Engine Hacks: Liquid Fuel Amateur Rocket Roundup

When the idea of an engine hacks theme was being kicked around at Hack a Day, the subject of rocket engines was one of the first to come up. There was a problem though; solid rocket motors are far too common to be interesting, and even hybrid rocket engines are becoming passé. We’ve never seen a liquid-fuel rocket build before, so that’s what this roundup evolved into.

First up is [Robert Watzlavick], who has been has been building liquid fueled engines for the last decade. He started out with an uncooled kerosene/LOX whose death is seen in the title pic for this post. Lately he’s been working on a monster of an engine that is projected to deliver over 1,000 Newtons of thrust. As with many of the early rockets that launched man into space, [Robert] uses kerosene and liquid oxygen for fuel. This man knows his stuff.

Next up is a ‘kit’ liquid fuel rocket, the SS67B-3, that’s based on the German WWII Taifun missile. This engine is about as basic as you can get. There’s one fuel tank that holds both the Hydrogen Peroxide oxidizer and gasoline fuel. Both are blasted into the combustion chamber with pressurized gas. we found a write-up on this kit with some good pictures, but no video.

If high pressures, glowing metal, and huge flames pique your interest, there’s also a fabulous e-book (PDF warning) available that is a reprint of How to Design, Build and Test Small Liquid-Fuel Rocket Engines by [Leroy J. Krzyck]. This book was originally written in 1967, but lathes and mills haven’t changed that much over the past 44 years. Why not give it a go? There’s still plenty of time to complete the build before the 100th anniversary of Goddard’s first flight.

28 thoughts on “Engine Hacks: Liquid Fuel Amateur Rocket Roundup

  1. Liquide fueled rockets are not safe.
    It is as simple as that. If you think they are safe you will die.
    Not to say that people shouldn’t experiment but understand this is really risky and that you will need to take every precaution and even then you could get hurt or killed. If you do not take every precaution you probably will get hurt and or killed and or hurt and kill someone else.

    1. Neither were chemistry sets, or model airplanes. But without stuff like this we end up with a generation of kids that can’t do a damn thing…There is no substitute for hands on.

  2. Note also that this is what got Goddard kicked out of Auburn, Massachusetts and sent him down to Roswell, New Mexico. Now you just go to prison. So much for our culture of research and innovation; replaced with fear and a quest for stability.

    1. Not so much for the rocket experiments themselves, but because he was doing something meaningless for his contemporaries and was asking the universities to fund him.

      They took one look and asked “You want to do what? Shoot a rocket to the moon? Why?”

      The choise of Roswell was more for the remote location as his experiments grew bigger. He would have had to make that decision anyways, because it’s just not safe to handle large quantities of liquid oxygen and fuel near other people.

    2. The problem for the government is that most of the fuels used by hobbyists for rocketry (which are designed to burn rather than explode) are very similar to things that DO explode.

      Black powder for example, the only difference as to whether it burns or explodes is the exact ratio of the ingredients used.

      Also, many of the things that are used by rocketry hobbyists are also used in the manufacture of illegal fireworks (after all, a firework is generally a rocket with something on the end to explode and make a nice light display) and the pursuit of illegal fireworks manufacturers can catch legitimate hobbyists in the same net.

  3. This “hack” is useless for the people out there who do not have a proper license for handling high concentrations of hydrogen peroxide.

    The average concentration of it in those brown bottles in pharmacies is only 3% at most. If you were to try to separate it from water, you can attempt to boil the water away, but you might need a vacuum system to get it to manageable temperatures. If you pay two dollars per bottle, each bottle (totally forgot the actual amount, but is close) you have 20 Milliliters of Hydrogen peroxide, assuming you can get ALL of the water out without wasting any hydrogen peroxide.

    To get any reasonable quantity for experiments would cost you a large sum of money. To get higher concentrations, you cannot (from my experience) use any easy to access chemicals.

    I already asked some companies if they were interested in shipping some to me in reasonable quantities, and here is one response from 2009:


    Dear ******,
    Thank you for your inquiry.
    Unfortunately the cost of shipping is quite expensive when ordering a small quantity like 10 lbs. These 10 lbs would cost about 1000 USD to transport to ***** NY USA. On the other hand if you would order a much bigger quantity, like a pallet with 6 jerrycans each 66 lbs, the transport would still be about 1000 USD. Hardly no increase in transport cost.

