Sciencemadness Discussion Board - High Energy Laminated Rocket Propellants

High Energy Laminated Rocket Propellants

kilowatt - 28-10-2007 at 03:05

Please keep in mind this is not meant to be a practical thing for rockets that are supposed to be utilitarian, reliable, or storable. I simply find the idea of pushing propellant chemistry to the limits to get the highest possible specific impulse is fascinating. That is what this is about, at least in the solid fuel department. I am also interested in liquid and hybrid propellants. This mainly applies to smaller highly experimental engines, some even quite small, as high cost or difficulty of synthesis limits the quantities of a lot of this stuff. The construction method I will describe is tedious and some of the propellants are very hazardous materials that demand the utmost respect during synthesis and handling. I'm sure some of these rockets are likely to fail catastrophically. Nonetheless it is an interesting area which not many people have delved into.

I have considered the possibility of some very energetic and reactive solid fuels and oxidizers for rocket engines. Examples of some of these fuels are lithium hydride and other light metal hydrides or borohydrides or light metals themselves such as lithium, sodium, or beryllium, or other things like cubane (actually quite safe/stable), decaborane or mixtures thereof, or mixtures containing hydroxylamine. Some of the possible oxidizers are N2O5 (very volatile) or other nitronium salts, perfluorate or fluorate salts, mixtures containing hydroxylammonium salts, or alkali metal peroxides and superoxides. I have been considering combinations of many of these with each other or with other less exotic propellants.

Clearly many of these propellants are so sensitive and reactive that they could not even come in contact with each other, much less be mixed into a composite propellant. They would simply explode, many as soon as they came into contact. Some of them are quite volatile, subliming solids, and some of them are very pyrophoric and cannot even be handled outside of an inert atmosphere. As a method to allow them to be used anyway, I have proposed laminate propellants.

For core burning or ring burning designs the fuel or oxidizer constituents would be individually cast or grown into solid plates of appropriate thickness with strochiometric mass and a hole in the center for the burn chamber. They could be combined with a suitable fibrous material such as fiberglass or steel wool (where compatible) for strength, or cast or grown as a single crystal plate. The plates of fuel and oxidizer material would then be stacked alternately in the rocket tube throughout its length and glued or mounted in with a thin dividing layer between each. A protective lining would then be applied to the inside of the burn chamber, and a line or layer of flash powder or similar would be applied down its length, bridging all the plates. This would be connected to an electric ignition, and the burn chamber would be sealed with argon gas inside by a cover film over the nozzle. Some of the more volatile propellants would require that the rocket be kept refrigerated until ignition.

The basic equipment needed for building such rockets would include an isolation glove box, possibly refrigerated, casting trays, and most importantly thorough knowledge of the properties and compatibilities of each of the propellant constituents, as well as testing with small samples.

A thickness for the plates would have to be chosen, probably through experimentation, so that the burn rate would be controlled, and yet the burn is even and complete. There could be issues regarding differing melting points of thermal conductivity of the different constituents, and there may be other unexpected issues with the burn rates of the plates.

Suggestions? Criticism? Comments? All welcome.

halogen - 28-10-2007 at 06:07

No such thing as fluorates or perfluorates AFAIK. The rest of it seems like a bad idea too; you're just making complicated pipe-bombs.

vulture - 28-10-2007 at 06:55

Quote:

A protective lining would then be applied to the inside of the burn chamber, and a line or layer of flash powder or similar would be applied down its length, bridging all the plates.

You're crazy. Flash powder in a rocket just turns a rocket into a giant uncontrollable fire cracker.

You want thrust, you need a gradual push. Not mass which turns into gas in two microseconds.

Try building a KClO3/sugar rocket first and see how hard it is to prevent that from simply exploding.

[Edited on 28-10-2007 by vulture]

kilowatt - 28-10-2007 at 07:00

I have seen perfluorates mentioned in various internet sources, albeit scarsely. I guess now that I think about it, it would be odd for fluorine to be in that oxidation state, though. Perhaps those ions are not possible; they are the only candidates I have looked that there is not extensive information on.

Regardless, you seem to have a very pessimistic view on experimental rocketry, halogen. I am interested in whether this propellant arrangement can function to yield high performance. The idea is to come up with something that will not explode, while developing a higher specific impulse than other solid propellants. As I mentioned first thing in my post, I am not trying to come up with a revolutionary new propellant for launch vehicles or anything, since it would be too expensive and dangerous, not to mention I'm just a regular guy without any credentials. I should not actually have to repeat myself there. I am simply bored with the standard solid propellants used in amateur rockets and am looking to find higher impulse onces, for the heck of it, for science. It doesn't have to be viable for space transport, or commercial rockets, or anything else any more that any other amateur rocket does. I assure you these engines will be no more feckless than a typical Estes engine, and FAR less feckless than a typical pipe bomb. These at least have experimental value.

Quote:

Try building a KClO3/sugar rocket first and see how hard it is to prevent that from simply exploding.

I have only worked with powdered metal based propellants before, but they aren't too hard to keep from exploding. I can only assume KClO3/sugar is even easier. Burn rates and chamber pressures can readily be calculated anyway with the most common propellant compositions. I had a little more trouble with Mg/KMnO4 based propellant; I had one engine work well but didn't have a way to measure the thrust, then I had one burn too slowly to register a thrust on my pulley system, then another explode after about one second (it was an end-burner, too

). I think I just didn't have enough binder in that one and it developed cracks. I successfully fired an aerospike ring burning engine with Mg/KNO3, but had far too much oxidizer as the epoxy binder didn't work out quite stochiometrically as I expected it too. That one was just buried in a hillside for firing the first firing, but that engine is reuseable. I need to rig up a sensor to record thrust dynamically.

[Edited on 28-10-2007 by kilowatt]

vulture - 28-10-2007 at 07:08

Yes, but anything you propose is either more hazardous (using alkali metals for example) or technically more complicated (compartimentation of oxidizer/fuel) than which is used in advanced space rockets.

There's a limit to maximum rocket fuel performance where you simply cross into explosion.

If you want a crazy idea, here's one I just came up with:

Try dissolving KMnO4 and naphtalene in acetone and allow it to evaporate. Burn and watch. Warning: likely very hazardous.

