the world are very unhappy about this. Who is right and wrong in this situation is now irrelevent, Israel must find a way to come to terms with these people. Be it by further fortification and warfare, or by other more peacefull means. Whatever it may be, I think experince has shown that the US's intervention has not been productive in solving this problem, and has only aggrevated our problems with the other people of the Middle East. It's time to admit defeat, and let the intrested parties find there own ways of sorting it out.
This may not be very humane, but it is Realpolitik. The US's intrest are truly not supported by supporting either party, since it can only come at the price of angering the other. So we should take a more neutral stance towards both groups, and let them settle their own problems.
My problem with America is the way we are currently re-distributing our wealth. I'm pretty strongly capatilist, and I know that inequalities in wealth are necessary for our system to work. But this doesn't mean that a huge (and widening) gap bettwen the rich and poor is a healthy thing. Some balance is needed.
In America that balance is fast disapearing. Average wages are rising, but median wages are falling. The rich are getting alot richer, and the gulf bettwen them and the rest of us is widening. It's the goverments job at times like these to step in and take action to halt and reverse this gap. But currently we have a goverment that is more responsive to the needs of the rich and large coporations then ever before.
This cannot continue indefinetly. Eventualy the lowerclass will get fed-up and we will have a leftist revoltion, which I think would be a bad thing. Think I'm crazy? The same kind of reaction is classic in any society with such a wealth distribution, the French Revolution or the revolutions happening in Latin America. I just hope we get a handle on it before it gets to late.
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I also worry about our goverment becoming more authoriatian, and the executive branch overeaching it's power. But thats another rant for another day.
Lets forget for a sec weather a hypersonic bomber is needed today. Consider what happens if another nation gets one first. Can an aircraft carrier possibly defend against a hypersonic bomber? Another thought is for city attacks, what happens if the fleches approaches a city at a nearly horizontal angle. How many buildings can one fleche go though?
This is a pretty good point. It would be pretty difficult to impossible for a Carrier to defend against an orbital attack. And a single KE munition could do a lot of damage to such a Carrier. However, hitting any mobile target, even one as big as a Carrier would be quite a trick. Even if it was just crusing around at a moderate pace, the thing could be tens of kilometers (if not farther) from where it was when you launched your mission. You would have to find it again, and then direct your incoming hyper-sonic warhead to hit the now rapidly evading target. It would be very difficult.
As for KE weapons versus cities, they are rather useless. If you just want to carpet bomb indiscrimanetly. A cruise missle loaded with bomblets, or a conventional strategic bomber could achive more destruction. But in fact, a B2 loaded with JDAMs could achive more destruction, and dole it out with devestating precision. Of course, with the political consiquences with an indescrimante bombing campaign, you might as well just nuke the city.
KE fragmination weapons might have some use against armor formations, but again cruise missles or fighters/bombers loaded with bombets can do the same thing. And will probably be more effective as the bomblets from them can actively home in on their targets, while the KE would be more like a scatter shot.
Which makes the Hypersonic bomber a quick attack vehicle with no noticeable build up of force indicating the chance for attack and unless you have advance mission detection systems that means you will not know that it is coming.....
It's as detectable as an ICBM or any other orbital launch, IE the Chinese or Russians would see it coming. If you want to catch one of the major powers of guard, a cruise missle or B2 strike has a better chance. Now the Iranians wouldn't see it coming, but they wouldn't see a B2 or Cruise Missle strike either, at least not untill it was to late.
Sorry for the double post.
ICBMs:
-Aren't reuseable and expensive
They may be expensive, but the development costs are already paid for. We only have to pay the per-unit cost. And the Billions that developing an orbital space bomber would cost buys you alot of Minutemen. They are only $7Mill a pop.
-Have light payloads (esp. volume)
And just what sort of payload is the orbital space bomber going to carry? Using current tech it's going to have a hard time carrying a hell of a lot of anything.
-Not very accurate (best is +/- 100m)
Whatever re-entery vehicle that is going to give you pin-point accuracy at mach-12+ could be mounted on the ICBM as well. If indeed you can produce such a vehicle.
-Not well suited to kinetic weapons (impact angle)
?? an ICBM can generaly put it's payload into any of the same orbits a space bomber would use. Their impact angles (for it's worth) could be exactly the same.
-Can't loiter or be recalled
If you actualy have intellegence that HAS to be acted upon within a matter of hours, then you don't wan't to recall the thing. But of course, how much can an the orbital bomber loiter? It either is in orbit, in which case it has limited windows in which it can attack, and you could put a payload up there with an ICBM to do the exact same thing. Or it is re-entering in which case it's not going to have alot of fuel to hang around anywhere, and you wouldn't want it hanging out over it's target anyways.