    If you still are interested in ordering such a small quantity like 10 lbs we will provide you with an invoice with a fixed binding price, including transport.

    Best regards,
    Erik Bengtsson
    Peroxide Propulsion

    If anyone here has any ideas how to get reasonable amounts of hydrogen peroxide in good concentration, please tell us, because there are people out there who would LOVE to dabble in liquid rocketry.

    1. First off, you can make 50% hydrogen peroxide pretty damn easily.

      Second off, anyone who’s googled anything about rockets knows how dangerous LOX is, you didn’t inform anyone of anythinghy people are on hackaday that refuse to google basics is beyond me

      Third, there are much better propellants to use for amateurs if you’re just experimenting. It’s not even close to out of the question for someone to obtain RP-1(its basically kerosene) and unless you want to go to orbit, you can store o2 in scuba tanks for testing. Methane is easy to obtain as well and storage is comparably easy

      If you’re just testing things these are perfectly fine setups, with the right precautions. Hobbyists do dangerous things, saying “its dangerous, dont ever do it” without any explanation just shows actual hobbyists you have no clue wtf you’re talking about.

      Yes I know this thread is dead but if I found it on Google’s front page than so are a lot of other people, and some of the info in these comments is just straight ignorant

  4. Incorrect. The thing that keeps black powder from “exploding”/burning is burn rate. Which while it can be modified by the proportion of chemicals, can be further modified by the grain size. Anyone who has done extensive solid rocket booster building has atleast heard of a CATO if not witnessed one first hand. These are primarily caused by voids in the fuel grain that exposes more surface area to the flame generating more gas and pressure than the case can handle.

    Regarding hydrogen peroxide it is possible to find 30% at stores, if you know the right ones to look in. Above 50% concentrations and you run into issues with storage and handling. Above 70% and the chance of causeing devastating explosions from minor spills increases with concentration. Never mind the painful consequences if you spill some on your skin much above 30%. There are a number of places that sell plans for hydrogen peroxide stills to purify it to useful concentrations for rocket cars and steam powered rockets that react with a catalytic gauze.

  5. I just want to commend the writing on this post. THIS is the level of polish HAD should strive for. No typos, good punctuation, nice verbiage. Well done. Now bring the rest of your posts up to this level and I’ll have much more respect for this site.

  6. Man, I really can’t describe how badly I want to do this, but I like not being brutally violated by the FAA, ATF, FBI, DHS, and God knows what other agencies even more. :/

  7. Up here in canada you can get h2o2 at hydroponics stores and similar specialized garden stores. It can befound in concentrations over 50%. This is not fun stuff to play with and please keep your moronic friends away. Please becareful.

  8. If it isn’t liquid oxygen as an oxidizer, we’re still talking about toys; RFNA and we’re at least out of the little-boy pants. Granted liquid H₂ as a propellant is something of an ‘extra for experts’ question, but kerosene, alcohol, or gasoline are acceptable.

  9. Above all else an engineering degree from an accredited university is a must. Then an understanding of the limitations of the materials you are going to use for construction and a very real understanding of thermodynamics. Most of the amateurs do not know the difference between a sonic nozzle and a supersonic nozzle. And, the rest do not understand the concept of cooling the supersonic nozzle to prevent the melting and catastrophic destruction of your garage, house, and life.

  10. Believe it or not I had something VERY similar to this back in the early 90’s. My mother got it from a friend at work (who loved their kid) decided it was too dangerous for their teenager to have. I was around 12 at the time.

    It looked really old at the time maybe 60’s vintage. I remember mine came with like 2 or 3 huge books and instructions on using multiple fuel/oxidizer/catalyst combos. There were several where you could pressurize the one tank with an air compressor. You could also use solid fuel booster engines to get it off the ground, it launched from an iron bowl with like a spark plug in the bottom and a long rod coming up out of the center.

    I damn near lost an eye testing out a new fuel mixture, I poured a little bit into an empty vodka bottle on the porch. I struck a match while leaning way away from it dropped it in. The first time the match hit the bottom and went out, so next time I got right over it and looked down in as I inserted it. I still remember the sound and the smell of burnt hair as it put me on my backside! Lol. I burned my hair and eye brow, and melted my eyelashes.

    I’ll never forget the day it the big one either. I had launched it successfully a couple times before. This was my first launch on my own fuel. I climbed about 30 feet struggling the whole way. Then it stopped and went BOOM! It looked just like the end of first Star Wars where the Death star explodes into all those tiny sparkly pieces.

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