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http://www.flightinternational.com/Arti … +Mars.html
This link is to an article about a developing Ion engine thye hjope to use eventually to transport humans to Mars.
Feedback please. I thougt Ion engines were WAY too slow for a manned mission???
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They're just chattering... having a great ion engine is less then half the battle, since the mass of the power source is the real killer.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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I think Ion engines could have applications toward manned exploration but only for the cargo-transport element of it.
Power sources will become less massive over time but given the actual thrust of an ion engine regardless no human being will wait in low orbit for several months straight especially when other systems can get them to the moon in a matter of days.
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Even then though, the price of a reuseable ion tug must be weighed against the economies of scale of building more copies of a chemical vehicle.
If an ion tug can last for 15 years, thats enough life span for five trips to and from Mars, will it be cheaper to build such a thing then it would to build five copies of the chemical vehicle?
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Even then though, the price of a reuseable ion tug must be weighed against the economies of scale of building more copies of a chemical vehicle.
If an ion tug can last for 15 years, thats enough life span for five trips to and from Mars, will it be cheaper to build such a thing then it would to build five copies of the chemical vehicle?
Consider the possibility of a lunar LOX tug where there's a stronger need for resusability. If its a craft on a one-way trip the use of an ion drive will only be merited if its a long trip.
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There is no way the economics of developing a reusable nuclear-electric Ion tug would work out for even Mars cargo supply, better to just apply the economies of scale to expendable nuclear thermal or chemical upperstages.
Eventually reuseable infrastructure will be needed but we havn't gotten their technologically or time-line wise.
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Lunar LOX is a red-herring, without a ready supply of fuel (hydrogen, methane, etc) the Lunar tug will need about as much imported Hydrogen as it would to simply send LOX from Earth for whatever hypothetical Mars vehicle.
An ion drive is too expensive for one-trip missions except to the outer planets. Even then, it would require a nuclear power plant with far superior specific power to anything presently or near-term available to be much better then traditional nuclear thermal engines.
The mass of the power plant (solar or nuclear) really kills the ion engine, without more power per-pound the ion drive is not any faster then chemical for Earth/Mars runs, and so it can't compete with chemical.
Solar power has some room for improvement, but it will not be the order of magnetude improvement needed to make an ion tug fast enough to compete with chemical without becomming too expensive (large areas of crystalline GaAs cells).
Nuclear power plants are definatly not going to get a whole lot lighter, and they aren't good enough for ion engines without needing to be scaled up to unrealistic and unaffordable sizes.
Getting to Mars is easy...
Step 1: Equip your payload with a biconic aerobrake shield which doubles as a payload shroud, as called for in NASA's DRM-III mission plan. Launch on CaLV without an EDS stage.
Step 2: Build a stretched version of the Lunar EDS stage and put it on top of NASA's biggest CaLV varient, just like the Moon missions but with extra fuel instead of a Lunar lander. Mate the Mars vehicle and the stretched EDS and go to Mars.
Step 3: Repeat steps 1 and 2 to get what you need to Mars. The heavy 125 tonne CaLV has just enough payload capacity to not need nuclear engines to push a reasonable sized vehicle to Mars.
For supply missions when you don't need a large Mars vehicle, the CaLV could put a Mars payload on top of the EDS instead of a Lunar lander.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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I agree. Even if H2O ice is found, it is unlikely that a Lunar LOX facility would be cheaper than lifting it from Earth by HLV or hopefully an even lower cost COTS alternative. The enormous cost of developing the ISRU technology and its infrastructure (tankers, onorbit depots etc etc) would have such a long pay back time it would probably be made redundent by other developments. In any case ISRU is needed on Mars and that will be a different CH4 based technology. H2O ice ISRU could be useful later at the Martian poles and for local Lunar exploration fuel needs.
[color=darkred]Let's go to Mars and far beyond - triple NASA's budget ![/color] [url=irc://freenode#space] #space channel !! [/url] [url=http://www.youtube.com/user/c1cl0ps] - videos !!![/url]
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Somehow I think infrastructure will be more a matter of bureacracy than actual engineering - the ISS being a prime example.
An LOX Ion tug doesn't need a port to dock at, no more than a Progress vehicle does. Send it to rendevous only with either a propellant lander in Low Lunar Orbit or the vehicle to be refueled. Depending on how long a tug is designed to last, maybe once or twice in its lifetime a smaller (disposable) tanker rendevouses to refuel its ion drive. After ten years at most scrap the tug and send up a replacement. If it breaks down leave it be - or if its hazardous send another tug to 'nudge' it out of harms way.
