What is necessary for a hypothetical supersonic speed Radio Controlled Jet?

[Noob of the Maths]

TL;DR Summary

What its the necessary elements for a Radio Control Jet?

Hi everyone! :)

While i watched rc jet exhibitions on youtube, i find that the most fast of this RC reached +700 Km/h. When i browse more information about the tourbine, i realized that for a hypothetical supersonic RC the mechanical system of the tourbine must have a complete air compressor and exit tourbine.

Maybe the size of this kind of RC Jet its too difficult to have a complete tourbine with the compressor and afterbuner, but if this could be done...the velocity could be very very fast.

So, yeah, the aerodynamic design must have a lot of attention to resist the G force.

Im very corious about if this its possible to do and achieve the sonic boom.

I am engineering mechanic student, so i don't have much idea about aeronatic principies... but i undertand that building a complete system in a small thing can accomplish many things...

thanks for your attention!

 

[Baluncore]

There will be a sonic boom, but nearby it will sound like the crack of a passing high-velocity rifle bullet.

You will need to make it longer and thinner, give it a metal skin, and a sharp pointed nose. It will end up looking a bit like a Lockheed F-104 Starfighter
https://en.wikipedia.org/wiki/Lockheed_F-104_Starfighter

Notice how most model aircraft in the youtube videos behave a bit like butterflies, because the pilot reacts too late, and then by too much. At those speeds you will be unable to control it visually from the ground. You will need to include a MEMS chip with accelerometers and gyroscopes, so it can control it's orientation and angle of attack. It will need an auto-throttle so it does not stall on approach, and GPS tracking so you can find it. Your drone, which is what it is, will require an aircraft position transponder.

Now all you need is a dozen assistants, and some government funding from a military weapons development budget.

 

[DaveC426913]

It will end up looking a bit like a Lockheed F-104 Starfighter
https://en.wikipedia.org/wiki/Lockheed_F-104_Starfighter

And then you could call it ... The Kiddo Widow Maker...

 

[Baluncore]

I actually prefer the more elegant term “Erdnagel”.

 

[Noob of the Maths]

r and thinner, give it a metal skin,

There will be a sonic boom, but nearby it will sound like the crack of a passing high-velocity rifle bullet.

You will need to make it longer and thinner, give it a metal skin, and a sharp pointed nose. It will end up looking a bit like a Lockheed F-104 Starfighter
https://en.wikipedia.org/wiki/Lockheed_F-104_Starfighter

Notice how most model aircraft in the youtube videos behave a bit like butterflies, because the pilot reacts too late, and then by too much. At those speeds you will be unable to control it visually from the ground. You will need to include a MEMS chip with accelerometers and gyroscopes, so it can control it's orientation and angle of attack. It will need an auto-throttle so it does not stall on approach, and GPS tracking so you can find it. Your drone, which is what it is, will require an aircraft position transponder.

Now all you need is a dozen assistants, and some government funding from a military weapons development budget.

Well that sound like "flight simulator without respawn". Without the assistants and funding luck will be what will be most required. With the F-104 design and considering the amount of fuel... the risks are many, with a great result if it works...

 

[Baluncore]

... the risks are many, with a great result if it works...

There are too many skills required to take on the entire project alone. Everything can be purchased, with the exception of the one thing essential to taking the next step, the flight control system.

Any large investment in an RC model needs a dynamic autopilot to handle the short term stability flight control. On loss of communications, it should enter an orbit, if it times out, then it should return home by GPS, along the shortest previously used flight path, landing on autopilot or by ballistic parachute.

The quickest way to fly a supersonic RC model would be to develop a general purpose RC avionics package, something that could be parameterised to fly any RC model or drone. Let others sacrifice their aircraft and their physical investment.

Make it open source and available free, so your software would become the essential component in every realistic model that flies more than twice. There would then be a part of you in every one of those future successful models.

Think like Linux. Teach the penguin to fly.

