Hacked Gadgets Forum

April 16, 2007

Homemade Rocket Motor Test

at 2:27 pm. Filed under Crazy Hacks, Insane Equipment, What Were They Thinking


Who said building and testing rocket motors in your basement is dangerous?

“This is the first static test with our homemade tar/oxygen hybrid rocket motor. James Turner and myself (Eric Stackpole), and two of our friends, Jeff Bernard and Caleb Lesher did this project last summer because we wanted to learn more about how rocket engines work. We built the rocket in James’ garage in Humboldt County, CA completely out of parts we got at the local hardware store. We had previously done a little over 20 tests with polyethylene, but none of them came close to this having much power (note the shaking of the camera when the rocket fires.) The camera did not capture them, but we could clearly see shock diamonds (indicating a supersonic exhaust velocity) running the entire length of the plume. We would have begun working on getting run times longer and perfecting nozzle geometry, but parents made us stop the experiments completely after our first test. There are several even larger rockets we built that we are waiting to be run if we get the chance. Admittedly, we did not know the rocket would be this powerful, and the fist thing we did after this test was build an enclosure with one foot thick walls filled with sand. We’ll post more clips as we develop our rocket program.”



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45 Responses to “Homemade Rocket Motor Test”

  1. Alexander Says:

    Sweet Zombie Jesus!

    I wish they would have hooked it up to a force-gauge in order to see how much thrust they got out of it!

  2. Marty Says:

    Sweet Zombie Jesus indeed! They should be thanking him that they still draw breath, and have all of their bodily appendages. My college advisor lost 4 fingers and his eyesight because of similar inattention to safety precautions. “It’s only fun until somebody gets hurt”.

  3. Ethan Says:

    Damn, i want plans for this

  4. Max Says:

    Yeah, these guys are real rocket scientists.

  5. liesofxiii Says:

    Where are the outtakes where they blow themselves up 😛

  6. Hexypoo Says:

    If there are out takes they would end up on youtube, everything ends up on you tube.

  7. Paul Says:

    This is massive 😀

  8. Marty Says:

    Yeah, as in massively foolish. What part of “shrapnel” is not understood? Google LDRS to see it done right. None of this “holding a pipe bomb in a vise” stupidity. Shop goggles, yeah, right. Go forth and be safe, guys.

  9. Takato Says:

    Once they get them working well enough, they should mount them on an R/C plane.

  10. liesofxiii Says:

    Yeah, this is far from safe, needs a massive warning at the begging of the video 😛

  11. Alan Parekh Says:

    The outtakes would probably include the house burning down…

  12. paul Says:

    I totally agree with Marty – standing beside what’s basically a pipe bomb is just so stupid – a good rocket motor is a narrow balance between a damp squib and a bomb – you find out by blowing a few up – by all means do the experiments, build a better rocket motor – but use some common sense, build a bunker and do it right

  13. Daniel Says:

    Interesting work guys! And, although Paul and Marty are exaggerating by comparing it to a
    pipebomb (both oxydizer and fuel in a sealed container, completely different from their
    rocket), I am glad you have seen the (right kind of) light concerning safety issues.

    Oh, and a simple electronic ignition would also help, just take a car battery, a car ignition
    coil and a spark plug. That way you can light the booster flame from a distance.

    Looking forwards to your upcoming tests!

  14. skazz Says:

    You’d think these were the kinds of kids who’d already be very familiar with fuses; I can’t imagine why anyone volunteered to stand right behind it with a lighter. Not sure I’m looking forward to the outcome of a wooden rocket shield used indoors either.

  15. squarefish06 Says:

    They would achieve a greater specific impulse if they used nitrous oxide instead of oxygen.
    The fears of this type of rocket motor exploding are being overstated, “Spaceship one” built by Burt Rutan used a very similar solid/gaseous bi-propellant design as well.

    This was specifically to avoid the problem that has plagued solid rocket motors since year one:Namely, once you light them they can’t be put out until all the fuel/oxidiser mix has been burnt. As seen on Challenger.

    Tha oxidiser can be stepped down in this design, or turned off completly, this causes the motor to flame out

    I do agree with a remote ignition system though 😉

  16. Derek Anderson Says:

    It is important to note that the burn rate is limited by the oxidizer delivery rate on this kind of motor. This means that there is no chance for a “runaway” reaction that results in detonation. At the same, time, the motor is still dangerous. Without a shield of some sort (a real shield, not plastic woodworking goggles), pressure could build up internally which results in detonation.

    Failure to restrain the motor might be an even more severe threat. Ever seen a welding tank get it’s head knocked off? That rocket might get a lot of velocity before it tears off it’s oxygen supply.

    Overall though, hella cool. My wife says I am not allowed to build one 🙁

  17. Max Says:

    I can just see the explosion when Dad gets the letter from the insurance company that wrote the policy on this house. That’s ex-policy, of course.

  18. Clark Hummell Says:

    SWEEET, this is quite inspiring! (j/k!)

