Wednesday, September 30, 2009

Vortex tube!

Cool thing I discovered in a book the other day: the Ranque-Hilsch vortex tube, usually just called a vortex tube (for obvious reasons). It's a simple tube, with no moving parts, that has an airflow looking like this:

It works by creating a vortex of air. The outside vortex is fast-moving with lots of kinetic energy, which creates a high temperature. The high-temperature air escapes out the sides of the cone, while the cooler, slower air inside is forced into the inner vortex and out the other end. Middle-temperature air cannot go out either the inside or outside holes, and hence must go to one extreme or the other before it leaves the tube.

It's less efficient that normal AC equipment, and it needs a lot of heatsinking for constant use, but it's good for spot cooling when a supply of compressed air is available.

It may work with some liquids as well.

It's also been used for uranium enrichment, in a process called Helikon vortex separation. It's been used by South Africa to produce both reactor-grade (3-5% 235U) and bomb-grade (~90% 235U) uranium. It requires huge amounts of electricity and cooling devices, but it does work, and it's easier to hide than centrifuges.

Twofer finished!

Today I painted the Twofer. One coat of dark blue, then red on the fin area fading into the blue. It looks awesome; pictures coming.

Dear Asshole Car Salesman

Your job is to make people want to buy cars from you. Yes, I know you work on a comission basis, and a sale now is your biggest priority. But people gather opinions on you based on how you act towards them, and that'll make a difference later in whether they look at your cars again, and what they tell their friends about your dealership. Treating a customer poorly just because they're not going to make their purchase in the two days remaining this monthis a bad idea. Effectively ignoring one because you know they're not going to make a big decision without their spouse their is even worse. Just because someone is only looking and is probably not going to give you a sale right now, is not an excuse to be an idiot. Your business is personality, and you fail. Asshole.



Tuesday, September 29, 2009

Doin' Some work: Twofer update

Pyramid: currently mostly stalled until I can actually get something done on cutting the sides.

The Twofer is doing somewhat better. I got the fins (two Baby Bertha fins, 1/8" thick) glued on and fillet, the engine mounts glued in and plugs put in to direct the ejection gasses forward, and the shock cord mount attached. I then swing tested it, but it wasn't quite stable. I finally added more clay and some metal bits to the nose cone, and then I tested it again. It was stable even at pretty low speeds, and I was able to let out about 20 feet of string to test it.

It's about 21" long and roughly 1.3oz unloaded and without a chute inside. The CP is about 15" behind the nose tip, right near the front of the fins. Loaded with two 13mm motors, the CG is somewhere near 13" aft of the nose tip, so stability is actually pretty good now.

I put on a 3/16" launch lug primarily because I'll need to launch it off the away pads at CATO in case it's unstable. The lug is between the fins, so there's plenty of access for hooking up the cluster on the side away from the rod.

Simulations, using modified RASP-93 running on my TI-84 with custom motor files. Equivalent motors are based on actual thrust, not designation.
2x 1/4A3-3T: 63 ft / 62 fps / 1.8 optimal delay. Ejection at roughly 10 feet. no good. (=1/2A4-3)
2x 1/2A3-4T: 213 ft / 124 fps / 3.3 optimal delay. Ejection just after. First flight. (=A5-4)
2x A3-4T: 526 ft / 212 fps / 4.6 optimal delay. Ejection just before. (=B4-4)
2x A10-3T: 513 ft / 206 fps / 4.6 optimal delay. Ejection early. (=B5-3)
1/2A3-4T + A3-4T: 369 ft / 155 fps / 3.8 optimal delay (A3), 4.4 optimal (1/2A3). Ejects just before. (=B3-3)
1/2A3-4T + A10-3T: 364 ft / 154 fps / 3.8 optimal (A10) 4.3 optimal (1/2A3). Ejects just before. (=B4-4)
A3-4T + A10-3T: 520 ft / 205 fps / 4.5 optimal. Ejects early. (=B4-3)

I also simulated it with a pair of Apogee C6s. 1800 ft / 570 fps / 7 optimal delay.

Monday, September 28, 2009

Aerotech Spacers Out!

Aerotech has officially released a spacer system for their 38mm RMS system. It's a bit different from the Cesaroni system, though.

The Cesaroni system simply uses metal spacer tubes that fit inside the motor, taking up the space of one grain. The AT system is a bit more complicated. It uses 3 parts: metal spacer tubes like in the Cesaroni system, a floating forward closure that can go anywhere inside the motor tube, and a choice of forward closures. One allows the case to be used with its normal-sized reloads as well as smaller one and has a large hole in the center; the other only allows use with spacers (ie, use of a 360Ns case with 240 loads but not 360 loads) but provides an eyebolt attachment for your recovery system.

