Tag Archives: liquid oxygen

MTA Firing Report, 2025-11-01

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by Dave Nordling, Pyrotechnic Operator, RRS.ORG

The Reaction Research Society (RRS) held a liquid-fueled static fire event of the UCLA Rocket Project’s latest designs at the Mojave Test Area (MTA) on Saturday, November 1, 2025. We also had a member project that day with Austin Sennott and Charles Sharp launching three versions of their Half-Cat design.

The weather was quite good all day with very low winds and mild temperatures. The teams seemed well prepared and briefed me on their operations prior to commencing propellant operations. RRS member, Bill Nelson, assisted me in overseeing the event as my apprentice.

UCLA’s first static firing had a no-start condition on their igniter due to an open circuit which was easily corrected, but the team opened the run valves dumping the alcohol and liquid oxygen. For safety, the team ran the tanks until empty and simply waited to let the reminder of the liquid left in the horizontal internal space of the engine evaporate. UCLA would correct their operational mistakes on the next run.

While the UCLA engine was drying and the system rendered safe, the Half-Cat team got the next operation and conducted fuel filling and remote nitrous oxide filling. The Half-Cat design has flown nearly a hundred times at both the RRS MTA and FAR. They had three successful launches one right after the other. All vehicles were recovered with only one recovery system getting tangled. The HalfCats flown that day were gasoline and nitrous oxide which was loaded by a remote controlled system from the Garboden bunker.

UCLA returned to their static-fire operations after the HalfCat team was complete. They corrected the problem with the igniter and replaced the engine. The second run was a little more successful.

The UCLA team is testing the latest iteration of their ethanol (75% with water) and liquid oxygen impingement injector. It has an ablative liner running the whole chamber length to a graphite converging-diverging nozzle plug. An aluminum shell provides structural strength holding the assembly together. Ignition of the engine is by a nozzle-mounted pyrotechnic igniter (model rocket motor) held in place by an external clamp. The system has worked well in recent iterations.

Firing operations on this second attempt proceeded as planned with a clean, steady burn. Unfortunately, near the end of the run, the engine experienced burn-through and the chamber ruptured upstream of the nozzle in the upward location. Operations concluded safely and after a cooldown period, the engine was inspected. The data suggested the chamber pressure and mixture ratio was higher than predicted, but the ablation of the liner seemed relatively even circumferentially. The G10 plastic liner was thought to be able to last longer. Some concern was raised about variability in the product used today versus that used in the past. The failure was relatively benign and adjustments to the propellant feed should correct the issue.

The UCLA team intends to fly their next vehicle for the FAR-MARS competition at the end of the Spring Quarter 2026. The single engine tests are necessary steps in selecting the right design for the best outcome. Although the sun was getting low, UCLA requested a third test with their next engine prototype. The team worked quickly to install their last engine of that day.

The team finished the installation, verified no leakage and began fuel and oxidizer fill operations. Remote pressurization operations went well and the team proceeded into the count. The second engine fire was steady and ran to completion. The pressurants were bled down and the system rendered safe. After some cooling off, the engine was inspected.

Some sparks were seen exiting the plume and some graphite ablation (small chunks popping out) at two locations around the convergent side was detected during inspections after engine removal. This is somewhat normal for some types of graphite. The UCLA throat design has a more gentle contour that can permit some of this undesirable ablation pattern without opening the throat area and decreasing performance.

The second engine firing was a success in that it could be reused. UCLA had a third design that was 3D-printed and regeneratively cooled, but no further operations were permitted that day given the late hour. The UCLA team expressed interest in returning to the MTA for another round of testing. The RRS is glad to assist university teams with their projects.

During UCLA’s last installation operation, I took the time to look at the RRS’s second 60-foot launch rail which is still under construction. The Jurassic Launcher is so named as the underlying custom-built hydraulic lift system was one of a few used 30 years ago in the 1992 movie, Jurassic Park. The RRS was glad to purchase the system and is in the process of refurbishing it for liquid rockets needing a longer run length.

The steel backbone structure was a radio tower donated to the society by RRS member, Waldo Stakes. Some welding repairs have been completed and a short extension was put at the end to give a full 60-foot run length. The backbone needs a little more of the finer work to get the rail lugs installed. There is also some work to be done replacing hoses, cleaning and rebuilding valves and the pump if needed, building structural pieces, mounting and integration of the backbone and restoring the reservoir tank. Once finished, Jurassic Launcher will be a valuable asset to members and clients at the RRS MTA

Austin and Charles gathered all three of their rockets and gathered valuable data with their prolific and growing flight history at the RRS. Several members indicated their interest in building a HalfCat or a derivative version. I was also grateful to them for their professionalism and efficiency in operations. They were a good example for the teams at the MTA.

