The Rocket Propulsion Laboratory
USCRPL with Traveler at Tommy Trojan.
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Traveler II
09/09/2014 by Allie Gehris

It has taken three months to write this post, but justly so. Our members have been rightfully catching up on the three months of sleep we each lost as we readied Traveler II for launch in mid-May.  With the chaos of a lab move, some rather tedious regulations, and composite material troubles, the semester started off slow.  What resulted though, was an extensive to-do list for those brave souls willing to make TII a reality in the final weeks of school.  The last month could not have been a more stark contrast thanks to the bureaucratic greenlight and an endless supply of willing hands.

To bring all readers up to speed, currently one of our main goals as a team is to be the first student group in the world to get a rocket into space.  Traveler I was our first space shot vehicle intended to claim us said title, but it failed to reach space in September 2013.  To launch a rocket of the scale that we build and at the altitudes we reach, there comes a number of necessary governmental regulations. Among these are the air space clearances that only the FAA and other organizations can sign off on.

For TII, the successor to TI, the FAA gave us two approved launch windows (read as “deadlines”) – one for the off days between classes and finals, and another two weeks later after graduation. Watching the days fly by, our first concern was producing a motorcase that could pass a hydro test. The hydrostatic pressure test is a qualification/proof test in which the case is filled and pressurized with water.  Doing so ensures – or disproves – that the case will handle the pressure of the rocket motor in flight; it is the standard industry test for ensuring a mission-worthy solid rocket motorcase.

Upon baking our first TII motorcase, we lost vacuum during the cure process, allowing the carbon fiber and epoxy to swim around in what became a very psychedelic, but super ineffective carbon case. The oven proved to be the downfall of the next case as well, melting and burning everything onto the case.

Traveler II Mk.1, aka Mr. Squiggles

Ryan, Jordan, Brandon, and Sarah peeling burnt breather off Traveler II Mk.2, which would eventually become an obscenely strong door stop
The third case’s layup brought with it a new wave of anxiety. A motorcase layup is a time-consuming and laborious process, one that requires many people to be in the lab for long stretches of time. With finals quickly approaching, it became clear that if this case did not work it would mean missing the first launch window and not having the people necessary to build a new one in time for the second window. Luckily, this case seemed to elude the bad luck that claimed the first two cases during the curing process. Without any glaring problems, it was prepped for hydro test.

The first bulkhead was inserted into the case far enough to put in the second bulkhead, but not all the way to the end of the case.  Seeing as pushing a resistant bulkhead down the entire length of a 7.5 foot motorcase is not exactly an easy-going process, we were relying on the pressure of the water to push it into place, as has been the process for other tests. With everything in place, the water began flowing. It takes a few minutes to get the case up to any substantial pressure, so the loud cracking noise that occurred within seconds was surprising to say the least. The motorcase failed at ~45 psi city water pressure, a far cry from the 1000 psi that is needed for a passable case. The bulkhead which was supposed to have been pushed to other end of the case by the water had instead cocked inside the case, damaging it beyond repair. 
It almost would’ve been funny if the failure didn’t have such upsetting consequences. The reason it had dislodged inside the case wasn’t entirely clear, but crashing even before the pressure test had begun wasn’t a dignified way for case number 3 to go. Running out of options, we brainstormed how to proceed. It wasn’t fair to ask people to sacrifice hours of study time in the hopes that a fourth layup would produce a workable motorcase. However, with the nosecone, motor, and most of the fins already made, it seemed wasteful not to at least try for the second launch window. We decided to run with an untested idea that until then had only been discussed as a future project: we were going to filament-wind the entire motorcase.

Filament winding has been used as a part of each carbon fiber motorcase for a few years, but only for specific layers (making up about 1/3 of the total case). Creating a code that would allow the filament winder and the mandrel to cooperate at precisely the right speeds would not only optimize the fiber angles to create a stronger motorcase, it would mean that the time and energy consuming manual layup process would become unnecessary. Of course, the entire code driving the filament winder had to be entirely rewritten, but thanks to some dedicated individuals, Jordan and Ian, along with plenty of caffeine, we had a working code.  
The brains of the code, Ian, Jordan, and Carter, overseeing the first filament-wound layer.

The finished Traveler II Mk.4: Our first filament-wound case!

Accomplishing a fully filament-wound case deserved more pomp and circumstance than we could afford in the strained timeline we were working with.  After some celebratory energy drinks, it was right back to work. The case came out of the oven looking wonderful, with the exception of the bidirectional layers, which are responsible for reinforcing the motor retention section. We figured they might have been overcooked because they were dry and slightly frayed, but nothing so harmful as to call off the hydro test.

