Episode 32: Jet Pack

Air Date: June 9, 2005

A Jet pack can be built from plans purchased off the internet and limited funds.

busted

The jetpack produced by the Mythbusters was not powerful enough to even lift itself off the ground, and they had to cheat by going beyond their assigned budget, in order to create it. The sum of its parts cost too much to allow the average person to build it on a budget and the plans did not have enough details to give builders a clear example of what to build.

"Pyramid power" can be harnessed for a variety of purposes around the home.

busted

The build team constructed a series of pyramid frames using the precise measurements and dimensions required to "harness" pyramid power. Four tests were performed: keeping razor blades sharp, preventing food from spoiling (one test for milk, another for an apple), and preventing the decay of a flower. The apple test at first seemed to be working, however it was later discovered that a contaminated saw blade (used to halve the apple) may have given one half a higher microbial load than the other. A repeated test using sterile equipment yielded approximately the same decay rate for each half. Strangely, a similar test with ‘cube power’ showed the fruit rotting at a faster rate than the other two tests.

This myth caused Adam to comment, "No more ‘oogie-boogie’ myths, please." (The MythBusters don’t normally deal with paranormal myths.)

37 Comments

  1. A Fan says:

    On the Jetpack episode you use lawn blowers not jets on your back or something like that…like the jetpacks in movies.

  2. Ali says:

    I am not sure whether all the power of the engine was actually getting to the propellors. I think that much of the power was being absorbed by the belt which is use to transfer power from the engine to the propellors. It would have been better to place two smaller, streamlined shaped engine directly beneath the propellors to ensure minimum wastage.

    • Kurt Breitenfeldt says:

      yes and no, 2 engines under or over the props would have restricted air movement, and would have added more weight to creat the same power. belts are light and power efficient, more so then any other option i can think of. also you need the engine on your back to act as a weight along with your legs, that should help to keep you upright. i don’t think that it should have been extended down as far as they had it due to the fact that you will indeed have your legs under you provided you do have legs. the only thing i would have tried to do differently is adjust the pully system so give the props more rotation and increase thrust. also i would have tried using a 4 blade prop over the 2 blade prob provided the engine had enough power to turn it. in the episode the engine seemed to be turning at max rpm’s but did they really use all the power that the engine was capible of putting out? that is my question. i find that on the show the Mythbusters team does not always look at every variable. maybe they just don’t always see EVERYTHING at all angles as i’m sure it’s hard to do, but if they’re lookin for a new member for the team, i would like to try out for it! lol

  3. Edward says:

    The duct fans built did not produce but half the lift expected. Did they think to change the pully sizes on the engine or ducts to increase the speed of the duct fans? If there was power to spare from the engine I would think they should have made the fans sping faster. i.e. more lift.

    • Kurt Breitenfeldt says:

      wish i would have read your post, i looked at that angle too! but i also had the thought to use a different prop

  4. michael says:

    If you dont wast your time with plans fans and ducts you can build a jet pack from model airplane jet engines, but four engines at 6,000 a pop put a dent in anyones budget.I have played with the idea. and would be glad to give you my insight.

    • Kurt Breitenfeldt says:

      i don’t think model engines will produce the power for the thrust needed for vertical lift of a 200lb person + equipment.

  5. Darren says:

    Personally i think it can work, but if they treated it like a small helicopter, as one person said with lift probs, and i think with the implementation of a jet turbine, of reasonable size to provide enough power to turn the blades and for the exhaust to provide additional thrust it may work. or even for the exhaust to run into something like a car turbocharger which will in turn provide more air for the turbine equalling more power to the blades. thats my two cents.

  6. george says:

    theproblem with the jet pack experiment was they tested the rig in an enclosed space.
    this let the air circulate instead of disperse so you eventually get a motor boat in a drainign toilet effect. the boat makes headway against the swirling water but appears to be standing still.

    even hoverjets like the harrier were first tested over special runways with screens and vents below the jet blast so the air wouldn’t simply recirculate.= through the engines but would actually be pushed away from the plane through the underground vents so the plane could lift off.

    they should take the jetpack outside and put it on top of a hanging crane thern try it so all the air blast goes downward and has little chance of recirculating around and back into the ducted propellor intake.

    even heliciopters must guard against creating the situation of recirculating airflow. with them it is called settleing into flow when they come down so fast they settle into their own prop wash and the helicopter is simply recirculating a donuts of air in the vicinity of the helicopter blade disc instead of displacing air. the helicopter loses lift and crashed.
    this was the cause of the first Osprey marine vehicle crashes.