I was also grateful to the UCLA team who similarly showed maturity and patience in their operations which led to useful results despite a few setbacks. They policed the area for their trash and loaded their equipment for departure with practiced ease.

For those groups and members wanting to use the RRS MTA, contact the RRS president, Frank Miuccio. president@rrs.org

The next monthly meeting of the RRS is every 2nd Friday at the front office of the Compton/Woodley Airport. Next one will be December 12, 2025.

MTA Firing Event, 2022-07-31

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by Dave Nordling, President, Reaction Research Society

The University of Michigan came to the Mojave Test Area for another static fire campaign starting Monday, July 25th and ending July 31st. Pyrotechnic operators, Jim Gross, Osvaldo Tarditti and myself supported this protracted campaign in the July heat. The weather was challenging during that week with few heat-related problems other than slow progress which is understandable given the conditions. New RRS member, Rushd Julfiker, and long time member, Jim Gross, assisted me in the cold flow and hot-fire testing. MASA’s academic adviser, Professor Mirko Gamba was also present at the MTA for the days of cold flow and hot-fire testing.

University of Michigan held a Test Readiness Review on Sunday, 7/17/2022, with RRS members present. Many good questions were raised but few corrections were needed. MASA proceeded with packing and departed campus for the MTA on Friday, 7/22/2022.

University of Michigan first day at the Mojave Test Area

The team arrived at the MTA on Monday night (7/25/2022) and began to unpack their gear and assemble the mobile test trailer. Leak checking went more smoothly due to design improvements. Problems with the igniter channel would prove to be a recurring concern.

Initial setup of the mobile trailer at first arrival.
Attaching frequently used tools by retractable tethers means never hunting for the right wrench again. Genius.
Hewlett-Packard film crew prepares to have interviews with the students.
Control trailer operations leading up to test.
A clean injector ready to be installed.
Fuel transfer operations before next test.
230-liter cryogenic liquid cylinders from Linde.

On Friday (7/29/22), gas bottles and cryogenic liquids were recieved from the supplier. Delays in receiving these consumables allowed sufficient time to verify systems were ready. MASA achieved significant progress towards hotfire after completing four valve timing coldflows and one abort test. Analysis of the data from our tests in preparation for hotfire tomorrow.

The RP-D2 engine sits on its thrust stand.
University of Michigan’s mobile test trailer beside the vertical test stand

Saturday (7/30/22) was the first attempt at hot-fire which was unsuccessful due to an igniter failure. The cause was traced back to an intermittent problem with the switch in the junction box. The prior igniter test demonstrated the igniter would fire in the cold flow conditions the day before. Comparing data sets, the team found that a simple verification of continuity in the voltage data stream during the countdown would safely identify a failed igniter firing circuit and allow a safe abort if it were to repeat.

RRS members Jim Gross and Rushd Julfiker examine the setup before the next test attempt.

In the last hour of the last day (Sunday, 7/31/22) of the campaign, MASA completed a successful 1 second hot-fire of the 2,000 lbf RP-D2 engine. The chamber and injector remained intact and the system safed itself properly.

Screenshot from the 1-second firing of RP-D2 as seen from the Garboden bunker

After examining the data, pressures were significantly off from the expected profile, but the engine passed the visual inspection After further consideration, the team opted not to proceed with a longer 4-second burn due to the uncertainty about our data values and pressure drops seen from hot-fire. MASA would conduct a more thorough examination of the data and hardware back at the university.

The MASA team began cleaning up the test site on Sunday night and continued throughout the night to prepare for the 1800 mile jouney home. University of Michigan was extremely happy with the result of their campaign and were grateful to our pyro-op’s and membership that supported every day with the MASA team.

The RRS was glad to provide our testing site, resources, experience, labor and insight to this successful testing campaign.

For inquiries about using the RRS Mojave Test Area, contact the RRS president.

president@rrs.org

MTA Firing Report, 2022-02-05

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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.

New launch control and instrumentation boxes.
Cryogenic liquid cylinder mobile cart used to place the vessel behind the vertical test stand frame

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,

Ethanol fuel transferred to the propellant tank by a low-pressure gas supply while the tared vessel is wieghed on a scale.

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.

View of the clamshell fixture holding the igniter before the first attempt on the first motor,

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.

The modified igniter holding fixture with added vent holes.
UCLA removing the first engine and associated vehicle systems mounted to their vertical frame.
Facility connections being made as the mobile test stand is put in place.

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.

Second engine being put into the mobile stand,
Preparations for the second engine hot-fire run out to sunset,
UCLA in the blockhouse for final checks before firing

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.

Hot-fire of the second engine by UCLA.

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.

UCLA posed for a photo after the hot-fire and just before the lengthy teardown in the cold hours of the evening.

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 ”president@rrs.org” for those interested in similar projects.