This paper presents the topic of using solid rocket propulsion for de-orbiting spacecraft,in order to fulfil space debris mitigation requirements.The benefits and disadvantages of using such means are discussed.A dedi...This paper presents the topic of using solid rocket propulsion for de-orbiting spacecraft,in order to fulfil space debris mitigation requirements.The benefits and disadvantages of using such means are discussed.A dedicated system can be implemented in the satellite design phase and shall be a key subsystem of platforms inserted into orbit.Uncontrolled,semi-controlled and controlled de-orbit can be completed using solid rocket motors.Their impact on the space debris environment is discussed.Specific requirements for dedicated propellants and systems are provided.While the majority of presently developed rocket systems worldwide require high burn rates,several applications,including de-orbiting,benefit from solid propellants with decreased regression rates.This allows limiting spacecraft accelerations and loads during de-orbit manoeuvres.Moreover,the requirement of minimising solid particle generation is presented.Heritage technology from the Mercury and Gemini human spaceflight programmes,where de-orbit motors were used,is shown.Historical Soviet,American and Chinese film-return-capsule solid propellant retrorockets,enabling deorbit,are also presented.A detailed survey of current work worldwide on end-of-life disposal using solid propulsion is included.Challenges of developing dedicated systems are discussed.Finally,an outlook on solid rocket motor utilisation for space debris mitigation is provided.展开更多
Objective To investigate whether the osteocyte apoptosis exists in orbital bones and to discuss its effect on the orbital development. Methods Seven young Newzealand white rabbits were selected as experimental animals...Objective To investigate whether the osteocyte apoptosis exists in orbital bones and to discuss its effect on the orbital development. Methods Seven young Newzealand white rabbits were selected as experimental animals.At two-month-old ,all rabbits were killed and then zygomas were made into paraffin and electron microscope sections after they were decalcified. Apoptosis of osteocytes was observed by light microscope and transmission electron microscopes and detected by TUNEL staining. Results The classical apoptosis of osteocytes was found under light and transmission electron microscopes. Apoptosis of osteocytes was diffused irregularly in the zygomatic tissue. Conclusion Osteocyte can apoptosis and it may participate in the development of the bony orbit.展开更多
基金financed by the Polish National Agency for Academic Exchange(No.PPI/APM/2018/1/00032/U/001)Work presented from projects of ESA includes work done during preliminary phases of ASPro(Pre-Qualification of Aluminium-Free Solid Propellant)and SPRODEM(Solid Propellant De-orbit Motor Engineering Model Development)projects funded within the General Support Technology Programme(GSTP)。
文摘This paper presents the topic of using solid rocket propulsion for de-orbiting spacecraft,in order to fulfil space debris mitigation requirements.The benefits and disadvantages of using such means are discussed.A dedicated system can be implemented in the satellite design phase and shall be a key subsystem of platforms inserted into orbit.Uncontrolled,semi-controlled and controlled de-orbit can be completed using solid rocket motors.Their impact on the space debris environment is discussed.Specific requirements for dedicated propellants and systems are provided.While the majority of presently developed rocket systems worldwide require high burn rates,several applications,including de-orbiting,benefit from solid propellants with decreased regression rates.This allows limiting spacecraft accelerations and loads during de-orbit manoeuvres.Moreover,the requirement of minimising solid particle generation is presented.Heritage technology from the Mercury and Gemini human spaceflight programmes,where de-orbit motors were used,is shown.Historical Soviet,American and Chinese film-return-capsule solid propellant retrorockets,enabling deorbit,are also presented.A detailed survey of current work worldwide on end-of-life disposal using solid propulsion is included.Challenges of developing dedicated systems are discussed.Finally,an outlook on solid rocket motor utilisation for space debris mitigation is provided.
文摘Objective To investigate whether the osteocyte apoptosis exists in orbital bones and to discuss its effect on the orbital development. Methods Seven young Newzealand white rabbits were selected as experimental animals.At two-month-old ,all rabbits were killed and then zygomas were made into paraffin and electron microscope sections after they were decalcified. Apoptosis of osteocytes was observed by light microscope and transmission electron microscopes and detected by TUNEL staining. Results The classical apoptosis of osteocytes was found under light and transmission electron microscopes. Apoptosis of osteocytes was diffused irregularly in the zygomatic tissue. Conclusion Osteocyte can apoptosis and it may participate in the development of the bony orbit.
