Completely wrong. Actually, producing rocket fuel out of the Martian atmosphere would be just about the easiest part of the trip. Doing it requires nothing more advanced than 19th century technology. NASA perfected the Mars-atmosphere-to-rocket-fuel process in the lab decades ago. This is one of the relatively few things about a Mars mission that enjoys wide consensus among scientists. In-situ fuel production is easy. It's really elementary chemistry.
well, I wonder if its so easy, why it isnt easy and cheap to produce rocket fuel ON EARTH itself! if rocket fuel is so easy to produce, it should be cheap enough to make the cost to LEO fall below the U$1000 per kilo!
Mars has less gravity than Earth. On Earth we complicated all too much because 1g make the things complex.For Mars simple Methane/Oxygen is proposed. For escape from Earth, this mixture was horrible.Make methane is simple.
Whats your take on it?
The easiest rocket propellants to make on Mars are carbon monoxide and oxygen. This has been demonstrated and is actually the basis of the technology behind Bloom Energy's fuel cell (though operated in reverse for a fuel cell).It's much easier than Methane/LOx, since you don't need to deal with hydrogen. The vast majority of the Martian atmosphere is CO2, which you can put right into an electrolysis cell and get CO on one side and oxygen on the other. Both are only mildly cryogenic. In fact, given the same industrial base, it may be easier to produce rocket fuel from the atmosphere of Mars than it is on Earth!Can you tell that CO/O2 rocket propellant ISRU on Mars (or, interestingly, in Mars orbit) is a hobbyhorse of mine?
Mars you have several options for fuel, the most promising being the Sabatier method of extracting methane and hydrogen peroxide from just the atmosphere of Mars.
Quote from: Robotbeat on 04/25/2011 04:32 pmThe easiest rocket propellants to make on Mars are carbon monoxide and oxygen. This has been demonstrated and is actually the basis of the technology behind Bloom Energy's fuel cell (though operated in reverse for a fuel cell).It's much easier than Methane/LOx, since you don't need to deal with hydrogen. The vast majority of the Martian atmosphere is CO2, which you can put right into an electrolysis cell and get CO on one side and oxygen on the other. Both are only mildly cryogenic. In fact, given the same industrial base, it may be easier to produce rocket fuel from the atmosphere of Mars than it is on Earth!Can you tell that CO/O2 rocket propellant ISRU on Mars (or, interestingly, in Mars orbit) is a hobbyhorse of mine? Um, the Bloom process requires water.
Quote from: Downix on 04/25/2011 04:48 pmQuote from: Robotbeat on 04/25/2011 04:32 pmThe easiest rocket propellants to make on Mars are carbon monoxide and oxygen. This has been demonstrated and is actually the basis of the technology behind Bloom Energy's fuel cell (though operated in reverse for a fuel cell).It's much easier than Methane/LOx, since you don't need to deal with hydrogen. The vast majority of the Martian atmosphere is CO2, which you can put right into an electrolysis cell and get CO on one side and oxygen on the other. Both are only mildly cryogenic. In fact, given the same industrial base, it may be easier to produce rocket fuel from the atmosphere of Mars than it is on Earth!Can you tell that CO/O2 rocket propellant ISRU on Mars (or, interestingly, in Mars orbit) is a hobbyhorse of mine? Um, the Bloom process requires water.Producing CO/O2 most certainly does NOT require water using the technology that became eventually used for Bloom Energy's fuel cells.
Quote from: Robotbeat on 04/25/2011 05:22 pmQuote from: Downix on 04/25/2011 04:48 pmQuote from: Robotbeat on 04/25/2011 04:32 pmThe easiest rocket propellants to make on Mars are carbon monoxide and oxygen. This has been demonstrated and is actually the basis of the technology behind Bloom Energy's fuel cell (though operated in reverse for a fuel cell).It's much easier than Methane/LOx, since you don't need to deal with hydrogen. The vast majority of the Martian atmosphere is CO2, which you can put right into an electrolysis cell and get CO on one side and oxygen on the other. Both are only mildly cryogenic. In fact, given the same industrial base, it may be easier to produce rocket fuel from the atmosphere of Mars than it is on Earth!Can you tell that CO/O2 rocket propellant ISRU on Mars (or, interestingly, in Mars orbit) is a hobbyhorse of mine? Um, the Bloom process requires water.Producing CO/O2 most certainly does NOT require water using the technology that became eventually used for Bloom Energy's fuel cells.According to Bloom's website it does.
