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:
, 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