Saturday, July 31, 2010

The EGE talks about what you're interested in.

Aside from the questions, there are clearly some thing you want to know about. I'll do my best to deliver:

July 10th: "Aerotech G71 vs G77":

The G71 and G77 are fairly similar motors. Both are Redline motors, with the awesome laser-red flame.

The G71 is a reload for the 29/40-120 hobby case. Its impulse is 107 Ns, at it contains 56.9 grams of propellant. It comes with delays of 4, 7, and 10 seconds.

The G77 actually comes in 2 slightly different styles. One is a reload for the 29/120 case (different from the 29/40-120). It is 105 Ns, with 58 grams of propellant and available delays of S (6 seconds) and M (10).

The other is a single-use motor, available in preassembled and loadable (different from reloadable) varieties. It contains 58.1 grams of propellant which generate 102.9 Ns of total impulse; available delays are 4, 7, and 10.

The bottom line: If you have the 29/40-120 hobby case, use the G71R reload.
If you have the 29/120 case, use the G77R reload.
If you have neither, use the G77R single-use motor. Choose the loadable variety if you want to save money and don't mind spending a few minutes building the motor.

July 12th: "best glue for ttw fin fillets mid power high power hpr rocketry":

Are you using fiberglass? If so, use epoxy.
Are you using carbon fiber? If so, use special high-temperature epoxy for carbon fiber.

If not, it depends on the application. For most uses, wood glue is excellent. It bonds excellently to paper / cardboard and all varieties of wood. It's incredibly strong, safe, and easy to use. It's cheap, sands well, and you can spread it into fillets with your fingers. It's slow to dry, though.

For attaching plastic, fiberglass, carbon fiber, metal, Blue Tube, or Quantum tube, epoxy will work better. It dries quickly and attaches almost everything. But, it'll stick to you, and it can cause allergies, so use *nitrile* (not latex) gloves.

A good compromise for larger rockets that need a lot of strength may be epoxy clay. It sets up rock hard, gives you plenty of time to precisely shape your fillets, and attaches anything. But it's expensive, and too much will be heavy.

July 12th: "blue thunder propellant formula":

Blue Thunder is a high-solids blend that burns very efficiently, with little smoke or colored flame. This indicates that it's almost pure ammonium perchlorate / aluminium blend, with few additives. I know very little about motor making; this site may be of help.

UPDATE: Thanks to Ken Kzak:

Blue Thunder is a high-solids blend that's mostly ammonium perchlorate and binders (PBAN and HTPB). Wikipedia gives one common recipe for high-performance, low-smoke motors as around 80% AP, 18% binder, and 2% metal. For Blue Thunder, that metal might be aluminium, magnesium, or copper.

July 13th: "rocksim file for madcow 2.6 patriot high powered rocket":

Madcow are awesome folk; I highly recommend their kits. On their page for the 2.6" fiberglass Patriot is a convenient link to the Rocksim file.

July 29th: "wisdom is knowing that you'll be an idiot in the future which qc comic":

Number Nine Hundred Seventy-six.

For the future, Ohnorobot is extremely useful, and searches over 100,000 panels of over 1700 comics.

Thursday, July 29, 2010

The EGE shows you: how to load an Estes Comanche-3

From July 9th: "how do you connect the engines on an estes comanche 3?"

You should have three motors for three-stage flight: A 24mm booster motor (C11-0 or D12-0), an 18mm booster motor (B6-0 or C6-0), and an 18mm upper stage motor (A8-5, B6-6, or C6-7).



First, take the 24mm motor and install the igniter in the nozzle. Install the motor in the lower booster stage (the one with no motor mount inside) with the nozzle facing down (away from the coupler).



Then, take the two 18mm motors. Take a 3" piece of scotch tape, and tape them together end-to-end so that the nozzle of the upper stage motor faces the black propellant (the end without a nozzle) on the booster motor. Wind about 5" of tape around the other end of the upper stage motor. This extra tape will prvent it from falling out at ejection.




Next, take the taped-together motors and push the nozzle end of the 18mm booster motor into the top of the lower stage. The nozzle will actually go about half an inch (12mm) into the top of the 24mm motor.



Then, slide the middle booster stage (with the motor mount inside) over the motors so that it connects with the coupler from the lower stage.



