Author Topic: Producing rocket fuel on Mars  (Read 28432 times)

Offline aceshigh

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Producing rocket fuel on Mars
« on: 04/25/2011 12:53 pm »
How easy is it really??

A discussion about it arose from the proposal of sending men to Phobos/Deimos instead of Mars. The argument was that it would be BETTER to send to Mars, because while on Mars you have more gravity to escape on the return, you can produce all the fuel you need on Mars itself.


I said producing fuel on Mars must not be so easy.

the person answered me:
Quote
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.



and I answered back
Quote
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!


well, its a big probability I am wrong... 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.


Whats your take on it? This forum has plenty of people who must know enough about this to tell if I am right, wrong, or partially right and wrong :)

Offline Downix

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Re: Producing rocket fuel on Mars
« Reply #1 on: 04/25/2011 02:20 pm »
It is easy to produce rocket fuel here on Earth.  My son produced some for his 2nd grade science fair exhibit.  (splitting water atoms down, then cryo-cooling the split hydrogen and ocygen)  The problem is not the fuel, it's the rest of the system. The fuel cost for a rocket is less than a fraction of a percent of the total cost of the system. 

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.
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Offline Spaniard

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Re: Producing rocket fuel on Mars
« Reply #2 on: 04/25/2011 02:43 pm »
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.

Offline Downix

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Re: Producing rocket fuel on Mars
« Reply #3 on: 04/25/2011 02:54 pm »
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.
The 1g is part of it, the thick atmosphere is the other.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline RanulfC

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Re: Producing rocket fuel on Mars
« Reply #4 on: 04/25/2011 02:59 pm »
Making "rocket-fuel" on Mars first of all has a LOT of "assumptions" added but the actual "chemistry" part IS "easy". It will NOT however be "cheap" in any sense of the term, OTHER than figuring against the cost of bringing ALL your propellant all the way from Earth.

To make fuel on Mars you have to bring the entire infrastructure AND "seed-stock" with you to start with. Here on Earth we've had hundreds of years and billions of (your-favorite-unit-of-monitary-worth-here) spent on setting up the exploration, discover, access, processing, and delivery system for general hydrocarbon fuels. All of which is "sunk" or mostly "paid-off" costs.

Fuel IS cheaper here and it will CONTINUE to be cheaper to make most of the propellant for cis-Lunar operations on Earth and ship it into space for a long time.

Until and unless we develop Lunar-Oxygen extraction and other propellant extraction and processing infrastructure with all the associated costs there.
(Once we had that resource we no longer have to spend large amounts of "propellant" MOVING propellant out of the gravity well)

Propellant costs are VERY low in the "margin" costs of space launch AS propellant. As "payload" it gets MORE expensive but with low flight rates and expendable vehicles overall it just isn't that large of a cost factor.

Some reading for you:
"Launch Vehicles: An Economic Perspective"
http://www.gwu.edu/~spi/assets/docs/NASA%20L.Vehicle%20Study%20V-5.pdf

 “When Physics, Economics, and Reality Collide: The Challenge of Cheap Orbital Access”
http://www.transterrestrial.com/archives/When%20Physics%20Economics%20and%20Reality%20Collide.pdf

"Physics, economics, and reality, part deux"
http://www.thespacereview.com/article/387/1

"The challenge of cheap orbital access"
http://www.thespacereview.com/article/395/1

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline savuporo

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Re: Producing rocket fuel on Mars
« Reply #5 on: 04/25/2011 03:30 pm »
Whats your take on it?

Why don't you start by looking at the latest research and engineering work done in that area ? Off the cuff, SRR reports gave me this :

http://www.isruinfo.com/docs/srr8/muscatello_et_al_nov_1.zip
There has probably been some more recent work ..
Orion - the first and only manned not-too-deep-space craft

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #6 on: 04/25/2011 04:32 pm »
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? :)
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Downix

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Re: Producing rocket fuel on Mars
« Reply #7 on: 04/25/2011 04:48 pm »
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? :)
Um, the Bloom process requires water.
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Offline beb

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Re: Producing rocket fuel on Mars
« Reply #8 on: 04/25/2011 05:10 pm »
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.

Peroxide?. I thought Sabatier produced methane and water.