No orbital infrastructure, no refueling depots unless you count the production facility on Luna itself. Russia has both Progress and its upcoming replacement, ESA will soon have its own cargo vehicle; autonomous docking tech is there.
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Trouble is, a chemical tug could make the trip many more times then the ion tug - just three days one way - while the ion tug will be doing well to best six months. Thats a big difference.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Lunar LOX is a red-herring, without a ready supply of fuel (hydrogen, methane, etc) the Lunar tug will need about as much imported Hydrogen as it would to simply send LOX from Earth for whatever hypothetical Mars vehicle.
Only a red-herring if its a chemical propellant tug. If its ion driven a few tons of xeon would last several years; if an oxygen-propellant ion drive is developed all the better - fuel exclusively from the moon.
You do have one point though: the "fuel" to go with the oxygen is all the moon lacks. Mars can provide that in time or even Titan and the outer solar system in the distance future. Using Lunar Oxygen just lowers the weight from Earth, as I'm sure you've heard from other LOX advocates.
However, I'm going to add this point: don't develop the LOX tug just yet. Its putting the carriage before the horse; the horse in this case is the LOX production facility - in situ propellant production and all. In a stripped-down space program tugs are indeed luxuries. Their time will come when we have something self-sufficent started. If we're worried about hauling cargo though through space radiation you can be sure people will be wanting unmanned tugs doing the job.
Don't depend on LOX to get to Mars, not initially - but it will come in handy if we intend to stay there.
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Huh? An ion engine powerd by oxygen would have terrible performance and would break down almost immediatly. Ionized oxygen is horribly corrosive.
"Using Lunar Oxygen just lowers the weight from Earth, as I'm sure you've heard from other LOX advocates."
But it wouldn't, it takes alot of oxidizer and fuel to launch anything from the Moon, and if you have to import Hydrogen or Methane from Earth, it will actually require launching more propellant from Earth to deliver this fuel to the Moon then it would to simply launch the propellant to a ship waiting in Earth orbit.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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"Using Lunar Oxygen just lowers the weight from Earth, as I'm sure you've heard from other LOX advocates."
But it wouldn't, it takes alot of oxidizer and fuel to launch anything from the Moon, and if you have to import Hydrogen or Methane from Earth, it will actually require launching more propellant from Earth to deliver this fuel to the Moon then it would to simply launch the propellant to a ship waiting in Earth orbit.
...so apparently we're back to square one refueling exclusively from Earth you suggest?
So I guess we should trash the VSE since it will be canceled within the next 2 administrations then since that will be how long it will take to even prepare to reach Mars (which could provide both oxider and propellant needs) - oops no funding since Katraina II obliterated Florida.
Say is that an asteroid coming? Guess we won't see it coming since Hubble is dead and the Web telescope broke.
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Yes, but thats what the CaLV is for, and it should be able to lift large amounts of rocket fuel for about half the price or less of any other available rocket.
The Space Shuttle has been an abject failure for the last thirty years, but NASA is still here. Its a popular agency, and as soon as they show that the past is behind them and they are competant at getting back in the rocket business, then funding will probably be pretty steady.
Hubble nor JWST are used to watch for killer meteors, and Hubble has already exceeded its reliable design life.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Why are we even bothering with Ion Engines? Nuclear Pulse Detonation, Anti-matter, and just about anything that's not a solar sail will go faster than the ion engine. Even the old liquid oxygen/hydrogen will go faster.
The ion engine has a very high exhaust velocity because the particles being expelled from the engines are going pretty fast. However, the particles aren't very big, making the energy coming out very little. It would be good for long distance travel, not short distance trips like mars.
Now let me explain anti-matter engines. The thrust is fast, because the particles are being expelled at the speed of light (being light after all, it has to go at the speed of light). The acceleration would be relatively fast because of the insane amount of energy coming out of the rear due to e=mc^2.
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Why are we even bothering with Ion Engines? Nuclear Pulse Detonation, Anti-matter, and just about anything that's not a solar sail will go faster than the ion engine. Even the old liquid oxygen/hydrogen will go faster.
Its the fuel economy that makes an ion engine worth considering is why. The engineering is what's being debated.
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It's the fuel economy that makes an ion engine worth considering is why. The engineering is what's being debated.
If there was an engine that could get you to Mars in 50000 years but got 100000000 miles/gallon (really good fuel economy), would you consider it? How crummy does the engine have to get before you realize it sucks.
Edits were for formatting purpose only.
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Getting to Mars is easy...
Step 1: Equip your payload with a biconic aerobrake shield which doubles as a payload shroud, as called for in NASA's DRM-III mission plan. Launch on CaLV without an EDS stage.
