Real Fuel for Real Life!

[Shadow Wolf56]

Hello everybody!

My name is @Shadow Wolf56 (duh) and I have a question to present to you!!!

What are some ideas for rocket fuel in real life? I know that potassium nitrate And sugar is available, but other fuels!(idk everything from vinegar+baking soda to ethanol+liquid oxygen). come up with anything! maybe if you have heaps of info about your suggestion, maybe you know where to buy it! Feel free to post your ideas/suggestions and maybe I can even (one day) test them... 

Edited July 28, 2017 by Shadow Wolf56

[Bill Phil]

Gasoline and LOX. It's what Goddard used for his first rocket, if I recall.

[Scotius]

Pepsi + Mentos

[Streetwind]

15 minutes ago, Shadow Wolf56 said:

I know that potassium nitrate is available

That's an oxidizer, not a fuel  It's usually paired with sugar, and the resulting propellant mixture is called "rocket candy". Great starter for hobbyists.

Something else that homebrew rocketeers occasionally dabble in is hybrid motors. A solid rubber liner burns with nitrous oxide gas being injected at the top. In case casting rubber is too much effort, you can simply use an acrylic tube - it will burn with NOx, too.

Edited July 28, 2017 by Streetwind

[sevenperforce]

1 hour ago, Streetwind said:

That's an oxidizer, not a fuel  It's usually paired with sugar, and the resulting propellant mixture is called "rocket candy". Great starter for hobbyists.

Something else that homebrew rocketeers occasionally dabble in is hybrid motors. A solid rubber liner burns with nitrous oxide gas being injected at the top. In case casting rubber is too much effort, you can simply use an acrylic tube - it will burn with NOx, too.

Though you usually need to scrape out the inside of the acrylic tube to give it more surface area.

If you want a super-cheap demonstrator, you can purchase 3% hydrogen peroxide, put it in a bottle, place a spoonful of yeast in a balloon, stretch the balloon over the top of the bottle, and lift the balloon so the yeast falls in. Shake. The yeast will catalyze the decomposition of the peroxide, causing it to release gaseous oxygen and fill the balloon. Then you've got a balloon full of pressurized GOX you can use as your oxidizer for your hybrid rocket.

[K^2]

2 hours ago, Scotius said:

Pepsi + Mentos

If only CO₂ was just a little more soluble.... A bottle rocket with constant 5 bar would have I_SP of up to 100s. That's seriously not bad for something you can build at home. Unfortunately, not enough gas dissolves in water at 5 bar to sustain the pressure, not to mention all the gas you'd be losing in "exhaust". So if you wanted to build a good bottle rocket, you still want to fill it with air and water, with the air that's already there doing most of the work. But carbonation would improve the efficiency of a bottle rocket by a notable margin.

If anybody wants to try a menthos/cola assisted bottle rocket and compare it to plain air/water, I'd be curious to see the results.

[Shadow Wolf56]

Hybrid rocket motors? What's the fuel?(I have heard of them but what the heck are they?)

EDIT:wait, just give me a billion years to work this out*starts googling*

Edited July 28, 2017 by Shadow Wolf56

[sevenperforce]

17 minutes ago, Shadow Wolf56 said:

Hybrid rocket motors? What's the fuel?(I have heard of them but what the heck are they?)

EDIT:wait, just give me a billion years to work this out*starts googling*

Hybrids use a vapor oxidizer burning against the surface of a solid fuel. (The reverse is possible, but rare.) Common fuels include paraffin wax, rubber, and a few others (I propose napalm); common oxidizers include LOX, GOX, HTP, and NOX. They can be throttled and sometimes even restarted by adjusting oxidizer flow, but they have high thrust and benign failure modes.

[Shadow Wolf56]

yeah I have been watching this awesome vid...

they use pvc pipe as fuel and nitrous oxide as oxidiser! (In the start)

Edited July 29, 2017 by Shadow Wolf56

[Shadow Wolf56]

also, can compressed oxygen be used as an oxidiser?

[Zeiss Ikon]

22 hours ago, Shadow Wolf56 said:

also, can compressed oxygen be used as an oxidiser?

Yes, but it won't produce a flight-weight engine/tank system.  The weight of a compressed oxygen bottle, to hold anywhere from 150-330 bar, is too great relative to the mass of oxygen it contains to give reasonable system performance.  Nitrous oxide compresses to a liquid at a mere 35-ish bar, so a smaller, thinner tank will hold more usable oxygen.  High test peroxide is a liquid at ambient pressure and temperature, and decomposes exothermically, eliminating the need for an igniter.  Otherwise, liquid oxygen is the way to go if oxygen is your choice -- it's reasonably dense, doesn't require a high tank pressure, and is an excellent oxidizer from an energy standpoint; plus, it's less hazardous to handle than high test peroxide, and not much more so than nitrous oxide.