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #9 on: 04/25/2011 05:22 pm »
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? :)
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.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Downix

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Re: Producing rocket fuel on Mars
« Reply #10 on: 04/25/2011 05:37 pm »
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? :)
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.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline Patchouli

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Re: Producing rocket fuel on Mars
« Reply #11 on: 04/25/2011 06:03 pm »
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? :)

Unlike CO/O2 Methane/Lox engines that are big enough for a MAV are not vaporware.
Three or four of these could get you back to the MTV in Mars orbit.

Since the engine is close to an RL-10 in performance specs in theory even just one or two could power a very small and light ascent vehicle but I'd want engine out capability on the MAV since once you lift off the Martian surface it's orbit or bust.
« Last Edit: 04/25/2011 06:13 pm by Patchouli »

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #12 on: 04/25/2011 06:46 pm »
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? :)
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.
« Last Edit: 04/25/2011 06:52 pm by Robotbeat »
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Offline Downix

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Re: Producing rocket fuel on Mars
« Reply #13 on: 04/25/2011 09:46 pm »
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? :)
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.
http://www.bloomenergy.com has all of the details.  If you ever study his cells, all of them emit water vapor in the guise of steam along with CO2.  Which means for it to work in reverse, you must input H2O.  Nice video for it here:
http://www.bloomenergy.com/products/solid-oxide-fuel-cell-animation/
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Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #14 on: 04/25/2011 10:00 pm »
You still haven't shown additional water is needed. You're guessing it does, for some reason. Why?

http://www.techbriefs.com/component/content/article/3495
This 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?
« Last Edit: 04/25/2011 10:01 pm by Robotbeat »
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Offline Downix

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Re: Producing rocket fuel on Mars
« Reply #15 on: 04/25/2011 10:03 pm »
You still haven't shown additional water is needed. You're guessing it does, for some reason.

http://www.techbriefs.com/component/content/article/3495
This 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.
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Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #16 on: 04/25/2011 10:09 pm »
You still haven't shown additional water is needed. You're guessing it does, for some reason.

http://www.techbriefs.com/component/content/article/3495
This 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.
« Last Edit: 04/25/2011 10:11 pm by Robotbeat »
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Offline alexterrell

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Re: Producing rocket fuel on Mars
« Reply #17 on: 04/25/2011 10:23 pm »
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? :)

What performance do you get from CO + O2?

I guess you have three options:

CO + LOX
Hydrocarbon + LOX, using H2 feedstock from Earth
Hydrocarbon / H2 + LOX, using water from surface ice

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #18 on: 04/25/2011 11:24 pm »
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? :)

What performance do you get from CO + O2?

I guess you have three options:

CO + LOX
Hydrocarbon + LOX, using H2 feedstock from Earth
Hydrocarbon / H2 + LOX, using water from surface ice
You 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).
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline sanman

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Re: Producing rocket fuel on Mars
« Reply #19 on: 04/25/2011 11:36 pm »
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?)

Offline Tass

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Re: Producing rocket fuel on Mars
« Reply #20 on: 04/26/2011 05:52 am »
Well I'll get back to the original post, which was sort of answered, but I will take another stab at it:

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.

This is pretty much correct. Probably a great deal less than the U$100 actually.



This analogy explains it well. One thing is that you have to use a lot more fuel than if you could just refuel the motorcycle on the way and ride it all the way, but the real increase of price comes from the expensive hardware that is thrown away.

Lets say to get back from Mars you have to have the bug with a full tank on Mars, that means you have to leave Earth with the entire train above. If you can refuel the bug on Mars, then you can use the gas it had to land on mars, you just have to be able to reach Mars with an empty bug tank not a full. Therefore you could do away with the tanker when leaving Earth, saving not only a tankers worth of fuel, but the tanker itself!

A little fuel on Mars can in principle save a lot of fuel on earth, and more importantly a lot of expensive hardware.   
« Last Edit: 04/26/2011 05:56 am by Tass »

Offline neilh

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Re: Producing rocket fuel on Mars
« Reply #21 on: 04/26/2011 06:54 am »
Tass, what's the source for that image? It's kind of amazing. :)
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Offline Tass

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Re: Producing rocket fuel on Mars
« Reply #22 on: 04/26/2011 07:21 am »
Tass, what's the source for that image? It's kind of amazing. :)

Well, someone posted it on another forum and I just nicked it.

