MTA Firing Report, 2022-02-05

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.


MTA Launch Event, 2021-11-20

by Dave Nordling, Reaction Research Society


The UCLA Project Prometheus held a static fire event at the RRS MTA for two of their latest designs of their liquid rocket engine. The pyrotechnic operator in charge was Osvaldo Tarditti with Dimitri Timohovich and myself as apprentices for these two static fire operations. This was a liquid ethanol and oxygen engine of the same 1500 lbf design used in prior years. There was a change in the injector pattern and a new ablative liner was used in the first of two engines.

UCLA positions their equipment and makes final checks before inspection from the pyrotechnic operator.

UCLA had come to the MTA on the prior afternoon to begin their setup with plans to be ready for the first of two hotfires when the pyrotechnic operator was to arrive that day. UCLA was in fact ready and after a short review of all plumbing and changes made since last year’s testing followed by the basic safety briefing to all attendees the tanking operations began.

During the pandemic, UCLA had a long pause without access to their laboratory. This time allowed the team to collaborate remotely and consider improving their testing rig which was deployed at the MTA for the first time.

The first engine hotfire had a few delays from the igniter failing to light in the last seconds of the count. The count was recycled with the same result. After the avionics team corrected the problem and the oxidizer supply was replenished, UCLA returned to their countdown and had a generally successful hotfire. The test ran the whole duration but the chamber internal wall ablative liner seemed to not be sufficient and a breach of the chamber jacket was seen.

Chamber ruptured on the first engine at the end of the burn after the ablative wall expired.

After purging the engine and safing the ground test system, UCLA waited for the engine to cool. Photos were taken of the post-test conditions and we all took a break for lunch before swapping engines for the second of two planned tests.

The second engine installed and ready.

The second engine had the old ablative liner material and went full duration without any obvious trouble. Also, the second engine used a small solid motor on a 3D-printed clamp-on mount which worked well. Similarly the engine was purged and allowed to cool before its removal for inspection back at the university. UCLA will likely examine the igniter firing circuit and system before their next engine firing or flight.

Second hotfire went full duration.
Group photo at the end of a successful day.

The team was very proud of the progress made and the data gathered will be very useful in anchoring their next flight vehicle’s performance. UCLA intends to surpass 30,000 feet with this next flight to claim the FAR-MARS prize. UCLA is still the current record holder at 22,000 feet from last year’s flight. Vehicle dry weight reductions in this year’s design and minor improvements to other vehicle systems could make the difference in claiming the prize.

The sun setting after a pleasant afternoon at the RRS MTA.

The old blockhouse had it’s roof replaced two weeks ago thanks to Dimitri Timohovich and other RRS members who lended a hand. Trimming of the roof beams was finished and the blockhouse was used for the first time with UCLA’s liquid rocket static fire.

As UCLA was packing up to depart the MTA, we used the time to build another wire launcher rail for model rockets in upcoming school events with LAPD CSP. Dimitri and his son, Max, launched a few volleys of some water rockets using a special system using an air compressor and solenoid firing box built for remote charging of nitrous oxide based hybrid motors. The system worked well and it was great fun.

Dimitri Timohovich reloads a water rocket based from Smartwater one-liter plastic bottles.
Under his father’s supervision, Max Timohovich prepares to launch the next volley of water rockets in the last hour of sunlight.

MTA launch event, 2021-05-29

by Dave Nordling, Reaction Research Society


The Reaction Research Society held a launch event at the Mojave Test Area mainly to support the UCLA Prometheus team for a static fire test of their high powered hybrid motor. UCLA chose one of the largest nitrous oxide hybrid motor designs, the M1575, made by Contrails Rocketry. Dave Crisalli was the pyrotechnic operator in charge for this event. I was his apprentice for the hybrid static fire.

There were three main activities at this event. The first was the UCLA Rocket Project making their preparations to launch their ethanol and LOX vehicle from the Friends of Amateur Rocketry (FAR) site from the 60-foot rail. FAR is just to the south of the RRS MTA where the UCLA Rocket Project had twice in one day static fired their 750 lbf liquid propellant rocket engine just four weeks earlier on 05-01-2021.

Weather conditions were ideal with winds being nearly still for most of the morning. This makes little difference for the hybrid motor static fire testing at the RRS MTA which was the second project by UCLA. Wind would factor heavily in the flight of the UCLA’s liquid rocket.

The third planned activity for UCLA was a series of model rocket flights from several high school teams mentored by UCLA graduate and undergraduate students. Still winds made for easier recovery of the first rockets launched that day.

UCLA Prometheus team prepares for static fire at the RRS MTA on 5-29-2021
Dave Crisalli gives the MTA safety briefing for the event in the loading area where the model rockets were assembled for flight.
UCLA graduate students conducted the model rocket launches from just west of the large test stand at the MTA

UCLA at the end of each Spring Quarter conducts a launch event where student groups build small rockets with egg payloads using single and dual-stage vehicles with model rocket class motors (G and under). UCLA graduate students and Professor Mitchell Spearrin were leading this event.

