Sunday, May 31, 2015

Weight is everything...

As I begin construction of my first Geezer TARC rocket, I find myself confronted by a sobering aspect of this year's competition... Weight.

The TARC rules specify that the rocket may weigh no more than 650 grams fully loaded on the pad. This means that you have to pack 2 eggs, the protection for those eggs, altimeter, parachute, wadding (or dog barf or baffle), shock cord, and the motor(s) into a rocket that will loft those eggs to 850 feet and bring them safely to the ground at a descent rate of around 21 feet per second. At first, I thought "no problemo"; after all, I build light, and I am usually well below - sometimes by 50% - the weight limit. But as the designs, both simple single motor and complex cluster, developed, I found that weights under 600 grams were difficult to achieve - and that was with little egg protection. Why is this?

1) The rocket has to withstand hitting the ground at 21-22 feet per second. Doesn't sound terribly fast, but this is a 15 mile per hour impact speed. You are going to have to build robustly if you want the model to last more than one flight, especially if the ground is not nice soft grass. This means basswood/plywood fins and thick body tubes - all of which are heavier than standard body tubes and balsa fins.

2) The eggs have to survive the impact with nary a crack. They are going to have to be protected well, which means a decent amount of weight devoted to padding. This is the big unknown in my designs - I do not yet have a feel for how much this will weigh. I do know that it cannot be much more than 50 grams, or my rockets will bust the weight cap. Time for some research and experimentation. But this brings up a good point - TARC teams and mentors are going to have to pay careful attention to weight in this year's competition, as it will be very easy to exceed the 650 gram limit.

As I ponder egg protection, I have made good progress on my first entry - a 4 engine cluster I call "Nemesis", after the Greek goddess of revenge. Hopefully, she will not end up too fat to fly.

Open Rocket simulation of Nemesis under power.

Monday, May 18, 2015

A Geezer's thoughts on the 2016 TARC challenge...

Well, the 2015 TARC finals are over (Yay Russellville! Have fun in Paris!) and the 2016 rules are out. I look forward to a new challenge each year, and this one has some interesting twists. So, good readers, below is a short summary of the TARC 2016 challenge, with my thoughts on some of the more interesting aspects of the competition.
  • Payload is two eggs (one oriented lengthways, one sideways) - this is a evil move by TARC, for a couple of reasons:
    1. If you do not have good protection and separation of the eggs, the lengthwise egg will drive right through the horizontal one. Eggs have decent strength along their long axis, but are very fragile along the short. I foresee many messes in the coming season.
    2. The sideways egg forces designers/builders to a BT-80 tube (or larger) for the payload section - past years could use the smaller BT-70. Larger diameter = greater surface area = more drag.
  • Altitude goal for qualification flights is 850 feet - this is higher than this past year's 825 mark, and you have twice the payload (2 eggs) + greater drag. It is theoretically possible to do this on E impulse, but I suspect many teams, even those that build light, are going to have to resort to F's or the equivalent. Greater impulse = more expensive motors.
  • Total flight duration must be between 44 and 46 seconds - 2 seconds shorter than last year, so the rocket must descend faster. Again, better have good egg protection!
  • The very tiny Perfectflite Firefly (see my Nov 30 post) joins the PNUT and APRA as an official altimeter.
  • Rocket must be at least 25.6 inches (65.0 cm) long and weigh less than 22.9 ounces (650 grams) fully loaded - same as last year.
  • All parts of the rocket must recover as a single connected unit (payload section cannot come down separately). Any type of recovery device may be used, as long as the rocket lands safely. Trip Barber and other NAR folk think this could get interesting; I think many folks will opt for ye olde conventional parachute. Kinda risky to get creative with 2 eggs waiting to become omelets.
  • Scoring, number of flights, etc. are the same as last year.
That's the challenge for the kiddos. And now...

We have also canonized the Geezer TARC rules for 2016, which are the same except for the following:
  • Geezer TARC begins with the announcement of the 2016 rules in May and ends with the contestants’ rockets being launched at a single event (date TBD, but well before school starts in late summer).
  • Each contestant may enter up to two rockets. These rockets may not fly before the official launch date, and the score shall be determined by the first flight of each on that date. The contestant's score shall be the better of the two flights, or the score of one flight if only one rocket is entered.
  • Any commercial altimeter may be used to determine altitude. However, reflights are not allowed if there is an altimeter malfunction; in this case, the flight will be disqualified (So choose a reliable altimeter).
  • There is only one rocket per design, and there are no test or sub-scale flights permitted for the design. Its merit will be judged solely by the rocket’s performance at the contest launch. If two rockets are entered, they must be of substantially different design - different number of motors, fins, or something major - an inch shorter or taller does not constitute a substantial difference, nor does the same design at a different scale (e.g., BT-70 versus BT-80 versions).
So how I am going to meet this year's challenge? Well, I have already have the first design, and the parts to build it - once I have made a couple additional tweaks. I don't want to give the competition any tips, but I can say this much:

This rocket ain't going to use a single stinking F motor!

