Complex sentence: A safety margin would be provided simply due to the extra lifting strength that would be required by the system to raise large payloads to orbit during routine operation; in an emergency, payloads in transit could be jettisoned from the tower to reduce tower loading.
Split into simpler sentences: A safety margin would be provided simply due to the extra lifting strength that would be required by the system to raise large payloads to orbit during routine operation. In an emergency, payloads in transit could be jettisoned from the tower to reduce tower loading.