I161W.... maybe

A while ago I bought an I161W off of stephen boy, and I opend it up today so I could see that all the parts were there, and lo and behold, one of the propellant slugs did not have a baggie, and it was already sitting in the liner tube. it is a relitively old load, it has a black liner tube made of the same material as the newer SU consumer motors. the slug that is a little deformed, it has bumps on one side (the entire thing of propellant is sticking out 1/16" from its little paper thing), and the other side has a valley about 1/8" deep. is this OK? can I still use it? I certainly hope so. if I cannot, what do I do with it? thanks for the help.

Neil... If you come to the next CMASS rocket launch, I can take a look at that for you. They way he stores his loads, parts are bound to get mixed up. I have made several loads from loose motor parts... including I161's.

"Pre fire" reloads were usually shipped with one grain in the liner and the rest bagged. The funny ended grain is the end of the stick of propellant. Propellant is cast in long sticks and cut into grains. It will work just fine, I usually put that grain at the nozzle end of the motor as it's harder to light.

OK, thanks Rocketjunkie. by the way doug, I do not know what you mean by "the way he stores his loads." if you mean Stephen boy, when I got it it was in the origional packaging. By the way, do you have any idea what the liner is made of? it looks to me like it is the same stuff as the normal consumer SU, but I do not know what the normal SU motors are made of, so I am clueless. all I know about the SU cases is that they are wicked tough. I whacked a spent one apart with a hammer, just to see what it looked like this morning. a lot like a RMS motor inside. It took several wicked hard whacks with the pointy end of a hammer (nail removal) to break it open, so it is really tough. Also, how do they make propellant "post fire"? why don't they simply keep it as one big thing of propellant, instead of seperate grains? I am glad to know that it is ok, so I will proabably be flying it. by the way (by the way, how many times have I said "by the way", this post?), doug, I cannot bring it to CMASS, as I am flying it in 3 days. thanks for the offer, though.

Pre-fire = before the AT fire. Post-fire = after the AT fire. Gotta love dem Latin prefixes.

If the liner is black, it is probably a phenolic liner. This is the same stuff that they use in the 18-29mm motor cases, just in thicker walls. McMaster-Carr sells it. For larger cases, AT uses filament-wound fiberglass.

Regarding the "stick of propellant" issue -- if they kept it as one long cored piece of propellant, it would be unweildly to ship, not "Easy Access" (it woulda been >62.5 g), and the motor would have had a severly progressive thrust profile. When chopped up in that configuration, it is called a BATES grain -- BAllistic Test and Evaluation grain. They are great because as the core diameter increases (increases burning surface area, increases thrust), the ends of the grain, which are also burning, become smaller (decreases burning surface are, decreases thrust). Around a L/D ratio of about 1.5, the thrust profile becomes perfectly flat and neutral. If you measure one of your 38mm grains, I bet it'll be somewhere around 2" long -- the propellant OD is ~1.25". The only reason, then, that AT motors have regressive thrust profiles is because the phenolic nozzle erodes significantly during the burn, yeilding less chamber pressure and less thrust.

I'm just in a typing mood this afternoon -- probably to get out of homework

Everything you have said makes sense, but the AT customer service guy told me that the I161W should not have a black liner. I TOLD him it was old..... I just done't know how old.... oh well, what difference will it make? just the liner tube. by the way, I noticed you moved from Kalyfornia (I think that was you) to Caleefohnia. Is that another movie, or a joke on something/someone? It is so funny to look at all the signatures and avatars out there..... by teh way, my scale may be off, but the I161W propellant grain in question weighs 64 grams, so howzit easy acces???? Isent the limit 62.5? going a little off topic here, but why 62.5? is equivelant to something (3.3 OZ? forget where I got that, but it kinda makes sense. I am a metric know-nothing, sorry.), or is it just another one of those nit-pickety ATF limits? first they regulate AP as an explosive, then they give us a limit like that.... why not just 62, or 63 (or 10000000000000000 pounds, for that matter. that would be better.), or something. why the extra half an ounce? I guess 62.5 is better than 62, but it makes me wonder. whenever I ask my dad a question like that he says "as you grandfather would say when I asked a question like that is "just to make you ask why"". an awnser for everything, but not a very satisfying one. OK, I am getting tired. 'Night.

P.S., just to rub it in, I either have no homework or all my work is homework, depending on the way you look at it. I prefer NO homework. I am homeschooled, so I do all my work at home, so everything could be called the "H-O-M-E W-O-R-K". sorry for the profanity I was unlucky enough to have a lineup of horrible teachers one year, taking my view of school from "tollerant" to "hatred". I swear, two of the teachers made kids cry at least once a week, and one of the two gave lectures on how his town had a better soccer team than the school he taught at. on lecture on that subject lasted for 15:36, according to my watch. (any wonder why he was mad at kids all the time. we did not see any educational value in his lectures, so we just found ways to pass the time. such as leaving the class two weeks early to start homeschooling.). Rant mode off. I think. whenever I get talking about that teacher the ol rant mode flips from low to supercharged. sorry. just gotta vent. you would think I would be done venting, I have not seen him for 2 years.

LOL!

Not to disparage your homeschooling but, 62.5 grams is not even CLOSE to 3.3 ounces

Try 2.2 ounces.

One of the first thing you should learn is how to look up information.

LOL! I just had to "look up" how to spell disparage!

We are on the Internet after all.

"The Internet is like the world's greatest library...only all the books are thrown on the floor!"

sandman

I don't think the I161 used phenolic liners... only paper. Maybe when the I161 was under the ISP name... Then that motor will be so old that it will be a bear to igniter.

The reason why I say the way he stores his loads because he has a box full of open reloads with faded markings on it that show what the load is... then asking what load is in a bag, he says he is not sure? A great way to get things mixed up.

You are forgetting something Neil.. the weight of the propellant slug includes the weight of the paper tube used to cast the propellant in, and the amount of moisture the grain absorbed during its lifetime. The 62.5 gram limit applies only to the combustable propellant part of the slug. If you "bake" the grains in your car during the summer, they will loose some weight because the water evaperates.

Aerotech 38mm grains are infficient because they don't quite make the 1:1.5 ratio. The reason.. the 62.5 gram limit. If they make it efficient, they will not be Easy Access.

Daveyfire is right on the money about Aerotech nozzles erroding, especially Redline motors..

Meh, close enough