April 1980:space activities report

SYLDA FOR ARIANE

During the early 1980s, a number of payloads in the 600 to 1000 kg class are due for launch into geostationary transfer orbit. This type of payload would normally be orbited by a US Delta vehicle or as part of a Shuttle payload.

The carrying capacity of Europe’s launch vehicle, Ariane,is about 1700 kg, which would allow it to carry two such satellites. To capitalise on this, the European Space Agency has awarded a contract for the construction of SYLDA (Systeme de Lancement Double Ariane) to Aerospatiale.

SYLDA is being built at the Les Mureaux Centre of Aerospatiale. The programme was initiated in June 1978 and the first use of SYLDA will be during 1980 on Ariane launch L-04 (the fourth trial launch).

The problems to be solved by engineers were to build a structure capable of supporting two satellites, making such a structure fit within the standard Ariane launch shroud, keeping mass to a minimum and ensuring that the satellites could be totally independent of each other. All these requirements were met by developing a container for the lower satellite which also acts as a support for the upper one.

SYLDA is a two part structure designed to split in an equatorial plane, after separation of the upper satellite. The lower vehicle is then free to depart on its own trajectory. Careful choice of separation velocities for the two satellites and the upper part of SYLDA ensures that there is no danger of collision between them.

Although SYLDA’s mass is 165 kg, the total weight penalty is only 120 kg because it replaces the normal Ariane separation system. Its structure is a honeycomb aluminium core covered in layers of carbon fibre. Windows in its lower section allow access to the enclosed satellite and also permit two-way radio communication. The two halves are held together by conventional clamping bands which are released by pyrotechnic devices. Four springs ensure separation.

The shape of the device imposes some constraints on the shape of the lower satellite. Otherwise, the upper limits are 2.6 m in length and 2.2 m diameter. The combined masses of the satellites should not exceed 1580 kg at present. Mechanical and electrical interfaces with the satellites are identical to those of the Shuttle Payload Assist Module, and the volume offered to the upper vehicle is the same as that of the PAM. Later development plans include expansion of the structure by a further 0.5 m on its length which will mean that two PAM-sized satellites can be carried. This would depend on expanding the standard Ariane shroud and uprating the launch capacity to 2500 kg.

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SPACE SHUTTLE PAYLOADS

Despite the delay in launching Columbia on its first test flight from Cape Canaveral, NASA has received firm payload commitments for the first 37 operational flights beginning in 1981. The Shuttle is thus almost completely booked to the spring of 1984.

The 47 payloads supported by these flights represent commitments by 14 government, commercial and foreign users, and range from the European Space Agency’s Spacelab to weather, communication and navigation satellites.

NASA payloads are expected to account for 32 per cent of these payloads, the Department of Defense about 15 per cent and all other users about 53 per cent.

These payloads normally are assigned to flights on a first come-first served basis. However, missions that involve national security will be given priority, as well as missions with significant scientific and technological objectives or time-critical launch windows. Flights for which NASA will be fully reimbursed also will be given preference over routine scientific and technological experiments.

A range of services are available to Shuttle users. Standard services, which are uniform for all non government users, include a basic Shuttle launch for a three-day mission with a standard orbital altitude and inclination, three person crew and standard support services. Optional services are available at extra cost upon request. These services could include special hardware, analysis and testing, use of Kennedy Space Center facilities and services, and special orbital operations such as extra-vehicular activity and missions of longer duration.

In addition to the 47 large payloads that will occupy much or all of the Shuttle’s cargo bay, more than 200 organizations and individuals have reserved room for some 300 small self-contained payloads, called Getaway Specials. These universities, companies and researchers, for $3,000 to $10,000, will send their own 200 lb or less payload into orbit aboard the Shuttle.

The Shuttle’s first payload, one of three preliminary payloads scheduled to fly before the Shuttle becomes operational, will ride the second orbital flight test scheduled this year. Named OSTA-1 for NASA’s Office of Space and Terrestrial Applications, the payload will consist of six Earth-sensing experiments designed to enable scientists to pinpoint natural resources and to study air pollution, lightning and ways to locate and track surface features and clouds. The payload will include also a life sciences experiment designed as a prototype for an experiment to be flown aboard the Spacelab, the pressurized manned orbiting laboratory designed to fit in the payload bay.

The thjrd orbital flight test will have a payload designed to allow astronauts to test the Shuttle’s remote manipulator system. This is a mechanical arm that will be used to take payloads out of the cargo bay, position them in space and also to retrieve satellites for return to Earth.

On the final flight test, an Office of Space Science payload (OSS-1), concerned with physics and astronomy experiments,will be aboard.