I Love Data

Not the android. Cool guy and all, but annoying after a while.

No, I'm talking about hard data. Facts. Information. Numbers. I love it. Call me a lifeless nerd (I do not deny), but some days I'd rather sit in the glow of my laptop screen and process data than do most anything else.

For example, my spreadsheet of data of all my rocket launches. It does everything. Automatically computes stats for every rocket and motor I've launches since October 2008. I'm still updating it to be more automatic, but it works nicely.

Ideally, it'll automatically compute everything. Add a new flight, it'll automatically add the impulse for the motor, update the number of flights for that particular rocket, add the reference number for that rocket, and update the number of flights with that particular motor. As of yet, all those things have to be updated manually.

But, once I finished sorting through all the errors today, I discovered some interesting stuff.

One odd bit is when I looked at the total impulse I've flown of each motor type. The two H165s from my certification last summer amount to 330 Newton-seconds, more than any other motor. 35 C6s equal 308 Ns, and 18 D12s make 302 Ns.

One more cluster flight with the Buckeye IV, though, and 4 more D12s will put it on top.

Launch Report #37: CATO 160

Saturday was an absolutely great day for a launch. The winds were a little high in the morning, but it was warm and dry and sunny and the flights were good. I flew 5 rockets; only one flight was perfect but the other 4 were all good and none of them got lost in trees.

First off the pad for me was the Multi-Goon loaded with 3x A8-3 motors in the 18mm cluster mount. Because of the 12 large fins, it arced over into the wind; fortunately, it deployed for a perfect landing and no damage except for some burns on the cluster mount. Next flight will be either on 5 13mm As, 3 18mm Bs, or 1 24mm D.

Second flight was the Goddard L-13 on a B6-2. Woefully underpowered and it arced over quite a bit. Parachute didn't deploy and it core-sampled; the rocket was mostly undamaged but the chute protector had unfolded too much and the parachute has 2 small burn holes which will be repaired. Next flight will be after repairs and painting on a C6-3.

Third flight was the Nike Goon on a B6-4. Not underpowered but unimpressive (simulated altitude 280 feet); this really needs a C or D. Streamer didn't fully deploy and one fin broke clean off; it's currently being repaired.

At this point, I'd flown three small rockets. I had the Svetlana loaded with an E18-4W, but it stubbornly refused to light. One Copperhead igniter failed (not surprising; Copperheads are cheap and kinda crappy) and one Quest Q2G2 failed (a surprise; they're very good igniters). So I was running our of good igniters. Then Rick Comshaw, who's the Wildman dealer for Connecticut offered me a deal: If I could find his rocket, he'd give me a free pack of igniters. Now that's an offer I couldn't refuse.

Now, mind you, he and another flier had spent over an hour looking along a large section of the tree line and not found it. We all had a pretty good angle on where it hit the treeline, but it wasn't in the thick trees there, nor on the field. So, instead, I decided to look deeper in the forest, since the rocket was fiberglass and pretty heavy. I found it almost 250 feet into the forest, across the stream, about 15 feet up in a tree. I climbed a small tree, grabbed it, and yanked it down, so I got my igniters.

Once I sanded the grain and added a piece of tape to improve ignition and put in the new igniter (a high-quality FirstFire Jr), it ignited immediately, sending the Svetlana to a simulated altitude of 850 feet. The parachute tangled and got a small burn hole, but the draggy body flapped around and it was undamaged.

Finally came VIPERFEST. Four of us had Viper IVs ready for launch, and one fellow had a similar Viper III. (My mom got there just in time to snap a few photos). All D12 motors; that's 19 (4x4 + 1x3) motors sitting on the pad:


Second from left is Al Gloer's Viper; 4th is the Viper III, and my Buckeye IV is on the right. Our new launch system built by a club member, took the full voltage of a car battery and applied it to 19 igniters. The result: 19 motors (100%) fired:


Al's got off the pad first because he used the Q2G2 igniters which fire milliseconds sooner than plain Estes igniters. All 5 lifted off perfectly just as the wind died; the 4 Viper IVs all went to around 860 feet, and the Viper III to slightly less. Mine is the smoke trail that extends off the top of the photo. One Viper used D12-7s instead of D12-5s; the extra 2 second sof delay means it's the one off the the right still producing tracking smoke:


All five chutes deployed perfectly; since the wind had died down, they came down rather near the launch pads. My simulated flight duration was 38 seconds, and reality matched exactly. This final photo, taken just one second before landing, is timestamped 37 seconds after liftoff.


I flew 5 rockets on 10 motors, including my first 3-motor and 4-motor clusters. I had a great time; the Viper flight was one of very few absolutely perfect flights I've had. It ranks right up there with my certification flight and the first flight of the Mozzie.

I also bought 18/20 motor hardware from Mr. Comshaw; I plan to fly the 18mm D reloads in rockets like the L-13.

One final note: the 1st, 3rd, and 4th pictures were modified slightly using the 'I'm feeling lucky' autoadjust in Picasa. Here's what happens when you use it too many times, just for fun:

Launch today!

