Last Saturday (February 23), we took a team to Baywood Elementary in Los Osos for their Science and Art Fair. We had a blast launching bottle rockets with the students and helping them build their own rockets to launch! We loved watching the kids learn and get excited over rockets. See you at Cal Poly soon, future rocket scientists!
On Monday, February 18, the team went to the propulsion’s laboratory to conduct a half duration test fire of our experimental propulsion system, HM-8. This hybrid motor uses solid HTPB fuel and liquid nitrous oxide oxidizer, and this year we have been developing a self-pressurized system, where instead of having nitrogen gas as a back pressure to keep nitrous oxide flowing like we had in HM-7, the nitrous oxide evaporates and is used as back pressure. This idea was developed as a possibility to reduce our rocket’s weight. Our previous data from flow tests indicated that the self-pressurizing system had comparable flow rates and pressures to our previous system, so we moved forward with the test fire.
However, we ran into new problems, where because we no longer had an inert gas (nitrogen) to put out the fire after the liquid nitrous oxide burn, the gaseous nitrous oxide continued to let the fire burn slowly. This fire burned through the rest of the fuel, the epoxy liner, and melted the aluminum combustion chamber at a point of high pressure.
We learned the importance of having an inert gas to back pressure our system, and we are going through a redesign process to get rid of using an oxidizing gas to back pressure the system.
Special shout-out to Penguin Computing for all of their support for our club! They donate core hours to let us run CFD (computational fluid dynamics) for our rockets to design our nose cone, fin, and boat tail. We are so grateful for their remote graphics that get us these cool images to analyze our rocket.
This past weekend, CPSS hosted a booth at Cal Poly’s Open House and set up a water bottle launcher in the Engineering Plaza. The water bottle launcher was jointly run by CPSS and the CPSLO AERO department.
Hundreds of prospective students, current students, and their parents came by our two booths and enjoyed seeing our rockets and launching their very own two-liter water bottle rocket. Thank you to Chris Young, Yaroslav Kurakin, Harrison King, Tom Koeitzer, Alaina Standish, Alec Bluhm, and Patrick Chizek for manning the Open House and Water Bottle Launcher booths.
On February 25, 2018, the club conducted a successful test fire of the Hybrid Motor 7 – Heavy propulsion system. The important shift in this test fire is that we have identified and resolved past issues with combustion stability and thrust. Our propulsion team discovered that the regulator between the pressurant tank and the oxidizer tank was not sufficient, and there was not enough flow for our larger heavy variant of Hybrid Motor 7. We placed two of our smaller regulators in parallel for this most recent test fire, and we produced sufficient thrust to clear the launch rail with a safe speed. The thrust curve for the engine is below:
This test served as a proof of concept that increasing flow between our tanks will increase our thrust. With a new single regulator with a higher flow coefficient, performance may even increase beyond what we have achieved in this test. The next steps are to do a full duration test fire to verify the engine continues to operate for a full 17 seconds, and a test launch to verify the system as a whole is ready for IREC. The video of our most recent test fire can be found here. Look out for more updates!
Every year, we start our new members off by breaking into teams and building smaller rockets, approximately the size of a level one certification rocket. The goal is to fly as high as possible and return an egg stored somewhere within the rocket. On 4 November, CPSS took some of our new members out to Friends of Amateur Rocketry (FAR) with their new rockets to see who best accomplished the goal.
While Double Double had a perfect liftoff, the parachute failed to deploy and the mission ended in a crunched body tube and egg. USS Struggle and 🅱️elvis 🅱️resley flew well with perfect landings, but both eggs were lost at some point during flight. In second place, with a peak altitude of 1362 feet, was Starlord. The winner, with a peak altitude of 1782 feet and a perfect recover, was Humpty Dumpty. Congratulations to the team, and to all of the new CPSS members!
Since the conclusion of our last year, Cal Poly Space Systems has completed an overhaul of the propulsion system in our Kronheim rocket. Due to the national nitrous oxide shortage in early 2017, we were unable to complete all of our testing objectives and decided not to attend IREC. Our five test fires gave us very useful data, but we did not want to launch Kronheim without being sure of success. We are starting this year with much progress on the Kronheim rocket already completed. We redesigned our injector to optimize thrust, and have a tentative plan to complete a number of test fires before 2018. We have decided to keep HTPB and nitrous oxide as our chemical propellants, as the nitrous shortage will not affect us this year.