Quote from: Downix on 04/25/2011 05:37 pmQuote from: Robotbeat on 04/25/2011 05:22 pmQuote from: Downix on 04/25/2011 04:48 pmQuote from: Robotbeat on 04/25/2011 04:32 pmThe easiest rocket propellants to make on Mars are carbon monoxide and oxygen. This has been demonstrated and is actually the basis of the technology behind Bloom Energy's fuel cell (though operated in reverse for a fuel cell).It's much easier than Methane/LOx, since you don't need to deal with hydrogen. The vast majority of the Martian atmosphere is CO2, which you can put right into an electrolysis cell and get CO on one side and oxygen on the other. Both are only mildly cryogenic. In fact, given the same industrial base, it may be easier to produce rocket fuel from the atmosphere of Mars than it is on Earth!Can you tell that CO/O2 rocket propellant ISRU on Mars (or, interestingly, in Mars orbit) is a hobbyhorse of mine? Um, the Bloom process requires water.Producing CO/O2 most certainly does NOT require water using the technology that became eventually used for Bloom Energy's fuel cells.According to Bloom's website it does.Why don't you show me a link, then? In none of the technical papers I've read on CO/O2 electrolysis is it mentioned that water is necessary for the process. Burden of proof is on you; I looked and could not find it. I cannot prove a negative.
You still haven't shown additional water is needed. You're guessing it does, for some reason.http://www.techbriefs.com/component/content/article/3495This article doesn't ever say water is required (though obviously if you're using it for producing syngas for producing hydrocarbons, hydrogen is needed... but NOT just for producing oxygen and carbon dioxide!). Can you show me any instance that says electrolysis of CO/O2 requires water?
Quote from: Robotbeat on 04/25/2011 10:00 pmYou still haven't shown additional water is needed. You're guessing it does, for some reason.http://www.techbriefs.com/component/content/article/3495This article doesn't ever say water is required (though obviously if you're using it for producing syngas for producing hydrocarbons, hydrogen is needed... but NOT just for producing oxygen and carbon dioxide!). Can you show me any instance that says electrolysis of CO/O2 requires water?What do you call "Steam" then but water? The mention of the Bloom process requires the input of Natural Gas with oxygen and gets water and CO2 output. To run that in reverse, you need water and CO2 input to get natural gas and oxygen output.I am not saying you need water for electrolysing CO, I'm saying that the Bloom process mentioned above does, and it's right there on their website and in the presentation given. So, to return to topic, there is a method to do this, but the one mentioned is not it.
Quote from: Robotbeat on 04/25/2011 04:32 pmThe easiest rocket propellants to make on Mars are carbon monoxide and oxygen. This has been demonstrated and is actually the basis of the technology behind Bloom Energy's fuel cell (though operated in reverse for a fuel cell).It's much easier than Methane/LOx, since you don't need to deal with hydrogen. The vast majority of the Martian atmosphere is CO2, which you can put right into an electrolysis cell and get CO on one side and oxygen on the other. Both are only mildly cryogenic. In fact, given the same industrial base, it may be easier to produce rocket fuel from the atmosphere of Mars than it is on Earth!Can you tell that CO/O2 rocket propellant ISRU on Mars (or, interestingly, in Mars orbit) is a hobbyhorse of mine? What performance do you get from CO + O2?I guess you have three options:CO + LOXHydrocarbon + LOX, using H2 feedstock from EarthHydrocarbon / H2 + LOX, using water from surface ice
maybe it IS easy to produce rocket fuel on Earth and on Mars, and out of the U$3000 per kilo that SpaceX needs right now, only about U$100 per kilo are due to fuel.
Tass, what's the source for that image? It's kind of amazing.
Quote from: alexterrell on 04/25/2011 10:23 pmQuote from: Robotbeat on 04/25/2011 04:32 pmThe easiest rocket propellants to make on Mars are carbon monoxide and oxygen. This has been demonstrated and is actually the basis of the technology behind Bloom Energy's fuel cell (though operated in reverse for a fuel cell).It's much easier than Methane/LOx, since you don't need to deal with hydrogen. The vast majority of the Martian atmosphere is CO2, which you can put right into an electrolysis cell and get CO on one side and oxygen on the other. Both are only mildly cryogenic. In fact, given the same industrial base, it may be easier to produce rocket fuel from the atmosphere of Mars than it is on Earth!Can you tell that CO/O2 rocket propellant ISRU on Mars (or, interestingly, in Mars orbit) is a hobbyhorse of mine? What performance do you get from CO + O2?I guess you have three options:CO + LOXHydrocarbon + LOX, using H2 feedstock from EarthHydrocarbon / H2 + LOX, using water from surface iceYou can get about 300s if pump-fed and with an extended nozzle (remember, you're practically at vacuum on the surface of Mars). Not great Isp, but better density than Methane/LOx. In other words, it can be superior to hydrocarbon/LOx at Earth Sea Level.Another option is to harvest water moisture from the Martian soil, which would allow you to get water just about anywhere on the surface (though with the difficulty of having to move soil around).
