[SS-Propellant] Re: Launch of the Propellant Development phase of SS2S

[william colburn]

The two phase motor offers a splendid example for
checking Chuck's flushing theory. The second phase
should thereby have greater Isp perhaps despite the
addition of the blast tube comprising the second motor
chamber.

With both theories providing such close approximations
to actual data, future testing will be very
interesting.

The use of the sucrose/sorbitol alloy as the binder is
a very interesting one as it may just solve the
peaking problem with little change in the process (as
Rich has pointed out)

BC

--- Rich Nakka <richnakka at rogers.com> wrote:

> Welcome to the SS2S Propellant Development Team
> (PDT) e-mail discussion 
> group...!  <>
> 
> Team members:
> <>* Richard Nakka
> * Randy Dormans
> * Matthew McFarland
> * Chris Richards
> * José Miraglia (please confirm whether or not  you
> received the earlier 
> test message)
> * Vlad Mateica
> * Antoon Vyverman (Antoon, have you signed up to the
> list? I am cc'ing 
> you for now)  <>
> ---
> What is on our agenda?  <>
> 
> First, the big news is that test firing of the ¼
> scale motor  (BEM) will 
> be taking place soon, tentatively at the beginning
> of December. With 
> sorbitol based propellant (KNSB) being used, it can
> be expected that the 
> motor thrust curve will experience the odd behaviour
> that has been seen 
> in the past with KNSB motor. That is, the
> "triangular" thrust curve, 
> rather than the predicted "flat" curve that BATES
> should provide.  <>
> 
> For those of you not familiar with this phenomenon
> (which I'll refer to 
> as "flushing" coined by,  C.Knight ), I recommend
> reading the test 
> report of the Kappa-SB motor:
> http://members.aol.com/kappadx/ksb002.html#Analysis
> 
> Note that the use of primer coating and  pyrogen
> ignition does not 
> eliminate this behaviour.
> 
> <>Also check out C.Knight's hypothesized explanation
> for this phenom:
> http://www.nakka-rocketry.net/knsbchar.html  <>
> 
> Tony Vyverman has written an excellent article that
> also hyhpothesises 
> certain causes such as partially-delayed igntion:
>
http://sugarshot.org/downloads/evaluation_of_kno3.pdf
> <>It is important 
> that we avoid this type of behaviour for the SS2S
> motor, for two 
> important reasons:
> 
> 1) We need full thrust off the pad to get the rocket
> stable quickly to 
> avoid any deviation from the desired flight path.
> 
> 2)  The low average chamber pressure resulting from
> a "triangular" 
> thrust significantly cuts into the delivered
> specific impulse, which we 
> cannot afford. The sims for the flight are based on
> an average 130 sec. Isp.
> 
>  <>Suggestions are needed on how we can modify the
> KNSB propellant, or 
> the motor design to achieve this goal.  <>
> 
> Miraglia has suggested the use of a sorbitol/sucrose
> (SB/SU) mixture. 
> This is an interesting option. Although this may not
> eliminate the 
> flushing problem (see Tony's report) it may
> nevertheless help, or such a 
> formulation could provide other advantages. For
> example, sucrose has a 
> greater density, which means more propellant mass
> for a given motor  
> volume.  A 1 or 2 % performance gain might be
> realized, based on my 
> calcs.  <>
> 
> My own feeling of late is that flushing might be a
> result of the grain 
> segments being too close together, causing a sort of
> self-extinquishing. 
> Perhaps we can do  static testing to see if greater
> spacing helps. Also 
> consider instead of flat faces on segments, have end
> surfaces sloped 
> (shallow cone). A really interesting suggestion put
> forth by Tony is the 
> use of KNSU on segment ends. This would also boost
> thrust off the pad, 
> due to KNSU's greater burn rate. Instead of KNSU,
> perhaps KNSB doped 
> with  Iron oxide ? Thoughts?  <>
> 
> Additives such as carbon or iron oxide to act as
> opacifier  can also be 
> considered/tested.  <>
> 
> Erosive burning behaviour of  KNSB should be
> investigated. Perhaps 
> someone can come up with a test proposal.
> 
> Consider small modifications to the formulation to
> improve Isp (e.g. 
> 66/34 instead of 65/35)?  GUIPEP runs can be done to
> get an idea if this 
> is worthwhile. Runs can also be done on KN/SB/SU
> formulations.
> 
> <>If the propellant formulation is changed in any
> way, testing will need 
> to be performed to characterize burnrate & c-star,
> as well as other 
> qualities such as hygroscopicity and safety with
> regard to overheating 
> during casting.  <>
> 
> Much of the testing can be done using small, scaled
> down motors.  Vlad 
> has volunteered to do some static testing. Randy,
> could you do some 
> testing as well? I can do propellant
> characterization tests, such as 
> strand burner. I may also be able to do limited
> static testing, say, 
> with the A-100M motor.
> 
> <>The next major SS2S motor test will be the
> "short-stack" motor. Before 
> this, we need to come up with a means of casting
> large propellant 
> grains. The short-stack is slated to have 2
> segments, each with a mass 
> of about 34 kg (75 lbs), which is identical to the
> full-size motor. 
> Also, curing the grains under pressure to ensure
> positive bonding to the 
> casting tube will need to be investigated and
> testing done. <>So there 
> is no shortage of work for the PDT, and no shortage
> of ideas that need 
> to be put forth.
> 
> And  please respond to the ss-propellant list, not
> to me personally, to 
> keep this a group project.
> 
> Richard Nakka
> 
>  
> 
> 
>