竹内 伸介

A detonation engine system is successfully demonstrated for the first time in space using sounding rocket S-520-31 of the Japan Aerospace Exploration Agency/Institute of Space Astronautical Science. Detailed flight results of an S-shaped pulse detonation engine (PDE) installed in the rocket are presented herein. The flight is conducted to confirm that the PDE and its system operate at scheduled sequences in space, confirm the reproducibility of the PDE cycle, and despin the rocket around its axis. It is confirmed that the PDE operated successfully for 14 cycles in space. The experimental plateau pressure of 2.0 0.1 MPais 80 3% of the calculated plateau pressure, which suggests that detonation occurred in 14 cycles. The pressure profiles of the cycles are similar, and the pressure integrals are 2.0 0.1 kN⋅ s∕m2, confirming the excellent reproducibility of the PDE cycle. A probability statistical approach assuming a Gaussian distribution is applied to determine the average angular acceleration difference between processes of the PDE operation, mixture supply, and oxygen supply. The results suggested that the PDE despun the rocket via the thrust produced via detonation combustion, which is consistent with a quasi-steady-state model with an accuracy of 101 15%.

To create a new flyable detonation propulsion system, a detonation engine system (DES) that can be stowed in sounding rocket S-520-31 has been developed. This paper focused on the first flight demonstration in the space environment of a DES-integrated rotating detonation engine (RDE) using S-520-31. The flight result was compared with ground-test data to validate its performance. In the flight experiment, the stable combustion of the annulus RDE with a plug-shaped inner nozzle was observed by onboard digital and analog cameras. With a time-averaged mass flow of 182 11 g∕s and an equivalence ratio of 1.2 0.2, the RDE generated a time-averaged thrust of 518 N and a specific impulse of 290 18 s, which is almost identical to the ideal value of constant pressure combustion. Due to the RDE combustion, the angular velocity increased by 5.7 deg ∕s in total, and the time-averaged torque from the rotational component of the exhaust during 6 s of operation was 0.26 N ⋅ m. The high-frequency sampling data identified the detonation frequency during the recorded time as 20 kHz in the flight, which was confirmed by the DES ground test through high-frequency sampling data analysis and high-speed video imaging.

2021年7月27日早朝5：30，JAXA内之浦宇宙空間観測所からデトネーションエンジンシステムを搭載した観測ロケットS-520-31号機が打ち上げられた．高度約200kmにてメタン–酸素推進剤による回転デトネーションエンジン（RDE）の6秒間作動およびパルスデトネーションエンジン（PDE）の2Hz作動を実施した．取得されたフライトデータから，RDE作動で時間平均推力518N，比推力290±18sおよび速度増速量8.0m/sを達成した．PDE作動では1サイクル当たりの圧力時間積分値が5％以内の高精度での繰り返しインパルス生成およびロケット機軸周りのスピンレート減少が確認された．本結果は，地上燃焼試験データとよく一致し，宇宙空間でのデトネーションエンジン作動が実証された．デトネーション波の判定に用いた圧力・加速度センサの高速サンプリングデータおよびRDEプルーム撮影用のデジタルカメラ画像は，JAXA/ISASで開発された再突入データ回収システムRATSにて回収することに成功した．