Supersonic R/C

Hi guys,
I've given some thought to the subject of high speed R/C, and a recent
thread about speed records has prompted me to post.
First of all, I know that the following would not be AMA or NAR compliant.
I'll keep this to the realm of 'what if'.
Hypothetically, I've wondered about what it would take to fly an R/C plane
and take it supersonic.
For those here that are not familiar with high powered rocketry, it's a
subset of the model rocket hobby that involves rockets that can be hundreds
of pounds in weight and soar to astonishing heights (to the point of
needing waivers from the FAA). To fuel this sport, special large rocket
engines are used. These engines have some performance and thrust
advantages over the disposable engines you might purchase for a normal
model rocket and can be bigger then a coffee can.
Starting with one of these engines, say perhaps an 'L' or 'M' size, I
imagine that an experienced modeler (with a good aeronautical background)
could build a plane with a fiberglass or carbon fiber skin that could be
dropped from a carrier plane half a mile uprange from the R/C operator,
have its motor ignited, power past mach 1 in controlled, powered flight,
then be landed conventionally. If airframe stresses of turning within the
control radius ofthe radio (or visibillity of the operator) is a concern,
you could have more then one operator spaced across the range.
Legal issues aside, can anyone think of any technical reasons this couldn't
be done?
Best regards,
Ben Hallert
Reply to
Ben Hallert
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Take it up on a balloon to 100,000 feet and let gravity do the work for you.
Reply to
Don Hatten
All it would take is time and money.
I'm sure a qualified aerodynamicist could work out the thrust-to-weight-and-drag formulas so that you could be sure of reachig your objective.
The speed of sound varies with temperature.
At 24C (~75F), the speed of sound is 1135 fps.
You're going to need pretty good bioculars, well-focused, to keep your model in sight from drop through the speed trap. Once the rocket's done burning, I guess things will calm down eventually.
Flutter and adequate power to control the surfaces seems to me to be the next major hurdle. You might want to test the model in a supersonic wind tunnel prior to turning the model loose anywhere near humans. Legal and insurance issues aside, you don't want to hurt anyone (I imagine). I'm sure that some people know what it takes to control an RPV at those speeds; whether they can or will tell you what they know is another issue entirely.
Let us know how things turn out.
Marty
Reply to
Martin X. Moleski, SJ
Ever heard of terminal velocity:
Sqrt ((2 * Weight)/(Drag Coefficient * Density * Area).
100,000 feet ain't gonna do it.
Mike
background)
Reply to
<phillipsmike
There are turbines available NOW that calculations show will take a model to excess of 500 mph... The problem is maintaining physical control from the ground, and building a model to take the stress.... Such a model will get small to the eye in a hurry, and normal construction methods won't cut it.....
But newer more powerful digital servos are available and composite materials are becoming more commonplace...
I believe this will be done before long, and I believe the flights will be autonomous when they happen.. Just WHERE it'll happen remains to be seen... It's not likely to be in the States.
Bill
Reply to
Bill Fulmer
At the speed of sound your model is going to be covering the dirt at roughly 1000 feet per second. Depending on the altitude you choose to attempt this at. But what this means is from your 1/2 mile point of release, you'll have something like 3 seconds (or less) to spot it, orient to it (figure out its attitude) and command it to do...........................?
This of course assumes the beast is stable enough on its own to fly straight and level from release to the point you tell it to do something. Otherwise, by the time you figure out what it's doing, and figure out what to do to correct it, and tell it............................................Splat!
I suspect it will zip past you so fast, you'll still be looking for it to appear in your field of vision as it disappears behind you.
Chuck
Reply to
C.O.Jones
If it looks like you are actually going to do this, please let us know in advance so I can arrange to be as far away as possible. Thanks.
Reply to
John R. Agnew
How quickly the great ones are forgotten. USAF Captain Joe Kittinger broke the sound barrier 40 years ago in free fall from 102,000 feet.
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Reply to
John Alt
I'm pretty sure a model airplane pointing straight down has less drag than a human body does and Joe Kittinger hit 614mph from 102,000.
Call me to tell me I'm wrong after the experiment is over.
Don
Reply to
Don Hatten
Thanks, John
Don
Reply to
Don Hatten
Let's say 1100 fps at a comfy temperature.
1/2 mile = 2500 feet = 2.27 seconds.
Of course, it won't reach top speed instantaneously, so perhaps the flight team will have 5 seconds to spot and fly it on its way toward them and perhaps another 3 before it becomes invisible.
