Helicopter Rotor Blade Radar (RODAR)

[SeaMac]

I've had this idea for decades and after having researched discovered there are numerous patents relating to the subject. Reading the abstracts, a main rotor based radar system makes great sense and provides for a very sensitive radar. Due to the width of the radome in relation to the size of the rotor disc a Synthetic Aperture Radar could be developed to rival or surpass anything currently available. For a helicopter this would provide 360* situational awareness, terrain avoidance, weather, obstacle detection etc. etc.


There are also patents relating to Electro-Optical systems built-in to the rotor blade tips. Combining both these technologies into the main rotor leaves the fuselage free of any aerodynamics robbing appendages and again just makes sense.


My question is, why have these ideas not gone any further? With today's miniaturization of electronic components, computing capability and composite materials along with the safety and operational benefits of developing such systems would seem to me to be a priority.

[ion_berkley]

OK I'll bite since I design RADAR stuff amongst other things.

A quick "back of the fag packet calculation" gives me the following:

Lynx rotor disc diameter (as an example): 12.8M
Lynx blade tip speed: 700 feet/sec = ~ 214M/S

Centripetal Acceleration = (v*v)/r = (214 * 214)/6.4 = 7155 M/S^2
i.e 70g constant acceleration.

It's not exactly a friendly environment for a relatively massive, sophisticated and delicate piece of electronics then. Cooling at least would not be such a problem....

Then there's the pragmatic problem of how you service, power and communicate with it.

In other words I suspect that it has theoretical benefits as you point out but is in practical terms a non-starter.

[SeaMac]

I believe one of the patent holders is Bell and they brought the system up to a technology demonstrator. Clearly it ran into issues, likely those mentioned above. As for servicing and powering, don't they operate rotor ice protection systems (RIPS) where there must be power and the ability to service the components?


I'm certain with at least the military application if it could be done it would have but then again DoD contractors tend to move at a snails pace when it comes to new technology. I'm just wondering with all that is new in technology why a system couldn't be made viable? Let me qualify myself here, I am not a pilot or engineer just someone who thinks too much sometimes.... lol

[Ascend Charlie]

The frontal area for the antenna is only a couple of inches, which will govern the wavelength of the radar waves, which will govern how useful they are for detecting or penetrating cloud, aircraft, rocks etc.

The rotation rate of 5 per second is pretty fast and will govern the range of the radar (short), though I suppose it is only for really close-in stuff. There will also be doppler shift to deal with, as the antenna is not fixed.

[SeaMac]

I know nothing of the specifics pertaining to operational characteristics of radar systems. I have read the patent applications from numerous sources mostly Electrical Engineers and in the abstracts and descriptions they proclaimed a very high degree of detail could be provided to the point of 3D Synthetic Aperture capability. In most instances the radar antennae itself was really no more than a wire installed within the leading edge of each rotor blade.

[bigglesbutler]

As I understand it a RIPS system only has slip rings to transfer the electricity from one side of the swash plate to the other (fixed - moving). Not sure how intelligent the parts on the head and blades are other than heating mats and cables.

Si

[Been Accounting]

I seem to remember something being shown on BBC TV with a very high definition image.

http://ieeexplore.ieee.org/ielx5/5266378/5268715/05268720.pdf?tp=&arnumber=5268720&isnumber=5268715

[SeaMac]

I've seen the document you provided in the link, it's the Ferranti system one of many I discovered while researching USPTO applications.

[cattletruck]

Seems to me that a lot of complex mathematics are required to determine the sensors whereabouts in relation to the returned radar signal. There's RRPM, pitch, flap, lead-lad, flex, twist, flutter, and probably more that needs calculating.

Although it seems like a good idea on paper, with sensor resolution continually increasing for any given size, then there may not be a requirement for locating a sensitive bit of equipment in such a hostile environment.

[AArkley]

Something like this, you mean?

t-VTF-jZdUQ


https://youtu.be/t-VTF-jZdUQ?t=41m40s

[SeaMac]

@AArkley,


Yes, that is very similar to RODAR. Since the HeliRadar is a relatively recent system one developed in association with Eurocopter I have to assume that many of the challenges mentioned above have been addressed. Now to have the antennae integral with the rotor itself, I have no doubt that DARPA or some other entity is working on it.


