February 1983:space activities report

MORE SHUTTLE ASTRONAUTS

NASA has decided to relax some of their requirements for
flying people aboard the Space Shuttle. Until now, flight
opportunities for Payload Specialists have been offered to
customers buying a half or more of a Shuttle mission or who were flying a unique experiment needing the unique talents
of a particular scientist or engineer.

Under the expanded programme, to begin in 1984, that
will change. Flight opportunities for Payload Specialists will
be made available whenever possible on a reimbursable basis
to all classes of Space Shuttle major payload customers,
including foreign and domestic commercial customers, international cooperative partners, the scientific and applications
community and the Department of Defense.

On the first four flights of the Shuttle, there were two
crew merpbers aboard, the commander and pilot. The fifth
carried four, adding two Mission Specialists, who helped in
deploying two commercial communication satellites.
In the future. Mission Specialists, who are experts in
extravehicular activity, operation of the Remote Manipulator
System and payload support systems, will be joined by
Payload Specialists on specific missions. They will be added
to selected flights to provide detailed, on-the-spot expertise
concerning payloads or scientific experiments. They will
most often be scientists, with special skills to operate a
scientific experiment, or a specialist proposed by a Shuttle
customer trained in the critical aspects of deploying and
operating a satellite.

Proposed Payload Specialists will undergo a short training
period in preparation for flight. NASA will retain final selection
authority to insure that they are fully qualified and can work
as part of the flight crew.

VOYAGER 2 PRESSES ON

The Voyager 2 spacecraft has now travelled about one
tenth of the distance it must cover for its encounter with the
planet Uranus, projected for 24 January 1986.
In the five years since its launch on 20 August 1978, the
probe has travelled 3000 million km and is now 1700 million
km from Earth. Most of the science instruments are functioning well after more than 40,000 hours of operating time.

Sixty-seven of the original 104 kg of propellant remain to
be used for attitude control and trajectory correction. The
two radioisotope thermoelectric generators are furnishing
422 watts of electrical power, which is 92 watts more than
the requirement. The two areas of concern are one scan
platform actuator which is showing signs of wear and the
radio receiver which has reduced tracking capability. Neither
of these problems is expected to seriously affect the future
encounter with Uranus.
Mission controllers at NASA's Jet Propulsion Laboratory
in California are in daily contact with the spacecraft as its science instruments monitor the interplanetary environment. One-way radio time from Voyager 2 to Earth is now 90
minutes.

Voyager now has sufficient velocity to ultimately escape
from the Solar System even though it has yet to fly by
Uranus in 1986 and possibly Neptune in 1989. With a
heliocentric velocity of 19.9 km per second (44,600 miles
pfer hour), it has the distinction of being the second fastest
object made by man. Its sister ship, Voyager 1, is travelling
slightly faster.
In its epic journey thus far. Voyager 2 has obtained
approximately 32,000 images of Jupiter and Saturn with
their rings and 13 major satellites. Planning is already
underway for photographing Uranus with its rings and five
satellites in 1986.

IMPROVED SHUTTLE BOOSTERS

A high performance booster motor for the Space Shuttle
was test fired for the first time last October. The motor has
been redesigned to increase the initial thrust of the Shuttle
at liftoff, allowing the reusable spacecraft to carry more
payload.

According to Frank Adams, deputy manager of the Solid
Rocket Booster Project Office at NASA's Marshall Space
Flight Center, the thrust increase was achieved in several
ways. "To the casual observer, the motor will look the same
as those we are presently using. However, we have reduced
the size of the 'throat' and increased the length of the
motor's exit cone. We have also increased the burn surface
of the propellant by removing some of the inhibitor used at
the ends of the four centre motor segments," said Adams.
"These changes will give the motor a higher specific impulse
which increases its performance and thrust."

The higher thrust motors will be used for the first time on
the eighth Shuttle flight, now scheduled for mid-1983. The
two motors will provide an additional 4 per cent thrust over
the motors currently in use which deliver about 2.8 million
pounds of thrust (12.5 MN) at liftoff.

Two giant Solid Rocket Boosters provide approximately
75 per cent of the Shuttle's power for liftoff from the launch
pad and during the first two minutes of flight. After their
propellant has burned out, the boosters separate from the
Shuttle and parachute into the ocean where they are
recovered and returned to Kennedy Space Center. They are
then refurbished and reused on subsequent Shuttle missions.

MARS/MOON MISSION STUDIES

RCA Astro-Electronics, builders of the Tiros and some of
the Explorer satellites, have been asked by the Jet Propulsion
Laboratory in California to study the feasibility of converting
their spacecraft for Mars and Lunar-orbiting missions. The two satellite concepts are:

• The Mars Geoscience Orbiter (MGO), which would
operate for one year in a low polar orbit over Mars and
carry a gamma-ray spectrometer, multi-spectral mapper, magnetometer and a radar altimeter.

• The Lunar Geoscience Orbiter (LGO), which would
operate for one Earth year in a low polar orbit over the
Moon. It would carry the same complement of instruments as the MGO, plus an X-ray spectrometer and
electron reflectometer.