Offline alexterrell

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Re: Producing rocket fuel on Mars
« Reply #23 on: 04/26/2011 10:01 am »
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? :)

What performance do you get from CO + O2?

I guess you have three options:

CO + LOX
Hydrocarbon + LOX, using H2 feedstock from Earth
Hydrocarbon / H2 + LOX, using water from surface ice
You 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 of

Carbon monoxide: 6.5
Hydrocarbon: 4.8
Hydrogen: 3.4

Based 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.

Offline madscientist197

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Re: Producing rocket fuel on Mars
« Reply #24 on: 04/26/2011 11:28 am »
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.
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.

Quote
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?)

That's something that people would worry about before humans land on Mars, not after someone cracked open their faceplate, as in practice once a crew have landed on Mars it's a little too late. Suits will leak, waste will be disposed of etc... Terran bacteria will end up everywhere.
John

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #25 on: 04/26/2011 03:01 pm »
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? :)

What performance do you get from CO + O2?

I guess you have three options:

CO + LOX
Hydrocarbon + LOX, using H2 feedstock from Earth
Hydrocarbon / H2 + LOX, using water from surface ice
You 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 of

Carbon monoxide: 6.5
Hydrocarbon: 4.8
Hydrogen: 3.4

Based 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.
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Offline Downix

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Re: Producing rocket fuel on Mars
« Reply #26 on: 04/26/2011 03:21 pm »
You still haven't shown additional water is needed. You're guessing it does, for some reason.

http://www.techbriefs.com/component/content/article/3495
This 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.
Bloom Energy uses natural gas, so it's system is not a good example, yes?

I've built solid oxide units before, it's not that difficult.  You just need to not grab just any old unit and claim that as a perfect example.  The Siemens HPD Delta is a far better example, produced by a company not so quick to produce hype as Bloom Energy has been.  A SOFC is indeed an ideal system for this kind of work.  Blooms just is not, alright?
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Offline sanman

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Re: Producing rocket fuel on Mars
« Reply #27 on: 04/26/2011 03:35 pm »
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.

Well, I don't see why Earth-origin bacteria should be considered "pollution", anymore than human beings would be considered pollution. If your astronauts are producing waste on the Martian surface, will it have to be sterilized before dumping it, for fear of contaminating the planet?

I don't think we should be walking on eggshells, worrying that we're going to damage the "fragile" Mars or the Moon. Otherwise, with that kind of handicap, we'll never be able to establish any kind of existence there. Can you imagine if the original American colonists had to avoid "contaminating" the local ecosystem with whatever they brought over from Europe? Their colony wouldn't have gotten off the ground.

Anyway, whatever the fuel is, there should be some way to manufacture it bacterially.

With bacteria, you can take a small amount to Mars (low payload mass), and then grow a whole lot more of them once there, by extracting nutrients from local material. A Martian brewery could generate the required fuel, and even be re-purposed towards producing other useful materials, just by swapping in other bacteria.

I was even reading how some bacteria can even be used to generate strong sandstone material, which could be used for building purposes:

http://youngandbrilliant.net/post/148829640

(Sorry, off-topic, I know, but it's still food for thought. Bacteria are adaptable, scalable, flexible)

Offline IsaacKuo

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Re: Producing rocket fuel on Mars
« Reply #28 on: 04/26/2011 04:07 pm »
You can get about 300s if pump-fed and with an extended nozzle (remember, you're practically at vacuum on the surface of Mars).

Does carbon monoxide/LOX really offer 300s Isp?  What are the technology risks involved in developing CO/LOX rocket engines?  I would guess that it's clean burning and maybe easier to develop than kerolox, but I'm no rocket scientist.

If CO/LOX is a good way to go, then I think it may be better to produce it in orbit rather than on the surface.  An atmospheric scooping satellite could enjoy 24/7 sunlight unhindered by atmospheric dust (nor would any dust filter be needed).  Since the fuel is produced in orbit, it starts off with a 3.5km/s head start over propellant produced on the surface.  The satellite's electric thruster could be used to raise its apoapsis into a highly elliptical orbit, providing a 5km/s head start.

Even Venus looks like a good place to produce CO/LOX.  Atmospheric scooping could be more productive in Venus orbit than Mars orbit thanks to the extra sunlight.  The frequent Earth-Venus windows and shorter trip times let tankers haul back more fuel per year.  A slingshot around Earth allows shipments to Mars without any extra delta-v cost.

