HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old May 23, 2013, 07:59 AM
"The Judge"
sebbe's Avatar
Sweden
Joined Feb 2006
5,792 Posts
Discussion
Mach 1 !!! ???

WIll it ever be possible ?? how ?
sebbe is online now Find More Posts by sebbe
Reply With Quote
Sign up now
to remove ads between posts
Old May 23, 2013, 12:07 PM
Registered User
United States, AL
Joined Apr 2007
823 Posts
OK, I'll bite. Set the requirements: take off from ground under own power? Land without damage? Under remote control by a single individual?

I think the plane could be built, but I dunno how you would power it. The model jet engines will prove insufficient I think until somebody builds them with augmented thrust. I don't believe they have the thrust/drag ratio to drag a plane through the sound barrier right now.

One option would be a rocket powered missile shaped vehicle dropped from another aircraft. With gravity help and a smoke trail to help see it I think it could be done. Control and landing would be difficult, but this would be just to say you broke Mach 1 with a RC plane.

Either way control will be difficult and the feasibility will depend on restrictions placed on the model.
biskit is offline Find More Posts by biskit
Reply With Quote
Old May 23, 2013, 02:38 PM
"The Judge"
sebbe's Avatar
Sweden
Joined Feb 2006
5,792 Posts
you are probably right, to control it, land, start it would not be possible maybee....

would be cool to see how fast electric motor/prop could go, without the need for start/takeoff/handlaunch, and you can have as high wingloading as needed,,,,,.... like you said, maybee draw the plane up with another bigger plane first, then release it in air, then go for it,,,, well landing is another matter, hehe

you could make a plane with super small ailerons/elevator just to control it in high speed, otherwise flutter will be a problem allready at 500km/h. then it needs to have very efficient and aerodynamic wing and fuselage..... the problem is, no way an electric motor and prop will reach those pitchspeeds needed to break mach1... maybee 700-800km/h ?
sebbe is online now Find More Posts by sebbe
Reply With Quote
Old May 23, 2013, 02:41 PM
"The Judge"
sebbe's Avatar
Sweden
Joined Feb 2006
5,792 Posts
is it possible making a 12x50 prop ?,, making that spin at 15000rpm ....
sebbe is online now Find More Posts by sebbe
Reply With Quote
Old May 23, 2013, 02:53 PM
Registered User
Canada, NS, Lunenburg
Joined Oct 1999
3,866 Posts
You can't get through the sound barrier with a prop driven airplane.

A gas turbine with afterburner should give you the power you need.

Control and safety will be the biggest issue.

Controlling such a model using only the sight of a pilot on the ground is not practical. At Mach 1, any reasonably small model will go from out of sight upwind to out of sight downwind in less than five seconds. That doesn't leave any time or space to turn before you lose sight of it.
DaveSawers is offline Find More Posts by DaveSawers
Reply With Quote
Old May 23, 2013, 04:52 PM
Livin it UP when Im goin DOWN
Arcteryxxx's Avatar
Norway, Telemark, Skien
Joined Feb 2010
4,341 Posts
Must be FPV...
Arcteryxxx is offline Find More Posts by Arcteryxxx
Reply With Quote
Old May 23, 2013, 05:45 PM
Pile-it
Alien_Tech's Avatar
United States, CA, Palmdale
Joined Nov 2007
1,698 Posts
Quote:
Originally Posted by sebbe View Post
you are probably right, to control it, land, start it would not be possible maybee....

would be cool to see how fast electric motor/prop could go, without the need for start/takeoff/handlaunch, and you can have as high wingloading as needed,,,,,.... like you said, maybee draw the plane up with another bigger plane first, then release it in air, then go for it,,,, well landing is another matter, hehe

you could make a plane with super small ailerons/elevator just to control it in high speed, otherwise flutter will be a problem allready at 500km/h. then it needs to have very efficient and aerodynamic wing and fuselage..... the problem is, no way an electric motor and prop will reach those pitchspeeds needed to break mach1... maybee 700-800km/h ?

