35
$\begingroup$

If the entire event of EDL (Entry - Descent - Landing) is going to take only 7 minutes and if the command to begin could be signalled based on ground weather conditions, why was it necessary to take the extra effort to program the capability to land in dust storms?

Why not make use of dynamic weather monitoring and only initiate entry when the conditions are perfect?

Improve this question
$\endgroup$
0

3 Answers 3

Reset to default
89
$\begingroup$

Because it's at the end of a 6 month cruise and there's no turning back.

InSight will not enter closed orbit around Mars - its trajectory is hyperbolic so either it misses Mars entirely or it enters the atmosphere.

There were six planned course corrections during the cruise phase, the final one of which - TCM 6 - occurred on the day of the landing. This was to precisely target the landing site and would have made very little difference to the entry time - certainly not enough to wait out a dust storm.

Improve this answer
$\endgroup$
32
$\begingroup$

InSight doesn't enter Martian orbit before EDL; it plows straight into Mars' atmosphere from interplanetary space. Thus, the time of landing is pretty much un-alterable after its final midcourse correction maneuvers; it cannot wait for perfect weather conditions to land.

Improve this answer
$\endgroup$
0
8
$\begingroup$

To deal with dust storms, two of the changes between Phoenix and InSight are mechanical in nature:

  • InSight uses a thicker heat shield, partly to handle the possibility of being sandblasted by a dust storm.

  • InSight’s parachute suspension lines use stronger material.

https://mars.nasa.gov/insight/timeline/landing/entry-descent-landing/

The landing site needs to be both flat and level, and reconnaissance helped to choose the optimal site. Nonetheless, there still could be boulders or small hills that should be avoided. Therefore, there are cameras and radar that help the computer decide the best place for landing, and thrust appropriately. These cameras and radar can be blinded by dust storms.

Improve this answer
$\endgroup$
6
  • $\begingroup$ Are the suspension lines stronger than Phoenix's because of possible dust storms, or because Insight is a little heavier, and its parachute was deployed at mach 1.8 instead of mach 1.7? $\endgroup$
    – Wayne Conrad
    Commented Nov 26, 2018 at 20:34
  • 3
    $\begingroup$ @WayneConrad: All 3 reasons contributed to the design change. $\endgroup$
    – DrSheldon
    Commented Nov 26, 2018 at 20:36
  • 7
    $\begingroup$ +1 for the how, but it actually misses the question of why. $\endgroup$
    – DarkDust
    Commented Nov 26, 2018 at 20:59
  • 2
    $\begingroup$ @WayneConrad: The wind, not the dust itself. $\endgroup$
    – DrSheldon
    Commented Nov 27, 2018 at 14:09
  • 6
    $\begingroup$ No, that's not how wind works on flying objects. If there is potential wind shear during deployment, that could cause increased loads on the parachute. But high wind speeds alone will not. That's because, aerodynamically, the capsule is flying relative to the wind, not relative to the ground. $\endgroup$
    – Wayne Conrad
    Commented Nov 27, 2018 at 16:42

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.