[Shadow Wolf56]

ok! so are you saying that compressed oxygen is not the most efficient way to go?

Also how to get NOX and LOX @Zeiss Ikon?

Edited July 29, 2017 by Shadow Wolf56

[Casualnaut]

Orphan tears is what secretly fuels every mission.

[sevenperforce]

3 hours ago, Shadow Wolf56 said:

ok! so are you saying that compressed oxygen is not the most efficient way to go?

Also how to get NOX and LOX @Zeiss Ikon?

NOX is easy, LOX isn't.

[Shpaget]

6 hours ago, Shadow Wolf56 said:

 

Also how to get NOX and LOX

Go to a car tuning shop. NOX is the thing they use extensively in Fast and Furious. They call it Nitrous, NOS, etc. Comes in pretty blue bottles.

Medical suppliers also have it. They call it laughing gas. They probably won't sell you.

6 hours ago, Shadow Wolf56 said:

Aaah can get rid of this quote!!

[DerekL1963]

On 7/29/2017 at 7:46 PM, sevenperforce said:

NOX is easy, LOX isn't.

o.0  At least in the US, it's pretty straightforward, rocketeers do it routinely. - call Praxair or Airproducts and arrange for a delivery.  You'll need an appropriately certified dewar and handling system/staff, which is non-trivial but doable.  From everything I've read on various rocketry lists, the biggest problem is the smallest commercial delivery if frequently far larger than the hobbyist or amauter can use.

[Streetwind]

I guess that just means that the average hobbyist should add...

*sunglasses*

MOAR BOOSTERS! 

[wumpus]

On 7/31/2017 at 2:02 AM, DerekL1963 said:

o.0  At least in the US, it's pretty straightforward, rocketeers do it routinely. - call Praxair or Airproducts and arrange for a delivery.  You'll need an appropriately certified dewar and handling system/staff, which is non-trivial but doable.  From everything I've read on various rocketry lists, the biggest problem is the smallest commercial delivery if frequently far larger than the hobbyist or amauter can use.

That's odd.  I've heard that LOX is a favorite industrial explosive.  Mix LOX with charcoal and you have a great explosive.  What makes it popular is that if your detonator are duds, all you have to do is wait for the LOX to evaporate and you then have a dud detonator+charcoal.  Still not ideal, but better than a dud sitting on your high explosive.

I'd hate to think that all such uses are larger "than the hobbyist or amature can use".

Finally, I wouldn't describe N₂O as "NOX".  Liquid N₂ is sometimes used for RCS (possibly in the astronauts RCS backpack), and might be used for other things (probably involving cooling cryogenics on the ground).  Even "NOS" would probably be better, as that would likely be written on the bottle (one easy source for hobbyists are car modification companies).  The N₂O will be liquid in a bottle to be released as a gas, and will also include additives to avoid any drug use (and related police oversight) issues.

[Zeiss Ikon]

As noted above.  High Test Peroxide is much harder to obtain than LOX, which is less practical in amateur quantities than nitrous oxide.

Another oxidizer that was used a lot back in the 1950s and 1960s, largely because it's hypergolic with some fuels, is nitric acid.  Liquid at ambient pressure/temperature, and in anhydrous form it's about 3/4 available oxygen by mass (and something like 10% denser than water).  There are handling issues, but in general, I'd rather deal with fuming nictric acid on a flight line than 95% peroxide (I'd rather work with LOX than either one).  You can use nitric acid as an oxidizer with almost any fuel, but the main reason to put up with its tendency to literally eat its way through tanks and pipes is that nearly any hydrazine derivative is hypergolic with some variant of nitric acid (white fuming, which is the anhydrous, pure HNO₃, or red fuming, which is white fuming plus as much N₂O₄ as will dissolve).

Modern rockets have almost entirely replaced nitric acid with pure N₂O₄ compressed to liquid, because it's hypergolic with some hydrazine derivatives (unsymmetrical dimethyl hydrazine and monomethyl hydrazine are most commonly used) it doesn't eat plumbing as badly and if you have a leak, while highly toxic, it will evaporate instantly instead of sitting on the tarmac waiting for enough energy to come along to ignite the asphalt.  Nitric acid, N₂O₄, and peroxide are all considered "storable", because they don't boil off at room temperature.  Nitrous oxide is sort of storable, too, since it won't go anywhere if you have a tank strong enough to keep it liquid.  This is why liquid fueled ICBMs (including the Titan II that also launched Gemini) mostly used some variant of nitric acid and hydrazine, or nitric acid and kerosene (jet fuel, called paraffin in British usage) plus a "starting slug" of a hydrazine variant preloaded into the fuel line to get things started.

