Craig,
This algorithm sounds very interesting. Are there any papers about it? Does it
have good convergence properties, at least comparable to popular
exo-atmospheric guidance algorithms? I could not find any papers in AIAA or
NTRS under your name or Boost Iterative Guidance.
Cheers,
Ian
--
Ian M Garcia
________________________________
From: arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> on behalf of
Craig Fink <webegood@xxxxxxxxx>
Sent: Sunday, June 9, 2019 1:15:24 PM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: SpaceX landings (was Re: SpaceX Single Stage to Orbit -wings)
When I worked on the Space Shuttle GN&C, I wrote a closed loop first stage
guidance algorithm that was small enough and fast enough to fit on the
Orbiter's tiny computers. Just upload the measured wind on the day of launch
and it would do the rest. Really nice algorithm that was never implemented
named BIG, Boost Iterative Guidance. When I was done, it flew beautiful
trajectory right down the center of the loads corridor and hitting the SRB
separation targets every time. At the end of the project I decided to see if I
need to add anything for the Engine Out Case, so I ran various engine out cases
without telling the Flight Software that an engine had fail. The closed loop
first stage guidance handled every engine out better than the actual flight
software. Instantly pitching up, within the load/heating constraints and
hitting the staging targets better than the actual FSW. That's what a closed
loop guidance is supposed to do.
There is nothing stopping SpaceX, if they haven't already done so, from doing
something similar with it's landing guidance. If the center engine fails during
the landing burn, I can easily imagine making a safe landing with two side
engines running with the right guidance algorithm. Or, even landing with one
side engine running, that would be a fun one.
--
Craig Fink
WeBeGood@xxxxxxxxx
On Sat, Jun 8, 2019 at 8:01 PM Henry Spencer
<hspencer@xxxxxxxxxxxxx<mailto:hspencer@xxxxxxxxxxxxx>> wrote:
On Thu, 6 Jun 2019, Craig Fink wrote:
... It's more efficient to make the corrections early than wait until
the last second.