Finally, slide the sustainer (the long section) over the 18mm upper stage motor and connect it with the middle stage. Prep your recovery system and you're ready to fly.

The EGE answers your questions!

As I've mentioned before, I have Google Analytics code on this blog. It's very neat, because I can find how you're finding the blog, and what you're looking for in it.

Interestingly, some of you have gotten here by googling questions. Well, your questions are now getting answered.

From July 26th: "can i split a 6 grain cesaroni reload kit into 2 3grain reloads"

No, that's not possible. Each reload kit only comes with one nozzle and one set of forward components (delay, ejection charge, etc). If you took three grain out of a reload kit, you would only have three grains, and not a second complete propellant kit.

From July 10th: "how many ounces can a e30-4 model rocket lift?"

There's a convenient trick for this: The 5-to-1 rule. A motor should provide 5 Newtons of average thrust for every Newton the rocket weighs (4.45 N = 1 pound). For an E30 which generates 30N average thrust, The rocket should weigh no more than 6N at liftoff. That's about 1.3 pounds, or 21 ounces.

Now, the E30 has a higher thrust of around 45N at liftoff, and 5:1 is a bit conservative. If you're flying a very stable rocket in no wind off a long launch rod, you could maybe get a 32 oz (2 pound) rocket off the pad. But that's not guaranteed.

From July 16th: "lufthansa tour flight stopped from takeoff from cleveland hopkins airport because two guys were jokingly saying "hijack" to one another?g"

I don't even want to know. You're on your own here.

From July 8th: "wildman blackhawk or?"

Or what? The Blackhawk is an excellent kit, by the way.

Tuesday, July 27, 2010

Finishing the A. R. V. Condor

After some more building, the Condor is completely built.

First, I tied the shock cord to the nose cone and glued it to the upper body tube. Then, I glued on the upper glider mounts. CA is a wonderful thing.

Then, I put on the finishing touches. The three mini launch lugs were attached - one by the lower glider mounts, and a pair above and below the mid-body joint. Finally, I glued the lower end of the shock cord into the coupler, and it was complete:

Now comes primer, paint, and decals - a process lengthier and more difficult than building.

I also test-chucked the gliders in the yard. #1 flies nicely with a small intentional left-hand curve; #2 dives to the right which will be corrected after finishing.

A. R. V. Condor progress

Got lots of building done on the Condor today.

First, I finished gluing the wings together:


Then I glued the main nose cone together, and glued the coupler and motor mount into the aft tube:

Then, I glued the gliders together. Wings, tail fin, and mounting dowels.

Finally, I glued the plastic glider mounts to the aft tube:

Swords!

I've now tripled the size of my fake sword collection.

For Halloween last year, I went as a ninja. I decided this, of course, on Friday night, with about 21 hours till the party. I managed to cobble together a halfway decent sword. It was actually made of two old window blinds, with dowels down the center for hardness. Grip was made of masking tape and electrical tape, and I painted it with spray paint. Crude, but decent. I even managed to make a scabbard out of wood and masking tape.

Now, though, I've substantially upgraded. I've made a matched set of a katana and wakizashi. They're made of solid wood, with better grips, and painted silver with a brush for a nice even coat.

The katana has a 22-inch "blade" with a 6" grip; the wakizashi has a 15" blade and 4.5" grip. Both on the small side, and technically a katana should be between 24 and 28 inches. But these are good for a costume.

Monday, July 26, 2010

A. R. V. Condor

I'm finally starting to build my vintage Estes A. R. V. Condor, which I bought back in March at NARCON. Entries and picture are cross-posted here and on TRF.

The Condor is a really neat kit. It's got two parasite gliders which form the fins of the rocket, then detach at apogee and glide down separately. They're very tricky to build, but it should be fun.

I'll be building it stock, save for the motor mount. The engine block and motor hook go into my parts bin, and the motor mount will be moved back a bit so I can use tape for retention.

All the parts:
There's a total of 36 parts, not including the decals and the jigs to align the glider wings, but including the two motor mount parts which I will not use. That's a lot of parts.

Here's a closeup of the wings and tail fin for one glider:

And here's a closeup of the decal sheet:

I did get a bit of work done this afternoon; here are the 4 assembled glider wings:

College Essays

They've started.