-Can't be retargeted in flight (limited fuel supply)
Agian if you have intellegence that has to be acted upon in an hour or so, you generaly don't want to retarget it. But an ICBM or other launch option could pre-position a payload in space to be targeted as you wish as well. Finaly with there MIRVs (which are re-entering service now that SALTII is dead) can easily target multiple targets 1000's of km apart.
Not really. Time sensitive strikes are what its all about, to be able to hit anywhere within an hour or so of the order is impossible by any sub- or low super-sonic bomber or cruise missile unless the bomber is stationed close to the target. They do take longer, and that makes all the difference in the world in today's wars. If we lack a nearby base of operation, which is increasingly likly, they are all but useless for time sensitive strikes.
Time sensitive strikes are a myth. Frankly, our intellegence isn't good enough to give us these sorts of targets. And if it is, it's generaly because we have conventional forces staged close enough to gather the intel and then carry them out. The turn around time on other intellegence assets (spy satilites, wire tapping, radio intercepts, human intell), is still a matter of days. Furthermore, most time-sensitive targets (people) are mobile, and could still easily leave the location in the time it takes for ANY weapon to get there (an hour or so at best).
The B-52 is a sitting duck to modern air defenses, and the B-1 is not much better with its only slightly higher speed. The B-2, as nice as it is, is only a few in number with most reserved for SAC bombers. Its stealth isn't perfect either, and doesn't work at all when it rains. Adsorbed water vapor also wrecks its stealth, which makes upkeep quite hard and expensive.
The B-52 and B-1s can launch stand-off AGM thousands of km away from it's target, and never come within range of it's air-defense systems. While the B-1 is getting rather dated, it is still a tough target and can get to it's target much faster. In any case, buying more B-2's (even at a billion or so each) is probably more economical than building the orbital space bomber.
Cruise missiles are also not a panacea of weapons either, the Tomahawk warhead is not very powerful and the ALCM supply is low after the Bosnia campaign. A modern attack submarine or Ageis warship only carries a dozen and a few dozen respectively, which will take time to rebuild and have to be reloaded in port. A hypersonic bomber could be reloaded multiple times per day with inexpensive munitions. And they do have to be prepositioned, which a hypersonic bomber does not. This is a big deal.
The Tomahawk carries a 1000lb warhead. Which is more than enough to destroy everything but hardened bunkers. Most ALCM have a payload of about twice that. And while the supplies may be low now, how many orbital space bombers do we have in inventory? And I have a hard time believing they are going to be able to turn the hypersonic-cryogenicly fueled orbital space bomber around multiple times per day. Even if they could, we certianly won't have that many "time critical" targets to use it on. Nor do I suspect it's KE weapons, which have to have pin-point accuracy at hypersonic speeds are going to be cheap either. Now sea-launched delivery methods have to be pre-positioned, but they already are. And would continune to be even if we deployed a orbital space bomber.
No current cruise missile is suited for deep penitration attacks either, and advanced low-altitude air defenses can indeed counter them. Why do you think Iran bought all those Russian low-altitude missiles when JDAM-armed jets could fly above them? 1000km is also not always enough, unless the launch vehicle is close enough to be attacked.
The latest ALCM (the AGM-129) incoporate stealth technology, specificly designed to defeate such weapon systems. And 1000km away is generaly more than enough to defeate most air-defense systems, which have at best a range of several hundread km. Furthermore, developing a new cruise missle/payload with the ability to make deep penetration attacks (a rocket assisted warhead) would cost less than the orbital space bomber.
Carriers are sitting ducks to modern antiship cruise missiles, and are likewise pretty slow. The F/A-18, as good as it is, is barely a match for modern Russian air and ground launch missiles. Its pretty slow too. The JSF, which will be great for light strike, can't carry heavy penitrator weapons except externally which sacrifices stealth and its advantages.
An orbital space plane doesn't make carriers any safer, and won't change our deployment patterns of them. Upgrading their defences or even developing an entirely new line of highspeed-highpayload-stealth delivery aircraft would cost less. And as I here it, a new generation of rocket assisted penetrators is in the works, which will alow conventional air-craft to deploy weapons with nearly as much penetration power as a KE weapon.
