March 1983:space activities report

SUCCESS FOR PAM

The fifth mission of the Space Shuttle saw the first
use aboard the reusable spacecraft of an important
new addition to the family of rocket stages: the Payload
Assist Module (PAM).
The new stage was privately developed by the
McDonnell Douglas Astronautics Company as the first
commercial space launch vehicle. The first PAM was
pushed out by springs from the cargo bay of Columbia
precisely on schedule on 11 November. It drifted with
its SBS communications satellite payload for 45 minutes while the Shuttle moved to a safe distance. Then
it began an 83 second rocket burn to boost SBS-3
towards geostationary orbit, approximately 22,898 mi
(36,851 km) above the Earth.

Twenty-four hours later, the launch was repeated
with Telesat Canada's ANIK-C3 satellite. Both satellites
were moved into their final operational circular orbits
of about 22,300 mi (35,887 km) by built-in "apogee
kick motors" a few days later.
The specially designed cradles that held the PAMs
and their payloads in the cargo bay were returned to
Earth by the Shuttle for use on future missions.

The mission aboard STS-5 marked the ninth and
tenth launches for PAM since 1980. On the first eight,
PAM operated as the third stage of the Delta launcher.

The next Shuttle mission for the Payload Assist
Module will be aboard STS-7, scheduled for launch
next April. Telesat Canada will use PAM again with the
ANIK-C2 satellite, accompanied by a second PAM
carrying the Indonesian communications satellite
Palapa-B1. Altogether, more than 60 PAM missions aboard the
Shuttle may fly over the next five years. In addition to
the PAM-D's 2750 lb (1274.5 kg) Delta-class payload
capacity, McDonnell Douglas is offering two other PAM configurations to handle large Shuttle payloads: the
recently announced PAM-D2 for satellites of up to
3500 1b (1587 kg) and the PAM-A (Atlas Class) for
those weighing up to 4400 lb (1996 kg).

SHUTTLE ENGINES

The three main engines from Shuttle Orbit,er Col¬
umbia will next fly into space aboard a new Shuttle
craft. According to Judson Lovingood, manager of the
Space Shuttle Main Engine Project at the Marshall
Space Flight Center, the engines will undergo a complete overhaul before they are reused again on Orbiter
Atlantis, due for delivery late next year. These engines,
which were operated at 100 per cent of rated thrust
on Columbia, will be modified and retested to certify
them for operation at 109 per cent aboard the fourth
Orbiter.
The engines have been removed from Columbia and
shipped back to the manufacturer (Rocketdyne Division
of Rockwell International in Canoga Park, California).

The first order of business was to carefully disassemble
them. Then every part was to undergo inspection to
determine wear and reusability. "We know that some
parts will have to be replaced because of the increased
temperatures and pressures they will see at the higher
power level,” said Lovingood. "But we would also like
to see if the flight environment has a different effect
on the hardware that we have seen in ground testing."

The engines will be reassembled and thoroughly
checked before being shipped to the Marshall Center's
engine test facility at the National Space Technology
Laboratories for a series of acceptance test firings.
These firings, tentatively schedule for autumn 1984,
will include ignition, calibration and endurance tests.
The engines underwent similar test firings before they
were installed in the Columbia.
After the engines have been accepted for flight by
the Marshall Center they will then be installed in
Atlantjs in time for its first mission in 1985. Columbia
will receive three brand new engines for its next flight,
the Spacelab mission in September.

JAPAN'S THIRD METSAT

Japan's Geostationary Meteorological Satellite
(GMS) programme will take a further step forward in
August 1984 when the third satellite (GMS-3a) will be
launched using the sixth N-2 vehicle. GMS-3a will be
placed in geostationary orbit at 140° East longitude
covering the Japanese segment of the World Weather
Watch, writes Nicholas Staggall.
The GMS-2 prototype model will be used as the
GMS-3a flight model although some refurbishing will
be required. This work will be based on the experience
gained from the flight model of the GMS-2 now orbiting
the Earth.