I wrote two 300-words essays (in an hour no less) last night. My family has decided to bribe me with food.

It's working.

Saturday, July 24, 2010

Modest Mouse!

Tonight, I am going to see Modest Mouse in Wallingford. I'm going with mandachan, and some friends from ARML (state math team). It's going to be awesome!

Friday, July 23, 2010

Radioactive Steel

A interesting side note about nuclear testing: all steel made since 1945 is contaminated. For millenia to come. Radioactive iron and carbon isotopes from atmospheric detonations have introduced a very small amount of radioactivity to all steel produced. It's not a harmful amount. Not even close. It's been decades sonce there were atmospheric tests. It's not even detectable by most detectors. But, it's enough that certain sensitive detectors, particularly Geiger counters, cannot be made of radioactive steel.

Usually aluminium* can be used, but if it's not, then there's only one thing to do. Pre-1945 steel must be found that has not been exposed to air that carries radioisotopes. There's not a lot of it around.

Fortunately, water is one of the best moderators known. A few feet will stop a lot of radiation, and prevent the radioisotopes in the air from reaching any steel.

Now, no one had the bright idea to stockpile a bunch of steel underwater before the first atmospheric test, but we do have the next best thing. Shipwrecks. Thousands of tons of pre-radiation steel, underwater. Unfortunately, most shipwrecks are in inconveniently deep water. The deep waters of the Atlantic and Pacific, from WWI and WWII shipping and warships.

There is one source of convenient steel, though. In June 1919, Admiral Von Reuter ordered his German fleet scuttled under the noses of their British captors to spite them. When it was over, the scuttling of the fleet left 52 ships on the seafloor of Scapa Flow, a Scottish bay. 45 of them were later raised, but 3 battleships and 4 cruisers remain. Small piece are retrieved occasionally by divers for use in instruments.

What the Hell were We Thinking?

I'm almost finished reading a very interesting book about US nuclear weapons design and testing. Much of the information is only recently declassified. It's absolutely fascinating stuff. And profoundly depressing, just how willing humanity was to come to the brink of apocalypse and stare into the abyss.

A Japanese artist, Isao Hashimoto, made a flash animation of every nuclear detonation between 1945 (the Trinity tests, Hiroshima, and Nagasaki) and 1998 (India and Pakistan). It's very sobering, watching over 2000 blips on that screen. Each one wquivalent to between 100 and 50,000,000 TONS of trinitrotolulene (TNT). It's well worth the 13 minutes to watch. It starts out slow, but around 3:30 in it gets crazy.



The only possible detonations not shown are the 2006 and 2009 North Korean tests and the Vela Incident, a possible Israeli test in 1979.

Wednesday, July 21, 2010

Other Aerotech News

The J1999N, which had several spectacular failures at LDRS, has been redesigned for safety. The new motor is being sent to Tripoli Motor Testing for recertification.

The E30T has been changed to the new molded case with integrated thrust ring and recertified. Not a big change, but it'll hopefully be a tad cheaper and the new case is more reliable.

The F30FJ Black Max and F31R Redline motors have been submitted for NAR certification. They are 24mm single-use motors 95mm long, the same as Estes E motors, and virtual twins of the upcoming F33FJ and F34R loads for the 24/60 case.

The D3 reload for the 18/20 case is back in testing, after having been delayed.

Tuesday, July 20, 2010

Aerotech H load tested!

From Aerotech's Facebook page comes the news that they've sucessfully tested H loads for the 29/40-120 case. Range between 162 and 166 Ns total impulse - baby Hs - and 1.05 to 1.1 second burns. Delay time 14 seconds, adjustable by drilling or buying different delay kits.

Assuming 164Ns and 1.08s burn, that's about an H152-14T.

Delivered Isp was 237.4 with 70.4 grams of Blue Thunder propellant. Core size was slightly over 1/4". The motor operates at around 650 PSI.

It's a single-grain load requiring hazmat shipping, but I buy my high-power loads at the field anyway. Price should be under $20 per load, available in a month or two.

The burn is heavily progressive, sloping from 90N to 180N thrust over the first second.

