Silane Hoppers - Use the CO2 man...

MarsGuy2012 · 2003-04-06 23:56:35

If you've read Case for Mars you should remember brief mention of this. It is found on pages 201-204. As part of the Silicon purification process which would be used to manufacture solar panels and other electronics silane is created.

The Silane (SiH4) burns in Carbon Dioxide!!! Most other rockets discussed for Mars use Oxygen. The Oxygen in these combinations is about 3/4 the total propellant weight.

If you build a silane rocket hopper you can refill your CO2 tanks every time you land. It gives you about three times the range of a methane/oxygen rocket. It can also be used in a ramjet (since it has solid exhaust products it can't be used in jet or combustion engines).

Using a fuel that burns in Martian air seems the natural way to go - very efficient. The main drawback I see is manufacturing the silane. You get it from the regolith (harder than making methane and oxygen from the air).

I don't know how much power it would use or how long it would take to produce either.

What do you think?

Let's not compare it to nuclear rockets right now. I just want to focus on the chemical competition. I think it could be a good early addition to a Mars base. Politicians might limit the use of nuclear applications on Mars in the early years; Nuclear rockets might have a long timeline; etc. So, just chemical for now.

MarsGuy2012 · 2003-04-06 23:57:43

One more thing...

What else burns in CO2?

MarsGuy2012 · 2003-04-17 10:34:01

Well after 40+ views and no replies this could mean two things:

1. I am the only one in here who knows what burns in CO2, or

2. Nobody cares about my stupid little Silane Hopper.

I will not let my ego be bruised so I will assume its #1.

I will now enlighten you all with my profound knowledge of the subject. :;):

Diborane (B2H6) and Silane (SiH4) both burn in Carbon Dioxide (CO2).

Diborane has a specific impulse of 300 seconds, but is rare on Mars.
Silane is found everywhere on Mars, but has a specific impulse of 280 seconds.

A use for these fuels other than for planetary hoppers might be for Mars Sample Returns.

This is what is required for a Methane/Oxygen fueled MSR mission:
1. A 300 watt RadioIsotopic Thermal Generator (RTG)
2. An In Situ Propellant Production Plant (ISPPP)
3. Seed Hydrogen (about 1/18 the total propellant mass).

If you didn't want to use radioactive materials (the RTG) or if you didn't trust the ISPPP, you could use a Diborane/CO2 fueled MSR which would require:
1. Solar Panels
2. A pump to aquire the CO2
3. A tank full of Diborane (about 1/4 the total propellant mass).

Personally I favor the Methane/Oxygen approach because it demonstrates a vital technology (ISPP) for human missions that would follow. But, if you want to get the 'Anti-nuclear' vote or if the people in charge are skiddish about the ISPP you should use the Diborane.

RobS · 2003-04-17 14:14:31

Actually, I suspect ISPP is more reliable than diborane because there's no history of developing rockets using it. Probably no one knows what diborane will do to a fuel tank after a few years, for example. There's good knowledge of methane and oxygen fuel, however.

-- RobS

Shaun Barrett · 2003-04-17 20:36:38

Humble apologies, MarsGuy2012.
I noticed your question about what substances burn in CO2 but ignored it. I was expecting someone to jump in and give you a chemistry lecture, so I thought I'd just keep out of the way!

Until someone here at New Mars mentioned burning silane in Mars' atmosphere (it might've been RobS or Robert Dyck, I'm not sure now), I didn't know it could be done.
I did attempt a very brief google search for other chemicals that would burn in CO2 but had no luck. I decided I knew way too little to get involved in this kind of discussion and left it alone.

You're quite right not to let the deafening silence about your question bruise your ego. It was a good question! It's just that I, for one, was too stupid to know the answer and, in retrospect, too rude to say so!
Sorry.

Josh Cryer · 2003-04-17 21:41:22

Hey, I should note that I'm probably adding to the page views (this is maybe my fourth or fifth time reading this thread). I'm just waiting for someone to enlighten you (and me!).

The idea in and of itself sounds quite facinating. Though, like most vehicle designs, I question the comfortablity factor. Are we going to be jolted about much?

dicktice · 2003-04-18 07:50:04

Shaun: Aren't you confusing stupidity with mere ignorance of a specialized field of engineering? If MarsGuy had written out the equation of the combustion reaction including the composition of the exhaust, and stated it in words; we who aren't in-the-know might have appreciated the overall benefits of burning Diborane (?) in carbon dioxide and been able to comment intelligently.... How about it, MarsGuy. Illucidate!