Quote:

I can only assume KClO3/sugar is even easier. Burn rates and chamber pressures can readily be calculated anyway with the most common propellant compositions. I had a little more trouble with Mg/KMnO4 based propellant; I had one engine work well but didn't have a way to measure the thrust, then I had one burn too slowly to register a thrust on my pulley system, then another explode after about one second (it was an end-burner, too

You're kidding right? My Mg/KMnO4 explodes in quantities of more than half a gram when unconfined! Either way your Mg is of lousy quality or you're not mixing it properly. Same goes for KClO3/sugar. Dry and intimately mixed KClO3/sugar with some Fe2O3 will blow up when using the slightest confinement. Trust me, I've tried.

[Edited on 28-10-2007 by vulture]

kilowatt - 28-10-2007 at 07:19

What are you getting at?

KMnO4 can never make a decent rocket propellant anyway as its byproducts are too heavy. Nonetheless I have experimented with it. KMnO4/glycerine is fun enough if you just want something to burn.

Quote:

Either way your Mg is of lousy quality or you're not mixing it properly.

It was perfectly good magnesium, but very not-finely-divided. It was packed tight, but had large grain size. Of course high performance was not reached because the grains were too big to burn completely in the chamber. You can see that by the disproportionately bright exhaust. http://www.chrisf.4hv.org/projects/rockets/test1.avi My laminated propellant proposal simply takes large grains like that to the next level, while making sure they remain in the chamber.

[Edited on 28-10-2007 by kilowatt]

vulture - 28-10-2007 at 07:27

Quote:

My laminated propellant proposal simply takes large grains like that to the next level, while making sure they remain in the chamber.

So you're making a heterogenous propellant with large grain size...which benefit do you expect from that?

Say you'd use an alkali metal and actually manage to ignite the "propellant". The blocks would simply melt and sink out the nozzle where they'd burn atmospherically once outside the rocket. That's just one of the many problems with the design.

Why not try it by filling a rocket chamber with naphtalene mothballs and filling up the holes with oxidizer? That's pretty much the approach you're after it seems.

[Edited on 28-10-2007 by vulture]

kilowatt - 28-10-2007 at 07:33

With something like an alkali metal, a fibrous binder would be needed to keep it from running out at once. It could still be a problem though. For that reason the alkali metal hydrides would look more promising. There could be similar issues with any of the lower melting or subliming chemicals. If the fuel and oxidizers could conduct heat or vaporize at a remotely similar rate though, I don't see why it couldn't work. I have considered strongly chilling the rocket before ignition, as long as the burn is brief enough.

Quote:

Why not try it by filling a rocket chamber with naphtalene mothballs and filling up the holes with oxidizer? That's pretty much the approach you're after it seems.

That sort of less organized approach would be more suitable to an end burning design, but end burners subject the chamber walls to the full combustion temperature, which will cause it to melt. For a core burning design something more structured would be nice. Not to mention that cramming some of these highly reactive oxidizers in with a fuel in that manner would be incredibly dangerous/suicidal.

I forgot to mention, the aerospike I mentioned earlier, which also contained a fairly large grain, did not seem to eject any unburned fuel like the earlier Mg/KMnO4 burn. It's only problems were lots of unburned oxidizer, as I got the stochiometry way off, and as such it burned very smokey and too slowly. The burn wasn't very consistent either, because the ring burning design was very hard to pack well (a laminate propellant would solve that, though). Otherwise, fairly decent I guess. I used plenty of binder. http://www.chrisf.4hv.org/projects/rockets/aerospike_1/aero1...

My hope is that with a laminate propellant the grains would also say somewhat well bound. The fuel/oxidizer plates could potentially be made up of bound mixtures as well, giving a higher melting point and lower thermal conductivity. I've considered other arrangements too such as thin coaxial laminates, or pie-shaped divisions that run the whole length (but I think the latter would be a really bad choice for many obvious reasons). The plate laminates seemed the most feasible. They are looking less feasible depending on their thickness, though. I should think thin plates with less tendency to run out or erode unevenly would be best, with an equally increased level of tedium in assembly.

[Edited on 28-10-2007 by kilowatt]

hinz - 28-10-2007 at 08:39

Learn some basics of rocketry first, if your Mg/KMnO4 propellant won't explode, you would melt your rocket case down at the temperatures Mg burns, and the MgO produced will stay inside your molten case or sinter on the parts of the nozzle, where the pressure is decreased (the bell shaped end). The nozzle would be tortured by liquid Mn and the trust wouldn't be good as most of the producs of the reaction (MgO) won't leave the nozzle, only the K2O and the liquid Mn would leave it and generate trust.

There is a reason why Werner von Braun has invented the liquid propellant rockets, because those designs you make won't work as no material will hold up the temperatures involved without beeing cooled.
With liquid propellants you can cool the nozzle with propellant and cheaper and easy handable propellants like kerosene/LOX can be choosen without decrease in reaction enthalphy and thus trust.
If you want to mess around with metall hydrides (your last crazy idea), fist look at their properties you you don't blow yourself up in a clowd of hydrogen (because your propellant got sligtly wet) as you ignite the fuze. (supposed you even get some metall hydrides)

If you still wan't to play with rockets, start with low tech KNO3/sugar,
here are some good pages for you:
http://www.jamesyawn.com/index.htm
http://www.nakka-rocketry.net/index.html (look at the rocket theory)

kilowatt - 28-10-2007 at 09:43

I discounted KMnO4 as a rocket oxidizer long ago, due mainly to its high exhaust mass and poor burn characteristics, and due to my past experiments which I mentioned. I have also discounted end burning designs. No new info here. Also note that in a core burning design the case does not see the combustion temperatures until burnout, and that even the flame temperature of the most mundane propellants exceeds the melting point of most if not all materials. That is why we use ablative nozzles like graphite or clay, and why real solid rockets like the Shuttle SRB, Patriot missiles, and large amateur rockets all use a core burning design, usually shaped so that the burn area remains constant.

I am familiar with liquid rockets, their advantages, as well as their complexities. I am just as interested in them as solid ones. I intend to build one someday using a pressure fed pump http://www.flometrics.com/rockets/rocket_pump/pump-animation... and a regeneratively cooled aerospike nozzle. I don't really have the time now but it's already on my to-do list. My main draw toward the aerospike nozzle is that it is easier to construct with a graphite spike without access to fancy lathes and machine tools, even though it is more difficult to obtain a proper expansion ratio especially for a static test. I also have a larger solid fueled aerospike in the works, which will use Al/NH4NO3 composite propellant. I want to become more familiar with their design as not only are they easy to put together, but they compensate to some degree for change in ambient pressure as they climb.

