Forgot to include the link to the 4-grain DD-Slot motor firing...! Here it is: https://www.youtube.com/watch?v=vXaRzSZEbOA Richard On Sat, Mar 15, 2014 at 4:40 PM, Richard Nakka <richard.rocketry@xxxxxxxxx> wrote: > Highlights of recent developments on the DoubleSShot project > --------------------------------------------------------------------------------------- > - On Saturday, March 1st, Vicente Alvero test fired the VIC-2B > experimental rocket motor. This was the second test firing of the > VIC-2 motor, and differed from the first in two ways: > 1. the composite nozzle cone attachment was modified to make it more secure > 2. the grain configuration was changed to that originally intended for > this motor (two unrestricted grain segments) > The primary purpose of this test firing was to ascertain how well a > carbon-fibre nozzle cone would hold out. Approximately half way > through the 2.5 second burn, the cone burnt through just aft of the > nozzle throat, and separated from the motor. This test clearly > demonstrated the intense heating that occurs in this region and that > normal composite material is not suitable. The latter half of the cone > survived the firing largely intact and will be used for the next test. > A steel "nozzle extension" will be fabricated, which will connect the > nozzle throat to a truncated cone. Another modification to the motor > will be a phenolic insert in the convergent part of the nozzle. This > will investigate how well phenolic stands up to the intense heating of > the flow as it enters the throat region. > Close-up video-captures of motor firing: > http://sugarshot.org/downloads/vic-2b_full_thrust2.jpg > http://sugarshot.org/downloads/vic-2b_rupture.jpg > http://sugarshot.org/downloads/vic-2b_post_sep.jpg > http://sugarshot.org/downloads/vic-2b_thrusting.jpg > http://sugarshot.org/downloads/vic-2b_burnout.jpg > Videos of test firing: > http://youtu.be/4cagisNbk7M > http://youtu.be/PdCHL2ZwsHk > Post-firing shots of nozzle cone: > http://sugarshot.org/downloads/img_1668a.jpg > http://sugarshot.org/downloads/vic-2b_cone_interior.jpg > Sketch showing proposed VIC-2C modifications: > http://sugarshot.org/downloads/vic-2_nozzle_mod.pdf > (videos/photo courtesy Vicente Alvero) > > -On Friday evening, March 7th, the 4-grain DD-slot 89mm motor was test > fired. Because the rain forced a scrub of the planned March 2nd test > at the FAR site, Rick Maschek and NASA USLI Citrus College student > Aaron Bunch, performed the static firing at the Jean Dry Lake in > Nevada. As this was a straightforward static test with solely chamber > pressure being measured, all that was needed was a 10" hole dug into > the ground of the lake bed. Ignition was via an e-match and slice of > 38 mm APCP propellant and two strands of AP propellant draped over the > fiberglass inhibited top surface of the top Double-D grain. The motor > firing appeared nominal and good pressure readings were obtained. Rick > reported > "Because the sun had set, a flame was recorded on the high speed > digital video cam that shows up to four mach diamonds. Thermal sensor > labels were applied to the nozzle, mid and forward areas of the motor. > The only record was on the red labels near the aft end." > "Everything is reusable...even the lining is in good shape". A sheet > of 3/32" (2.4mm) EPDM (rubber) thermal liner was used for the motor > and contributed to the uncharacteristic dark grey exhaust smoke. Must > be why Scott uses the EPDM, it works great. The thickness looks the > same at the bulkhead and gradually gets thinner as you go down to the > nozzle though there was complete coverage and you could still see the > cuts I made on all four sides. Just 'guessing', I'd say half the > thickness burned away at the nozzle end. That might mean a thinner > piece could be used but let's hold off on that till we do the six > grain test...higher pressure and more erosion." > > "The only area of 'concern' was on the two sides near the top where I > had the APCP propellant for the igniter. I ran strands of it from the > top APCP disk that the e-match lights and the strands may have fallen > down and against the rubber when the motor was inverted. We will know > better when I do the six-grain test at FAR since it will be vertically > mounted on an I-beam. I will also try to secure the AP ribbon to the > propellant sides for the next test. The Red RTV (protecting the > bulkhead) was also almost burned completely away and that is not > normal so I think too much APCP was at the bulkhead end." > Aaron Bunch preparing to dig hole in dry lake bed: > http://sugarshot.org/downloads/cimg3638a.jpg > Aaron holding the rocket motor prior to the static firing: > http://sugarshot.org/downloads/cimg3642a.jpg > Rick with the motor in place: > http://sugarshot.org/downloads/dscn0065a.jpg > Motor thrusting: > http://sugarshot.org/downloads/thrusting-1.jpg > http://sugarshot.org/downloads/thrusting-2.jpg > Close-up of ignition, burning and ending: > http://sugarshot.org/downloads/ignition.jpg > http://sugarshot.org/downloads/4_diamonds.jpg > http://sugarshot.org/downloads/ending.jpg > Post-firing pics of motor disassembled: > http://sugarshot.org/downloads/dscn0212a.jpg > http://sugarshot.org/downloads/dscn0215a.jpg > http://sugarshot.org/downloads/dscn0216a.jpg > http://sugarshot.org/downloads/dscn022a.jpg > Views of thermal liner, post-firing: > http://sugarshot.org/downloads/dscn0366_bulkhead_edge.jpg > http://sugarshot.org/downloads/dscn0367_nozzle_edge.jpg > (photos and video courtesy Rick Maschek) > > -The next planned motor firing will be the 6-grain DD-Slot motor which > is planned to occur on April 5th at the FAR test site. > > -Markus Bindhammer reported that the recent balloon flight of the > robot astronaut "Cosma" was a partial success. Markus wrote: "The data > are not very useful as the data were only logged while waiting on the > ground waiting for lift-off for several hours. An internal time > prevent that data are only logged for 3.5 hours. I will build an > improved version of Cosma, more balloon flights are planned this year, > but not currently scheduled." > > -Grant Saviers has been added to "Donors of Goods & Services" for his > recent donation of two precision pressure transducers, which were sent > to Chris King. Thanks again for your generosity, Grant! > http://sugarshot.org/sponsors.html#Donorservices > > -An Avionics telecon was held Sunday March 2nd, and was attended by > Chris King, Hans Olaf Toft, Mattias Lampe, and Richard Nakka. Mattias > reported progress on the design of a de-spin controller. Mattias > procured various parts for testing, such as various types of motors > (in-runner, out-runner and brushed motors). Chris brought up a good > point about the possible concern of motor bearing lubricant > out-gassing in a vacuum. This will be investigated. The next telecon > is scheduled for March 16th . > > -SS2S welcomes (and thanks) Daniel Larsen as our newest Bronze Donor. > http://sugarshot.org/sponsors.html#Donors > > -Tickets sales are going well for the SS2S Tool Raffle, but we still > have a ways to go until we reach our goal. Those recent rocket motor > test firings led by Rick Maschek and Vicente Alvero were really > impressive. But remember, rocket motor testing is expensive, and > fund-raisers such as this are an important strategy to pays the costs. > http://sugarshot.org/tool-raffle/index.html > or if you prefer a straightforward donation: > http://sugarshot.org/contrib.html > --------------------------- > -Sugar Shot to Space is on facebook. Check us out. > http://tinyurl.com/2exr92k