The fourth and final hydro test began around 3 pm on May 13th, four days before we were scheduled to head to Black Rock. The bulkhead had already been pushed (with difficulty) to the end of the case to prevent what happened to Traveler II Mk 3, but the absence of a loud crack as the pressure began to increase still came as a relief. This sought-after silence continued through the increasing increments of pressure, all the way up to 1000 psi, where it remained steady for over 2 minutes. We finally had a working motorcase!

(Photo Credit: Susan Karlin)
The next four days were nothing but a race to the finish.  Now that we had a case, everything started coming together as the final preparations for our trip to Nevada were made. Seeing as though this was going to be our first trip to Black Rock without attending a rocketry event called BALLS (where Traveler I was flown) we, in a brilliant stroke of creativity, named our own event:  Not BALLS 2014 was a go!

Brandon, Ryan, and Allie bonding... oh, and attaching the fins to traveler

Congratulations, it’s a nozzle!

Jordan, Jeff, Kevin, and Ryan inspect the rocket after a beautiful tip-to-tip cure
(Photo Credit: Susan Karlin) 

Brandon drilling one of six GoPro holes in the upper airframe
(Photo Credit: Susan Karlin)

The nosecone, although having been made months prior, looking as sexy as ever
(Photo Credit: Susan Karlin)

Brad and Kevin high-fiving after the trailer and the rocket have been successfully packed
(Photo Credit: Susan Karlin) 

About a day behind schedule, but still with two full days left in the launch window, the caravan set off. With the exception of a well-deserved In-N-Out stop, there were no major holdups until about 6 AM when a tire melted. A quick stop at Home Depot and a bolt later, everything was back on track. Six hours after that, everyone had arrived in Black Rock and it was time to set everything up to launch that evening. As much as we did in the days leading up to Black Rock, there was still a lot to finish: integrating the motor, incorporating the recovery system, assembling and calibrating the launch tower, and doing last minute functional checks with the avionics. The first evening of preparations ran us slightly over our launch time, so we had to postpone the launch until the final day of our launch window.

RPL Fleet ready for action!
(Photo Credit: Susan Karlin)
Good morning sunshine
(Photo Credit: Susan Karlin)
Carter and Ian integrating the avionics sled into the nosecone
(Photo Credit: Susan Karlin)

Teamwork makes the dream work
(Photo Credit: Susan Karlin)

People struggling with the launch tower, but...
(Photo Credit: Susan Karlin)

Don't worry everyone, Kevin's got it!
(Photo Credit: Susan Karlin)

We won't be hitting any airplanes today, thanks to Brandon calling in the flight window
(Photo Credit: Susan Karlin)
Jake sticking it up the aft
(Photo Credit: Susan Karlin)
(Photo Credit: Susan Karlin)

In the morning of May 19th, the rocket was in the tower and ready to go. At 11:20 am, the countdown to space began.


Up, up, and away!
(Photo Credit: Susan Karlin)

Traveler left the launch pad, skewing slightly in the air before exploding promptly after ignition, at around 4,000 ft

(Photo Credit: Susan Karlin)

Once the pieces stopped burning and it was safe to collect them, the reason for the failure was immediately apparent.  The motorcase had shredded at the reinforced bidirectional section responsible for forward motor retention. While it had withstood the slow pressure of the hydro test, the faulty carbon wasn't strong enough to take that same force so abruptly.

Holy battery fire Batman!
(Photo Credit: Susan Karlin)
Thumbs up for the fins and nozzle perfectly intact after hitting the ground from a 4,000 foot free fall
(Photo Credit: Susan Karlin)

As sleep-deprived and exhausted as each of us were, this second failed space-shot attempt did not dampen any spirits. Once again, our Traveler launch became a learning experience for us to understand and build upon. Just 24 hours after our arrival, we were packed up and on the road again.

Failure is a part of rocketry, but as the RPL team nobly demonstrated, it should not be viewed negatively. Seeing what faulty carbon can do to a motorcase, we have decided to start imposing stricter quality control over the products we use, and are already back into full swing this semester.

A special shout out goes to Titan America and his film crew (whom you can see in some of the pictures above), who not only machined the amazing nozzle that survived the worst of the impact, but also braved the desert to come out and support us. We also want to thank Susan Karlin, an amazingly dedicated journalist responsible for many of the photos above. We were so lucky to find someone not only willing, but enthusiastic about accompanying us on multiple 14 hours drives to the middle of nowhere.

