Sunday, August 31, 2014

Heavy artillery...

While I was visiting the Air and Space Museum near Dulles last month, I ran across the Tiny Tim rocket, developed during World War II. The simplicity and aesthetics of this weapon appealed to me immediately:

Tiny Tim rocket on display at the Air and Space Museum (click to enlarge).
The short description also interested me:

The Tiny Tim air-to-ground missile was the largest American rocket in service during World War II. Loaded with TNT, it could destroy coastal defense guns, pill boxes, bridges, tanks, and ships. Tiny Tims sank at least one Japanese ship and seriously damaged another. During the Korean war, one Tiny Tim knocked out a key bridge. Visible in this partial cutaway are simulated solid propellant sticks and some of the rocket's 24 exhaust nozzles.

A Google search yielded more info. This 10 foot long puppy carried a 148 lb warhead up to 1600 yards and had a thrust of 3,000 lbs. It was typically mounted underneath aircraft, as you can see from the below images:

Top: Tiny Tim mounted on a P-51 Mustang.
Bottom: Tiny Tim being fired from a SB2C Helldiver.
Today it rained muchly, which put the kibosh on priming/painting rockets (I did get manage to glue the fins on the Viking, though). A little water is not sufficient to stop the rocketry bug; I remembered this rocket from my trip and fired up the computer to create a design of a flying model. The first part is always the most difficult - choosing a scale. This is largely driven by two things - the diameters of the available body tubes and the sizes/shapes of the available nose cones. I knew I wanted this rocket to be at least BT-70 (2.217 inches) in diameter and the Fliskits' upscaled Deuces Wild nose cone for this tube looked to be the right shape. This being decided, it was fairly easy to take the dimensions of the real Tiny Tim and work out a scale - 1/5.2774. Not a nice fraction, but hey, we have computers now, don't we?

This gave an overall rocket length of 23 inches. Subtract 4 inches for the nose, and you are left with 19 inches for the body tube. I knew I would probably need nose weight, so I split it into a 3 inch payload section and a 16 inch sustainer. Inspired by the 24 exhaust nozzles of the original, I went with a 5 motor cluster as the power plant - 4 13 mm motors (Estes A10's) and a single 24 mm motor. Such a combo would allow for many different motor configurations (1, 3, or 5), producing altitudes to suit launch field constraints and my mood. It should also instill terror in my friends when they see me try to light 5 motors simultaneously.

It took a couple of hours to get all the measurements and do the design in Open Rocket. It turns out that I need about 1.5 ounces of weight up front to insure stability, but even with this a single D12 should send Tiny Tim to over 500 feet. 4 A10's and a D12 will put it at around 870 feet, and an E30 will produce a max speed of about 0.5 Mach and a peak altitude of 1350 feet. Not too shabby.

Tiny Tim design in Open Rocket (click to enlarge).
After finalizing the design, I also played around some more with the photo rendering feature of Open Rocket. I was able to render my version of the Tiny Tim as if it were just launched from a plane to a surface target. I am really beginning to like this software - It's quite powerful (as long as you stick to basic rocket designs), and you can't beat the price (free).

Tiny Tim rendered in Open Rocket (click to enlarge).
This will be the next rocket project once I finish with the Wizard and Viking I am currently building. Time to start gathering the parts…

Saturday, August 30, 2014

Slow, quiet progress...

Not too much has been going on, rocketry wise - at least not significant enough to write about. Over the past couple of weeks, Duane and I have attended the initial TARC meetings at Liberty and Buckhorn middle schools. We gave little pep talks and showed off our TARC rockets. Not as many kids as I expected, but today's youth have much to do after school, with homework, sports, band, robotics, etc., etc. I certainly do not remember being that busy in Junior High - except for homework and band, I seldom had to be anywhere. Truly a different world nowadays.

But with several thousand bucks prize money and a free trip to Paris, you would think it would have more appeal. I know I would have been all over it.

Anyway, the rocket building continues, but at a slightly slower pace than when I was facing the Geezer TARC launch deadline. I just finished a clone of an Estes Alpha in the current decor scheme and a Quest Payloader One. The latter is a favorite of my friend Woody and I punched a couple of small holes in the translucent red payload section to enable altitude measurements by one of my altimeters (they have to be able to sense the surrounding air or you get nada). I am about to paint the Estes scale model of the Patriot missile, and am working on an Estes Wizard and a Rocketarium scale kit of the Viking 7 rocket. It's a two motor cluster, which makes me happy :)

TARC season gets underway in September, so things should liven up a bit. Huntsville could very well field a record number of teams this year, well over 10. We shall see.