Aerotech recommends using no more than 2 spacers per case, but theoretically 5 can turn a 38/1080 motor into a 38/120 motor. Imagine being able to use G and J loads in the same casing! The only penalty is 1.9" of case length (over the usual case) and about 50g (1.8 oz) per spacer used. In other words, a 360Ns case with one spacer is 1.9" longer and 1.8oz heavier than the 240Ns case alone.

Currently, the system is not yet certified, but this is expected to come by mid-October. The standard new closure, which allows use of the nominal load for the case plus smaller loads, comes with 2 spacers and the floating forward closure for $29.99. The anchored forward closure, alone, is $19.99.

29mm and 54mm systems will likely join the 38mm system soon. I will certainly buy the 29mm system so I can use 60Ns and 120Ns loads with my 180Ns case. (The 100Ns case uses non-standard-size grains and thus wouldn't work with the spacer.) Aerotech is not sure whether they'll make 75mm and 98mm versions only because they would carry significant weight and length penalties versus the nominal size casing.

Like other Aerotech stuff, this isn't necessarily as simple to use as the Cesaroni version, but it's not too hard, and I personally like assembling my own motor from individual parts. Using a Cesaroni load, which is preassembled, seems like no different from using a single-use motor.

The announcement on TRF, Rocketry Planet, and Aerotech's website.

And now, for your enjoyment, my first embedded Youtube video, which shows the assmbly of the new spacer system and 2 test firings.

Sunday, September 27, 2009

Happy 11th, Google!

As seen in their logo today, Google is 11 years old. That's pretty impressive - in just over a decade they've become the dominant name in search, blogging, email, and more. I personally use them for email, blogging, photo hosting and organizing, following blogs, and more.

Saturday, September 26, 2009

Up in Massachuetts

I'm currently up in Massachusetts at Generic Small Liberal Arts School™ visiting my sister, so I didn't really get anything rocket-wise done today. I have, however, been conclusively beaten in chess and checkers by a friend of hers.

Friday, September 25, 2009

Wildman Order Came!

It came sometime between 5 and 9 tonight while I was at marching band. I was shipped HAZMAT even though it didn't need it; I'll have to call and ask about that since I was expecting 8 bucks for shpping, not 35.

The 29/40-120 case is very impressive. It's bigger than I realized - much closer to the size of the 29/180 case than the 24/40 case.

Thursday, September 24, 2009

In Lieu of an Actual Post

The combination of high school in general, marching band, history, starting a thesis paper, doing calculus homework, watching CSI and the Mentalist, applying for NHS, doing crazy chemistry homework, emailing colleges, trying to figure out how to take the SAT and subject tests, programming, dealing with somewhat computer illiterate parents, working 8 hours a week, not being at home this weekend, building rockets, and trying to improve his relationship has driven the EGE to the point of near insanity. You very well might get filler posts for a few days while he gets some reading and homework done and then is gone for 2 days, but you'll get a brand new post, with some actual content, every day. That's my promise.

Wednesday, September 23, 2009

The Twofer

Finally, soemthing other than that pyramid!

The Twofer is from the 'let's try crazy S#!+ and see if it works' files. It's a 2x13mm cluster rocket based around a 24mm body tube. the body is flattened at the motor end to accomodate the two 13mm motor tubes. The body is about 15" long, and the nose cone is a 24mm parabolic cone from Apogee.

Oh yeah, it's only gonna have two fins.

The 2-fin concept is based on this rocket from EMRR, which unfortunately never got to fly to prove the concept. I'll be making the fins nice and big. Because they'll be about 60° apart on the body, no matter how you turn it there's still a large amoutn of fin area visible, and therefore corrective force. Compare this to 2 fins located 180° apart, where from side angles there's no correct force.

I've gotten a bit done on it tonight. I put about half an ounce of clay in the nose cone and glued it together, and I cut and glued two 13mm MMT tubes together. I also flattened one end of the body tube and slathered wood glue on it to fix it in that shape.

On the pyramid, I reinforced the square plate that holds the motor mount with wood glue and finished reinfocring the motor tube.

Tuesday, September 22, 2009

Random Stuff

Made a bit of progress on the pyramid. Cut a bit of stuff; put a layer of glue on the motor mount tube for strength and the bulkhead for ehat protection.

Facebook and Google Friend Connect / Following are being fussy and not always working. This makes the EGE unhappy. He wants to find more cool blogs!

I've been reading some interesting stuff about submarine warfare in the Cold War recently. History day posts to follow.