  7. jordan says:

    i saw the james bond episode super cool

  8. Rick says:

    the jet pack one was boring.

  9. Robin Dudley says:

    I think your plans for the ‘jetpack’ were flawed from the start, the gear ratio’s were the wrong way round, you had the small cog on the engine shaft and the large cogs on the fans, this effectively reduced the fan rpm to at least half that of the engine!, now if you had had 1:1 ration (same size cogs for engine and fans) then you would have doubled what you had on the show (thrust that is), also if you had reversed the cogs, large on the engine and small on the fans, you would probably have quadroupled the rpm available!! so would you give it another go, seems a shame to waste such a good bit of engineering!!!!

    • Kurt Breitenfeldt says:

      the reason for the restriction with the pully system is because few engines can turn something as fast as they turn, even the car you drive doesn’t turn the tires at the same rate as the rpm of the engine, not even in top gear.

  10. caleb says:

    What if you use actual jet engines, or ionization rockets. All you need to have to make an ionization rocket is a television, a cylinder, and two plates which i don’t know what they are made out of.Take the electron gun from inside the television and put it inside the cylinder.At the other end of the cylinder put the two plates there about one and a half inches apart from each other. Drill a whole quite big at the end of the cylinder where the two plates are but don’t drill into the plates them selves. Cut the end of the cylinder. On the side of the cylinder with fan in the whole to suck air into the cylinder. What should happen is the when the electrons combine with the air molecules the get ionized and when they get between the two plates the go zooooooooming through the back, thus giving trust more powerful than any other rocket to date. It’s also more sudden than any other.

    • Kurt Breitenfeldt says:

      i would love to see the plans and parts list for that!!!

  11. caleb says:

    what i meant to say was, “drill a small hole on the side and put a fan in the hole to suck air into the cylinder”.

  12. Jamie's#1fan says:

    i’m trying to do a science project on what you guys did. you are pretty awesome and i was wondering if you guys had any tips for me…

  13. Gabriel says:

    yes could be have a right function may be using a more powerful motor, light weight, may be same to a motorcicle motor and a right guide system i found this http://www.youtube.com/watch?v=vyb6vnX1My0 is a proyect same. but is same a “pinguin helicopter” and baxter low weight (joke) i like to much this chapter

    • Kurt Breitenfeldt says:

      to bulky, i think the guys had the right idea by keeping is small…well sorta. i think the idea is to build something that you could stand up with and support yourself. it’s got to be under 100 lbs for the guys i work with!

  14. KCP says:

    Thanks for doing pyrimid power ’cause I needed a science far project ASAP and it worked out perfect I got first place!!!!!!!!!

  15. Delmer says:

    I love your show. I hope you still have Your “jet pack” I do believe that it can fly. 1) You must first use a propeller, like the one on a WW2 mustang P-51. Not that thick fan. 2) The Pitch of the propeller was too shallow. It should have a deeper pitch. Should add 5 to 10 degree angal or same as the mustang prop. at least. 3) Should add a ring or a band. Like the Mercedis Benz emblem. at about 1/8″thick or less. in the ducks. cut out a slot where the ring would fit in flush and the propeller could flow freely and not loosing air pressure. Allthese changes should make if fly. If it does would like to see it up close and personal.

  16. Delmer says:

    Sorry Didn’t finish my comment. I do have more ideas. But never get the chance to work on any of them. I also have an idea to go green and long distant on this type of flying. Please, I would like a reply. Thank you for your time. Again, I love you show. your fan: Delmer Delmer

  17. bennie dodd says:

    someone did not research enough!!! all pyramid power testing must be done away from all metal structures. they did theirs in a metal building! oops! do not use a metal frame. use wood. place objects 2/3 up from the base. re-visit this one! try honey in a small plastic container(parts cabinet drawer works well)longer tha it is wide. put a control outside pyramid. leave several days. gets thick. control stays normal. they didn’t look before they leaped!! need more info, contact me.

