by Dave Nordling, President, Reaction Research Society
The University of Southern California (USC) Rocket Propulsion Laboratory (RPL) held a static fire test of their third solid motor design in the Earthshaker series. Prior designs resulted in failures and incremental corrections to the design were made for this test. Earthshakiiest was to be the largest impulse motor made by any collegiate team. Osvaldo Tarditti was the pyrotechnic operator in charge.
Given the repeated recent failures of USC motor designs, the society required protective barriers installed in the event of another energetic failure. Unfortunately, this would prove to be a wise choice as failure did result right at startup. All personnel were at a safe distance or behind appropriate barriers.
The extreme heat from the explosion and fire destroyed the static fire stand, melted portions of the shielding and severely damaged the mounting points such that further use is not possible. USC is working with the RRS to clear and clean up the pad. Many of these tests are very dangerous and can damage our facilities. The society expects all groups to repair, restore or replace any of our assets damaged. A new method of holding future large solid motors is being discussed.
The society thanks our former president, Osvaldo Tarditti, for supporting this event as the pyrotechnic operator in charge and to Bill Inman for also supporting the event on behalf of the society. The operation was conducted safely and much was learned despite the poor outcome. USC will provide details from the testing soon and a path forward,
The latest meeting of the Reaction Research Society took place via video call on Friday, February 11th and had eighteen attendees.
DISCUSSION ON USC RPL STATIC FIRING – EARTHSHAKR III
The meeting kicked off with a discussion of the static fire that was to be conducted the following day at the MTA. Osvaldo Tarditti will be the Pyro Op in charge. The wear and tear of testing has become evident on the concrete pad near the vertical test stand, and a question was raised about the best option for future tests by USC at the MTA. Some RRS members raised concerns about any additional drilling into the concrete, and have expressed a desire to eliminate the tripping hazard of permanent bolts. One option discussed and preferred by some members was launching in a vertical orientation. Other members prefer the horizontal orientation that USC has been using.
All members agreed that safety is the #1 priority. John Krell recalled having a friend die in the 60s from fragments of a metal casing that exploded. USC uses a carbon fiber casing, which produces much less dangerous fragments in the event something goes wrong. Fiberglass was mentioned as another alternative safer than metal.
REMINDER TO PAY DUES
We received another reminder to pay dues for 2022 from the Treasurer:
$40/year for full members was due on January 1st
$20/year for student members
Pay via PO Box or “Donate” button to the right
PRESENTATION ON THE COMPTON COMET PROJECT
Joel Cool-Panama and Manuel Marquez presented on the progress of the “Compton Comet.” This RRS project utilizes a 1,500 lbf LOX/ethanol engine. The rocket is under construction at Tomorrow’s Aeronautical Museum at the Compton/Woodley Airport.
Both presenters (Joe & Manuel) are RRS members and students at CSU Dominguez Hills. The hopes are to complete a static fire of the liquid rocket engine at the MTA sometime this year.
UPDATES ON MTA SITE MAINTANENCE & UPGRADES
The discussion then moved to the progress on site upgrades and maintenance: namely the new bathroom and the repair of the Dosa Building window that was broken during Bill Inman’s destructive propane bottle test. On the bathroom front, there was little progress to report. Dimitri is taking the lead on bathroom construction but had been working on pyrotechnics for the Los Angeles Super Bowl, which understandably left little time for the bathroom construction. Progress is expected to pick back up in the upcoming weeks.
Osvaldo outlined the plans he had to repair the glass in the Dosa building. Because this is not the first time a window had to be replaced, Osvaldo designed an aluminum frame which locks into place and allows removal and replacement of the pane from inside the Dosa building. He intends to install a plexiglass panel in the place as a test. It would likely be more resistant to shattering, but may get cloudy or present other unforeseen issues. The only way to find out is to test it!
DISCUSSION OF BILL INMAN’S DESTRUCTIVE TEST
As mentioned earlier in this post, Bill Inman conducted an elevated temperature burst test of a 5-gallon (20-pound) propane container partially filled with water. A detailed report on that test from Bill can be found here.
DISCUSSION OF UCLA LIQUID TEST FIRING
Earlier in February, UCLA planned 3 liquid rocket engine tests in a single day – an ambitious goal. A summary of the day from the Pyro Op in charge, Dave Nordling, can be found here.
UPDATE ON THE NEW FEE STRUCTURE FOR MTA USE
The executive council approved a new fee structure for use of the MTA, which are specific to non-RRS members. RRS members are still allowed to use the site with the usual requirements in place. The new fee structure is as follows:
$1,000 / day for schools
$1,500 / day for private companies
A minimum 14-day advance notice is required, and reservations are subject to availability of Pyro Ops qualified to oversee the testing taking place.
UPCOMING MTA EVENTS
The MTA has a busy several months coming up. Frank updated the membership on the student classes, a new set of which will begin on the 23rd of February for the LAPD Strive class. Classes are scheduled once a week through March with the launch on April 2nd. Another set of classes with the YMCA will begin in early April, with a similar schedule and a launch date set for May 1st.
The University of Michigan has requested the MTA be reserved for a testing campaign on a LOX-RP1 liquid rocket engine from May 6th – 13th. USC has also expressed interest in conducting further testing in the near future.
Wolfram Blume updated the membership on his project the “Gas Guzzler.” He is finalizing the re-build of the parts damaged in the last flight and hopes to have the repairs complete in late-February, with a new launch shortly thereafter.
