Quote:
Originally Posted by Peter Ward
I expect the new lander will have an almost fully automated descent and landing capability...but details of this are remarkably scant on any NASA information release.
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"Digital Apollo" by David A. Mindell provides a detailed account of the
design process and engineering of the Apollo flight systems including the
man machine interface. It also provides accounts of each of the landings
and what was learnt from each one with respect the design of the
flight systems.
It discusses how it was originally envisaged by some that the landing
would be fully automated. The LM was ungainly to fly, with 16 thrusters
and the main gimballed engine. Pilots had originally wanted to perform the
landings manually but in simulators they crashed every time.
The LM Digital Autopilot came into being where the pilots could insert
themselves into the loop. Inputs from the pilot were interpreted by
a digital computer and it fired the thusters, continually compensating
for the changing of center of gravity as fuel was spent and when it
sloshed around in the tanks. Even the 8-ball resembled its analog
counterpart but was being driven by the computer.
The system was capable of everywhere between and including a
manual and fully automated landing.
When you listen to the comms loop during the Apollo landing sequences
you will hear them read out what program the computer is running
during each phase. The programs were designated 'P' with a numeric
suffix, so P63 for example was the initial braking phase program which was
taking the LM to a pre-programmed landing point. It then transitioned
to P64 which was the Approach Phase Guidance which was very similar
to P63 but also included a Landing Point Designation (LPD) option.
What was cool was that the triangular LM windows were etched
with an angular scale. The etching was both on the inner and outer
panes of the window so one could eliminate parallax. See image below.
The pilot could look at the numeric readout on the computer and
then eyeball the corresponding angle etched on the scale on the
window panes and looking out into the distance that point was what the
computer was computing to be the landing point. Conversely the pilot
could look out the window, read off the corresponding point on the etched
scale, punch that into the computer and it would take them there.
Or they could punch in P67 which allowed for manual inputs in a
fly-by-wire system. For example, certain operations on the joystick
would signal the computer to hover.
Programs such as P66 would give the pilot attitude control whilst the
computer controlled the rate of descent.
I recommend the book :-
https://www.amazon.com.au/Digital-Ap.../dp/0262516101
http://web.mit.edu/digitalapollo/