To our fans and every person who helped with the Traveler II build, from the first motorcase to the moment right before the launch: you're incredible. It takes a special kind of person to sacrifice their time and energy towards a build (especially during finals) and still have the strength to see failure as a learning opportunity. Our team is full of these people, which is what makes what we do possible and worthwhile. You'll be hearing about more exciting projects in lab's future, but for now, Flight On!

Semester Update
04/19/2014 by Jason Silverman
Things at RPL have been quieter than usual for the past semester, but they're about to get exciting! In this post we'll look at lab's activities since the cancelled launch of Traveler 2 last October and go over our plans for major launches later this year.

Both of the motor cases we attempted to make for Traveler 2 last semester had problems that prevented us from using them. The first one had its vacuum bag break while it was curing, leading to fiber warpage, while the second one got too hot near the middle during cure and also had a problem with its sealant layer. One thing we did differently with the sealant for that case was to wrap it with tow before laying down carbon sheets, in order to prevent the sealant from shifting later in the layup; however, that probably lowered the chance of creating a successful seal by squeezing the sealant unevenly. We decided to make future cases with a sheet layer over the sealant even if all the other layers would be filament-wound.

We used up our sealant material on the second Traveler 2 case, so we made a few test cases at the end of the fall semester with a different type of sealant that had been donated. We achieved a good seal in most of those test cases and burst them at a pressure well above our qualification level, using a new hydrotest setup in which the bulkheads were restrained by each other so no axial load had to be transmitted into the case.

In December we continued our Kiwi static fire series, firing a 72/10 grain (our normal propellant composition) and two oxamide grains at the Mojave Test Area to gather burn rate data. We're interested in testing propellant with oxamide added because it burns slower and would reduce the loads and aerodynamic heating on our vehicles. Following those tests, we decided we'd need one more round of firings before we could make a space shot design with oxamide propellant. We returned to the MTA in January to fire two final grains, one of which was in a case made with the new sealant material; both were successful and generated good data.

Kiwi at the December 2013 firing campaign. Its next outing will mark its celebratory 10th firing!

Jake supervises the cooking of a delicious breakfast!
The team at the MTA in January.
Kiwi has now been fired nine times, which we believe is unprecedented for a composite rocket motor case! The heat damage to the sealant is getting more and more noticeable, but its career may not be over yet.

Following the conclusion of our propellant additive testing, we finalized the design for our 6" space shot vehicle, Del Carbon Xtreme (DCX), which uses the benefits of oxamide propellant to reach space with a smaller motor than Traveler. It's planned to fly at BALLS in September, so work on it hasn't been the highest priority, but we did make a nosecone for it with our cork-based thermal protection material in January.

Megan, Brandon and Sarah epoxying a fiberglass backing layer to a TPS half.
Our main project for most of this semester has been making a 4"-diameter vehicle with about the same performance as Silver Spur 3 or SixyBack, but with an oxamide motor. It was designed at the end of last semester and the beginning of this one primarily by freshmen and sophomore members of lab, as a way to transfer skills from the upperclassmen. The designers did a great job with the modeling, simulation, and even coming up with a name: Flying Dutchman, for either Davy Jones's ship or the In-N-Out secret menu item. It's far better than the initial name, Sophomore Test Design.
Progress on Flying Dutchman has been slow but steady, with the fins, bulkheads, motor components, and nosecone now complete. We also made a motor case with the new sealant material -- the one that had worked successfully in the firing in January -- but it did not pass hydrotest, probably because the much larger size of the case as compared to the static fire case made it difficult to lay down the thin sealant layer properly. We ordered a new roll of our traditional sealant material and just completed laying up a new case. Both of these cases used a new 4" mandrel; our old one was too scratched and warped.

As part of the Flying Dutchman project, we made a new nosecone mold that's a 6:1 von Karman ogive -- a more aerodynamically efficient shape than our previous 4" nosecone, and one with enough length for our current avionics package. We machined the plug in house, laid up a two-part fiberglass female mold, and made the flight article last week! Due to our switch of focus to Traveler 2 (more on that later), launch of Flying Dutchman is now planned to occur at BALLS or later in the fall semester.

The nosecone plug on the acrylic support structure which held it during the mold layup.
One factor that has made it hard to stick to our original schedule for this semester was that we had to move the lab to the eastern wall of the high bay in RRB, since our previous space was being turned into a cage for testing UAVs. It was hard work moving everything, but we took the opportunity to dispose of a lot of unneeded equipment and become better organized. Now that the moving process is finished, we're enjoying having a larger and more square lab area, as well as full access to the garage door in the wall of the high bay. We also underwent a safety review process by the facilities office and now have improved safety practices for machining, welding, and other shop activities.

