Launch N-2 rocket

The day has come. We finally launched the N-2 rocket we developed.

N-2 rocket in flight

Preparations continued until late the night before the launch day. It was already past 8 PM when the team left the building.

This time three rockets were launched as the N-2 rocket family. They are named Tana, Galana, and Perkerra, respectively. These were named after rivers in Kenya.

Tana Rocket with a reaction wheel
Galana rocket which deploys the parachute by command from the ground station (manual override).
Perkerra rocket with attitude control using a canard

The following are some of the positive aspects of this launch.

  • Worked with KSA to launch three N-2 rockets
  • The solid rocket motors worked well. It was especially good to discover a technique for bending the edge of the combustion chamber with a hammer in the field.
  • Telemetry allowed us to downlink sensor data and camera images to the ground station
  • ESP32 reset problem was encountered in the field, but was troubleshooted by the avionics team
  • Pyrotechnic (crimson powder) worked and the parachute was released
  • Launch sequence was created and the team complied with it
  • Perkerra flew stable and achieved maximum apogee among three rockets
  • Airframe accommodated all the subsystems without failure

On the other hand, areas for improvement are as follows

  • Management issue
    • Development timeline
    • Avoid last minute work
  • Technical issue
    • Recovery system must be seriously prioritized
    • Entire rocket subsystems have to be redesigned for smooth assembly
    • Add internal memory to store the logging data
    • Launch pad needs to be paid attention as it is crucial

We had a post-flight meeting to discuss the way forward.

The internship which will begin next January will focus on improving organizational issues as a top priority.

23. November 2022
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Testing flight computer using drone

Today, the avionics team conducted tests on the flight computer using a drone. The first test was to confirm the operation of the state machine. The flight computer of the N-2 rocket has a mechanism that detects and transitions between five states: initial state, ascent phase, apogee, descent phase, and landing phase.

The test will be conducted near a dam on campus. Just prior to the test, students from the GIS department were using a drone in a practical to measure the depth of the dam water.
Suspend the avionics bay as the payload
Drone begins to ascend

The operation of the state machine was successfully verified. The next step is the long-distance communication test. We confirm that the sensor and camera videos are transmitted via Wifi without any problems.

Direct the Wifi antenna at the drone to communicate

The test was a success, as sensor values and camera video were received up to 500 m, as expected by the N-2 rocket.

18. November 2022
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First successful combustion test of N-2 motor (full grain)

One week to go until launch. Today was the first successful full-grain test of the N-2 motor. The modifications made to the final single-grain motor included changing the nozzle and combustion chamber from aluminum to mild steel and deepening the grooves in the snap ring. Arriving at the rugby field where we usually conduct our tests around 3:30 p.m., we found a group of new students visiting the site. Today’s test piece was a full-grain solid-state motor to be installed on the N-2 rocket, which had been postponed from last Friday’s test due to an ignition system failure. Again, the test motor that has been successfully tested so far is a test motor that outputs only half of the thrust required for the N-2 rocket manufactured for verification purposes, and the final product, the N-2 motor (i.e., full grain), has never been successfully confirmed in a static test.

Below is a video of the static test. Countdown! 10, 9, 8,…, it has ignited at 7 but the nozzle and bulkhead did not eject as before, nor did the side walls of the combustion chamber. The combustion is complete without melting. A memorable first successful combustion test for an N-2 motor!

First successful combustion test of N-2 motor

The following video is an extract of the combustion section. It shows gas leaking from the gap between the nozzle and combustion chamber; a malfunction of the O-ring was suspected, but according to the student, he was able to visually confirm that the side wall of the combustion chamber had slightly expanded before today’s static test. It is not known at this time whether the deformation was caused by the load during processing or by heating from previous static tests, but we will verify this in the next combustion test. In addition, the connection between the nozzle and combustion chamber, where the heat flux is at its maximum, is red hot. We will measure this area with a thermography in the next round of testing to analyze and evaluate the strength loss due to heating.

The thrust curve sent by the student at night is shown below. One unfortunate note is that the offset value at zero time, 170[N], occurred, so the measured thrust of 460N could not be justified. This will be an area for improvement next time.

