This site is not affiliated with the Discovery Channel or MythBusters. Please visit the Official MythBusters site for official content.

Episode 32: Jetpack, Pyramid power

  • You build a jet pack from plans on the Internet: mythbusted
  • Egyptian pyramids incorporate a sacred geometry that helps perserve the mummies: mythbusted

Jetpack

Myth: Can you build a jet pack from plans on the Internet

A fun, grand, ambitious build for Jamie and Adam: building a jetpack.

Jamie and Adam were given $10K and one month to see if they could build a jet pack from plans off the Internet. They purchased plans off the Internet for under $100 that weren't for an actual 'jet' pack, but instead a 60hp gas engine hooked up to two propellers with cowlings that can purportedly carry a 200lb pilot. According to Jamie's calculations, the plans could theoretically work, though they don't know of anyone that has actually successfully built the pack in the plans. Also, plans were vague, so there would have to be some improvisation.

Jamie and Adam visited Nino Amareno, who was listed as a "Rocket Pack expert." Jamie gleefully strapped himself into Amareno's rocket pack, though they didn't show him actually flying with the pack. Adam: "I've never seen Jamie so happy in my life."

History

The first attempts to bulid modern rocket pack started in the 1950s. The breakthrough came in 1961 with a military-funded project by Wendell Moore of Bell Aerosystems, the "Bell Rocket Belt." It could fly up to 60ft and up to 60mph, but the military pulled the plug because it was too noisy. The show neglected to mention that another big flaw was that it could only fly for 20 seconds.

For some later attempts at jetpacks, they talked to North E. West at the Hiller Aviation Museum in San Carlos, CA. West showed them the Hiller Platform, which was the earliest ducted fan design that lifted a man. The design took a $0.5M to build and placed the pilot on top of a single ducted fan.

The also looked at a Solotrek XFV, which is similar in design to their own backpack. The XFV prototype they saw never flew, but it's successors did. After seven years of development costing $10M, the XFV took it's on November 2003 was the maiden flight -- it barely lifted off the ground.

The final design they look at was the Moller Skycar in Davis, CA. Moller has spent $200M on the design and believes that nearly everyone will have a skycar in the future. The Skycar is billed as "the first and only feasible, personally affordable, personal vertical takeoff and landing (VTOL) vehicle the world has ever seen."

Picking up parts

Backpack: Jamie and Adam visted the junkyard visit to pickup some alumninum and iron to build the pack. They both lusted after a large block of aluminum (Jamie: "It just like gets me all worked up just looking at it")

Engine: They visited California Power Systems to pick up the engine, first searching for the Rotax 503 dual carb that the plans specified. The owner suggested that they go with a Rotax 583 instead, which is lighter and more powerful. They bought the 583 but eventually switched it for another, unnamed, lighter, similarly powerful engine.

NOTE: I can't find official Rotax 583 specs, this is the closest I can find: * R&D's 583 Rotax * Rotax 582 specs

The Build

Jamie: "This is exactly the kind of project that motivates me personally, so I'm going to be losing some sleep on this one."

Ducted fans: Adam worked on the cowlings, building them out of stacked roofing foam that he then shaped on a lathe and coated with carbon fiber strips. There needed to be a 1/16" clearance between the propellers and the cowlings to generate the proper thrust.

Backpack: Jamie worked on the structure for the backpack, elongating the plan's design so that and lowered the engine could balance the pilot more properly.

Other build components: * Propellers from a hovercraft manufacturer * Vanes mounted below the propellers * Reinforcement struts added to support the ducted fans * Armrests * Joystick * Throttle control

Adam's first prediction: * 5% chance that someone flies * 80% hell of a racket * 15% of horrible, horrible disaster

Test Flight

FAA came to classify the backpack as an ultralight so that Jamie and Adam can do an unregulated test flight.

Adam has lowered his prediction to 2% that it's a viable flying machine.

Buster Test Runs * Adam: "The first official flying test of the WIDOWMAKER!" * First run: Jamie's moustache blew upwards, and there was lots of noise, but it did not make it off the ground. Jamie believed that the fuel mix was wrong because the engine wasn't reaching its powerband, so they made some adjustments. * Second run: Engine reached the "butter zone," but Buster made it only an inch or two off the ground.

Adam believes it's a weight issue, but Jamie believes it's a thrust issue as the design is supposed to generate 500 lbs of thrust. They compromise for the next test run: Buster is removed to lower the weight and a layer of balsa is added to the inside of the cowling to reduce the gap between it and the propeller.

The final test runs: * No Buster: Still no go. Jamie: "If it was correctly balanced, it would be flying, without anything on it, but not with a whole lotta excess." * With Jamie as pilot: "It feels like I'm sitting on top of a drag racer."