I am familiar with the properties of alkali metal hydrides and borohydrides as well as their synthesis, and I'm not sure why you assume I would not be before considering their use.

I am already familiar with Nakka's page. http://www.nakka-rocketry.net/index.html

I simply wish to experiment with alternative solid fuels. I am not simply some uninformed newbie whose first instinct is to come up with rash ideas. You have all brought up interesting points, but there is nothing in basic rocket theory that says a laminated propellant design or high energy propellants is outlandish. It is not too different from the equally exotic liquid propellants tested in the 1950s by the US government, the main difference being that you can easily control the flow rate in a liquid rocket, while in a solid rocket you have to make use of burn geometry and the like.

[Edited on 28-10-2007 by kilowatt]

Eclectic - 28-10-2007 at 11:07

Your experiments with making lithium metal and some of the other experiments in your project pages would likely help establish credentials...

Twospoons - 28-10-2007 at 13:18

Chemical considerations aside, a better way to isolate hypergolic propellant components might be to pelletise the lower volume component, coat it with a compatible isolation barrier, then mix the pellets with the other component in the grain. Sort of like flammable concrete. I would imagine such a composite structure would be stronger than laminating, with better control of burn characteristics, less risk of fracture (with resulting catastrophic burn surface increase). It would also be a damn sight easier to build.

franklyn - 28-10-2007 at 13:39

A propellant used for rocket propulsion is inherently very much less efficient
thermodynamically than the same amount of that propellant used inside of a
gun barrel , where explosive deflagration couples nicely with the constrained
expansion of the gas produced. The rate of acceleration of a missile is
determined of course by the pressure acting on it from the gas produced.
The pressure produced is directly the result of the quantity of gas and to a
lessor extent the temperature. Optimally for a rocket , this thrust is designed
to just marginally exceed the takeoff weight by a small percentage , and
ideally the rate of burn progressively becomes less as does the weight. For
the best efficient use of the available energy it must be burned slowly. The
duration this is sustainable is determined by the rate which the propellant is
consumed not how energetic it is , which only affects the dimensions of the
vehicle size for a fixed payload. Better to have a large cheap rocket than a
small expensive one.
Remember that the Saturn 5 that boosted the moon explorers into orbit was
fueled by liquid oxygen and keroene , not all that sexy. Solid motors are just
as bland , a mix of resinous fuel binding the oxidizer. The most energetic
propellant schemes are used solely by military missiles for reduced size and
portability. The legendary Titan II was fueled with IRFNA ( Inhibited Red
Fuming Nitric Acid ) and UDMH ( Unsymetrical Dimethyl Hydrazine ) a hypergol
which self igniting when blended. A reason this surpassed the performance of
cryogenic fuel schemes is that the cold fuels have that much less latent heat
than a fuel at ambient temperature and this must be made up from the energy
provided by burning. In effect cold fuels are handicapped , one reason less
enegetic solid fuels compare favorablty. There are further considerations as to
the layout of a vehicle. The X-15 rocket plane was fueld with liquid oxygen and
ammonia because these are consumed at rates which maintain the same level
trim and center of mass distribution within the plane. Interestingly there is more
hydrogen in a gallon of gasoline than there is in a gallon of liquid hydrogen ,
due to the relative densities , so the tank can be smaller and therefore lighter
and does not additionally require refrigeration. Current research for more
energetic fuels looks to strained ring hydrocarbon fuels such as cyclopropane
and unsaturated alkenes or even alkynes and boranes. Energetic oxidizers tend
to be explosive posing a safety threat. Solid nitryl perchlorate can be made from
NO2, ClO2, and O3 gases: 2 NO2 + 2 ClO2 + 2 O3 => 2 NO2ClO4 + O2

.

APCP - 28-10-2007 at 14:59

Quote:

Originally posted by kilowatt
I also have a larger solid fueled aerospike in the works, which will use Al/NH4NO3 composite propellant.

[Edited on 28-10-2007 by kilowatt]

ANCP chuffs when using Al. Unless you can get some cenes, you'll want to use Mg instead of Al.

Be would be your best bet for high performance metal.

You start reaching the upper limits of solids Isp when you use HNF/GAP. Expensive as hell, hard to get, hard to make....

Still, good luck on any experimentation. Get some diagrams for your aerospike designs made up, I am intrigued. My team plans on using an aerospike on an R motor for a space shot. Probably won't because they are pain, but one varient of the motor has an aerospike.

Eclectic - 28-10-2007 at 18:38

Has anyone tested LiBH4 as a high energy fuel additive?

kilowatt - 28-10-2007 at 19:27

Quote:

Chemical considerations aside, a better way to isolate hypergolic propellant components might be to pelletise the lower volume component, coat it with a compatible isolation barrier, then mix the pellets with the other component in the grain. Sort of like flammable concrete. I would imagine such a composite structure would be stronger than laminating, with better control of burn characteristics, less risk of fracture (with resulting catastrophic burn surface increase). It would also be a damn sight easier to build.

Interesting. I would be extremely worried about what would happen if that isolation barrier were to mechanically break down during loading though. I wouldn't want to be anywhere near it. Until I have a safe way to work with it in that way, it's just too risky. Just one little scratch you know...

Quote:

Your experiments with making lithium metal and some of the other experiments in your project pages would likely help establish credentials...

Not really, so far my every attempt at alkali metals has failed.

Of course not many people have done better (congrats to those who have), but that is no excuse. I have my fingers crossed for my new mini cell which I have finally decided to first fire up with eutectic LiCl/KCl. My most successful chemistry projects so far are my distillation rig and my scrap lead refining process (which I have yet to implement at large scale). Most of my most successful projects have been electrical, such as my reconnection guns.

Quote:

ANCP chuffs when using Al. Unless you can get some cenes, you'll want to use Mg instead of Al.

Be would be your best bet for high performance metal.

