Special Sessions

Abstract

1. Guidance & Control of Launch Vehicles and STS: Dr. Gopal Jee, GD, CGDG, VSSC
2. Actuators Sensors and Robotics for Space Applications: Dr. Biju Prasad B, GD, CASG, VSSC
3. RF Systems for Launch Vehicles: Shri. Lal M J, Group Director, RFSG/AVN, VSSC
4. Avionics Fabrication Techniques: Smt. Sheena Abraham, Group Director, EPG, VSSC

• Guidance & Control of Launch Vehicles and STS:
  Reusable launch vehicle (RLV) is being developed by ISRO, where it is envisaged to recover both booster and upper stage of a space transportation system (STS). Booster is recovered using propulsion system whereas upper stage recovery is assisted by aerodynamics along with propulsion system. Guidance and control are the two essential components of onboard software which provides complete autonomy to the reusable launch vehicle. Guidance is the path planner algorithm, ensuring RLV’s safe ascent to the orbit, de-boost, re-entry and landing on a runway. Control works as an autopilot, ensuring the safety of the vehicle while steering it towards the targeted location decided by the guidance algorithm. To get complete reusability, various experimental flights are being carried out by us. We have achieved the mastery in launching the RLV to high altitude (HEX mission – Hypersonic re-entry experiment) using booster, landing it on a runway (LEX experiment – Landing experiment). Capability of taking the RLV to the orbit and re-entering into the Earth’s atmosphere (OREX – orbital re-entry experiment), without violating structural and thermal loads is being developed. Pinpoint landing of the booster is planned in near future. Brief description of plant modelling of rotational and translational dynamics, autopilot and guidance design will be covered in this talk. Glimpse of experiences gained during the journey of development of RLV will be given during the presentation.      
• Actuators Sensors and Robotics for Space Applications: 

  Actuators are used for the control and guidance in satellite launch vehicles. This can be achieved through thrust vector control by deflecting the liquid engine and solid motor nozzles, injecting high density fluid into the supersonic exhaust jet or deflecting the external fins during the aerodynamic phase of the mission. Actuators are also used to control the mixture ratio of fuel and oxidiser to maintain optimum propellant outage or alter the engine thrust. Since these are mission critical operations, a very high level of reliability and fault tolerance is required. This is achieved by introducing redundancy in its critical elements and maintaining a rugged fault detection isolation and reconfiguration system.  Space robotics is a niche area which finds lot of application in interplanetary exploration, unmanned missions of orbital vehicles and in space stations for repair, maintenance and conducting experiments. These robotic systems should not only be designed to survive launch loads and harsh environments expected in space and interplanetary missions but also possess artificial intelligence to respond to unseen situations.  In space stations, humanoids can conduct series of experiments and assist in cargo transfer and maintenance operations. With the tremendous advancements happening in AI ML area, space robotics has the potential to accelerate space exploration without risking the human life. 

• RF Systems for Launch Vehicles:

  RF Systems in Launch Vehicles can be grouped into Telemetry, Tracking and Tele-command systems.  Functional requirement of telemetry systems is to acquire telemetry data pertaining to the vehicle performance and satellite injection parameters. All launch vehicles are inherently explosion prone whenever they contain fuel or oxidizer, or explosive devices are installed, or toxic chemicals or high-pressure gasses are on board. There is requirement to track all rocket systems during their ascent from the ground to low earth orbit, and terminating any flight before it poses a hazard to lives or property. Tracking and Tele-Command System forms an important part of System for terminating the flight for Range Safety. Vehicle instantaneous position should be known with high accuracy in real -time. Based on tracking data, coded sequence should be sent to launch vehicle, decoded onboard for command execution as per the issued command from the ground. The position of launch vehicle can be computed using either Radar Tracking, Inertial Navigation System or GPS/NaViC Based systems. Radar tracking is an independent system. Data from Inertial Navigation System or NaVIC system is collected though launch vehicle Telemetry.

• Avionics Fabrication Techniques:

  Avionics package Life Cycle starts with Launch Vehicle Project Requirements.  Based on mutual discussion and compromise between Design team and Project team, Conceptual design will be made.  Specifications will be generated and preliminary design will be arrived at block diagram level.  The preliminary design has to undergo all reviews and once the circuit is finalized, Printed Circuit Board (PCB) layout design is made. After getting clearance for all design as well as Quality Control aspects, the PCB will be fabricated.  The inputs for the fabrication of Avionics packages are Components, PCBs and Mechanical chassis.   The PCB will be wired with components or electronic parts by means of Reflow soldering operation and Manual soldering.  After wiring the card is ready for testing. It will undergo all testing to check whether the original specifications whatever aimed is met and whether all project requirements are met. The different tests are Initial Standard Room Conditions Test (ISRC), Thermal tests (Hot and Cold soak), Vibration, Shock EMI, Vacuum test, Final Standard Room Conditions Test (FSRC. There are two tpes of tests like Qualification tests to establish design margin and Flight acceptance tests to bring out workmanship defects. After obtaining all clearances, a Configuration Controlled Document (CCD) will be released. There is an approved CCD for each package. Once the package fabrication and testing is streamlined, the production can be outsourced to external industries after accreditation and proper enabling. Electronic devices are shrinking in size and increasing in complexity due to improvements in VLSI technology. Miniaturized Avionics packages are the need of the hour for space applications. For that miniaturization technologies like Hybrid Microcircuit technology, Surface Mount Technology and 3D packaging technologies are used.  All these will be addressed briefly in the presentation along with some case studies.