PeterAlway
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I was working on an article about the Astrobee 200, whcih has a Nike booster for a first stage. And I my source material was contradictory about its performance. One illustration gave its designation as 2.5-DS-59,000, meaning it had a duration of 2.5 seconds, burned double-base solid propellant, and had a thrust of 59,000 pounds. But other sources gave a duration of 3.5 seconds. I decided to look through all of my binders for thrust, burn duration, and total impulse data from various sources. I thought I'd also make note of the length and diameter of the motor given in various sources.
I ended up finding two dozen sources that gave some fraction of that information. Only two of them were drawings by model rocketeers. The rest were drawing or text sources by NASA, the Army, Air Force, contractors, or technical journals. And the wide variations were pretty enlightening.
First, the physical dimensions, because that's what matters to modelers. Some years ago, someone posted a bunch of discrepancies in the length of the Nike booster motor in my drawings. Of the 15 values given, nine were in the range of 134.75"-135" long. The Army's Nike-Ajax manual gave a length of 136", and the NASA Goddard blueprint of the Nike-Tomahawk explicityl gave 132.7". Two sources I had used im my drawings gave overall nike stage lengths, with an adapter length to be subtracted to give the motor length. The University of Michigan's Nike Deacon drawing gave a motor length of 131.0". On inspecting the drawing and photos, I could see that the adapter was not that long--the dimension on the drawing was in error. A similar error showed up in the Model Rocketry Magazine article I used when I drew the Nike-Apache. It showed the Nike motor to be 138" long.
One technical journal article showed a single-stage Nike rocket with a motor 124.75 long--pretty obviously a simple typo.
Diameters are interesting, too. Usually source give the main diameter as 16.5, and a forward flange 17.5" in diameter. But reputable sources give a range of numbers. 16.2"-16.466 for the main diameter, and 17.2 to 17.572 for the flange. A whole can of worms!
I'll be sorting out that information at some point to figure out how to correct my drawings.
Nike performance figures are a whole nother can of worms! The first problem is one of defining a motor's burn duration, Here is an illustration to show the tail-off of a Nike motor, based on thrust-vs-time data I found in some documents about the Air Force's Honest John-Nike-Nike-Hydac. One document gave a dozen or two thrust values at different times--presumably data from a static test of a motor:
Note that the usual thrust duration given for the motor is 3.5 seconds, but this document gave a duration of 3.54 seconds. Some sources suggest that the duration should be measured to the point where thrust drops to 1/2 its full value, at about 3.2 seconds. You find average thrust by dividing the total impuls of the motor by the duration, so duration affects the average thrust number.
If this thrust curve is typical of all Nike motors, then the total impulse of the Nike motor is 132,000 lb-seconds, making it an S motor (the document also give an explicit value of about 132,000 lb-sec, agreeing with my calculation from the data points). If you use a duration of 3.5 seconds (by far the most comon value given), the average thrust is 37,700 lb.
But...every single other source gives an average thrust for the Nike motor of at least 42,500 lb. Either This was a wimpy motor test, or the thrust is being averaged over a shorter time (3.105 seconds works). Either is reasonably possible. Double-base propellants burned at a rate that was notoriously temperature sensitive. Several WW II era rockets had extra nozzles with burst diaphragms, so that if the moter were literally hot, so that it burned faster, the extra burning rate would provide extra thrust rather than blowing up the rocket.
One NASA source--an older version of the online NASA Wallops sounding rocket reference manual, gave a total impulse of 146,540 lb-sec (no I don't trust all those digits!) for the Nike motor, compared to 132,000 from the Air Force document. In "Rockets of the World" I used thrust and duration values from NASA documents that gave a much higher figure (I don't have that number handy--I only have notes from sources more reliable than me, but I did check that they came from a NASA document).
I will mention that the Total impulse values for the Nike range from 131,975 lb-s (the implied precision of that number is nuts!) up to 170,450 lb-s (calculated from a thrust and duration given in a NASA source that probably gave a maximum thrust, so I wouldn't trust the number.