What a neat idea it would be to place a folding heatshield within a cargo vessel to be attached and used for Mars entry into its atmosphere. One could probably make this item in space from scrap soyuz or progress ships if one used the ISS as a staging location. Could this be adapted to the engine pod recovery from orbit possibly.
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Folding heat shields are a non-starter. Don't even go there, expecially not from Aluminum (which melts at ~600 degrees) from left over Progress capsules. And don't forget the payload penalty to reach ISS orbit from Florida. Plus the engine pod has about 600%+ more thrust then you need for TLI/TMI, so the rest of the SSMEs would be "dead weight," not that they were intended to be restarted without refurbishing, in space no less.
*shakes head vigerously to clear out the dizziness of crazy ideas*
Just make a conical heat shield that doubles as the payload faring, problem solved.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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An anti-matter engine is a looong ways off. We can't produce, store, nor safely launch large amounts of anti-matter by any stretch of the imagination.
Also, despite its very very high fuel efficiency, you still need an awful lot of it to produce much thrust. The engine that you describe =VT= is a type called a beam drive, where matter and anti-matter combine to form EM energy/photons. Trouble is, its all in the extreme gamma-ray range, which will cook your crew and your ship without an awful lot of shielding.
Trying to couple anti-matter reactions to heat rocket fuel has the same problems as nuclear rockets, that the heat you can reach limits the efficiency, and the heat is limited by the melting point of your rocket.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Now let me explain anti-matter engines. The thrust is fast, because the particles are being expelled at the speed of light (being light after all, it has to go at the speed of light). The acceleration would be relatively fast because of the insane amount of energy coming out of the rear due to e=mc^2.
You couldn't be more wrong about this. While it is true that an anti-matter engine would have tremendously incredible fuel efficency, or specific impulse, the thrust that they can produce is generaly pathetic. While it is true that e=mc^2, this does not mean that expelling light is going to give you an incredible change in momentum (which is what thrust relates to). For a object with 0 mass (like light) the relevenat equation is E=pc (E energy, p momentum, and c is the speed of light). Which generaly dictates that for most sane energy expedature rates of anti-matter you are going to be looking at very, very, little thrust. Mainly because there are limits to the amount of anti-matter you can react without blowing your ship up. The thrust to weight ratios of most pure (ie undilluted) anti-matter drives are pathetic. Generaly much less so than of the ion-drive which you seem to berate.
Also, you are generaly incorrect in your assumtion that anti-matter engines are driven by photons. While it is true that there are anti-matter engines that rely upon photons, they are generaly not the most popular in the public conciousness. They rely upon large blocks of tungsten or some other dense/high melting point substance to absourb the radiation from an anti-matter drive and re-radiate it as lower-energy photons (which can be reflected with mirrors and the like). While potentialy very efficent, they have perhapce the worse thrust-weight ratios as the tungsten block is very heavy and the rate at which you can react the anti-matter is very slow (because you don't want to melt the block).
Most proposed anti-matter drives rely upon magnetic containment to re-direct the pions and kaons that an anti-proton proton collision creates for propulsion. The rest of the energenic radiation (primarily gamma radiation) is far to high energy to be re-directed as a propulsive source, and so is lost.
He who refuses to do arithmetic is doomed to talk nonsense.
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Now let me explain anti-matter engines. The thrust is fast, because the particles are being expelled at the speed of light (being light after all, it has to go at the speed of light). The acceleration would be relatively fast because of the insane amount of energy coming out of the rear due to e=mc^2.
You couldn't be more wrong about this. While it is true that an anti-matter engine would have tremendously incredible fuel efficency, or specific impulse, the thrust that they can produce is generaly pathetic. While it is true that e=mc^2, this does not mean that expelling light is going to give you an incredible change in momentum (which is what thrust relates to). For a object with 0 mass (like light) the relevenat equation is E=pc (E energy, p momentum, and c is the speed of light). Which generaly dictates that for most sane energy expedature rates of anti-matter you are going to be looking at very, very, little thrust. Mainly because there are limits to the amount of anti-matter you can react without blowing your ship up. The thrust to weight ratios of most pure (ie undilluted) anti-matter drives are pathetic. Generaly much less so than of the ion-drive which you seem to berate.
So an antimatter engine would act much like an ion engine, except more gamma-radiation?
That problem with photons having no mass could be altered if, instead of an anti-hydrogen + hydrogen reaction something more like an anti-hydrogen + helium, or lithium, or even better something heavier and more common like oxygen, methane, even kerosene (obviously that last suggestion would be applicable in vehicles only in Earth's vicinty). There wouldn't be a complete annihalation, and not even a whole gram of antimatter would be needed to send a few tons of propellant into a frenzy to rival the velocity of a nuclear rocket.
