[AR] Re: thinking big once more
- From: Dave McMillan <skyefire@xxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Wed, 28 Sep 2016 17:53:31 -0400
On 9/28/2016 4:51 PM, Jonathan Goff wrote:
Henry,
I also wonder about the probability of unsurvivable engine failures
with Raptor. At 3x the chamber pressure, and 5-6x the peak pump outlet
pressure of a Merlin-1D while being in the same general package, we're
likely talking about a 3-6x increase in worst case P*V energy
available to do antisocial things. Not sure if that means anything,
but it at least suggests to me that anti-fraticide protections might
be more challenging and heavier for Raptor.
But how does that compare to the potential RUD energy release of
engines 4-5 times larger than the F1 (which, IIRC, is roughly what it
would take to replace ~42 Raptors with 5-6 of the bigger engines?)
Since the rule of thumb (IIRC) is that the 1st stage is the least
sensitive to dry mass increases (I know, that's not the same as
"insensitive"), and recalling all the discussions of Big Dumb Boosters
(aka Minimum Cost Design) years ago, what's the trade between putting a
reasonable (for the most likely violent failure scenarios) amount of
"armor" between lots of adjoining small engines and and a smaller number
of adjoining big engines?
Or maybe SpaceX will get it working without an hitch, who knows.
"Without a hitch" seems very unlikely. "Get it working well
eventually" seems reasonably probable, assuming no seriously
disastrous/expensive incidents along the way.
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