FAE explosives can't hold a candle to the destructive power of a kinetic weapon, they can't blow up deeply buried bunkers or even armored vehicles very well, since the pressure wave is slow moving and dissapates rapidly. A carefully shaped KEM should retain most of its velocity even through reentry.
Sheer payload carriage is less important anymore to the power of said weapons, ICBMs and cruise missiles can't carry big and heavy weapons and conventional bombers and fighters can't deliver them with speed and impunity.
And lets not forget, no weapon in our arsenal (other then the 9MT coldwar megabombs) can defeat a really deeply buried bunker. Not even the big 5000lbs bunker buster. Thats where kinetic weapons may make all the difference.
If you want to dig deep enough, you can always put enough concreate/granit over your head to defeat a penetrator. No KE weapon is going to be able to hit Cheyenne Mountain for example, with the better part of a mountain above it, or any Russian/Chinese counterpart that might exists, or even some of the Terrorist camps in deep caves. For these sorts of super-heavily armoured targets, your only solution is to bomb the entrances every few days or so, and deny their utility to the enemy. I suspect the range of hardened bunkers that an KE penetrator can destroy that a more conventional weapon couldn't is rather limited, as such bunkers are rather expensive. And vrs anything but these super-hardened bunkers conventional weapons do the job just as well, for a lot less. KE weapons have no advantage over conventional weapons other than their penetration ability. And we don't have to worry if they can achive termial guidance at Mach-12+ which won't be easy. When/if we develop more powerful rocket-assist conventional penetrators the range will be even less.
I think the DOD/Airforce's program for a suborbital bomber/fighter is kind of pointless. As Robert pointed out, an ICBM/SLBM does essentialy the same thing, and we've got those (and fairly acurate re-entry vehicles to go with them) in spades. Of course, there may be political consiquences of an ICBM launch which makes it politcaly unacceptable. I can understand that. However, the conventional options the US has in it's arsenal right now can generaly achive the same thing, at a much lower costs.
I have a hard time imaging what a sub-orbital bomber could achive that conventional options could not. Our strategic bomber fleet, of B-52s, B-1s, and B-2s all have global range (with refueling). The B-1s and B-2s especialy are practicaly un-interceptable. Even the B-52s, using standoff stealth cruise missles (like the AGM-129) are practicaly invincible. It might take them a little longer to get to their target, but even with-refueling operations they would probably be much cheaper to operate. And their payloads are much greater.
If a fast time on target is desired, than cruise missles launched from our nuclear submarines (SSNs) can hit most a wide range of targets inland, and are likewise virtualy undefetable in the oceans depths. Their Tomahawks have ~1000km range, which is enough to hit most inland targets. A single sub's payload of 12 missles probably has more payload than our orbital bomber as well. We have more than enough of them, and they have enough endurance for them to be pre-positioned out at potential hot-spots. I have no doubt their are some off the cost of North Korea right now (as well as Iran).
Then we have our Carrier aircraft, which with refuling can again hit virtualy any-inland target, and while not as tough as our bombers, are still at least even with their opponents. When the JSF comes on line (if it ever does), it should easily remedy any problems we have their. A flight of F/A-18 Hornets carries more payload then the the sub-orbital bomber would as well.
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So what does the sub-orbital bomber have that conventional options don't? I suppose from a certian point of view it doesn't have to violate other nations air-space to hit it's target. Frankly, I think our political concurns about air-space are overblown. Most countries lack the ability to do anything about a US violation of their air-space, and even those that do few would actualy do anything about it (besides some diplomatic complaints). Heck, generaly if a B-2 or Cruise Missle overflew most countries (including, in some respects, the US) they likely wouldn't even know it unless we told them.
They have the ability to deploy "KE" weapons. Frankly, "crowbars from space" are overated. Even with a good re-entery vehicle air friction saps a lot of there velocity to begin with. Let's say you drop an at orbital velocity, ~30km/s or so. Even without friction losses, that's only ~34MJ/kg. Which is good, but FAE explosives can do about this good, without being dropped from orbit. And if you lose half of that energy to the atmosphere (not an absurd proposition, you would still be coming in at Mach 12) you would have only ~8MJ/kg, which is only twice as good as TNT, and no doubt worse or comparable to military explosives (which I don't have figures for on hand). You could get a lot of penetration, but conventional explosives have already proven capable of penetrating most any bunkered target. And a conventional bomber would be able to carry thousands of pounds of bombs, and have no issues with trying to hit a small target at Mach-12.
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Although I suppose if military development of a sub-orbital bomber is the price I have to pay for scramjet technology, I guess it's worth it. But the whole concept seems rather pointless to me.