Photo on Facebook

Wednesday, July 14, 2010

Going to Ohio

I'm going to Ohio for a few days, then visiting the University of Maryland and riding the train home. Blogging will be light, as internet is spotty in Amish country. (No, I don't know why my uncle lives in Amish country. He's not Amish.)

...and then more stuff when I come back in a week.

Tuesday, July 13, 2010

Eco-friendly dowels

In which I mock 'green' products of decidedly inferior quality.

Regular 3/8" x 24" dowels, made from OMGWTF EVIL WOOD THAT EATS YOUR CHILDREN AND CAUSES TOENAIL CANCER, cost 99 cents at A.C. Moore. They're smooth and made of high-quality wood that is hard to break.

The supposedly eco-friendly dowels are not 24" long. They're perhaps 22" long. Ish. They're rough wood, that will give you environmentally wonderful splinters. They're only half as strong as the hardwood dowels.

And they cost $3.79.

Sunday, July 11, 2010

SR-71 plastic model conversion

I've finally got some decent work done on the SR-71 conversion. It started out a non-flying 1:48 plastic model weighing 11.1 ounces. It took up a lot of space and didn't do anything interesting. Not acceptable.

So, clearly, the thing to do is to stick a rocket motor in it. 18mm just wasn't going to cut it - with any noseweight, it'd be underpowered even on D24Ts. So, 24mm it was.

First, I did some surgery. I cut off the tailcone to accept a 24mm diameter internal tube. I removed the landing gear doors, cut out some internal bulkheads that obstructed the tube, and replaced the doors. I cut off the body just forward of the wings, and the 2" tip of the nosecone.

I took a 15" length of 24mm tube and put it through the main body, with 1" sticking out the aft end for motor retention purposes, and 3" out the front to couple with the nose section. I glued a shock cord and a bunch of BBs into the very tip of the nose cone, then reglued the tip to the main nose cone. I glued two dowels inside the nose section to keep it in place when it's attached to the body section.

(It makes a lot more sense when you're doing it, rather than reading it. Sorry.)

Then, I glued the shock cord to the sticking-out section of the internal tube. Finally, I took black paint and painted over all the exposed sections of white tubing, broken plastic, etc.

It looks pretty nice, and it should fly nicely on high-thrust E and F motors. First flight will probably be on an F35W

Saturday, July 10, 2010

More on the 29/40-120 H load

All information from Facebook and TRF.

The new baby H will use an optimized Blue Thunder blend, as I suspected. 70g of propellant, for an Isp around 235. It will have a delay and ejection charge, and uses a normal 29mm high power nozzle, modified liner, and longer-than-usual grains.

There's some speculation on TRF that the high operating pressure may cause delay issues.

According to Gary Rosenfield (of AT), once the NFPA 1125 rules change in 2011 and the propellant limit on model rocket motors jumps from 62.5g to 125g, they'll likely make a full G (160 Ns) motor for the case as well.

Cosmonaut Alexi Leonov

So, you may be asking, why did I name the Alexi Leonov as such?

It's named after one of the greatest Russian Cosmonauts - Alexey Arkhipovich Leonov. (Alexi is one of several English transliterations).

He was the first man to walk in space in 1965. For 12 minutes and 9 seconds on March 18 of that year, he stepped outside the Voskhod 2 spacecraft, connected only by a thin 17-foot tether. He had the world's greatest view, but he soon encountered problems. His suit soon ballooned, costing him mobility and preventing him from operating cameras. The temperature rose; he was 'up to his knees' in sweat and his body temperature rose 3.2°F (1.8°) - a dangerous rise.

He could barely get back in the airlock; he got temporarily stuck. Much longer, and he would have been forced to swallow his suicide pill. He had to risk decompression sickness by releasing air from his suit. Their automatic reenty computer failed and they had to land manually, then spend a cold night in a forest surrounded by wolves. When asked later, though, he modestly downplayed the danger.

In 1975, he flew on Soyuz 19 - the Russian part of the Apollo-Soyuz Test Project. The ASTP, with the symbolic handshake in space, effectively ended the Space Race and was a major moment in achieving detente. During the mission, the crews spoke in each others' languages; Leonov joked that there was "Russian, English, and Oklahomski", referring to Tom Stafford's pronounced accent whilst speaking Russian.

