Saturday, May 21, 2022

Some quick numbers from the 2022 TARC Finals...

The 2021-2022 TARC Finals were held last weekend in northern Virginia. No Huntsville teams made it into the top 100, though 6 teams from Alabama (5 from north Alabama) did compete at the Finals. Of these 6, four were in the top 42 of round one and advanced to round 2. Alabama ended up with two teams in the top 25 - Tharptown, which finished in the money at #10, and Muscle Shoals, which was #20. These teams will receive invitations to participate in the NASA Student Launch Program next year, and I wish them well - it will be a very busy time for those students!

Trip Barber just sent out the stats of the flights conducted at the Finals - 1st round had 810 feet as the altitude goal and 860 feet was the target of the second. My natural instinct is to fiddle with numbers and that PDF full of stats was just too tempting for me to pass up. It also gave me an excuse to try extracting tables from PDF documents - something that I had never tried before. Turns out it's pretty easy - at least on a Mac. Anyway, on to the graphs...

Motor choices of the TARC teams attending the 2021-2022 Finals (Click to enlarge).

The above plot shows the breakdown of motors used by the 100 teams attending the Finals. Note that the Aerotech F39 was the most popular motor, accounting for 25% of the motors flown in round 1. It was followed by the Cesaroni F59, with Duane's favorite TARC motor, the Aerotech F32, coming in a distant 3rd. Exactly two-thirds of the finalists used reloads and 70% of the motors were made by Aerotech. This changes a bit when we look at the same information for the 42 teams making it to round 2:

Motor choices of the final 42 at the 2021-2022 TARC Finals (Click to enlarge).

Here the number of F39's increases to 33% of the total. Reloads account for nearly 74%, and the Aerotech share increases to 76%.

Ever since TARC instituted two altitude goals at Finals (one high and one low), I have always wondered whether it was easier for the teams to go higher or lower. I suspected that it would be easier to hit the low mark, as TARC teams making it into the top 100 would have had plenty of practice adjusting weight, etc. to bring their rockets' altitudes down. Not so much the other direction. The 2021-2022 Finals data give me a chance to see if my guess was right, at least for the recent season.

Altitude scores of the teams attending the 2021-2022 TARC Finals (Click to enlarge).

Looking at the above plot we see that the mean difference between the altimeter altitudes and the 810 foot goal was about 6 feet on the low side (i.e., average altitude was 804 feet). The dashed red lines give the one standard deviation bounds, which correspond to 38 feet above and below the average. In computing these numbers, I have thrown out flights with absurd altitudes or those that were disqualified.

Now let's look at the same data for the final 42:

Altitude scores of teams in the final 42 at the 2021-2022 TARC Finals (Click to enlarge).

In round 2 the average difference was also low, but by 25 feet - 4 times the round 1 difference. The scatter is also larger; 55 feet as opposed to 38 for the opening round. I noticed that 860 feet - 25 feet is 835 feet, meaning that the round 2 average is the same as the altitude mark the teams had to hit for their qualification flights. This implies that most of the teams in the second round did not really know how to adjust their rocket to make it go higher; perhaps they fell back on the configurations that got them to the Finals in the first place? The round 2 scores were certainly worse, by almost a factor of 2 (average of 95 in round 2 versus 55 in round 1) - which lends some support to my hypothesis. However, the weather was pretty bad at Finals this year, and it's hard to rule out worse conditions in round 2 as a cause.

I guess I am going to have to see if the trend is there next year...

Saturday, April 30, 2022

New member of the fleet and pics from the last HARA launch of the season...

So I finished the Skylance - it turned out AOK. Now to apply primer to the Centuri Sabre and move on to the next project - whatever that is.

Finished Skylance (Click to enlarge).

HARA held its last launch of the 2021-2022 flying season back on April 9. I had to pass because of work, but the skies were mostly clear and the temps comfortable. However, the wind sucked; 3 high power rockets (level 1 certification models) were hung high in the trees, and so far we only have been able to retrieve one. Make that most of one - a part of it is still hanging in the tree. 

Anyway, Patrick and others passed on some pictures for the launch album on the HARA FaceBook page and I thought I would share a few below. Next time I expect to fly is Memorial Day weekend - I am going to launch more than my usual 4 or 5, I think. Have to come out of this dry spell properly.

A Student Launch team watches the sky while waiting for RSO check
(Photo by Patrick Morrison - Click to enlarge).

