Chapter 4, Problem 70P

After parachuting through the Martian atmosphere, the Mars Science Laboratory executed a complex series of maneuvers that successfully placed the rover Curiosity on the surface of Mars in 2012. The final ∼22s of the landing involved, in this order, firing rockets (1) to maintain a constant downward velocity of 32 m/s. (2) to achieve a constant deceleration that brought the downward speed to 0.75 m/s, and (3) to hold that constant velocity while the rover was lowered on cables from the rest of the spacecraft (see this chapter’s opening image). The rover’s touchdown was indicated by a sudden decrease in the rocket thrust needed to maintain constant velocity. Figure 4.28 shows the rocket thrust (upward force) as a function of time during these final 22 s of the flight and the first few seconds after touchdown. (a) Identify the two constant-velocity phases, the constant-deceleration phase, and the post-touchdown phase. (b) Find the magnitude of the spacecraft’s acceleration during the constant-deceleration phase. Finally, determine (c) the mass of the so-called powered descent vehicle (PDF), meaning the spacecraft with the rover attached and (d) the mass of the rover alone. Remember that all this happened at Mars, so you’ll need to consult Appendix E.

FIGURE 4.28 Rocket thrust (upward force of rocket engines) during the final descent of the Mars rover Curiosity (Problem 70).