The good old days!

This video has been featured on numerous rocket blogs and sites, and it is time I posted it here. From the mid-60's to mid-70's, the West Covina Model Rocket Society (WCMRS) was one of California's most active model rocket clubs, having over a hundred members. They even had their own designated launch site in a city park, which is unheard of nowadays. The video, from 1967, shows the club in action, and features things such as a "silo launched" scale model of a Titan, and an underwater launch (Yep, it can be done). Here's the link to the low-res version on YouTube:


A better version, with a 3 minute prelude about Robert Goddard, can be found here ("Junior Missilemen in Action").

I found a short article about the club, published in the Centuri American Rocketeer, Vol 3, No. 1:

(Click to enlarge)

So what happened to the West Covina Model Rocket Society? Well, it appears that they had some problems with starting fires in the park. After the third such incident, in 1974, the city banned rocket launches there and WCMRS faded from history. Yet another reminder that good things are easily lost.

Making sense of Geezer TARC...

As mentioned in a prior post, rain forced the early termination of the Geezer TARC launch, leaving both me and Duane with an unflown, untested entry. We decided to rectify that situation this past Saturday, and 10 AM found us setting up pads and gear at Pegasus. We were joined by a few unexpected flyers - Matt, a friend of former HARA member Woody Bevil, was already there at the field with his two daughters, and they had rockets. I had my trusty tripod low power pad and controller with me, so it was a foregone conclusion that those rockets would soon head up into the bright blue sky.

Ignition of the Gnome's motor (Click to enlarge).

Apogee Apprentice clears the rod on a B6-4
(Click to enlarge).

One of the young ladies was the first to fly - her Estes Gnome performed well on a 13mm 1/2 A motor, but required a little searching to find it in the tall weeds (Hopefully the city will mow Pegasus again sometime in October - the flora is getting a bit wild). Her sister was next, and an Estes B6-4 powered her Apogee Apprentice to a respectable altitude, after which it gracefully floated down to earth on a parachute. Matt had a very nice Semroc Omega, which flew twice in single-stage mode on C11-5's. They had a good day - 4 flights, with 3 perfect recoveries.

Semroc Omega on a C11-5 (Click to enlarge).

Omega under parachute (Click to enlarge).

Which is more than I can say for those of mine and Duane...

First up was the rocket Duane had flown at the Geezer TARC launch on September 14, this time loaded with an Aerotech reloadable E28-7. I had passed along a tip based on data I collected at the Geezer TARC launch, which was to lighten the rocket down from 447 grams and consider a different motor. He listened, as the rocket weighed in 19 grams lighter and the E28 had 6 more newton seconds total impulse. This made all the difference in the world - peak altitude was 815 feet, very close to the 800 foot goal. Quite a difference from the dismal 665 feet apogee from the previous Saturday. Unfortunately, the shock cord attachment pulled loose, causing the sustainer to tumble to the ground and the payload section to slowly descend under the parachute. It took about 10 minutes for Duane to locate the sustainer in the weeds; fortunately, there was no damage.

Duane's rocket clears the rail (Click to enlarge).

My turn was next. Heeding the lesson from last Saturday's fiasco, I had removed the kevlar protector from Oeuf and loaded conventional chute wadding. I did a very close check of the igniters in the two Quest D16-6 motors - this would be my very first composite motor cluster flight - and placed the model on the rail. The clips were connected, the count given, and Oeuf shot up the rail, riding two beautiful pillars of black smoke into the sky. I was relieved that both motors fired, but the relief turned to concern as it appeared that Oeuf had performed a little too well - the altimeter would report an apogee of 873 feet. Then concern turned to horror as the parachute failed to deploy. It dragged behind the rocket, fluttering enough to slow the rocket down to 26 feet per second - slow enough to result in no physical damage but fast enough to break the egg (which was wrapped in saran wrap this time). Inspection revealed that 3 shroud lines had ripped away from the Apogee nylon parachute, despite being reinforced with CA as per instructions.

Oeuf under composite cluster power! (Click to enlarge).

Duane and I were having serious recovery problems...

The final flight of the morning was Duane's unflown entry. It too was loaded with an Aerotech E28, and had the best altitude of all the flights - 793 feet, just 7 feet off the mark. This time the recovery system worked perfectly, making for a nice end to our hour long launch.

Duane's 2nd rocket starts its journey (Click to enlarge).

After the Geezer TARC launch, I was looking for a way to see if I could make sense of the data taken during the launch. As you may know, the peak altitude of a rocket is influenced by 3 primary factors - total weight, impulse of the motor, and the frontal area. There are other variables to consider, but these are the big three. I had no measurements of the rocket diameters, but I knew that they all ranged from the diameter of a TARC egg (1.8") to that of a BT-70 body tube (2.2"), resulting in a 50% variation in area. This is significant, but not factors of two or larger, so I figured I could ignore it for my simple analysis, which involved plotting peak altitude versus (total weight divided by motor impulse). I reckoned that the area variation would show up as scatter in the data points.

