Invitation to DPS throttling for DOI meeting

See list belowFEB 5 196868-FM-T-20FM/Deputy ChiefInvitation to DPS throttling for DOI meeting

1. This memo is to notify you of a long overdue meeting. Even I have been aware for at least a year and a half of the lack of definition of the spacecraft computer program requirements associated with throttling the descent propulsion system (DPS). During that time we have gone through a whole series of program change proposals— some of which have been implemented, some discarded. What we must do is to get all interested parties together to pin this business down once and for all in order to provide positive direction to MIT for the Luminary program. Unfortunately, we are probably already far late to avoid schedule impact.

2. Out primary problem deals with how we should use our guidance and propulsion systems to make the descent orbit insertion (DOI) maneuver on a lunar landing mission. Questions involve:

a) how long to remain at 10% thrust

b) what thrust level to proceed to for the latter part of the burn?

c) what sort of option should be provided the astronauts and/or the ground in the control of this maneuver?

d) what limitations the DPS imposes, such as helium pressure, freezing, etc.

e) what sort of limitations the guidance system imposes primarily involved in maneuver accuracy.

f) how the RTCC should do the targeting for those maneuvers

g) what guidance mode should be used (that is, Lambert or External Delta V

h) the value and desirability of providing a manual throttle test during the maneuver

i) And I am sure there are many others.

3. Accordingly, we have set up a meeting for February 14 starting at 9:00 a.m., and possible lasting all day long, to attempt to resolve all this and to develop a precise definition of spacecraft and ground computer program requirements, and perhaps, some mission rules and procedures, etc. The meeting will be held in Building 30, Room 2032B. You and/or your representatives are urged to attend. In fact, I would appreciate it if you would review the distribution and see if I have overlooked anybody who should be there, and let them know.