Monday, September 21, 2009

My parachutes

Because I don't have much time and I've got nothing new to post, I did a count of all my chutes:

12": 9 hexagonal (1 in Astrocam)
16": 1 hexagonal (in Nantucket Sound)
18": 1 hexagonal (in Alexi Leonov)
32": 1 octagonal

4": 1 green(attached to little plastic army man for air-dropping)
6": 2 green
12": 1 formerly green, currently on Lord Gavin somewhere in Salem
16": 1 red octagon
17": 1 purple hexagon (in Mozzie)
18": 1 green octagon
20:" 1 green octagon
24": 1 green octagon
28": 1 red circle (in Nike-Apache)
30": 1 orange / black octagon
42": 1 red square

Total: 12 plastic, 12 nylon, 24 overall.

Actual, meaningful content returns tomorrow.

Sunday, September 20, 2009

For those about to 'WTF?'

If you're finding yourself, here, there are several possibilities. You may know me, or be a fellow rocketry blogger, or you may be the auhtor of one of a few other blogs I read. You might have found this blog from a Google search, either intentional or not.

However, there's a pretty good chance at least some of you are readers or authors of one of the approximately 10 blogs I found and commented on tonight. If so, then read here. The Amateur Geek is primarily a rocketry blog. If you're interested in rocketry at all, then some of this might make sense. TRF and EMRR might help with the confusing stuff. if you're not interested in rocketry, then there's still a lot of cool stuff here. Thanks for visiting.

More Progress on the Pyramid

The single assembled side is complete. I've put 3 total layer of fillets on, and with a bit of tape to hold the glue I made the point nice and perfect and filled with solidified glue. I didn't get to cut anything out today, though.

The motor tube now has fillets on both sides of the centering rings, plus a notch in the forward rings for the kevlar to pass through. The forward end of the tube has been slathered with wood glue to prevent it from bending under thrust.

The outer tube now has the bulkhead thoroughly glued in with fillets on both sides.

I also finished doing the touch-up painting on the SpaceShipOne. All the epoxy clay and bare spots are now nice and white, and the red that scraped off the nose cone has been replaced.

Saturday, September 19, 2009

Lots of progress!

Orbital Transport:

I put the final layer of wood glue on, then sanded it when it was drying. I then put a single coat of white on the glider. It'll get another coat tomorrow; the main body, where weight is less of a factor, will get a coat of primer first.


I brushed on white paint to cover the grey epoxy clay, plus a few spots on the trailing edges of the wings and tail fins that weren't covered in the original finishing.


I got lots of work done. First, my dad cut out two of the 8 triangles that make up the main body. I sanded them and butt-glues them together with wood glue. It's currently drying.

Next, I started work on the motor mount. I decided to go with the conventional design used in commercial pyramid kits, where inside the pyramid is a square bulkhead with a large tube in the middle. Inside the large tube goes the motor mount tube with centering rings attached to it to fill the large gap. The parachute(s) goes between the inner and outer tubes and is pulled out when the motor ejects.

By pure luck my dad had a 54mm hole saw that precisely matched a 2" cardboard mailing tube I had lying around saved for something like this. I cut out 3 circles from my 1/4" plywood. Through one, I drilled 2 1/8" holes through. Through the other 2, I drilled 1" holes which I sanded (using a dremel disk on a drill) to 1.25". I cut a 5" length of mailing tube and a 6" lenght of 29mm tubing, plus 3' of 1/8" kevlar string.

I tied the kevlar string through the 1/8" holes in the bulkhead disk, then put a drop of CA (superglue) on the knot to hold it. I then glued the bulkhead into one end of the 2" tube. The 2" tube will be permanantly attached to the main body of the pyramid and will hold the motor mount and parachute during powered flight. The kevlar will tie around the motor mount and hold the whole thing together.

I wood-glued the two centering rings to the 29mm motor mount tube, which is 6" long - just big enough for the 5.994" length of the 29/40-120 casing I intend to use with it. Tomorrow I'll put fillets on the other side of the centering rings, the bulkhead joint, and the middle of the one assembled pyramid side, plus of course cutting out and gluing the other sides of the pyramid. First flight will likely be in November on a G53 Black Max reload.

New Rocket Vendor

Odd'l Rockets, which has just joined the World Wide Weird, is a new vendor which sells some pretty cool-looking odd-rocs.

Their current selection of three kits includes a 13mm badmiton birdie rocket, a 13mm Sputnik with a 3" foam ball body predrilled for the motor mount, legs, and launch lug; and the Breakaway. The Breakaway is much like the old Wacky Wiggler, but with a kevlar cord that won't burn through, plus balsa fins and nose cone. It flies on 18mm motors.

