diamonds as a fuel?

[Arugela]

I'm thinking about how to get an engine up to max tempuratures to burn 8:1 ratios of hydrogen lox. What about if you lined it with diamond and used the diamond melting point to be a fuel additive or as fuel itself. Does it combine with hydrogen into a methane like fuel or can it add to the hydrogen burn to increase thrust or isp? What about hydrogen stored in diamond and slowly melted by high tempurature liquid hydrogen fuel ratios.

https://lisbdnet.com/what-is-the-melting-point-of-diamond/

If you build engines directly on a fuel tank that is freezing liquid hydrogen how much could you get it to cool down the engines to get the increased thrust? And could diamond act as an insulator or heat transfer agent if not a fuel additive?

Edited February 5, 2022 by Arugela

[JoeSchmuckatelli]

What element makes up diamond? 

[Admiral Fluffy]

14 minutes ago, JoeSchmuckatelli said:

What element makes up diamond? 

Carbon. You could use that as fuel,

[magnemoe]

2 minutes ago, JoeSchmuckatelli said:

What element makes up diamond? 

Carbon and many RP1 engines uses an sot buildup in the engine to protect it. I could see you using film cooling with something who added an protective layer. 
Diamond does not handle high temperatures well as in that seen in engines, now its has very high thermal conductivity but that does not help in an rocket engine but might be extremely nice for stuff like IR sensors and if the price get down cooling of chips. 

[kerbiloid]

Large amounts of the diamond dioxide can cause the greenhouse effect.

[cubinator]

Diamond/LOx could possibly be used as a hybrid rocket, I don't know how fast the stuff burns. Probably not half as well as LH2. And if you're trying to cool an engine, there is very little that will work better than liquid hydrogen.

[Arugela]

I was hoping it could draw the heat out fast enough as a solid to help get the temperature down. Could you farm artificial diamond in mars atmosphere or earth from co2 and the build with it in a way you could repair the ship in any way. Or is it too much energy? You could have way stations with lots of solar panels and slowly repair and use it as a structural element in a repairable ship.

Might be a bit scifi, but you can build diamond layers on the fly with your spaceship you could then try to manufacture metalic hydrogen or other things if they become viable. It might start making a much more expensive ship possible based on the ability to go between hydrogen and methane fuel types and have very high heat capacity/transferance. I was thinking maybe have a layer of the entire hull of diamond sheating to spread out the heat from the engine. Assuming you could pull it away fast enough. This could let the engines burn higher with hydrogen in a combined cooling system. Maybe diamond heat piping filled with hydrogen? Sealed so you don't have to add more hydrogen or use it from your fuel source and to drop the mass of the heat piping to lower the density of the diamond.

I didn't know if it could also be used to melt slowly as a layer of the engine to add carbon to a purer hydrogen burn if it helps. I'm not sure if that lowers or raises isp and thrust.

What would happen if you soaked diamond in liquid hydrogen until it melted and then use it as a fuel additive for an afterburner? Or maybe treat the diamond for extra heating abilities?

https://www.sciencedaily.com/releases/2021/12/211216145928.htm

If you are going to use it to deal with hydrogen anyway. A space ship that can manufacture itself would be ultimately useful in the long run. If diamond is a good building material or part of some processes.

At which point focusing on materials that can be grown at a way station and all work together might be a good goal. If you are likely using carbon fiber anyway. Carbon and hydrogen and oxygen at this point. If you could funnily use either as an oxidizer replacement for deep space or something. Could it help reduce the need of oxidizer at all in if it's more dense or added into a fuel mix? maybe with some more exotic fuel combos if a ship could be made to use multiple fuels?

https://www.quora.com/How-come-a-combustion-product-CO2-can-be-also-an-oxidizer-especially-for-rocket-propulsion

Lots of oxidizer with your carbon on mars and then custom make fuels to need. If the fuel density is good far a part of a journey change the fuel types for a target mission with one ship.

7 hours ago, kerbiloid said:

Large amounts of the diamond dioxide can cause the greenhouse effect.

Terraform mars? Bring trees in a dome and start growing outwards? what can diamond dioxide do in fuels? Or is it good for manufacturing. I couldn't find anything specific on it.

https://science.anu.edu.au/news-events/news/tiny-diamond-invention-could-help-launch-rockets-space

A flying fabrication station. Or a cargo ship with enough transport to carry one to the target and use it.

https://communities.acs.org/t5/Ask-An-ACS-Chemist/Burning-diamond-and-graphite-in-liquid-oxygen/td-p/6098

If you make stuff magnetic maybe it can be used where you want liquids to move. Like a heat pipe or parts of an engine or to carry it? Not sure on the downsides of such materials. Maybe as a way to carry fuels. One idea I was fond of in general was using permanent magnets in structure. if the fuel can be carried this might help with some types of fuel transfers. Unless that is not needed or problematic. Maybe between tanks?

there was also something I was reading about it turning to carbon dust before turning to liquid. If it takes high temperatures maybe it could  collected while making oxidizer on mars and burned as a fuel additive in a hotter than normal hydrogen engine. Or used with a methane mix. Or something more interesting. I'm not familiar with fuel types.

Edited February 6, 2022 by Arugela

[Shpaget]

But why diamond? Why not graphite which has the same amount of carbon per kg as diamond, but is much easier to machine and is somewhat cheaper.

Why do you think diamond is a good material for this purpose?

Edited February 6, 2022 by Shpaget

[kerbiloid]

Because Lucy in The Sky With Diamonds sounds much better than Lucy in The Sky With Graphite.

[K^2]

8 hours ago, cubinator said:

Diamond/LOx could possibly be used as a hybrid rocket, I don't know how fast the stuff burns. Probably not half as well as LH2. And if you're trying to cool an engine, there is very little that will work better than liquid hydrogen.

Diamond/LOx hybrid will actually work great. Diamond burns wonderfully in pure oxygen. The rate of burn might be a bit low, but that's easy to overcome with scale by building a much bigger engine with intricate chamber geometry.

The I_SP won't be amazing, actually a little worse than kerlox, but it can be comparable to solid boosters. All in all, not a terrible rocket.

Shockingly impractical and expensive, sure, but other than that.

[JoeSchmuckatelli]

Well in that case - let's just use coal. 

Steampunk 

Also:

https://www.livescience.com/64487-steam-powered-spaceship.html

[Arugela]

7 hours ago, Shpaget said:

But why diamond? Why not graphite which has the same amount of carbon per kg as diamond, but is much easier to machine and is somewhat cheaper.

Why do you think diamond is a good material for this purpose?

By diamond I mean any carbon based material. No specific reason. I just thought it might be good for something. Plus there was some stuff on liquid diamond. And I thought it would be easier to store in a simplistic way. Or also use as a structural material. I was trying to get a ship design based entirely on the same fuel elements for repair ability and fuel use. In this case I was hoping it was a good heat transfer agent to get heat way from the engines hot spot or transfer in cold from a cryogenic chamber. Trying to get fuel usage up to heats above 6:1 for hydrogen basically. And things you might be able to use with it.

I was also trying to find materials that get rid of problems with hydrogen embrittlement. Or something repairable or farmable. I thought something non metal might be easier. Or part of a solution. maybe treated diamond?

Edited February 6, 2022 by Arugela

[Johnmo89]

One of your arguments is that diamonds burn "cleanly" (let's not forget that CO 2 is also a pollutant). Burning natural gas only emits CO 2 and H 2 O, so it is a much better alternative when pollution is considered.