 

[Rive]

The 'RC' part there means quite lot of problems alone. The plane will be out of visible range and common RC radio range in no time, so you need a reliable fast downlink to transmit telemetry and visual information, and a reliable uplink to transmit control signals. Has to cover a dozen kilometres, at the very least.

Also, the kinetic energy of the thing would be comparable to a cannon projectile. I guess you would have some troubles with the legal part too.

I think this project is definitely not for loners.

 

[Vanadium 50]

I actually prefer the more elegant term “Erdnagel”.

Is that German for "lawn dart"?

How do you get a F-104?
Buy some land and wait.

 

[Baluncore]

Is that German for "lawn dart"?

Erdnagel = Earth nail = tent peg.

 

[kalabren]

In the 1940s they could get their propeller planes almost to Mach 1 by putting them into a steep dive. In all cases they were stopped by the planes breaking or becoming unstable as they were not designed for that speed. The British eventually managed to get a Spitfire up to Mach 0.92 before they gave up with the idea.

I'm not knowledgeable about RC aircraft but I suspect your job would be much easier if you didn't try for level flight.

EDIT: I see with some Google that gliders have reached 0.75 mach (not counting things like returning space shuttles and whatever space magic is in the new PRC weapon) so I really don't think the problem is engine power. I can't imagine radio control being an issue in this day and age, so I suspect the problem is regulatory and the small number of civiilians who undersstand supersonic aerodynamics.

 

[cjl]

The biggest problem is that RC jet turbines don't have a good inlet or nozzle to provide thrust when supersonic. I disagree with many of the above statements - you do not need metal or even composites to make a structure that is able to handle supersonic speeds, and if you restrict yourself to low supersonic speeds, heating isn't much of an issue either. The plane could also be entirely stable, and therefore not require any kind of computerized stability assistance. You would need a telemetry package though, since it'll get out of sight far too fast to just control based on sight from the ground. However, it could be completely controllable with something like an FPV drone rig (basically an onboard camera transmitting back to you so it appears as though you are piloting it from onboard). It would be much safer of course if it had a rudimentary autopilot though that would fly it back to its origin point in case of loss of signal.

The real problem is propulsion. Making an airbreathing jet engine that works supersonically is (for obvious reasons) not a priority for the RC jet manufacturers, so you'd definitely need to make your own supersonic inlet to feed the engine and (possibly) a nozzle modification at the back of the engine too. I know a professor who was looking at making a supersonic drone using RC-derived engines for propulsion a while back (I don't know if that ever amounted to anything though), and he was looking at adding a custom afterburner and variable area nozzle to the engine to achieve the necessary performance, as well as a custom inlet to feed it, and that was for a design speed of mach 1.4.

It probably wouldn't be *that* difficult (technologically - all of these things would be hugely expensive of course) to make an RC aircraft that could do a brief supersonic dash using a supplemental rocket engine, as that takes care of the propulsion, but making one capable of sustained supersonic flight would be a pretty serious undertaking, primarily due to the propulsion requirements.

 

[DaveC426913]

Yikes! You're talking about a radio-controlled, radar-invisible, privately owned and operated supersonic missile!

That's terrifying just to think about!

 

[kalabren]

Not radar invisible, but I feel you're correct that it probably won't get noticed by the equipment and operators at the local airport.

 

[anorlunda]

Not radar invisible, but I feel you're correct that it probably won't get noticed by the equipment and operators at the local airport.

But would it be noticed by a Secret Service protection team?

 

[kalabren]

But would it be noticed by a Secret Service protection team?

I don't know anything about spies.

Military have stuff like this, so you know they're aware of the situation :-)

(Yes, that's a quadcopter jammer)

 

[Baluncore]

But would it be noticed by a Secret Service protection team?

It will be continuously radiating TV pictures back to the operator. Even if it does not show up on the radar, it will be very obvious to any RF energy surveillance system.

 

[kalabren]

Obviously the secret service agents pre-programmed the drone with good photos. There is no need for it to radiate or beam back a video feed.

EDIT: TIL "secret service" isn't spies but the protection for the USA president. Sorry guys! I thought you were talking about agents trying to sabotage the airport.