BTW, it would have been nice of you to indicate the segment which mentioned the HeliRadar was @ 41:44, it would have saved me and possibly others from watching the entire video. Thank you though for sharing.

[HLCPTR]

For close-range obstacle detection, the AW139 has an option for LIDAR which will provide the crew with information on potential conflict with lateral obstructions. This is obviously not a "cruise flight" function, but one which will provide proximity information during hover operations.


Perhaps not what the OP was looking for, but which may be somewhat related.

[SeaMac]

@HLCPTR,

Aware of LIDAR but not the same system. RODAR is integral to the main rotor therefore requires nothing to be mounted externally on the fuselage. If EO capability could be added to the rotor tips then not even a gimbal mounted EO sensor would be required affording a clean fuselage and the inherent increase in aerodynamic and thus fuel efficiency. Development stagnation could be nothing more than sorting out payment to the multitude of current patent holders. It's always about money in the end, even something that could definitely save lives...

[whoknows idont]

Why would you want to incorporate it in the blade tips? The obvious answer would be to just bolt your magic device on top of the rotor head. Most of the above mentioned problems would be overcome.
I wonder why EC appears to never having followed up on their patent from 15 years ago. BTW, they called it ROSAR, synthetic aperture radar with rotating antennas.

[SeaMac]

@whoknows idont,

It's not me who wanted to put just the electro-optical sensors in the rotor blade tips, there's more than one patent for just that with the USPTO. With the integral to rotor radar and blade tip EO you would have both synthetic aperture capability along with HD day/night camera/IR/thermal imaging, all potentially combined on one screen providing the crew with the utmost in situational awareness. It is not magic it is technological reality with awarded US patents. I do not know why Eurocopter didn't continue with ROSAR, maybe it infringed on existing patents and they chose to stay out of litigation. My only question is why all of the patent holders and industry leaders have not made this technology available. I suspect it comes down to money, if in the 70's you designed a system and was awarded a patent -which it was- but for whatever reason stopped development you still own the patent so long as you kept it current. If say Raytheon, Airbus, Boeing or someone else wanted to continue development they have to buy the rights or pay royalties......all comes down to money. Then of course if Boeing ended up with the patent well then, there's no chance at all it'll be developed. Boeing IMHO is the embodiment of a truly evil corporation, but that's a whole other matter.

[whoknows idont]

What's the gain? At the tips you have to compensate for the variety of blade movement and for the means of that, exactly capture the blade tip movement. Otherwise get a pretty wobbly image. Seems terribly complicated, maybe impossible with 1970s technology.
On top of that, you have a much more exposed position, would need redesigned blades, tamper much more with the helicopters rotor system.
While you gain not one single rpm over the rotor head. So what's the unobvious angle here? :confused:

[AnFI]

OK I'll bite since I design RADAR stuff amongst other things.

A quick "back of the fag packet calculation" gives me the following:

Lynx rotor disc diameter (as an example): 12.8M
Lynx blade tip speed: 700 feet/sec = ~ 214M/S

Centripetal Acceleration = (v*v)/r = (214 * 214)/6.4 = 7155 M/S^2
i.e 70g constant acceleration.



Err , maybe need to get your cigarette packet checked

Is 7155m/s^2 ~= 70g ? (More like: 700g)


i can understand that valves might have an issue at 700g, but why would a chip care about being at 700g ?

[SeaMac]

@whoknows idont,

I'm sure the engineers and patent holders were hoping to gain 360* situational awareness and all-weather, day/night operational ability out of a rotorcraft platform. Personally I can think of one particular outfit that could significantly benefit from the technology......160th S.O.A.R. although they seem to do just fine without.

Computer software can stabilize virtually any image as for the rotor tip speed that too can be slowed and stabilized digitally so the image could very likely be HD.

I'm not the one driving this, just curious why with all the research and patents it's not made available. It just seems to me to offer so much in safety especially for SAR applications that the manufacturers would be clamoring to make it available.

[whoknows idont]

The rotor head also turns the full 360 degrees, just saying. I wonder, what the benefit of using the blade tips would be. Maybe the greater distance between the sensor and the rotational axis makes the picture so much better...
I also find it to be a quite intriguing question why this technology didn't cut the mustard yet. :confused:
Who knows, I don't.

[SeaMac]

@whoknows idont,

I would think you would get a better view from the rotor tips as compare to the rotor head, at least being able to view beneath the aircraft for a full 3D picture even back to the fuselage itself.