Bah, any civilisation advanced enough to go truly interstellar must fall into one of two catagories.
A) They use some sort of STL (Slower Than Light) travel, and have developed a society stable enough to remain cohesive despite the decades to centuries of seperation bettwen systems. This seems to prohibit large scale warfare.
B) They use some sort of fast STL of FTL travel and thus have weapons of incredible scale. If you can harness the kinds of energies/physic manipulation to quickly make transit bettwen systems, then warfare could get really messy. Planet smashing and the like. This also seems to proclude warlike civilisations. But even if they did still exist, the level of warfare they would engage in would not be very manpower intensive, so humans wouldn't have much role in it. Indeed, their warships and weapons would probably be entirely automated. If we were usefull at all, it would be as slave labor.
Why going "up" ( from Venus to Mars ) , to need "considerably more" energy than going "down" from ( Saturn to Mars)?
I think we could even PRODUCE energy from the higher specific orbital energy of the mass falling from Saturnian to Martian orbit, and this extra energy to power the other terraformation needs...
Two reasons why it is "cheaper" energy wise. Primarily because Saturn has a gigantic gravity well, and Nitrogen from Titan has to escape that well to get to Mars. Even after adding Titan's orbital velocity, it still takes some 30km/s to break free of Saturn's orbit. Which is three times Venus's escape velocity of ~10km/s. And this disregards Titan's own gravity well, which is on the smallish side.
Secoundly, Titan's greater distance from the sun means that you must either accept a slower delivery time, or go faster. Furthermore, since Venus is so close into the sun, it can make very effective use of solar sails to transport it's cargo to Mars. Cargo from Titan cannot make as effective use of this.
This assumes in both cases that the cargo only has to intersect Mars orbit (ie, crash onto the planet). Cargo from Venus has to slow down and cargo from Titan has to speed up if you actualy want to go into orbit.
Hmmm. First, the density of the Titanian air is ~4 times greater than on sea level on earth. The PRESSURE is 1.5 times bigger. Even in heaviest spacesuit any human will be chilled by the -180C wind in minutes. The air IS poisonous - it contains 5-6% methane... Thus it is explosive indeed if leaks in O2 air in a habitat. But the disadvantages of such environment are compensated in great degree by advantages -- in that cold the water ice is hard as quarz, perfect constructional material... the deep cold means better and more efficient heat machines. Out-door superconductivity... etc.
The density of the air is irrelevent to most applications. It means that heat will be lost a little faster, line of sight is shorter, and drag is greater, but that's about it. The denser nature of the atmosphere isn't any more hazardous to people then water is.
Second, while Titan is very cold, such cold is not insurmountable. Modern insulation is very good at trapping heat. Sometime earlier I calculated that the amount of energy needed to warm a habitat in the face of a serious leak was trivial in comparison to other energy needs an outpost would face. Now, Titan cryo-suits would still probably need some active heating, but this is easily done as I pointed out, as Titan's atmosphere has methane which the suit can burn (with it's oxygen) for heat. Any comparision to "space suits" is irrelevent, as the two would be totaly diffrent in opperation. Indeed, suits designed to deal with vacume generaly have to worry more about getting rid of heat as the human body produces a great deal and vacume is such an effective insulator.
Lastly, the atmosphere is NOT poisonous. Neither Nitrogen nor Methane is toxic to the human body in the way CO2 is. Of course you couldn't survive breathing such an atmosphere, but it is not absourbed into the blood like CO2. CO2 is absourbed into the blood by your lungs, which can kill you. Kill you very quickly infact, at the concentrations it is present on Venus. Even a slow leak is dangerous, as when oxygen is at partial pressures where it is still breathable, the CO2 concentration could rise to the point where it's toxicity would kill you. Worse yet, the Venutian atmosphere no doubt also contains high concentrations of carbon monoxide (CO) as well. Not only is it toxic in the same way CO2 is, it will also bind up the O2 in your lungs and blood and kill you at much lower amounts.
That's not to say that the cryogenic atmosphere of Titan isn't hazerdous. It is both very cold, and potentialy explosive. But it is a more managable hazard. A base could much more easily deal with a slow leak, by increasing heating to displace lost heat, and watching out for sources of flame, or possibly leave candles or other igniters out to burn it before it reaches dangerous levels. If a Titan outpost operates at 1.5atm or higher, the partial pressure of oxygen can be much lower than it is here on earth, and so the methane may not be as explosive as you might think as well.
