Aerodopers- Could a man make a flying platform with these small turbine engines?

Factual Questions
1

Per this thread This model plane is freakin’ sweet

The model turbine engines sold by ths company for large scale jet plane models are around 2,000 to 3,000 each fully configured. If they can sucessfully gang 8 of them together for a 300 lb B-52 model, why can’t they be used to produce a workable flying platform afor a full grown man?

The engines develop 12, 14 and 18 lbs (18 lb unit apparently shipping soon) of thrust each. If I attached 20 of these to a frame or platform of some kind that would give me 280-360 lbs of lifting power.

Other than the approx 60,000 - 70,000 invested in model airplane engines for 20 of these things what’s the hangup to this idea?

2

Be kinda fun to whack a couple on the back of my bicycle, an’ all.

3

The problem with a flying platform is that the engines are seeing almost zero forward velocity. Jet engines are much less efficient at lower speeds. You would not be able to get full thrust out of them if they are just holding you level.

4

The US Army has supposedly experimented with a 1 man flying platform called “WASP” (yes, is an acronym, no, I don’t know what it might be), but doesn’t like to talk about it for some reason. There’s a couple of problems with using your idea as a manned transportation device:

1.) Humans are notorously unaerodynamic flying machines. No, really.
2.) Without something like wings to generate lift, you’re gonna need a lot of engines and fuel.
3.) Without flaps or aerilons of some sort, you’re going to need to use vectored thrust to control your direction, that’s going to consume more fuel, and if you don’t watch it, you could wind up giving yourself a third degree burn quite easily, and those things are not fun, especially when you’re 30 feet in the air, and if you panic because your ass has suddenly caught fire, you could wind up doing a really nifty impression of a SCUD missile.
4.) You’re going to have to be careful where you locate the intake of the engines. Get 'em too close to you and you’ll get sucked into 'em when you fire that puppy up.
5.) I don’t think that you’ll be able to use a parachute with one of those things, so if you suck a bird or two into the intakes, you can expect to at least break a couple of bones when you come down shortly thereafter.
6.) The longest flight using a rocket pack (like the one in the James Bond movie) is something like 60 seconds, so you’re going to be limited to fairly short hops.

None of this means that it’d be impossible to build such a thing that operated safely, but it’d cost a heckuvalot of money and you probably wouldn’t be able to fly it for very long.

I don’t know if there’s a book discussing personal flying craft from an applied technology standpoint, but you might want to skim a copy of Unconventional Flying Objects by Paul R. Hill. Hill was a NASA engineer who saw a UFO and spent his off-hours trying to figure out how alien technology, if there was such a thing, might work. Surprisingly, the book isn’t filled with lots of wild-eyed speculation, as Hill worked out the physics of some of the things that he and others witnessed, and also built experimental devices to try and replicate some of the most likely ways things would work. The book is chockablock with mathematical formulas (all standard engineering and physics formulas) and has photos of Hill trying some of the things out. One of the reasons I bring this book up, is that Hill experimented with trying to figure out how best to build a man-sized flying platform, the book contains his findings, with both formulas and photographs.

He seems to have worked out the best method of controlling the flight of such a device, but admits that then-current engine efficiencies were such as to make anything other than a very short flight utterly impractical.

5

NASA did come up with a “flying bedstead” platform to allow the Apollo astronauts some simulated Lunar lander practice. So yeah, you can build a man-carrying flying platform. I think ducted fans might be more practical but yeah, you could use mini-jets if you don’t mind the expense and fuel burn.

Will your health insurance cover injuries sustained flying experimental aircraft?

6

I saw one of the “Flying Bedsteads” (LLRV) at Edwards AFB. It was in a hangar with the first lifting body, the [url=“http://www.dfrc.nasa.gov/Gallery/Photo/M2-F1/Small/EC63-229.jpg”]M2-F1.

More LLRV info and photos.
More M2-F1 info and photos.

If I suddenly had gobs of money, my dream would be to build an exact replica of the lifting body and to fly it. :slight_smile:

Back to the OP. There’s a saying that “You can fly a barn door, if you give it enough power.” As can be seen with the LLRV, you can lift a “platform” with a single, large engine. No reason you wouldn’t be able to do it with many small engines. But remember that they’re not exactly stable. Neil Armstrong had to punch out of an LLRV. (You do plan to put an ejection seat in yours, right?) Anr remember too, that you have a weight limit for ultralights. (Broomstick can tell you what other rules there are – for example, how many engines can an ultralight have?) If you go above the weight limit, then it becomes a “powered lift vehicle” and requires a license.

So using a bunch of little turbines to make a platform is a fun idea; but if you want to use them to build a man-carrying aircraft I’d suggest building something more conventional.

7

Fixing the links:

I saw a “Flying Bedstead” (LLRV) at Edwards Air Force Base. It was in a hangar with the first lifting body, the M2-F1.

8

Professional pilot, but not aero engineer, here …

Using jet engines for direct lift, ie thrust aimed to offset gravity, is stunningly inefficient. An AV-8B Harrier can do it for only a few minutes before exhausting it’s fuel supply.

As a general rule of design, the larger the craft, the relatively more fuel it can carry; that’s why trans-oceanic aircraft are so big. Yes, it takes more gas to move the larger airplane, but as the machine gets bigger, the fuel carrying capacity (& hence range & endurance) go up faster than the marginal increase in fuel burn to carry the larger aircraft and fuel.

So any very small personal-sized vehicle is going to be hard-pressed to carry more than a few minutes of fuel tops.

