You can see some neat shock interaction with the pad on this old
video: https://www.youtube.com/watch?v=mK9cbPoi5Fw
Also a quick demo of even a small plume getting rid of anything that
isn't attached to the pad.
We did damage one nozzle with concrete debris, it took a chip out of
the thin part of the jacket at the nozzle-end o-ring gland on a
chamber-saddle-jacket engine. Ended up repairing it with aluminum
solder. On other tests where we were destroying a pad we found bits of
spalled concrete on top of the rocket. The primary area hazard of the
rocket was hot chips of concrete lighting bushes on fire.
On Sat, Apr 22, 2023 at 9:19 AM jake <dmarc-noreply@xxxxxxxxxxxxx> wrote:
Oh nothing is ever trivial with this much energy around that's for sure.
I do wonder though what the "atmospheric" pressure would be in the middle of
the whole engine cluster while sitting on the pad. Given all the exhausts
around it forming basically a shield I imagine there must be a healthy
pressure gradient from atmospheric to something greater towards the middle.
Of course there would also be an "eudiction" effect along the plume boundary
acting to pump it down too.
I think Mr Carmack experienced something along those lines on his hover tests
years ago when the nozzle of his hopper got close enough to the ground to
form effectively a second nozzle or something along those lines?
I still like the spike shaped diverter though, worst case it's failure modes
are photogenic ;-)
Sent from my Galaxy
-------- Original message --------
From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
Date: 22/4/23 1:58 am (GMT+10:00)
To: Arocket List <arocket@xxxxxxxxxxxxx>
Subject: [AR] Re: starship pad flame trench?
On Fri, 21 Apr 2023, Jake Anderson wrote:
I want to see a "reverse aerospike" as the diverter.
OK so it's just a plain spike, with a water outlet at the top, dump a
squillion tonnes of water out the top of an 8ish meter high spike (to
fit under the OLM) that has a nice radiused curve into being level with
the ground.
Careful here -- the aerodynamics of flame deflectors, especially big ones,
aren't simple. That exhaust flow is highly supersonic, and when it hits
something shock waves will form, so just making the shape any old smooth
curve won't necessarily do what you want.
Henry