Well , that's OK Norman, we can just agree to disagree. You can't have one
without the other, pressure must increase as the plume velocity decreases
and approaches zero, stagnates. Compression = heating. Another analogy, a
pitot tube converts velocity into pressure/airspeed.
Regardless, a concrete pad makes for a poor flame deflector and if I were
to be a gambling man I'd bet SpaceX employs some kind of flame deflector in
their next launch or, if they stay with a flat pad, it will be the largest
ablative heat shield in history. Even the Germans used a 4 lobed deflector
on the V-2 launch stand which the US used in the post war Redstone/Jupiter
C rockets which put the first US man in space (sub orbital).
Ken
On Fri, Apr 21, 2023 at 11:33 PM Norman Yarvin <yarvin@xxxxxxxxxxxx> wrote:
On Fri, Apr 21, 2023 at 01:36:37PM +0300, Ben Brockert wrote:
Though you don't define "significant percentage", I don't think the
math is as simple as you imply by quoting the chamber pressure.
Yeah, it's chamber _temperature_ rather than pressure that gets
approximately re-achieved when rocket exhaust hits a surface and
stagnates. (In vacuum, that is, or in air but close enough that there
hasn't been significant mixing yet.)
Pressure depends on how much it's spread out.