M.Sc Thesis

M.Sc StudentAnastasia Birger
SubjectSatellite Constellation for Ballistic Missile Interception
DepartmentDepartment of Aerospace Engineering
Supervisor Professor Emeritus Guelman Mauricio
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


The objective of this study is to show the possibility to use space based vehicles to engage and intercept ballistic missiles during the midcourse phase of flight. The advantage of this approach is that interception occurs far away form the intended ballistic missile target.

Interception of ballistic missiles by space based vehicles requires the analysis of a number of basic system elements. First, a feasible constellation of satellites is to be defined. The number of satellites that should be sent to space has to be as small as possible. Moreover, the size of each space vehicle should be also minimized while assuring the required constellation size. That is, total interceptor system mass should be minimized.

In order to calculate the constellation size, performance of each satellite has to be defined. In this work a nominal size interceptor model was defined to check the maneuverability and attainability domain. The most important characteristic of the space based interceptor (SBI) vehicle for constellation definition is its orbit parameters and required fuel mass. The altitude actually dictates the satellites velocity.

Using the SBI model and Pontryagin's maximum principle, the SBI reachable set was obtained. This reachable set is the volume covered by the SBI for a given amount of fuel. The nominal target trajectory defines a specific interception time interval and interception domain. The intersection of this region domain and the SBI reachable set enables the calculation of the required constellation size to achieve continuous defense. For a number of constellation altitudes it is shown that the constellation size can be as small as composed of 60 to 100 SBIs for continuous defense against a single ballistic missile.

Next, the guidance law as required by the space vehicle to successfully intercept the ballistic missile is to be proven. An engine is capable to generate only constant thrust pulses, so the guidance takes it in into account. A combined guidance law, consisting of midcourse phase and end game guidance, was proposed and checked during this study.

The design of the interception is one more important issue. The study considers the way to choose the intercept point out of the set of possible intercept points. What is the best intercept angle for this kind of interception is also one of the questions that are discussed here.