Top of Patrick's umbrella rocket (Photo by
Doug Aguilar - Click to enlarge).
The backside of the umbrella rocket (Photo by
Doug Aguilar - Click to enlarge).

The umbrella rocket under power (Photo by Patrick Morrison - Click to enlarge).

R2D2 pops his top (Photo by Patrick
Morrison - Click to enlarge).
The 18mm motor inside an Estes Long Ranger
CATOs (Photo by Patrick Morrison - Click to enlarge).

Student Launch rocket heads skyward
(Photo by Patrick Morrison - Click to enlarge).
Nice shot of a mid-power Crayon rocket
(Photo by Patrick Morrison - Click to enlarge).

Flyer posing by his Level 3 cert rocket
(Photo by Vince huegele - Click to enlarge).
On its way to a successful Level 3 cert flight
(Photo by Patrick Morrison - Click to enlarge).

Level 1 rocket hanging in tree (Photo by Patrick Morrison - Click to enlarge).

Estes Olympus falling out of the sky (Photo by Patrick Morrison - Click to enlarge).

Sometimes Estes parachutes do work... (Photo by Patrick Morrison - Click to enlarge).

Sunday, April 24, 2022

The Estes MaxTrax rocket...

Estes MaxTrax starter set (Click to enlarge).

I recently acquired an Estes MaxTrax starter set (now out of production). The MaxTrax was a ready-to-fly BT-56 based rocket featuring an "altitude tracking capsule" that separated from the rocket at ejection. Slowed by a small streamer, it would fall to the ground at a constant speed; impact would stop the internal timer - which was triggered by a spring loaded switch at ejection - and the capsule would display the altitude, which was simply time of fall multiplied by the speed.

A 1990's application of an old idea based on some simple physics - first proposed in mid-1970, as rocketeers searched for an easier way to get the altitudes of their birds without having to use theodolites, which were cumbersome and hard to maintain. Back in 1974, Stephen Fentress suggested that ping pong balls might be a good option, as they were standardized as far as size and weight. His data and calculations showed that a ping pong ball fell at about 28.5 feet per second, so timing the ball's fall and multiplying that number by 28.5 would produce the altitude in feet. The experiments for the RX-16 rocket in Centuri's Power System outfit also suggested using a ping pong ball to get the altitude, except that the manual rounded 28.5 to 30 feet per second (page 17). The MaxTrax was the latest rocket to use the concept, creating a capsule with an internal timer to eliminate the need to time the fall with a stop watch. It's also probably the last time this will be used in a commercial rocket - accurate, small and cheap electronic altimeters have eliminated the other methods used in rocketry for many decades. 

Note - I wrote a bit more detail about this in a blog post 8 years ago. It was intended to be the first of a two-parter, but me being me, I never wrote the second piece.

My MaxTrax (Click to enlarge).The altitude capsule (Click to enlarge).

So what to do with the MaxTrax? It's pretty obvious - stick an altimeter in the rocket body and compare its altitude at ejection (which we shall take as the "truth") to the reading on the MaxTrax capsule. Easy, and it will produces some numbers to play with. I was stoked until I happened to glance at the MaxTrax reviews on the various forums, which revealed a very important reason why the Estes concept never really worked out.

The darn thing didn't work most of the time.

It all has to do with stopping the internal electronic timer, which is started when the capsule is ejected from the body. There is a "bounce switch" in the nose, which consists of a small spring that on impact with the ground is supposed to travel forward and complete a circuit, stopping the timer. One problem is that there is too much space between the spring and the metal contact, requiring a hard impact to stop the timer. The other is that the capsule is fairly light, so it can land on its side - the bounce switch requires a nose-on impact with the ground.

Estes acknowledged the problem in a note packaged with the rocket:

Click to enlarge.

This can't be good. Still, I'm going to give it a try at my next launch. Some have suggested removing the foam around the nose cone to help close the bounce switch, so I'll start with that. I guess I can afford to waste a few B6-4 motors.

Stay tuned...

Friday, April 15, 2022

This TARC season is over...

Girl Scout team poses with their rocket (Click to enlarge).

