Hiroto HABU

To get better information about thermal stability of ammonium dinitramide (ADN), this study discussed about thermal decomposition mechanism, decomposition kinetics, and influence of aging on thermal decomposition of ADN using thermal analyses and evolved gas analyses. From the results of evolved gas analyses about ADN, it was found that thermal decomposition of ADN has three stages depending on temperature. The reaction at low temperature side was the decomposition of a part of dinitramic acid from ADN dissociation. At high temperature side, 2 stages of reaction with gas generation were occurred. First reaction is thought to bedecomposition of dinitramic acid. The reaction mode is different from that at low temperature side. Second one is thought to be the reaction of decomposition products of ADN. Kinetic analyses of ADN decomposition and lifetime prediction were carried out using the results of SC-DSC scanning tests and TAM isothermal tests. The results of kinetic analysis from TAM tests showed lower activation energy, and closer decomposition amount to real time storage than that from SC-DSC scanning tests. Non-isothermal tests may not be able to precisely predict the lifetime of materials whose decomposition mechanism changes with temperature, such as ADN. From the results of evolved gas analyses about ADN and AN (aging product of ADN) mixture, the exotherm and gas generation at low temperature side could not be observed. Nitric acid from AN dissociation is weaker acid than dinitramic acid. Thus, HN(NO_2)_2 decomposition at low temperature side was inhibited when acid level in the system was reduced.

In this research we obtained ignition delay time, chemical ignition delay time, and activation energy of the Ammonium dinitramide (ADN) / Ammonium nitrate (AN) composite propellants. In the results ignition delay time and chemical ignition delay time decrease with increasing atmosphere temperature and increasing concentration of ADN. Activation energy of ADN/AN composite propellant decrease at concentration of ADN between 40 [mass%] and 60 [mass%]. It is consider that reaction of ADN/AN propellant is changed by increasing concentration of AN.

Ammonium nitrate (AN) surface was coa ted with moisture prevention layer by the atmospheric pressure glow (APG) plasma deposition to use A N as an oxidizer of composite solid propellants. The hygroscopic property of AN was examined via mass increase of AN powder in a constant temperature and humidity oven. Although the AN treated hexafluoropropene (HFP) / He APG plasma showed no improvement in the moisture-proof property at 70%RH (35oC), it showed perfect moisture-proof property at 50%RH (35oC).

本研究会の研究対象である固体酸化剤粒子は,その特性上,電子顕微鏡観察環境下において強い電子線を照射すると分解しガス化するため,高倍率での表面観察は困難であった.また,本研究会の目的のひとつである薄膜コーティングを施した粒子の場合,表面帯電を逃がす目的で被観察物に施す金属蒸着も良好な観察を妨げる要因であった.今回,低い電子線加速電圧において良好な分解能を得られる極低加速電圧SEM を用いて対象物を観察したところ,良好な観察結果を得たためここに報告する.

Lithium ejection system (LES) is one of the chemical payloads for the ionosphere observation. Lithium is selected as the chemical tracer to detect optically the neutral winds, and the thermite loaded in LES played a role of the heat sauce to vaporize the solid phase lithium. This device has been launched by the Japanese sounding rocket, S-520, from Uchinoura space center in 2007. Gaseous lithium was successfully injected into the space, and the red colored cloud was able to be observed from the ground. The concept was explained in early papers, and their design was shown that the thermite including lithium or sodium pellets was directly charged in the canister. Thermite is ignited by the pyrotechnics and generates the high temperature chemical products which give the vaporization energy of the released materials. The payload design was considered that the instruments on board which acts by the pyrotechnics need to be equipped with the safe and arm device (SAD) from the safety standard. The final design obtained the safety and the reliability of this device for storing and handling. Lithium in the canister is able to be removed with ease, and the tracer materials will be able to replace lithium to other one if necessary. 13 LES canisters were fabricated for ISAS-NASA international collaborative space science mission. This paper reports the results of the design study and the specification of LES.

A nitrous oxide (N2O)/ ethanol propulsion system is distinguished as the liquid propulsion with non-toxic, user-friendly, and storable bipropellant. The current target of the present study is to build a quickresponse and maneuverable main engine of a sounding-rocket like flying test bed which will be applied to the hypersonic air-breathing propulsion researches in the near future. The application to the spacecraft propulsion is also considered due to its compatibility in low-temperature operation environment. Two series of static firing tests were performed with 700 N class gas generator models so far. Current test results showed that valuable design data were collected and operational procedure was verified. Potential of application of composite materials to the combustion chamber was also examined from the chamber wall heat flux data obtained and the result of firing test using a thick SFRP chamber.

資料番号: SA0200131000