 

[berkeman]

Sorry if this has been asked already, but isn't there some new FAA standard for drone control and monitoring, in addition to drone/RC flight rules? I understand that bad operators will try to avoid those rules and monitoring, but hopefully for the good guys it provides a reasonable way to fly their crafts...

 

[jrmichler]

Here's a good article on the FAA drone rules. It has a link to the actual FAA rules. https://www.eaa.org/eaa/news-and-pu...on-news/news/09-01-2016-drone-rules-in-effect. The oversimplified version is to stay in sight of the drone, less than 400 feet above ground, in contact with ATC, the drone must weigh less than 55 lbs, and the operator needs a license.

The line of sight requirement rules out high speed operation. Note that many handguns have subsonic muzzle velocity.

The FAA is working on rules for drones operating beyond the line of sight: https://www.faa.gov/uas/programs_partnerships/beyond/.

The EAA (Experimental Aircraft Association) has lots of good information on drones. Go to eaa.org, and enter UAS (unmanned aircraft systems) into the search window.

 

[ChemAir]

If you really want to build something to break the sound barrier, I'd suggest joining a high power model rocketry club. In the US, Tripoli and NAR are the sanctioning bodies.

Of course, you can fly a lot higher in the black rock desert in Nevada, compared to Maryland, but Mach 2+ is achievable in multiple locations. It is legal if you are certified and you operate under a club altitude waiver.

My builds haven't gone fast enough to burn off paint, yet.

 

[dlgoff]

The oversimplified version is to stay in sight of the drone, less than 400 feet above ground ...

I have a small drone and yes 400 feet is the max altitude rules provide.

 

[DaveC426913]

you do not need metal or even composites to make a structure that is able to handle supersonic speeds, and if you restrict yourself to low supersonic speeds, heating isn't much of an issue either. The plane could also be entirely stable, and therefore not require any kind of computerized stability assistance. You would need a telemetry package though, since it'll get out of sight far too fast to just control based on sight from the ground. However, it could be completely controllable with something like an FPV drone rig (basically an onboard camera transmitting back to you so it appears as though you are piloting it from onboard).

Point-of-order: I am greatly concerned about the discussion potentially veering into ways to design and engineer what amounts to a remote-controlled missile. A 20 pound object being consciously directed at 1000mph into a target can do a lot of damage.

I see it as no different from discussing how one might make explosives or toxins - i.e.: As long as readers obey the law, there's no harm - and yet - it's still it's arming and informing those who wish to do harm. The PF I know and love frowns on that.

Just my 2c.

 

[berkeman]

Point-of-order: I am greatly concerned about the discussion potentially veering into ways to design and engineer what amounts to a remote-controlled missile. A 20 pound object being consciously directed at 1000mph into a target can do a lot of damge.

I dunno. The bad actors don't need our help on that. And I don't think what's been covered so far will help incompetent teenagers to design something dangerous on their own. So far the Mentors have discussed this thread some, and it's probably okay to continue for a bit. But it would be good to stick to how to design something that falls within the existing or near-future FAA regulations (and other regulations for other areas in the world).

 

[DaveC426913]

The bad actors don't need our help on that.

And yet would we not stop a similar discussion about creating explosives or toxins? I think the only difference is that we do not intuitively assume drones are intrinsically weapons of destruction, unlike toxins and explosives. (Remember the cautionary tale of 9/11 - realizing after-the-fact that a mere civilian airplane is intrinsically a WMD).

(Rhetorical. No need to beat this to death. I've stated my concern.)

 

[DaveE]

There's no indication that anyone here, including the OP, has any intention of building this. If they did it likely wouldn't get off the drawing board.

Summary:: What its the necessary elements for a Radio Control Jet?

Im very corious about if this its possible to do

That is all, I think. Just a question from an engineering student.

BTW, the answer is yes. If Lockheed can build an F-104 in the early 1960's, this could also be built in 2022. It's just a question of money, knowledge, experience, etc.

 

[DaveC426913]

If Lockheed can build an F-104 in the early 1960's, this could also be built in 2022.

