The interaction of relativistic spacecrafts with the interstellar medium (1608.05284v2)

Abstract: The Breakthrough Starshot initiative aims to launch a gram-scale spacecraft to a speed of $v\sim 0.2$c, 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. 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 $\sim 0.1$ mm for quartz material after traversing a gas column of $N_{\rm H}\sim 2\times 10^{18}\rm cm^{-2}$ 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 $v=0.2c$, we find that dust bombardment can erode a surface layer of $\sim 0.5$ mm thickness after the spacecraft has swept a column density of $N_{\rm H}\sim 3\times 10^{17}\rm cm^{-2}$, assuming the standard gas-to-dust ratio of the interstellar medium. 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.

Interaction of Relativistic Spacecrafts with the Interstellar Medium

The paper "The Interaction of relativistic spacecrafts with the interstellar medium" offers a thorough examination of the potential damage a relativistic spacecraft might encounter on its journey through the interstellar medium. This paper specifically analyzes gram-scale spacecraft, envisaged by the Breakthrough Starshot initiative, which aims to achieve velocities of up to 0.2c, allowing the spacecraft to reach alpha Centauri within a span of approximately 20 years.

The paper centers around the interaction dynamics between a spacecraft and interstellar gas and dust. Two principal materials, quartz and graphite, are assessed for their structural integrity when exposed to these interplanetary adversities. The authors quantify the extent of damage caused by collisions with gas atoms, particularly emphasizing energy deposition resulting in damage tracks. These tracks alter the material structure by forming permanent linear defects, primarily due to massive ions like iron.

One of the crucial findings is the disparity in damage susceptibility between quartz and graphite. Quartz is considerably more affected by heavy ions, suffering damage to depths of up to 0.1 mm after traversing certain gas columns. Graphite, owing to its higher thermal conductivity, manages to resist damage for speeds exceeding 0.15c due to its ability to rapidly distribute the deposited energy.

On the other hand, dust bombardment introduces another layer of complexity. Relativistic speeds amplify the dust's destructive capacity, leading to surface erosion through crater formation caused by explosive evaporation. The paper delineates the crater formation process, explores the modification in material structure due to melting, and predicts a substantial erosion depth of about 0.5 mm at 0.2c across a specific gas column density range.

The analysis extends to assess the equilibrium temperature of the spacecraft, a critical factor stemming from collisional heating by interstellar gas atoms (primarily H and He). The paper posits that, within typical interstellar medium conditions, spacecraft heating is unlikely to reach melting points unless interacting with dense clumps, thus averting structural damage from this heating source.

Furthermore, the investigation evaluates scenarios under which large interstellar dust grains might invoke total spacecraft destruction. Although calculated chances are minimal, the necessity to account for big grain collisions is emphasized. This prompts the exploration of protective measures such as employing highly conductive shield layers and specific spacecraft configurations to mitigate the risks stemming from dust collisions.

Overall, this paper lays foundational insights into spacecraft material resilience, potential damage mitigation strategies, and the interplay between relativistic motion and interstellar constituent interactions. It underscores the importance of protective shielding and design optimizations to advance space exploration technology feasibly. As spacecraft design evolves, integrating these considerations will be pivotal to safeguarding sensitive electronic components against the unyielding consequences of relativistic journeys through space.