Another TARC season has passed - and once again, no team from the Huntsville area made it to the Finals up in Virginia. I have some thoughts on why this keeps happening, which I will share later. But first, let's consider the good things that came out of this year's TARC:
  • We had 2 new Girl Scout teams, who went from totally inexperienced to making 3 qualification flights in just three months. This is quite an accomplishment, especially when you consider that one group of scouts had the best scores, beating even the John Paul II teams. One cannot help being impressed, and I sincerely hope that these young ladies will be back next year.
  • All teams made qualification flights.
  • All rockets flew straight, though we had a few problems with fins popping off. So often, in fact, that it became a running joke.
So one can be pleased that the teams crossed the finish line, which is indeed something to be happy about. We just didn't do well enough to place.

Redstone Composite Squadron team member poses
with the rocket (Click to enlarge).
Girl scouts prep their rocket (Click to enlarge). 

So what went wrong? The Huntsville teams can obviously build stable rockets that meet the competition goals, and they certainly put in the practice time - these are not the issues. The problem is not in the building and the flying. It's what comes after the flying, in the analysis of the data from the practice flights.  Therein lies the difference between making so-so qualification flights and qualification flights good enough to make the TARC top 100.

The local teams simply do not bother to analyze their flight data. There are no plots, no analysis of the altitude versus mass, no accounting for weather conditions - even though these numbers are recorded for each flight. The strategy used by the teams in recent years is based on luck, i.e., let's practice until we get a flight that has a low score, then attempt the qualification flights immediately afterward. They are essentially making random guesses until the rocket makes a good flight. The specs of that flight - mass, motor, ballast, etc. - are then duplicated for the qualification flights, even when the weather conditions have changed significantly. The outcome is predictable - lacking compensations for the wind and temperature, the qualification flights have scores in the 40's, 50's and 60's, even though the good flight had a score of 10 or less.

Girl scout rocket takes to the air (Click to enlarge).JurassicTARC team member retrieves the rocket
(Click to enlarge).

But you can't compensate by guessing. You have to look at the practice flight data to get those numbers. Unfortunately, that requires the local teams to put forth an effort beyond what they are currently willing to do. So they trust to luck. And sooner or later, that strategy will pay off for someone. On a rare day, Fortune will smile upon a team who will string together two decent qualification flights, setting them on a path to the TARC Finals. But to win in Virginia, you have to fly to a different altitude on a different field, and even Fortune can't help against those odds. Placing in the top 10 requires that you understand how to adjust the rocket to meet a different goal.

John Paul II teams hard at work (Click to enlarge).

We are planning to hold a TARC workshop early in the coming season - maybe there will be a team that will listen and realize that looking at the flight data is just as important as designing the rocket. 

I keep hoping.

Monday, March 28, 2022

Merging video and data

Rocket electronics have gotten quite cheap - small altimeters and decent HD cameras can be had for as little as $30, putting "instrumented rocket flight" within the reach of every rocketeer. Most folks are content with keeping the video and data separate, but I have always been intrigued with synchronizing the data with the video, so that each frame can be tied to a specific height, speed, acceleration, etc. My first experiments (back in 2017) in doing this involved my Windows PC laptop and a program called DashWare; the software was somewhat cumbersome from a usability perspective (hey, it was free!) and so I soon lost motivation. Too much work!

DashWare created video

Time passes and new software appears. Late last year, I discovered that there was this software application called RaceRender, with capabilities like those offered in DashWare. The good news was that it was available for MacOS, meaning I could make use of my big screen iMac in creating data-synced videos; the bad news was that it cost money, especially if you wanted to remove the stupid program logo/watermark from the videos. After a bit of research, I made the plunge and bought the software. Fortunately, I was not disappointed with this purchase (unlike some others in the past).

Regardless of whether you use DashWare or RaceRender, you need two things to create a data-synced video - the video from the camera and the data from the altimeter, flight computer, or whatever. The video must be in a format readable by the software - not a problem for the cameras generally used by rocketeers - and the data should be in a file with numbers arranged in a comma separated value format (csv). Files downloaded from all logging altimeters of which I am aware are in this format, so again no problem. You may have to edit the csv file to remove parts before launch and well after landing, but this is pretty easy using Excel or some other spreadsheet application. The only gotcha is understanding the limitations of the software - for example, RaceRender can't deal with negative speeds, so you need to take the absolute value of speeds from altimeters (e.g., FlightSketch Mini) that give the descent speeds as negative.

RaceRender screen capture (Click to enlarge).

