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Launch Statsby Jack Hagerty, LUNAR #002Every time you fly a rocket with LUNAR, you have to fill out a flight card. After the flight the RSO pulls the card off of the clip board and carefully stores them in the pocket of the Orange Vest. Did you ever wonder what happens to them after that? For quite a while, nothing. They were bundled up by month, but no one did anything with them and they started piling up at the various club officers' houses.To try and get some useful information out of this mess, last year I started doing a simple sort on them by motor size to get a few crude statistics. The total number of flights and the total number of motors should be self explanatory. It's a good bet that there will always be more motors than flights since we've never yet had a launch where someone didn't fly a multistage or cluster model. The "Total Impulse Expended" line needs a little explanation, though. I'm sure you all know that the letter in the first position of your motor designation (e.g., the "C" in a "C6-5") represents the total impulse of the motor. Impulse is the measure of the amount of "push" the motor gives to your model. It has the units of "Newton-seconds" (Nt-s) which is the metric unit for force (Newton, which is about ¼ pound) times the number of seconds which that force is applied. For example, the C6 motor puts out an average thrust of 6 Nt (which is what the "6" represents) for 1½ seconds so it has an impulse of 9 Nt-s. The National Association of Rocketry has defined the different motor classes as "A" for motors up to 2½ Nt-s, "B" from there up to 5 Nt-s, "C" up to 10 Nt-s and so on. Notice that the upper limit doubles with each class. It works the other way, too. Below "A" there are two recognized classes of 1/4A (zero through 5/8 Nt-s) and 1/2A (from there to 1 1/4 Nt-s). To get the "Total Impulse" number, I simply took the total number of motors in each impulse class and multiplied by the upper limit of that class (e.g., the total number of "C" motors times 10) then added them all up. Of course, this number would be way too high since not all motors in a certain impulse class are at the top limit. Some are notoriously low such as the Aerotech E25 (at 22 Nt-s that's only 10% above the top of the "D" range) or the FSI F100 (at 50 Nt-s it's barely above an "E"). For this reason, I took the calculated total and multiplied by 75%. There's no scientific reason behind the 75% other than it just "felt" right. If anyone out there can come up with a better industry average, please contact me and I'll update these tables. Finally, the "Average Impulse" is simply the total impulse divided by the total number of motors. This gives us some idea as to how "powerful" a day we had! Here are the results of the past year's worth of launches. Note that there is a big hole for four months last summer. For a couple of these I had to leave the launch early and no one collected the cards and for the others I was out of town. Still, this should give you some idea of how things are going. From now on, when we print these in the newsletter or web page, it will be just a little summary box with the totals in it, not a whole article like this. April, 1996
Total Flights: 113
Rob Powers conducted a great contest launch in April, but the Sport Range was pretty busy, too. The motor count does NOT include any of the contest flights. May, 1996
Total Flights: 94
Fewer fliers out in May, but part of that had to do with the high winds this month. You'll notice that all of the drop-off is with the larger motors ("C" and above) except for the same number of "H" motors (and that's probably the same two guys!). This makes sense if you think that you wouldn't want to be chasing models downwind into the Concannon vineyards! Also, the number of flights and motors used is almost identical, showing that only two fliers risked two-staged flights that day. June, 1996
Total Flights: 110
A turnaround from May. The weather was perfect for flying (sunny and calm) so the number of flights jumped back to about the same at April. But look at the number of motors used! While we did have quite a few cluster and multi-stage flights, it's not quite as dramatic as it seems. Most of that "A" motor count came from Chris Burgess whose "Li'l Wild Thing" consumed 7 A10's with each flight and he flew it three times! Taking his 21 motors out of the "A" column shows that everyone was flying bigger stuff with the three smallest motor sizes showing sharp decreases while "C" and above used a lot more. July, August, September, October, 1996 No flight cards available November, 1996
Total Flights: 179
This was a HUGE launch by the number of flights, and it almost didn't happen. The forecast was for a big storm to hit by mid morning and Warren Massey called me at 6:45 to get an executive decision as to whether or not to launch (he puts the message on the answering machine at 7:00). Since there was no wind at the time, we went ahead. While it was overcast and (towards the end) windy all morning, we still had a huge turnout and everyone had a good time. If you compare the number of motors to launches you'll see that we had a large number of multi-stage and cluster flights. All together there were five 2-stage flights, one 3-stage flight, five 2-engine clusters, four 3-engine clusters and two cluster/staged flights: one with three engines in the booster and one with four! The most ambitious was an H-to-G two stage flight (which still stayed within our impulse limit since it was a very low-end "H") but it core-sampled spectacularly when the upper stage didn't ignite. December, 1996 Rained out. January, 1997
Total Flights: 73
This is a launch that almost didn't happen. Like the previous two months, the weather was rotten. While there was no rain to worry about, the wind was brisk and the fog gave us a ceiling of under 200' during setup. In fact, the mist in the air gave a stinging quality to the wind. We couldn't activate our waiver under these conditions, of course, which limited us to 1 lb launch weights. After the equipment was up, I called for a vote of the dozen or so hearty souls who had braved the elements to ask if they were willing to still fly even if they would be limited to "C" motors at first. The answer was a unanimous "yes!" Rocket fiends in need of a fix are not always the most rational... Those who stuck it out, though, were rewarded by some marginally improved conditions. The fog lifted to nearly 1,000' and the wind died down some. A couple of brave flyers launched 2 stage models (one with A's and one with C's) and Paul Magid even flew his scratch-built Astron Ranger replica on a three "C" engine cluster. We even worked our way up to a few "F" motor flights that were under a pound and had a max altitude of under 1,000'. February, 1997
Total Flights: 150
What a difference a month makes! In comparison to January's almost Arctic conditions, February had very mild temperatures and light winds. We had a huge turn out, and everyone was trying to fly right up to the end when we had to shut it down at 1 PM. More interestingly, this seemed to be a grownup's launch. The motors ran to the high end of the impulse range and gave us the highest average impulse since I started compiling these records! March, 1997
Total Flights: 166
Almost an exact copy of last month's launch, right down to the mild temps and kicking people out at 1 PM! Just slightly more flights and more motors, but they tended towards the smaller end, so while the Total Impulse was up 6%, the total number of motors was up 16%, thus the Average Impulse was a bit lower. April, 1997
Total Flights: 176
A really good launch that came within three flights of tying the largest number of flights record from last November. There was a big increase in the number of low end motors used (mostly by a large Indian Guide group who was flying with us) but a concurrent drop off towards the top end. Another interesting observation is that these were almost ALL single motor flights! I flew my old Astron Ranger on it's 25 year anniversary flight (I built in March, 1972!) on three A6-4's and one person flew a full-up Commanche 3. Other than that, there were only two 2-stage flights. That lone 1/2A was flown by Royce Longacre who was de-bugging his flexwing glider. The reason for the odd motor number count is that three people didn't put down a motor on their flight cards and somehow slipped it past the RSO (tsk, tsk). They were all lower end Estes kits that couldn't have flown on anything more than a "C" at most, so it wouldn't have altered our Impulse totals by more than about 2%. =================== This is a good start, I can hardly wait to see how the upcoming year compares!
Copyright © 1997 by LUNAR, All rights reserved. Information date: May 17, 1997 lk |