Either way, orbital production of CO/LOX could be used for a wide variety of missions, including precursor missions to Deimos or Phobos.  You wouldn't need to land on Mars to access the fuel produced.  The relatively low shipping costs to Earth make it potentially useful for supplying Earth satellites and space stations.

Offline aceshigh

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Re: Producing rocket fuel on Mars
« Reply #29 on: 04/26/2011 04:39 pm »
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?

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #30 on: 04/26/2011 04:41 pm »
I don't want to oversell CO/LOx. It's likely it'd take some development time to reach 300s. Earlier engines would be lower. The biggest drawback is that we don't have a lot of experience with it. It's a really good opportunity for some low-cost NASA grants for SBIR, etc, to develop 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...
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Offline savuporo

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Re: Producing rocket fuel on Mars
« Reply #31 on: 04/26/2011 05:14 pm »
This is relevant here as well:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110002954_2011000907.pdf

Quote
• Flagships Program is planning a Mars Lander for 2018.
- 2018 orbits provide the largest payload capacity for a landed mission
in 30 years.
- ISRU is being included in the planning for this mission.

Quote
By the end of the decade the ISRU project could realistically have flown
four demonstration or prospecting payloads!
Orion - the first and only manned not-too-deep-space craft

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #32 on: 04/26/2011 05:16 pm »
This is relevant here as well:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110002954_2011000907.pdf

Quote
• Flagships Program is planning a Mars Lander for 2018.
- 2018 orbits provide the largest payload capacity for a landed mission
in 30 years.
- ISRU is being included in the planning for this mission.

Quote
By the end of the decade the ISRU project could realistically have flown
four demonstration or prospecting payloads!
Cool! :)
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Offline Tass

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Re: Producing rocket fuel on Mars
« Reply #33 on: 04/26/2011 05:16 pm »
If you shave 4km/s or more of the required return delta-v with a Phobos tether, then much of the incentive to produce fuel on Mars is gone.

Sure in some far of future we will likely have both, but both will be expensive to establish so you'd likely start with just one.

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?

Pretty much. And the first two although hopefully smaller (per flight) than for disposable rockets are far from insubstantial. 

Achieving the mass fraction required for SSTO takes very expensive technology. Maintaing that technology in a shape that is still safe after the abuse of launch and reentry is expensive too. And then there is the development cost that needs to be payed off. Finally the footnote that it burns a bit more fuel per payload than multistage rockets.

But of course is is being developed, it wouldn't be if it was not expected to be worth it.

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #34 on: 04/26/2011 05:20 pm »
I'm not convinced Skylon would be cheaper than a TSTO RLV. So many technical risks with Skylon. I actually expect Skylon to be nearly obsolete by the time it is finished (i.e. in the world where Skylon is given the eleven digits of funding that it needs is also a world where there are a lot of players who can significantly reduce the price for a much lower initial cost). We shall see.
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Offline IsaacKuo

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Re: Producing rocket fuel on Mars
« Reply #35 on: 04/26/2011 06:40 pm »
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.

The composition of Earth's atmosphere is very different.  Venus is similar, though, and could use common refining hardware.

Quote
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).

Ion thrusters are a mature technology, and would be the most practical thing to use in either case.  Tether propulsion is at best unproven.

Quote
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.

Such a tether would suffer drag of its own.  Long tethers are unproven, while ion thrusters are already in use for main propulsion.  In particular, GOCE proves the use of ion propulsion for long term atmospheric drag compensation at very low Earth orbit.

If you want the advantages of reduced drag at a higher orbit, there are ways to use somewhat elliptical orbits to get you the same advantages without the burden of a drag-laden tether.

Quote
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...

This would require a 6000km long tether, which is well beyond the state of the art as well as being a massive investment.  It would be less technologically challenging to use Phobos as a source of dumb inertial mass.  The basic idea is to fill up tanks with loose regolith simply to increase the mass of the spacecraft.  Then you lower periapsis to dip into the upper atmosphere (0.5km/s) to start aeroscooping.  Each aeroscooping pass lowers the apoapsis.  Just before full circularization, you dump the regolith tanks and raise apoapsis out of the atmosphere.  This reduces your mass for the return trip to Phobos.