Once you have the input files properly formatted, you import them into the software and select the ways you want the data displayed - simple numbers, gauges, or graphs; it's up to you. Then you have to sync the data to the video by selecting a video frame corresponding to the first line of data, usually t = 0, the time of first motion on the launch pad. This is easy to do with most rocket videos, as first motion is readily apparent when you step frame by frame through the movie (unless the camera is pointing up - then it is really hard). You then invoke application's sync feature, et voila! The data is now properly displayed on the video as it plays. The final step is exporting your project into a standalone video, which you can share with your buddies on YouTube, FaceBook, etc.

This past Sunday I flew my Estes Solo with an Estes Astrocam and a FlightSketch Mini, as I wanted to get some footage of the glider separating from the rocket near apogee. The flight was successful - the C6-3 motor carried the rocket up to 222 feet and the glider separated at 200 feet, on the way down. I would like a better camera than the Astrocam - the shutter can't handle fast motion (distorts) and it does not have a good depth of focus - but better cameras are heavier and not easily carried by low impulse model rockets. I eagerly look forward to such critters appearing on the market.

Frames from the data-synced Solo video (Click to enlarge).

Friday, March 18, 2022

Vendor review - Apogee Components

I decided some time ago that I should occasionally write reviews of some of the vendors I patronize - to heap praise on the things they do right (which is often) and to keep them honest when they muff things up. A recent email from Apogee asking for a review/testimonial has led to this post, as I can add to the blog and give Apogee what they asked for (well, sort of) in a single writing. Plus Apogee starts with an "A", making it a logical choice for the first review. So let's begin, shall we?

Apogee Components (

Started by Ed LaCroix back in 1989, Apogee was bought by Tim Van Milligan in 1995. He grew the business from a small one room shop into what I consider a true small business, now having several paid employees and a dedicated building. Apogee is noted for its wide selection of kits, of its own make and from other manufacturers, and is the developer of what is (probably) the best rocket design/simulation software available, RockSim. I have purchased items from the company for many years, and it has been very nice to watch it expand, both in the product line and in the services offered. Tim is a long-time competition rocketeer who is dedicated to the hobby and he does a pretty darn good job in balancing his company's interests with serving the rocketry community.

Positive aspects of Apogee Components

  • Extremely fast shipping and 100% reliability: Tim guarantees your order will be shipped by the end of the next business day (same day for orders placed before 2 PM) and has always lived up to that promise (in my experience). I also have never received the wrong stuff - some vendors make mistakes in matching the packing with the order, but not Apogee. Tim offers the buyer a choice of shipping methods (motors have limited options) and ships using the service selected by the buyer. This may seem stupid to highlight, but there are some vendors who offer a choice of shipper and then ship USPS, regardless of what the buyer selects (and pays for). Apogee is 100% reliable in shipping - in my opinion, they are the best in the business. 
  • Outstanding selection of rocket kits: Apogee has a very large selection of low and mid power kits, along with some that are Level 1 class high power. Not only do they have the usual stuff from Estes, Semroc, LOC, Aerotech, etc., they also have offerings from less well-known companies like Aggressor Aerospace Rocketry and J&H Aerospace. Apogee's line of 4 inch kits is very popular among high power novices - I cannot recall a HPR launch in the past few years when there was not a Zephyr, Katana, or Peregrine present. The Zephyr is especially beloved - there are often multiple Zephyrs leaving HARA's pads on launch day. I guess that's why Tim started offering the 24 mm powered Zephyr Jr. for those hesitant to dip their toes in the high power waters - it's a beauty at any size. Recent Apogee releases include a line of BT-55 based beginner rockets (Habu, Atomizer), and I agree with Tim's idea that bigger body tubes are better for novice rocketeers - easier to manipulate and pack the parachute. Not a big fan of the Habu's snake decor though <shudder>.
  • Competition kits and parts: I am currently aware of only 3 companies that have kit and parts offerings suited to rocketeers wanting to participate in non-scale NRC and FAI competitions - Apogee, ASP Rocketry, and Galactic Manufacturing. Apogee has a good selection of kits that span the range of competition, from the Cirrus Breeze rocket glider to the EggTosser egg lofter to the International Thermal Sailor duration bird to the Rotary Revolution gyro copter to the Spek payload altitude rocket to the... well, you get the idea. They have lots of competition kits. These tend to be a bit on the heavy side, so you probably won't be setting any records with them, but they are more than good enough to put you on the NRC National Scoreboard. Beginners should take note of these offerings, as they are an excellent first step in building competition experience. Apogee also offers some competition parts - egg capsules (they may be the only current supplier of these), lightweight styrene nose cones, foam plugs to replace wadding, "fly-away" rail guides and launch towers.
  • TARC: Speaking of competition, Apogee is an excellent source of parts for the annual TARC competitions. There are the usual body tubes, rail guides, motor retainers and so forth, but the company makes the most awesome egg cushions on the market, capable of protecting the fragile egg payloads even in catastrophic circumstances. I kid you not - I have seen TARC rockets come in ballistic, suffering major damage, and eggs in these cushions survived with nary a crack. We strongly recommend these to the local rocket teams and the number of messes has gone down significantly since they started using them. I am also a big fan of the colorful Apogee printed nylon parachutes - they are not only good for TARC rockets; I stuff them into any rocket of mine in which they fit (BT-50 and larger). Much better than plastic parachutes! Another part of Apogee's TARC support is their "TARC Bulk Pack of Parts", tailored for the active TARC contest year. Unlike past offerings from Estes and others - which were basically SPEAs (Spare Parts Elimination Assortments) - thought has been put into the Apogee parts assemblage. You can actually build 2 very competitive TARC rockets from this product. The only negative is the provision for a two 24 mm cluster in this year's TARC bulk pack... C'mon Tim, what top 10 TARC team has ever used a cluster? Despite this minor flaw, the TARC Bulk Pack of Parts is an excellent set of components for TARC teams, especially new ones. I sincerely hope Apogee continues to offer this product in future years.
  • Tutorial videos, newsletter, and rocket plans(!): Tim renders a valuable service to the rocketry community through his many tutorial videos on pretty much all aspects of rocketry. We often ask novice rocketeers (especially TARC teams) to view those pertaining to rocket construction. The company's "Peak of Flight" newsletter has informative articles, and occasionally features a rocket design one can build from Apogee parts. The plans are near and dear to my heart, bringing back fond memories of the old Estes "Design of the Month" contest and similar featured in the Centuri newsletters. I particularly love the old Shrox designs, but there have been some good ones recently, like the "Fabled Flyer." BTW, if you can't or don't want to make decals for these designs, you can buy the markings from Apogee - a nice encouragement from Tim.

