INTRODUCTION

In early 1981, on-orbit occurrences of satellite fragmentation documented by John Gabbard at NORAD/ADCOM were correlated to breakups of Delta second stages remaining on-orbit after their mission was completed. This correlation was made by Don Kessler of NASA-JSC, and is documented in Reference 1. On 29 May 1981, McDonnell Douglas Space Systems Company (MDSSC), who design, build and launch the Delta launch vehicle, was notified by its customer, NASAGSFC, of these breakups and was tasked to determine the cause. We immediately mounted an investigation into potential causes of the breakups and corrective action to preclude their occurring on future mission hardware. Early analysis indicated a need to deplete the propellants after completing the primary mission. This was done on Delta 156, just four months later, and has been done on all subsequent Delta missions. There have been no recorded breakups of Delta second stages launched since implementing this corrective action.

VEHICLE DESCRIPTION

The Delta vehicle is flown as a two-stage vehicle for low-earth orbit missions and with a third stage for higher energy missions (i.e., GPS, GTO and escape missions). These vehicle configurations are shown in Figures 1 and 2.

The Delta vehicle stands approximately 130 feet high and weighs just over 511,600 pounds (including spacecraft) when ready for launch. The vehicle is made up of four major assemblies: (1) first stage, including the booster, solid rocket motors and interstage; (2) second stage; (3) pay load fairing; and as needed, (4) third stage.