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #36 on: 04/26/2011 07:14 pm »
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 like ion engines, but there are limitations.

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. Probably best to use a longer tether, though, so you can get to the point of at least negligible drag for the solar array. Extend it to 1000km, and your required energy for drag compensation propulsion is reduced by half and the drag induced by the solar array is probably barely even measurable. So there's a pretty good argument to be made for using a long, 1000+km cable, and the technical risk isn't that great.

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).
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Offline baldusi

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Re: Producing rocket fuel on Mars
« Reply #37 on: 04/26/2011 07:23 pm »
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?

Offline Tass

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Re: Producing rocket fuel on Mars
« Reply #38 on: 04/26/2011 07:31 pm »
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?

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.

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #39 on: 04/26/2011 07:31 pm »
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?
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.
« Last Edit: 04/26/2011 07:33 pm by Robotbeat »
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Offline baldusi

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Re: Producing rocket fuel on Mars
« Reply #40 on: 04/26/2011 07:36 pm »
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?

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.
So the pressure at 360km on Mars would be the pressure at 250km on Earth? It seems sort of counter intuitive.

Offline RanulfC

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Re: Producing rocket fuel on Mars
« Reply #41 on: 04/26/2011 07:59 pm »
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.
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.
Actually there isn't really a need for "genetic-engineering" since there are already a lot of ways of extracting fuel products from organisms that are well understood and proven right here on Earth. (Algae's mostly)

It's a "toss-up" actually on which process' (mechanical or biological) would be better "suited" for overall propellant production purposes. The whole thing is based on assumptions made for each process. Robotbeat's concept for CO/O2 production is pretty much based on the assumptions for a certain techniquie of production just like Zubrin's Methane/LOx system is base on a lot of his assumptions.
("Practically" neither one is "right" or "wrong" as EITHER will "work" in the end, but a serious look at trade-offs, technology, and infrastructure requirements would need to be made to narrow down the pros-and-cons of each within a SET exploration concept. As the saying goes "your-milage-may-vary" especially if someone is making base assumptions that are different than yours :) )

Genetic tweeking, (actual "engineering" or simply selective breeding programs) could make it much easier for a biological system to utilize resources we already KNOW are on Mars such as being able to survive exposure to the Martian soil, but we already KNOW that there are biologies that can survive and even thrive in Mars' atmosphere as long as suitable means are provided to raise the average temperature. Which gets back to the "bio-reactor" idea of course, which is no more (or really less in most cases) complex than doing the same job mechanically. Nutrients can be package pretty densly and there is always the case of using the 'waste' of one biological process to provide support for another so that isn't really an overall issue with the concept.

As Sanman pointed out, it's a hell of a biological pre-cursor mission concept :)

Quote
There will always be those who fretfully fear of bacteria escaping and "contaminating" the Martian environment, but appropriate failsafes can be designed in.

That's something that people would worry about before humans land on Mars, not after someone cracked open their faceplate, as in practice once a crew have landed on Mars it's a little too late. Suits will leak, waste will be disposed of etc... Terran bacteria will end up everywhere.
[/quote]
Sadly there ARE people out there already "worrying" about such contamination and as a whole they are also dead-set against taking ANY chances with "human-contamination" of other "bio-spheres" whether the subject actually HAS a "bio-sphere" or not.

While it used to be there were fears base on contaminatin traveling from space to Earth, more recently this has turned around to become a movement to ensure NO "human-contamination" goes from Earth to anywhere else. Overall while this is "supportable" due to scientific concerns the reality of this concept is that in order to carry it out the only POSSIBLE "solution" is to ensure that humans never set foot on another world.

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Offline baldusi

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Re: Producing rocket fuel on Mars
« Reply #42 on: 04/26/2011 08:08 pm »
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?
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.
If Mars is equivalent to 70km. Then 250km (GOCE altitude) minus 70 is 180km. Earth's scale is 7.64km, thus around 23.73 "scales". Times 10.8km is 254km in Mars.

Offline alexterrell

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Re: Producing rocket fuel on Mars
« Reply #43 on: 04/26/2011 08:58 pm »

So to get back to Earth, delta V = 5500m/s, I get mass ratios of

Carbon monoxide: 6.5
Hydrocarbon: 4.8
Hydrogen: 3.4

Based 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 Orbit

Carbon monoxide: 4
Hydrocarbon: 3.3
Hydrogen: 2.5

If 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.

