Greg Smith's quest to spend even more money on rocket science...
As of 8/9/08 I'm now level 3 certified. Yay. Now aspire to become a Tripoli TAP member for the San Diego club so I'm working to increase my experience and augment my rocketry résumé.
For my 2008 birthday present my parents kicked in half of the cost of an Aerotech M1939 motor. They drove all the way out from Cochise, AZ for last year's Plaster Blaster which was completely blown out by wind. We made several other attempts to link up in the ensuing year to get that motor flown. Mother Nature cooperated this weekend and, on Sunday, I was finally able to launch the beast. I used my L3 7.5" Nike Smoke as I'd actually built and reinforced it for this particular motor. Here's a liftoff photo:
Some might notice that, much to my chagrin, the shot is clearly back-focused. I'm certain that I had a clean focus lock on the rocket before flight so I'm not sure what went wrong here. In any event you get the idea and I attained just under 10,000' on this impressive flight. For some reason the Parrot2 altimeter did not record any data so I only have the AltAcc graph and summary:
I dedicated this flight to my parents 'cause they rock! Again Roy and I had to walk north over a mile to get this 50 pound beast back. We were exhausted! I can honestly say that this was THE best launch of my life and I'd like to thank my parents, Frank Hermes, my friend Kristine, and Mother Nature for that!
I'd planned many flights over the weekend but prep and recovery took much longer than expected so I only had three flights total. The middle flight was on Saturday night and my new .38 Spatial was one of 21 rockets launched simultaneously on the new CTI H123 Skidmark motor. This propellant formulation isn't new but, with recent California State Fire Marshall approval, these impressive motors pretty much dominated the launch. They employ particles of titanium metal in the propellant that burn bright white/orange and pop loudly. In aggregate a single Skidmark motor yields thousands of these sparks and, as a result, roars loudly well above a normal motor's decibel level. Here's a video of all 21 rockets launching at once (well 20 if you exclude Frank's entry which failed to ignite due to my error):
Here's another of the seven including .38 Spatial (third from the right):
And here's a photo of my design isolated with some nice dusk lighting:
This launch was the clear crowd pleaser of the weekend. John Bowman did an excellent job of coordinating the event and the crowd loved it!
Frank and I conducted the successful M750 drag race just after 10AM on Saturday. Here's a video covering prep and flight:
Here's a liftoff photo verifying Frank Hermes' clear victory in this M750 drag race:
The flights were quick, impressive, and invisible after the smoke charges burned out. I should also note that frank topped 21,000' and, in a separate flight, Mark Clauson attained his level 3 AND topped 22,000' for a club record! Here's his video of the race:
Here's my Parrot2 Altimeter graph and summary:
Here's the way too simplistic summary from the G-Wiz LCX:
I'm likely to sell the LCX and buy the HCX at some point because that's just not enough data to bother! Note the lack of calibration 'cause this is the first time I'd used the device and failed to RTFM. Therefore the acceleration and velocity numbers are wrong. The barometric sensor does not require calibration so the altitude number should be correct. The average of 20,788' and 19,635' is 20,212'. Yay! President's Challenge mission accomplished.
I'd planned to use my GPS transmitter for this flight but realized the fragility of the antenna and the carbon fiber exterior of Em-Sem-Fity was guaranteed to insulate the device from satellites. In the end I used my trusty radio tracker system and walked right up to the rocket roughly 2+ miles north of the launch site. The rocket was entirely intact and dual deploy appeared to have worked perfectly:
While cleaning up the photo sequence of the drag race I noticed something interesting... my flame clearly appears weaker than Frank's. I normalized our two flights using Photoshop and added ruler lines for comparison:
In prepping my motor I heard rumor that I shouldn't use the disposable forward seal disc. I checked with Gary Rosenfield and Karl Baumann from Aerotech (conveniently in attendance at the launch) and Karl was surprised that I had a disposable seal disc. He asked for the lot number but now I only have my nozzle pack serial: 071007. Unfortunately I disposed of the four grain boxes. In any event Karl commented that this M750 reload must have been from an early production batch. As such I must assume that a) my reload was in the neighborhood of 2+ years old and b) there could be an aging effect on this motor that reduced its total impulse and/or average thrust. I'll follow up with Gary and request his input.
Frank challenged me to a rematch at Plaster Blaster 2010. If we do this I'm going to request two sequential serial number reloads built in the same recent lot. For now I'm elated that I exceeded 20,000 feet for a new personal altitude record.
[Disclaimer: I assume no responsibility for use or misuse of this information. It's available elsewhere on the Internet and I'm simply sharing my engineering interpretation of that information. Use these materials with great caution. Do not mix reactants until just before use. Do not mix or ignite them anywhere near ignition sources or flammable materials, respectively. Do not look directly at the reaction as harmful UV radiation is emitted. Be careful!]
If you watch Mythbusters then you'll likely have seen their experiments involving thermite. According to Wikipedia Hans Goldschmidt discovered and patented this thermite reaction in 1893 and used it to both cut and weld metal. These powdered mixtures require very high ignition temperatures (2000˚F) but then burn at 4,500˚F swapping oxygen, producing molten metal, and releasing a bunch 'o' heat and UV radiation. Common reactants include elemental aluminum or magnesium with metal oxides like copper (II) oxide (cupric oxide) or iron (III) oxide (ferric oxide).
Many folks in high-power rocketry are successfully using thermite as a source of instant ignition of even the largest rocket motors using a guideline of roughly 1 g thermite per 1000 N•s of total impulse. I'm intrigued both by the reaction itself and its utility in this hobby so I decided to give it a try. I ordered 1 pound each of aluminum powder, cupric oxide, and ferric oxide online. I'm quite certain I overpaid as well so you should definitely compare prices on the Internet(s). :) I was finally able to use my chemical engineering degree and calculated the appropriate mass ratio of the reactants using stoichiometry and atomic and molecular weights. For the aluminum + ferric oxide reaction it's:
Fe2O3 + 2Al → 2Fe + Al2O3 + heat + UV
2 moles of Al = 26.98 g/mol * 2 moles = 53.96 g
1 mole of Fe2O3 = 159.69 g/mol * 1 mole = 159.69 g
So the mass/weight ratio is almost exactly 1:3 Al:Fe2O3
I set up my video camera intending to share the clips here but the ignitions were so fast that they only show up on about 4 frames at 30 frames per second. As such I've simply grabbed the key frames and assembled sequences for both tests. This camera method also eliminated the need to directly observe the reaction although the emitted UV might have improved my tan a bit. Here a single electric match ignites 0.5 grams of a molar ratio of ferric oxide + aluminum powder thermite:
Ignition was fairly rapid but continued to sputter for about 30 seconds afterward. In this second experiment I again used a single electric match to ignite 0.5 grams of a molar ratio of cupric oxide + aluminum powder thermite:
This second combination appeared to be far more energetic and burned to completion without sputtering. Most folks have been using this cupric oxide+Al combination but I wanted to try the classic ferric oxide+Al combination as well. It's clear that cupric oxide works way better so I now have my empirical answer. Again... exercise caution!!
Some might notice that, much to my chagrin, the shot is clearly back-focused. I'm certain that I had a clean focus lock on the rocket before flight so I'm not sure what went wrong here. In any event you get the idea and I attained just under 10,000' on this impressive flight. For some reason the Parrot2 altimeter did not record any data so I only have the AltAcc graph and summary:
