Sweet! Thanks for responding. I'll look into it and comment here if I find
something.
--
Ian M Garcia
From: Craig Fink
Sent: Monday, June 17, 6:12 PM
Subject: [AR] Re: SpaceX landings (was Re: SpaceX Single Stage to Orbit -wings)
To: arocket@xxxxxxxxxxxxx
Ian,
I'm not surprised you haven't been able to find any papers using my name, I've
never written one for AIAA or NTRS. But, I would be surprised if someone has
not written a paper on it or came up with a very similar algorithm. You might
want to look at NASA JSC Transmittal Memos, TM-#######. Last I heard, JSC
Library has them all.
Boost Iterative Guidance (BIG), was named more for the acronym BIG, and the
words fit the acronym. The Guidance Algorithm is much more extensible than just
a closed loop guidance during the boost phase of a rocket. Last time I heard
about where this Algorithm was going, it had been adapted to fly Space Shuttle
Second Stage, Space Shuttle East Coast Aborts, On-Orbit and Entry and Landing.
None of these actually implemented in the Shuttle far as I know. I'm sure that
someone else probably has written it up in the past 25 years.
BIG, was more of a jab at the Rocket Scientist who wrote the stripped down
6-DOF simulation that he called SIMP. SIMP was a full blown, but stripped down
6-DOF simulation that was small, compact and ran really fast. Two Pages of Code
with no comments. He named it SIMP, so when I wrapped a Guidance Algorithm
around it, the obvious choice to name it was BIG containing SIMP.
For the Space Shuttle, we had a high fidelity simulation of the vehicle called
SVDS. Along with being a simulation, it also had the actual Flight Software
coded within it, coded in parallel with the Space Shuttle Orbiter. So, I could
code BIG as a subroutine within the flight software contained within the high
fidelity simulation SVDS. SVDS would take hours to run on a Mainframe, SIMP
almost no time. Really, having a 6-DOF simulation On-Board any Vehicle is a
really good idea on so many levels.
So, the keywords that you might want to search on for a guidance algorithm
might be, 6-dof simulation, constrained optimization, adaptive self tuning gains
Constrained Optimization, understanding constraints along the path your vehicle
is trying to fly. For the Space Shuttle first stage constraints include Dynamic
Pressure as a function of Mach number, DynamicPressure * AngleOfAttack
(Q-Alpha) Loads corridor, Q-Beta loads corridor, AngleOfAttack heating limits.
Second Stage, Entry may have a different set of Constraints...
Steering Algorithm, In the case of the Space Shuttle, the simulation SIMP has
to have a corresponding steering algorithm that controls the flight through the
constraints. In first stage Space Shuttle, these include things like Initial
pitch over angle after attitude hold at liftoff (controls Dynamic Pressure),
Pitch rate blending into Q-Alpha steering, blending into Alpha steering.
Targets, where Guidance is taking the vehicle. In the Space Shuttles case,
first stage targets having a smooth transition to PEG guidance, no large
transient at staging yields great results. It could just have easily been
something like the Falcon 9 staging target like the impact point is the
Autonomous Drone Ship.
--
Craig Fink
WeBeGood@xxxxxxxxx
On Mon, Jun 10, 2019 at 8:27 AM Ian M. Garcia
<ian@xxxxxxxxxxxxx<mailto:ian@xxxxxxxxxxxxx>> wrote:
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<mailto:arocket-bounce@xxxxxxxxxxxxx>
<arocket-bounce@xxxxxxxxxxxxx<mailto:arocket-bounce@xxxxxxxxxxxxx>> on behalf
of Craig Fink <webegood@xxxxxxxxx<mailto:webegood@xxxxxxxxx>>
Sent: Sunday, June 9, 2019 1:15:24 PM
To: arocket@xxxxxxxxxxxxx<mailto: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.
