From sedsnm Tue May 26 16: 06: 09 1998




Скачать 206.83 Kb.
НазваниеFrom sedsnm Tue May 26 16: 06: 09 1998
страница3/3
Дата07.10.2012
Размер206.83 Kb.
ТипДокументы
1   2   3


To: Dave/Kristin Hall

CC: RocketGeeks

Subject: Re: Boosted motor.


Dave/Kristin Hall wrote:


> I was thinking...

>

> * The core (of a core burner) is wasted volume

> * A good, quick ignition of the grain is often beyond "normal"

> igniters

> * A good swift kick in the ass is always a good thing (for a rocket)

>

> So, has anybody ever filled the core of a normal AP motor with

> micrograin?

> Seems like it would act as one hell of an ignition aid (and burn so

> fast

> as to not effect grain dynamic shape much at all), give the motor a

> nice

> little kick, and hey, more propellant is always a good thing!

>

> --

> David Hall

> Propulsion Performance Office (Code 4732H0D)

> Naval Air Warfare Center - Weapons Division

> China Lake, CA 93555


Micrograin motors burns very quickly, showing peak pressures around 120

bar. This is an inherent limit of the combustion process, as the heat of

evaporation equals the heat of combustion at somevhere around 120 bar -

and this means, that micrograin rockets are rather easy to design: If

the motor casing is able to withstand 120bar + safety margin, it will

work.


However - addition of some organic compound will take away the inherent

pressure limit. Placing a micrograin charge within a coreburner will

cause the burnrate, and thus pressure, to be extremely high right after

ignition. This might work for a 200+ bar motor, if carefully designed.

For motors operating at more normal pressures - forget it.


Micrograin in small portions works nicely for ignition BTW.


Hans Olaf Toft

http://users.cybercity.dk/~dko7904/linklib.htm


Date: 28 Sep 1998 13:56:35 -0500 (added by MTA mail.murraystate.edu)

To: arocket@nmt.edu

From: Terry McCreary

Subject: Re: Boosted motor.


At 01:52 PM 9/28/98 -0400, you wrote:

>How does one make a consistant foamy propellant ?

>Will it work with my AP , Al, HTPB straight mix??

>Tom


I don't know about "consistent", but foamy propellant is easy. Just use

HTPB contaminated with a little water, and add excess curing agent. The

curing agent reacts with water, you get CO2. And the product of this

reaction catalyzes the cure! So it can harden up on you within minutes,

right in the middle of packing the stuff. :-(


Seriously, consistency would be a problem. PAPI and IPDI are supposed to be

more reactive with water than other curatives.


P'rfesser


To: "Dave/Kristin Hall" , "ARoc"

From: "Troy Prideaux"

Subject: Re: Burn Testing

Date: Tue, 29 Sep 98 10:50:34 +1100 (WDT)


My interpretation of chuffing is a phenomenon experienced with SMALL motors

containing a propellant consisting of a pressure sensitive oxidiser(s) such

as AP which is ignited but firing "UNDER" the full working pressure of that

propellant. This will result in a "Chuff" a cough type effect by where the

motor appears to almost blow it self out and in a few cases it does

terminating all combustion with a very high percentage of the propellant

still not burned. If the motor continues to operate it may come up to

enough pressure to operate normally or continue to chuff like a slow pulse

which will be repeated until the motor comes up to pressure and begins to

operate normally or extinguishes its self. This normally happens in the

first part of a motors operation and is more apparent in progressive grain

structures. Normally it can avoided but tightening the throat of the nozzle

to increase pressure. Also I have found this effect to be more apparent in

low solids formulations (slow ones too) and propellants containing little

or no metals. I've found motors 54mm or larger don't seem to be affected by

this "chuffing" problem.


Date: Mon, 28 Sep 1998 20:59:05 -0400

From: Tom Binford

To: Troy Prideaux

CC: Arocket@nmt.edu

Subject: Re: Delay comp's


Troy Prideaux wrote:

>

> Does anyone have any good formulations for pyro delay compositions. Prefer

> smoky ones but beggars....... Also would prefer easily obtainable chemicals

> if possible?

>

> Thanks,

>

> Troy.