Interestingly, the birdie rocket has both A10-3Ts and A3-2Ts recommended as motors. I think he means A3-4Ts, as the -2 motor hasn't been made for a decade or two.

The designer, Hans Michielssen, has already done some interesting stuff that he's reviewed on EMRR.

Also available are a special spring to use in place of clothespins to hold rockets, especially gliders, up on launch rods, and a ceramic dome deflector to prevent exhaust from bouncing off the deflector and melting the rocket, as well as to provide a non-conductive resting spot for the clips.

Odd'l products are available at Jonrocket.

Friday, September 18, 2009

Pyramid Progress

I've got the 8 10" by 5" triangles drawn out on the 1/4" plywood, plus 2 of the strips that will attach to the bottom of the triangle pairs to stiffen them. Tomorrow comes cutting them out with a jigsaw and the designing of the motor mount.

I used a bit of epoxy clay to stiffen the broken boom of the SpaceShipOne. It's now safe for flight again - I'll use a C6-3 and a 16" nylon chute and plenty of recovery space. I also tried repairing an old rubix cube with the epoxy clay, but the bond wasn't good and about halfway through the second test solve it fell apart.

The wood glue coating of the Orbital Transport is nearly complete. The underside of the port wing-fin is drying; after that all I have to do is the two small fins on the bottom and the edges of the wing-fins, and then it'll be fully colored with a shiny smooth paintable finish!

Adding commented code for TI-RASP to the document continues. Hopefully I'll finish it within a week.

Thursday, September 17, 2009

Bought Motors

From Wildman Rocketry. He's having a 35% off sale on all Aerotech SU motors and reloads, which makes it cheaper than pretty much everything else out there.

What I got:
Rouse-Tech 29/40-120 casing
G71-7R reload
3-pack of E18-4W (24/40 load)
3-pack of F12-5J (24/40 load)

Edit 9/18 4:53 pm: A few things were not in stock... The lady I talked to at Wildman was very helpful on the phone. I'm getting F12-3Js and a G71-4R instead (all the medium delays sold quick) and counting on bonus delays.

Wednesday, September 16, 2009

xkcd Book!

I am now the proud owner of an xkcd book!

(Well, it'll take 7-14 days to ship, but it's ordered so I technically own it.)

Tuesday, September 15, 2009

Random Rocketry Stuff

Rocketry is slow today; it'll go back up once I buy a few things. Madcow Solar Express and possibly another kit from Apogee; 29/40-120 case and a few reloads if Discount Rocketry ever gets it back in stock.

I've got a few scratch builds that I'm currently planning:
  • 10" pyramid for 24mm and 29mm reloads
  • 12" diameter 29mm saucer that can use anything from an E16W to an I200W
  • 24mm diameter cluster of 2 13mm motors - my first cluster
  • 2-finned rocket, which'll be stable by having the fins about 90° apart

I'm currently spreading wood glue on the Orbital Transport in preparation for painting. The glider, main nose cone, and one full wing-fin are complete, with one wing-fin left to go. It'll be painted in white, and the Orbital transport look drawn on with fine-tippens and markers. It should be ready to fly by the Oct. 10th CATO launch.

Finally, I'm currently typing up the code for TIRASP V3.4, the latest version of my rocketry simulation program for the TI-84. It'll be published as a google document and posted on TRF. The document will contain fully commented and explain code, all the motor files plus information of creating custom files to add to your own program, known bugs (currently 2, none very annoying) and more.

Monday, September 14, 2009

Aerotech J99N

Apparently one of the test/futures/demo motor Aerotech has is the J99N endburner. I first found out about it here on TRF, where an AT rep says it has a 10-second burn time - one of the longest burn times available in any motor.

Some info on a test flight can be found here.

Here Gary Baumann notes that it's for 54/1280 hardware.

Update: certified on 10/26/09; full info here, and it's actually for the 54/852 hardware.

Sunday, September 13, 2009


I'm currently in the process of changing my labeling system for posts. HPR and MPR have their own categories now, only stuff actually relating to certification goes in Certification, and Model Rocketry only deals with LPR stuff now. Changing the labels will take a few days, but it'll be easier to work with in the end.

This is awesome.

Happened across this on TRF: redirects to the Aerotech website. Gary Rosenfield has an awesome sense of humor.

Saturday, September 12, 2009

Possible Issues with Blue Tube

This thread on TRF raises some possible issues with the new Blue Tube. Basically, when unreinforced, it can temporarily bend under high-heat, high-humidity conditions.

The bending is apparently because of their original use: a liner for large artillery shells. It needed to bend to conform to the shell as it experienced aerodynamic heating.

