Monday, March 29, 2010

SS-18 "Satan"

This is the largest ICBM in operation right now, and it can either carry a single very large warhead (to greater than 20 MT), or many MIRVs (to nearly a dozen.)

But despite being a weapon, this is first and foremost a badass rocket that is pretty cool. Some day soon, it may simply be used to launch science missions.

Saturday, March 27, 2010

Orange nosecone

This nosecone and payload bay in one was taken from a cirrus dart kit that is no longer in use. It is about 8 oz, in other words, rather heavy. The cirrus dart uses a solid plastic nosecone. This will be used in addition to the stock nosecone for the thunderbolt 38mm kit when it flies soon.

Clearly it has not been finished yet, one more coat is in order and then a layer of epoxy to lock everything up and make it shine.

Sunday, March 21, 2010

High altitude balloon images from the Lower Hudson Valley

This was a flight to at least 90,000 feet by a team located north of New York City. Normally these high altitude balloons seem to be flown in some location in the country, flying over farms and a grid of rural routes and highways. In these flights, even with the curvature and dark sky, it is sometimes hard to get a feel for the altitude. But now, being able to see all of long island (about 120 miles long), one can better appreciate what 100,000 feet means. Note that the very beginning of Long Island to the west (right side) is Brooklyn and Queens, home to more than 4.5 million people and this rocketry blog. Yet I can cover it up with a finger in this picture.

Balloon Images

Rail guides

The rail guides have been installed using JB weld. The rocket was held stable using the highly technical "pile of jackets" method. Some of the extra epoxy was used to repair a Stegosaur tail spike fossil. I always mix way more than needed, because it seems that very small amounts tend to mix poorly. JB weld is proving to be a very useful epoxy, having never really found a place in my rockets to date.

Friday, March 19, 2010

Slow posting means more building

Work has started on the 2 inch, 29mm Drago kit. Here is the motor mount assembly, with the top centering ring in place. A notch was cut out of the ring to allow the kevlar shock cord (thinner than in the 38mm thunderbolt) to pass down the side of the motor mount. Everything was tacked in place using thin CA. Sadly, the ring somehow wound up a bit crooked. I will now have to sand, crack, or dissolve the CA and redo it. Once it looks good enough, everything will get a thick layer of epoxy (maybe JB weld rather than 30 minute due to the heat exposure?) I plan to slide this motor mount into the rocket, and then CA the fins in place around it. The lower ring will be kept out so that the fins can be reinforced with fillets both inside and out of the rocket, per the technique used in builds particularly in the late 90s. The idea is to get a really solid fin mount so that this rocket can handle some serious performance and high speed recoveries.

This kit is very bare bones - there is no motor retainer, that is common, but there are not even any launch lugs! It is clear how they can keep the costs down, and someone with the basic experience needed should be able to take advantage of that.

Tuesday, March 16, 2010

Saturday, March 13, 2010

The Thunderbolt 38mm build continues!

Work on the 38mmThunderbolt kit has continued now that a new supply of gloves and epoxy has arrived. This rocket uses JB weld and 30 minute Devcon epoxy, the latter never being very popular among the "pro amateurs" but has always been my choice, and will continue to be for ease of use and reliable performance.

The hardpoint anchor was assembled, with a bead of CA applied to the threads to lock them. The Kevlar recovery line was tied in place, wrapped in thread, and finally "potted" (soaked) with a thin CA. The knot will take the stress of recovery, with the CA potting simply used to keep the knot secure over the years. The hardpoint anchor is like a small aluminum coupler, and it formed the base of a 38mm stack which was secured with a zip tie to ensure a tight fit. Ideally the hardpoint will be strong enough alone, but in this system the coupler also takes on recovery forces transferring them to the upper and lower airframe sections. All surfaces were sanded with a very coarse, 60 grit sandpaper which 30 minute epoxy seems to love.

During some downtime, I selected some extra brass motherboard standoffs (fairly heavy) to use as noseweight. There is no known stability issue with this rocket, even with J motors, because it is so long (see below). However, this is a particularly light nosecone. My concern was that without some extra inertia, the nosecone would eject but not help pull out the recovery system. 38mm rockets are always hard to pack, particularly with so much thick kevlar. There is a very real risk that the parachute will get stuck in the rocket, or as seems to often be the case, halfway out of the airframe. By adding an extra oz or so, I hope to help prevent this. Do you think this matters? Please comment below if you have some ideas about this issue.

Finally, the two airframe sections have been glued together. Even with some sanding and rotating, there was a substantial gap and what looks like a slight bend. These are probably both small enough to ignore at this point. My acme fin-can rockets always seem to have a nice spin to them anyway, which is fun. The joint will be filled and possibly slightly reinforced with JB weld next.

