The citation for the wikipedia page (240s ISP) gives an exhaust velocity of 2,300m/s :
https://en.wikipedia.org/wiki/SuperDraco#cite_note-DragonFly... - page 12 of the PDF.
So taking a rough 2300/9.8 gives about 235s
https://en.wikipedia.org/wiki/SuperDraco#cite_note-DragonFly... - page 12 of the PDF.
So taking a rough 2300/9.8 gives about 235s
So while I do not doubt that the numbers for that vehicle and that test are accurate, I keep hoping to find actual data from SpaceX on the performance of the production rocket slated for use in the production Dragon Module.
I understand that SpaceX plays this information close to its vest given the competition with Boeing for Commercial Crew and perhaps Blue Origin should SpaceX ever decide to sell rockets for sub orbital tourist jaunts[1]. Anyway I'm just interested in more official specs so that I can have more confidence in my understanding of their capabilities.
[1] If you think about it, they have all the hardware, an F9r with a Dragon Crew mounted on top, they boost up to 100km, separate, the Dragon gets a nice ballistic arc for that weightless feeling and then both the booster and the capsule go back and land back at the pad for re-use.
It looks like you're doing this calculation:
Isp * Gravity / Gravity
If you're trying to predict the hover duration, that will depend on the delta V of the vehicle. Then, a hover duration would be:
Delta v / Gravity
Not sure what the expected delta V is for the Dragon though.