Re: rocket motors

On 3 Jan, 23:42, richardcas...@xxxxxxxxxxxxx (Richard Casady) wrote:
On Sat, 03 Jan 2009 20:28:10 -0600, "Lloyd E. Sponenburgh"





<lloydspinsidemindspring.com> wrote:
richardcas...@xxxxxxxxxxxxx (Richard Casady) fired this volley in
news:499204c2.660078562@xxxxxxxxxxxxxxxxxxxxxxx:

On Mon, 29 Dec 2008 09:02:53 -0800 (PST), TONY S <kclo42112
@gmail.com>
wrote:

anyone  here use aluminum with Bp for rockets? I know that its used
for extra thrust but how much and is it worth it?

Aluminum, used with ammonium perchlorate, and a binder, is the fuel
for the Shuttle solid boosters. Not extra thrust, in that case, but,
give or take the binder, all of it.

"give or take the binder" means "give or take all of the fuel" except
the small percentage of aluminum added to raise the combustion
temperature.

Having spent some time discussing these fuels with John Rahkonen (who
originally formulated the Shuttle SRB fuels), I became aware that the
aluminum was an adjunct - not the primary fuel - to raise the
combustion temperature (and thus, the chamber pressure).

I seem to have been misinformed. Organic fuels would have a lower
average atomic weight wouldn't they.

Casady- Hide quoted text -

- Show quoted text -

The propellant mixture in each SRB motor consists of an ammonium
perchlorate (oxidizer, 69.6 percent by weight), aluminum (fuel, 16
percent), iron oxide (a catalyst, 0.4 percent), a polymer (a binder
that holds the mixture together, 12.04 percent), and an epoxy curing
agent (1.96 percent). The propellant is an 11-point star- shaped
perforation in the forward motor segment and a double- truncated- cone
perforation in each of the aft segments and aft closure. This
configuration provides high thrust at ignition and then reduces the
thrust by approximately a third 50 seconds after lift-off to prevent
overstressing the vehicle during maximum dynamic pressure.
Source: http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/srb.html

From wiki (ugh):
The propellant mixture in each SRB motor consists of ammonium
perchlorate (oxidizer, 69.6% by weight), aluminum (fuel, 16%), iron
oxide (a catalyst, 0.4%), a polymer (such as PBAN or HTPB, a binder
that holds the mixture together, also acting as secondary fuel,
12.04%), and an epoxy curing agent (1.96%). This propellant is
commonly referred to as Ammonium Perchlorate Composite Propellant, or
simply APCP. This mixture develops a specific impulse of 242 seconds
at sea level or 268 seconds in a vacuum.

The main fuel, aluminum is used because it has a reasonable specific
energy density of about 31.0MJ/kg, but having a high volumetric energy
density, as well as being difficult to accidentally ignite.

The propellant is an 11-point star-shaped perforation in the forward
motor segment and a double-truncated-cone perforation in each of the
aft segments and aft closure. This configuration provides high thrust
at ignition and then reduces the thrust by approximately a third 50
seconds after lift-off to avoid overstressing the vehicle during
maximum dynamic pressure
Source: http://en.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_Booster#Propellant

.

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