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SpaceX - And why 10 minutes matter
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iMo:
The today's sequence is something I would always go with - as it is the safest. In case of fire or explosion the supporting personnel around the capsule would be lost otherwise..
legroeder2k:
I've found some more data about the DM-2 mission at https://everydayastronaut.com/dragon-2-dm-2-spacexs-first-crewed-mission/

One thing is the payload is announced there with 12055kg which I understand is the complete wet mass of the dragon capsule  - bringing it's available delta-v down to about 400m/s. (9525 kg dry + 1388 kg fuel + 1142kg capsule payload)

Another, way more interessting thing is the mission profile for Falcon 9 a bit down in the post. There Tim Dodd explains that for safety reasons the flight profile is really shallow to ensure a safe abort at any time.
Which makes my rough calculations worse because the transfer from a lower orbit to ISS needs more delta-v. Not talking about the plane change, as the orbital velocity is higher in lower orbits. Taking 180km and not 280km in the calcuations means for transfer they have to spent 127m/s and for the 2,5° inclination change i get 340m/s. Exceeding the 400m/s quite a bit.

And due to the fact that having a shallower trajectory also brings the issue of having to fight atmospheric drag for longer they really might not have enough fuel margin in the Falcon 9 to do much wiggling at all.
nfmax:

--- Quote from: imo on May 28, 2020, 03:35:27 pm ---The today's sequence is something I would always go with - as it is the safest. In case of fire or explosion the supporting personnel around the capsule would be lost otherwise..

--- End quote ---

Where the safety systems make use of nitrogen tetroxide & mono-methyl hydrazine, it must be pretty damn dangerous
iMo:
Sure, but the probability the hydrazine+N2O4 bailout engines/tanks explode (or leak) is lower than with the main LOX+kerosene tanks, imho..
PS: In a different thread I wondered why they do not use solid propellant bailout engines, but somebody argued the hydrazine engines are better suited (ie. used for orbital maneuvers too)..  :(
Domagoj T:

--- Quote from: imo on May 28, 2020, 04:19:16 pm ---PS: In a different thread I wondered why they do not use solid propellant bailout engines, but somebody argued the hydrazine engines are better suited (ie. used for orbital maneuvers too)..  :(

--- End quote ---
SuperDracos were designed to be multi purpose. They provide launch abort capability, but were also intended to be used for propulsive landings. NASA decided they didn't want crewed vehicles to use propulsive landing, but SuperDracos were presumably already part of the design so they stayed. We may still see them in that role in the future.
Since they are hydrazine engines, the added benefit is that they use the same propellant and oxidizer as the much smaller Draco engines which are used for orbital maneuvering, so in normal operation when you don't use launch abort procedure, you can still use that propellant. If you had solid motors, that would be dead mass for the entirety of mission. Also, being hypergolic engines, they can be restarted numerous times, and offer variable thrust and burn length capability, neither of which can be done with solid motors.

In a nominal mission, I don't think SuperDracos are used for orbital maneuvering. Their specific impulse is worse than Dracos, so the small guys do that part.
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