我們開發出了一種使用固態金屬作為推進劑的新型態離子推進器:磁控電子束轟擊金屬離子推進器Metallic Ion Thruster using Magnetron E-beam Bombardment (MIT-MEB)。不同於使用惰性氣體作為推進劑的經典離子推進器/電漿推進器，MIT-MEB使用固體金屬作為推進劑，因此有儲存密度高、成本低廉、易於儲存、安全等優點。可以使用任何導體作為推進劑。而元素週期表上有八成是金屬，因此相較傳統離子推進器而言，MIT-MEB在材料選擇上有絕對的優勢。本設計分為三個部分：金屬離子產生器和離子加速器以及中和器。首先自由電子從熱燈絲發射並被電場加速衝向金屬靶，使得金屬被加熱並蒸發。而金屬靶表面和燈絲之間具有約0.2~0.3T的磁場用於聚焦電子，當金屬蒸氣通過被磁場侷限而形成的高密度的電子雲時，會被其中的高能電子碰撞並游離。金屬被游離成離子後會被電場加速並排出裝置，而外部的中和器則釋放電子並與離子一同離開推進器。推進器最終排出等量的高速離子與電子藉以保持裝置的電中性。由於電子束工作條件與真空條件無關，因此可在超高真空環境中運作。我們已經製作並測試了原型機，通過電子束轟擊將金屬靶加熱至超過415℃。在5 kV/3 mA和1 kV/15 mA的電子束電流轟擊下，使用鋅片作為測試靶材，測得其質量流率為（2.2±0.4)E-4（g/s）與（1.8±0.3)E-5（g/s），游離率為0.03±0.01 ％和1.1±0.3 ％。因此，離子貢獻之推進力理論值分別為9.0±1.0 μN和10.3±0.7 μN，總功率約為25 W左右。比衝Isp理論值分別為12300 s和5500 s。若考慮未游離之蒸氣的貢獻，則總推進力分別為99±40 μN 和 17.3±4.0 μN.

The electric thruster is a device that uses electromagnetic fields to control and accelerate ions. An ion thruster using a metallic target as the propellant has been developed. Different from the inert gas used in conventional plasma thrusters, the metallic target is in the solid state, high density, easy to be stored and cheap. The design is divided into three parts: a metallic evaporator and an ion accelerator and a neutralizer. The principle of electron-beam (E-beam) evaporation, where a metal target is evaporated and ionized by thermal-emitted electrons, is used. The working condition is independent of the vacuum condition so that it works in the ultra-high vacuum space. A focusing magnet with a magnetic field about 0.2~0.3 T between the target surface and the filament is used to guide electrons toward the center of the target so that the metal is evaporated and ionized. A prototype has been built and tested. The metallic targets were heated to more than 415 °C by electron bombardment. A mass flow rate of (2.2±0.4)E-4 (g/s) and (1.8±0.3)E-5 (g/s) using Zn at 5 kV/3 mA and 1 kV/ 15mA E-beam current was measured. An ionization rate of 0.03±0.01 % and 1.1±0.3 % using Zn at 5 kV and 1 kV E-beam current was measured. Therefore, the estimated thrust is 9.0±1.0 μN and 10.3±0.7 μN with a power of about 25 W. The Estimated Isp is 12,300 s and 5,500 s respectively. Considering the contribution of vapors, the total thrust is 99±40 μN and 17.3±4.0 μN respectively.

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