He is now perhaps the most famous Cosmonaut, and still alive at 76.
From Wikimedia

His name was given to the central spacecraft in 2010 by Arthur C. Clarke.

He's also an accomplished amateur artist; his most famous work is "Near the Moon", painted in 1967. Interestingly, it's almost identical to the opening of 2001: A Space Odyssey, which Leonov noted to Clarke at a 1968 screening.

From Wikipedia

Before and After: Alexi Leonov

Looks so much better painted, don'cha think?

Friday, July 9, 2010

Big 29/40-120 reloads

From the Aerotech Facebook page (the only thing I still legitimately like about that site anymore):

Today, they tested a new 29/40-120 reload. It generated 150 Ns of total impulse. That's a whole lot more than the current G loads for the case, which top out at 120 Newton-seconds (G64). (G76G is 115, G71R is 107, G53FJ is 91).

That means it must have been a high-impulse Blue Thunder blend (the only more efficient propellant, Warp Nine, isn;t used in such small cases), with an Isp (efficiency) of 245 (assuming 62.5g of propellant, the max that usually fits in the case). That's very high; most blends top out at about 200. See previous post.

The burn time is apparently 1.17 seconds, for what is about a G128T. That's an awesome motor, and would kick some major ass if it's released as a commercial load.

But it gets better. Oh yes.

They're looking to put an H load in it. Obviously a baby H - just over the limit at 161 Ns or so. Average thrust between 100 and 120. That's pushing 263 for the Isp for 62.5g of propellant. Even if they've got 72.2 grams - the amount in the old G33J, and the maximum that'll fit in the casing - that's still a nice high 228.

I thoroughly approve of this, and I really hope they get a motor to market. I have several rockets - the Mozzie chief among them - that could rock on a big G or baby H, but can't quite fit a 29/180 casing.

Also, since it's a small amount of propellant, it'll be cheap. And everybody, it seems, has the hobby casing (29/40-120) for mid-power stuff; it'd be cheaper to certify with that than by buying the larger casing.

Painting

Painting the Alexi Leonov:

Primer

sanding, sanding, sanding

primer

more sanding

Coat 1: blue and grey

(wait)

(wait some more)

Coat 2: silver and white

(wait)

See that the white didn't come out well

Coat 3: white

still waiting...

Wednesday, July 7, 2010

Dear bad driver

Dear driver of the white Accord, licence plate starting with 520, who happened to be traveling north on Interstate 395 in Montville at 2:15 pm this afternoon:

I realize that you had just gotten on the freeway, only to realize that you were behind a tractor-trailer, an RV, and half a dozen other cars. I realize that your selfish ego could not stand waiting a few minutes to pass and speed on down the highway, when traffic had spread out a bit. But I cannot for my life understand why you though it would be a good idea to suddenly pull into the left lane to pass without checking your mirrors, putting your blinker on, and being prepared to speed up to match the higher speed of traffic in the left lane.

You see, after the red SUV, there was another car in the lane, about 4 seconds (400 feet) behind. Me. By the time you decided to make your move, I was only about 20 feet behind you, going 65 to your 50. Fortunately, I had noticed your oh-so-typical movements, wandering back and forth in your lane, and the moment I knew you were attempting to merge into me, I had the presence of mind to slam on my brakes - never mind the cars behind me - and hit the horn.

While you took your jolly old time, slowing to 45 before realizing you have a functional gas pedal (that will within minutes take you far beyond the speed limit), I got within a yard of your bumper before my brakes slowed me to your speed. You never even knew I was there until I hit the horn. Had I been momentarily frozen or distracted, much less doing something truly stupid like texting, you would have lazily sat there until I slammed into your rear end.

And at freeway speeds, we would have been in deep shit. At least one of us would have been pushed into the lane from whence you came, thus setting off a chain reaction that would have consumed a half a dozen vehicles that couldn't get out of the way, plus more from behind that couldn't stop. It would have been a spectacularly horrific collision. They would still be picking bodies from the mangled steel. And there would be a lot of bodies.

Don't you see, you idiot? Your inability to follow basic rules of common sense put many lives at risk, and you sat there, oblivious. I'm a new driver; I shouldn't have to be wary of adults you act like children. Think before you act next time, you goddamn fucking asshole.