After all, I have a rep to protect...

Sunday, May 10, 2015

May's Club Launch...

Looking out towards the range (Click to enlarge).
Yesterday saw me getting up at the unseemly (for a Saturday) time of 6:30 AM in order to be ready to depart for the Manchester field at 7:30. I had prepped 11 rockets on Friday night, and they joined Duane's rockets and numerous other gear - tables, chairs, range boxes, electronics, and snacks - that occupied most of his SUV. The goal was to arrive on the field at 9 to help with the range setup, but we made a breakfast stop at the Hardees in Winchester for some biscuits. As a result, we arrived about 30 minutes late - Woody had already started unloaded the HARA trailer. There was plenty of work to do - I focussed on setting up the low power racks, while Duane and the others deployed the mid and high power pads. More people showed up and pitched in, and we were ready to fly by 10:15 or so.

Laika on the pad (Click to enlarge).Laika blasts off on Keith's Level 1 certification flight
(Click to enlarge).
This launch would see relatively few high power rockets take to the air - the stiff wind and the high-80's temperatures discouraged high altitude flights, as one was sure to take a very long walk to recover any rocket that deployed a parachute above 1500 feet or so. I was certainly dissuaded; I would fly the 9 model rockets that accompanied me, choosing to leave the two mid power birds - a Semroc Aero Dart and a Thrustline D-Region Tomahawk - strapped inside Duane's vehicle. However, there were a few brave souls who went for it... Keith Nyman earned his level 1 certification flying a blue and yellow LOC Fantom EXL ("Laika") on an H motor; he would fly it again later in the day, along with an Estes Mega Red Max. Woody launched his scratch build, also powered by an H; he did not fly much, as he had the thankless job of being in charge of the range, which was executed flawlessly. Thanks Woody!

Woody sends a model rocket on its way (Click to enlarge).
Despite being affected a bit by the heat, I managed to put up all 9 mod rocs:
  • Estes Athena (A8-3) - This RTF was my "drift test" model. Good boost to maybe 250 feet, and recovered a short way from the pad.
  • Centuri MX-774 clone (A8-3) - Another straight flight, with recovery by streamer. Unfortunately, the rocket landed right on a pile of wooden slats near the pond, resulting in major damage to one fin and considerable scraping of the finish. Still assessing whether I will repair it or build a new one.
  • Canaroc Green Hornet clone (A8-3) - Good flight, with a bit of drift on the rip stop nylon chute. Missed the pond by "that much".
  • Estes Black Brant 3 clone (A8-3) - The maiden voyage for this bird, which went off perfectly.
  • Estes Midget clone (A10-0T, 1/2 A3-2T) - Started out well with a quick take off, but the upper stage did not ignite. The rocket came in ballistic, crunching the upper stage and driving the nose cone into the body tube.
  • Estes Helios with BT-60 booster (C11-0, B6-4) - This RTF performed really well, achieving about 800 feet. It also drifted the farthest, landing well beyond the pond. The walk reminded me how much I missed having TARC kids around to recover my rockets.
  • Fliskits Deuces Wild (2xC6-5) - The C motors put this rocket up to about 700 feet or so, and a lull in the wind caused it to land fairly close to the pads. I really like this model, as it is quite sturdy and reliable.
  • Estes Eclipse clone (1/2 A3-4T) - This black beauty shot off the pad, grabbing some serious altitude before deploying the streamer. It landed in the gravel near the road, breaking a fin (Already repaired).
  • Semroc Micron (A8-3) - My last flight of the day also resulted in a broken fin when this rocket landed in the same area as the Eclipse. Every streamer rocket flown at this launch was damaged, as the wind kept blowing them onto the gravel area.
My Canaroc FK-3 clone next to Nate's Renegade-D (Click to enlarge).
Green Hornet takes to the sky (Click to enlarge).My Micron blasts off on an A8-3 (Click to enlarge).
There were lots of other low and mid power rockets flown. Nate and Vince were there, with Vince putting up his Phoenix a couple of times on E motors and flying a Rocketarium Mega Vortex, which had a loud, fast spin coming down. Nate flew several without mishap, including his Renegade-D  and several smaller birds on C motors (He did a LOT of walking, unfortunately). Duane launched the Death Star on a C6-3, and its multi piece separation and recovery delighted the kids present. A family brought along a uniquely decorated "Frankenrocket", which they called Fireball. It made two flights, recovering successfully each time.