I don't really see how transporting the nitrogen from Venus to Mars in gasbags is feasible. Gasbags are too fragile; a single micrometeorite (and there are MANY between Venus and Mars) would puncture the gasbag, and suddenly the whole shebang would empty like a runaway balloon. No gasbag would make it to Mars.
A common myth. Space is actually pretty darn empty. The odds of hitting a signifigant chunk of matter in transit bettwen Venus and Mars is pretty much nill. And there is no reason a self-sealing gasbag could not be developed.
Another possibility is freezing the nitrogen in Venus orbit into solid chunks -- 100% nitrogen asteroids -- and then push them onto a trajectory for Mars. Put a homing beacon on them to track them for extra logistic control.
Not a terrible idea, but there are problems. Space quite frankly isn't cold enough for liquid nitrogen, especialy as close in to the sun as Venus is. The nitrogen will melt/sublime away into the vacume. Now, the rate of this will be fairly slow, but it signifigant losses will happen enroute.
* Venus is more easily accessible than Titan. Distance: Venus wins.
True enough. However, Venus's gravity is much higher (even at the altitudes we are talking about), which makes getting of the planet much more difficult. Titan has to worry Saturn's gravity (as well as radiation belts). On the other hand, Venus is much closer to the sun, which also creates more intense radiation worries.
* Venus aerostats are based on hot air balloon/zeppelin design, with which mankind has centuries of experience. Titan airtight domes are basically untested, undeveloped tech. Simplicity of tech: Venus wins.
These aerostats are going to require some sort of large scale air-tight system that an outpost on Titan would require. And while we may have some experience building blimps and zepplins, these are a far cry from the mega-aerostats that are going to be necessary in the Venutian atmosphere. In Titan's favor, the only disaster they have to worry about is an puncture, which isn't necessarily deadly considering the atmosphere isn't poisionus, just nearly cryogenic. A Venutian aerostat would have to worry about leaks and failure of there blimps, which would lead to terrible plumet of doom to the planet surface.
* Venus 50km altitude is the most Earthlike environment in the solar system. No pressure differential = no explosive decompression if punctured. Habitable temperature, easy access to oxygen and nitrogen for breathing air. Environment: Venus wins.
The atmosphere is still full of toxic CO2, it's not like you can go out without a mask. Titan's atmosphere is slightly thicker than Earths (1.5atm), but not to a troublesome degree. The outpost could be be run at either overpressure (to prevent atmosphere incursion) or normal Earth pressures, which ever proves more benifical. People can stand either. It is cold, but protection from the cold and and an oxygen supply are all that would be required. Heck, you could use your oxygen supply to burn some of the methane in the atmosphere to give you the heat you needed. And while Nitrogen and Oxygen are present on Venus, the Nitrogen is fairly rare, and you have to break down the CO2 to get O2, which isn't that easy. Titan has plenty of Nitrogen, and O2 is easy to get from water electrolisis.
Furthermore, the surface of Titan is as bad as it gets. Plunge deeper into the Venutian atmosphere, and you are into some bad trouble. Aerostats should also be possible on Titan, hot air-ballons would work realy well there.
* No pressure differential = much less mechanical stress for envelope to resist. Venusian aerostats can be constructed of more lightweight material, as long as we pick a suitably acid-resistant one. Actually building on Titan will require metal/rock style heavy construction in order to withstand the pressure differential. Venus will do with acid-resistant cloth bags. Lighter, cheaper materials. Weight and price: Venus wins.
Even at high altitudes Venus still has signifigant gravity, much higher than Titans. So in fact the structures would have to be stronger than they are on Titan. Also, the Aerostats are going to require some HUGE mega-structures. CO2 does allow for more boyancy than our atmospher, but not by alot. To support any amount of weight you are going to need some large gas bags. And as I pointed out earlier, the pressure diffrence on Titan is not realy a big deal. People can easily function at much higher atmospheric pressures, but even if they couldn't, resisting half an atmosphere of pressure is chump change. Also, Titan habitats can be constructed out of native material, which will not be so easy on Venus.
Which brings on my last, most critical point. An outpost on Titan has access to all the material it needs for construction and expansion. Getting minerals on Venus is going to be VERY difficult, as people and equipment simply can't function for long periods of time on the surface. Furthermore, Titan has easy access to huge amounts of water for drinking and rocketfuel. Venus is very hydrogen poor, and so getting a large enough supply of water just for the colonists needs will be difficult. Fueling rockets will be just about impossible.