  19. bubba Says:

    what’s with the music and dramatic setup, they say themselves in the video that they are replicating previously described rockets from the internet.

  20. paul Says:

    Sure hybrids are easier to ‘tune’ but you still don’t stand beside them the first time you fire them up (or ever) – I’ve flown nitrous hybrids dozens of times so I do have a little experience – as I said above a rocket motor is a balance between overpressure in the casing (ie boom!) and underpressure (no thrust) – it’s hard to manage, has to match the burn profile of the grain – these guys are burning tar – not the most stable of fuels – all it takes is a big chunk to come loose (surface area bumps up, burn rate goes up) and block the nozzle (pressure spikes until the back pressure on the oxidizer shuts it down)

  21. DIY ROCKET - Homemade Rockets! | zedomax.com - blog about DIYs and Review on reviews of gadgets and technologies... Says:

    […] via […]

  22. ryan Says:

    Man that was awsome i need something like that!!! can i have the plans???

  23. Alan Parekh Says:

    I am not the creator, it is just featured here, click on the Youtube logo (bottom right in the video window) to view the authors video page. Or click this link.

  24. ryan Says:

    Man thats sweeet!!!!! Dude can u send me the plans on how to make One?????

  25. ryan Says:

    man where do you get this stuff????

  26. Ross Says:

    Very impressive work and nice design. As for all the safety concerns people have been voicing… Is it dangerous? Of course, but its far from a pipe bomb. a pipebomb is a confined explosive as someone earlier has stated, and yes, rocket motors are known to cato (Catastrophe At Take Off) but in this deisgn that is EXTREMELY unlikely. Hybrids are some of the safest and most efficient designs around. Since the oxidizer and the fuel are not chemically bound until they are ignited, the only way for this particular rocket to explode would be for the internal pressure to spike. The most likely cause for this would be a fuel that melts too easily (such as the polyethylene they were previously testing which can suddenly create too much surface area) but even in this situation you have a force ( in this case the oxygen) forcing the excess pressure out the nozzle. Someone said fuse??? This isnt exactly the kinda of rocket you light with a fuse buddy, fuses are for solid propellants at best, but shouldnt be used on rockets at all.
    I think we should cut these guys a break, I love doing this sort of stuff, and i typically find that kids that are smart enough to build a more advanced rockets are also aware of the danger around them. They DID notice what they were doing was a little dangerous and immediately too measures to make it safer using what they had available.
    Congrats to you guys for doing a great job, looking forward to seeing your next step!

  27. Conner Says:

    that was great i hope that i can get the chance to try it

  28. ryan Says:

    if the us gov found out about this theyd probably ban them cause somone would turn it into a rpg or something

  29. Adam Says:

    I’m sure the US Government is fully aware of homemade rockets like these…

  30. Jacob Says:

    Very nice…..I hope they see this… http://www.NEFAR.com

  31. David Says:

    So much misinformation…so little time…

    1. They are only creating 5 lbs of thrust. Barely enough to the lift the fuel and tank 10 feet in the air. What I have seen so far is not a rocket motor but a glorified torch. A real hybrid rocket motor looks like this:


    or this:


    2. This kind of testing should NEVER be done inside a residential structure of ANY KIND. Even a garage. This has house fire written all over it.

    3. Ross, REAL hybrid rockets are ignited with IGNITERS which places the rocketeer way way far away from the rocket and not a hand held torch with the user only 2-3 feet away from a possible CATO. It is possible and I have seen a dozen or so launches in person with hybrid rockets ignited in this way. The igniter breaks the seal between the NO2 and the fuel and ignites it all at the same time.

    4. Want to see real hobby rocketry? And do it safely? Check these sites out:


    This stuff in the video is great. It’s reassuring to see young people so enthusiastic about scientific endeavors. However, what they are doing is suicide. They need to be doing this kind of stuff outside and using a remote ignition system with sandbag bunkers around the “motor.”

  32. Ross Says:

    David, I am agreeing with you. A fuse and an igniter are vastly different things and with hybrid rockets I have built I have only ever used an igniter (I’m pretty sure a fuse just wouldn’t work). As for your explanation of a possible CATO, I believe it to be incorrect, let me explain. On almost all hybrid rockets, the actual fuel is not overly flammable in the form before oxidation, therefore if the seal were to break (which I have seen before in a rocket of a friend of mine) the NO2 MAY light and most likely will burn itself out quickly or in a worse case scenario cause the casing and/or nozzle to explode. This is known as engine failure and it is EXTREMELY dangerous, but in no way are you risking that same kind of cato you would get from a liquid, or even solid propellant rocket as there is no mix of the oxidizer and fuel (the oxidizer burning by itself is hardly explosive but could cause enough pressure for an explosion of sorts. Regardless of any of this, we have seen that the nozzle simply flies out when the pressure builds (a nifty, although probably not very reliable, safety mechanism), so as long as someone doesn’t stand behind the nozzle (and if they do, Darwin is in motion) everything should be fine.

    And I agree, this testing really should be done outdoors. I’m giving them the benefit of the doubt that they took many safety precautions and much thought before igniting, and may have limitations for reasons unknown to us.

