Trajectory Design with Thrust Profile Optimization for Ascent Phase of a Hypersonic Sub-Orbital Demonstration Mission.

Paper number

IAC-07-C1.3.03

Author

Mr. Jaison Joseph, Indian Space Research Organisation (ISRO), VSSC, India

Coauthor

Dr. Swaminathan S, Indian Space Research Organisation (ISRO), VSSC, India

Coauthor

Mr. Madan Lal, Indian Space Research Organisation (ISRO), VSSC, India

Year

2007

Abstract

Renewed interest in Re-usable Launch Vehicles has led to the evolution of technology demonstration concepts, where the prime objective is to demonstrate new technologies at reduced cost and shorter turnaround time. To achieve this, new developments are to be kept to a minimum and existing hardware are to be used wherever possible. This philosophy is employed in the hypersonic re-entry demonstration mission of ISRO, where the objective is to demonstrate controlled hypersonic re-entry flight of a winged body vehicle. This mission will be accomplished in a time and cost effective manner using an existing 9-ton class solid motor, which will be used for boosting the vehicle to hypersonic Mach numbers. 
	The selected solid motor had a thrust time profile that delivers a very large impulse in a short duration. This leads to a very large dynamic pressure during ascent phase of the mission. For effective use in the demonstration mission, the thrust profile needs to be optimally reshaped so that the dynamic pressure levels are kept low, simultaneously meeting all other mission constraints. Optimization of solid motor thrust profile is a challenging proposition and not attempted so far, mainly due to mission and internal ballistic constraints.
	The objective of this paper is to demonstrate a strategy where the solid motor thrust profile and steering program are optimized simultaneously. Optimization proceeds to arrive at a solution from possible thrust time profiles, which meet ballistic constraints, concurrently achieving other mission-imposed constraints. This is formulated as a parameter optimization problem and solved with a NLP (non linear programming) solver, using direct transcription method.
	The existing thrust profile of the solid motor was of the progressive type with burn duration of around 55s. This had resulted in a peak dynamic pressure of around 300kPa during the ascent phase of the trajectory. The optimization reshaped the thrust profile to “M – type” with a burn duration of approximately 90s. This brought down the peak dynamic pressure to as low as 50kPa during the ascent trajectory. The optimized thrust profile was realizable within the internal ballistic constraints of the solid motor. 
   The strategy of simultaneously optimizing thrust profile and steering program, which enables the use of an existing hardware, proves to be a novel method to achieve technology demonstrations in a time and cost effective manner. The method presented can be further improved by directly optimizing the grain design parameters of the solid booster instead of the thrust profile.

Abstract document

IAC-07-C1.3.03.pdf

Manuscript document

IAC-07-C1.3.03.pdf (🔒 authorized access only).

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