What about trying to use genetically-engineered bacteria to produce whatever fuel is convenient? At least with bacteria you have distributed redundancy - lots of little bioreactors instead of just the one which can break down.Sure, bacteria need climate control, but that makes them good advance guinea pigs in place of humans.
There will always be those who fretfully fear of bacteria escaping and "contaminating" the Martian environment, but appropriate failsafes can be designed in.(Tell me, if an astronaut fell off a Martian cliff and cracked his faceplate open, would everybody be more concerned about the astronaut, or instead about the potential for his germs to contaminate Mars?)
Quote from: Robotbeat on 04/25/2011 11:24 pmQuote from: alexterrell on 04/25/2011 10:23 pmQuote from: Robotbeat on 04/25/2011 04:32 pmThe easiest rocket propellants to make on Mars are carbon monoxide and oxygen. This has been demonstrated and is actually the basis of the technology behind Bloom Energy's fuel cell (though operated in reverse for a fuel cell).It's much easier than Methane/LOx, since you don't need to deal with hydrogen. The vast majority of the Martian atmosphere is CO2, which you can put right into an electrolysis cell and get CO on one side and oxygen on the other. Both are only mildly cryogenic. In fact, given the same industrial base, it may be easier to produce rocket fuel from the atmosphere of Mars than it is on Earth!Can you tell that CO/O2 rocket propellant ISRU on Mars (or, interestingly, in Mars orbit) is a hobbyhorse of mine? What performance do you get from CO + O2?I guess you have three options:CO + LOXHydrocarbon + LOX, using H2 feedstock from EarthHydrocarbon / H2 + LOX, using water from surface iceYou can get about 300s if pump-fed and with an extended nozzle (remember, you're practically at vacuum on the surface of Mars). Not great Isp, but better density than Methane/LOx. In other words, it can be superior to hydrocarbon/LOx at Earth Sea Level.Another option is to harvest water moisture from the Martian soil, which would allow you to get water just about anywhere on the surface (though with the difficulty of having to move soil around).So to get back to Earth, delta V = 5500m/s, I get mass ratios ofCarbon monoxide: 6.5Hydrocarbon: 4.8Hydrogen: 3.4Based on this, I agree it's not worth bringing Hydrogen from Earth.Water harvesting might be good for a second visit, but will need careful landing selection.
Quote from: Downix on 04/25/2011 10:03 pmQuote from: Robotbeat on 04/25/2011 10:00 pmYou still haven't shown additional water is needed. You're guessing it does, for some reason.http://www.techbriefs.com/component/content/article/3495This article doesn't ever say water is required (though obviously if you're using it for producing syngas for producing hydrocarbons, hydrogen is needed... but NOT just for producing oxygen and carbon dioxide!). Can you show me any instance that says electrolysis of CO/O2 requires water?What do you call "Steam" then but water? The mention of the Bloom process requires the input of Natural Gas with oxygen and gets water and CO2 output. To run that in reverse, you need water and CO2 input to get natural gas and oxygen output.I am not saying you need water for electrolysing CO, I'm saying that the Bloom process mentioned above does, and it's right there on their website and in the presentation given. So, to return to topic, there is a method to do this, but the one mentioned is not it.Oh, for goodness sake, you only need water if you're trying to produce methane!Solid-oxide electrolysis, which eventually evolved into what Bloom Energy uses, can be used for producing CO/O2, and no water is needed. It's not the same exact technology. Yes, solid oxide electrolysis is the method I'm talking about, and NO it doesn't need water for producing CO/O2 from CO2. Sheesh.I don't know why you're passing off your misunderstanding of the technology as a reason why it's not viable.
Huh? I presume by "genetically-engineered bacteria to produce whatever fuel is convenient" you mean hydrocarbons of some sort? It would be easier to produce fuel directly than to produce the chemicals and nutrients required to keep bacteria alive. Plus you can still have failures in the support/processing systems (it doesn't really make the system redundant). The only way to make this work would be to create bacteria that would produce fuel and could survive in the ambient environment -- which would pollute the Martian environment.I don't think you've quite thought this through.