That's a cool idea! Gorgeous plane - one of my faves.
I wonder if 21st century technology could make a safe F-104? Just for the cool factor.

 

[DaveE]

That's a cool idea! Gorgeous plane - one of my faves.
I wonder if 21st century technology could make a safe F-104? Just for the cool factor.

What are you waiting for, you can have one tomorrow!
https://warbirdsnews.com/warbirds-news/flyable-cf-104-starfighter-for-sale.html

 

[berkeman]

And yet would we not stop a similar discussion about creating explosives or toxins?

And I don't think what's been covered so far will help incompetent teenagers to design something dangerous on their own.

I think this is the main difference...

(Rhetorical. No need to beat this to death. I've stated my concern.)

Thanks.

 

[DaveC426913]

There's no indication that anyone here, including the OP, has any intention of building this. If they did it likely wouldn't get off the drawing board.

That is not the litmus test that is applied to discussing explosives or toxins. The litmus test is usually could some unknown reader use this information with the intent to cause harm?

 

[DaveC426913]

What are you waiting for, you can have one tomorrow!

Not a chance man! (talk about lethal weapons!) My wife is not a widow yet and I want to prolong that status.

 

[kalabren]

You can probably buy an old Mig-31 from somewhere. They're reliable, still in service, and super fast. Similar role to the F-104 but newer design.

 

[Baluncore]

A rifle can launch a missile that exceeds the speed of sound. You will need to make a very small radio control receiver to steer the spinning bullet. There are gyros that will easily fit with the receiver inside a round. The very small control surfaces on the spinning bullet will need to operate at above 1 kHz.

 

[jrmichler]

Summary:: What its the necessary elements for a Radio Control Jet?

Im very corious about if this its possible to do and achieve the sonic boom.

To summarize the thread so far: It is possible, but...

1) You need to design and build an airframe that is controllable over the full speed range
and
2) Is strong enough to withstand the aerodynamic forces
and
3) Low drag at supersonic speeds
and
4) Takeoff and landing speeds low enough to be able to use existing runways
and
5) A semi or fully autonomous control system
and
6) Get permission from the FAA
and
7) Design and build a jet engine capable of supersonic operation
and
8) A suitable telemetry system with pilot interface (think glass cockpit)
and
9) A few things I did not think of yet.

The effort required is years, not weeks or months, for each of the above items. That explains why nobody has done it yet. Also, high speed flight has considerations that are not necessarily obvious. For example, a 2 G turn at 1000 ft/sec will make a circle about 6 miles diameter.

 

[DaveC426913]

"...a 2 G turn at 1000 ft/sec will make a circle about 6 miles diameter"

Uh huh, and what is that reduced to at >12g's?

Spoiler: Hint

<1 mile

 

[cjl]

Point-of-order: I am greatly concerned about the discussion potentially veering into ways to design and engineer what amounts to a remote-controlled missile. A 20 pound object being consciously directed at 1000mph into a target can do a lot of damage.

I see it as no different from discussing how one might make explosives or toxins - i.e.: As long as readers obey the law, there's no harm - and yet - it's still it's arming and informing those who wish to do harm. The PF I know and love frowns on that.

Just my 2c.

Honestly, the way I view it, anyone with the technical ability to make this actually happen won't have that much difficulty figuring out how. This is well beyond just assembling commercially available parts here, even with all the information provided above.

As I said, a significant amount of what I know about it comes from a former professor of mine working with a team of aerospace graduate students and a decent amount of funding, and though I'm confident we came up with a viable concept for a mach 1.4 drone based on commercially available parts, it took a huge amount of time and still involved a lot of custom work to get it (hopefully) functional, and as far as I know, it never actually turned into real flight hardware.

To me, this is very different from something like an explosives discussion, where it genuinely is plausible for someone with little experience to make something that at least is fairly dangerous by themselves without a lot of additional resources. To make a working supersonic UAV, you'd be talking tens of thousands of dollars and hundreds or thousands of hours of design and fabrication work, and that's assuming you know what you're doing.