The DS guys are already knocking on 500 mph (496 I think), so the structure already a long way to being developed. As far a prop powered plane doing it, it can be done, it's just not very efficient. No aero laws preventing it. My bet is the DS guys doing it first.
Alien_Tech is online now Find More Posts by Alien_Tech
RCG Plus Member
Reply With Quote
Old May 23, 2013, 05:57 PM
Registered User
sneu's Avatar
United States, CA, San Diego
Joined Dec 1999
7,344 Posts
Quote:
Originally Posted by Alien_Tech View Post
The DS guys are already knocking on 500 mph (496 I think), so the structure already a long way to being developed. As far a prop powered plane doing it, it can be done, it's just not very efficient. No aero laws preventing it. My bet is the DS guys doing it first.

I bet not--the energy needed to get from 500 to 750+ is way more than you know.

Steve Neu
sneu is offline Find More Posts by sneu
Reply With Quote
Old May 23, 2013, 06:12 PM
2012 NZ Speedcup - 231 MPH
DownUnderPilot's Avatar
New Zealand, Tasman, Richmond
Joined Mar 2006
1,979 Posts
Rocket powered and FPV may well make it possible, given enough money and a suitable location. Forget the propeller idea.
DownUnderPilot is online now Find More Posts by DownUnderPilot
Reply With Quote
Old May 23, 2013, 07:00 PM
Registered User
United States, AL
Joined Apr 2007
823 Posts
To break Mach 1 with a prop the prop tips are well above supersonic and the prop thrust and efficiency will drop like a rock. There's a reason no prop plane has broken the sound barrier.

I will say rocket power is the only feasible way right now. The inlet drag of a tiny turbine is far too much relative to its thrust.

Just because a glider goes 500mph doesn't mean it can break the sound barrier. Strength is not the issue, shock waves and rigid surfaces are the problem.
biskit is offline Find More Posts by biskit
Reply With Quote
Old May 23, 2013, 08:36 PM
Registered User
United States, VA, Manassas
Joined Dec 2007
120 Posts
The only way I see it being done soon (after a couple of years of testing) is a 60 degree delta built minimum diameter around a 54mm J180 casing. Initial thrust of about 80 lbs tapering off to about 40 lbs over 4+seconds could do it if it is kept minimum diameter and very thin. Air start also. Don't want to start the legal argument, but FPV would be the only way to go. It will be covering almost a mile in the 4 second burn. Landing a very thin and heavy delta is not a problem. Deltas are the best choice if you do not turn at all during the run. The high induced drag of a delta also makes it perfect for putting on the brakes after a speed run. Dont ask me how I know about rocket powered RC, I will deny everything. Lets just say I started on testing more than a decade ago and the visibility thing became an issue very quickly. CG is an issue also. You are burning about a pound of fuel in 4 seconds. Something that kinda worked for ground launch test was a water bladder. I never got to the J motor stage, only G.

Brooks
bpbrinson is offline Find More Posts by bpbrinson
Last edited by bpbrinson; May 23, 2013 at 09:12 PM.
Reply With Quote
Old May 23, 2013, 09:07 PM
Drinks Day Old Expired Milk
VooDoo Child's Avatar
United States, OR, Portland
Joined Aug 2010
2,832 Posts
Sounds like Richard Branson needs to be called in on this one :-)
VooDoo Child is offline Find More Posts by VooDoo Child
Reply With Quote
Old May 23, 2013, 09:24 PM
Registered User
United States, VA, Manassas
Joined Dec 2007
120 Posts
I was kinda hoping you would give it a try, Voodoo. You got the skills to go that fast , but what about FPV? I would really prefer to be on 100% preprogrammed gyro for the boost phase. You have not seen what I have seen.

