3
$\begingroup$

During the SpaceX'S Crew Dragon In Flight Abort Test on a Falcon 9 Launch System, as soon as the abort system was triggered Falcon 9 booster engines was shut down and crew dragon's super dracos ignited and pulled it out to safety.

What if the booster engines did not shut down? Would the super dracos have the TWR to pull the capsule to safety especially at later stages of flight?

$\endgroup$
2
  • $\begingroup$ From space.stackexchange.com/questions/14775/…, it seems the F9 peak acceleration is above 2G. An article in 2020 on Spaceflight Now says the peak acceleration of an abort test was 3.3G. (Not enough for a full answer, but a start, at least. I.e., how much would the F9 1st stage accelerate if it no longer has a payload? Is there ever a case where the 1st stage might overtake an aborted payload?) $\endgroup$
    – Ghedipunk
    Jun 14, 2022 at 16:15
  • $\begingroup$ I thought AFTS would kick in and blow up the rocket, but maybe not... $\endgroup$ Jun 16, 2022 at 20:53

1 Answer 1

5
$\begingroup$

The abort system in the Falcon 9 removes the payload (Crew Dragon) from the second stage using the Super Draco engines. The second stage remains attached to the first stage. Mass of the fully loaded second stage is around 100 tonnes, while the mass of the Crew Dragon is around 12 tonnes (https://www.spaceflightinsider.com/hangar/falcon-9/). As noted in @Ghedipunk's comment, the Super Dracos accelerate the Crew Dragon at around 3.3Gs, while the max acceleration of the first stage is only 2G (which isn't going to be impacted much by the loss of 10% of the mass during abort).

So, there is very little chance the whole first stage will overtake the Crew Dragon on an abort. The bigger issue is a RUD in the first stage, which can significantly accelerate debris in all sorts of directions - something you can't completely mitigate and is an issue for all Human Spaceflight.

$\endgroup$
3
  • $\begingroup$ What about the time at MECO, where booster acceleration is the highest? $\endgroup$
    – Ashvin
    Jun 15, 2022 at 8:31
  • 2
    $\begingroup$ As I noted, the maximum acceleration of the booster is 2G. It loses 10% of its mass when the Crew Dragon aborts, so theoretically could jump to 2.2G (a = F/m). Super Dracos pull the capsule away at 3.3G, which is much greater than 2.2G. $\endgroup$
    – throx
    Jun 15, 2022 at 22:12
  • 2
    $\begingroup$ Note that the maximum acceleration is only 2g because SpaceX specifically limits it to 2g for crew flights. If there were some kind of malfunction, it is not inconceivable that this limiting might not work and the acceleration might be higher. I still believe the SuperDracos are "faster", though, after all, that's literally their one job they are designed for: outrun the rocket. $\endgroup$ Jun 16, 2022 at 8:15

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.