I use a HTPB - Zinc based composite:

200u AP 40

Zinc dust 40

HTPB R45M 11

DOA 6.5

Tepanol .5

Iso 143 2


Mix all ingredients except AP until uniform. Add AP and mix until

uniform. Pour into tubes and allow to cure.

Burn rate is approx 30 sec per inch at atmospheric pressure.

Exhaust is grey/white smoke (black if confined).

Tom


Date: 28 Sep 1998 20:39:12 -0500 (added by MTA mail.murraystate.edu)

To: arocket@nmt.edu

From: Terry McCreary

Subject: Chuffing (was Re: Burn Testing)


>BTW, just what in the heck is "chuffing?" I see it used all over RMR and

>arocket, but I've never seen it defined and none of my texts mention it

>(at least by that name).


AP and KP propellants burn well only under pressure. If the area ratio is

too small to maintain combustion, some of the propellant can ignite and burn

briefly, then it may go out. If enough heat has been absorbed by the

propellant during the brief burning, it can re-ignite when the exhaust gases

have moved away from the surface. The phenomenon can repeat itself until

the propellant either goes out completely or the entire surface ignites and

burns normally.


BP motors don't show this problem because BP burns well at almost any

pressure, except subatmospheric.


P'rfesser


Date: Wed, 30 Sep 1998 12:30:40 -0600

From: Michael Bernard

To: Dave/Kristin Hall

CC: Terry McCreary ,

RocketGeeks

Subject: Re: Silicones (was Re: Chuffing (was Re: Burn Testing))


One thing to consider when selecting a silicone to use with AP is that many of

the two part silicones evolve acetic acid as they cure. I seem to remember that

acids can sensitize AP formulations. The moisture cured silicones evolve ammonia as

they cure and don't present any problems. I first read about Silicone II/PP (or AP)

propellants in a PGI (Pyrotechnic Guild International) paper that was on Tom

Perrigrins (sp?) pyro web site. The guy that wrote it stressed that a lot more work

on incompatabilites needed to be done and that it was a very preliminary report. Any

idea what the heat cured silicones have as byproducts?


mike Bernard


Dave/Kristin Hall wrote:


> >>Have you considered using any of the two part, heat cured silicones? Granted,

> >>the work I've done with them was not propellant work, but you get *days* of

> >>pot life (even with the catalyst added). But throw it in a (roughly) 150 F

> >>oven for a few hours and you've a complete cure.

>

> > Dave, can you give us some specifics on these silicones? Brand, part

> > number, approximate cost, availability?

>

> I don't have any *specifics* anymore, but....

>

> Dow Corning makes a *bunch* of them suitable for just about any application

> you can think of. Personally, I was trying to find an adhesive that would

> glue ceramic tiles to either aluminum or carbon/epoxy composite that could

> withstand pretty severe temperature cycling. Even with that in mind, I

> *still* had about a dozen to choose from.

>

> I don't remember the part number, etc. for what I ended up with, but it was

> some very tough stuff. When we glued the tiles to some sheets of carbon

> and aluminum for testing, we found that we could not tear the tiles off

> without the use of a chisel (to get under the corner of the tile). It had

> an advertised pot life of 3-4 hours (IIRC) but we found in practice the pot

> life to be measured in days, maybe even weeks (read: We threw it away before

> it was unusable).

>

> The stuff we used was very thick. About the consistency of rubber cement

> (duh!). I understand they also sell a thixotropic version though.

>

> Cost? I don't recall, but if it was particularly expensive, I would (recall).

>

> Availability? I seem to recall it taking about 3 weeks to get.

>

> Oh, and it comes in 10 lb (2 literish) buckets.