Interesting note. Mg is no problem, I have quite a bit, it's just more expensive than Al. I made an atomizer for magnesium that uses molten magnesium in a steel bottle, pressurized with argon to force it through an orifice which is electrically charged so the droplets repel each other. I have not operated it yet, but it will spray the metal droplets into an argon purged trap filled with xylene, which will have an oppositely charged plate at the bottom. Beryllium would be nice, but it's incredibly expensive, not to mention the exhaust would be highly toxic, as well as the fuel itself during handling. On top of that it's very high melting and difficult to work. Still, I have considered its use for some very very small upper stage engines, since you can buy Be powder by the gram cheaper than you can buy any other form of the metal.

Quote:

Get some diagrams for your aerospike designs made up, I am intrigued.

I've already got them. Check http://www.chrisf.4hv.org/projects/rockets/aerospike_mkII/
The case and end cap are made of regular 6061 aluminum with a good burst pressure safety margin even at elevated temperature, and I would like to use titanium for the central core, which will be cooled in flight by air flowing through the entire length of the tube from a hole in the nose cone and coming out the end of the spike, simulating an infinite spike length. Obviously the case temperature must not be allowed to exceed 300°C or so where the strength reduction is just over 50%. I plan to re-temper it to T-6 after each firing. Some finite element analysis would be wonderful to aid in shaping the spike appropriately, perhaps you know a bit about that?

Here's the small Mg/KNO3 aerospike I tested before, as well as the crudded up results from the far-too-lean propellant composition. This rocket was designed and built as a static test engine and not the slightest effort was made to use lightweight materials which would be flyable.
http://www.chrisf.4hv.org/projects/rockets/HPIM1251.JPG
http://www.chrisf.4hv.org/projects/rockets/aerospike_1/

And here is a cutaway my proposed liquid aerospike design.
http://www.chrisf.4hv.org/concepts/mini_aerospike.jpg
http://www.chrisf.4hv.org/concepts/aerospike_rocket.jpg
You can ignore the teflon piston pumps though as I have since discovered the much simpler, lighter, and more elegant pressure fed pump design that I linked before.

Quote:

Has anyone tested LiBH4 as a high energy fuel additive?

I would certainly like too, give its higher energy and hydrogen content. Are you talking about solid borohydride (thats definitely an area for my laminate propellant thing, being one of the fuels I proposed for it) or a liquid fuel that contains it in solution? THF is a good solvent for it, as well as a rather strained compound.

[Edited on 28-10-2007 by kilowatt]

froot - 29-10-2007 at 03:34

The risk of failure of the divisions between the various components of the propellant cake and the potential consequences simply outweigh the benefits. Some of those additives you proposed are rather scary in a confined tube, nevermind together with reactive oxidisers in the same tube.
In your particular design, have you considered arranging the divisions vertically? This would obviously mean that it would burn progressively up the chamber. I can appreciate the innovative approach, but please test your concepts with mild fuel components first. If something goes wrong, we'd like you to report your findings to us and you'll need at least one finger to type it in

I would say that the next step forward with rocketry would be re-useable motors with variable nozzles that can be throttled, extinguished, and re-ignited using fuels generating 'eco-friendly' exhaust gases.

vulture - 29-10-2007 at 06:29

You know, using metal hydrides isn't THAT crazy, just don't use them in combination with oxidizers. Just using them as a controllable source of H2 which is then burned eliminates the need for pressurized H2 gas.

The only problem is where to get the oxygen from.

Also, if you have acces to perchlorates, you might want to try and make lithiumperchlorate. It's a good oxidizer with a VERY high oxygen content. Just awfully hygroscopic IIRC.

[Edited on 29-10-2007 by vulture]

Eclectic - 29-10-2007 at 06:40

There is a report on Dann's site that lithium perchlorate is completely soluble in epoxy. There is some question as to whether the resulting fuel would be prone to high order detonation.

I was thinking of solid LiBH4 powder as a replacement for aluminum in a solid propellant grain.

kilowatt - 29-10-2007 at 08:30

Lithium perchlorate might be a good one, would definitely have to be sealed though. I've made lithium nitrate before, it too is extremely hygroscopic. I'm pretty sure that sample is sitting around in my room somewhere in aqueous solution which it picked up from the air. Good oxidizer when dry though.

Quote:

I was thinking of solid LiBH4 powder as a replacement for aluminum in a solid propellant grain.

Holy shit. I'm thinking that would tend to explode...

Quote:

The only problem is where to get the oxygen from.

Hybrid propellant, with borohydride decomposition happening in a separate chamber connected to the burn chamber via injectors, most likely.

Antwain - 29-10-2007 at 09:08

Just a caution- even though you don't have Be. I know (or knew, he died but maybe not because of this) a guy who had made himself sick from chronic Be exposure. He used to repair antique watches, and had to file down Be springs. He had a kind of permanent pneumonia and was always coughing. Apparently it can give you cancer too and possibly screws with your bones if it is absorbed (which the metal probably can't be).

Hey, if you were feeling particularly suicidal you could arrange a hypergolic fuel based on 100% H2O2 and LiH. low exhaust weights

kilowatt - 29-10-2007 at 14:29

Yeah, that sounds like beryllium poisoning

, I don't think you have to inhale much (doesn't matter what form, metal, oxide, etc) to get chronic symptoms. Childsplay compared to boranes though, specifically pentaborane (liquid) or pentaborane (solid). That shit is evil, I would definitely not want to be exposed. They are high impulse though.

There is a roundabout chemical synthesis for pentaborane but as far as I know decaborane would have to be made with hydrolysis of either diborane or pentaborane, giving low yields. I think that's a ways off for me.

The highest impulse chemical rocket propellant known and tested is F2 + Li/H2 liquid tripropellant. Isp was 542, meaning it obviously didn't blow up. They even considered using FLOX, a mixture of F2 and O2 on the Saturn V, but obviously decided against it because of corrosion, cost, and the logistics of pumping out huge amounts of HF into the air.