MarsGuy2012 · 2003-04-18 09:42:44

Here's the equation for the Silane reaction:

SiH4 + 2CO2 --> SiO2 + 2C + 2H2O

In this reaction only 27% of the propellant mass is silane. You get 73% of your fuel from the air. All you need is a pump and probably some dust filters. SiO2 and C are both solids so you can only use this fuel in a rocket, ramjet, or to fire a boiler of a steam engine. (Locamotives on Mars? ??? )

I'm not exactly sure about the Diborane reaction, but here is a try:

B2H6 + 3CO2 --> B2O3 + 3C + 3H2O

I know the left side of the equation is correct - I just guessed on the right side, though.

This is the extent of my knowledge on the subject. I also tried to find other fuels that would burn in CO2 on the web but came up empty.

P.S. Good point RobS. If the diborane eats through your fuel tank it won't do us much good, will it?

Hazer · 2003-11-26 13:14:09

Quick question everyone, how would the density of the Martian atmosphere affect the burning of silane? I like the idea of burning silane with CO2, but I was wondering if the low density of the Martian atmosphere might hinder the burning-and require us to collect CO2 before running the engine.
I really like the idea though.

Addendum:
Silane (Silicon hydride)
Boiling point
-112C
All silanes (There are multiple types!) are spontaneously inflammable in air and oxygen. SiH compounds are good reducing agents. I'll look some more into this.

Addendum 2: I'll see if I can get my hands on some silane, CO2, vacuum chamber, and a Sterling Engine.

RobS · 2003-11-26 23:54:02

I assume you'd have to compress the Martian air before using it to burn the silane.

-- RobS

Hazer · 2003-11-27 01:14:41

Yeah. One more question, how is this silane produced on Mars?

RobS · 2003-11-27 09:54:05

Good sol to everyone and Happy Thanksgiving to those who participate in this venerable American family ritual. We are on our way to Chicago for Turkey and Persian rice (with Iranian-American relatives) in a few minutes.

The recipe for silane is given in the Bible (I mean, The Case for Mars), page 202:

Start with SiO2 (sand)

Heat in the presence of carbon, producing silicon and carbon dioxide. This is a very endothermic reaction. Possibly the remnants of my left-over turkey can be reduced to carbon for this purpose (sorry, I'm joking).

Bathe the hot silicon with hot hydrogen gas. This produces silane (SiH4).

-- RobS (who just bought the dessert pies for the family feast)

Hazer · 2003-11-27 22:42:21

Thanks, I'll see what I can do.
Er, RobS, where were you planning to get this hydrogen gas? I mean, here on earth we can get it via simple electrolysis-but is there enough hydrogen on Mars for us to use?

Addendum: Our pineapple and cherry cobbler was a good source of carbon

RobS · 2003-11-28 09:42:47

You have to have an energy source to make silane, obviously. Mars Direct assumes a 3.5 tonne, 100 kilowatt (electrical) reactor. Any Mars outpost for 4 crewmembers and in situ resource utilization needs about 100 kilowatts of continuous power. That reactor converted only 5% of its heat to electricity. If a 15% Stirling engine were used the reactor would make 300 kilowatts, or a 100 kilowatt reactor could be made for closer to 1.5 tonnes.

Solar power could do it as well. The surface of Mars receive 500 watts of continuous solar power per square meter when the sun is overhead. Divide by pi and you get the average power output over an entire sol: about 150 watts per square meter. If the panels are 33% efficient in making electricity (which is now theoretically possible) that means a square meter will make about 50 continuous watts of power (none at night of course, but more during the day). Thus you need 20 square meters to make 1 kilowatt and 2000 square meters to make 100 kilowatts (which will be cut in half or more during dust storms). If solar panels mass 4 kilograms per square meter, then 100 kilowatts requires 8 tonnes of panels. That's much better than Zubrin assumed; he had to assume 10% efficient panels (which was what was available in the early 1990s). You can't deploy all those panels robotically, so you can't easily use solar power without a human crew to install it. In my Mars-24 project I assumed a series of four relatively small cargo landers and two shuttles, each deploying six-kilowatt arrays, which were robotically connected together with cables; that produced an initial solar powered network with 36 kilowatts, which can make the needed fuel for a shuttle in two years without people around as well.

One can also use windmills. There is a windmill advertised on the web that makes 50 kilowatts (on Earth) in a 25 mile per hour wind with blade 46 feet in diameter. I figure with the thinner Martian air, one would need a windmill of the same design to make 5 kilowatts in a 25 mile per hour wind if it had 100 meter (328 feet diameter) blades. You'd want to put them on top of hills or crater rims to maximize exposure to wind. Crews would have to set them up and maintain them, and they'd be big and bulky. Martian gravity would help. You could make the blades pretty easily from martian materials and just import the generator.