>

> --

> David Hall

> Propulsion Performance Office (Code 4732H0D)

> Naval Air Warfare Center - Weapons Division

> China Lake, CA 93555


Date: 30 Sep 1998 14:27:08 -0500 (added by MTA mail.murraystate.edu)

To: arocket@nmt.edu

From: Terry McCreary

Subject: Re: Silicones (was Re: Chuffing (was Re: Burn Testing))


At 12:30 PM 9/30/98 -0600, you wrote:

> One thing to consider when selecting a silicone to use with AP is that

many of

>the two part silicones evolve acetic acid as they cure. I seem to remember that

>acids can sensitize AP formulations. The moisture cured silicones evolve

ammonia as

>they cure and don't present any problems. I first read about Silicone II/PP

(or AP)

>propellants in a PGI (Pyrotechnic Guild International) paper that was on Tom

>Perrigrins (sp?) pyro web site. The guy that wrote it stressed that a lot

more work

>on incompatabilites needed to be done and that it was a very preliminary

report. Any

>idea what the heat cured silicones have as byproducts?


My understanding is that the two-part silicones emit nothing during cure.

Like epoxy, they undergo an addition reaction. One-part silicone caulking

is moisture-cure regardless of the type. The older type emits acetic acid,

and supposedly should not be used in pyrotechnic compositions that might be

acid-sensitive. GE II emits ammonia.


I've never used a two-part silicone but know that they're used to make molds

for plastics. A gas given off during cure wouldn't have time to bubble out

and would ruin the mold.


P'rfesser


Date: 29 Sep 1998 06:15:45 -0500 (added by MTA mail.murraystate.edu)

To: arocket@nmt.edu, tbinford@frontiernet.net

From: Terry McCreary

Subject: Re: Changing burn profile


>Thin styrofoam disks, wax, maybe even something like dried bread. I

>would think that with a foamy spacer, the pressure rise would push it to

>the outside of the groove, accomplishing your goal. (Unless it splits

>along the thickness, with the pieces acting as an inhibitor. I would

>make several motors, some straight core, some with thin styrofoam and

>some with wax paper. Put them on a test stand, burn em, and see what

>happens.

>Good luck - Tom


Combine two ideas. Use fast-burning foamy propellant disks as your spacers.

They'd burn away very quickly, pressurise the chamber and start the motor

quickly. If you're into making your own igniters you could use a multiple

igniter setup with a small "head" at each spacer, to insure they ignite first.


P'rfesser
1   2   3

Похожие:

From sedsnm Tue May 26 16: 06: 09 1998 iconFrom Tue Apr 15 11: 25: 12 1997

From sedsnm Tue May 26 16: 06: 09 1998 iconTue and Thurs. 4: 00~5: 30PM

From sedsnm Tue May 26 16: 06: 09 1998 iconTue Oct 11 16: 48: 55 cst 2005

From sedsnm Tue May 26 16: 06: 09 1998 iconF42B1/02 (12) описание изобретения к патенту
Ссылки: ru 2103643 C1, 27. 01. 1998. ru 2250359 С2, 20. 04. 2005. ru 2110753 С1, 27. 01. 1998. Us 4860655 A, 29. 08. 1998
From sedsnm Tue May 26 16: 06: 09 1998 iconПинк Флойд
Издательство Сергея Козлова, 1998 г. © Nickolas Schaffner, 1991 г. © Гливенко Д. В., перевод. 1998 г. © Гисич И. С., оформление....
From sedsnm Tue May 26 16: 06: 09 1998 iconOrglist Digest Tue, 15 Jan 2002 09: 47: 26 -0800 V01 #110 Today's topics: 'Aminomethylation of polystyrene'

From sedsnm Tue May 26 16: 06: 09 1998 iconПубликации сотрудников кафедры за период с 1998 по 2005 гг
А. И., «Агрегация тромбоцитов при недостаточности кровообращения у больных с ишемической дилатационной кардиомиопатией» International...
From sedsnm Tue May 26 16: 06: 09 1998 iconPlease note: There will be more 1998 entries in the next update list 1998-1999

From sedsnm Tue May 26 16: 06: 09 1998 iconOfficial Journal L 174, 12/03/1998 p. 0001-0026
Директива 98/13/ес европейского парламента и совета евросоюза от 12 февраля 1998 г
From sedsnm Tue May 26 16: 06: 09 1998 iconTue – august 20 wed – august 21 thu – august 22

Разместите кнопку на своём сайте:
Библиотека


База данных защищена авторским правом ©lib.znate.ru 2014
обратиться к администрации
Библиотека
Главная страница