The next problem is control. Imagaine you built a platform, or some thing that looked more or less like a motorcycle or jet-ski (PWC). Now imagine it balanced on a narrow pole stuck up it’s underside. Not bolted or welded to the end of the pole; just balanced.

Now climb up there & sit on it without falling off the pole. Meanwhile, I’ll put a big fan in the room and blast 10 or 20 or 60 mph wind at you from the front or sides or back, moving my fan at random.

Tough problem for you to stay balanced up there. That’s what the control system needs to solve. With modern computers, gyros, etc, the design is simple enough for the professional engineers in the aerospace industry, but the DIY homebrew crowd is gonna fnd it a bit tough.

And what will you use to provide the power to steer / balance with? You can use vectored thrust, where the engines pivot to push left/right & fore/aft as needed, but you lose maybe 10% of yuor power doing that, exacerbating the challenge of getting enough power & range into the thing.

My bottom line:
Can it be done? Sure.
Will it be pretty lame in performance & endurance: Yes.
Would it be totally cool to have one: You bet.

9

Fixing the other link:

More LLRV info and photos.

To repeat what I said before, and to reiterate what LSLGuy said, controlling the machine would be difficult. Remember that the LLRV was built by “rocket scientists”, and one still crashed.

A similar machine would be a helicopter. Helicopters are inherently unstable. If you let go of the cyclic, it may “fall off” in any direction. The pilot needs to make constant, minute control inputs in order to heep a helicopter in the air. But a helicopter has its mass centred under the centre of lift, like a pendulum. A powered-lift aircraft would have the thrust underneath the centre of mass. A simpler example than the PWC on a pole might be to imagine a four-foot square piece of plywood on top of a bowling ball. You can sit on top and balance; but if you throw in some wind, an earthquake, or whatever, it will be very difficult.

Now, you could put your engines around the perimeter of the platform. Since your weight is in the middle, it would be easier to balance. But you need to be able to minutely control the engines individually in order to maintain balance. What happens if one or more fails?

Or you could use the Harrier approach: Put the engine in the middle and duct the thrust. At this point, you would have a bunch of the little model engines instead of a single “real” engine. Why not go for the actual aircraft turbine? And you’d still have the stability problem. And the fuel consumption problem.

When it comes down to it, there are cheaper, better ways of getting an awesome flying machine. You can get a MiG or an L-39 relatively cheaply. (You still have the training, maintenance and fuel costs, of course.)

Of course, this is all coming from the guy who’d love to have his own lifting body while there are zillions of actual gliders and sailplanes out there. :wink:

10

There was a video of this floating around but I can’t find it right now…

11

Then there’s the guy who has strapped a couple of rocket engines to a souped mechanics creeper that he’s built.

12

No limit on the number of engines on an ultralight, anything from zero to infinity. Hang as many as you want… as long as you don’t exceed the weight limit :slight_smile: There have been multi-engine ultralights, but they’ve largely disappeared, along with their builder/pilots. Given the other limitations imposed on ultralights, their performance wasn’t that great with all their engines running - minus one, it was deplorable and in some cases uncontrollable if there wasn’t enough rudder or power to overcome the assymetrical thrust problems. The accident/fatality rate scared a lot of folks off. I haven’t seen a true ultralight multi-engine design from later than the early 80’s. The AirCam is based on the Drifter ultralight, but it’s a “real airplane”, far above the weight/fuel/performance limits of it’s ultralight/lightplane single-engine ancestor/counsins.

A gent out in Ohio built an honest-to-goodness jet powered ultralight, a Mitchellwing. Another picture. Another picture. By the way - in that last picture an emergency parachute can be clearly seen as a large, white cylinder above one of the wheels. The guy might be a little crazy, but he’s not stupid. Could only get about 7 minutes of flight out of it or some such - jets just aren’t very efficient at slow speeds. Took it to the big Oshkosh fly-in one year, had the balls to put the thing on a scale to prove it was an honest-to-goodness legal Part 103 ultralight in all respect, including weight (weight is the most common limit blown by ultralight builders). Even less practical that the average ultralight, but kinda fun and funky to see.

Um… mini-jet turbines for model aircraft actually ARE real “actual aircraft turbines” - real small ones :slight_smile: Just like RC model aircraft are real aircraft. :smiley:

A big problem with multi-engine aircraft (of any size) is that the more engines you have the more stuff you have to go wrong. Even with big, well-funded aircraft, the most common multi configuration is two - you got three’s and four’s, too, and a very few with more than that. Each engine needs it’s own fuel supply, monitors, accessories… then you have to keep track of them all. And adjust them all. And troubleshoot them all.

Now, coming out of a an ultralight and experimental aircraft background where people built some pretty wild stuff just to prove it can be done, I think the idea of using mini-turbines to power a manned platform is pretty cool - but it IS wildly impractical (not that a hobby has to be practical) and you would spend a lot of money on it what with parts, fuel, and breaking stuff while you’re working out various problems. It IS a fact that experimental aviation on all levels has a higher rate of 'boo-boos", and the more unconventional the aircraft the higher the (already increased) chances of accidents. The laws of physics do not care if you’re an amateur - you don’t have to get very high to get very hurt. So I would urge extreme caution if anyone ever tries something like this, and contact your good buddies in the Experimental Aviation Association (EAA) - they always seem to have somebody who knows something about whatever wild idea someone else is proprosing. Making use of their knowledge base can save you time, money, effort, and doctor bills.