-- RobS

Bill White · 2003-11-28 13:31:12

You have to have an energy source to make silane, obviously. Mars Direct assumes a 3.5 tonne, 100 kilowatt (electrical) reactor. Any Mars outpost for 4 crewmembers and in situ resource utilization needs about 100 kilowatts of continuous power. That reactor converted only 5% of its heat to electricity. If a 15% Stirling engine were used the reactor would make 300 kilowatts, or a 100 kilowatt reactor could be made for closer to 1.5 tonnes.
* * *
-- RobS

This may be off thread yet I believe the following idea flows nicely from the RobS comment:

(I have deleted my solar chimney response from here and moved it to another thread.)

Ian Flint · 2003-11-29 12:22:24

Er, Hazer, If you haven't been paying attention, they are finding more and more water on Mars all the time. Water is full of hydrogen.

Hazer · 2003-11-29 13:09:29

Uh yeah, but I was under the impression that they wanted to use this water for things like drinking, growing food, et cetera. Ah well, my worries may be a load of bahooey if there is enough water on Mars.

SpaceNut · 2016-07-25 20:32:41

Bump

Silane seems to cover current and past discusion....

fix the artifacts and shifting that were in this very old topic....
wow its from 2003

Burning silane

https://www.linkedin.com/pulse/what-sil … ert-morlan
AAEAAQAAAAAAAAW9AAAAJDhiYzdmNjk1LTZiMDYtNGU1Yy1hZGNhLTFiMGE1ODg0N2Y1NA.jpg

elderflower · 2016-07-26 06:28:12

Because Silane will burn to Silicon Dioxide it will not be useable in internal combustion engines, including gas turbines. The Silica will be deposited on the relatively cool parts and either wear the engine away or coke it up, or both. It could be used in external combustion equipment such as Rankine or Sterling cycle engines. These would be easier to decoke and there need be no moving parts in the exhaust stream.
Another easily portable energy source is peroxide. If the concentration is sufficient its breakdown produces steam and oxygen. The higher the concentration the higher the temperature of the breakdown products (=superheat in the steam fraction), the more oxygen you get and the more power you can extract in your expansion turbine. On the downside the higher the concentration the less stable the stuff becomes and (above about 60% H2O2) the higher the boiling point, which translates into heavier tanks). Stabilizers are available which would help, here.
SHOULD HAVE BEEN ABOVE 60% THE HIGHER THE FREEZING POINT. sorry!

Last edited by elderflower (2016-08-06 15:25:16)

Antius · 2016-08-01 04:58:47

I wonder if it is possible to decompose the silane and liberate hydrogen gas? This could then be oxidised with CO2 in a fuel cell. No good for a flying machine, but could work in a rover. I suppose the same thing would work for any hydrocarbon and doesn't need silane specifically.

Has there been any research into CO2/H2 fuel cells?

JoshNH4H · 2016-08-01 11:56:57

On the face of it, a CO2/H2 fuel cell sounds like a pretty bad idea. Because Carbon is a gas, you could only oxidize to Carbon Monoxide. The energy gains from this reaction are actually very minor and so it's probably a bad candidate for a fuel.

It would make more sense to supply both the fuel and oxidizer and use ambient CO2 as a propellant to increase the propulsive efficiency. This is the function that the nitrogen in Earth's atmosphere serves.

knightdepaix · 2016-09-10 12:56:15

Besides carbon monoxide and dioxide, oxocarbons also included carbon suboxide and other oxides. Could carbon suboxide as a liquid burn in carbon dioxide and is the exhaust carbon monoxide ? While some hydrogen could be used as fuel starter, local factory that use such C3O2 fuel can use the exhaust CO for metallurgy or metal refining.

SpaceNut · 2021-04-16 21:11:06

bump

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#1 2003-04-06 23:56:35

Re: Silane Hoppers - Use the CO2 man...

#2 2003-04-06 23:57:43

Re: Silane Hoppers - Use the CO2 man...

#3 2003-04-17 10:34:01

Re: Silane Hoppers - Use the CO2 man...

#4 2003-04-17 14:14:31

Re: Silane Hoppers - Use the CO2 man...

#5 2003-04-17 20:36:38

Re: Silane Hoppers - Use the CO2 man...

#6 2003-04-17 21:41:22

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#7 2003-04-18 07:50:04

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#8 2003-04-18 09:42:44

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#9 2003-11-26 13:14:09

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#10 2003-11-26 23:54:02

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#11 2003-11-27 01:14:41

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#12 2003-11-27 09:54:05

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#14 2003-11-28 09:42:47

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#15 2003-11-28 13:31:12

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#16 2003-11-29 12:22:24

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#17 2003-11-29 13:09:29

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#18 2016-07-25 20:32:41

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#19 2016-07-26 06:28:12

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#20 2016-08-01 04:58:47

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#21 2016-08-01 11:56:57

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#22 2016-09-10 12:56:15

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#23 2021-04-16 21:11:06

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