  33. Eric Stackpole Says:

    Hi all,
    This is Eric from the video. I stumbled upon this site and read your comments. I wanted to clarify that we are doing a lot more to improve safety. The power of the tar rocket was much greater then we had anticipated for that test and all of our work thereafter has been outdoors in a test stand with sand filled walls and with us a good distance away. We’ve also developed some remote ignition systems but we are still working on what design will work the best for our purposes. Since we’ve hosted the videos, there have been more then 50,000 views and it seems like almost as many comments. With so many eyes on us, we want to demonstrate doing everything the right way, but we don’t want to sacrifice innovation and the ability to “just try something”. I suppose this is the dilemma many businesses face. Despite all of the support and advice we’ve gotten, the greatest hurtle has been just getting the guys together. Hopefully we’ll be able to get enough done to post another video soon. As always, we appreciate the encouragement and advice.

  34. bill white Says:

    I won’t waste time with underlining safety issues; I assume you understand them now. However I am very interested if you have continued with the experiments using external sourced Oxygen and tar based propellants for your motors. I want to encourage you to continue! You may be on to something here. I am particularly interested in the remote ignition systems you have tried and/or are using.

  35. tyler Says:

    i was just looking for info on how to build a hybrid rocket and i stumbold on this site. i am doing my science experement on what is the cheepest way to get a craft in space and like you i have bilt a hybrid rocket. i just have one tho. i also have built a 4 stage soled rocket and a 2 stage rocket. i like how you are makeing these out of simpil stuff but i know you get this a lot bee safe i got a 2 degree bern all on my arm because my 4 stage rocket bloo up when i had it in 4 difrent holding units i bilt. and from what it looks like i think you are deeling whith a vary powerfol tar rocket so be safe.

    sorry for my bad gramer i am not so hot in inglish and i am just 14.

  36. deni Says:

    great job! i wise i can create one of those!

  37. angelamnesia Says:

    I’m chinese boy.I like rocket.
    Your works very well!great job!

  38. bj Says:

    lol i thought the bly up the whole room for a second

  39. DOC Says:

    The kids doing this stuff seem pretty bright, I AGREE, WE SHOULD GIVE THEM SOME CREDIT…but…let’s hope they put this knowledge and skill to good work at MIT, CalTech or someplace like that – BEFORE they blow themselves up and lose a finger, hand,eye…… Put your skills to work guys, study engineering and don’t get hurt – oh yeah, use an electronic ignition source for heaven’s sake!! The kid using the propane torch IS gonna get hurt. You’re smart enough to make these motors, plug in anything to electronically ignite these motors, and do it outside…You don’t see NASA or AeroJet testing indoors! STAY SAFE!!!!

    Anyway – good luck guys, keep working and studying, DON’T GET HURT – you seem to have a good team of friends working together!! By the way, there are surgeons out there like me that’ll stitch you up when you get renamed “Stumpy” by your friends when you lose an arm or something if you don’t stop some of the really dangerous stuff you’re doing!! LOL… Don’t get hurt, keep flying safe!! GOOD LUCK….

    And to the STONERS making comments here…get off the dope before you attempt to make a rocket engine, the guy with the “bad gramer in inglish” needs to put down the bong! The guy with the “4 stage soled rocket…2 degree bern…rocket bloo up…deeling whith” – damn! What happened to you, inhaled too many hydrocarbons? Is this attempted population control??? Siblings should not breed! Let’s hope some of these guys don’t replicate! No offense guys but DAMN!

  40. acre Says:

    you idiots have too much time on your hands

  41. storms Says:

    can you use propane as part of the testing stage?
    i have started to make the engine however i cannot find the valve thats get connected to the tank. anyone please help me out!!!!!!

  42. Rob Wilkins Says:

    Great interest in rocketry, however, wouldn’t it make more sense to test outside in a more formal and SAFE test stand? In addition, sensors could be attached for recorded thrust/time data. Also, remote means of ignition would afford greater safety.

  43. squig95 Says:

    Just an idea- why dont you make a valvless pulse jet? Lol. Btw where did you get the tar idea from?
    C ya

  44. xarlock667 Says:

    Try using heated liquid tar injected into the firing tube. That way you have a more controlled even burn and you can control the output better. Using a solid lump of tar may sound great, but after a split second or two it melts and you have liquid fuel being blasted out the rear. Kind of like you had when you used the polyethylene pipe as fuel and it shot out the end and hit your freezer. Flaming tar will burn your damned house down. BEWARE! Heated tar burns like hell, and it will stick to you while it burns you. You cannot wash it off! BE careful, and use it outside. Aside from that, have fun and try not to die!

  45. Aaron Says:

    i’m so gonna build some of these. i’ve got years of experience in model rockets, have friends at the missile defence agency, and dozens of books.
    the only way i’d modify the rockets are with graphite nozzles, because almost nothing will melt graphite. the mythbusters used it in their rockets, and it’s oober easy to put in a lathe.

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