Brooks
bpbrinson is offline Find More Posts by bpbrinson
Reply With Quote
Old May 23, 2013, 09:33 PM
Registered User
United States, AZ, Tucson
Joined Nov 2010
4,043 Posts
Quote:
Originally Posted by biskit View Post
To break Mach 1 with a prop the prop tips are well above supersonic and the prop thrust and efficiency will drop like a rock. There's a reason no prop plane has broken the sound barrier.

I will say rocket power is the only feasible way right now. The inlet drag of a tiny turbine is far too much relative to its thrust.

Just because a glider goes 500mph doesn't mean it can break the sound barrier. Strength is not the issue, shock waves and rigid surfaces are the problem.
Well it actually is entirely possible for a prop plane to do it. The problem is the supersonic transition on the prop its self. The prop generates a huge pressure differential, which causes both sickening loud noise, as well as extreme vibration. The solution is a specifically designed prop that would spin fast enough that even the root chord would be super sonic. If you look into it there have actually been quite a few props that have developed into very efficient subsonic applications. Proper prop development is just NOW starting to break through. Have you seen THIS prop? Props like these are redesigning the way aircraft are made.

Anyhow, although supersonic prop planes do not exist, they are possible. Unfortunately most people/organizations give up on the quest because they realize the draw backs, and utter pointlessness of doing so!

As for truly breaking the sound barrier with RC, it will most definitely rely on a rocket powered aircraft. KNO3 rockets are simple, and can produce amazing thrust for cheap. A hollow carbon delta wing FPV glider would do it as mentioned by BpBrinson.

PS, it is very easy to make dual stage rockets, and or high powered KNO3.

If I were to build one it would be a hollow carbon glider, staged with 3 rockets. All 3 would ignite, the two outer being more powerful, quicker burning rockets, meanwhile the less powerful single rocket would burn approximately twice as long. After the two outer are spent, they would be ejected to reduce drag, and weight.

As for a safe way of doing it.... I guess FPV? They have what approximately 4 mile range? I would launch about .5-1.0 miles away, and when ignite start climbing from the sky. A 40-60 degree trajectory will generally be your best bet IT would reduce the altitude, as well as distance traveled, keeping you within range of FPV. It also "usually" works out to be the most efficient when it comes to overcoming gravity. Not to mention, altitude would be nice for trying to slow down, and get home safely
Jwmflying14 is offline Find More Posts by Jwmflying14
Reply With Quote
Old May 23, 2013, 09:44 PM
Registered User
United States, AZ, Tucson
Joined Nov 2010
4,043 Posts
PS, not sure a Gyro would help... I am not positive what reynolds numbers this would be operating in, but you would most definitely encounter some very challenging aerodynamic hurdles. Ever heard of an RC getting compression locked controls?! Oh god! Super sonic aerodynamics are mind blowing-ly complicated... Depending on shockwaves, as well as compressible high and low pressure zone effect the way they fly. Aircraft develop flutter, control lock, and extreme flutter. In some cases aircraft have reversed their controls do to changing the center of pressure on a wing during control surface deflection, they have lost all control, and controls have locked up. An improperly design wing can technical stall at the leading edge creating a void in which a control surface actuates, therefore having no effect at all...

It was the sound "barrier" for many years due to these complications...

PS, an RC turbine will never work. You will guaranteed have a compressor stall if you ever even got close to the speed.
Jwmflying14 is offline Find More Posts by Jwmflying14
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Gallery Show us your Mach-1 chip.greely Slope 12 May 13, 2013 11:41 PM
For Sale Mach 1 RTF $450 Jason Lilly Aircraft - Sailplanes (FS/W) 0 Jan 20, 2013 10:35 PM
For Sale Mach 1 ScottCondon Aircraft - Sailplanes (FS/W) 0 Jan 20, 2013 07:28 PM
Sold Mach 1 Mark Canfield Aircraft - Sailplanes (FS/W) 12 Jan 14, 2013 12:00 AM
Wanted Mach 1 and Mach None kits gavoss Aircraft - Fuel - Airplanes (FS/W) 2 Apr 17, 2010 12:41 PM