Work on Flying Dutchman is continuing in parallel with Traveler 2, which is planned for launch May 3-4 with a backup of May 17-19. Most of the parts were made in the fall, with the largest remaining thing to do being the motor case, which will be started early next week if the new Flying Dutchman case turns out well. Other tasks include beveling the fins, making the fin alignment guide, fitting the nose tip receiver into the nosecone, bonding nosecone stiffening rings, and machining camera holders. We'll be flying some developmental avionics hardware that, if it performs well, will be used for a custom flight computer and telemetry system we're developing. Stay tuned for news about Traveler 2's construction and launch plans!

Finally, I'd like to remind readers that you can get much more frequent updates about RPL's activities at

Flight on!

Traveler 1 Flight Report
10/13/2013 by Jason Silverman
Traveler was launched on September 21, 2013, after two years of hard work and waiting. The flight ended in an explosion at T+3.5 seconds. Most parts of the rocket were recovered, and some can be reused. Luckily, enough of the motor was intact to piece together the cause of the explosion. This update will cover pre-launch operations, the launch itself, and future plans.

To launch Traveler, we attended the annual BALLS rocketry event in Black Rock, Nevada. The playa, as the dry lake bed is called, is one of the flattest places in the world. It is a 9-10 hour drive from LA, and frequently has harsh weather such as sandstorms. RPL goes to Black Rock once or twice a year to launch our largest vehicles; smaller ones are launched at the Mojave Test Area.

Final assembly of Traveler went fairly smoothly, with successful tests of recovery deployment and avionics transmissions. Everything appeared ready as we packed the trailer on Wednesday.

The scene inside the trailer.

"Area 52" departing.
In a very rare event for RPL, the trailer ended up leaving earlier than scheduled, at 2300 Wednesday. Brake trouble necessitated a stop in Sacramento for maintenance, so the total trip time for the trailer amounted to about 21 hours, justifying why we like to leave with time to spare.

On Friday morning, we drove the trailer out about one mile from the flight line, unloaded the tower, and parked the trailer an additional 300 feet away. Weather in the morning was nice, but heavy winds and sandstorms developed in the afternoon as we took the final steps to prepare the rocket for flight.

The avionics package, minus the outer tube.

The tower area.

Our new launch monitoring software.
It was obvious through most of the afternoon that a launch could not be attempted -- we couldn't even keep the trailer door open for more than a few seconds before the air inside would be filled with dust. We took the opportunity to let everyone sign the rocket:

The FAA had established Temporary Flight Restrictions in the area from 1700-1900 that day, which meant we needed to launch before 1845 to be clear of the airspace by 1900 (something we didn't learn until that evening). When the weather became tolerable at about 1800, we finished integrating the rocket and carried it over to the launch tower. By the time it was vertical and people had taken pictures, we were within a few minutes of 1845, meaning we couldn't launch that day. It was disappointing, but we knew we had additional launch windows the next two days, so we lowered the tower and brought the rocket back to the trailer. The winds were still bad at that point, making the porta potties back at the flight line vibrate like washing machines!

Positioning the tower for the first launch attempt.
The next day, we spent the morning and early afternoon charging batteries and generally being stuck inside the trailer. There was some light rain, which reduced the dust levels. The rain meant that the sedans had to leave the playa and return to Gerlach. Some cars were subsequently unable to return to the playa because of muddy spots at the playa entrances, and watched the launch from Gerlach or an adjacent mountain.

Panorama of the launch site.
Integration went smoothly once again, and Traveler was vertical in the tower at 1710. The weather was still improving, but we had to wait for the cloud cover to dissipate somewhat. Once the clouds were cooperating, a train was spotted on the tracks next to the playa, and we waited about 10 minutes for it to go by. The ignition signal was finally sent by Alec at 1807. The composite igniter took a few dramatic seconds to ignite the whole motor.

Traveler soared almost straight up, obscuring the view of the rocket from the trailer. After 3.5 seconds of flight, at approximately 4000 feet, the smoke trail became abruptly larger and separated into several pieces, followed in a fraction of a second by the unmistakable sound of a solid rocket motor catastrophically failing. The pieces of the rocket arced over, with what was left of the motor still spewing fire from both ends as it cartwheeled. The team split up to run and drive out to the pieces. The nosecone landed the closest, bouncing on the titanium tip; other parts drifted farther, like the motor (which made a decent-sized crater) and the parachute (which went several miles).