Maynard Hill has shown that models can be flown autonomously. Part of the investment in the Fastest RC Plane on Earth will have to be an autopilot and a GPS system. Do what Maynard did: takeoff, turn on the autopilot, watch the flight, recover control, land. (I am NOT in any way criticizing Maynard or his team. Just describing what they did.)
Not technically impossible. Not cheap.
For those who have the money, it would probably be something to do out on the salt flats. I'd invest in a pretty good bunker myself, just in case, while the kinks were being worked out of the system.
Marty
Reply to
Martin X. Moleski, SJ
If the AMA hasen't banned such attempts, they should. Lest we not have a hobby after the feds take notice.
I don't see what all the hoopla is about, chasing records the Air Force beat 40+ years ago with vacuum tube controlled vehicles.
Reply to
John Alt
sniperzz...
it could be done... get a level 2 Tripoli card. Buy a K-500 or 1000 motor ( wont need a L or a M those are wayyyy too big) , build a carrier plane and the "rocket plane". Fly the combo towards you and as it passes overhead fire off the rocket plane... that way it wont pose too much of a problem in nailing your group of ground support. ( mind you that they are all behind the line of motor ignition point.
Either the rocket plane will shread in 2 seconds or it will fly for 10 seconds...
a final note... put your AMA and Tripoli card near the exhaust of the rocket motor.. if any of the Powers of Might from either group see this flying feat... :)
Scot D
TRA 539
Reply to
BunnyKiller
Why does a person climb any mountain that has been climbed before?
Why does anyone do anything that even though someone may have doen it before, that anyone has not done it before?
Why does anyone ever wish to travel "...just over that hill?"
For whatever reason it may be, I am truly thankful for those reasons and the people that climb those hills, mountains, & whatever.
HC
Reply to
CainHD
I would think you would have those answers for us Horace! How many of those "Election" hills have you been up?
Reply to
C.O.Jones
Yes it will..here's a link to Joe Kittinger who jumped from 102,800 feet and MAY have reached Mach1.
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jumps from a higher altitude are being planned for right now.
Brian
snipped-for-privacy@bellsouth.net wrote:
Reply to
Brian
Just a few minor little problems. First, control is only available when the operator can SEE the 'aircraft'. I don't know how you can see a model at over 100,000 feet. Better eyes than mine! The remote systems used by Maynard Hill probably will be of extremely limited value since the distance covered in a very limited period of time is simply huge.
Second, the model PROBABLY cannot carry enough fuel to accelerate fast enough to go supersonic if there was a small a turbine capable of providing that much push and I strongly suspect the Feds would be upset if you were building a rocket capable of that feat. Howeve, those are probably just minor technical details.
I guess you could talk to the USAF about one of their old F-100's that are being used up as target drones. Be prepared to be disappointed because international treaty requires certian actions taken to 'safe' these airframes. Typically they take a chain saw to the main spar and carry throughs.
Oh yes, the third problem has to do with federal law prohibiting supersonic flight over the Contential United States. But that is just another law that can be easily broken if you have deep enough pockets and a senator or two on your 'staff'.
LOL!
Reply to
Six_O'Clock_High
Just a point of info! The high power rocket guys have an event called the drag race. Where they do in fact launch rockets that break the sound barrier. Granted, they're going more or less straight up. But you do hear something of a sonic boom and they do reach between 5000 to 15,000 feet altitude (or more). They also have others, slower, that make it as high as 30,000 plus. And yes, they coordinate with the FAA for these events and get a corridor cleared. Something to see at least once even if you're not into rockets.
Chuck
Reply to
C.O.Jones
The key here is Radio "Control". Since supersonic speed will take the model out of sight in a split second, you then have to include the issue of UAV control. The technology is here right now to put supersonic and UAV together to do what you "theoretically" suggest, but from the pure issue of fun, why? I sit here and spin up my imagination, and I still can't see what would be fun about it other than to use it as a "trophy" accomplishment (as in: "Look what I can do!". Sort of like how the character Stuart acts on MAD TV in the U.S.)
MJC
Reply to
MJC
Maynard Hill set an FIA record using a UAV. It was under human control only at the beginning and the end of the flight.
"De gustibus non disputandum." There's no arguing with taste. The fellow who started this thread only asked whether it was technically possible, not whether it was legal, wise, or entertaining.
I think it's technically possible. All you need is time, money, a few moderately clever people, and wide open spaces. The laws of aerodynamics are what they are. The technology exists.
I know that I won't invest in the project and I gather that you won't, either. I wouldn't be too surprised if some wealthy people decide to do it or something like it. Folks with money to burn often burn money. :o)
Marty
Reply to
Martin X. Moleski, SJ

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