On the thread, Randy, the owner of Always Ready Rocketry, who is the primary dealer for Blue Tube responds. Yes, at Southern Thunder, under extreme conditons, 3" and 4" rockets, which were 8 feet long, bent somewhat in area without internal components. The bends were temporary and the rocket flexed back into shape in cooler, drier conditions. It took them a while to bend, and that was under extreme Florida conditions.

Randy also mentions that they're working on adding a binder to Blue Tube that won't bend in the sun. He says that once that is complete, it'll be the "holy grail of airframes".

In short, it's a minor problem that affects few that'll get better. I still plan to use 29mm Blue Tube for the eventual sucessor to the Machnum Force.

30" Chute

After a bit of work, my 30" chute is finished, although not tested. It's made of orange and block gores - 4 of each color - and they're shaped to make it slightly curved when unfolded. There's a 1" spill hole at the center to make the sewing easier and for stability in the air. The seams are double-stitched for strength and to make them flat. The shroud lines are extra-long (90" per line; each is attached to two adjacient corners) so it'll stay open and not twist so much. It folds pretty small - enough to fit in 2.6" and probably even 54mm tubes.

I'll test it tomorrow when the rain stops. Much thanks to my mom for doing all the sewing and hard work.

Friday, September 11, 2009

Joined TRF!

Finally joined TRF (The Rocketry Forum). I'm the 'The EGE' on there as well. (It's my username for pretty much every anonymous thing I do).

Thursday, September 10, 2009

Square 1 Cube

My newest geeky puzzle: the Square one.

What it looks like unsolved:

And solved:

It's a lot trickier than the rubix cube, and i'm only just figuring it out. I currently have it cube-shaped but not solved. I think I like the constant shape of the Rubix cube better.
This is the best site I've found so far.

Wednesday, September 9, 2009

Random Stuff

1) Been playing Nethack a lot lately. Great gobs of fun.

2) I'm starting to coat the main body of the Orbital Transport with wood glue in preparation for painting. It'll take 5 or 6 times, each covering about 20% of the balsa, to get it nice and smooth.

3) Ever wondered how many hamburger patties could fit into a tractor trailer? About 100 million, or enough for every third person in the United States.

Tuesday, September 8, 2009

Crazy Idea for Competition

Posted to the CATO forums:

Completely crazy idea that's been bouncing aroung for a while and I'd just like to get out there...

Just as a friendly event, try a combination of duration and spot landing. These are both easy enough skills to get at least moderately good at separately, but usually opposite landings - spot landing is close by, and duration well downrange. It'd be open impulse from MMX to G, inclusive - you can land real close with the samller stuff, but a larger rocket will get better duration. it'd also be open to all means of recovery except for R/C controlled gliders.

Scoring would be duration divided by distance from the target, times 100 to make the scores easier to work with. Thus, a 30-second flight landing 150 feet away would score a 20, while a 60-second flight landing at the same distance would get a 40.

I'll be happy to donate a prize if it's worth a try.


Monday, September 7, 2009

Nylon chutes!

Today I bought lots of nice thin ripstop nylon: 1½ yards of red, 1½ of black, and 3 yards of orange. It was about 7 bucks a yard (60" x 36") but I got it for arouund 30 bucks cause I had a coupon.

So far I've made a 16" octagon (8 shroud lines) and a 42" square (4 lines). The 42" chute is by far my biggest chute; it'll be used for the CATO pumpkin-lofting competition.

Update, 9/8 at 1150 pm: I've since tested both chutes. The 16" chute folds small (easily a 29mm tube, could possibly fit a 24mm tube), unfolds quickly, and looks great. The 42" chute won't fit into much smaller than a 2.6" tube, but it's huge and awesome. It unfolds slowly, but still pretty well, and it's so cool to see it descend really slowly even with 6 oz of weight under it.

I've also got the gores and shroud lines cut for a 30" octagonal chutes. It's got 8 gores, alternating orange and black; it'll have a 1" spill hole in the middle. It'll be my third-largest chute, and my first gored / multiple color nylon chute.

Any other chutes will have to wait for the purchase of more shroud line material.

Nantucket Sound Update

Now that the epoxy clay is dry and the clay secure, I printed out the nose shroud, assembled it with CA, painted it, and glued it on. The Nantucket Sound is now ready to return to flight; its third flight will be either on a D12-3 or and E18-4W.

Sunday, September 6, 2009

What I'll probably order

From Apogee:
Madcow Solar Express
PemTech Kraken
Assortment of centering rings, launch lugs, and tube couplers
Estimeted total cost: $95

From Discount Rocketry:
29/40-120 case
E18-4W reloads (3 pack)
F22-5J load
G71-7R load
G75J-M load
Recovery wadding
Estimated total cost: $110.00

That's a lot of money, but for the money I'm getting one motor case, 6 loads, 2 MPR rockets, a bunch of parts, and wadding. I might take out the G75 load, or the Kraken, if I don't wanna spend quite this much.