BTW, liquid oxygen forms a high explosive mixture with anything that combines combustible and porous.  Yes, that includes asphalt (a LOX spill on an airport tarmac is a bomb-squad emergency, though if you can keep it from going boom for a while the LOX evaporates off).  The early attempts at motors for the A-4 (what everyone by Germany called the V-2) resulted in dropping high explosive alcohol/oxygen jelly on the launch pad several times, when ignition failed to ignite -- at least, once, it actually went off.

[cantab]

Nuclear bombs

[Confused Scientist]

Lasers! Seriously!

Ah, but you fuels, and technically, lasers aren't reaction mass.

Sublimating ice! Butterflies flapping their wings in Asia! An airplane on a treadmill! A flashlight shining on a solar panel! An ice cream flavor no one likes! Potatoes!

Or, you could try: Hydrogen and methane! It's what all the cool kids are doing these days! I'd say it's mainstream, except then it would- paradoxically- not be mainstream.

[ChainiaC]

9 hours ago, Confused Scientist said:

Or, you could try: Hydrogen and methane! It's what all the cool kids are doing these days! I'd say it's mainstream, except then it would- paradoxically- not be mainstream.

Well I ain't no rocket scientist nor a chemist, but I recon you'll get some pretty lousy ISP using that as a bipropellant

[Zeiss Ikon]

4 hours ago, ChainiaC said:

Well I ain't no rocket scientist nor a chemist, but I recon you'll get some pretty lousy ISP using that as a bipropellant

I think those were to be the fuel, with LOX as the oxidizer.  For amateurs, hydrogen and methane are impractical; they have to be too cold to keep them liquid (and pressurized gasses aren't practical due to tank weight).  On an amateur basis, the best combination of safety and performance in liquid fuels is probably kerosene (or diesel fuel) or gasoline, with ethanol/methanol as an alternate for some situations, with either LOX or nitrous as oxidizer.

FWIW, nitrous/alcohol has been used in high power model rockets (yes, Tripoli launches have included liquid bipropellant rockets, at least in the mid-1990s).  The tanks and combustion chamber are one long tube.  A sliding piston pushed by the nitrous pressurizes the alcohol, and a "pyrovalve" (a small chunk of solid propellant initially blocking the injectors) serves to both start propellant flow and ignite the motor.  Yes, you can have a flight-weight liquid biprop motor as small as a couple inches diameter and a couple feet long, including tanks, fuel feed, and thrust chamber.  Don't know if they sold enough of them to stay in production, but I'm pretty confident I could build one from scratch, given time and material resources.

[wumpus]

7 hours ago, Zeiss Ikon said:

FWIW, nitrous/alcohol has been used in high power model rockets (yes, Tripoli launches have included liquid bipropellant rockets, at least in the mid-1990s).  

While I've often thought that would be a good mixture, I've never heard it had very good Isp (LOX+vodka*) is very near LOX+RP1 in Isp, but with vastly lower temperatures.  Googling around, I saw a NASA paper (at least on a NASA site) that showed that N₂O+propane would make a great preasure fed rocket.
https://tfaws.nasa.gov/TFAWS06/Proceedings/Aerothermal-Propulsion/Papers/TFAWS06-1026_Paper_Herdy.pdf

[Zeiss Ikon]

We used to discuss nitrous/ethane for self-pressurized systems on the model rocket newgroup as far back as the early '90s (I'm sure they were examined by actual rocket scientists further back than that), and I recall reading that ethylene was thermodynamically similar but with higher energy due to the strain in the double bond.  IMO, either one would be a preferred replacement for propane (in that there's no need to use oxidizer to pressurize the fuel).  Those propellants weren't taken seriously in the '50s and '60s because of tank weight, but modern composite tanks can contain 800+ psi vapor pressure at reasonable weight, hence give useful mass ratios.

As noted in the article, where this system shines is as a storable, self-igniting bipropellant system.  Not technically hypergolic, but all that's needed is a little electric power (a couple hundred watts for a few seconds, seemingly) to heat the catalyst to get a start.  The ability to use the oxidizer as a monopropellant saves stage weight, possibly enough to offset the required batteries.

BTW, this article indicates nitrous-isopropanol is good for 233 s -- not top of the line for liquid bipropellant, but if self-pressurized and self-igniting, the system mass savings on pumps and igniters (not to mention cost savings on things you don't have to design or build) might make the whole-stage performance a win.  Nitrous-ethylene might do better (ethylene has a near-zero energy of decomposition due to the double bond, so you get more energy per mole than any alcohol).