by Dave Nordling, President, Reaction Research Society
The University of Michigan came to the Mojave Test Area for another static order phentermine 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 cytotec for the MTA on Friday, 7/22/2022.
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.
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.
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.
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.
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.
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.
The RRS Mojave Test Area (MTA) was used by the student group, Michigan Aeronautical Science Association (MASA) of the University of Michigan at Ann Arbor. Given the remoteness of the RRS MTA and the great distance that the Michigan team was willing to travel, MASA had planned an extended test campaign to use the site for their cold flow and ultimately hot-fire their RP-1/LOX 2,550 lbf liquid rocket engine. Originally planned for a week, the team arrived on Monday, August 16th, and continued to use the MTA site through August 28th. In the end, Michigan faculty called the end of the MASA test series as the new semester was starting and many materials needed to be returned before MASA left southern California.
MASA is a new student group to the society and had very ambitious goals in what they wanted to accomplish in the planned test series. Typically, the RRS will work with new universities and new clients over a period of many months before agreeing to a first test series at the MTA on a weekend campaign. Proper planning is an essential requirement for success and the RRS must become thoroughly familiar and comfortable with all planned use of the MTA site. Like with all attendees to the MTA, indemnification waivers were required from all attendees including spectators. MASA limited their staff to only essential personnel and ran a day and night shift to both safeguard their equipment through the night and provide continuous support to prepare for the next day’s events. The team was able to find rented housing accommodations in the local areas of California City and Ridgecrest.
MASA has had a couple years of experience with their propellant flow systems in laboratory tests at the university and was willing to hold several meetings with RRS members sharing their full test procedures and schematics, and answer questions posed by RRS pyrotechnic operators in advance of their arrival. The MASA fluid systems had many appropriate safety features and used high quality valves and parts. MASA has developed a control system that uses motorized needle valves in place of a pressure reducing regulator for independent propellant tank pressure controls. MASA had conducted many tests of this system and held several tests to confirm proper operation in the early steps of their MTA campaign.
MASA’s system designs also had some problems with the nitrogen compressor (booster) system being unable to operate due to a regulator failure. The team was able to bypass the unit, but it limited the top pressure of the blowdown tests to the bottle pressure (2000 psi). A few changes were necessary for vent line routing to improve operational safety. Remote pressurization operations were safely executed but proceeded very slowly and thus a great degree of boiloff in the LN2 limited run time.
The event was successful in some respects that it gave the students a practical understanding of how to conduct test operations under desert conditions. It also revealed some of the shortcomings in their plumbing design (leaks) which they were able to fix well enough to get to cold flow with cryogenic LN2 and water on the last day of testing (when this report is dated). The cold flow tests provided useful data in their control algorithm which will be useful to the next series of tests. MASA also gained experience in safe cryogenic tanking and operations with these hazardous fluids.
Logistics was a big challenge for the MASA team due to errors in their communication with local suppliers. Nitrogen and helium gas bottles were significantly delayed and cryogenic liquid nitrogen cylinders also were very late to arrive at the MTA. Some of these problems can be easily mitigated for the next test campaign now that relationships have been better established. While MASA was disappointed with some of the outcomes from the test series, they are interested in returning to the RRS MTA in the latter part of this calendar year. This follow-on test series will be discussed at length in the coming months.
The society was similarly challenged in supporting this MASA campaign. The society is grateful to everyone who assisted at the MTA (Osvaldo Tarditti, Waldo Stakes, Bill Inman and myself) or those who gave their comments and concerns (Larry Hoffing, Jim Gross). Several members spent multiple days at the MTA both during the week and on weekends. The RRS provided the necessary oversight during the hazardous portions of the testing campaign which was particularly difficult to schedule during weekdays. The MASA team was very open and disciplined in their interactions with the society. The RRS was also glad for the University of Michigan’s support and communications throughout this event.
It was a challenging event which was made possible by the contributions of many RRS members over many days. Frequent communication between MASA faculty and the RRS was a firm requirement on all days of this tenacious campaign and the MASA team provided daily briefings on their progress.
This testing campaign and current RRS policies will be discussed at the next monthly meeting, 9/10/2021. Pursuant to our mission statement, the society is glad to support projects of this kind to universities capable of conducting safe experiments at our unique testing site and to those who are willing and able to provide the society with sufficient advance notice to review their reports, schematics and inspect their hardware. This campaign is firm proof that we will need more licensed pyro-ops and more members available to support any similarly extended test series in the future if they are accepted by the council. By building and enforcing a consistent and fair policy for all new and prior clients, the RRS can better operate to the benefit of everyone.
All requests to use the RRS MTA must be made to the RRS president and reviewed by the executive council. For any questions about this test series or any future test series, please contact the RRS president.