Introduction

The Mission Planning and Analysis Division produced, in February 1970, an internal note describing the role of MPAD in the Apollo 11 adventure. This note is an outstanding example of the dedication, and the feelings, that the people working in this division had for their work. Filled with hard data, matter-of-factly highlighting the precision of the flown missions compared to the predictions, this document is nonetheless an emotional account of one of the major accomplishment of this elected group of men and women.

To describe MPAD work and its role we extracted portions from that document ( MSC Internal Note 70-FM-20: The Apollo 11 Adventure) and let the different branches speak for themselves. The full document, which contains also a summary of the A11 flight interspersed by citations from crew exchanges with MCC, is available in the downloads section of the site.

The Landing Analysis Branch

 "The designated responsibilities of the Landing Analysis Branch are mission planning and analysis related to descent to and ascent from the surface of gravitational bodies with consideration given to thrust controlled flight and aerodinamically controlled flight as required."

This branch work was thus split between two different sections, one devoted to the Lunar Landing and the other to the Reentry Studies.

Lunar Landing Section

"Specific tasks which must be performed to produce a final lunar module descent/ascent mission design include powered flight trajectory analysis, guidance analysis, systems analysis, guidance and flight monitoring procedures development, and real-time mission support."

The two different phases are divided into events: "CSM/LM undock, CSM separation, descent orbit injection, and the powered descent" for the descent, and "prelaunch preparation, ignition/staging, vertical rise, pitchover, and insertion upon completion of powered flight".

It is of course highlighted that "Development of procedures and techniques to monitor critical systems and to assess flight progress, both by the crew on board the vehicle and by the ground flight control personnel, received much attention. It seemed as if all of MSC and a large contractor force were involved in this effort, and its importance cannot be overemphasized".

Between the data offered in support of this section are found two complex figures that nicely summarize all the main data for the lunar descent and ascent phases.

Reentry Studies Section

"Atmospheric reentry includes the passage of the command module through the earth's atmosphere and the safe arrival of the CM at a predetermined geographical location."

In doing this crew safety and trajectory control are the main problems.

Crew safety "can be divided into three areas: (1) heating, (2) excessive gravitational forces, and (3) skipping out of the atmosphere".

Trajectory control "once the spacecraft has safely penetrated the earth's atmosphere, is to guide the spacecraft to a predetermined landing point".

Between other data is found, at the end of this section, the actual A11 EMS scroll, showing the flown path of the CM during reentry.

The Flight Analysis Branch

"The functions of the Flight Analysis Branch are to establish operational procedures and data to support the mission trajectories, to assure flight safety, and to support the real-time command and control functions."

This branch is futher partitioned in three sections: Contingency Analysis, Flight Studies and Mission Support.

Contingency Analysis Section

The key approach used by MPAD for mission planning leverages on the management of any contingency. For every flight phase there was one, or more, abort modes that took into consideration system failures and other types of operational situations requiring the termination of the mission and the safe recovery of the crew.

"To insure the high confidence level required by the Apollo Lunar Landing program, a practical return-to-earth abort capability must be defined throughout the various mission phases. Definition of this capability and implementation of the associated techniques into the mission planning and crew training activities are the major functions of the Contingency Analysis Branch. In general, spacecraft and operational constraints are super-imposed on safe return-to-earth trajectory requirements. The resultant interaction has led to the evolvement of several distinct abort techniques and powered flight monitoring procedures. These techniques and procedures are combined to ensure that a safe return-to-earth capability exists throughout the spectrum of anticipated contingency conditions."

Between the material provided there is an outstanding summary chart that shows how each mission phase was complemented by one, or more, contingency procedures options.

Flight Studies Section

With this section one enters the realm of the more esoteric aspects of spaceflight: the relative motion of the involved bodies and the intricacies of orbital dynamics.

"The members of the Flight Studies Section investigated the topics of separation and recontact, orbital debris, and range safety for the first lunar landing mission. Separation techniques and procedures were analyzed, and in some cases defined, to insure there would be no recontact between manned vehicles and unmanned jettisoned configurations. All phases of the mission, from lift-off to landing were evaluated for the nominal, abort, and alternate mission cases."