 

[Rive]

Uh huh, and what is that reduced to at >12g's?

12g for a DIY custom drone? The question would be about the debris distribution, right?

You can probably buy an old Mig-31 from somewhere.

Sure. Though a Mig-21 would be a better choice, and it's dirt cheap.
But, to actually fly it (to keep it in flying order) would take lot more than just the bird, you know...

 

[DaveC426913]

12g for a DIY custom drone?

Premise already established that it will hold together at Mach 1+. So not a stretch.

 

[kalabren]

A rifle can launch a missile that exceeds the speed of sound. You will need to make a very small radio control receiver to steer the spinning bullet. There are gyros that will easily fit with the receiver inside a round. The very small control surfaces on the spinning bullet will need to operate at above 1 kHz.

Guided smallarms rounds do exist. As far as I am aware, the USA and the PRC both have one, though they are too expensive and temperamental to use operationally.

I don't know any technical specifications of the rounds, in particular whether or not they spin if they have control surfaces.

You can probably buy an old MANPADS (the shoulder anti-air missiles) for USD 300 and a goat. If you were trying to be super bad, that's probably much easier that building your own missile. As such, I don't see any inherent danger in this thread.

 

[Astronuc]

1) You need to design and build an airframe that is controllable over the full speed range
and
2) Is strong enough to withstand the aerodynamic forces
and
3) Low drag at supersonic speeds
and
4) Takeoff and landing speeds low enough to be able to use existing runways
and
5) A semi or fully autonomous control system
and
6) Get permission from the FAA
and
7) Design and build a jet engine capable of supersonic operation
and
8) A suitable telemetry system with pilot interface (think glass cockpit)
and

I like jrmichler's response, but I would put the FAA at the top of the list, since they regulate what goes up into the atmosphere, especially aircraft.

https://www.physicsforums.com/threa...eed-radio-controlled-jet.1007617/post-6580673

https://www.faa.gov/newsroom/supersonic-flight
Currently, U.S. law prohibits flight in excess of Mach 1 over land unless specifically authorized by the FAA for purposes stated in the regulations. The two supersonic rulemaking activities would not rescind the prohibition of flight in excess of Mach 1 over land.

Unmanned Aircraft Systems (UAS)
https://www.faa.gov/uas/
https://www.faa.gov/newsroom/small-unmanned-aircraft-systems-uas-regulations-part-107 (probably precludes supersonic UAS, or small UASs). I would imagine that if one obtain permission, one would have to test/fly such an aircraft in restricted airspace, similar to that for small spacecraft /rocket launches.

Some rules concerning drones/UAVs

Operating Requirements
Just as there are rules of the road when driving a car, there are rules of the sky when operating a drone.

• Always avoid manned aircraft.
• Never operate in a careless or reckless manner.
• Keep your drone within sight. If you use First Person View or similar technology, you must have a visual observer always keep your drone within unaided sight (for example, no binoculars).
• You cannot be a pilot or visual observer for more than one drone operation at a time.
• Do not fly a drone over people unless they are directly participating in the operation.
• Do not operate your drone from a moving vehicle or aircraft unless you are flying your drone over a sparsely populated area and it does not involve the transportation of property for compensation or hire.

Recreational Flyers & Modeler Community-Based Organizations
https://www.faa.gov/uas/recreational_fliers/

There may not be a rule for supersonic UAVs, since nobody does that - yet. Yes, US, Russia, China, and others, are looking a hypersonic aircraft/missiles obviously with military applications, which is why it may not be legal for supersonic drones (UAVs).

Technically, one only needs a propulsion system that can push such a craft through the atmosphere, meaning the thrust must equal drag at the designed supersonic speed. The rest (aircraft geometric design, flight control surfaces, strength of materials (structural integrity), . . . is pretty straightforward.

 

[berkeman]

Okay, I think the question in the OP has been answered pretty well, including practical considerations for how to keep track of such a fast RC aircraft/drone. Since we are heading into discussions about SA-7 missiles and goats, it's probably best to tie off the thread now. Thanks everybody for an interesting discussion.