Jump to content

Silane as an ISRU Fuel


SOXBLOX

Recommended Posts

Silane, or SiH4, is the silicon analog of methane. It is pyrophoric, which, as far as I can see, means it's hypergolic, and has decent thermal properties, according to a paper I read. It could be produced from abundant silicon in the lunar crust, etc.

What do you think? Would it be a good fuel for lunar use?

Link to comment
Share on other sites

1 hour ago, SOXBLOX said:

Silane, or SiH4, is the silicon analog of methane. It is pyrophoric, which, as far as I can see, means it's hypergolic, and has decent thermal properties, according to a paper I read. It could be produced from abundant silicon in the lunar crust, etc.

What do you think? Would it be a good fuel for lunar use?

How do you plan on solving Si/SiO2 deposits in the rocket engine?

Link to comment
Share on other sites

I see three issues with silane as a choice of propellant for ISRU on the moon:

1) I assume any engine intended for this role ought to be reusable, and this seems to conflict with the fact that the exhaust of any silane fueled rocket is largely quartz, some of which will be left behind in the engine after shutdown. Solid silicon deposits may also build up in parts of the engine plumbing wherever high temperatures are experienced.  The large amount of solids and liquids in the nozzle will also reduce Isp.

2) Hypersonic quartz smoke in the exhaust will be damaging to any nearby structures on the ground and in orbit.

3) You still need large quantities of hydrogen in order to make large quantities of silane.

I'm not sure how important each of these problems would actually be in reality, but they certainly need to be either solved or shown to be insignificant in order to make silane a useful propellant.

Link to comment
Share on other sites

According to the wiki, silane looks to be a little more complicated than just having Si and H. Like catalyzing with a metal halide, is that available on the moon? I'm sure the Si on the moon isn't just pure Si laying around, how many steps and how much energy would be required to produce silane? Compared with just making hydrolox from moon stuff is it more or less energy? Silane also seems dangerous.

Link to comment
Share on other sites

So, it's probably like coking from kerosene, but worse. But would SiOeven be solid in this environment? I can't imagine fine sand blowing out of a rocket nozzle...

I'm thinking that its benefits, if any, would be the hypergolic and ISRU aspects. Like @Spica said, you still need hydrogen, which on the Moon can really only be found in ice deposits.

I was wondering if it would have slightly-worse-than-methane performance, but without needing carbon.

IDK about production of silicon from regolith. I'll check in the morning...

Link to comment
Share on other sites

A quick Google turned up a whole bunch of research about this. The answer seems to be a strong "maybe."  They're also looking at silanes for terrestrial use as scramjet fuel.

Quote

Whether or not a lunar-based propulsion system, more particularly, one based on LO2/LSiH4, will ever be developed will depend upon many factors that are beyond the scope of this paper. However, the technology to manufacture oxygen and silane on the Moon and also to develop a lunar-based propulsion system based on the bipropellant LO2/LSiH4 combination is within our reach. The development of a lunar-based propulsion system can be accomplished within the time frame under consideration, i.e., by the start of the 21st century. All that is required are the need, the will, and the funds.

From http://articles.adsabs.harvard.edu//full/1985lbsa.conf..169R/0000175.000.html

See also:

 

 

 

Edited by Guest
Link to comment
Share on other sites

Since the exhaust of some solid rocket motors can be assumed to consist of sizeable amounts of alumina, producing silicon dioxide might actually not be that terrible. At least if the design is kept simple enough. 

That said, if you're trying to process lunar regolith into rocket fuel, you might want to think about some kind of metal + oxidizer solid propellant or even a  metal + LOX hybrid design. The less hydrogen you need, the better.

Link to comment
Share on other sites

6 hours ago, Brikoleur said:

Thanks! That first one is the one I read on this, a while ago. It was in some book I got from the library...

So, oxygen can come from ilmenite, pyroxene, or olivine. The Rosenberg paper says that an initial amount of hydrochloric acid would be needed, but after that, Earth would only have to supply water. Of course, now we know that the Moon has water. Maybe this could work...

Link to comment
Share on other sites

On 5/8/2021 at 3:15 PM, kerbiloid said:

(Let alone the probable glassy remains in the chamber.)

That could give it a use not as a rocket propellant but as a method for creating a landing pad with rocket exhaust such as FAST landing pads being developed by Masten.

Link to comment
Share on other sites

On 5/10/2021 at 12:01 PM, SpaceFace545 said:

That could give it a use not as a rocket propellant but as a method for creating a landing pad with rocket exhaust such as FAST landing pads being developed by Masten.

Spoiler

Why do I see a pogo stick of glass under a rocket engine.

Landing on glass is maybe not the best idea...

Edited by Xd the great
Link to comment
Share on other sites

This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...