Later today (i.e, after I get some sleep) is CATO 160, my first CATO launch since November. Weather looks to be good, and I'll be there from 9 till 2. I probably won't get a lot of pictures if any, though; neither my dad nor mandachan will be there with the photography awesomeness.

Rockets I'm bringing:

Heli-roc (A10-3)
Multi-Goon (3x A8-3 or 3x B6-4)
Nike Goon (B6-4 or C6-5)
SpaceShipOne (C6-3)
L-13 (B6-2 or C6-3)
Mach Goon* (G115-11WT)
Svetlana (E18-4W)
Pyramid* (G64-4W)
Mozzie (several choices of E and F motors)
Buckeye IV (4x D12-5)

* Neither of these will probably fly today, but I'm bringing them just in case.

Presenting: the Buckeye IV

It was in the upper 50s again today... it might have momentarily even reached 60!

So, I hung my rocket from a tree again. Well, actually, first I sanded the primer with steel wool so it was nice and smooth. Then, I put a coat of medium grey on the middle on the rocket. It's pretty much primer color, but actual paint, and it's smooth even without sanding.

Then, I did some masking. A lot of masking, actually. 137 pieces of green masking tape; most were angled pieces under an inch long. Then I hung it up again, and sprayed a nice even coat of red.

Here's the result:

 

Priming the Viper IV

Weather got up to 57 degrees for the first time this year. At my dad's suggestion, I tied a rope around the motor retainer and hung it from a tree out in the woods.

The can, fortunately, had enough primer left to prime the entire body tube and nose cone. (The fin / motor unit had been previously primed). It's currently out drying and looks really good, though completely ridiculous hanging from a tree.

Pictures coming, maybe.

Priming and painting

For the first time in over a month, the weather got over 50° more than momentarily today. 50 is a pretty important temperature because that's the minimum temperature for my auto primer. So, I went out and painted some rockets.

First, I primed everything:

Viper IV (fin unit only)
SpaceShipOne
Svetlana
18mm booster (still needs a name)
18mm glider pod (ditto)

The can of primer was almost 7 bucks but well worth it. It coated everything nice and smoothly and dried very quickly. I let it dry for about 20 minutes before I came back to paint.

I'm not sure how I'll paint the Viper IV yet, so I didn't paint the fin unit.

The Svetlana got a coat of a nice cherry red. Sometime later I'll add black fading a patterns, per suggestion of mandachan.

The SpaceShipOne is now white, although it'll need a second coat for full coverage. Already, though, it looks so much better than before. Putting primer on, especially the nice auto primer, makes the bottom coat opaque so the paint really looks nice and even.

The 18mm booster is now yellow; I might add a roll pattern later. Feel free to suggest names for it and the glider boost pod in the comments.

I painted the boost pod yellow on one side, green on the other. Green is usually a dangerous choise cause it blends in with grass, but the yellow will make it easy to find.

Pictures will come later, maybe tomorrow, after everything is dry and I can bring them all inside without stinking the house up.

This is taking forever

Currently, the Viper IV construction is almost so very nearly at a halt. I've got the entire fin assembly glued together, so now all I have to do is the fillets on the fins. Which, due to the four motor tubes intersecting, have any number of little nooks and crannies that are really really hard to fill. In fact, there's a total of 56 inches of fillets that I have to rid off some 40 tiny little holes, and I can only work on one of the four sides at a time.

Which effectively means that this is going to take a while. Sunday is about the earliest I can possibly expect to be done with the fillets. Fortunately, after that, it's smooth sailing - just glue on the fin unit, tack down the launch lug, and tie the nose cone to the shock cord.

And, of course, 2 coats of primer and 2-4 coats of paint, but that's another story.

However, I do have some side projects going. The first of those I started today. It's a new 18mm booster stage, to replace the older version that got destroyed in spectacular fashion. While this one still won't be able to survive a 300 feet-per-second power prang**, it does have some improvements.

It's a brand-new piece of tubing, rather than a crappy piece of scrap. The tubing is a bit long so that the butt joint between the upper-stage and lower-stage motors is inside the tubing, which lessens the likelyhood of the joint bending. The fins are large, strong 3/32" balsa and will have double fillets of wood glue, so they'll be very strong. They're nice and large, which will keep the rocket stable and also slow the booster down on its descent.

I've also got a few other designs that I'll be building soon. They include a 13mm boost pod for gliders, a 29mm saucer, and a ridiculously complicated design.

Viper IV part VI: Pictures!

Because I know I've only got about one more post before someone bugs me for pictures...

This first one is the fin unit with the fillets drying. It's up on blocks so it stays upright.
 
Note the way the 4 motor tubes fit into the brown coupler; it took a lot of balsa, tissue paper, and wood filler for the nice joint you see here. Also note the 4 motors test-fit into the motor tubes, and my homemade motor retainer.

 
When I'm old and stodgy and have a desk and an office, I will make one of these fin units again. Because it's so much cooler than a plant, serves as an auxilary paperweight, and start a lot of conversations. Especially if everything goes as planned and I go into aerospace engineering.

 
This is just a dry fit, but it's roughly what I'll look like glued together. except for the whole 'paint' thing, of course.

 
Here's a close-up of the shock cord mount.