Jamie: "Well, the main thing that it feels like I'm in some kind of mixer."

The backpack is nowhere close to flying. Their opinion is that the average joe could not possibly take those plans and be successful.

busted

Pyramid power

Myth: This is a silly myth based on Ancient Egypt. The myth is that the Egyptian pyramids incorporate a sacred geometry that helps perserve the mummies. This same geometry can keep fruit fresh or razor blades sharp

The build team interviewed Jerry Tomlinson, Pyramid Freak Expert, who offered no real helpful advice.

They purchased a $38 magical pyramid as a reference for the precise dimensions, as they only thing they had gleaned from Tomlinson was that the shape was the most important aspect.

For the test each item was placed 1/3 of the way up in the pyramid to match the location of burial chambers in Egyptian pyramids. A control item was placed outside of the pyramid. The pyramids were also aligned to the north.

  • Rose: Both dried out similarly
  • Apple: Pyramid apple rotted much less. However, Tory cut it with a dirty chop saw, so they ran the test once more with properly sterlized apples. They also added a cube in the second test and ran it for four months. No visible difference.
  • Milk: Milk in both was pretty nasty with milk maggots.
  • Razors 1: Kari dulled two razor blades and put one under the pyramid. They were identical under the electron microscope (2500x magnification).
  • Razors 2: Tory shaved with two razors, one for each side of the face. One of the razors was aligned with magnetic north and placed in the pyramid. Tory then shaved with both razors 16 days later. Both razors nicked him pretty good. Tory: "I would have to say that this part of the myth is totally busted." Kari: "I think your face is busted."

Adam: "can we not do anymore of these oogy boogy myths?"

busted

Comments

hai my name is martijn and i'm emailing from holland en i would realy want to know where jou got those plans becease i kant find them aniwhere
I would realy apriciate the effort for sending something back because my father and I are going to trai end built one of oure own so any help would be apriciaitet
thanks for al the efford sow far
the best regarts martijn

http://www.futurehorizons.net/jetpack.htm

It still runs ads for lightsabres, ray guns and the like in Popular Electronics and maybe Servo as well.

I have a fun myth for the guys to test. is it possible to get your eye sucked out of your head by a 3 liter soda bottle by decompression.

Ok, the day when i say this episode it got me thinking that the way you could get more thrust out of the motors would have been to make the bottom of the propelloer holder more pointed like a nuclear smoke stack. I was just wondering if you try this agin to see if it would fly

hey guys this is just a note to say that your used the wrong blades on your hover back pack you used thrust props when you should have used lift fans big big big difference thrust props are shaped to push a lifted body and a lifting fan is shaped to simplely lift a body (thrust prop has 2,3,4 blades and a lift fan has 5-9 blades) thanks for your time in this.....Dave

I think you put the moter to far low down that caused it with more wiant

You can find a copy of those plans for free here: http://www.timwylie.com/jetpack.html

I hope dave gillespie is right I bought the plans from horizon and will do it Dave's way since Myth busters way did not work.
Cross your fingers and don't tell my wife!!! Thanks Dave

should the material of the walls/frame make a difference? copper..? minerals flecked through sand[stones] conducting currents (solar e, heat exchange, radiated photovolactic transferance, static exchange-wind friction..what would happen if they were struck by lightning? gold..resonators? what energy is it focusing?

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.
kwc

Turbo Charging that little motor will increase it's torque output aswell as HP, in turn allowing you to change the sprocket/gear diameters for a faster prop speed, and then greater thrust. Also, Prop changes as stated above.. P>S. I bet if I was on it (150lb man) verses Jamie (probable more than 150lb's) it would lift.

I think one of the bigger problems with lift-off was "settling under power" it is a well known hazard to helicopter flight that if you are in a space which causes the airflow to circulate and re-enter the fans from the top, you will lose an enormous amount of lift. All propellers need "fresh undisturbed air" to create the most lift. By being inside they created the situation which was worst for these fans.

If you ever have an opportunity to watch a fully loaded helicopter take off you will see the first thing they do once they break free of the ground is to start forward. This prevent the air from circulating around and re-entering from the top. They get an immediate boost in lift by doing this. Had the "Widow Maker" simply been outside, it would have produced much more lift and since it was almost ready to lift inside it probably would have flown. If they had been outside and with just a bit of a breeze to interupt the recirculation of air it WOULD have produced excess lift and flown. Stability and airworthiness are separate issues.

The pyramid razor thing started out as one of Martin Gardner's little jokes in Scientific American - I don't think he ever expected anyone to take it seriously!