Rideshare launch

A rideshare launch is a way of carrying several satellites together when a single rocket is launched. A large primary satellite takes up most of the launch vehicle, and small secondary payloads are placed in the spare room below it and sent up together. The cost of one launch is shared among several customers, so even small satellites get a chance to go to space.

This method began to take hold when devices such as the ESPA ring appeared, which the US government and industry started developing together in 1999. It was designed to use the space under the primary satellite that had gone unused, so that small satellites could be carried without harming the large satellite's mission. After that, as small satellites for business and research increased, demand for this method grew too.

A rideshare launch is a structure that shares the spare payload room and weight margin of a launch vehicle. After the main payload reaches its set orbit, the secondary payloads are released from the same vehicle through a separation device, each to its own target orbit. So the launch date and the orbit are set to fit the primary customer's mission, and the secondary customers have to follow those conditions.

Secondary payloads must meet standards for size, weight and vibration, and the order of separation must be worked out so they do not collide with the primary satellite. These design standards are standardized, so satellites from several companies can be loaded into the same standard frame.

Rideshare launches are often used for communications, Earth observation and research missions that want to put up several small satellites. It works only if there is a secondary satellite whose needs fit the primary payload's orbit, and the launch schedule can change with the primary customer's schedule.

Secondary customers find it hard to launch exactly on the date they want, and their orbit may also be limited. So when the length of the mission matters or a particular orbit is a must, a dedicated launch may suit better.

A rideshare launch has an advantage in cost, but that does not mean it is always cheap. Preparing the secondary payload to fit and going through certification take effort, and if the launch is delayed, the whole schedule can slip with it.

A common misunderstanding is that if you load many satellites, each can go freely to any orbit. In practice, the primary satellite's orbit is the standard, and the choices for the secondary satellites are limited.

It is like many people riding one bus and getting off at the stops where each needs to go. Many satellites ride on one rocket and then go their separate ways to their own orbits.

It is one of the main ways to lower the cost of space development, so it helps you understand a realistic path for small satellite companies and research institutes to start a space mission.