**Author details**

these design constraints intersect with the theoretical corridor width, there also exists a minimum vehicle L/D for a successful aerocapture. As the constraints become more restrictive (in other words, allowable peak g-load and peak heat rate are reduced), the requirement for vehicle L/D will increase whereas the maximum

The difference between **Figures 11** and **12** is the ballistic coefficients. By comparing the two plots, we note that a higher ballistic coefficient results in similar theoretical corridor width (i.e., vehicle control authority), similar peak g-load, but much higher peak heat rate and total heat load. **Figure 11** can be regarded for robotic missions or small satellite missions whereas **Figure 12** for human Mars

**Figure 11** shows that the peak heat rate and total heat load are very benign. Even

within the TPS material limits. At lower *V*∞, we can even use non-ablative TPS materials such as the tiles used on Space Shuttles as listed in **Table 3**. In terms of peak g-load, robotic missions can usually tolerate a higher g-load than for human missions. The Galileo probe that entered Jupiter's atmosphere was designed to withstand over 200 Earth g's. As a result, in the range of arrival *V*<sup>∞</sup> considered, the

For human Mars missions, as shown in **Figure 12**, the peak heat rates are still well within the current TPS materials. As with higher *V*<sup>∞</sup> values, peak heat rate can

dling such heat rate. Note that HEEET is an ablative TPS material, which means that it will be difficult to reuse because of the loss of materials. For the purpose of getting humans to Mars, a non-ablative TPS material will be ideal for repeated aerocapture maneuvers. Considering a theoretical corridor width of 2 deg., with a mid-L/D

than what the shuttle tile can handle. Assuming a non-ablative TPS material can sustain 75 W/cm<sup>2</sup> peak heat rate; then, in **Figure 12**, the area above the contour line of 2 deg. and left of 75 W/cm<sup>2</sup> line is the feasible region for aerocapture, which requires a very low arrival *V*<sup>∞</sup> of less than 1.5 km/s. In terms of the g-load constraints for human missions, within the areas found, a peak g-load of 2 Earth g's is a very benign condition. It is important to note again, that the worst-case scenarios are shown, and with guidance and control, optimal trajectories can often reduce the

In this chapter, a high-level assessment of aerocapture, aerobraking, and entry for robotic and human mission is presented. A comprehensive parametric analysis for all three maneuvers has been investigated while considering the key design parameters. Vehicle aerodynamic properties are key drivers in the performance of these maneuvers. Entry velocities also affect greatly the design parameters. From the results, aerocapture, aerobraking, and entry can be successful for robotic missions, whereas for human Mars missions, there are still challenges that need to be addressed. The challenges are directly related to the risks of the mission, and for human missions, safety is usually the top priority and strategies to mitigate the risk, that is, addressing the challenges will significantly reduce the risk to ensure mission

vehicle (L/D of 0.6–0.8), the peak heat rate will be around 75 W/cm2

, which is well

, HEEET is capable of han-

, which is more

allowable arrival *V*<sup>∞</sup> will decrease.

*Mars Exploration - A Step Forward*

g-load constraints are not too restrictive.

be more challenging. However at around 2000 W/cm<sup>2</sup>

missions.

peak conditions.

**6. Conclusions**

success.

**48**

**5.2 Aerocapture for robotic and human missions**

at *V*<sup>∞</sup> of 9 km/s, the peak heat rates are only around 250 W/cm<sup>2</sup>

Ye Lu Kent State University, Kent, OH, United States

\*Address all correspondence to: ylu16@kent.edu

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