The DR order might be delayed for a few days because the motor case is out of stock.

Launch Report #33: LPR With the Cousins

I got to go out with the cousins today and launch a few LPR birds. My normal local field was being used by the little mini football players, so we had to use a smaller local field about 250' by 500' - a third the size.

First came Mach My Day on an A8-3. Nice flight to around 350 feet; it was a bit unstable and squirrely after burnout, though.

Second came the Odyssey on an A10-3T. Quick boost and nice recovery. The light aft bodt with big fins came down *slower* than the streamer.

Third was the first flight of SpaceShipTwo on an A10-3T. Boost was straight with only a bit of roll; it went to around 300 feet and came back at a good speed on the 4" nylon chute, which barely fit into the tiny body.

Fourth was the Nuclear Mosquito on a B6-4. It's such a great rocket: I love the colors and shape; it can use anything from an A to a D; there's plenty of room for a chute, and it's a fun, non-serious rocket. Ejection was just past at around 300 feet; the 12" plastic chute (originally from the Deltie Thunder) took a moment to unfold and it finally was under the chute at around 250 feet. It's an incredibly light rocket; the 12" chute was too much (as it was at CATO last month) and it drifted a long way. Next flight uses a 6" or 8" chute or a long streamer. It drifted over the trees, and looked lost, but a gust of wind caused it to miss the trees by literally 2 feet and land right next to me.

Fifth was Glider 2 on a B6-2. The new glider hook worked perfectly and the boost was fast and straight, with only a slight arc and roll, and the glider stayed attached till ejection at around 300 feet or so. The pod came straight down and was easily recovered; despite a steep bank (which kept it nearby), the glider went around 400 feet away as the crow flies and stayed aloft nearly a minute, coming down and recovered in an adjaicent cemetary. A sucessful flight; it'll fly on the same motor with a bit less bank at CATO.

Sixth was Mach My Day, this time on a B6-4. It corkscrewed once then headed off at a 45° angle over the cemetary; the last I heard was the ejection pop. If it's found, I'll get it back - I put my name, address, phone number, and email on it when I was planning it as a Machbuster that'd go half a mile high.

I flew 6 motors on 6 flights in 5 different rockets; one lost and no other damage with 5 sucessful flights. Totals: 137 launches on 158 motors in 54 different rockets (8 retired / lost / destroyed); total 1437.4 (12.3% K), per motor 9.1 (81.9% C) and per flight 10.49 (4.9% D).

Saturday, September 5, 2009

New Projects

To compliment my plans to buy a 29mm hobby case, I'm also planning to buy a rocket or two.

I want to be able to fly the Redline, Mojave Green, and Black Max G reloads for the 29/40-120 case at Salem, which pretty much requires staying under 1600 feet to ensure recovery. This requires a 2.6" rocket minimum; depending on the weight, 2.6" rockets can top out between 1400 feet and 2800 feet on ~110Ns G loads like those in the 29/40-120 and 29/120 cases. A 3" or 4" rocket would be preferrable, but those are more expensive, and 4" rockets risk being over 3.3 pounds, or too heavy to fly on a G other than the SU G80T.

Although I looked at rockets from other manufacturers, including some Cosmodrome kits (which I'll definitely buy more of in the future), and the Pemberton King Kraken, I eventually reduced my options to a range of about 8 rockets from Madcow. They're fairly cheap, incredible quality, and always a little quirky.

So, I asked my dad.

After rejecting the Patriot and MIM-23B Hawk ("We do Navy and Air Force in this family, not Army"), the DX-3 (too boring), the Cowabunga and Momba (he's too serious for those), and a few others, he settled on liking the Solar Express. It's a great rocket; I considered it my second choice for a certification rocket before settling on the Nike-Apache.

It's pretty cheap (around 50 bucks), cool-looking, and had high-quality stuff like a solid plastic nose cone, TTW fins, 29mm thick-wall motor mount, and a great recovery system with a kevlar / nylon cord combo, chute protector, and a 17" nylon chute, identical to the Mozzie's, that's great quality and will bring it down quickly but safely. I plan to paint it scarlet and grey and call it the Buckeye Express. An excellent excuse to use Redlines.