You can get about 300s if pump-fed and with an extended nozzle (remember, you're practically at vacuum on the surface of Mars).
• Flagships Program is planning a Mars Lander for 2018.- 2018 orbits provide the largest payload capacity for a landed missionin 30 years.- ISRU is being included in the planning for this mission.
By the end of the decade the ISRU project could realistically have flownfour demonstration or prospecting payloads!
This is relevant here as well:http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110002954_2011000907.pdfQuote• Flagships Program is planning a Mars Lander for 2018.- 2018 orbits provide the largest payload capacity for a landed missionin 30 years.- ISRU is being included in the planning for this mission.QuoteBy the end of the decade the ISRU project could realistically have flownfour demonstration or prospecting payloads!
if fuel is so inexpensive, wouldnt a SSTO like Skylon be much cheaper than they are already supposed to be??? Aside the initial construction costs of each Skylon, and maintainance costs, fuel is the only extra cost for Skylon, isnt it?
But yeah, it works well with the idea of an atmospheric scoop in Low Mars Orbit. Not only is Mars' atmosphere over 95% rocket fuel feedstock, but the low orbital velocity at Mars gives you a huge advantage over an atmospheric scoop at Earth.
But it definitely requires high-Isp electric propulsion (at Earth orbit you can use a tether for propulsion; not feasible at Mars... you'd need at least a high-energy arcjet).
Another idea is to have the scoop on a long, long tether. The higher the altitude of your orbit, the lower your orbital velocity is (and the less dense the atmosphere at your solar array) thus meaning you have far less drag to compensate, and the gravitational field of Mars is considerably less than on Earth, so the strength requirements for your tether are far less extreme than, say, an Earth space elevator.
Heck, if you just attach one end of the tether to Phobos... you could just scoop the atmosphere of Mars with no need for compensating propulsion (well, not for a while ), using Phobos' mass as "free" drag compensation. Also, Mars craft leaving the surface would only need a about 1km/s of delta-v to reach the end of the tether. Hmmm...
The pressure of the GOCE mission (250km), would be equivalent to what height in Mars? I.e., at what height the atmospheric drag would be equivalent?Mars pressure is 636Pa, which is close to 70km in earth. So would GOCE be equivalent to 180km orbit in Mars?
Quote from: baldusi on 04/26/2011 07:23 pmThe pressure of the GOCE mission (250km), would be equivalent to what height in Mars? I.e., at what height the atmospheric drag would be equivalent?Mars pressure is 636Pa, which is close to 70km in earth. So would GOCE be equivalent to 180km orbit in Mars?No, Mars' scale height is almost double of Earths, so Mars surface corresponds to roughly 70km on Earth and for every five we move up on Earth it corresponds to ten on Mars. So the equivalent height of 250km on Earth would be more like 360km on Mars.
Quote from: sanman on 04/25/2011 11:36 pmWhat about trying to use genetically-engineered bacteria to produce whatever fuel is convenient? At least with bacteria you have distributed redundancy - lots of little bioreactors instead of just the one which can break down.Sure, bacteria need climate control, but that makes them good advance guinea pigs in place of humans. Huh? I presume by "genetically-engineered bacteria to produce whatever fuel is convenient" you mean hydrocarbons of some sort? It would be easier to produce fuel directly than to produce the chemicals and nutrients required to keep bacteria alive. Plus you can still have failures in the support/processing systems (it doesn't really make the system redundant). The only way to make this work would be to create bacteria that would produce fuel and could survive in the ambient environment -- which would pollute the Martian environment.I don't think you've quite thought this through.
There will always be those who fretfully fear of bacteria escaping and "contaminating" the Martian environment, but appropriate failsafes can be designed in.
Quote from: baldusi on 04/26/2011 07:23 pmThe pressure of the GOCE mission (250km), would be equivalent to what height in Mars? I.e., at what height the atmospheric drag would be equivalent?Mars pressure is 636Pa, which is close to 70km in earth. So would GOCE be equivalent to 180km orbit in Mars?The "scale height" of Mars's atmosphere is ~10.8km (greater than on Earth), so the density decreases a little slower with increasing altitude than on Earth.EDIT:Tass beat me to it. Tether propulsion can't be done for Mars (though other uses of tethers are feasible!) because there are only weak and sporadic magnetic fields at Mars.