* What about not bothering with separating N from CO2, and just shipping the whole 96:3 mixture as-is to Mars from Venus? Maybe deal with the CO2 on the Mars end, binding it to the biosphere there? Could they use any CO2 or do they already have more than enough?
Not such a good idea. Mars seems to have great deal of CO2 present in it's ice caps, more than enough. Especialy since CO2 is poisonous to us in even low concentrations. I guess a CO2 heavy atmosphere is better than no atmosphere at all, but not by alot. We would be better off converting that CO2 into O2 and sending that to Mars, though there seems to be plenty of that there as well.
In either case, the energy costs of seperating the elements we desire from the ones we don't is much less then the amount of energy it would take to transport the unrefined materails to Mars. However, in Titan's case, we could use all the elements of it's atmosphere, so sending it back unrefined makes more sense.
The Landis aerostat theory seems viable for Venus, and gas processing is going to be a crucial tech for the aerostats. If we use unmanned aerostats, gas processing can even be their whole singular purpose. Assuming minor investment in gas processing tech, would it be reasonable to assume that gas processing the N from Venus and shipping to Mars would take less energy than mining from the easier Titan and shipping to Mars? If we have manned aerostats, they're going to want to have surplus nitrogen production anyway, to have storages of nitrogen for emergency purposes.
It would certianly take less energy (even with refining) but that doesn't mean it would cost less. Venus aerostats are going to be difficult and expensive to construct, while a colony on Titain is probably going to be much simpler.
I think the amount of Sulfuric Acid (or any kind of acid for that matter) is going to be VERY limited. Venus is to hydrogen poor, and far to hot for it to exist in any quantities. In fact, if there are any signifigant concentations of hydrogen they are tightly bound to some rocks inside the crust.
This is not to say that SO2 is realy nice to play around with either. But in all honesty, in comparision to the crushing heat and pressure of Venus, the chemical concurns are rather minor.
The SSME startup procedure, since it operates at such extremely high pressure and temperature, is very complex; many valves must be opened and closed in a particular sequence at exactly the right time for the engine to properly ignite. You would need to carry an additional Helium bottle for tank pressurization, and you would need some kind of small thruster to effect propellant settling. The big reason is though it was never intended to be fired in the icy vacuum of space nor more then once between careful inspection and refurbishing. Just look at the thing, does it look like its going to be easy to make a "cheap" version or modify it to ignite in the freezing vacuum after hours or days of the initial firing with minimal fuel "weight" versus sunny Florida at 1G? Even if it were reliable enough to fire repeatedly between overhauls, which its not.
The SSME as an upper stage makes great sense if your lower stage is under-powerd (CLV), or you have a really big payload (HLLV). There is just that niggling issue of getting it to air start and/or fire more then once per mission. Trouble is, this performance comes at too high a complexity.
I'm not sure what your point is here. Yes, the SSME is very complex, however on the other hand this complexity hasn't lead to any major trouble. It has proven to be reliable despite it's complexity. The shuttle already carries some Helium for valve opperation and tank pressurisation. I guess I just don't understand the diffrence bettwen air and vacume start. What makes it so difficult to re-start the engine in outerspace?
NASA needs the CEV, and it needs it now, and so whichever engine is used for the upper stage needs to be as closely based off the SSME or J-2S as is practical. Scaling up the J-2 isn't happening, it would be nice if you could squeeze a few more percent of thrust out of it, but no serious alterations to it are nessesarry or desireable. Perhaps NASA ought to focus on taking the current "luxury model" SSME and just make it work first, and then make a simplified model later.
This is one of the nice things about the current approach. It is very possible for us to design and launch a simple CEV now, and then later upgrade it with better engines later. Unlike the shuttle, which has virtualy no upgrade path. So maybe an RS-68 or an RL-10s now, and a simplified SSME later.
The SSME has fantastic Isp for a first stage, but only at altitude. During the first minute or two of acent, the air pressure is high compared to how much the propellant gasses expand, and so actually the RS-68 is dead even for Isp until getting up high. Then there are the gravitational losses to consider, and a quartet of RS-68s would have 16% more thrust then a quintet of SSMEs, and so using them instead should not cost as much payload as simple calculations indicate.
While this is true, it is less important in the situations we are talking about anyways. Both the shuttle and the HLV will have those huge solid rocket boosters to help eliminate gravitation losses, and get into the upper atmosphere more quickly. It still seems to me that the SSME is still ideal (aside from cost). In the Shuttle Derived heavy lift vehicle we will be building, it will be playing essentialy the same role it did in the orignial Shuttle, where it plays secound fiddle to the Boosters untill it gets to alltitude.