According to Apogee's Rocksim predictions, it'll fly to betwen 800 and 1100 feet on Fs, and 1300 to 1800 on Gs. Madcow's predictions suggest 570' on an E16-4W, 900 to 1300 feet on Fs, and 1600 to 1900 feet on Gs. I'll definitely fly it on E18-4W reloads in my 24/40 case, and on a G71-7 Redline sometime. My predictions are 250 feet on a D12-3 (marginal, a D21-4T would be better but more expensive), 500-600 feet on Es, 800 to 1100 on Fs, and 1200 to 1700 on Gs. (These are guesses only; my predictions may differ). It'll also have the capability to fly on Hs at NERRF-6 next summer. Scarlet-painted Buckeye Express on an H165 Redline to 2500 feet would ROCK.

I may also buy a Pemberton Kraken in the same order. I like the look of the King Kraken but it's just too expensive; this provides the same cool look in a smaller (1.64" diameter) rocket that can fly on anything from D12-5 and D15-4 motors, to Fs on absolutely calm days.

I'm also debating between scratch-building a 9" pyramid and a 12" saucer to use for low, loud flights on 29mm motors. Cast your vote in the poll in the upper right, please.

500 posts!

This is my 500th post. I like big round numbers, so this is a pretty big thing for me. (Before she starts yelling at me, I really ought to thank mandachan for getting me into blogging, and to note that she's almost to 400 posts herself).

It took me 9 months, minus two days, to get to 250 posts. It's taken me 6 more, minus 3 days, to get my second 250. At this rate, I'll get to 750 posts in 3 months minus 4 days - December 1st - and to 1000 posts 5 days before that. (Ah, the fallacies of extrapolating with only 2 datapoints...)

In a pretty much unrelated conicidence, this is my 365th post of the year. Since I had exactly 365 total on The Amateur Geek's 1-year anniversary, that means I've posted the same number of times - 135 - in the past 3 months (minus 5 days) then I did in the first 6 2/3 months of the blog. I hope that all this content I've been producing is interesting and informative; I think my writing has improved, and I'm pretty sure that I'm one of the most-content-and-cheese-filled rocketry blogs out there - right up with Dick Stafford.

And now, back to content you actually care about.....

Friday, September 4, 2009

Hummingbird glider #2

Ever since February, when I launched and lost and then found destroyed the glider, the pod of my Hummingbird and been sitting, waiting for a new glider. Well, now it has one.

It's made almost entirely of balsa. The wing is 3.5" wide and about an inch at it maximum chord; overall it's about 4.5" long. After some messing around with, it glides pretty well.

I colored it green with a grey tail and pink throat - like a ruby-throated hummingbird. It'll be a bit hard to find in the grass, but fortunately it won't be too hard to find in the short grass of my local flying field.

Epoxy Clay!

Epoxy clay may just have saved two of my favorite rockets from early deaths. First, I put a layer of epoxy to hold the clay in the nose shroud of the Nantucket Sound. This clay flew out on the last flight; the nose shroud was lost and it's temporarily banned till the clay is better held in. I still need to fully cover the clay with epoxy to prevent it from splitting and destroying the shroud, plus to print out and paint a new shroud, but it'll be fliable again within a week.

Second, I put a thin layer of epoxy clay around the edge of the eye bolt in the Mozzie. The internal nut, which is not accessable without destroying part of the nose cone and the plywood retainer disk, has been slightly loose at times. Just as an extra precaution, the layer of epoxy clay will prevent the eyebolt from completely pulling out if the nut fails. It'll stil require major surgery, but at least I'll still have the nose cone.

Specific Impulse Explained

Specific Impulse, Isp , is a term frequently bandied about in rocketry, but rarely fully explained. I've used twice, here and here, both times in reference to high-Isp Blue Thunder blends.

I finally found a sensible explanation of what exactly the specific impulse of a specific propellant is. It's the specific impulse per unit mass. For example, just over one newton (102g) of Black Jack propellant in the G75J reload generates 155Ns of total impulse; the specific impulse of Black Jack is thus around 150 seconds. On the other hand, the same mass produces 220Ns in the H220T, so the specific impulse of that formulation of Blue Thunder is 212 or so.

A sampling of Isp s for several types of propellant:

White Lightning (W): 205 (J570); 200 (G79) 186 (N2000); 192 (K550); 210 (D10W)

Blue Thunder (T): 213 (D21); 225 (F32T); 212 (H220T); 222 (J460); 231 (M2500)

Black Jack (J): 143 (E11); 149 (G75); 147 (I154)

Black Max (FJ): 143 (F23); 156 (G53); 152 (I225); 154 (K513); 151 (M1800)

Redline (R): 182 (F27); 209 (H165); 192 (J420); 194 (K1275) 188 (M2000)

Mojave Green (G): 201 (G76); 203 (H250); 203 (J500); 205 (L1390); 202 (M2100)

Warp-9 (N): 225 (G69 Endburner); 234 (G339 Coreburner); 228 (J1999 Coreburner); 219 (K1999N Coreburner); 210 (L339N Endburner)

Cesaroni Skidmark: 178 (G69); 168 (I297); 171 (J250); 180 (K675); 171 (l1410); 176 (L3400)

Blue Thunder and Warp-9 are roughly tied for the highest (most efficient); White Lightning, Redline, and Mojave Green are tied for second; Skidmarks a bit below average, and the Black Jack / Max motors the lowest.

