The downward propagating flame of NH₃/O₂/N₂ mixture in a top open combustion tube were captured by high speed cameras. In the propagation process the flame changes its shape and structures depending on the location of the flame. One of the critical moments of the flame is transition to the parametric instability, which shows a highly structured cellular pattern followed by steep growth of pressure perturbation called as combustion instability. The authors received the highest award in 2022 Beautiful Flame Photo Contest in 60^th Symposium (Japanese) on Combustion. The name of picture is "Chrysanthemum Flame" as shown in the right, which represents an instant of transition to the parametric instability of the propagating flame. In this paper the story behind the flame picture including method of photographing, theoretical background, and significance of the picture from the view of combustion science are described.

A story of making "August iris flower listening to the song of flame" were described. The photo is composed by two main components of a laminar diffusion flame array formed on a Rubens tube and dielectric barrier discharge (DBD) on iris flower. The different frequency of sinuous wave was applied to the speaker attached at the end of tube for controlling heights of the laminar diffusion flame array and the waveform appeared on the Rubens tube. The frequencies of sound wave varied from 400 Hz to 900 Hz. DBD on iris flower was achieved to express a situation that the flower is listening the songs of flames. Electrodes for the DBD were the iris flower itself and acrylic water tank. The frequency of DBD was set to 7 kHz and its applied voltage was set to 35 kV peak to peak. In the final product of the submission, the flame array was flipped vertically and arranged at the bottom. On the back of the flame array iris flower with DBD were placed to express the pose of listening to the sound of flame.

A detonation engine in space flight has been successfully demonstrated. This is the world's first successful demonstration of a detonation engine in space. The detonation engine system developed in this study was loaded onto the mission section of the sounding rocket S-520-31 and launched from the JAXA Uchinoura Space Center at 5:30 a.m. on July 27, 2021. After the separation of the first stage rocket, the rotating detonation engine and pulse detonation engine were successfully operated in space, and photo images, pressure, temperature, vibration, position, and attitude data were acquired by telemetry and RATS (Reentry and Recovery Module with Deployable Aeroshell Technology for Sounding Rocket Experiment). The fuel is methane and the oxidizer is oxygen. The detonation engine generates detonation and compression waves at extremely high frequencies (1-100 kHz) to drastically increase reaction speed, leading to radical reduction of rocket engine weights and high performance by easy generation of thrust. The success of this space flight demonstration will bring the detonation engine much closer to practical use as a kick motor for deep space exploration, and as a first and second stage engine for rockets.

This is a story of how to make "flamme de cocktail". The story includes not only science point of view, but literary flavor may include. Flamme de cocktail is a photo for one of the variations of combined flames using a dual nozzle burner. This short column also introduces how to make the work, the detail structures of dual nozzle burner, and variety of combine flames using the burner. Color printing available on J-STAGE. Author recommends refer to the color digital images for this paper.

Combustion phenomena are complex, beautiful, and interesting objects of observation. Michael Faraday, the great British experimental scientist of the 19th century, stated that the most effective tools when attempting to elucidate unknown phenomena are "experiments" and "observation". The author, who respects Michael Faraday, has been conducting research on flame extinction and fire extinguishments mainly through observation of phenomena. The author has often submitted interesting flame photographs obtained in the research with the help of Hirosaki University students to the "Beautiful Flames" photo contest. In the report, the author explains these works with the author's memories.

An overview of research on high-energetic ionic-liquid propellants (EILPs) in Japan to realize a green space propulsion system is reported in this paper. First, two kinds of propellant compositions consisting of ammonium dinitramide/monomethylamine nitrate/urea were selected as candidates as the compositions with sufficiently low melting temperature and higher propulsion performance than conventional hydrazine. For innovative combustion control methods to solve the problems of catalyst ignition, thermal and catalytic reaction characteristics were investigated, and laser heating ignition and electrolytic ignition were experimentally studied. The results show the feasibility of both laser heating ignition and electrolytic ignition and provide knowledge of the influences of several design parameters on the ignition characteristics.