Double starting device

A satellite in the lower part of a double launcher

A double launch device is used to launch two large satellites into space at once with a launcher. For this purpose, the satellites are placed one above the other in the tip of the launch vehicle.

problem

In order to accommodate two satellites on top of each other in the rocket, the lower (second) satellite that sits on the rocket would have to carry the upper (first) satellite, because otherwise it could not be connected to the rocket. As a result, the top of the second satellite would not be usable, which would often lead to problems.

The lid is closed.

solution

To solve this problem, there is the double launch device, a largely cylindrical transport container, on the bottom of which the second satellite sits on a normal adapter and whose frustoconical upper side carries the first satellite, which is in turn seated on an adapter. Because there is a satellite in the twin launcher and one is on it, it goes into orbit with the satellites, so that its weight is removed from the payload mass.

Details

The adapter of the lower satellite can sit on the floor of the double launch device or directly on the launcher if the double launch device is open at the bottom. When the double launcher is closed at the bottom, it usually consists of two parts: a cover and a base piece, whereby the satellite is first placed in the base piece and then closed with the cover (with some rocket types the first satellite is already sitting on it with or without the Payload fairing). The upper satellite, on the other hand, sits directly under the payload fairing, which either only surrounds the satellite, so that the dual launcher is located under it, or the payload fairing surrounds both.

When the satellites are released, the upper satellite is released first. Then the top rocket stage rotates a little, and then the lid or the payload fairing open at the bottom is pushed off. Then the rocket stage rotates again and deploys the second satellite.

As a rule, the larger and heavier of the two satellites is attached to the double launch device and the lighter, smaller one in the double launch device.

Examples of different double launch devices

With Ariane 4

The Ariane 4 mostly used a double launcher, the diameter of which was the same as that of its payload fairing . The satellites could be equally wide. The smaller and lighter satellite was housed in the lower part of the double launch device. The larger, heavier satellite was mounted on top of the top of the twin launcher, with the payload fairing placed around it. Then this combination was mounted on the lower part of the double launch device. As a result, the double launch device was under the payload fairing. The logo of the satellite housed in the double launcher was therefore attached to this type of double launcher. The now complete combination was brought to the rocket on the launch site and attached to it. After reaching orbit (the payload fairing was thrown off during the flight), the upper satellite was ejected first. Then the third stage spun a little further and the top of the double launcher was pushed off. After the stage had rotated a little further, the lower satellite was finally released.

At Ariane 5

The Ariane 5 , on the other hand, only uses a double launch device (SYLDA5 - Système de Lancement Double Ariane 5), the diameter of which is smaller than that of the payload fairing almost over its entire length. The assembly is accordingly different. First, the larger, heavier satellite is placed on the one-piece double launch device that is open at the bottom. Then the already assembled payload fairing, open at the bottom, is slipped over the two and attached to the double launch device, which is just as wide at the bottom. In the meantime, the smaller and lighter satellite has been mounted on the tip of the Ariane 5, so that now only the combination of the upper satellite, double launch device and payload fairing has to be slipped over the lower satellite. The double launch device is therefore located in the payload fairing on Ariane 5. Then the rocket is driven from the assembly building to the launch pad. The launching of the satellites is the same for the Ariane 5 as for the Ariane 4, with the exception that the Ariane 5 has the double launch device launched in one piece.

The upper satellite is lifted onto the dual launcher of a Delta II .

With the Delta II

The Delta II rarely used a double launch device. As with the Ariane 4, this consisted of an upper and a lower part. However, the assembly was done differently. First the smaller and lighter satellite was attached with its adapter in the lower part and the upper one slipped over it. Then the larger, heavier satellite was attached to it. Then the whole thing was packed in a transport container and brought to the launch pad, unpacked and mounted on the rocket. Only here was the payload fairing installed around the combination of satellite and double launch device. In the Delta II - as in the Ariane 5 - the double launch device was therefore located within the payload fairing. After reaching orbit, the satellites were launched.

swell

Arianespace: Ariane 4 User Manual ( Memento from September 27, 2007 in the Internet Archive ) (21.5 MB ZIP )
Arianespace: Ariane 5 User Manual ( Memento from October 22, 2014 in the Internet Archive ) (23.4 MB PDF )

Web links

Commons : double launcher - collection of pictures, videos and audio files

Arianespace e-space Newsletter April 2000 ( Memento of March 11, 2006 in the Internet Archive ) (Contains, among other things, a description of the various payload fairings and double launch devices, PDF; 725 kB)
Delta II Payload Planners Guide (PDF; 10.0 MB)