Negative aspects of Apogee Components

In this universe, nothing is ever perfect. No matter how good you are, there are always flaws. Even Apogee has one...

  • Cost - Buying from Apogee ain't cheap. Expect to pay retail or something pretty close, and I sometimes wince at the prices. 31 bucks for a 2 stage BT-55 based kit? Ouch - even if it is very cool in appearance. To be fair, Apogee is a business; Tim has several mouths to feed, overhead on a big building and equipment costs/maintenance, etc., etc. - plus the inflated costs of materials these days. So one should not expect the discounts offered by AC Supply and a few other vendors (which are not as good as in the past, BTW). Tim acknowledges the price issue on his website - see "We are a bit more expensive, but your goals are worth it" on this page. Partially balancing out the higher prices is the Apogee VIR (Very Important Rocketeer) program which allows you to accumulate points that you can apply to future purchases. It's pretty good; I just used some of my points to purchase a fin jig to help my aging carcass get the fins on straight.

In summary, Apogee is one of the best rocket vendors out there. It offers a wide variety of products and even caters to niche markets like NRC/FAI competition and TARC. The company also offers excellent tutorial videos and materials, produced by a rocketeer with many, many years of experience. On top of this, they are fast and 100% reliable in shipping - they have never screwed up one of my orders. The only downside is the prices, but I am willing to pay more for the services and unique products Apogee offers. So please consider them when you are buying rocket stuff - you won't regret the purchase.

If you read this Tim, I have a request - please lay off the snake-themed rockets. I don't want rocket powered snakes haunting my dreams.

P.S. - RockSim/Launch Visualizer review to come later. It merits a separate post.

Saturday, March 12, 2022

I get a thing in the mail...

 I went to the mailbox earlier this week, expecting the usual bills and "waste of paper" ads. However, there was a surprise - tucked in amongst the Arby's and Dominos flyers was a nice little postcard, sent to me by Ed Mitton. The card was one of 20 flown in the payload section of his Icarus rocket, which made its maiden voyage on March 3. I had read about it on his blog, and thought it was a supremely cool resurrection of an old concept. Had no idea I was one of the recipients though - the blog post implied he sent the cards to those attending the launch. I am pretty stoked about receiving one - may even do this myself at future launch.

Thanks Ed!!!!