Which is a more stable lander design:

1.Single central engine.

2.Multiple engines located near the corners

Following is the design for Tianwen-1, the Chinese Mars lander:

enter image description here

And following is the design for InSight, the NASA Mars lander:

enter image description here

At the first glance it seems that a single engine design may be a little more unstable than the multi engine counterpart. I am confused about what is taken in to account for the placement of thrusters/engines...

What are the various parameters taken into consideration while designing the engine configuration/number for a lander (moon / Mars, taking atmosphere into account)?

  • 3
    $\begingroup$ Great question, not long ago I asked a question about Viking, which had 3 engines. $\endgroup$ Commented Jul 17, 2020 at 20:23
  • 1
    $\begingroup$ slightly related: What is the purpose and necessity of this giant structure being used in tests of China's Mars lander? $\endgroup$
    – uhoh
    Commented Jul 18, 2020 at 2:50
  • $\begingroup$ This is pure speculation, so I will not post as an answer: One engine is probably simpler, but with three, you can adjust the throttle on each to help steer. $\endgroup$ Commented Jul 18, 2020 at 21:30
  • 1
    $\begingroup$ There's several tradeoffs, it's more than just a matter of stability. With multiple separated engines, you need fast, precise throttling to keep things under control. This arrangement will be more suited for a squat and wide lander, with each engine pointing well away from the center of mass. With a single central engine (or a compact cluster for redundancy), you can't use differential thrust and need gimbaling instead. This arrangement is better suited for a tall lander with high center of gravity, but might still be used for a squat one due to not needing as precise throttle control. $\endgroup$ Commented Jul 19, 2020 at 1:29
  • 2
    $\begingroup$ I suspect also that multiple engines may be chosen to dissipate the exhaust as to not carve out the surface of the moon/planet. $\endgroup$
    – R. Hall
    Commented Nov 4, 2020 at 3:40


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