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #44 on: 04/26/2011 09:02 pm »

So to get back to Earth, delta V = 5500m/s, I get mass ratios of

Carbon monoxide: 6.5
Hydrocarbon: 4.8
Hydrogen: 3.4

Based 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 Orbit

Carbon monoxide: 4
Hydrocarbon: 3.3
Hydrogen: 2.5

If 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.
Yeah, that's better. It doesn't sound like a big difference, but it makes ISRU much easier and smaller scale... overall more realistic. The difference is between a rocket with no payload and a rocket with a considerable payload.

Plus, it allows you to reuse a Mars Transfer Vehicle for both legs of the journey.
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Offline IsaacKuo

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Re: Producing rocket fuel on Mars
« Reply #45 on: 04/26/2011 09:11 pm »
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.

Arcjets are not just as proven.  There are no arcjet equivalents of Dawn or GOCE.   
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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).

Some sort of electric ramjet could, in theory, be more efficient than simply using some scooped up atmosphere as electric rocket thruster propellant.  But it introduces a whole new level of technology risk and R&D effort.  An electric ramjet would share extremely little with traditional ramjets.  It's a whole different beast.

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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.

Well...sort of.  If all you want is a momentary deployment and you don't care that it snaps off at the end, then sure.  But this is not acceptable for this mission, where payloads on both ends are required.

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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.

Or you could simply use a somewhat elliptical orbit, and avoid the complication, technology risk, drag, and mass of the tether system.  An apoapsis raised 300km higher than periapsis reduces drag ten-fold.

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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).

If you can simply make the scoop bigger, then you could simply make it big enough to hide your entire solar array within its "shadow".  No tether needed, just make your scoop bigger and fly at a higher altitude.

But a larger scoop means more mass for the scoop and more work for the compressor/cooler to scavenge the thin atmosphere.  If the diameter of the scoop is too large, you also have deployment complications.  So, there will be some practical limits on scoop size.

Anyway, your tether can't be too thin or it will be too vulnerable to damage.  You will want some sort of hoytether structure, so the overall drag may be similar to a 1cm wide ribbon.  Multiply that by 10.8km, and we get the drag equivalent of about 108 square meters.  If you want the tether's drag to only be, say, 10% of the overall drag, then you need a scoop 37m in diameter.  That's big!

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #46 on: 04/26/2011 09:57 pm »
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.
« Last Edit: 04/26/2011 09:58 pm by Robotbeat »
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Offline IsaacKuo

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Re: Producing rocket fuel on Mars
« Reply #47 on: 04/27/2011 02:18 am »
Arcjets are flying now on commercial satellites. Just about the definition of proven.

Proven for use in stationkeeping.  But not for main propulsion--not for high delta-v long term use, as in Dawn and GOCE.  In particular, the GOCE mission closely matches the design and requirements for an atmospheric scooping satellite.

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If you pick an elliptical orbit, the drag will tend to circularize your orbit.

This is acceptable and/or compensated for by the ion thruster main propulsion.

One method of operation where it is acceptable is to alternate between spiraling upward and downward.  Spiraling downward involves first lowering periapsis to dip into the upper atmosphere, and then repeatedly scooping (each scooping pass lowers apoapsis).  Before the orbit fully circularizes, main propulsion is used to raise periapsis above the atmosphere.  At that point, repeated thrusts at periapsis are used to raise apoapsis.

A steady state method of operation would involve using main propulsion compensate for drag in each orbit.  This can slightly raise periapsis, but that can be compensated for with tiny retrograde thrusts at apoapsis.

Either way, the available solar power can be used to refrigerate/compress/process propellant during the periods it is not used for main propulsion.

Offline Patchouli

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Re: Producing rocket fuel on Mars
« Reply #48 on: 04/27/2011 02:41 am »
I've already decided methane is the best fuel for Mars ISRU.
It has good energy density is non toxic this means engine testing on earth will be easy enough.
Getting reusability out a of methane engine also is fairly easy the Darma Chase-10 is rated for 10,000 seconds XCOR has similar ratings for it's methane engines.

Experience with handling methane rockets is now getting fairly mature.