[Edited on 29-10-2007 by kilowatt]

franklyn - 31-10-2007 at 04:35

The most energetic binary components which come to mind would be
LiH + HF -> LiF + H2 , variations of this comprised of solids would be
NH4F + NaNH2 -> NaF + N2 + 3H2
2 : 5 , molar expansion

and I've posted this before elswhere , Bifluoride and Hypochlorite
2 NH4F.HF + 2 Ca(ClO)2 -> 2 CaF2 + 4 H2O + 2 HCl + N2
4 : 9 , molar expansion

Hydrazine Fluoride and Chlorite
2 H2NNH2.HF + 2 Mg(ClO2)2 -> MgF2 + 4 H2O + 2HCl + 2N2
4 : 9 , molar expansion

Somewhat more exotic is Methyl Hydrazine Fluoride salt
CH3HNNH2.HF + KClO4 -> KF + CO + 3 H2O + HCl + N2
2 : 7 , molar expansion

Then there is borane compounding
2 NH4F.HF + NaBH4 -> NaF + BF3 + N2 + 7H2
3 : 10 , molar expansion 70 % Hydrogen by volume , 9.2% by weight

4 H2NNH2.BH3 + 6 NH4F.HF -> 4 BF3 + 7N2 + 29H2
10 : 40 , molar expansion 72.5 % Hydrogen by volume , 11 % by weight

These materials are more readily available
2 CaH2 + 2 NH4F.HF -> 2 CaF2 + N2 + 6 H2
4 : 9 , molar expansion 67 % Hydrogen by volume , 10.2 % by weight

CaH2 cannisters - density 1.70 gm/cm³ , melts at 675º C
http://www.fairradio.com/catalog.php?mode=search&query=M...

NH4F.HF - density 1.51 gm/cm³ , melts at 124º C with decomposition
generally available 96% technical grade
http://store.hvchemical.com/browse.cfm/4,1061.htm
http://www.gfschemicals.com/chemicals/gfschem-1134.asp
http://www.baddley.com/S/FL165.htm
Call for quote
http://www.fluoridearc.com/pages/fluoridesac.html
http://www.kyantec.com/catalog.htm

_______________________________

A way to enhance thrust with hydrogen exhaust is to use an augmentor
a device which acts somewhat like an aspirator. This may even work better
with the aerospike nozzle.
See - http://www.aardvark.co.nz/pjet/augmentors.shtml
http://gltrs.grc.nasa.gov/reports/2006/TM-2006-214224.pdf

.

[Edited on 31-10-2007 by franklyn]

kilowatt - 31-10-2007 at 06:23

The air breathing augmenter is neat. With an aerospike nozzle, I can see the augmenter burning the hydrogen rich exhaust in air up to a certain altitude, where the augmenter could be ejected and the mode of operation would then become a non-airbreathing rocket.

Calcium is a little heavy; lithium hydride would be much preferred to calcium hydride, and lithium borohydride has an even greater hydrogen content. I am surprised that ammonium bifluoride is available for purchase so easily, interesting links.

Eclectic - 31-10-2007 at 16:01

Pentaborane Rocket Fuel: Safe handling and storage

franklyn - 31-10-2007 at 23:16

Low density and pyrophoricity apart from the expense militates against its use,
but the ultimate hydrogen gas propulsion reaction would use straight liquified
Diborane in a hybrid arrangement having the Diborane tank over the Bifluoride
matrix combustion cavity.

2 B2H6 + 6 NH4F.HF -> 4 BF3 + 3 N2 + 21 H2
2 : 7, molar expansion 75 % Hydrogen by volume , 10.3 % by weight

Due to the very low melting temperature of Bifluoride 124º C ts hard to see how this
would remain solid for very long despite ablation from surface burning. It could
more easily be used premelted in lquid phase. As I pointed out before in my other
post above in this thread, " cryogenic fuel schemes have that much less latent
heat than a fuel at ambient temperature and this must be made up from the
energy provided by burning. " As a melt , heat energy is added to the system.

______________________________________

I had posted this on a similar scheme here

http://www.sciencemadness.org/talk/viewthread.php?tid=8678&a...
http://www.sciencemadness.org/talk/viewthread.php?tid=8678&a...

_____________________________________

U P D A T E

The density of NaBH4 is barely more than water only 1.07 and it melts at just under body
temperature at 36º C. The shortcomings of using this as a solid are much more pronounced
than for NH4F.HF. It does however compact a large quantity of Hydrogen gas, its chief merit.
It can be readily melted and used in a liquid form. This has the advantages of increasing the
latent energy of the system, simplifying the layout, affording throttle-ability, safe storage
without risk of spills ( the fuel components are then solid ) and unlike many other energetic
chemicals these cannot explode by themselves.

2 NH4F.HF + NaBH4 -> NaF + BF3 + N2 + 7H2
3 : 10 , molar expansion 70 % Hydrogen by volume , 9.2% by weight

A combustible exhaust makes the the rocket plane concept a better approach than direct
verticle lift, since this applies the concept of the inclined plane to aeronautics. Supplemented
by combustion with air, the thrust can be varied so there is little initial consumption of fuel
from takeoff until a high altitude is reached, and then the full propulsion can be engaged to
acheive trans-atmospheric altitudes.

Discovered in 1943 by H.C. Brown, one of boron chemistry's Nobel prizewinners, and
H.I. Schlesinger, Sodium Tetrahydroborate ( NaBH4 ) proved to have strong possibilities
as a missile propellant. By far the world's leading commercial producer of NaBH4 is
Morton International Inc. Long famous for table salt, Morton is also a major manufacturer
of specialty chemicals. The process involves reacting Boric acid with Methanol to produce
Tri-Methyl Borate ( B(CH3O)3 ) which is then reacted with Sodium Hydride at elevated
temperatures. This yields Sodium Borohydride and Sodium Hydroxide together. It is soluble
in Methanol and also Water at 550 gm / Liter , decomposing slowly unless the solution is
basic, which is why it is contained with lye.
See this video of Tri-Methyl Borate - http://exploscience.com/Home/Green Fire Light.wmv

Powerpoint presentation
http://gcep.stanford.edu/pdfs/hydrogen_workshop/Wu.pdf

Pricey
http://www.usbweb.com/category.asp?special=&cat=bio&...
http://store.hvchemical.com/search.htm?step=2&viewfrom=1...
http://www.gfschemicals.com/chemicals/gfschem-A7158.asp

[Edited on 6-11-2007 by franklyn]

kilowatt - 1-11-2007 at 00:15

Quote:

cryogenic fuel schemes have that much less latent
heat than a fuel at ambient temperature and this must be made up from the energy provided by burning.

