Many small satellites have been launched piggyback fashion alongside the larger primary payloads. On most larger launchersy liquid fuel and solid rocket boosters are added to a launcher in fixed increments until the required lift capability is exceeded.
Dummy mass is then to added to fine-tune the required orbit injection point .
Small payloads can be substituted making effective use of this mass margin, often providing a very cost effective route into orbit,however the main drawback to being a hitchhiker on a launcher is that the orbital injection point is determined by the primary payload. Small payloads have limited scope for carrying fuel for orbital manoeuvres, and so piggyback launches could be restrictive for some applications, for instance to deploy many small satellites in a constellation. In addition, most small satellites prefer LEO orbits, and the majority of launches are into GTO, further restricting the available launch opportunities. For these reasons a number of dedicated small satellite launchers have emerged and many more are under development, serving the increasing demand for critical small satellite missions requiring specific orbits. In addition the Scout launcher was developed as a dedicated small satellite launcher, although it is no longer made, and the Russian Federation Zenit and Cosmos launchers have also regularly been used, but employing ad-hoc payload accommodation.