[RocketsNW] Balls17 personal launch report

[kmcgoffin at worldaccessnet.com]

Heh heh.  I usually figure a Cd of 0.8 to 1.1 for most of my rockets. 
Underachiever in Cd reduction indeed!

Last year I tried to match actual altitude records to Cd estimates in the
approximate Fehskins-Malewicki equations.  Kept getting Cd numbers under
0.08.....that pretty much told me that the approximate equations were, uh,
approximate.  ;-)

At least now you know what the FAA newbie bunch think Cd should be on NASA
rockets.  Now we just have to make them understand that hobby rockets
aren't polished to perfection.  Except mine, of course:  All those bugs
stuck in the paint, hey, they're "precisely positioned surface turbulent
flow layer inducers."

Oh, and make sure the FAA newbies know we don't use "NASA micro-fins"
either. LOL

+McG+
(Apologies to Dave Proffitt)



> Balls17 was a mixed-bag for me this year --- great in some ways, very
> disappointing in others.
>  
> It was my 6th launch on the Black Rock playa, and my first trip to Balls.
> The weather was the best I have seen down there: Thursday afternoon was
> windy when we arrived, but Friday and Saturday were spectacularly
> beautiful.... moderate temperature, plenty of sun, and no wind, dust
> storms, or ice in the morning. There were lots of really impressive
> projects there, including an all aluminum hybrid rocket with a 14.9 sec
> burn time and something like P (?) impulse. There a large number of flight
> failures, mostly CATO's, and some of them were quite spectacular. Oregon
> was well-represented, and there were many flyers from all over the US and
> other parts of the world. Vending was great (What's-Up Rocketry was
> well-stocked and really customer-oriented). I got a kick out of the cannon
> on Saturday evening --- it was firing 12-lb bowling balls stuffed with
> what appeared to be red propellant.
>  
> My flying buddy, Randy Steck, got his L3 cert done, flying his 4" dia
> "Cinqieme" rocket (it means 5th, in French, as in fifth rocket). He was
> first guy to fly at the launch on Friday, just before noon, on an M1315,
> and he had a nice straight boost, but his main chute came out at apogee,
> so the cert wasn't quite there. Not to be deterred, he fixed the problem,
> bought another reload and flew it again on Saturday morning, the first
> flight of that day too, and successfully got his L3. Peak altitude was the
> same in both flights, at just under 15k ft. Congrats to Randy!
>  
> For my Triple Threat 3-stage N-N-M project things weren't so smooth.
> Because my planned burn-time was 16 seconds, I was one of three lucky
> flyers to catch the attention of the FAA Brain Trust in Washington DC,
> just a few days before the launch, and their flight sim showed that I was
> in danger of breaking the 100k waiver. You would think it would be quite a
> stretch to get from my 75k simulation to their 100k, but as it turns out,
> it is just amazing how high your rocket can actually go if your
> Coefficient of Drag (Cd) is only 0.2!  Now, according to Rocksim my Cd is
> a measly 0.5 on the sustainer, and 0.8 for the big honking fins on the
> first booster, so I'm clearly an underachiever in reducing drag. If I
> could achieve the superior Cd numbers that the FAA did, I could reach my
> 95k ft goal with only an H motor. Think of the possibilities! Think of the
> money savings!
>  
> Anywho, the entire Tripoli BOD and the Balls launch director got into it,
> and on Wednesday the emails were flying all over the place, with me
> spending much of my time that day re-running simulations and emailing more
> and more data, instead of getting ready to leave, as planned. We left
> late, and I forgot a bunch of stuff, which was irritating, but we still
> had a good trip down to Nevada.
>  
> Upon arriving at the launch site, I got the word that my 3-stage flight
> was officially nixed. So I spent the rest of Thursday and all day Friday
> figuring out whether and how to still fly 2-stage. Being designed for
> 3-stage minimum-diameter flight, my rocket is complex, so it isn't easy to
> change its configuration on moment's notice and go through TRA BOD
> approval again. To make it worse, we needed to leave the playa by 4pm on
> Saturday to get back home for some important stuff on Sunday. It would
> have been relatively easy to fly it as a 3-stage boosted-dart on the same
> 1st and 2nd booster motors, but that isn't very interesting for me
> (essentially that's what I already did in 2006 at XPRS), and plus it would
> waste $1700 worth of propellant that I would just "have to" buy again next
> year. So I was leaning toward being a spectator on Saturday. However, at
> 9:30 pm I got a call from Mark Clark (the Balls launch director) on Gabe's
> sat-phone that I had the green light to fly my original N4000 to N2000 to
> M1400 configuration.
>  
> After that, it was off to the races to do a full day's worth of rocket
> prep on Saturday morning. I had planned to fly it first thing on Saturday
> morning, so that I would have the rest of the day to find my sustainer and
> enjoy watching the other projects. Instead I spent Saturday building my
> motors, assembling the recovery system, overcoming the usual last-minute
> glitches, etc. and finally had the rocket on the pad at 4:30, already past
> our 4:00 planned time to leave the launch. After waiting for Fred and the
> Hardtail team to push the button on their 2-stage Nike project loaded up
> next door on John Lyngdal's tower (unfortunately it was a really
> impressive CATO, due to a motor casing failure at the snap ring groove), I
> climbed the tower to arm all the electronics at T-minus-15 minutes before
> the 5pm close of the 100k ft waiver. After flipping on switches I
> discovered that the DG Control was reporting an open circuit in one of the
> pyro channels. No matter how many times I tried arming the DGC, it still
> said the same thing. With only 10 minutes left in the waiver, I knew I was
> sunk for the day, and sunk for the launch. So with great regret I scrubbed
> the mission.
>  
> Upon pulling the rocket apart back at camp I discovered a break in the
> 8-conductor tape wire in the sustainer fin can, where it goes past the
> motor's aft closure. Two of these circuits control staging separation
> (primary and backup), one ignites the motor, and the last one reports
> separation status to the Beeline GPS transmitter. I found a break in the
> motor ignition circuit and in the primary staging circuit, so the flight
> was definitely hosed. If I had found this problem first thing Saturday
> morning, as planned (before the FAA got involved and "added value"), I
> could have fixed it and still flown by mid-morning, but with only 10
> minutes left in the waiver I was out of luck. So we packed it up and
> headed home.
>  
> I do have to say that the Tripoli BOD and the Balls launch organizers
> really tried hard to remedy a situation that was beyond their control and
> sprung on us late in the game, and they put in a lot of time trying to
> straighten it out. They really earned their "pay" on this one (i.e. lots
> of work for no money), and I was impressed that they didn't just say "oh
> well", and blow it off. My hat's off to them. I hope they can help educate
> the new guys down at the FAA, and get the TRA 60-sec burn-time agreement
> documented so we don't have to go through this again in the future. I also
> really appreciated Kimberly Harms loaning me the Jumbo launch pad and the
> Team Hardtail guys for hauling it down there and back for me. Fred and
> Mikey and the gang were great too, for loaning me nuts and bolts and misc
> stuff to try to get a 2-stage flight to happen.
>  
> I'm going to give it another try next year. But it better fly then, cuz
> I'm getting tired of driving all the way to Black Rock only to spend the
> time all stressed-out solving more problems! The work-to-fun ratio was
> definitely out of whack this year.
>  
> --- Adrian
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