Vince's Phoenix leaves the pad (Click to enlarge).Nate's V-2 heads for London (Click to enlarge).
The Death Star gets going (Click to enlarge).The uniquely-decorated "Fireball" (Click to enlarge).
The biggest motor used Saturday was the J in UAH's CANSAT rocket. It made two flights, the second being the very last flight of the day, around 3:30 PM. After that, we packed up the range, loaded the SUV, and headed south to Huntsville. Nate followed us to Winchester, where we stopped at Larry's BBQ for the traditional post-club launch dinner. BBQ joints with a pig out front are usually pretty decent; Larry's has two, and the pig in the parking lot is mighty big. As you may guess, the food is also mighty good.

Dinner time! (Click to enlarge)

Friday, May 1, 2015

Back to elementary school...

This morning saw me hauling an unusual load into the office - four rockets and some basic launch gear. Horizon Elementary School is hosting a Space Week, filled with all sort of activities - projects, telescopes, speakers, and, for the final hours of the final day, a rocket launch. I love these events! Elementary school kids are so enthusiastic and excited by everything, especially stuff that soars into the sky, and I was looking forward to spending an hour or two surrounded by all that enthusiasm. Definitely beats sitting in a finance or group meeting at work...

I met Vince just outside my office building just before 1:30 and we moseyed over to Horizon, where Elliot Laramie was waiting for us. Vince had brought 5 rockets - 3 scratch builds (or kits of which I am not familiar), a Mongoose upper stage, and a George Gassaway "Spider", whereas Elliot had gathered together quite a posse - a Centuri, Xarconian Cruiser, Zooch Mercury Redstone, a Soyuz, a Bullpup, a V-2, and a couple of others. My 4 consisted of an Estes Eagle boost glider, the reliable Snitch saucer, Der Red Max, and a Quest Big Betty with a keychain camera strapped down near her rear. There was a bit of wind out of the east, which caused to us to set up on a corner of the outdoor basketball court in the eastern part of the playground. I was amazed by the number of kids present - there was a "field day" activity going on, with a shave ice truck, a choo-choo train, and several "moon walk" inflatables. I wish we had this stuff back in the Stone Age, when I was in elementary school.

The crowd gathers at Horizon Elementary as Vince prepares a rocket for flight (Click to enlarge).
We started launching very soon after 2, with Vince as the lead off man. I would follow, and then Elliot; we would repeat this sequence until we ran out of rockets or time, as we had to be finished by 2:40 in order for the school to prepare for the dismissal of the kiddos. After a very enthusiastic countdown by the crowd, Vince's rocket soared into the gorgeous blue sky and deployed its parachute for a nice soft landing. We had 3 kids designated as "retrievers" and one of them shot off like a flash to fetch it. I was next, with the Eagle boost glider, but the wind kept blowing the glider off the pod. Vince kindly helped hold the thing on until the count, but the glider again came free just as I pressed the launch button; it lay dormant on the ground while the boost pod did crazy arcs in the air. NOT the way I wanted my first flight to go. Elliot then launched his Bullpup, which flew as all Bullpups do - straight up, with a gentle recovery by parachute.

The first rocket takes to the sky (Click to enlarge).Elliot's Mercury Redstone lifts off (Click to enlarge).
The rest of the flights went well, except for Elliot's Centuri drifting away on its white parachute. I was especially pleased with the air my Snitch achieved on a C6-0, and was happy with the Big Betty flight. She came down just to the south of the basketball court and there was nary a scratch on her bulky bod. But the real highlight, at least to me, was Elliot's beautiful Xarconian Cruiser. Not only did it fly textbook straight, but the slow recovery on the Estes plastic parachute was a thing of beauty, with the rocket landing gracefully just behind the crowd. I was so taken with the rocket's descent that I forgot to snap a pic.

Elliot's Centuri begins its final flight (Click to enlarge).Vince's Spider closes out the launch (Click to enlarge).

Elliot's Xarconian Cruiser gracefully ascends skyward
(Click to enlarge).
A "rocket retriever" keeps his eye on the action
(Click to enlarge).

We managed to fly 13 rockets total - 4 each for me and Elliot, and 5 for Vince. The crowd of young spectators seemed to be well pleased, so I decided that that I should reward myself by taking the rest of the afternoon off to enjoy the extremely nice weather. This I proceeded to do for the next hour or two, after which I downloaded the Big Betty video and extracted a few frames:

Big Betty looks down at the crowd on her way up (Click to enlarge).
Houses adjacent to the school (Yes, I turned it upside down - Click to enlarge).
Folks looking up as Big Betty descends under parachute (Click to enlarge).
Big Betty laying on the grass (Click to enlarge).
Unfortunately, I have no pics of my flights, as I was pushing the fire button on my controller (not coordinated enough to handle a camera and launch a rocket simultaneously). However, it is appropriate that I at least show you Big Betty:

Big Betty (Click to enlarge).
Below is the complete video of her journey today, including the recovery by the retriever (Couldn't cut out all those little feet). I am now going to put that embarrassment of a boost glider into the "disabled" box - if it can't stay on, it don't fly.