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In an emergency, is it possible to use the draco and super draco thrusters alone to slow down the vehicle after re-entry? Right from the point parachutes are supposed to be released right upto touch down on water or land. So basically if the parachutes fail(God forbid), are the thrusters capable of slowing down the vehicle after re-entry in Earth to safe touchdown?

Also is there protection for the draco and super draco thrusters from sea water?


Added later: Seems it could land: https://www.teslarati.com/spacex-crew-dragon-emergency-landing/?mc_cid=ec782f2549&mc_eid=0310f1b8f4

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It seems that someone on the /r/spacexlounge subreddit had the same question:

We know from the FAA filing for the pad abort that Dragon has a fuel capacity of 1388kg, and we know that it's max landing mass should be around 8.9 tonnes. If we round that up to 9 tonnes, and then plug in the specific impulse for SuperDraco of 235 seconds, we get a Delta-V of 330m/s2.

This is backed up by data from the pad abort. During the pad abort it reached a max altitude of 1.5km and traveled 2.2km downrange. Assuming no gravity or drag losses, that would require 183m/s2 of delta-v. Gravity losses would amount to an additional 49m/s2 given that the engines fired for 5 seconds.

If we then account for drag losses, and the fact that the abort burn ended prematurely with fuel still in the tanks, and the fact that it had to drag the trunk along with it, unlike during landing, then 300+m/s2 of Delta-V seems quite reasonable.

300 m/s^2 is all the delta-v that the Dragon can use to land. From the same post:

Terminal velocity of the Dragon capsule is somewhere in the region of 100m/s. I guesstimated 115m/s, which for a 3G landing burn would require 155m/s of Delta-V, coincidentally the max velocity during the pad abort was also about that much. But let's call it 200m/s2 to be safe.

In the right circumstances, the Crew Dragon COULD perform an emergency propulsive landing using the SuperDracos. I have no idea whether this has been programmed into an abort sequence, given that the capability of propulsive landings for Dragon V2 was publicly cancelled.

The Draco thrusters would likely not be used, given that they are designed for orbital maneuvers and attitude control, and thus would be far less efficient when operated in an atmosphere (as well as the poisonous fuel thing.)

As for your second question, I can't seem to find anything directly about it but I believe that both types of thrusters have water protection, given the capsule's propensity to land in it (and because they are meant to be re-used.)

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    $\begingroup$ I'm a little suspicious of their math since delta-v is a velocity but they're giving accelerations. $\endgroup$ – 2012rcampion Mar 3 at 22:34
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Using Super Dracos, yes.

Musk quotes from the thread:

Dragon 2 was designed to land using thrusters, with parachutes as backup. Switched to chutes as primary, due to difficulty of proving safety, but Dragon can still do it. https://t.co/Mr7VFIQwWf

...

For cargo missions, propulsive land landing should be no problem. Doesn’t have same safety criticality as crew.

Someone asked:

Are thrusters programmed as backup if chutes fail to deploy properly?

And Musk replied:

Most likely, but this is contingent upon NASA review & approval

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I can't place when he said this, but I remember, Musk was asked about this in some interview. He said it could land propulsivly, but it would be a hard landing because the landing gear that was originally planned is not there. He did not indicate if they had programmed that option into the return sequence. It sounded to me like a theoretical answer.

Obviously this could only happen in a return from orbit. If it were an aborted launch, the fuel would be used up in the escape.

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