Here's the result:

Simple Geezer TARC altitude analysis (Click to enlarge).

Note the correlation - Vince's FrankenBertha comes in at a low 6.4 grams per newton-second, so it goes way too high, and Duane's boat tail rocket with 13.3 grams per newton-second comes in too low. There appears to be a sweet spot (highlighted by the cyan band) between 10.5 and 11.4 grams per newton-second that puts the rockets at the right altitude. And, as expected, there is scatter in the data, in part caused by the neglect of the variation in frontal areas. Still, it's somewhat informative, and may provide a good way to check the built TARC rockets to see if they are "in the zone" with regard to weight and motor choice.

I'm glad something useful came out of that rainy day and those broken eggs.

Would you believe a finless, air launched rocket?

Joe Barnard, honcho of BPS Space and master of finless, thrust vectoring flights, has undertaken a new project - an air launched finless rocket (which naturally looks like a missile, assuming you ignore the hot pink color) using a silo. He has posted a fun, excellent video on YouTube, which nicely illustrates the unforeseen engineer challenges that arise in an decently complex project. Joe never ceases to amaze me with his savvy and approach to solving problems!

Check it out:

Rain at high noon...

This past Saturday was the appointed date for this year's Geezer TARC competition. On Friday, the forecast did not look good, but Duane and I decided to wait until Saturday morning before making the weather call. At 7 AM Saturday morning, the radar showed rain all around us, and by 8 AM even Duane threw in the towel - the weather did not look like it was going to cooperate. I sent out a few "don't show up" messages to the folks I knew would be there, but Duane suggested we go down to the field to intercept anyone I missed that might show.

That decision had momentous consequences.

We found Patrick and Art at Pegasus East, with Patrick very eager to fly his 3D printed entry. Allen pulled up, and then Vince materialized with his Franken rockets - the pressure was on. Duane and I gave in to go fever, and we quickly set up the pad, controller, and table loaded with stuff amidst the occasional drop of rain. The sky did not look good, and my iPhone weather radar app showed the rain getting ever nearer, but there was no stopping this choo-choo. People were going to fly their rockets - weather be damned.

Patrick's rocket leaves the rail
(Photo by Patrick; Click to enlarge).

Patrick's model under parachute (Click to enlarge).

The flying began with Patrick. He was worried that his orange and blue 3D printed beauty might go a bit too high on the Aerotech E20-7, and he was right. His rocket shot past the altitude mark by a hundred feet, and caused us a bit of concern as it drifted across the road towards the Blue Origin rocket engine facility construction area. Fortunately, the model landed a bit to the south of the fence, so all was good, especially when a check showed an undamaged egg - qualified flight! I was pleased that Patrick flew the little used Perfectflite Firefly altimeter - it's small and light, and yields quite useful data when connected to the readout unit. According to the Firefly, Patrick's rocket reached 903 feet, had a max speed of 264 feet per second, took 7 seconds to reach apogee, descended at 17.2 feet per second (a bit slow - should be between 21 and 22 feet per second), and stayed aloft for 59.4 seconds. So this year's Geezer TARC started with a score of 168.

Vince's "FrankenSprint" gets going on an E12-6 (Photo by Patrick; Click to enlarge).

Vince was up next, flying a "FrankenSprint". His rocket was a Sprint XL with the nose cone replaced by an Estes Scrambler egg capsule - improvised to say the least. Powered by an Estes E12-6, his model hit 748 feet - 52 feet shy of the 800 foot mark - and stayed up for just over 59 seconds. This duration was about the same as that of Patrick's rocket, which went 155 feet higher. If you surmised that his parachute was too big, you would be right. Too large parachutes would plague both of Vince's flights this day. Sometimes a few calculations or simulations can be better than guessing, but his 117 score put him in the lead.

Duane's rocket starts its trek upward (Photo by Patrick; Click to enlarge).

Duane was number 3 - he loaded his rocket on the rail and gave the count. The Aerotech E30-7 sent the rocket skyward, but we could tell that he didn't make altitude. This was backed up by the very short duration of 35 seconds. After recovery, we checked the altimeter which beeped out a disappointing 665 feet, resulting in a 154 score. The Geezers were not doing so good.

Duane loads Ool on the rail as I look on (Photo by Patrick; Click to enlarge).