I bought some extra 1/4" elastic today. I'm going to add 9 feet of that to the 8 feet of shock cord already included with the Viper IV. More shock cord means less change of it breaking or of the nose cone bouncing back and hitting (and damaging) the body, and makes it 9 feet easier to recover if it lands in a tree.

Viper IV building part V

Over the last few days, I've actually managed to get the fins on the Viper IV.

Since it's been pretty wet and humid the last few days, I knew that trying to glue each fin on with wood glue would not work, because it would take forever to dry and the bond wouldn't be that great. Instead, I spread superglue along the joint between the fins and motor tubes, forming an instant bond that holds the fin in place. Then, I used wood glue to make a fillet. They're still finishing drying and will require a second coat, but once finished all four fins will be strongly attached to the motor tubes with smooth joints.

The way that the Viper IV is built is somewhat unusual. For most mid-power rockets, one glues the motor mount inside, then attaches the fins either directly to the body tube, or through it. Every major component is glued to the body tube, which is the foundation of the rocket. With the Viper IV, the foundation is the quad motor mount. It takes a lot of work to glue the motor tubes together, add positive retention, fit the motor mount into the coupler, and glue on the fins. Only at the end is the whole subassembly added to the body tube, and the only other things glued to the body tube are the shock cord and launch lug.

Viper IV building part IV

I've finally managed to get the motor mount almost complete. It took quite a bit of balsa to get the 4-tube cluster to fit exactly inside the 2.56" coupler, but that turned out to be the hardest part.

After that, I just stuffed tissue paper down into the cracks and covered that with wood glue, creating a hard stuffing that won't let ejection charge gasses leak past. Finally, I covered the end with wood filler for smoothness, and that's currently drying. Pictures will come, eventually.

Hopefully, I'll get a lot done tomorrow. We're supposed to get up to a foot of snow, and school got canceled at 8:40 pm. That's only the second time in the last decade that it's gotten closed the night before, and as I write this just before midnight it hasn't even started snowing yet!

Viper IV build thread part 1: the parts

Because I'm bored, and it's my fervent but misguided hope that there's at least one person on planet earth who is interested (and also cause it'll help write the EMRR review), I present the Viper IV build thread.

I might cross-post it on TRF. Basically depends on if I feel like it tomorrow.

(note on abbreviations: LOC-Precision, here just 'LOC', is the company that makes the kit, including all the components. PNC = Plastic Nose Cone; BT = Body Tube)

Without further ado, what actually came in the bag:

• Nose cone: 3.5:1 plastic ogive PNC-2.56, color off-white. The shoulder is 2.5" long and includes a molded eye for shock cord attachment. It's standard-issue LOC thick-walled plastic - 112g (3.95 oz) accoridng to Apogee, and has raised ribs on the seams.
• Body tube: 30" of LOC BT-2.56; 2.56" internally and 2.63" externally weighing 139g (4.92 oz). The tube is thick-walled and high-quality, with an outer glassine wrap for strength and ease of finishing. The spirals are tight and shallow and will not interfere with finishing.
• Coupler: 3" of LOC 2.56" tube coupler; 2.479" internally and 2.555" externally weighing 11.8g (0.41 oz). It is also thick-walled and made of kraft paper; it is used to fit the 4 motor tubes into the rocket. Formerly Viper IV kits contained 2 plywood centerting rings, but those tended to snap durign sendign hence the change.
• Motor tubes: 4 lengths of LOC 24mm motor tube, each 12" long and in total weighing about 1 ounce. As well as the motor mounts, they are the entire aft end of the rocket.
• Fins: 4 plywood fins each 1/8" thick and total weight about 2 ounces. The root is 5" long, the tip 2", and they they're 4" wide. The plywood is incredibly high quality - very strong, and just 2 minutes with 120-grit sandpaper and steel wool makes each fin smooth on the faces and glass-like on the edges.
• Shock cord: 8 feet of 1/4" flat elastic for the shock cord plus a short length of nylon to mount it to the wall of the tube. Not incredibly strong, and below Madcow quality, but good enough.
• Parachute: 18" diameter circular black ripstop nylon parachute with 6 medium-length sewn-on nylon shroud lines. High quality and able to stand up to abuse; however, there is one tear in the edge sewing that is mostly merely cosmetic and takes 10 seconds with a sewing machine to fix.
• Launch lug: 6" of LOC 1/4" diameter launch lug. Decent quality.

To which I will likely add the following:

• Quick-link: simply to aid in changing the parachute.
• Motor retention: threaded rod between the motor mounts plus a few assorted nuts and washers. Will prevent the ejection charges from pushing the motors out instead of the parachute.
• Chute protector: 9" piece of aramid (Kevlar™) cloth that does not burn, to protect the parachute from the heat of the ejection charges. Will add with a quick-link to allow use on multiple rockets.
• Rail buttons: to allow launching off launch pads with launch rods or launch rails.

The total height is 9 + 30 + (12-3) = 48 inches tall. My second-tallest rocket after the Nike-Apache, my third cluster (after the Twofer and Multi-Goon), and my first 4-motor cluster.

Pictures, simulations, and actual building coming soon.