NATION AL
AERONAUTICS
AN D SPACE
ADMINISTRATION

 

 

OFFICE OF THE ADMINISTRATOR
1520 H STREET NORTHWEST
WASHINGTON 25, D.C.

IN REPLY REFER TO SL TeLePHone: EXgcurive 3-3260 TWX: WA 755

 

NOY 2s i861
Dr. Joshua Lederberg
Stanford University
Medical Center
Palo Alto, California

Dear Dr. Lederberg:

Thank you for your letter of October 11. In the letter and the
material accompanying it, you raised several questions relative to
Mariner Be Since these missions are very important to us, I would like
to take this opportunity to describe to you the basic philosophy and
ingredients of the present NASA planetary program.

~
The points you made have been among those that we have considered ~
very carefully during all efforts to develop our plans - although, at
times, it may appear that they have not. The reasoning that has led to XX
current program philosophy is, unfortunately, not simply stated; many a
constraints exists, some definite and essentially unalterable, some ~
arbitrary. Furthermore, these constraints are closely related and a
interwoven. ®
—

The first constraint results from the launch vehicle capability
required for planetary missions. Considering first the 1962 opportunities,
the Atlas-Agena B, the only developed vehicle suitable at present, is
just capable of sending a marginal planetary spacecraft (460 pounds) to
Venus; a Mars mission is not practicable. In 1964, the Centaur vehicle
should be available, and it is expected that it will be able to inject
about 1,000 pounds to either planet. Even with this weight, the desired
amount of systems redundancy is not possible, and the effect of mission
complexity on overall reliability must be carefully considered.

A second constraint is related to the fact that, at present, a
planetary mission is a difficult objective - even assuming injection into
an escape trajectory. Part of the difficulty is that to have a reasonable
possibility of completing a four to six-month trip and accomplishing a
close fly-by with an operating spacecraft, all spacecraft subsystems -
attitude control, guidance power, propulsion, scientific instrumentation,
and communications - must have reliabilities that are difficult to attain
within current weight limitations. If this reliability problem is added
to the fact that maximum use must be made of the limited opportunities
for planetary missions, the resulting viewpoint is that extreme care must
be taken to see that any added complexity is well worth the associated
reduction in reliability.
Dr. Joshua Lederberg ~2- NOY 2. 1989
Stanford University

A third constraint is a consideration of the resources available and
the optimum distribution of these between the various programs of merit.
NASA has undertaken a great many programs of significance in a short time,
and must carefully weigh the use of funds, personnel, and facilities for
each, so as to maximize the return of valuable results per unit of time.

Consideration of these factors has led to a philosophy that calls
for two launches at each planetary opportunity. It is also planned that
these missions will be preceded by spacecraft demonstration flights. A
principal objective for early planetary missions will be to prove the
difficult technology necessary to send spacecraft to the planets that are
capable of transmitting data to earth at the time of planetary encounter.

The present program plans call for utilization of the Atlas-Agena B
to launch two Mariner R spacecraft to Venus in 1962. With a test flight
in 1963, the Centaur Mariner B project is expected to include two launches
to Venus and Mars at each opportunity, beginning with Venus in 1964 and
continuing to overlap the first operational Voyager missions on Saturn.

An entry capsule is being added to Mariner B at the earliest opportunity
consistent with launch vehicle capability and mission reliability, hope-
fully for the Mars '64 missions. Interest in the capsule is very high,
both because of the need to acquire the necessary entry-landing technology
and because of the obvious scientific possibilities.

Im conclusion, I think that the NASA planetary program is well
planned to make maximum use of existing technology, and that it will be
evolutionary in such a way as to maximize overall objectives. I also
believe that the presently planned program, considering all factors
mentioned above, is reasonably in keeping with the ‘desirable requirements
you have expressed, and hope that this letter will provide you some
assurance that NASA is making every effort to achieve a sound, successful
planetary program,

Thank you again for your interest in the NASA programs.

Sincerely,

Abayh £ Oanyn

Hugh L. Dryden
Deputy Administrator