From 9b2e94aa9e8a55c8b17f31237db1d41a09e685c7 Mon Sep 17 00:00:00 2001 From: Bdale Garbee Date: Sat, 30 May 2015 21:55:47 -0600 Subject: [PATCH] starting research motor log! --- rockets/research/index.mdwn | 5 ++++ rockets/research/test1.mdwn | 58 +++++++++++++++++++++++++++++++++++++ 2 files changed, 63 insertions(+) create mode 100755 rockets/research/index.mdwn create mode 100755 rockets/research/test1.mdwn diff --git a/rockets/research/index.mdwn b/rockets/research/index.mdwn new file mode 100755 index 0000000..89b95f1 --- /dev/null +++ b/rockets/research/index.mdwn @@ -0,0 +1,5 @@ +# Propellant Research # + +## Test Log ## + +* [Test 1](test1) - 38mm 3-grain KNSO diff --git a/rockets/research/test1.mdwn b/rockets/research/test1.mdwn new file mode 100755 index 0000000..033b137 --- /dev/null +++ b/rockets/research/test1.mdwn @@ -0,0 +1,58 @@ +# Test 1 # + +Robert and I decided to start out with a Sorbitol mix. Following +[Scott Jolley's](http://ajolleyplace.com/scott.html) lead, Bdale procured +a sample of Polystep-B1 surfactant to make the propellant pourable. + +A quick burn simulation suggested 3 grains in an Aerotech 38/360 case with +0.250 nozzle throat would be something like an H125 with Kn in the low +300's, fairly even burn rate, using around 177g of propellant. It looks like +this is in a burn rate plateau, as simulating with the stock nozzle size of +0.180 inches yielded nearly identical results, just with higher chamber +pressures. + +Aerotech 38mm grains are 1.875 inches long, and our casting tube measured +1.260 inches inside diameter. We used a +[Tru-Core](http://www.rocketsaway.com/html/casting_sets.html) +casting set with 0.5 inch diameter mandrel. The plan was to cast one long +grain and then cut it into 3 grain-length pieces, so we started with 6 inches +of casting tube weighing 4.75 grams hoping to get at least 5.625 inches of +good grain after saw / knife kerfs. + +## Formula ## + +* 65% Potassium Nitrate (130g) +* 35% Sorbitol (70g) +* 1% Red Iron Oxide, added post-melt (2g) +* 1 drop per 100g Polystep-B1 (2 drops) + +## Process ## + +We measured out the potassium nitrate and sorbitol into a sealable plastic +container and shook vigorously to break up the clumps in the sorbitol and +get a good physical mix. + +The mix was dumped into a Presto Multi-Cooker and heated with the dial set +to something like 225 degrees F. Once it started to melt, we stirred almost +constantly with a silicone spatula. + +Once the sorbitol was all melted, we added the red iron oxide and stirred +until it was all blended in. Then we added 2 drops of surfactant and +continued to stir. The surfactant clearly reduced viscosity as shown by +lifting the spatula and watching how the material dripped off. + +We started to pour the propellant into the casting tube on the stand, but +fairly quickly the mixture got thick as it cooled. So we put it back on the +heat, with the control turned up to something like 275. Stirring constantly, +we noticed it start to smoke and immediately pulled the power and started +to pour again. This time we got the casting tube filled pretty easily. + +We set up some folded card stock in a piece of aluminum angle and poured the +remaining propellant in to form a test strand for open air burning. + +Clean-up was done using water and paper towels, including boiling water in the +multi-cooer to help soften the residual propellant. Pretty easy to clean up +actually. + +About 4 hours later, the card stock was pulled off the test strand, which +proved to still be a bit on the pliable and "tacky" surface side. -- 2.30.2