Our officer and lead corps is the most experienced group to lead the club in many years, and we expect swift progress in the completion of the Kronheim rocket. Much of our work thus far into the year has been in planning and preparing for our new members, as well as establishing a 2017-2018 timeline and schedule. We have split our new members into teams to design their cert rockets. We will attend the October Skies event in the middle of Fall Quarter to launch the certs in our annual egg launch competition.
On May 27, Cal Poly Space Systems conducted the first successful 2/3 duration test fire of the HM-7 Heavy hybrid motor. Using data from this test, we were able to build a thrust curve:
As expected with a 2/3 duration test fire, thrust drops at around ten seconds as nitrous oxide (our oxidizer) mixes with nitrogen (our pressurant). Stable combustion occurs for about 10 seconds, and is followed by approximately 5 seconds of unstable combustion. Additionally, the video (final phase of test begins at 23:45) provides a qualitative confirmation to our quantitative data. Average thrust over the entire test was about 520 pounds. We are very pleased with the results of this test!
This test fire is a significant step forward in our progress to IREC, and serves as a complement to our previous short duration test fire. The 2/3 duration test also demonstrates that our new HM-7 Heavy design can withstand temperatures and pressures associated with sustained stable combustion. We hope to conduct at least one more test fire before the final trip to IREC.
With Spring Break starting at Cal Poly we have good news to share about our IREC competition rocket development. We have completed multiple tests and have decided on the rocket name – CPSS will fly Kronheim at Spaceport America.
Multiple payload designs were considered in past months. The final decision is to develop a payload capable of collecting flight data for further development of the active guidance system. Payload design and manufacturing is mostly handled by the avionics team.
Payload bay CAD model
The recovery team finished mechanical design of the recovery system and started production of the main parachute. The team is preparing for a full system test, which will give us data to complete parachute sizing.
The system integration team has performed tensile testing of student made composite materials and has finalized design of the rocket structure. The fiberglass nose cone was manufactured a few weeks ago. Test flight honeycomb fins and the bulkhead are in production over break.
Tensile test results
With systems and recovery well on the way, we plan to perform a test flight at FAR on April 15, 2017. Goals of the flight include test of structural integrity of the rocket body, honeycomb fins and bulkhead, recovery avionics, and recovery mechanism. One of the major objectives is to observe shock during main chute deployment, the data will be used to finalize size of the competition drogue parachute.
The propulsion team finally has a hydrostatic test procedure approved by University Environmental Health and Safety, thanks to our Student Safety Officer Chris Young. The combustion chamber was successfully tested to a Factor of Safety of 3, and the nitrous tank will be tested next week.
HM7-Heavy test fire assembly
Ground Support team has been making final changes to the system. We have significantly improved safety by adding 3 relief valves and 4 pressure sensors in the GS box. Final modifications are planned to be completed in upcoming week.
Both Propulsion and GS are looking forward to perform a test fire in first few weeks of the Spring Term. Follow our youtube channel for test fire videos.
The second term of 2016-17 academic year has started and CPSS has some good progress to show. We are well on track for #ESRA 2017 Spaceport America Cup in June.
Avionics team has developed recovery board, manufactured hardware for the active guidance system, and well on the way to perform flight test in next 7 weeks.
Recovery team has completed separator device, which is going to be flight tested with Avionics. They are also about to finish design of the parachute, materials for which will be purchased in upcoming week.
Ground Support has completed new design for the system, as well as purchased required components. GS-Rocket interface has been redesigned as well, implementation of new quick disconnects is under way.
System Integration team has been focused on developing a new technique for manufacturing and attaching the fins that will not interfere with the integration of the propulsion system. New design employs honeycomb composite structure. The manufacturing of test fins took place over last weekend. The fins were tested last Friday (January 20th) for strength to assist the Recovery Team in determining parachute size an allowable impact velocity. A similar honeycomb design will be used for the bulkhead to support the loads from the parachute, and the centering rings for the N2 tank and parachute tubes.
Propulsion team has manufactured all major components of HM-7 Heavy over Christmas Break. Nitrous tank and combustion chamber are ready for hydrostatic test. Nozzle and injector are ready for test fire. All active plumbing components have been purchased and have arrived. Rest of the plumbing has been purchased as well. With a major setback of the timeline due to issues with hydrostatic test procedures approval, team has to delay short duration test fire by time unknown at the moment. Even with the setback, propulsion is still on track for launch in June.
CPSS is looking forward to upcoming testing. We have done a lot of manufacturing in past three month and we are looking forward to test every component of the system in next 12 weeks.