Oxamide, Del Grande, and Traveler
Welcome back to our sporadic web updates! Here's what's been going on recently:
Oxamide testing - Back in February we built a small 3" diameter, two-grain motor case to characterize a new propellant formulation. We cast 6 small composite grains 72/10 AP and Al content, with an added 3% oxamide as a flame coolant with the hopes that we could see an appreciable lengthening in burn time as a result.
The motor case was all aluminum and we conducted three separate tests in one day. The difference between each firing was the throat diameter of the nozzle - it was constructed of an aluminum carrier with a removable graphite insert that had a different throat diameter for each burn, in order to hit 600, 800, and 1000 psi, respectively. It had hardly any diverging section, making it simply a sonic throat - we only needed chamber pressure and burn time in order to figure out the burn rate coefficients that we needed for modeling.
It was a first in the fact that Rocket Lab fired one motor three times in one day. This time we didn't have to worry about a thrust stand - we just dug a hole and threw the motor in the ground (reminiscent of some old static tests conducted by lab...).
We first put in nozzles that were supposed to give us 400 and 600 psi chamber pressures, but noticed that we were actually hitting startup pressures of 150% nominal pressure. We opted out of the 800 psi nozzle and went for a lower 300 psi nozzle we made as a back up just in case this problem happened.
With the biggest throat diameter, there was noticable chuffing in the motor - solid propellant combustion instability - caused by an incredibly low L* value (volume of chamber divided by the area of the throat) that caused the motor to resonate, similar to blowing over an open glass bottle and hearing a sound. We just had this nozzle lying around just in case we were worried about chamber pressure, and really did no Kn calcs with it - we just basically found a drill bit lying around and did the "eh...looks about right" calculation. But hey, we learned a lot. I put up just the one interesting video (chuffing) on youtube:
(for some reason I can't get the video to actually display on Blogger so you will have to click the link)
Del Grande - We rebuilt Del Grande to fly it again this semester. We used a new kevlar nosecone (the mold/plug has been in the works for years now) with which we wanted to test a new nosecone mounted avionics system and CO2 recovery system. Everything else in the rocket was pretty much the same as before.
The upper airframe was repaired after the last flight which left a lengthwise tear in the airframe due to parachute deployment, and a new motor case and nozzle were manufactured. This rocket is an 8" diameter rocket with a 6" P6110 motor in an aluminum motor case.
We wanted to try a new GPS avionics system that would track the rocket and backup the data given from our ARTS board (from Ozark Aerospace). Unfortunately due to time constraints and a few hiccups with the live telemetry coming from the GPS system, and the fact that the on-site generator we were using to power our tracking computers failed just before launch, we were unable to get an active lock on the GPS system.
The launch was beautiful, even considering the weather conditions - it was incredibly windy. It was unnerving to watch the rocket sway back and forth on our launch rail as the bottom of the rocket was stacked precariously on a pile of bricks we found lying around. But the takeoff was amazing, as it was last time with this monstrous rocket. (We say monstrous because its so far the largest rocket we have fired, since this one was slightly longer than Del Grande 1). Video here:
Sims/past flight data say ~20k ft at ~mach 1.1 from a P6110 motor. It wasn't light. After the launch, Ian Whittinghill flew all over the site and was unable to find any trace of the motor:
Mojave Test Site
And the next weekend, a few members of RPL came out with a telescope and looked all over the Mojave desert, running from hill to hill, and getting sunburned the entire time. This is a time to learn and rethink some of our recovery methods, after the second failure in a row. This is something that we are turning our full attention toward, because our next rocket at Balls is REALLY going to need it, since our next project is...finally....Traveler.
ALSO - keep following our Picasa album... I am uploading more and more stuff. There's pictures from this last launch and I am starting to upload senior design projects by lab members. We have done everything from hybrid propulsion to electric to liquid flow tests. We don't call it Rocket "Propulsion" Laboratory for nothing.
posted by William Murray at
11:59 AM
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