It doesn't all have to come from the burning. That is what regenerative cooling, running the propellant through pipes or cavities in the nozzle and chamber, is for. The propellant becomes a warmer supercritical fluid while the nozzle and chamber are cooled. Remember cryogenic LOX is one of the most successful liquid oxidizers, while cryogenic liquid hydrogen is one of the highest impulse liquid fuels, despite its great bulk and low density.

Diborane too would be a chilled fuel, with its critical temperature of 16.6°C, though it would be more practical (in terms of vapor pressure) to store it in a pressurized dewar at like -35°C. I think it would work just fine despite its low density, much like liquid hydrogen works just fine. Diborane is relatively easy to synthesize too (from NaBH4 or NaH), but it's definitely hard to handle. It can be made from BF3 and NaH or NaBH4, or by acidifying or halogenating NaBH4.

The video you linked doesn't work.

Bandwidth Limit Exceeded. I thought the borohydride synthesis yielded borohydride and methoxide (or ethoxide, if you used triethylborate) though, not hydroxide.
B(OCH3)3 + 4NaH --> NaBH4 + 3NaOCH3
Only after addition to water would this react to form sodium hydroxide, but sodium borohydride reacts with water. Wikipedia describes recrystallization in diglyme as an appropriate method for isolating the borohydride.

[Edited on 1-11-2007 by kilowatt]

franklyn - 1-11-2007 at 09:17

One hand washes the other so to speak, quenching the laval nozzle allows a
lighter engine that won't melt, a cryogenic fluid however introduces material
problems due to thermal shock. Few alloys can withstand that differential. A
hot fluid imposes less of a constraint on the metal properties.

I know side reactions in the formation of NaBH4 are more complex , I don't have
a description of the proces.

An alternative :
3 NaBH4 + AlCl3 -> 3 NaCl + Al(BH4)3 , Aluminum Borohydride is not stable and
breaks down into an uncoordinated eutectic Al(BH4)3 -> AlH3 + 3BH3

Renewed interest in AlH3
http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=A441121&Locat...

.

Whole lotta shakin goin on

franklyn - 4-11-2007 at 10:21

I archived this a few years back, I had considered using Hydrogen rich exhaust
from a hypergol propellant for fuel to power a compound rocket turbine engine.
The idea was that a turbo-supercharger could be simply modified so that the
propellant will spin the turbine and the exhaust can be further combusted with
the air from the compressor. The fuel would need to be liquid to be throttled
and cheap and available limiting any exotic component to a minimum. I settled
on 8 parts Ammonium Nitrate in solution in one part water at the boiling point
as the oxidizer and because it is also Hydrogen rich. The reducing component
would also need to be liquid and react on contact with the Ammonium Nitrate.
The criteria of Hydrogen rich and pyrophoric is satisfied by Diborane , limiting it
to a minimum 12.9 % weight of the total by solvating it with Ethylene Diamine
also very Hydrogen rich , H2N-CH2-CH2-NH2 : B2H6 . Only the Boron and Carbon
consume available oxygen the exhaust is 2/3 Hydrogen by volume 9.9% by weight.
Carbon Monoxide increases the combustable volume by 12.5% for a total 78.7 %

. . . . . . . . . . . . . . . . . . . . . Ratio of moles of reactants -> . 1 0 2 .:. 5 1 2 . -> to moles of products . . . . . . . . . . . . . // . . . combusted in air
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . / . . . . . \
3 2 .H2N-CH2-CH2-NH2 : B2H6 .+. 4 5 NH4NO3 .+. 2 5 H2O . => . 3 2 B2O3 .+. 6 4 CO .+.7 7 N2 .+. 3 3 9 H2 . // . 2 0 2 O2 .+ . 8 0 8 N2
. . . . . . . . . . . . . . . . | . . . . . . . . .| . . . . . . . . . . . .| . . . . . . . . . . . | . . . . . . . . . . . . | . . . . . . . . . . | . . . . . . . . | . . . . . . . . . | . . . . . . . . . . . | . . . . . . . . . . |
molar mass . . 1920 . . . . . 883 . . . . . . . . 3600 . . . . . . . 450 . . . . . . . . . .2227 . . . . . .1792 . . . .2156 . . . . . . 678. . . . . . . . 6464 . . . . . 22624

Quote:

I have subsequently revised this to exclude Diborane on the grounds that
it is self igniting and a safety hazard as well as not meeting the cheap and
readily available criteria. A gel of dry Isopropanol and Aluminum containing
Isopropoxide formed first in situ as the ignition source is by far more practical.
http://en.wikipedia.org/wiki/Aluminium_isopropoxide
The alcohol itself provides some oxygen so less Ammonium Nitrate is required.
I'm toying with the idea of a combined Ammonium Nitrate , Ammonium Bifluoride
melt. Apart from Ammonia contained , this same formulation was used for IRFNA
( Inhibited Red Fuming Nitric Acid ) passivated with 0.6 % Hydrogen Fluoride
http://www.astronautix.com/props/nitdudmh.htm

The diagrams below show various schematic and cutaway views of ordinary
turbosuperchargers. The only components are the the exhaust turbine and
compressor impellor mounted at opposite ends of the common shaft , the
central journal houses the full floating bearing , and also mounts the two
rotor housings called volute scrolls. My design excludes the compressor's
housing and envelopes the entire turbo unit instead with a cowling somewhat
like a nacell of a jet engine containing the aspirated air which is directed over
the turbine's housing to mix with the exhaust at that end. Additional air and
thrust bearing is provided by the trailing augmentor section. - Center diagram

An intriguing innovation is this air-bearing which eliminates the need for oiling.
http://www.miti.cc/newsletters/06_oilfree_turbocharger_gas_e...

.

Compound engine.JPG - 94kB

artem - 4-11-2007 at 10:36

Quote:

Originally posted by franklyn
...
2 B2H6 + 6 NH4F.HF -> 4 BF3 + 3 N2 + 21 H2
8 : 28 , molar expansion 75 % Hydrogen by volume , 21.3 % by weight
...

This reaction is slightly endothermic, H~+202kJ

franklyn - 12-11-2007 at 10:13

- artem -
has posted above observing that the " propellant " mix I proposed is in fact
endothermic. We exchanged U2U's over this and he remains steadfast in
his conviction, as I do that his assertion flies in the face of common sense.
( I have subsequently corrected the 21.3 % to 10.3 , which was in error )
The maddening thing about this is that when one does the requisite
assigning of enthalpies ( cited in references ) to the balanced equation
there appears to be a large discrepancy over what the result is.
[ artem ] has given me two different figures , and every time I do the
math ( using cited references ) I get a different result - Grrr.

