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Why is SpaceX choosing to land the booster on the Mechazilla arms instead of performing a soft ground landing like the Falcon 9 booster?
by kedv 2y ago
Why is SpaceX choosing to land the booster on the Mechazilla arms instead of performing a soft ground landing like the Falcon 9 booster?
- syncsynchalt 2y ago1) legs are heavy 2) empty rockets are stronger in tension than compression the scale of Superheavy is such that the above two items are making the arms scheme make sense. The number of engines also gives this rocket the ability to hover, which probably makes the scheme easier to pull off.
- anymouse123456 2y agoIt's my understanding that these engines can be driven with variable power, which also makes deceleration and controlled hover more feasible.
- syncsynchalt 2y agoThis was also true for this engine's predecessor, the Merlin 1D. However that engine's rocket (the Falcon 9) can't hover, as the power of a single engine throttled to its lowest setting still overcomes the weight of a nearly-empty booster. All high performance engines tend to only throttle in a range in the upper half of the engine's performance, the difference making hovering possible in this case is that the Super Heavy has _so many_ engines that it can turn off. This is a sort of secondary throttling, or meta-throttling, and the rocket can use the combination of engine throttling and engine-off to hover comfortably (while near-empty) with three engines going.
- anymouse123456 2y agoThanks for the clarification!
- askvictor 2y ago> 2) empty rockets are stronger in tension than compression True, but wouldn't the deceleration burn be putting much more compression onto the near-empty rocket than the landing?
- asdfadsfgfdda 2y agoThe engine load is probably a steady, consistent magnitude. While a landing load is rapid and variable. Also, you need to design legs for wind loading after landing, which can be high if you want to launch often.
- jve 2y ago3) rapid reuse by landing on launch tower
- avmich 2y agoSpent rocket stages are empty of fuel, but not necessarily of the ullage gases, the pressure inside could be e.g. 3 atmospheres and that could be enough to provide some stiffness in the direction perpendicular to the axis.