Thursday, September 3, 2009

Thoughts on new reloadable motors

I've been thinking recently about getting a bit more hardware. There's a rather large gap in my arsenal between the 45Ns F motors I can fly in my 24/40 case, and the 155Ns G75J in my 29/180 case. There's a number of reload options in that range, but they're all either Aerotech loads (in Rouse-tech cases) or the Cesaroni Pro29 series.

Since I'm not looking for 60Ns F motors only, that eliminates the 24/60 and 29/60 cases and the Cesaroni Pro29-1G case (approxiamtely a 60Ns case). This narrows it down to a few options: The Aerotech 29/40-120, 29/100, and 29/120 cases, and the Cesaroni Pro29 2-grain and 3-grain motors.

I can eliminate the 29/100 case as well. It's very similar to the 29/120 case, but with a few differences. The 100Ns case has the G54W and G104T loads; the 120Ns case has the G77R and G79W. The G104T, because its average thrust is over 80N, cannot be flown at places like Salem without a waiver; I'm also not a big fan of Blue Thunder motors cause they don't produce any spectacular flame or smoke. For only about a dollar more per flight, I'd rather have the option of two different motors, one red and one white, which have a higher impulse and can lift even 3.3lb 4" rockets.

I can also eliminate the Cesaroni system. Although I like the simple assembly, adjustable delays, and variety of motors, it's just not practical for me. Although the cases themselves are cheap - slightly less than single AT / Rouse-tech cases of the same impulse range - it requires buying an aft closure - about 20 bucks - in order to use the cases, and a 15-buck delay adjustment tool in order to have the range of delays. That means for even a 2-grain (120Ns) case, I'm looking at about 60 bucks for the case, and then G reloads are around 20 bucks - not a substantial savings over SU motors.

That said, however, I will keep Cesaroni reloads in mind for the future. Once I'm 18, going for my L2 cert, and hopefully able to fly high-thrust Gs and H and I motors at Salem, the Pro38 series starts to look a lot more attractive. At that range, they start to get to about the same price as AT reloads, and the greater variety of reloads per case is a big plus. Plus, Cesaroni has one thing that Aerotech has never expressed any interest in: SKIDMARKS!

That leave the Aerotech 29/120 and 29/40-120 cases. The hobby case (40-120Ns) is between 40 and 50 bucks; the 120Ns case is between 25 and 35. I don't need to buy closures, as I already have a pair from my 29/180-240 system. However, the 15-dollar difference in initial cost is quickly offset - G loads for the hobby case cost about $2.50 less, and there's even more of a difference with E and F loads. Although I like the G77 and G79, I think the variety of cheap reloads for the hobby case wins out. It also has several other advantages: per-motor delays, instead of a medium delay for each motor; a better ejection charge holding system, different propellants, including Black Max and Mojave Green, and of course the ability to fly F motors. I likely won't fly E motors, though, as 24/40 E loads are cheaper than 29mm E loads.

Along with the case, I'll definitely buy a 3-pack of E18-4T reloads. I like the loud and smoky White Lightning propellant, and the -4 delay is good for the Mozzie, Nantucket Sound, 24mm saucer, and even possibly the Nike-Apache, although since my Nike-Apache turned out heavy I think F motors are a better choice. I'll also get an F reload or two, plus a G load.

I'm also looking into getting another MPR rocket. Currently I'm leaning towards the Madcow Scooter.

Wednesday, September 2, 2009

Awkward Wednesdays!

(clap clap clapclapclap)

Hey folks, Turtle Tuesday on Drowning in Turtles got delay to till today, but you really should go check it out. Mandachan's artwork is awesome!

Tuesday, September 1, 2009


A pretty cool calender. I think I want one.

No Thank You.

Someone from a site called zillionsb tried to post a comment on a post about 3 days old inviting me to send a link to them. The comment sounded like spam and twitter has suspended their account for suspicious activity, which usually includes spamming, so I deleted the comment. To any who might do this in the future, please revisit my policy at the bottom, with the important bits highlighted here for you:

LART weapons will be applied on spammers, trolls, overly obscene, self-promoting, or crude commenters, and anyone who pisses me off too many times. Deal.