The only thing "wonderful" about the SSME is its high Isp at altitude and above-average reliability, thats it, thats all, period, end quote. In every other respect, its a terrible piece of equipment, and its especially a joke given its design purpose of reuseability. Due to its very high complexity, the thing cost triple at least what expendable engines (RS-68, RD-0120) do per-thrust.
Saying it is only excelent at reliablity, thrust, and ISP is kind of silly, because really these are three of the most important issues in rockets engines. And while it's cost may be high, it is a one time cost. The things can be re-used like 30 times each. Even with refurbishment costs, I have no doubt that re-using them will be cheaper on a per-thrust basis then any other engine.
Now lets not start this engine pod debate again, we've been over this before. Even with a self-righting ballistic reentry, you still:
-Need a heat shield at least 8m wide, and if it must be bigger then this, it will stick out the edges of the main tank.
-Need power, communications, tracking, and mission control for it
-Route fuel lines, structural connections, and wiring through the heat shield
-Airbags, parachutes, altimiters, airspeed indicator, accelerometers, etc
-Must resist impacts greater then designed for (soft Shuttle landing)
-Must not be damaged by plasma wake during reentry or hypersonic air
- Heat shield - a valid concurn. Sticking the 5 SSME underneath the HLV is a strech to begin with, and the engine pod does not improve things. I think the only solution to this is to either mount the thing off-axis (as in the shuttle) or redesign the main tank so they can fit. As the tank is going to have to be redesigned somewhat anyhow, I don't see how this is an issue.
- Routing things through the heat shield - The shuttle routs fuel-lines (and probably some control lines) through it's heat shield some how, so it can't be that big an issue.
- Airbags and control equipment - This stuff is already out there and can be picked up off the shelf without issue (like the parachutes). Some control systems and redudent sensors (esp accelerometers) are going to be needed on the first stage even if it is re-usable.
- Landing Impact - With a proper parachute size this shouldn't be that much greater than the shuttle's landing (which isn't realy all that soft). Besides, these things withstand take-off (3 G's or so) and re-entery and all the vibration hazards associated with both, so I don't think it's going to be that big an issue.
- Re-entery damage - The heat shield should be designed to keep them out of the wake obviously. The shuttle has to return through that same air, so this also should be doable.
Just as importantly though, if you lose the thing, you are in big trouble. How long does it take to build a new one? How much does that cost? If you have a time-sensitive launch (say, a Mars departure window) and your engine pod burns up then you can't put it on the next one. So how much does multiple backup pods cost? Or what if there is a snafu durring refurbishing/recovery?
There will have to be multiples, obviously. The pods aren't so large and complex that it should take all of the two-years or so bettwen launch windows to build another one.
Then there is the development... how much is THAT going to cost? Four RS-68s cost about $60-80M a flight, so unless recovery, refurbishing, and amoratizing construction costs anywhere close to this then I'm sure the development cost will wipe out any real cost advantage. Which you will have traded for having a proven, easy, fast arrangement that reduces the risk NASA will "run out of steam" politically before ever getting the HLLV off the ground if development drags on.
Boeing seems pretty confident that it can do just that, with total refurbishemnt costs for similar systems to what we are talking about comming in at under $60 Million. Rember the pod is going to bring back not just the engines, but any gimbles and associated equipment to. While I can see the need for a quick HLV development, an engine pod still seems to make sense as an later development.[/url]
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While I semi-agree that the US is probably going to avoid the RD-0120 for political reasons, it's not entirely impossible that a US company could license the design and produce a copy here. If the price was right, and they could be convinced of a need for it, I'm sure they could.
It would take considearbly less energy to transport, but extracting it is tricky. Venus's atmosphere is only ~4% Nitrogen, so a considerable amount of air will be have to be collected and processed before you get anything usefull. On top of that, Venus is an incredibly hellish place, so the entire operation will have to based in orbit, while Titan provides a quite nice operating platform.
However, the energy considerations are considerable. It would take a lot less delta-V to get the air from Venus to Mars then it would Titan to Mars. The trips are a lot shorter as well. And since Venus is so close to the sun, it's a prime target for use of a Solar Sail as a delivery method.
I've been wondering about this for some time. One the main points of the SSME concept was that it was an at least semi-reusable engine. Other engines of course can be restarted for multiple firings if necessary, but they were still disposable. The SSME was the first (as far as I know) engine that was designed to be recovered and reused considerably. They take the things back to Stenis, give them a look over, test fire them, and then remount them on the shuttle. I think they are good for 20 or so firings. The fact that this is possible at all should seem to bode well for their re-start in vacume. I just wonder why this is (apparently) not the case.