The main separation cases were "the nominal CSM/LM ejection and the CSM SPS evasive maneuver from the S-IVB and the nominal LM ascent stage jettison in lunar orbit". In addition to the related analyses "gymbal angles were generated to be used by the crew to view the S-IVB during the evasive maneuver and to view the LM ascent stage after jettison".

"Earth entry of spacecraft debris [ SLA panels] was analyzed to determine the probability that a casualty would result from the nominal mission".

"The nominal CM/SM separation was also analyzed to predict the trajectory of the SM after separation and the landing area for the SM debris".

Mission Support Section

"The Mission Support Section is responsible for the management, planning, and operation of the Real-TIme Auxiliary Computing Facility ( RTACF)". This responsibility included "the development of computer processors to satisfy the RTACF computing requirements".

After the Apollo 10 mission "thirty-eight team members from the Mission Support Section and its contractors support organisations began program verification and training" and this included support for sixteen simulations "during which compatibility checks were made with RTCC".

"During the mission, six hundred and thirty-seven [637] data requests were satisfied for the RTACF requestors". This simple statement is then followed by the exhaustive list of topics handled by the RTACF. A 6 pages list spans all the possible aspects of spaceflight. It is interesting to note the development of "a complete return-to-earth capability was developed and tested at Bellcom in Washington, D.C., in support of the Emergency Mission Control Center. This capability could have been used by the flight control team in the event of any loss of the Houston Mission Control Center."

The Apollo software effort is typically related to the development of the Apollo Guidance Computers software (for the CSM and the LM). Seldom is the ground software brought into consideration despite its life- and mission-critical role. An historical missed-in-action that needs recovery.

The Mathematical Physics Branch

This branch contribution goes tersely straight to the point: the computations related to navigation accuracies. In particular a "review of lunar orbit accuracies associated with the location of the lunar module (LM) at the beginning of the powered descent".

The presence of Mascons and other irregularities in the lunar gravitational field led to great uncertainties in the localisation of the CSM and LM while orbiting the Moon, with related implications to the accuracy of the landing phase. Data related to pre-Apollo 8, Apollo 8, pre-Apollo 10 and Apollo 10 are presented as well as the procedures developed to reduce the errors with Apollo 11.

Of note are the reproductions of MCC computer displays showing state vector data and landing site location estimates during Apollo 11 LM flight, and a description of the R2 Moon Model.

The Lunar Mission Analysis Bunch

"In 1961, the Lunar Trajectory Section of the Mission Analysis Branch, which has become the Lunar Mission Analysis Branch [the 'Bunch' in the title is theirs], started to develop the computer programs and trajectory analysis techniques required to conduct a lunar landing mission. Since that time, many thousands of manhours have contributed to the successful completion of a manned lunar landing mission."

Among its contributions it "conducted preflight targeting scans; determined the launch window; supplied the Marshall Space Flight Center with the S-IVB targeting to obtain the proper insertion, and transearth injection procedures and real-time targeting logic; and managed the formulation, implementation, and verification of the RTCC programs required to support the lunar mission.". Again an under-estimated life- and mission-critical ground software effort.

The rest of their chapter is a concise and highly readable summary on how to go to the moon and get back in terms of trajectories and targeting data. It starts from Free-Return Trajectories and continues with Launch Window Considerations (also applied to the A11 case), Real-Time Targeting, Translunar Coast (with LOI and Mid Course Corrections), Transearth Coast (with TEI and again Mid Course Corrections).

The Orbital Mission Analysis Branch

As the name implies this branch deals with orbital flight, around the Earth or the Moon, in a way similar to what the previous branch did for the specific aspects of a lunar bound flight. Another exciting branch since it dealt primarily with rendezvous techniques and procedures.

"Development of the nominal rendezvous for the lunar landing began early in 1963 with the direct ascent technique. The entire development included ten phases: the first five phases took about a year each to develop; the last five were developed within the year preceding the Apollo 11 mission".

