http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Electromagnetic Forces on a Relativistic Spacecraft in the Interstellar Medium
Hoang, Thiem,Loeb, Abraham American Astronomical Society 2017 The Astrophysical journal Vol.848 No.1
<P>A relativistic spacecraft of the type envisioned by the Breakthrough Starshot initiative will inevitably become charged through collisions with interstellar particles and UV photons. Interstellar magnetic fields would therefore deflect the trajectory of the spacecraft. We calculate the expected deflection for typical interstellar conditions. We also find that the charge distribution of the spacecraft is asymmetric, producing an electric dipole moment. The interaction between the moving electric dipole and the interstellar magnetic field is found to produce a large torque, which can result in fast oscillation of the spacecraft around the axis perpendicular to the direction of motion, with a period of similar to 0.5 hr. We then study the spacecraft rotation arising from impulsive torques by dust bombardment. Finally, we discuss the effect of the spacecraft rotation and suggest several methods to mitigate it.</P>
The Interaction of Relativistic Spacecrafts with the Interstellar Medium
Hoang, Thiem,Lazarian, A.,Burkhart, Blakesley,Loeb, Abraham American Astronomical Society 2017 The Astrophysical journal Vol.837 No.1
<P>The Breakthrough Starshot initiative aims to launch a gram-scale spacecraft to a speed of nu similar to 0.2c, capable of reaching the nearest star system, alpha Centauri, in about 20 years. However, a critical challenge for the initiative is the damage to the spacecraft by interstellar gas and dust during the journey. In this paper, we quantify the interaction of a relativistic spacecraft with gas and dust in the interstellar medium (ISM). For gas bombardment, we find that damage by track formation due to heavy elements is an important effect. We find that gas bombardment can potentially damage the surface of the spacecraft to a depth of similar to 0.1 mm for quartz material after traversing a gas column of N-H similar to 2 x 10(18) cm(-2) along the path to alpha Centauri, whereas the effect is much weaker for graphite material. The effect of dust bombardment erodes the spacecraft surface and produces numerous craters due to explosive evaporation of surface atoms. For a spacecraft speed nu = 0.2c, we find that dust bombardment can erode a surface layer of similar to 0.5 mm thickness after the spacecraft has swept a column density of N-H similar to 3 x 10(17) cm(-2) assuming the standard gas-to-dust ratio of the ISM. Dust bombardment also damages the spacecraft surface by modifying the material structure through melting. We calculate the equilibrium surface temperature due to collisional heating by gas atoms as well as the temperature profile as a function of depth into the spacecraft. Our quantitative results suggest methods for damage control, and we highlight possibilities for shielding strategies and protection of the spacecraft.</P>