Post BALLS XX Report

Silent times have fallen upon this blog recently, but I am about to fill you in on our progress with a very long status update.

Ever since we started the Traveler project back in April, we have been working on it diligently. We planned on scaling up our 4" Silver Spur 3 rocket that we flew last year at Balls to an 8" minimum diameter carbon motor case rocket to fly by BALLS this year in Black Rock Desert, NV. And it has been quite a journey - designing and fabricating the hardware necessary was no simple task.

In order to be cleared to fly a rocket of this size (an R 16,000), we had to get a Class 3 amateur rocket waiver from the FAA, which required a decent amount of paperwork and a large amount of diligence - we have never had to get a waiver of this kind before, nor conduct the kind of simulations necessary to get it. To start off the process, most of the key design work was finished before the start of the summer so that we could begin work with Air Force Research Lab at Edwards AFB on POST II 6DOF simulations of the rocket. In the simulations, we conducted several 1,000 run Monte Carlo simulations where the rocket would land in every imaginable case - low drag, high drag, low thrust, failed recovery system - you name it - so that we could see what the landing pattern looked like. This process is required for a Class 3 waiver, and took well over 500 e-mails and several phone calls with our friends at Edwards to complete.

Traveler in a section of the launch tower on display at BALLS. The horse is not flight hardware.

Long story short, we ran out of time. We hit all of the TRIPOLI/FAA deadlines, but during the last week were denied the waiver because of an ATC airspace limitation with two days to spare before the launch. We tried modifying our dispersions but were not able to get it done in time to still receive a waiver. These things happen - it's why it normally takes 45 days to complete this process, and why we are not let down by the results. We are ready to blast through the paperwork one last time for a launch on our own in the near future. While it would have been nice to fly at BALLS under the event waiver, insurance, and land use permits, we will simply have to do this on our own when we decide to launch.

But before I move forward, I want to give a HUGE thanks to the people we worked with from RPL to Edwards/AFRL, TRIPOLI, FAA/AST and ATC. All of you provided tremendous help, with Edwards/AFRL helping us at every second of every working day with simulation data, to TRIPOLI providing an immense knowledge of how to build/tailoring the 6DOF simulations to get the kind of results the FAA needed in order for us to get our flight waiver, to FAA/AST/ATC to pushing our paperwork through all government channels as fast as humanly possible. We realize we were not able to get a waiver in time for BALLS XX, but we would not have even gotten remotely close to it if it wasn't for all of your help. As an organization, we have learned and matured immensely in these past few months, and it’s because of all of you who helped us with this vehicle. This rocket will fly, and it'll fly soon!

Instead of hanging our heads low and coming up to the event empty handed, we decided to (mostly) finish the rocket, launch tower, and avionics and bring them up to the event. It was a great time to complete a mock integration of all of the systems and test them out. While everything would have most likely worked had we actually flown, it is nice to stand back and be able to identify problems with some of our processes and refine them for the future. We were also happy to show off all the work we've done and actually stand around and watch other groups fly (which is something we never have enough time to do).

So, moving on to the actual rocket. Like mentioned before, we were planning on entering the Carmack Prize at Balls, which requires a flight to 100,000 ft with altitude confirmation and a safe recovery on the ground. Traveler is definitely capable of achieving this altitude with a 211 lb R 16,000 motor. Average thrust is 3,500 lbs for 13 seconds, which will take us into the Mach ~6 flight regime.

The rocket itself is pretty much made of entirely composite materials. The motor is based on Silver Spur 3's design that has been successfully static tested and flown - a minimum diameter carbon motor case that has been developed and constructed by USCRPL. This year we increased the diameter of the rocket to 8". The composite systems are extensive to say the least. We manufacture everything except we do not lay up our own phenolic parts (yet). We usually buy pre-cured phenolic, as in the fin leading edges, and machine it in lab.