But it also occurs to me that using a SSME as an upper stage engine realy is sub-optimal. Unlike some other more general purpose, rocket engines, they truely were designed for their role in the shuttle. As a first stage recoverable engine, they realy are first class, high ISP, hight thrust, proven reliability, and reusability. So if at all possible, this is the role in which they should be used. There high cost does make throwing them away rather wastefull. On the other hand, their high cost and complexity are probably at least partialy due to their high performance characteristics. I wonder how much cost a "mass produced" SSME or scaled up J-2 would cost in comparision.
So they should be used on the first stage of our HLLV, they are more expensive, but they are undoubtably the best at what they do. The requirments are very similar to those for which they were initialy designed after all. No other engine comes close in terms of Thrust and ISP. There cost means they should not be thrown away if possible. I know GCRN's objections to an "engine pod" with the things, but I wonder if such a concept might be worthwhile in the end anyways. The HLV is going to be around for quite a while (hopefully) so maybe some investment in this now makes some sense.
I've also been thinking that since the HLV is going to have an upper stage which performs it's circulisation burn as well as injection burn, it might be possible to launch the engines on a balistic path which eliminates the need for some sort of OMS to facilitate their re-entery.
Politicaly speaking, Stenis is probably still going to be around as a engine test sight if nothing else. But continuing SSME production would also be a nice bone to throw them. I also think it's a shame to have developed such a wonderful engine and then just throw it away.
Due to the speed involved with aerobraking, you actually want to come in fairly shallow and not straight on nose first. Doing so greatly reduces the heating on the vehicle, and makes a light-weight heat shield practical instead of something really thick and heavy. Those 1-2G loads are with a shallow decent too I bet. In this case, a TransHAB might not be practical, with the force of entry being on a corner which would complicate the structural loads and heat shield design. You couldn't just have a big flat disk shield on the front.
There are definetly alot of methods for aerobraking, but I don't see the advantage in going at it nose-on as opposed to anyother posture, regardless of angle of approach. Certianly going at it shield first would have the advantage of being inhernitly stable. As for the re-entery G loads I quoted, those are from the Shuttle, which does have a fairly gentle re-entery profile in general, and is certianly moving much slower than a Mars Mission would be. 1G is the typical load with 2G's being the structural max. Soyuz does re-entery at about 4G's. But as I said at the start, aerobraking can very greatly depending upon your profile, and if you are only shooting for aero-capture then the load shouldn't be as bad.
De-inflating the HAB isn't going to work very well I think. You could gain alot of structural strength by filling the walls with perminantly hardening foam. Also, I doubt you could get it to fold up so nicely as when it was packed on Earth too. It might be possible to use a fabric heat shield to make TransHAB aerobraking practical, but that would take some work.
I agree that folding the thing back up would be impractical, but it's not technicaly impossible, by any means. If you plan on folding the thing up during re-entery and don't unfold it untill you fire-off you TMI burn, then there realy isn't any reason to make the walls super stiff. Strong enough to resist puncture and what not for sure, but they shouldn't face any signfigant loads in zero-g.
In any event, why? We aren't going to colonize Mars with chemical or simple nuclear engines, they really aren't practical. And, if we have some advanced propulsion system, we can easily afford short transit times, which will mean speeds higher then are possible for aerobraking.
I was think more in terms of ITV being used in more near term missions. In fact, one of the ideas I've been toying around with is how to get the logistics of a re-usable ITV working. Such a vehicle would benifit greatly from the Trans-hab concept, as it wouldn't be hampered by the need to land on a planet.
A folding rigid heat shield would be very hard, considering the absolutely-can't-leak seals. I think it makes it hard enough that it defeats the purpose of a TransHAB, you may as well stick with metal walls if one of them has to support a rigid heat shield. A fabric or ablator shield is the only option for a TransHAB. Again, I think this is moot anyway, since we aren't going to use aerobraking for colony ships.
I mostly agree on the rigid fabric heat shield concept. However, if we could keep the load down to where a metal heat shield could be used, I could see how a folding-metal shield could be used. The metal shield is unfolded by whatever means works best (inflation, mechanical, whatever). The metal plates are fitted into a semi-tight lock during this process. During re-entery the metal plates would expand, very effecticly sealing the joints bettwen them. Proper joint design (sawteeth or what not) could lead to a very effective hold.