Suppose that during the boost phase a Falcon 9 lost enough engines that it could not deploy its payload into a useful orbit or trajectory.

Are there some scenarios where it could conceivably return to Earth with it's presumably very expensive or valuable payload intact, rather than deploy into a useless orbit or put it in the ocean?

For the purposes of this question assume that there is both a downrange landing ship in the ocean and the pad on land is also available and ready. Also assume there is clearance from government agencies, the insurers, customer(s) etc, and that it's really worth it to bring this particular payload back rather than scrap it and build another.

One abstracted, hypothetical example might be that the payload is "the last RTG on Earth" because there's no current replacement supply for any feasible radioisotope source.

Also assume that the rocket has sufficient programming to recalculate this dramatically different trajectory.

If everyone is "on board" with this, is it possible? Are there any show-stoppers for the current Falcon-9? Below about 110 km the fairing should still be intact, but would that even be necessary?

  • $\begingroup$ The barge would have to be repositioned because the stage is going to be landing in a different location, and it's not fast enough to do that. $\endgroup$ – Hobbes Nov 22 '17 at 16:30
  • $\begingroup$ Yikes, exact duplicate! OK let's close it. $\endgroup$ – uhoh Nov 23 '17 at 0:03


The upper stage, full of fuel, with a payload on top of it, is heavier than the entire first stage it would be incredibly top heavy, significantly longer and worse all the weight at the far end of the pendulum that it could never control the stack to land.

SpaceFlight Insider has the empty masses as:

First Stage Dry Mass = 25,600kg Second Stage Dry Mass = 3,900KG Second Stage Prop Mass = 92,670KG

So a second stage, ignoring payload and fairing mass, is close to 4 times the mass of the entire empty first stage.

While attached to the first stage, you could not vent the fuel, which takes about 8 minutes when using the engines main turbo pumps, to dump the fuel by burning it up. Hard to imagine a faster way to vent the fuel in the case of a rocket.

  • $\begingroup$ Even very top heavy might not be a problem when under power, but if it were returning down without engines it would really want to flip and would break. $\endgroup$ – jkavalik Nov 22 '17 at 17:47
  • $\begingroup$ The engines offer some control, but with a full second stage I highly doubt there is enough control authority to manage the entire stack. This would be hugely out of balance. The engines are no where near the mass of the second stage mass. $\endgroup$ – geoffc Nov 22 '17 at 18:22
  • $\begingroup$ @geoffc Since this question will be closed as duplicate (i've voted to close as well), what is the utility of re-writing your answer there again here? Isn't it better to allow it to point back to your longer version of the same answer there? By posting your duplicate answer, it blocks me from just deleting the question. If there is something new here, wouldn't it be better to move that to the longer answer? $\endgroup$ – uhoh Nov 23 '17 at 0:06

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