Quote from: alexterrell on 04/26/2011 10:01 amSo to get back to Earth, delta V = 5500m/s, I get mass ratios ofCarbon monoxide: 6.5Hydrocarbon: 4.8Hydrogen: 3.4Based on this, I agree it's not worth bringing Hydrogen from Earth.Water harvesting might be good for a second visit, but will need careful landing selection.For actually getting back to Earth, I'm not sure it's as good of an idea (quite a big mass fraction). I'm a fan of Mars Orbital Rendezvous, with the lander only having to get to LEO (analogous to Apollo). CO/O2 is handicapped for higher delta-v, but I think it's just right for filling up an ascent vehicle. If return propellant is too much, I'm in favor of pre-placing it with an SEP tug or perhaps having an SEP-powered Mars Transfer Vehicle.
So to get back to Earth, delta V = 5500m/s, I get mass ratios ofCarbon monoxide: 6.5Hydrocarbon: 4.8Hydrogen: 3.4Based on this, I agree it's not worth bringing Hydrogen from Earth.Water harvesting might be good for a second visit, but will need careful landing selection.
Quote from: Robotbeat on 04/26/2011 03:01 pmQuote from: alexterrell on 04/26/2011 10:01 amSo to get back to Earth, delta V = 5500m/s, I get mass ratios ofCarbon monoxide: 6.5Hydrocarbon: 4.8Hydrogen: 3.4Based on this, I agree it's not worth bringing Hydrogen from Earth.Water harvesting might be good for a second visit, but will need careful landing selection.For actually getting back to Earth, I'm not sure it's as good of an idea (quite a big mass fraction). I'm a fan of Mars Orbital Rendezvous, with the lander only having to get to LEO (analogous to Apollo). CO/O2 is handicapped for higher delta-v, but I think it's just right for filling up an ascent vehicle. If return propellant is too much, I'm in favor of pre-placing it with an SEP tug or perhaps having an SEP-powered Mars Transfer Vehicle.OK, so for Mars to Low Mars OrbitCarbon monoxide: 4Hydrocarbon: 3.3Hydrogen: 2.5If return supplies and hab module are in Mars orbit, then launch mass only needs to be a few tons. Say 5 tons launcher and 20 tons fuel.Of course, you have the same problem with fuel in Mars orbit. But a Solar Electric Tug delivering a Hydrocarbon fuelled return ship would be good.
Arcjets are more efficient from a power standpoint than ion engines. And are just as proven. Arcjets would also probably work better with the atmosphere of Mars than ion engines.
I would imagine you could operate the arcjet/scoop as a sort of electric ramjet, provided you had a low enough relative velocity (ramjets usually are only good to about 2km/s, which implies a cable of about 1500km in length... make it 2000km for margin... could also choose a more difficult "scramjet" arrangement).
As far as the tether... The length isn't nearly as much of an issue as specific strength (for a space elevator). A tether of over 30 km in length has been demonstrated in space.
And existing materials (specifically "Zylon" and a few others) have enough specific strength (plus margin) to be used in the manner I described, and stronger fibers are being developed. Even ~30km is about 3 scale heights of Mars's atmosphere, meaning the bottom of the tether would experience an atmosphere roughly 20 times as dense as the top of the tether, allowing you a pretty big difference in drag between the top and the bottom, allowing you to use a large solar array.
A thin cable would have lower drag than a large atmospheric scoop (or, rather, you could choose the altitude and size of the scoop such that the drag from the cable is insignificant compared to the drag from the scoop for a given mass flowrate).
Arcjets are flying now on commercial satellites. Just about the definition of proven.
If you pick an elliptical orbit, the drag will tend to circularize your orbit.
This whole argument started in another forum because someone was defending Mars Direct... he had read the book The Case For Mars and thinks Mars Direct is the best and only way to go.Do most people here are also proponents of Mars Direct or do you people think there are many criticisms that can go against it?Personally, I think we shouldnt even try to go to Mars before abandoning the 40 yrs old technology we use today (and it will be about 60yrs old when we go to Mars) and get cheaper access to orbit and cut transit times at least by half (instead of 6 months, no more than 3 months).
I've already decided methane is the best fuel for Mars ISRU.
Zurbin probably looked at a lot of propellant combinations as well before settling on methane for similar reasons.
The thing is that methane requires either bringing hydrogen from Earth or digging in the soil. It's a good fuel, but these things will handicap it until there is substantial infrastructure built on Mars.CO/O2 doesn't suffer from those drawbacks. Its feedstock is available everywhere on the planet's surface straight from the atmosphere, in much the same way oxygen is available here.Both are good solutions with different pros and cons.