The equation of the reaction is _ 2 B2H6 + 6 NH4F.HF => 4 BF3 + 3 N2 + 21 H2

B2H6 has a Positive heat of formation , is pyrophoric and spontaneosly
burns in air , inherently acidic NH4F.HF de-oxidizes Aluminum !
It is elementary that acids energetically replace hydrogen from hydrides.
The notion that combined , these will form a cold pack is facetious.

Granted that HF has a high enthalpy to begin with , and so less energy is
available. This is similar to a reactive metal with a chlorocarbon , energy
will be less than if the metal is oxidized with chlorine directly because the
carbon is also being reduced.

2 B(s) + 3 F2(g) -> 2 BF3(g)
. . . . . . . . . . . . . . . . . . . -2272 ( -1136 KJ / mol )

B2H6(liq) + 6 HF(g) -> 2 BF3(g) + 6 H2(g)
+ 41 . . . . . . . . .-1638 . . . -2272 . . . . . . . . . - 675 KJ reaction enthalpy

I have assumed dis-association of 2 NH3 into N2 + 3H2 . Enthalpy of NH3 is
- 46 KJ / mol , so in reverse this is endothermic , but still the molar volume
increaes ( opposite of the Haber process for its formation by Le Chatelier ).
Assuming double the above value -1350 and subtracting the heat value of
the 6 moles of ammonia -276 KJ corresponding to the balanced equation with
Amminium Bifluoride , leaves -1074 KJ which appears a reasonable value.
In my conception NH4F.HF is to be in a liquid phase for use , as I pointed
out in a previous post , the lattice energy and heat of fusion , is thus
added to the enthalpy. BF3 is a gas so the heat associated with the phase
changes to liquid and then solid , remains in the substance itself and for this
reason is not evident in the accounting , this endothermic component is not
expressed in the figures.

The solution otherwise is uncomplicated and straight forward :

http://pages.prodigy.net/anderhan/ch11thermo.pdf
Quote _
" Enthalpy changes for reactions can be obtained by simply subtracting the
heats of formation of the reactants from the heats of formation of
the products. Be sure to multiply the heats of formation by the coefficient
of the compound involved."

Also , arithmetically subtracting a negative is the same as adding a positive.

The big problem is obtaining consistent enthalpy values. There is aparently no
agreement , convention , consensus , consistency or standard as to exactly
what constitutes " standard " values although it may be stated as such.
I don't quibble with the units , that is easily convertable , but the fact that
it may be calculated at absolute zero 0º K or 298º K ( 0º C ) or often
at an arbitrarilly chosen phase without stating so.

For example , given in 0º Kelvin > http://srdata.nist.gov/cccbdb/hf0k.asp

From > http://cobweb.ecn.purdue.edu/~propulsi/propulsion/comb/prope...
( Fiqures are given in calories / gram , this I first multiply by the molar mass
and and again by 4.184 to convert into Kilojoules / mol )
B2H6 is + 354 cal / gm = ( + 40.9 KJ / mol , liquid
NH4F.HF is -3189 cal / gm = ( -760.5 KJ / mol
NH4F is -3000 cal / gm = ( -464.4 KJ / mol
NH3 is -649 cal / gm = ( -46.2 KJ / mol
HF is -3581 cal / gm = ( -299.6 kj / mol , liquid
BF3 is not indicated

From > http://webbook.nist.gov/chemistry/form-ser.html
( substances must be individuallly researched )
B2H6 is + 41 KJ / mol , liquid
NH4F.HF is not indicated
NH4F is not indicated
NH3 is -45.9 KJ / mol
HF is -273.3 kJ / mol
BF3 is -1136 kJ / mol

From > http://www.ualberta.ca/%7Ejplambec/che/data/p00403.htm
B2H6 is not indicated
NH4F.HF is not indicated
NH4F is not indicated
NH3 is -46.1 KJ / mol , gas
HF is -271.1 kJ / mol , gas
BF3 is -1137 kJ / mol , gas

From > http://www.grc.nasa.gov/WWW/CEAWeb/TP-2001-210959-REV1.pdf
B2H6 is + 36.6 KJ / mol , gas
NH4F.HF is not indicated
NH4F is not indicated
NH3 is -45.9 KJ / mol , gas
HF is -273.3 kJ / mol , gas
BF3 is -1136 kJ / mol , gas

From > http://www.update.uu.se/~jolkkonen/pdf/CRC_TD.pdf
STANDARD THERMODYNAMIC PROPERTIES OF CHEMICAL SUBSTANCES
B2H6 is + 36.4 KJ / mol , gas
NH4F.HF is not indicated
NH4F is -464 KJ / mol , crystal
NH3 is -45.9 KJ / mol , gas
HF is -299.8 KJ / mol . liquid <> -273.3 kJ / mol , gas
BF3 is -1136 kJ / mol , gas

From - CRC Handbook of Chemistry & Physics
B2H6 is + 36.4 KJ / mol , gas
NH4F.HF is not indicated
NH4F is -464 KJ / mol , crystal
NH3 is -45.9 KJ / mol , gas
HF is -299.8 KJ / mol . liquid <> -273.3 kJ / mol , gas
BF3 is -1136 kJ / mol , gas

From - Kirk Othmer encylopedia
( substances must be individuallly researched )
B2H6 is + 35.5 KJ / mol , gas
NH4F.HF is -798.3 KJ / mol , crystal
NH4F is -466.9 KJ / mol , crystal
NH3 is -46.2 KJ / mol , gas
HF is -272.5 kJ / mol , gas
BF3 is -1135.6 kJ / mol , gas

Heat of formation values used for NH4F.HF
( The value -464 for NH4F(s) , and -273 for HF(g) are combined , -737 )
B2H6(liq) is + 41 , NH3(g) is -46 and BF3(g) is -1136

2 B2H6(g) + 6 NH4F.HF(l) -> 4 BF3(g) + 3 N2(g) + 21 H2(g)
. .+ 82 . . . . . . . .-4422 . . . . . . . -4544 . . . . . . . . . . . . . . . . . . . - 204 KJ reaction enthalpy