It is good experience for beginners and experts alike to build and fly model rockets., The RRS has it’s own such internal program called the Yoerg Challenge which is to motivate all members to build and fly a model rocket kit at least once from the RRS MTA. The RRS is known as an experimental society and not limited to the model rocket code, but we are also fully supportive of all forms of propulsion as long as it is safely conducted and compliant to the regulations set by the state of California.

As the UCLA hybrid rocket team was making their system checks, they discovered a problem in their nitrous filling system and valve commands. During this diagnostic period, some of the RRS members went to the nearby FAR site to see how the UCLA liquid rocket preparations were progressing.

UCLA’s liquid rocket set on the 60-foot rail launcher at FAR. The team preparing the vehicle for erecting, loading then flight.
RRS members from left to right, Bill Inman, Waldo Stakes, John Wells and Manuel Marquez, inspect the UCLA liquid rocket on the 60-foot launcher deployed at the FAR site.
A few last minute fixes and the rocket was made ready.
The liquid rocket sits on the rail before raising it for launch.
UCLA’s rocket is in position getting ready to clear the area for propellant loading and pressurization operations.

Some of the RRS members remained at the FAR site to witness the launch. After two years of design, planning, build and world pandemic, the UCLA team liquid rocket launch was an amazing success. Due to the relatively low winds that day under clear skies, recovery was made just under a mile away. Preliminary data from telemetry confirmed a new university team altitude record of 22,000 feet. It was an amazing sight to witness from the observation bunker at the RRS MTA.

UCLA’s liquid rocket had a perfect launch on 5-29-2021 setting a new altitude record of 22,000 feet by a university team. Photo by Xavier Marshall, RRS.

The UCLA Prometheus team had corrected their initial electrical problem and began the series of procedural checks to familiarize the new members of the hybrid rocket team. Some minor adjustments of the motor mount alignment was necessary before getting into test.

The UCLA Prometheus team makes some adjustments to better align the hybrid motor in the vertical skid mounted to classic I-beam at the RRS MTA.
The nitrous oxide K-bottle sits inverted in the sloped stand to allow the liquid to flow from the port. Some nitrous oxide bottles come with an internal siphon line to avoid having to invert the container. The bottle is also being chilled with ice to keep the oxidizer sufficiently dense and improve performance in hot-fire.
The top bulkhead of the hybrid motor is attached to the load cell for thrust measurement. A pressure transmitter is tapped into the nitrous oxide volume to further gauge performance.
The high-powered hybrid motor by Contrails uses four 1/4-inch fill lines and a single smaller vent line from the same floating injector at the mid-point inside
Dave Crisalli (right) inspects the hybrid motor on the test rails before the firing
UCLA Prometheus team tracks their written procedures as they progress to hot-fire in the old blockhouse.

The hybrid motor firing proceeded without further problems and resulted in a spectacular test meeting expected performance. Continuous thrust levels over 600 lbf were recorded but data analysis is still ongoing.

The hybrid motor at startup.
The UCLA hybrid motor at full thrust. Chamber pressure was over 1000 psia.

The team had a second hybrid motor grain ready for another firing so they proceeded with disassembly and inspection of the parts. The floating injector seals were still in good condition but the graphite nozzle having survived many prior hot fire tests did not survive that day’s test. Although the throat was in good condition, the inlet taper had cracked requiring a replacement the team did not have.

The top half of the floating injector with its internal siphon tube protruding up to near the top bulkhead.
The floating injector being removed from the lower half containing the spent fuel propellant grain.
The floating injector was removed after hot-fire and the dual O-ring seals were inspected. Seals were ok for re-use.
The nozzle assembly did not pass inspection after the first and only hot-fire on 05-29-2021.
The graphite nozzle fractured at the inlet taper from the first and only firing that day.

UCLA Prometheus was pleased with the results from the single firing and will proceed with integrating the motor into their flight vehicle for a launch from FAR on June 19, 2021. The RRS will hold an event at the Mojave Test Area on this same Saturday for member projects and will observe the flight from our northern vantage point.

UCLA avionics team conducted a few tests on the GPS tracking module that will fly on their vehicle in June 2021.

In the last hours of the day, after most of the UCLA liquid and hybrid teams had cleared the area, packaged and carried away their trash, packed their equipment and departed the RRS MTA and FAR sites. The UCLA avionics team remained at the MTA to conduct another series of tests on the GPS tracking system. The society was glad to support this diligence which will help assure success in one of the most important aspects of rocketry which is data acquisition from telemetry. If there is no data, it didn’t happen.

For any group interested in using the RRS MTA for their propulsion related projects, download one of our Standard Record Forms from our RRS.ORG website and submit this request to the RRS president. The society has had a long relationship with UCLA and USC, but we are also supportive to any amateur, professional or academic groups wanting to learn from test.

president@rrs.org