Then it was my turn. Ool was placed on the pad, and the count was given - but the igniter misfired. A replacement was stuck into the nozzle of the E12-6, and Duane reloaded the rocket on the rail. Another count was given, and Ool shot straight up into the increasingly gloomy sky. All seemed well until ejection, when it soon became apparent that my parachute was tangled up with the kevlar chute protector and shock cord. Ool plummeted to the ground, impacting with a sickening thud that foretold horrible things happening inside the payload section. A DQ - which was a darn shame, because Ool flew to 810 feet (the best altitude of the day), and even with the very short duration of 28.5 seconds, I would have ended up with 56 score. But a bad flight is a bad flight, and I cursed myself for not trusting my instinct to use normal chute wadding instead of the kevlar protection. I had seen too many instances of parachute failures when they were used by the TARC teams, and I should have heeded this knowledge. But I didn't, and paid the price.

Ool begins her ill-fated flight (Click to enlarge).

Ool doing the "dive of death" (Photo by Patrick; Click to enlarge).

And yes, Ool suffered quite a bit of damage - the body had failed under one fin which was hanging, another fin had a cracked edge, the body tube was crinkled near the end of the motor mount, and the top of the nose cone was bashed in. And, of course, there were egg guts all over the inside of the payload section. I ended up throwing away the Apogee egg protector, which was beyond cleaning; fortunately, the altimeter was shielded and survived unscathed. I am trying to repair the model, but alas, I fear she will never be the same.

Ool's flight profile from the PNUT altimeter (Click to enlarge).

We were now being subjected to sprinkles of rain - the weather was fast deteriorating. But Vince had to fly his second improvisation, this one being a Big Bertha topped by an egg capsule. FrankenBertha was powered by an Aerotech E15-7 - waaay too much motor, and this was proven when it sent her soaring to 1122 feet - 322 feet above the goal! Combine that with a very long duration of nearly 2 minutes, and you have the worst score of the day - a very, very bad 626.

Vince hooks up "FrankenBertha" (Photo by Patrick; Click to enlarge).

Now it was beginning to actually rain, so the launch was called - even though Duane and I still had another model to fly. Vince's 117 score was the best of the day, so we gave him the trophy and declared him the 2020 TARC Geezer. My parachute failure netted me the Skunk trophy, which appropriately enough has a Latin inscription of "Accidit Stercore"; I leave it to ya'll to look that up.

2020 Geezer TARC scores (Click to enlarge).

Vince triumphs! (Click to enlarge).

My Skunk (Click to enlarge).

And that, good readers, was this year's Geezer TARC. A new champion has risen from a pile of dismal scores, lousy weather, and the remains of an egg which died a horrible death.

Congrats Vince!

How much power do you really need?

The Geezer TARC flyoff is this weekend, and I am busy going over my final calculations before the event, making sure I have the proper descent rates with my chosen parachutes. I am also following a lot of activity over on the Contest Rockets group, where the discussions are focussing on the NRC, NAR's relatively new competition format. This got me to thinking about egg lofting and wondering if it would be possible to apply competition techniques to this year's TARC, given the relatively simple payload and design constraints. My two Geezer TARC models fly on E impulse, but could you get a single egg and altimeter to 800 feet with a D motor? A quick glance at the NAR records shows altitudes of over 600 meters (1968 feet) for this impulse class, so yes, it should be doable - if I was top of the line contest rocketeer, which I ain't.

But I did get inspired enough to fire up OpenRocket to see if I could come up with a workable design using off-the-shelf parts. Wonder of wonders, I found it surprisingly easy to do so. Meet Eggsperimental!

A visual rendering of Eggsperimental (Click to enlarge).

Eggsperimental is a BT-50 based, D12 powered model that meets all the TARC requirements. It consists of a light weight Apogee clear plastic egg capsule with padding for the egg and a Firefly altimeter in the shoulder, a long piece of BT-50 body tube, an engine hook, three balsa fins, and 2 Apogee 3D printed rail guides (which I have decided to replace with an Apogee egglofter fly away rail guide to reduce drag even more). Weighing just 146 grams with a D12-7 motor, it only requires a 12" Mylar parachute to bring it safely back to earth. OpenRocket says this puppy should break 1000 feet, which gives me plenty of margin for additional weight (i.e., nice paint job).

Apogee egg capsule and padding (Click to enlarge).

Eggsperimental in the OpenRocket design screen (Click to enlarge).

So what are the pro's and cons of this design?

Pro's:

• Very economical
• Standard model rocket construction techniques - assembles like an Estes Alpha!
• Easy to construct, finish, and paint
• Uses a relatively cheap black powder motor that can be bought locally

Cons:

• Not very robust - may not survive many flights (but easy to build copies)
• Would have to come up with a way to add weight to lower altitude (body tube segment glued to egg capsule capable of holding sand, clay, or bb's - not hard to do)
• Fly away rail guides may malfunction (I've seen this happen)

I'm planning to construct one soon, but won't have it by Geezer TARC. However, I should have it built and ready to fly by the time the teams start practicing. If it works, it'll make the other rockets look like big pigs.

I kinda like that thought..