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Erin Anne
Erin Anne
00:02
De Laval nozzle
A de Laval nozzle (or convergent-divergent nozzle, CD nozzle or con-di nozzle) is a tube which is pinched in the middle, making a carefully balanced, asymmetric hourglass shape. It is used to accelerate a compressible fluid to supersonic speeds in the axial (thrust) direction, by converting the thermal energy of the flow into kinetic energy. De Laval nozzles are widely used in some types of steam turbines and rocket engine nozzles. It also sees use in supersonic jet engines. Similar flow properties have been applied to jet streams within astrophysics. == History == Giovanni Battista Ven...
TheMatrix Equation-balance
TheMatrix Equation-balance
Cool. Interesting concept. But, back to humans. How would you open (accelerate) someone's mind? Role model, Art, Desperation and pain?
Erin Anne
Erin Anne
searching for it on Space SE may have been illuminating
ah, but that was the whole point of the metaphor! opening isn't accelerating
being selectively open is a useful adaptation
TheMatrix Equation-balance
TheMatrix Equation-balance
Interesting. I think I understand now. Freedom of mind can diffuse your thoughts. But narrow circumstances can critically focus your mind.
@fyrepenguin - you are correct. I was talking about the Starship's dry mass plus cargo.
 
6 hours later…
Vorac
Vorac
06:37
@ErinAnne Thanks! The linked question is not useful to me because "Riding a bike during EVA would be a very different proposition, and I will not comment on it." The first page of questions on that tag is even further removed from my intent. Should I ask a regular question?
Erin Anne
Erin Anne
06:57
that's what the site is for, though I'd lay out explicitly what you want answered that isn't answered in the existing questions about bikes
 
14 hours later…
TheMatrix Equation-balance
TheMatrix Equation-balance
20:41
user image
They say that reporting (on engines) was incorrect because an engine cannot be restarted inflight (after shutdown).
 
2 hours later…
TheMatrix Equation-balance
TheMatrix Equation-balance
22:42
6 engines out, some of the other engines working at 70% capacity or less . Maybe there is still hope for this Super Heavy.
Erin Anne
Erin Anne
who says? where do they say it
fyrepenguin
fyrepenguin
@TheMatrixEquation-balance Why “maybe”? The program seems to be going successfully enough
@TheMatrixEquation-balance well, they certainly are supposed to be able to relight twice when not on the pad, so I don’t know what you mean by not being restarted in flight
TheMatrix Equation-balance
TheMatrix Equation-balance
Terran Space Academy - youtube.com/watch?v=13KtGfpZtDw ("Exterior engines cannot restart..."
Erin Anne
Erin Anne
oh, a Youtube channel I've never heard of. Good to know!
fyrepenguin
fyrepenguin
It’s plausible that re-light capability is not on all engines. Would be good to have a proper source for that
Erin Anne
Erin Anne
22:53
yeah. On the one hand, not all the engines need to relight (though I don't know if I've ever heard how many engines are supposed to be used for boostback). On the other hand, it's surely tempting to have all the Raptors be identical aside from the nozzles
TheMatrix Equation-balance
TheMatrix Equation-balance
@fyrepenguin - This is a critical junction. They don't have room for more than 33 Raptors (in Super Heavy). And they can't realistically scale up the current Raptor engine. If it turns out they have a critical power deficiency in Super Heavy, they will not have any easy solutions.
Erin Anne
Erin Anne
I don't understand why you think a critical power deficiency is a risk
aside from "if we can't actually get all the Raptors to run at full power"
ascent analysis simulations are trivial. It's really, really easy to figure out what the power margins are
TheMatrix Equation-balance
TheMatrix Equation-balance
So far, given the information, it could be the case that the current Super Heavy configuration is the bare minimum for a loaded Starship launch.
Assuming that all the Raptors are firing.
fyrepenguin
fyrepenguin
@TheMatrixEquation-balance given what information? They’ve mentioned that they should have engine-out capacity. Where does this mention of barely having enough power to launch come from?
TheMatrix Equation-balance
TheMatrix Equation-balance
@fyrepenguin - we don't know what the margins are. At what percent of capacity, Raptors can work during assent.
Erin Anne
Erin Anne
23:00
lol
if you see an analysis out in the wild that says there may not be sufficient power, bring it
or if you put together an analysis yourself somehow
TheMatrix Equation-balance
TheMatrix Equation-balance
I'll sleep like a baby, if you provide some insider information confirming that my fears are not founded.
Erin Anne
Erin Anne
there's no particular reason to believe that SpaceX don't know what the margins are, though
the same as you'd give up your StackExchange account if it turned out that Super Heavy was going to make a landing attempt?
TheMatrix Equation-balance
TheMatrix Equation-balance
Elon always exaggerating.
Erin Anne
Erin Anne
ahahaha. ok
fyrepenguin
fyrepenguin
Elon, maybe. Particularly with timelines. But not so much talking to the FAA

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