Thrust curve

The solid motors we tested were manufactured last Wednesday, so they are about 6 days old. Experience shows that the performance of our solid motors deteriorates with the passage of time after manufacture. Therefore, we decided to conduct a combustion test this Friday using a motor that was manufactured immediately after (i.e. 2 days old).

The motor after the combustion

16. November 2022
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Tour of the Physics Department’s drone equipment

I visited the laboratory of the Department of Physics with members of the Drone Research Group (website: Drone Research Group at JKUAT). The chair of the Physics Department, who is a member of the drone group, suggested that they show us the drone equipment that the Physics Department owns. This equipment was donated to JKUAT in 2021 by GRSS (Geoscience and Remote Sensing Society), a part of IEEE. (Reference: Varsity Receives Drones from American based Engineers’ Society to aid Research)

As to why drone equipment was provided to the Physics Department, it has to do with the course offerings in JKUAT’s Physics Department.

  1. Control and instrumentation
  2. Renewable energy
  3. Geophysics
  4. Physics

In course 1, the research deals with scientific observations using laboratory-made electronic circuits, and previously used high-altitude balloons and Cansat. The use of a new drone will allow for a wider range of observations, and it was deemed appropriate to provide this to the department.

When I first heard about “instrumentation and control”, I wondered why this course is under the Department of Physics. I understand that it is positioned under the School and Pure and Applied Science in terms of designing and implementing electronic circuits for scientific observation and acquiring data. There still seems to be a graduation project where students try to implement a PLC (Programmable Logic Controller) system, which I assume this is rather a field of electronic engineering, by the way. In the Renewable energy field (2), for example, students are working on fluid flow simulations around wind turbines. And the geophysics such as the gravity survey for geothermal power generation (3) sounds unique to Kenya, because about half of Kenya’s electricity is generated by geothermal power generation.

In addition to the drone group, several graduate students from the Physics Department also participated
PCB to be attached to a drone for scientific observation
Explanation by faculty from the Department of Physics
A small drone is used

11. November 2022
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Ask advice from an expert: improving fiberglass manufacturing

Two events were scheduled for today. The first was a static test of the N-2 rocket motor. In the previous test, the nozzle could not withstand the pressure increase and popped out, so two improvements were made to the test: the groove depth was increased and the snap ring was doubled.

Members keeping their distance from the test apparatus.

As it turns out, today’s test was not conducted. The reason was that there was a problem with the igniter. Since we had not prepared a spare igniter, we had to conduct two tests including this motor in the next test.

In the afternoon, we invited a fiberglass expert to JKUAT to teach us how to fabricate fiberglass airframes. He had originally worked for vehicle industry, where he learned fiberglass manufacturing.

When we showed them the tools we were using, he gave us the following advice immediately.

  1. Use a Fiber cloth (for the outer layer) or Tissue mat (for the inner layer) instead of a Glass mat
  2. Use a 2-inch paintbrush instead of a roller
  3. Use epoxy resin instead of polyester resin
  4. Use mirror graze polish (looks like vaseline) when removing from the mold
  5. Use aluminum for body tube molds, not PVC resin
  6. Use gelcoat for the final layer

The students, who had been engaged in fiberglass production by trial and error, listened to the opinions of the professional.

Students receiving manufacturing instruction. A bucket of water is always prepared for emergencies.
First, apply the releasing agent to the mold
The hardener mixture should be varied depending on the layer. The inner layer should have less hardener (takes longer to cure), and as it gets closer to the final layer, more hardener (cures faster). Specifically, for the inner layer, use 1/4 capful of hardener to 350 ml of resin. In the final layer, use 1 capful per 350 ml of resin.
Remove air bubbles by pressing down with a brush. Work quickly.
Glass mat is made of two layers, like tissue paper, and can be separated into individual sheets. In the production of this body tube, the first layer was for one sheet, the second layer was for two sheets (full), and the third and final layer was for two sheets (full).

Today was also a day of progress for all teams, as the boards ordered from JLCPCB arrived.

Flight control team’s board
Avionics team’s board

11. November 2022
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