The point, if I have one, is that reputable sources often don't agree, and why they disagree is really just a matter of speculation. Fortunately, we're all just hobbyists, so it really doesn't matter all that much whether the Nike was an S motor or a T motor, and whether it was 16.238" in diameter or 16.44 inches in diameter.
I ended up finding two dozen sources that gave some fraction of that information. Only two of them were drawings by model rocketeers. The rest were drawing or text sources by NASA, the Army, Air Force, contractors, or technical journals. And the wide variations were pretty enlightening.
First, the physical dimensions, because that's what matters to modelers. Some years ago, someone posted a bunch of discrepancies in the length of the Nike booster motor in my drawings. Of the 15 values given, nine were in the range of 134.75"-135" long. The Army's Nike-Ajax manual gave a length of 136", and the NASA Goddard blueprint of the Nike-Tomahawk explicityl gave 132.7". Two sources I had used im my drawings gave overall nike stage lengths, with an adapter length to be subtracted to give the motor length. The University of Michigan's Nike Deacon drawing gave a motor length of 131.0". On inspecting the drawing and photos, I could see that the adapter was not that long--the dimension on the drawing was in error. A similar error showed up in the Model Rocketry Magazine article I used when I drew the Nike-Apache. It showed the Nike motor to be 138" long.
One technical journal article showed a single-stage Nike rocket with a motor 124.75 long--pretty obviously a simple typo.
Diameters are interesting, too. Usually source give the main diameter as 16.5, and a forward flange 17.5" in diameter. But reputable sources give a range of numbers. 16.2"-16.466 for the main diameter, and 17.2 to 17.572 for the flange. A whole can of worms!
I'll be sorting out that information at some point to figure out how to correct my drawings.
Nike performance figures are a whole nother can of worms! The first problem is one of defining a motor's burn duration, Here is an illustration to show the tail-off of a Nike motor, based on thrust-vs-time data I found in some documents about the Air Force's Honest John-Nike-Nike-Hydac. One document gave a dozen or two thrust values at different times--presumably data from a static test of a motor:
Note that the usual thrust duration given for the motor is 3.5 seconds, but this document gave a duration of 3.54 seconds. Some sources suggest that the duration should be measured to the point where thrust drops to 1/2 its full value, at about 3.2 seconds. You find average thrust by dividing the total impuls of the motor by the duration, so duration affects the average thrust number.
If this thrust curve is typical of all Nike motors, then the total impulse of the Nike motor is 132,000 lb-seconds, making it an S motor (the document also give an explicit value of about 132,000 lb-sec, agreeing with my calculation from the data points). If you use a duration of 3.5 seconds (by far the most comon value given), the average thrust is 37,700 lb.
But...every single other source gives an average thrust for the Nike motor of at least 42,500 lb. Either This was a wimpy motor test, or the thrust is being averaged over a shorter time (3.105 seconds works). Either is reasonably possible. Double-base propellants burned at a rate that was notoriously temperature sensitive. Several WW II era rockets had extra nozzles with burst diaphragms, so that if the moter were literally hot, so that it burned faster, the extra burning rate would provide extra thrust rather than blowing up the rocket.
One NASA source--an older version of the online NASA Wallops sounding rocket reference manual, gave a total impulse of 146,540 lb-sec (no I don't trust all those digits!) for the Nike motor, compared to 132,000 from the Air Force document. In "Rockets of the World" I used thrust and duration values from NASA documents that gave a much higher figure (I don't have that number handy--I only have notes from sources more reliable than me, but I did check that they came from a NASA document).
I will mention that the Total impulse values for the Nike range from 131,975 lb-s (the implied precision of that number is nuts!) up to 170,450 lb-s (calculated from a thrust and duration given in a NASA source that probably gave a maximum thrust, so I wouldn't trust the number.
The point, if I have one, is that reputable sources often don't agree, and why they disagree is really just a matter of speculation. Fortunately, we're all just hobbyists, so it really doesn't matter all that much whether the Nike was an S motor or a T motor, and whether it was 16.238" in diameter or 16.44 inches in diameter.