And large quantities of liquid methane is safely transported in tankers every day.

Lastly it is versatile and can be a universal fuel for Mars.
Methane can be used in fuel cells to run rovers and provide backup power during dust storms.
http://www.gizmag.com/platinum-free-methane-fueled-fuel-cells/17064/

Land a few automated nuclear and solar powered methane fuel plants in various locations you could effectively explore Mars at fairly low risk.

This infrastructure also would be an asset for future missions and make it less likely the first Mars missions would end as flags and foot prints like Apollo.
Zurbin probably looked at a lot of propellant combinations as well before settling on methane for similar reasons.
« Last Edit: 04/27/2011 03:02 am by Patchouli »

Offline sanman

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Re: Producing rocket fuel on Mars
« Reply #49 on: 04/27/2011 02:21 pm »
Plus, at ambient Martian temperatures, methane could be conveniently kept in liquid form, and handled that way.

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #50 on: 04/27/2011 02:36 pm »
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.
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Offline aceshigh

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Re: Producing rocket fuel on Mars
« Reply #51 on: 04/27/2011 03:51 pm »
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).

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #52 on: 04/27/2011 04:07 pm »
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 don't think fighting orbital mechanics is a good idea if you're trying to get to Mars affordably.

As far as 40 year old technology goes, there are many good ideas, such as using liquid oxygen and liquid hydrogen in a multi-stage rocket, an idea which is over a century old, but the first orbital all-hydrolox rocket has only launched in the last decade. I believe it's essential to choose an architecture that will lead to RLVs naturally (i.e. prop depots in LEO), but the problem isn't "old technology." But putting our money into new launch vehicles won't help. What may help is NASA purchasing flights or propellant launched on whatever is the cheapest commercial launch vehicle, allowing the market (by helping create a market) to help develop the cheapest launch vehicle.
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Offline RanulfC

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Re: Producing rocket fuel on Mars
« Reply #53 on: 04/27/2011 09:00 pm »
I've already decided methane is the best fuel for Mars ISRU.
.... AND as far as anyone can figure out that is pretty much how Zubrin "arrived" at his decision too ;)

Truth is there are a LOT of different fuels that can be made on Mars, some "better" in some respects than others though AGAIN choosing is more a matter of intial working assumptions than actual "logic" per-se.

Zubrin also suggested Methanol, while others have chosen and shown methods of producing everything from Acetylene
http://www.uapress.arizona.edu/onlinebks/ResourcesNearEarthSpace/resources28.pdf

Hydrazine and Hydrogenperoxide:
http://www.tfd.chalmers.se/~valeri/Mars/martian_project.pdf]http://www.uapress.arizona.edu/onlinebks/ResourcesNearEarthSpace/resources32.pdf[/url

Even burning Martian CO2 with Magnesium brought from Earth:
[url]http://www.tfd.chalmers.se/~valeri/Mars/martian_project.pdf


(Mars is compatable with producing even things like Nitrous Oxide/Acetylene "fuel-blends" such as "NOFBX" :) )

A "quick" google search reveals a number of alternative concepts, plans and propellant schemes using total in-situ production or bringing some feed-stock or materials from Earth.
http://www.google.com/search?hl=en&biw=1259&bih=864&q=propellant+production+on+Mars&aq=f&aqi=&aql=f&oq=

So the choice most often comes down to perceptions.
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Zurbin probably looked at a lot of propellant combinations as well before settling on methane for similar reasons.
Actually he did a lot of work on and with Methanol after he suggested Methane, as noted though it still comes down concept, assumptions, and perception. There are numerous propellants that can be made in-situ on Mars. More so that can be made here on EARTH which was part of the original "question/post" but currently hydrocarbon Oil/Coal/Gas has by far the lowest "infrastructure" costs associated with it due to its age and depth of "monies" already spent. Any "new" fuel has to compete not only with basic production costs but the money already spent on transportation and distribution which makes "synthetic" fuels appear much less viable until and unless "regular" fuel prices increase dramatically. (And you'd be WRONG to think they have done so yet! The overall inertia of the system is such that we have YET to reach viable "break-even" points for alternative fuels to compete with gas/oil/coal despite numerous attempts to level the playing field)

As to Mars-Direct I feel it is exactly as Zubrin described it, repeating Apollo to go to Mars. Simply finding a way to make a flight to Mars "affordable" and "palletable" to the political mind is no more going to assure that the program won't be cancled as soon as the first successful landing is over the same way Apollo was. And none of the grandous plans of "follow-on" missions and colonization is any more likely with Mars-Direct than the same thing on the Moon was after Apollo-11 returned home.