Alternatively _

2 B2H6(g) + 6 NH4F.HF(l) -> 4 BF3(g) + 6 NH3(g) + 12 H2(g)
. .+ 82 . . . . . . . .-4422 . . . . . . .-4544 . . . . . -276 . . . . . . . . . . . .- 480 KJ reaction enthalpy

One way around this provides only an approximate result , and it is not
endothermic. Summing the individual average bond energies of the reactants
and the products > http://www.cem.msu.edu/~reusch/OrgPage/bndenrgy.htm

REACTION _ 2 B2H6 + 6 NH4F.HF -> 4 BF3 + 3 N2 + 21 H2

BOND . . . . .H - B . . . H-N . . . H-F . -> . B-F . . . .N2 . . . .H2
ENERGY . . . 90 . . . . . 93 . . . 135 . .-> .150 . . . 226 . . . 104
COUNT . . . X 12 . . . X 18 . . .X 12 . -> . X 12 . . . X 3 . . .X 21
TOTALS . . .1080 . . 1674 . . 1620 . -> .1800 . . 678 . . 2184

- 288 KJ reaction enthalpy

Well there you have it every way I calculate it from worst case it comes up
exothermic. What latent heat might be present in NH4F.HF , is the variable.

________________________________________________________

Diborane was considered in the 1950's as a fuel but never deployed.
This may not be a practical propellant due to the errosive nature of HF,
teflon lined non-metal fittings would be needed at least. It is in keeping
with this thread in exploring beyond the current art.
http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=30
NOTE you must copy this URL and paste into the address bar

Most energetic reaction ?
http://www.math.temple.edu/~wds/homepage/chem.records
Here is research with OF2 as an oxidizer for Diborane
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/1970000...
Turbojet combustion of Diborane
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/1993008...

.

artem - 13-11-2007 at 00:40

Quote:

Originally posted by franklyn
...Heat of formation values used for NH4F.HF
( The value -464 for NH4F(s) , and -273 for HF(g) are combined , -737 )
...Well there you have it every way I calculate it from worst case it comes up exothermic. What latent heat might be present in NH4F.HF , is the variable.

Well, franklyn

1)NH4HF2(s) H0=-804KJ/mole(Chem.Encyclopedia)
(it is solid - Tm=+126.45C)
your mistake is "combining" without the enthalpy of
sublimation HF -36.4KJ at 292.7K) and
reaction HF(l)+NH4F(s)=>NH4HF2(s), H~-28KJ/mole
Another figures for NH4HF2 (-798 KJ, for example) are possible, but the the difference is negligible.
(figure -760.5 for NH4HF2 may be wrong, such internet sources often contain mistakes)
2)the reaction B2H6+NH4HF2 may be exothermic:
0.5B2H6(g)+3NH4HF2(s)=>NH4BF4(s)+2NH4F(s)+3H2+~295KJ
2.5B2H6(g)+3NH4HF2(s)=>3BN(s)+2BF3(g)+15H2+~704KJ
and so on...
but it is BAD PROPELLANT anyway, it is suitable only as H2-source.
3)NF4HF2 is more suitable for propellant

franklyn - 18-11-2007 at 02:44

LA-2341 - The performance of boron explosives

Available from the First CD of the Los Alamos monograph collection

This 1959 study of mixtures of Boranes with various Fluorocarbons showed that
even in reducing carbon performance is only slightly inferior to TNT. Notably Boranes
were also mixed and exploded with only Hydrazine and that is not even considered to
be an oxidizer yet obtained again performance slightly less than that of TNT yielding
Boron Nitride and Hydrogen.

.

artem - 18-11-2007 at 10:01

Quote:

Originally posted by franklyn
This 1959 study of mixtures of Boranes with various Fluorocarbons showed that even in reducing carbon performance is only slightly inferior to TNT...

.

Theory gives 5.9MJ/kg for teflon+B5H9,B10H14 (and ~110% blast effect vs TNT)
See also US Patent 5487798 - using mixtures of NH4N3+B,Ti,TiH2.

DubaiAmateurRocketry - 29-5-2013 at 23:36

Quote: Originally posted by hinz

Learn some basics of rocketry first, if your Mg/KMnO4 propellant won't explode, you would melt your rocket case down at the temperatures Mg burns, and the MgO produced will stay inside your molten case or sinter on the parts of the nozzle, where the pressure is decreased (the bell shaped end). The nozzle would be tortured by liquid Mn and the trust wouldn't be good as most of the producs of the reaction (MgO) won't leave the nozzle, only the K2O and the liquid Mn would leave it and generate trust.

There is a reason why Werner von Braun has invented the liquid propellant rockets, because those designs you make won't work as no material will hold up the temperatures involved without beeing cooled.
With liquid propellants you can cool the nozzle with propellant and cheaper and easy handable propellants like kerosene/LOX can be choosen without decrease in reaction enthalphy and thus trust.
If you want to mess around with metall hydrides (your last crazy idea), fist look at their properties you you don't blow yourself up in a clowd of hydrogen (because your propellant got sligtly wet) as you ignite the fuze. (supposed you even get some metall hydrides)

If you still wan't to play with rockets, start with low tech KNO3/sugar,
here are some good pages for you:
http://www.jamesyawn.com/index.htm
http://www.nakka-rocketry.net/index.html (look at the rocket theory)

Liquid Mn and K2O does not generage thrust.

Quote: Originally posted by APCP

Quote:

Originally posted by kilowatt
I also have a larger solid fueled aerospike in the works, which will use Al/NH4NO3 composite propellant.

[Edited on 28-10-2007 by kilowatt]

Use Magnesium for nitrates, aluminum for perchlorates.

Magnesium boils easily and react fast, aluminum boils 2600 which a nitrated propellant unlikely to reach, so al will react at its molten stage which is not stable so it chuffs.
___________

and all those other comments are very nice, Lithium boro hydride might be the might hydride to use but its really unsafe,

the most practical might come to Magnesium hydride.

Or a composite propellant with dissolve oxidizier in a binder that releases flourine mixed with magnesium powder or hydride, magnesium burns really hot with flourine, and for hottest chemistry reaction ever is lithium + flourine which combust at around 5000 degree.

hyfalcon - 30-5-2013 at 17:19

What material would be able to withstand that kind of thermal shock and still not fail? Diamond?!