Tuesday, July 6, 2010

Some Pictures

Here is the boost pod for the Deltie Thunder. It's been shortened by about 6" to remove the crimped section. The lighter plates on the glider hook are basswood stiffeners, and the dark spot on the nose is wood filler.
















Here is the Alexi Leonov in the process of rebuilding.
















And here is my newest project, the 1:48 scale SR-71, weighing in at 11.1 oz before modificiations.

Posted by Picasa

NERRF Drag Race Picture

Two days ago, Jim Flis, owner of Fliskits, posted his album of NERRF pictures of TRF. You can few the whole giant album here.

One picture, I found, was described as a "HPR drag race". Well, there weren't many of those, so I took a look. Sure enough, it showed two skinny rockets and one fat - the drag race between Crazy Jim and I, with a third rocket launched at the same time for kicks.

My Sudden Mach is on the left, on a G78G. It's about a foot taller than Crazy Jim's Blackhawk, just to the right, also on a G78G. The third rocket, whose name and owner I do not recall, is on a J800T. Our two rockets are almost keeping pace, despite having a tenth the thrust of the larger rocket.

Once again, thanks to Jim Flis for the picture.

Monday, July 5, 2010

How to predict the lunar phase

So, you're an astronomy geek like me, and you want to know what the moon will be like during the Perseid meteor shower. Or you're planning a camping weekend and want to have a new moon to better see the stars. Or you're tired of how-many-cool-ways-to-break-a-bottle and you want a new party trick.

You want to calculate the phase of the moon on a given day? I can do that. It's actually pretty easy.

For 2000-2019:
Add 2 to the last 2 digits of the year.
Multiply by 11.
Add the month and day.
Cast out 30s.
The remainder is the number of days since the last new moon.

0 is a new moon; 7 is first quarter, 15 is full moon, 22 is last quarter.

For example: 5 July 2010
2+10=12
12*11=132
132+5+7=144
144-30-30-30-30=24

The moon today is thus 2 days past last quarter. It's a waning crescent and rises between midnight and dawn.

Here's the kicker: Thanks to the Metonic cycle, you can go forward or back 19 years, and the phases are the same. 1981, 2000, 2019, 2038, etc are all the same. This stays accurate for a few centuries either way; it gets off by a day every 219 years. For future dates, subtract one day for every 219 years from the calculated lunar age; for the past, add.

Just don't forget about the Julian/Gregorian switch, a 10-day gap in 1583 for Catholic countries and 13 days in 1752 for Britain et al.

Just an example of how accurate this method is: take November 12, 1594. 1594 is 418 (=19*22) years from 2012.
2+12=14
14*11=154
154+11+12=177
177-(30*5)=27
418 is about twice 219 years in the past, so add two days and it's 29. One day from new moon.

In fact, November 12, 1594 was a new moon and an annular solar eclipse. Over 4 centuries, this little arithmetic trick is accurate to one day.

Originally published in Sky and Telescope magazine, November 2005 issue, p.130. If you want the full text, let me know.

Epic repairs session

I had lots of time tonight, so I managed to get a lot done on repairing rockets.

My biggest project was the Alexi Leonov, a slightly modified Estes Loadstar. It hadn't been built too well from the beginning, and these latest mishaps just made it worse. The fins were crooked and loose, the booster didn't fit right, the booster motor mount was crooked, and my original decorating was pathetic. It's five years old, and back then my finishing abilities were limited to putting decals in sortof maybe the right places. No paint, just decals and some random stuff written with marker. It was ugly.

And then it got worse. Last February, I fried the upper stage motor mount and replaced it, badly. Two weeks ago, it pranged and ejected the motor mount - the glue joints had failed. Then I knocked it over and it lost a fin.

So, I decided to give it some justice. Proper fin job, better internals, and a nice looking paint job. I peeled off the decals, rubbed most of the adhesive off. Removed all the fins but one each on the booster and sustainer. Sanded all fins smooth, and sanded the body tube where the fins had been. Drew up fin alignment guides in Word, printed them out, glued all fins on nicely with superglue; the firsy round of wood glue fillets is drying.