After adding the rail guides, and sanding down the nosecone to fit, I only need to drill a small vent hole near the top, and the rocket is ready to fly! No need to paint it just yet, fiberglass has a sexy look to it anyway (until it gets black inside from ejection residue that is!)

This isn't exactly as crazy as my 72 inch x 38mm model from back in the day, but boy it is still pretty long. This thing will be great on little H motors.

Tuesday, March 9, 2010

"The Rocket Project" by Sony

The Rocket Project

Building rockets with kids, and using rocketry and computers to teach science and engineering... great! Using this project as a chance to sell overpriced laptops... eh predictable, not so bad I guess.

But why the arrogant (and highly misleading) statement about the power of a Sony laptop as compared to a LM computer? "Todays Sony Vaio has more computing power than the first rocket to reach the moon." Now first of all, this could only mean the LM. But allowing for a first minor lie, and seeing that these words come over the Saturn V, I assume they mean the IU computer. Either way, this is nothing to boast about. It is a safe bet that most computers since the 1980s have had this much power. My cellphone probably does.

All of the SONY mistakes aside, this was a great idea. If only Alcoa or some other company that knows when to keep the product placements under control had sponsored this. As if these computers really launched the rocket...

Looking forward to the launch, hope they make space as planned!

Get the best deals on laptops at!

Intercontinental Ballistic and Cruise Missiles

Saturday, March 6, 2010

The best packages are 60 inches long and 4 inches in diameter

As if one fiberglass rocket were not enough, I now have two kits to build! A Wildman Drago just arrived, bundled with a pro 29mm motor (a promotion from a few months back.) However, rather than come with the so-so 3 or 4 grain case, this one came with a somewhat scary looking pro 29 6 grain XL! Yikes, that is just asking for trouble - these are big H and little I motors. Probably it is best to build one kit at a time, so the 38mm kit will go first as soon as I can get a new batch of 30 minute epoxy. It has already used more JB weld than in previous builds, which is an interesting test, but some parts require the fast, crystal clear stuff.

Dropping almost $300 on rockets in a few months is unprecedented for this rebar, with limited amounts of income, but it feels pretty good!

Wednesday, March 3, 2010

Thunderbolt 38mm step 2

The ACME fincan was added today, using more JB weld. The mix out wasted more JB than expected, so a smaller amount was used. Hopefully this will still be enough, about 4 pea sized drops were used, and the can (very tight on this airframe) was forced into place and rotated a few times to spread the epoxy. A thin layer remains on the fin canister, it can be sanded off later. This will take another 24 hours or so to cure.

Da Oith

Imagine some day launching a rocket and getting onboard footage like this?

Tuesday, March 2, 2010

Finally step 1 completed on the Thunderbolt

The Thunderbolt 38mm Kit is finally on the way to being built. It took me this long because the snap ring retainer, a Gaint Leap slimline, was WAY too small for a fiberglass airframe. I estimated a full 1 mm ID too small. After much sanding by hand, I had to take it up a notch and use the Dremel, which still took about 30 minutes because (obviously) aluminum parts get VERY hot when machining. The part was finally able to fit (when hit on the top with a text book, invert. biology to be specific) and it is now curing with some JB weld. The extra JB can be seen curing in an old grape jelly lid; this is some great epoxy.

The sanding was harder for me than it would be for others with a proper rocket shop and some big tools, but around here it is a coffee table and Dremel. Having said that, this retainer does not seem right for this kit in fiberglass. It would be asking quite a bit for giant leap to pre-sand this part, but it would make this much more like a almost ready to fly kit, as advertised.

All this work is soon forgotten, however, as the anticipation of flying this rocket in April builds.

Next up will be the acme fin can, the hard point anchor, and final assembly of the airframe with a coupler at the center. With the purchase of some 30 minute epoxy, the rest of the rocket should be done within a week or so. Maiden flight will be a pro 29 G motor.

All too often, I find that my kits wind up full of minor mistakes or compromises. As part of my rocketry education, I hope to eventually build kits slowly and more carefully, and focus on the details.

Monday, March 1, 2010

How to make the perfect nozzle

PWR Engineering

Expect an update on the construction of the 38mm fiberglass rocket soon. Not much work yet because of an extremely tight fit on the slimline retainer - so far 1 mm or so sanded off of the ID and still no fit. Obviously it is made for phenolic airframes and is just way too small for fiberglass. Next time I may just take a dremel to it - sanding anodized aluminum is harder than expected!