  18. Martin says:

    I tend to agree with bennie dodd but I have some other stuff to say about this “myth”.
    If you’re going to test “pyramid power”, you really should follow the “pyramid power” rules. It’s great that you made a scale model of the great pyramid, but that’s just the start. You then have to align one side of your pyramid to magnetic north using a directioanl compass. You also cannot have your pyramid in the same room as electronic equipment. They don’t get on very well, and your pyramid won’t work. When you’ve done all this, you should then leave the pyramid alone for at least 3 to 4 weeks. It’s a comsic battery and like any battery, it needs time to charge. You also should not bump or knock the pyramid at any time as it’s a very sensitive device. I’m not sure about the metal structures. I don’t recall all the details, but I was dissapointed with the pyramid power episode. I felt you guys didn’t give it a fair shot. You got a couple of half good results and said “busted”. I also think that sometimes you guys keep doing “myths” until you get the results you’re looking for and then say “myth busted”. If you think I’m crazy, please let me know, I’d be interested to hear from you guys.

    Cheers, Martin

  19. tom says:

    The propeller fan jetpack should work in theory but it would cost more money than an average person could afford. An engine that is light enough and powerful enough must be found and even then it should be turbocharged or something to increase the power with little extra weight. A small jet turbine for micro model jets could be used to drive the fans. they are light and powerful, the excess thrust from the engine could be forced downward to get a few extra pounds of thrust.

    As for changing the gearing of the engine and fan it would not work. A small engine doesn’t have the torque to drive the fans – Imagine trying to accelerate in a manual transmission car from a stop in 5th gear or two drive a school bus with a weedwhacker motor. Simply not enough power for the load being put on the engine. It just isn’t possible.

    The cowling could be redesigned to generate more lift perhaps.

    A commercial company could invest and create a personally jetpack and market it for 50k or something. A full scale comany would have the resources to optimize a design like this.

  20. Topher174 says:

    FAIL…

    Check out the blokes in New Zealand that are producing them. What I don’t understand guys, is that they debuted the same thing that you tried to build at Oshkosh at the same time. Only, theirs worked…

  21. Buzz Lightyear says:

    Controlled Indoors Flight of the Martin Jetpack
    http://www.youtube.com/watch?v=2TBndcBjQFM

  22. Jesse says:

    Does anyone know where I can get a pyramid kit for my science fair project?

  23. BSXR says:

    They should def. try the jet pack out again!

  24. Richard says:

    Jet pack again!

  25. matthew says:

    the engine is not strong enough

  26. Charlie says:

    Myth busters came close, here are a few improvements based on research;
    1) The duct provides approx 30% to 40% of the lift, with the fan providing the rest. The ducts leading edge, duct to blade clearance and the exit shape all need careful attention.
    2) Transonic flow (ie speed of air below sonic level)is an important consideration as high rotational speeds does not always give high flows due to disturbed air flow at the tip.
    3) don’t have the air flowing over an obstruction like the motor.
    4)Duct length to diameter looked a little large.
    5) Internal stators to smooth the airflow are required in the duct so air does not separate from the duct wall.
    6) The ratio of the duct exit to the duct inlet throat should be about 10% greater.
    Good luck out there on building one.

  27. whynot says:

    The problem was very simple. The duct design was incorrect, it needed to be longer to allow the airflow to be focused. The comment about the intake needing to be 10% smaller than the exit should have been just the opposite, the exit duct needs to be smaller to basically funnel the air a pressure point, same as a rocket nozzle is funnel shaped. The more turbulent the airflow on exit the better, one wants to build turbulent air pressure right at the exahasut nozzle, thats what generates the lift, with laminar flow the air would not create enough presure on exit.
    The top part of the cowling should be short, from where the fan is, the exit should be longer to allow pressure build-up, the fans create thrust from the pressure buildup within the cowling itself being driven downward – the moving column of air.
    Also, the props used did not appear to have a deep enough pitch based on rotor speed, slower rotor speed required a higher pitch. Jamie was wrong about “no chance if system failure, certain death, fall like a stone”, the solution was ballistically deployed parachute. The extreme vibration is damped by a better engine mount and drive shaft assembly.

  28. what if says:

    What about using 4 propeller systems?

  29. Daniel says:

    Hello,I thinck that you used the wrong engine. You have to youse a engine that uses jet fuel. Jet fuel works better than normal petrol . The proppelar will move faster .

  30. Bob says:

    What about increasing the curved area at the top of the fans, to give a larger surface and shape them more aerodynamically like a “curved” wing? Increasing the air flow over the top surface and over a larger area might give more lift.

  31. Mark says:

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