You and I both wonder why it hasn't been brought to market. I believe it was about 20 years ago and I remember reading an article in Rotor magazine about technology to make flying at low levels safer. It involved cameras located all about the craft, live wire detection systems and so forth and all made perfectly logical sense. The rotor itself offers a perfect antennae and EO platform providing a 3D 360* view.

It could also be a liability concern, one entity responsible for the rotor itself, another for the radar then yet another for EO but all contained within one blade. So who do you sue if something goes wrong and your aircraft turns into a land dart or the rotor lops someone's head off?

[whoknows idont]

So who do you sue if something goes wrong

Going by that logic, no safety enhancing feature / add-on device would have ever made it into serial production.

You and I both wonder why it hasn't been brought to market.

But then again, who are we to reassess the hypothetical prospects of this squib load technology? Feels like we hit a brick wall before we even started discussing this.
A kind of military explanation would go like this: The fact that it hasn't been done yet proofs that it doesn't make sense (only satisfactory if you are blessed enough not to care about explanations).
Any way, this discussion has been going in circles for a while... (no pun intended)

[SeaMac]

Shall I apply the rotor brake? :hmm:

[22clipper]

Half a life time ago ABC Austalia used to screen a program fronted by a Pom with a plum in her mouth called 'This week in Britain'. One memorable episode featured a Wessex with microwaves piped up the rotor mast to rotor blades modified as antennas. I recall a detailed image of London on a CRT in which the Thames was clearly visible.

How you could fiddle with a helo power plant to the extent that the main drive shaft out of the gearbox became a waveguide & still keep the machine air worthy is just awesom I reckon.

[SeaMac]

@22clipper,

IRRC you are referring to the Ferranti RODAR which is patented in the US!

[212man]

There will also be doppler shift to deal with, as the antenna is not fixed

I'm pretty sure that at 300,000,000 metres/second the relative effect of the rotor speed will be irrelevant ;)

[ion_berkley]

Quote:
Originally Posted by ion_berkley View Post
OK I'll bite since I design RADAR stuff amongst other things.

A quick "back of the fag packet calculation" gives me the following:

Lynx rotor disc diameter (as an example): 12.8M
Lynx blade tip speed: 700 feet/sec = ~ 214M/S

Centripetal Acceleration = (v*v)/r = (214 * 214)/6.4 = 7155 M/S^2
i.e 70g constant acceleration.

Err , maybe need to get your cigarette packet checked

Is 7155m/s^2 ~= 70g ? (More like: 700g)


i can understand that valves might have an issue at 700g, but why would a chip care about being at 700g ?

Excellent catch mate! What's a factor of 10 between friends!
You asked about acceleration and chips...well likely the chips themselves are not the weakest link, but I can only imagine that such cyclical stress would be very detrimental to reliability and lifetime. Whats trickier is keeping everything rigid and planar, bearing in mind all this technology is generally optimized for its electrical qualities rather than mechanical, unlike the composites and alloys used in blade construction, many of the components used in these types of circuits contain fine, hair line filaments of wire or resonating crystals internally for example. Just because R&D has worked out how to put a guidance system into an artillery shell, doesn't make that technology commodity, cheap, or even attractive. At the end of the day, whilst "cost is no obstacle" technologies had there place in the military of the 50's and 60's, thats not the case today.

As for patents, well I have a bunch. I doubt many of the protected technologies in them will ever see commercial success, but its a form of insurance policy when it all occasionally works out.

I think it boils down to this. If you really have an application that requires this level of RADAR functionality then you build it in the contemporary AESA style, conformal with the structure of the aircraft. I've got to believe that the material and mechanical technology that goes into blade design is already difficult enough that it would require enormous justification to add this type of complexity even before we consider how much harder it makes the job of the RADAR design team.

[SeaMac]

@ion berkley,

My only hope here is, with the exponential advances in computer, material, mechanical and electrical sciences that a system which could drastically improve helicopter operation safety isn't left to collect dust on a back shelf somewhere.

Other than obvious military applications I think such a system would benefit the HEMS and SAR industry tremendously.

You never know, there could be some prodigal wiz kids at MIT right now reading this thinking to themselves, "I've got the key to make this work".

Since any development I could find ceased some years back maybe it's time to revisit the concept?