NEXT MONTHLY MEETING
Chris Lancaster has been corresponding with a museum in Germany who has one of George Garboden’s rocket motors installed in a racecar. They are preparing a presentation for the March meeting about this machine of interest!
The next RRS monthly meeting will be held virtually on Friday, March 11th at 7:30 pm pacific time. Current members will receive an invite via e-mail the week of the meeting. Non-members (or members who have not received recent invites) can request an invitation by sending an email to:
Please check your spam folders and add firstname.lastname@example.org to your email whitelist to make sure you are receiving the meeting invitation.
by Dave Nordling, President, Reaction Research Society
UCLA Rocket Project conducted a static fire test series at the Mojave Test Area on February 5, 2022. i was the pyrotechnic operator in charge for the event. Bill Inman of the RRS was also present as my apprentice in overseeing operations leading to hot-fire that day. UCLA returned with improved launch control and instrumentation boxes. They also invested in plastic tube mounting fixtures for cleaner routing of their low pressure plastic pneumatic lines.
UCLA had three liquid engines prepared for testing which was a very aggressive goal. Some problems occurred in ethanol fuel tanking operation which resulted in a minor spill. Ethanol is volatile and very flammable, but dissipates quickly and doesn’t pose a lasting hazard or contaminant.
The issue was partially with the procedure lacking precise metering of a prescribed volume and part with a lack of coordination between the teams. Fuel loading is not considered one of the more challenging tasks but even simple items can cause serious problems if the team fails to keep their focus, The RRS has recommended UCLA reconsider and revise their procedures as needed but also to take a wider view of what operations are in place and who is doing what, where and when. Coordination is a full time job requiring diligent leadership and responsible participants,
The first engine in the series was a modified version of a prior impinging injector used in last year’s flight. The team was able to complete propellant loading and retreat back to the blockhouse for pressurization operations. All proceeded well until the last part of the countdown.
Ignition failure scrubbed the first firing attempt as the F-sized rocket motor lit but propelled itself downrange pneumatically under excessive pressure built up enough to eject the fixture off the engine before the team could commit to firing. Per UCLA’s procedures, the spotter correctly indicated ”no fire” which caused the launch team to safely abort the sequence. The team held on the release of the pressurant and opted to remotely relieve the system as allowed in their plumbing design after the umbilicals were released. As there was no remote means of draining the LOX, the pneumstically actuated vent was left open to allow the LOX to boil out and with sufficient time elapsed the team was able to approach.
The 3D-printed clamp-on fixture that held the igniter was examined and reassembled. The decision was made to drill large vent holes in the plastic two-piece clamshell which would help in the next firing attempt. Unfortunately, the second firing attempt failed to achieve ignition. This time, the spotter did see and hear the F-sized hobby motor fire but the igniter was not energetic enough to light the initial propellant streams. The LOX and ethanol streamed from the engine during the blowdown period and quickly evaporated without fire or explosion. This is a potential failure mode that all liquid hot-fires must plan for. Ethanol and liquid oxygen do not contaminate the area and are quickly dissipated but a chilled pre-mixture of fuel and oxidizer is quite dangerous.
Duringn the hardware switch, we had some discussion about different methods of ignition including automotive diesel glowplug systems and high-voltage stungun transformer cells all powered by 12-volt battery or capacitor-based small power sources, Both would require significant development and only a test with cryogenic propellant would be a fair test of these devices. UCLA had some interest in exploring these options but it would have to wait to the next academic year.
I discussed UCLA’s methods of scrubbing their test and recommended they put in a safer means of draining their LOX and ethanol in future operations. This will be discussed before subsequent tests at the MTA.
UCLA has had good results from pyrotechnic igniters using cut-down lances, but these are not easy to acquire as they are ATF-regulated. UCLA decided to try hobby rocket motors which had problems in this first engine test series. The only option forward was to continue using the vented fixture fitted for F-motors and a hope a prior ignition failure did not occur.
With the mobile test stand in place, the second engine tested was the injector design that will fly on UCLA’s rocket. It is the same one used lsst year which worked well. The first injector was unable to be tested that day due to ignition problems and UCLA’s decision to proceed with the second engine as their backup. Time was becoming short as the late afternoon arrived and UCLA had to switch over to their mobile testing rig which would hold the second and third engines when tested.
Liquid oxygen quantities in the cylinder ran low and full oxidizer tank load wasn’t possible for what would be the last test of the day. After finishing the LOX tanking, UCLA retreated to the blockhouse for final checks before second firing. No igniter problems were seen with this second engine, but it was a possibility given the recent problems with the first test series.
The hot-fire went to nearly full duration but the burn likely finished fuel rich. Some buzzing was evident so UCLA will review the data to see if the same instability seen in prior firings was present. It didn’t seem to be damaging and if the performance is still sufficient UCLA should have at least one good engine to fly in May when they try to surpass the university-built liquid rocket altitude record.
The third engine was left for a later test date. UCLA is considering another hot-fire series but only after a full review of the data from February 5th.
My thanks to fellow RRS member, Bill Inman, for making the long drive from Carson City, Nevada to support this test.
Also, a big thanks to Eric Beckner of Friends of Amateur Rocketry for staying late and handling the return of the liquid oxygen cylinder.
The RRS is glad to support university teams with our unique facilities at the Mojave Test Area (MTA). Contact the society at ”email@example.com” for those interested in similar projects.