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DALBIT-1, a miniature-sized, fully integrated, Earth-based lander test bed was designed and developed for the vertical takeoff and vertical landing flight demonstration. Mission and design requirem...

This paper proposes an integrated framework for staging and trajectory optimization of a launch vehicle under a constraint on the instantaneous impact point (IIP) of the separated stage. The proposed framework iterates between the optimal staging module and the trajectory optimization module to minimize the lift-off mass of a launch vehicle for a given payload mass. The trajectory optimization module finds the velocity losses and velocity change for IIP control, which flow to the optimal sizing module as inputs. The iteration between the two modules continues until the convergence criteria are satisfied. The effectiveness of the proposed framework has been demonstrated through a case study.

This paper proposes a procedure for managing the risk of reentering space objects and risk assessment methodologies used for the process. The proposed procedure comprises three phases encompassing the whole reentry stages of space objects. Mathematical models for assessing the impact risk of the reentering space objects by utilizing the information available during different risk management phases and the recommended risk analysis results for public communication are presented. The concept of the conditional casualty expectation is proposed as the metric representing the reentry risk and the method to compute its profile is introduced. A case study on the risk management procedure with the dataset on an actual reentry event is conducted to demonstrate the efficacy of the proposed procedure.

This study proposes an algorithm to calculate fast the predicted intercept point (PIP) of the anti-ballistic missile system. A neural network system is trained to learn the motion of the ballistic target to predict the future target position. Then a prediction algorithm iteratively calculates PIP and the launch time of the interceptor. PIP calculation enables the missile to effectively approach to the ballistic target. Computer simulations using simple interceptor models are conducted, demonstrating the usefulness of the proposed PIP determination algorithm. The proposed algorithm significantly reduces the computation time required for target trajectory prediction in real-time.

This paper proposes a two-phase framework to predict the impact dispersion area of a reentering space object. A semi-analytic approach is developed that predicts the dispersion area by combining an analytic impact point sensitivity model with corrections to account for aerodynamic drag. The first phase of the framework (preparation phase) generates a database storing the coefficients used in the correction model; this applies the least-squares method to the results of numerical experiments on the space object reentry for various initial states (position and velocity) and aerodynamic characteristics (i.e., ballistic coefficient). The second phase (execution phase: during the reentry event) predicts the dispersion area of the falling object using the correction coefficients database generated in the preparation phase. The validity and computational efficiency of the proposed method are demonstrated through a case study.

This paper proposes a noniterative feedback midcourse guidance algorithm for intercepting a ballistic target. The virtual impact point (VIP) concept, which is the intersection point between the defense missile trajectory and the sphere defined by the hit altitude, is introduced. Then the motion of the virtual impact point caused by the external acceleration applied to the missile is derived. The proposed guidance algorithm generates the acceleration command that moves the VIP to the PIP along the shortest path without any iterative procedure and has high potential as an onboard midcourse guidance algorithm. The validity of the proposed guidance algorithm has been demonstrated through the case study.

This paper proposes an optimal staging method for reusable launch vehicles considering velocity losses. The proposed method expands a traditional stage optimization approach for expendable launch vehicles by introducing the descent phase of the separated stage and combining it with the trajectory optimization procedure. For a reusable stage, the structural ratios responsible for its ascent and landing phases are defined to formulate the optimal sizing problem and optimized along with variables for traditional staging problems. An optimal staging case study on a reusable launch vehicle demonstrates the effectiveness of the proposed method.

A new analytic formulation to express the time derivatives of the instantaneous impact point (IIP) of a rocket is proposed. The geometric relationship on a plane tangential to the IIP is us...

This paper proposes a feedback guidance law to move the instantaneous impact point (IIP) of a rocket to a desired location. Analytic expressions relating the time derivatives of an IIP with the external acceleration of the rocket are introduced. A near time-optimal feedback-form guidance law to determine the direction of the acceleration for guiding the IIP is developed using the de-rivative expressions. The effectiveness of the proposed guidance law, in comparison with the results of open-loop trajectory optimization, was demonstrated through IIP pointing case studies., Total 22 pages, 11 figures, submitted to Aerospace Science and Technology