Verifying BC

[Ballisticboy]

Not so. The table below shows that Doppler radar can only provide four of the many aerodynamic coefficients. The ARL Spark Range (or equivalent) is needed to get them all.



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Sorry, but while you may think that in the US, for years we have been getting much more data than that from radar tracks, along with some other techniques, without the use of spark ranges which we don't have. Otherwise, according to the papers you quote, we would not be able to produce fire control data let alone sixdof data which we do when needed.

 

[Berger.Fan222]

Sorry, but while you may think that in the US, for years we have been getting much more data than that from radar tracks, along with some other techniques, without the use of spark ranges which we don't have. Otherwise, according to the papers you quote, we would not be able to produce fire control data let alone sixdof data which we do when needed.

Who is "we"? What country knows more about ballistics than the guys at ARL?

One can also estimate the aerodynamic coefficients with various theoretical models. However, these modelling approaches don't tend to be as accurate as spark range measurements.

There are approaches which essentially perform a guess and check, starting with the theoretical aero coefficients, running a 6DOF model, and tweaking the aero coefficients to obtain the best possible match with radar data. But these approaches are overconstrained - different possible combinations of aero coefficients can give the same radar data, so the aero coefficients are not really uniquely determined.

Of course, I'd be happy to look anything up that you can cite in the open literature supporting your claims. Of course you can't back up your BS with citations. National security and what not.

 

[Ballisticboy]

Who is "we"? What country knows more about ballistics than the guys at ARL?

One can also estimate the aerodynamic coefficients with various theoretical models. However, these modelling approaches don't tend to be as accurate as spark range measurements.

There are approaches which essentially perform a guess and check, starting with the theoretical aero coefficients, running a 6DOF model, and tweaking the aero coefficients to obtain the best possible match with radar data. But these approaches are overconstrained - different possible combinations of aero coefficients can give the same radar data, so the aero coefficients are not really uniquely determined.

Of course, I'd be happy to look anything up that you can cite in the open literature supporting your claims. Of course you can't back up your BS with citations. National security and what not.

The papers you quote were not written by the experts in ballistics at BRL such as Murphy, McCoy or Lieske, all of whom I knew and worked with back in the 80's, and who I am sure would not agree with you now. The data obtainable from Doppler radar quoted in the table you presented appears to be for a fixed head Doppler system only, a totally different beast to the proper Doppler tracking radar which has potential for producing much more information at higher tracking frequencies. In addition there is the Multi Receptor Doppler Radar (MRDR) system which is a kind of Doppler spark range being able to measure yaw and yaw rates. In theory MRDR, can produce all the data required without a tracking radar though I do not think it has ever been used in this way (papers have been presented at the International Ballistics Symposium). There is also flight follower from which much valuable information can be obtained, particularly for bullets (which have already been successfully tracked) due to the much higher resolution than a spark range can produce. There is plenty of information on the internet for flight follower.
Spark ranges are fine if you have one and personnel with the appropriate knowledge and experience to use it, such as Dupuis, though they do have resolution limitations for small arms. Many countries do not have spark ranges so different methods have been developed and used successfully.
So while a full sixdof set may require some additional information or intuitive knowledge (the different possible coefficient combinations you mention are easily dismissed as unrealistic in the vast majority of cases I have encountered) other than a full tracking radar set, a vast amount more information than just drag and spin damping is available if the system is used properly.

 

[JRS]

WOW As if actual BC is really that important

Good marketing is a money making tool.