Clone of Estes Alpha (click to enlarge).

Quest Payloader One (click to enlarge).

Saturday, August 16, 2014

A not-so-agonizing defeat

Today was Geezer TARC.

And I lost. Duane is THE man for this year's TARC season.

But I am not perturbed. Any day that sees rockets flown is a good day, and several birds took to the air this morning. It was a great day to fly, and I, Duane, Nate, the kids and parents who came out to watch had a good time on a green field in great weather. Liberty Middle School kids who are thinking about doing TARC for the first time got to experience what a TARC launch is like. Who can complain about that?

Now for the details…

We arrived at the Harvest horse farm right on time at 10 AM, and quickly set up the tent and pads. About 8 Liberty and former Falcon Rocketeer kids showed up, along with their parents; Nate was there as well, but brought no rocket to fly (slacker). I was thrilled with the turnout, especially the kids - it's always nice to have a recovery team to chase down the rockets.

First up was one of my Alpha III's on a B6-4 to test the winds. It reached about 400 feet and drifted a bit to the northeast. The drift was not much, which gave us confidence that we would miss the evil rocket eating trees off in that direction (They had claimed my TARC rocket and $70 altimeter last year). The winds established, I somewhat nervously set the Bullpup 1 on the pad; it would be the first competition rocket to take to the air. After giving the standard 5 second countdown, I pressed the button of Duane's controller and watched Bullpup 1 streak skyward under the power of 2 Estes D12-5 motors. The up part was beautiful - straight and high; you could tell that it was close to the altitude mark from the ground. I only wish the down part had gone as well; the payload section's parachute tangled, resulting in a very fast descent at about 43 miles per hour. It hit the ground with a sickening thump after only 22 seconds in the air, far short of the 46 second goal. The raw hen's egg inside the payload section was obviously a goner, but I waited until the recovery crew brought back the sustainer before listening to the altimeter beeping out the peak altitude - 855 feet (or so I thought - analysis of the altimeter data showed that the rocket actually reached 867 feet), which was not bad. Only 55 feet high on a first flight.

Bullpup 1 on the pad (click to enlarge).
Then it came time to open the payload section, and it was as I had feared. The egg was shattered; not even the saran wrap I had wrapped around it was able to prevent yolk and shell fragments from covering the inside of the section. And not just the payload part - yolk had also flowed into the altimeter tube, coating my Perfectflite altimeter in a yellow gooey mess. Fortunately, I was able to clean things up (mostly) with paper towels. Bullpup 1 is ready to fly again at another launch.

Flight 1, broken egg. Disqualified. Things were not looking good.

Duane launched his yellow and black beast on an Aerotech F32 (His description, not mine. He described today's launch as my "beauties" versus his "beasts"). His rocket soared to 862 feet (the best altitude of the day, it would later turn out), and the payload section landed safely 56 seconds after liftoff. At 94, this was the winning TARC score of the day.

Duane's yellow and black "beast". Today's winner (Click to enlarge).
Flight 2, 94 score. Duane in the lead.

One of the Falcon Rocketeer's had brought a couple of rockets to fly, and he launched a Rocketarium Witchcraft on a B motor. It put in a nice flight, but ended up landing on top of one of the horse barns. Nate came to rescue by texting the owner, who said he would recover the rocket and return it to us the next time we fly at the field. The rocketeer then launched a scratch build, which also flew well, if you do not count the fact it came in without deploying the chute. Fortunately, there was little damage to the rocket. That young man and I had much in common today - we could not get our recovery devices to work right.

Duane's brown and silver BT-70 rocket made TARC flight 3, powered by an Aerotech E15. Altitude was a little high and time a little long, but it ejected the motor during flight, resulting in a disqualification. I followed with Der Eggcracker on the final TARC flight. It flew a bit too good (over performance issues, maybe?), soaring to 1047 feet on an Aerotech E20. The payload section parachute deployed fully, landing safely after 70 seconds, but the sustainer parachute tangled. The rocket gods smiled upon me though, for even though its landing was a bit hard, there was no damage. Der Eggcracker did not live up to its name, for the egg was in perfect shape, giving me an embarrassingly high qualifying score of 339. I think I would have preferred a disqualification.