The nosecone, largely intact.
We brought the pieces back to the trailer to see what went wrong. The debris included two nearly-intact grains that had been extinguished when the motor lost pressure. They exhibited evidence of backside burning, meaning that the propellant in contact with the casting tube had not been properly inhibited and had started to burn, increasing the chamber pressure. If this had happened on many grains, the pressure increase could have been enough to blow the case; it's also possible that some grains lost chunks of propellant which clogged the nozzle.

A grain with obvious evidence of backside burning.
We view this flight primarily as a chance to learn. We were prepared for the possibility of a failure; after all, Traveler's motto is "space or nothing!" We were ironically reminded of this slogan when it was exposed, written in sharpie, on the outside of the motor case under the tip-to-tip layers -- not a place we ever expected to see again.

As Jordan said:

"We didn't reach our end goal, but we have still accomplished another step on the way. We built a spaceshot, had it on the pad armed and fueled, and fired it. No other group of students has gotten anywhere close to that. I'm excited we have gotten this far  - we had issues - and we'll work through them and will be back soon enough.

"This series of event that led to this moment - including the concept and initial lab development, all the prior projects which tested technologies for Traveler, the lengthy paperwork process, along with the design, build, and rebuilds of it - have spanned nearly a decade. The number of people who have been involved is far too many to list here. 

"For the flight crew - who this past weekend dealt with the worst that Black Rock could offer, part of which locked themselves in our trailer for 7 hours waiting for storms to pass, part of which was stranded by mud blocking the playa entrances, and the countless other oddities that happen out there - you're amazing. 

"Thank you and congratulations to everyone who has helped make this happen."

Traveler's BLM permit included backup launch opportunities 2 and 4 weeks after BALLS. We wanted to use the 4-week window to launch Traveler 2, a rebuilt version of Traveler with some enhancements, but were not able to finish it in time -- and the government shutdown prevented us from using the playa. We'll post details about future plans as they become available.

Finally, thanks to a variety of members for providing pictures that went into this update. You can view them on Picasa.

Flight on!

Traveler: L-1 Week
09/14/2013 by Jason Silverman
For the fourth time in lab history, we're within a week of launching Traveler. This time, we know we'll be able to make a shot, since we have signed FAA and BLM waivers! It's been an intense two-year process by two generations of lab leaders to get approval to launch. Out of it, though, we've made excellent contacts at the government agencies, gotten good advice about how to plan our launch operations, and laid the groundwork for regularly obtaining future clearances.

Even with the two-year delay, there's still a lot of work being done on Traveler. Foremost is remaking the motor, as the original one was fired in May. We also took the opportunity afforded by the delays to redesign the avionics package, adding more advanced components and making the integration method much more straightforward.

Other work includes the tower team practicing the setup of the launch tower, the renovating of the trailer, and the construction of a UAV to track the rocket.

Traveler's phenolic nozzle has been integrated, along with its CNC graphite throat courtesy of Titan America!

We can also officially announce now - if it wasn't already clear - that Traveler's destination is space. It would be the first student-designed and -built rocket to fly there. We expect a maximum speed of Mach 5.5, and an apogee of 350-400 kft (space is defined to start at 328). Our waiver allows flight up to 491,000 feet, above which a commercial launch permit would be required. There are so many variables affecting the flight, from motor performance to aerodynamics to weather, that we can't say anything exactly, just in terms of probability - except that the flight will be spectacular no matter what happens!

We plan for the trailer and chase car to leave near midnight Wednesday/Thursday, with the rest of the cars leaving in groups during Thursday morning and early afternoon. It's about a 10-hour drive if you don't have to obey the trailer speed limit, plus a while for the traditional stop at the Reno Costco.

The waiver allows us to launch during daylight on September 20, 21, and 22 (the three days of BALLS). An afternoon or evening launch would be most likely the first two days, and a morning launch on the third. If weather or technical problems prevent us from launching during BALLS, we will return to the playa during our backup windows two or four weeks later.

Check the blog for some more pre-launch updates. During BALLS, we'll be tweeting occasionally at @USCRPL.

First meeting
08/30/2013 by Jason Silverman
RPL's first meeting of the semester will be at 4:00 PM in MHP 101. Future meetings will be at the same time, but in GFS 106.

Additionally, we're having a lab preview meeting at 3:00 PM in MHP 101 for prospective members who want a more in-depth overview of lab's activities.

There is lots of exciting news to go over at the meetings, including our FAA waiver status, plans to finish up Traveler, and the design of a 200,000'-apogee vehicle to fly at BALLS along with Traveler. BE THERE!

Further archives of news are accessible at the RPL Blog.