I think the only big risk is just containing antimatter, and after that containing it safely during launch. Don't rule out antimatter just yet. If the radiation from a few hundred pounds of fission material can boil tons of water surely the same principle can be applied with antimatter and propellant.
Still, antimatter isn't for the short-term. Easily a few decades needed - I don't want a misguided rocket with an antimatter source blowing up within my own Timezone let alone my state!
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I think the only big risk is just containing antimatter, and after that containing it safely during launch. Don't rule out antimatter just yet. If the radiation from a few hundred pounds of fission material can boil tons of water surely the same principle can be applied with antimatter and propellant.
Safety comparisons with "plain" old nuclear fuel are bad, because there is no way for nuclear fuel to become really dangerous so long as it is not brought critical, which with a properly designed reactor simply cannot occur. Uranium decays so slowly, that its is basically not radioactive (radiation intensity and duration are inversely proportional).
Antimatter on the other hand, all of its energy would be immediatly radiated as hard high-power gamma rays if there were any leak, creating a burst of deadly radiation. And thats if the thing leaks, which I find to be a... disquieting possibility if you put it on top of a rocket.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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So an antimatter engine would act much like an ion engine, except more gamma-radiation?
Sort of. A typical magnetic confinement based engine uses a stream of extreamly high velocity quarks (that's what Pions and Kaons are). Like .9C or better velocities. These particals quickly decay into more gamma radiation, but they are out of your engine by that time. While a conventional ion engine is pushed by lower velocity, higher mass ions (atoms striped of electrons). The faster, lighter particles a anti-matter engine uses gives it a much higher ISP, but the thrust is generaly not signifigant, as the containment equipment is very bulky, and the particals are very light.
That problem with photons having no mass could be altered if, instead of an anti-hydrogen + hydrogen reaction something more like an anti-hydrogen + helium, or lithium, or even better something heavier and more common like oxygen, methane, even kerosene (obviously that last suggestion would be applicable in vehicles only in Earth's vicinty). There wouldn't be a complete annihalation, and not even a whole gram of antimatter would be needed to send a few tons of propellant into a frenzy to rival the velocity of a nuclear rocket.
Sure you can dilute the anti-matter with other matter, and use it primarily as a heat source, but this results in a few problems.
#1. The heavier particles are obviously going to move slower, which results in a lower ISP, but higher thrust.
#2. Containing the hot-matter becomes an issue. This limits your propellent velocity to that similar of a NTR. As magnetic containment is rather impratical, and there is a limit to the heat materials can withstand without melting. Which limits you to NTR type performance.
#3. It may be the case that the containment device for the anti-matter weighs more than the radioactive source would for the NTR, in which case the thrust to weight ratio would be inferior to the NTR.
To me the most plausible design I have seen for anti-matter engines are those that use anti-matter to catilise a fusion reaction. This could give you orion like specific impulses or better, but with out so much radiation (though more neutrons).
An idea I've been thinking about involves using positrons. If we react positrons with hydrogen atoms, annilating the electron, we would get alot of gamma radiation (which would heat the proton involved), and the resulting ion could be magneticaly directed. Sort of like a ion-engine on anti-matter steroids :-)
I think the only big risk is just containing antimatter, and after that containing it safely during launch. Don't rule out antimatter just yet. If the radiation from a few hundred pounds of fission material can boil tons of water surely the same principle can be applied with antimatter and propellant.
Still, antimatter isn't for the short-term. Easily a few decades needed - I don't want a misguided rocket with an antimatter source blowing up within my own Timezone let alone my state!
I certianly wouldn't rule it out, but you are right it is still a few decades (or more) out. Anti-matter production and containment methods certianly need more time to mature. But I've long thought that anti-matter might reach fruitin before fusion ever does. I can see a clear path for improvment in anti-matter at least, who knows when (or if) fusion will mature.
He who refuses to do arithmetic is doomed to talk nonsense.
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Work with existing technolgy drive motor systems we could use to get to mars .
Larger Vessels :
- Standard Engines ( Hydrogen / LOX )
- Nuclear Engines
- Plasma Drive
Smaller vessels and long range probes
- Standard Engines
- Ion Drvive Motors
It depends on a number of factors including duration for journey, cargo or humans, weight factors and more. So use technology now available for the journeys and returns and develop newer technologies as we move through space and build presences in space on the Moon, Mars, and orbiting on space stations / platforms.
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