Flight 3, motor kicked. Disqualified.
Flight 4, 339 score. Qualified, but sucky to the max.

Duane's BT-70 TARC rocket (on left) and Der Eggcracker (click to enlarge).
Geezer TARC was over, and I congratulated Duane on his victory. He, however, was not content to leave things be, and flew his BT-70 rocket again on an E20. It chuffed on the pad, and flew off at angle to the southeast; not exactly what was hoped for. I closed out the day with a flight of my Big Bertha on a C6-3, to test out a new keychain camera I purchased at Southern Thunder. Here's the flight video:

This launch was a lot of fun, and Duane and I agreed it should an annual thing. Perhaps next year we can persuade others to join us. That would be exciting indeed!

P.S. For those of you who like flight details, here are plots of the altimeter data from Bullpup 1 and Der Eggcracker's flights:

Bullpup 1 altimeter data (Click to enlarge).

Der Eggcracker altimeter data (click to enlarge).

Friday, August 15, 2014

Awaiting tomorrow...

The night before a launch is always a hectic time - I am scurrying about for several hours doing various stuff. Launch controller, altimeter, and camera batteries need to be charged; rockets need to be chosen for the next day's flights, and then loaded with their parachutes and motors (Don't put in the igniters until just before launch - have to be safe, you know). And then there's the launch pad, camp chair, and sun screen to pack up, along with my range box of motors, igniters, and other odds and ends.

And no matter how much I prepare, I always seem to forget my cap - very stupid, as I have no hair on top of my shiny head. Tomorrow is going to be different though. We have the "Geezer TARC" showdown starting at 10 AM, and I shall be both prepared and properly dressed for the occasion. I have to be, as Duane and Nate have invited practically the entire town to see our fly off. I suppose it is for the best - a victor needs a crowd to applaud his win. Duane thinks it's gonna be him.

But I shall prevail.

The chosen for tomorrow are:

  • Alpha III - loaded with a B6-4, this "expendable" bird will give us a gauge on the wind before we commit our TARC beauties to the wild blue yonder.
  • Bullpup 1 - loaded with 2 D12-5's, this is the rocket on which I am pinning most of my aspirations.
  • Der Eggcracker - armed with a single E20-4W, it is my chance for redemption if the Bullpup does not fare well.
  • Big Bertha - my battered Big Bertha will carry a keychain camera aloft on a C6-3 to get some onboard video. I try to do this every launch with a rocket.

Depending on how the day goes, I may refly one or more of these. The TARC rockets are the priority.

It's going to be an exciting day!

Sunday, August 10, 2014

Waiting to fly...

The Mark 1 and Mark 2 rockets I designed for "Geezer TARC" (See July 13th post) are finished - and they now have names. The Mark 1 is now the Bullpup 1, named after my old Junior High school mascot. The school burned down long ago, but the rocket carries on the tradition with its blue and white paint scheme. I am fairly confident it will make the altitude mark of 800 feet on two D12-5's, unless I am wildly off on the drag coefficient.

Bullpup 1 (click to enlarge).
The Mark 2 is now "Der Eggcracker." Styled after the Estes "Der Red Max", this single motor powered rocket is the minimum diameter (1.8") needed to carry the large hen's egg required by this year's TARC rules. The Open Rocket simulations indicate that an E20-4 motor will put it within 80 feet of the altitude goal. Unfortunately, I have no E20-4's - just placed an order with Hobbylinc; hopefully they will arrive this week.
Der Eggcracker (click to enlarge).
The "Geezer TARC" fly off between me and Duane was supposed to have been yesterday, but bad weather (thunderstorms) forced the cancellation of the club launch at Manchester. Probably a good thing, as I did not have the optimum motor for Der Eggcracker (an E30 would have a bit too much oomph), which pinned most of my hopes on the Bullpup 1. The new launch date has not been set, but I expect it will either be during the Labor Day weekend or at the Manchester launch in September. The couple of weeks delay gives my buddy Nate a chance to build a bird and join in the fun.