JF Mezei wrote on Tue, 30 Apr 2019
15:39:51 -0400:

On 2019-04-30 14:10, Jeff Findley wrote:

I'm pretty sure they're totally independent. The pairs of SuperDracos
are fully independent from each other.

I believe this is correct. It gives the system some redundancy to have
these separate.


Considering current role of Super Dracos as being potentially useful
only during launch, and hopefully never used, wouldn't it make more
sense for them to share the weight of fuel with the dracos?


No, it wouldn't because now you have all the issues of adjusting for
different chamber pressures, etc.


aka: if all goes well at launch, the fuel is used by dracos during
on-orbit operations. And if Super Dracos is used during launch, you're
not going to need the fuel for dracos isn't you're not going to orbit.


Except that wasn't the way the thing was designed. I suspect SpaceX
is better at doing "the sensible thing" than you are when it comes to
their spacecraft.


I could understand separate fuel tanks in a context where the Super
Dracos would be used for every landing. (if fuel not used for launch
abort, it is then needed for normal landing and vice versa).


I suspect your 'understanding' is the least of SpaceX's concerns.


Were powered landings ruled out during Dragon 1 such that Dragon2 design
started off with powered landings already out of equation, or did they
start designing it for powered landings and then it was ruled out ?


Dragon I didn't have SuperDraco engines so it was never going to do a
propulsive landing. Propulsive landings were ruled out quite late for
Crew Dragon and the cargo variant of that craft might well still do
them someday since that doesn't raise the safety certification
concerns that eventually killed them for Crew Dragon.

They didn't "start designing it for powered landings". They also
FINISHED designing it for powered landings and built the thing that
way (with the exception of removing the landing legs, which Musk says
they could still put back with little to no difficulty). This stuff
is NOT hard to find out. You could, just occasionally, look things up
for yourself.

https://spaceflightnow.com/2017/07/1...gon-spaceship/

https://www.inverse.com/article/3440...hrust-landings

https://www.teslarati.com/spacex-cre...gency-landing/

I could go on...


--
"Ignorance is preferable to error, and he is less remote from the
truth who believes nothing than he who believes what is wrong."
-- Thomas Jefferson