ISRU is a wonderful idea, but it is only a PART of what is needed and though Zubrin and the majority of MD advocates refuse to admit it the infrastructure that they tend to dismiss as "not-needed" and "a-side-track" are in fact neccessary parts of both the learning process of living and working in space (as well as in planetary gravity wells) to the degree of being able to REALLY live there rather than just visit.

Mars-Direct as a concept and "plan" simply makes the actual concept of a mission to Mars more paletable in a political and financial sense. It does not address, and in fact ignores issues of sustainability, exploration beyond a "single-target/goal" and in-space infrastructure and experiance building. It polarizes people by demanding they are either "for" Mars or "against" it because unless they fully support "Mars-Direct" they are a "danger" to getting to THAT goal as soon as possible.

On a personal level, while I was intially impressed and awed with Mars-Direct and "The Case for Mars", etc, it did not take me long to see the various issues with applying the Apollo paradigm to a Mars mission and the enheirent flaws with focusing on a single-goal instead of the whole picture. In many ways "worse" for me was the fact that my own interests were more towards Venus than Mars and this automatically put me in the camp of "enemies" of Mars-Direct even though I was intitally supportive!

I fully believe that we either go into space with the intent of going EVERYWHERE or we are going to continue to go NOWHERE forever.

Randy
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British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline QuantumG

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Re: Producing rocket fuel on Mars
« Reply #54 on: 04/27/2011 11:40 pm »
Technology development required for Mars Direct:

* Land bigger and bigger payloads via direct heat shield aerocapture.
* Fly various tether experiments until artificial gravity (and spinup!) has been demonstrated.
* Show guidance, navigation and control on an end-over-end rotating platform.
* Modest in-space nuclear reactors.
* Radiation mitigation strategies with no hand waiving.

Of course, when NASA suggests demonstrating any of these the Mars Society gets mad because "all we need to do is declare Mars the destination and set a deadline!"

The Apollo cargo cult lives.


Human spaceflight is basically just LARPing now.

Offline Robotbeat

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Re: Producing rocket fuel on Mars
« Reply #55 on: 04/28/2011 05:43 am »
In-space nuclear power is not required or even helpful for Mars (unless you go for incredibly high power systems, but it'd cost dozens of billions for such a project, at least), and I think large ASRGs are superior for surface power (safer, longer lasting, simpler, can be mobile, no real shielding necessary) to augment surface solar. Artificial gravity isn't required, either (though, to be honest, we won't know until we do longer duration missions in space, perhaps using Mars-level gravity). Neither is radiation mitigation (well, beyond a water wall).

Enhanced EDL is required, though the degree of EDL required depends on who you talk to. ISRU is also required, as is reliable, relatively-closed-loop ECLSS.
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Offline QuantumG

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Re: Producing rocket fuel on Mars
« Reply #56 on: 04/28/2011 05:49 am »
Yeah, yeah.  My post was about Mars Direct, which calls for a modest nuclear reactor to be sent on the cargo-only mission.
Human spaceflight is basically just LARPing now.

Offline mlorrey

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Re: Producing rocket fuel on Mars
« Reply #57 on: 04/28/2011 05:53 am »
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.

Primary mission of any Mars operation beyond flags and footprints is going to be to find and refine water anyways, NASA has found plenty of evidence of buried glaciers at relatively low latitudes. Furthermore, the astronauts will produce water as a function of metabolism for the months they will be in flight and on Mars. Hydrogen is not going to be an issue.

Any serious Mars program is going to send ISRU equipment to Mars months or years before humans go there.
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Offline alexterrell

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Re: Producing rocket fuel on Mars
« Reply #58 on: 04/28/2011 08:03 am »
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).
There's a nice discussion on this forum about Phobos being a superb target.

It has water and carbon and easy radiation sheltering, and is very easy (energetically) to get to, using either chemical rockets or SEP (ideally a combination of both).

My suggestion would be to establish a permanent base on Phobos (or Deimos), with ISRU, and only then start regular Mars flights.


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