The note then proceeds in giving a short-form but complete summary of the different rendezvous approaches and, as in the previous case, is highly readable and full of insights. The list goes as follows: (1) Direct Ascent; (2) Standard Insertion Parking Orbit with Standard Direct Intercept at Variable Time; (3) Direct Coelliptic Sequence; (4) Original CSI-CDH Coelliptic Sequence; (5) Same Coelliptic Sequence as for Phase 4 but with Optimized Terminal Phase; (6) Same Coelliptic Sequence as for Phase 5 but with CSM in 60 n.mi. Circular Orbit; (7) Extended CSI-CDH Coelliptic Sequence; (8) CSI-CDH Coelliptic sequence with Controlled CSI-to-CDH DeltaT; (9) Same Coelliptic Sequence as for Phase 8 but with Insertion Orbit 45 by 10 n.mi.; (10) Apollo 11 CSI-CDH Coelliptic Sequence (with radial component at insertion).

In closing, and in addition to A11 rendezvous targets, a Question/Answer list is provided about all the choices made for A11 rendezvous. Here is an example:

"Q - Why is the nominal parking orbit for the CSM approximately 60 n.mi. circular?

 A - Not higher because of LM RCS DeltaV budget; not lower because of the phasing situation for powered descent aborts." 

A unique contribution to this note.

The Guidance and Performance Branch

This branch is divided in two sections: the Guidance Analysis Section and the Consumables Analysis section.

The Guidance Analysis Section

"Out of the most significaant contributions of the Guidance Analysis Section to the first lunar landing mission (Apollo 11) was the definition of the ground guidance monitoring philosophy and procedures for the powered flight maneuvers. The monitoring consists of evaluation of the guidance systems during the following maneuvers."

The maneuvers were: (a) Launch evaluation for commitment to TLI; (b) TLI evaluation for commitment to LOI; (c) LM PGNS and AGS evaluation during lunar descent for descent abort and a guidance switchover decision; (d)  LM PGNS and AGS evaluation during lunar ascent for a guidance switchover decision.

In support of the good performances recorded during the A11 flight, strip chart records are provided. 

The Consumables Analysis Section

"Many problems are associated with the consumables subsystem. The first one is to determine which problems are critical and how they can be defined and then integrated into the total mission planning cycle."

Using information from trajectory, flight plan, system/subsystems/components, and various constraints and considerations, "computer programs are written for the basic mission timeline and the various consumables analyses are conducted and appropriate information is included in the mission plan. An iterated loop is required to feed back out-of-tolerance conditions and to provide for the updating that is inevitably required."

A table showing the accuracy of A11 consumables predictions is provided.

The Advanced Mission Design Branch

"In the beginning, there were three possible approaches to the lunar landing mission": (1) Direct Approach; (2) Earth Orbit rendezvous; (3) Lunar Orbit Rendezvous.

"Originally, the direct approach was favoured by the Space Task Group (STG), and the original contract to North American Aviation (NAA) indicates that this mode was favoured by the MSFC. The lunar orbit rendezvous mode was suggested by the Langley Research Center. After several months of study, the Space Task Group switched the direct approach to the lunar orbit rendezvous mode and initiated a three-way battle among STG, NAA and MSFC as to which approach was technically best."

History was thus made and samples of the original budgets originate within this branch are provided.

"The choice was made in favor of the lunar orbit rendezvous mode at a high level meeting attended by the President of the United States of America, and almost immediately there was a call for a DeltaV budget so that the size of the system tanks could be determined.". The results of that budget analysis are also provided.

The contribution of this branch details some important actors in the early definitions of the lunar trajectory, lunar landing trajectory, as well as the Linear Acceleration Guidance Scheme for Landing and Launch Trajectories in Vacuum, the basis for LM descent and ascent guidance.

Samples of original presentation slides are included.

Conclusions

This short introduction doesn't talk about other participants in MPAD, like the Administration Office and the Report Preparation Office, represented in the note with some funny sketches. But all the actors of MPAD are there with their signatures including those of Bill Tindall and his secretary.

 At the time this document was issued, February 1970, Tindall was the deputy chief of MPAD, the chief was John P. Mayer. The heads of the different branches (whose names are often found in many documents) were:

Landing Analysis Branch: Floyd V. Bennet

Flight Analysis Branch: Charlie C. Allen

Mathematical Physics Branch: James C. Mc Pherson

Lunar Mission Analysis Branch: Ronald L. Berry

Orbital Mission Analysis Branch: Edgar C. Lineberry

Guidance and Performance Branch:Marlowe D. Cassett

Advanced Mission Design Branch: Jack Funk

15/12/2008 - Edited after proofreading by librarian.