Layup time! This was the nosecone - most likely 2 a.m. on a random weeknight

Composite systems are as follows:

Unidirectional prepreg carbon (motorcase, fins)

Bi-directional prepreg carbon (motorcase, tip-to-tip fin reinforcements)

Linen Phenolic (fin leading edges)

Canvas Phenolic (motorcase)

Silica Phenolic (nozzle) - AAE Aerospace (see below)

Fiberglass Phenolic (nozzle) - AAE Aerospace (see below)

S-Glass Fiberglass (nosecone)

Cork Sheet (nosecone)

End-Grain Balsa (fins, avionics cartridge retainment bulkheads)

Upper air frame layup with unidirectional prepreg carbon

Setting up for the hydrotest - case passed @ 1,000 psi for 120 seconds

Machining the leading edge of the fins after the layup

Fin attachment with fin alignment guide machined from MDF

5-Layer tip-to-tip prepreg layup over the fins for reinforcement

The nozzle phenolic is the one part of the vehicle that was largely constructed outside of lab. For the first time ever, we have moved from a steel/aluminum outer nozzle carrier with phenolic inserts to a fully phenolic nozzle. The outer part of the nozzle is overwrapped in glass phenolic, with the bulk of the ablative material being silica phenolic. AAE Aerospace in Huntington Beach, CA manufactured the nozzle for us on a cheap budget and really quick timetable, and we are extremely thankful that they managed to do this for us. Our experience with AAE was great and they were very friendly/helpful to us throughout the process. The rest of the nozzle assembly - graphite throat, aluminum bulkhead, etc. was made in-house.

Showing off the nozzle at BALLS

This time around we wanted to mitigate the chances of seeing erosive burning in our motor. Usually with motors of this Length/Diameter (L/D) ratio, erosive burning (where gases in the combustion chamber are accelerated down the length of the motor to a point where they drastically increase heat transfer/burning rate of the propellant near the aft end of the motor) becomes an issue. On the bottom two bates grains, the ID of the propellant grain was opened up to allow the core velocity to drop below a rule-of-thumb value to where it should no longer be an issue.

The nosecone is covered in cork that will serve as an ablative protection against the ~Mach 6 flow at max Q. The nosecone tip is titanium as was with Silver Spur 3 (and thankfully helped protect our avionics after impact).

Nosecone - 10 layers of S-glass with outer cork layer. Tip not attached

The primary recovery deployment is controlled by a single Featherweight Raven. The Raven can ignite four e-matches to trigger double CD3's and a backup black powder charge, which then separate the nosecone and deploy a streamer for recovery. The Raven logs accelerometer, barometric, and temperature data internally. Independent of the Raven are three other systems, each with GPS and live telemetry. The first is an Arduino micro-controller which we have programmed to simultaneously transmit and log to an SD card data read from several components. The components attached to the Arduino currently include a Garmin GPS, pressure transducer (for motor pressure), and accelerometer. The Arduino transmits its data at approx. 900 MHz (33cm amateur radio band). The other two standalone systems are both packages comprised of just a GPS unit and transmitter. One is from Byonics and the other is the BeeLine system from BigRedBee. Both of these systems transmit at the APRS frequency 144.39 MHz (2m amateur band). This not only gives our system triple redundant GPS, but also allows us to use the APRS network (aprs.org) as a backup receiver for the GPS data vital to finding the rocket.

The core of our avionics team (minus Dylan who couldn't make it)

The launch tower was a brand new project this semester as well. It's made of up 3 modules that bolt together on site and are individually small enough to fit in the bed of a pickup truck. It has 4 adjustable steel guides that run 20' in length that guide the rocket without the need for extra buttons on the outside of the rocket. This saves us ~30k ft on our altitude. If we can gain altitude on the rocket by simply building GSE, why not? Well, that 30k ft was some of the hardest fought for - it took a monumental amount of work to build this monster of a tower, but it was finished in about a month. It can also be easily reconfigured to fly any of our past vehicles (8" dia and smaller).

20' of pure awesome

We successfully deployed the launch tower at BALLS to test on-site integration. Everything went well, and we have identified a few areas that would benefit from a little bit of improvement next time around.

This is what Traveler sees

One thing I want to note - this year we have had the largest rocket lab membership ever. Our first meeting of the year had easily 60 people present, and many of them have stuck around for the late nights in lab this semester. It's great that the lab has now grown to such a large size and is still functioning - we continue to educate ourselves and each other in each stage of the project and the process has been greatly rewarding.

Keep reading the website! Traveler will be up in the air as soon as paperwork is completed. It's just a matter of time at this point. We will continue work on improvements to the vehicle in the meantime, and possibly start up another interim project. Stay tuned.

Flight On!