Then I started on the internals. I removed a broken centering ring on the upper stage motor mount, cut a new one from cardboard, and glued it to the motor tube. I reglued a centering ring on the lower stage motor mount to better align the motor. Finally, I cut down and sanded the interstage coupler so it fits perfectly.

If you're confused, don't worry. Pictures are coming, as well as a really nice looking paint job.

Second, I worked on the Deltie Thunder's boost pod. I cut out the crimped section of tubing and moved the glider hook and launch lugs further up. (I checked stability; it's good even with the shorter pod.) I sanded the broken bits on the hook to fit the matching hook on the glider and added outside plates for stiffness. Finally, I filled the dent in the balsa nose cone with wood filler, sanded, and coated with wood glue.

Third, I added protective layers of glue to the 5x13mm motor mount of the Multi-Goon to protect it from ejection charges.

Fourth, I reglued the nose cone on the Sudden Mach. It's now fully repaired and ready for business.

Fifth, I reglued a few paint chips on the Svetlana. The baffle and the Heli-roc will have to wait for later, though.

Saturday, July 3, 2010

Simulating the Fleet

After almost 7 months of having Openrocket, I've finally simulated all the fleet. Well, almost. I still have to sim the Nike-Apache - the most complex rocket in my fleet, with its multiple finsets and transition section. That's next.

There's also a few other that I likely won't do. The SpaceShipOne and SpaceShipTwo have build-up fin units with many angles, as does the Orbital Transport and most of my gliders. The Heliroc is just plain weird. If I get really bored this summer, I might give some a shot.

Friday, July 2, 2010

Starting repairs

Between NERRF and my personal launch, I have a lot of rockets to fix in some capacity or another.
  • Alexi Leonov: its last flight ended with a crash and the entire motor mount ejecting out the back. The centering rings are pretty shot and the motor tube needs replacing, so I'll put in a new mount with basswood centering rings and a better motor mount tube. I will probably also add fillets to the fins and maybe even paint it. Also, I'm an idiot, I kinda tripped and hit it and knocked a fin off.
  • Heliroc: needs a new rubber band for the blades.
  • Sudden Mach: first, I need to reglue the nose cone into the upper body tube. Then, I need to figure out how to mount the timer for easier and more sucessful operation.
  • Deltie Thunder: the pop pod needs a lot of work. There's a massive crimp in the body tube; I'm not sure if I'll replace the tube entirely or just couple in a fresh section. I also need to fix the glider hook, probably with plywood - it wasn't designed to take an F motor - and to fix the economy-sized dent in the nose cone.
  • Multi-Goon: I need to change the 13mm and 24mm engine mounts to prevent them from being burned by ejection charges.
  • Svetlana will take the most work. Mainly, I need to figure out a new baffle system. I need to clean off the back end, repair some dings, and put a clear coat of protective enamel on. Plus, if I'm lucky, mandachan will draw Svetlana-the-character on it.

Sudden Mach flight data

I got the flight data on our drag race from Crazy Jim. His altimeter was beeping out 3382 feet.

My simulation indicated 3380 feet.

That is incredible. That's not just an accurate simulation, that's a perfect flight, an absolutely vertical trajectory, and pure dumb luck.

I gotta get me one of those tiny altimeters.

Thursday, July 1, 2010

For Science!

According to the paper today, Ozzy Osbourne's DNA is getting sequenced. For science.

You see, he was basically on a 40-year bender. He consumed quantities of drugs and alcohol that would kill most healthy humans. So, they're hoping to spot mutations in certain areas that would indicate a higher resistance to those substances. Ozzy even volunteered the 65 grand to get it done.

Ironically, now that he's cleaned up his act (though his stage shows are just as awesome, save the bat-eating), he even writes a health column for the British Sunday Times.

From CBS news

Rounding

Rounding a number to the nearest power of 10 is easy. Round up if the end is 50 or above, down if 49.9... or below. But what happens if you need to round to the nearest 5, or the nearest 45, or the nearest multiple of 2π?

Then use this simple formula, constructed during a sleepless night by me. It'll round any number x to the nearest multiple of n.

n int ((x/n) + 0.5)  (Where int(z) is the greatest integer less than z, also called the floor function; it's available on most graphing calculators and in most programming languages.)

It works for any n>0.

For complex numbers, apply separately to the real and imaginary components.