In News:

• Soon, the ISRO hopes to accomplish a remarkable feat - the 200th consecutive successful launch of the Rohini RH-200 sounding rocket.
• According to the Vikram Sarabhai Space Centre (VSSC, Thumba, near Thiruvananthapuram, Kerala), the 3.5-meter-tall RH-200, a trusted member of the Rohini sounding rocket family used by the ISRO for atmospheric studies, has completed 198 consecutive successful flights.

What’s in today’s article:

• About Sounding Rockets
• News Summary

Sounding Rockets:

• Sounding rockets are one or two stage solid propellant rockets used for probing the upper atmospheric regions and for space research.
  • Sounding in the rocket context is equivalent to "taking a measurement".
• They also serve as easily affordable platforms to test or prove prototypes of new components or subsystems intended for use in launch vehicles and satellites.
• With the establishment of the Thumba Equatorial Rocket Launching Station (TERLS) in 1963 at Thumba (a location close to the magnetic equator), there was a quantum jump in the scope for aeronomy and atmospheric sciences in India.
• The launch of the first sounding rocket (American Nike-Apache) from Thumba in 1963, marked the beginning of the Indian Space Programme.
• After that, two-stage rockets imported from Russia (M-100) and France (Centaure) were flown.

Indian Sounding Rocket Programme:

• ISRO started launching indigenously made sounding rockets from 1965 and experience gained was of immense value in the mastering of solid propellant technology.
• In 1975, all sounding rocket activities were consolidated under the Rohini Sounding Rocket (RSR) Programme.
  • Rohini is a series of sounding rockets developed by the ISRO for meteorological and atmospheric study.
  • These sounding rockets are capable of carrying payloads of 2 to 200 kgs between altitudes of 100 to 500 kms.
  • RH-75 (with a diameter of 75mm) was the first truly Indian sounding rocket, which was followed by RH-100 and RH-125 rockets.
  • The ISRO currently uses RH-200, RH-300 Mk-II and RH-560 Mk-II rockets, which are launched from the TERLS and the Satish Dhawan Space Center in Sriharikota, Andhra Pradesh.
• The sounding rocket program served as the foundation for ISRO's launch vehicle technology.

News Summary:

• RH-200 (the '200' in the name refers to the rocket's diameter in mm) is a two-stage rocket capable of reaching a height of 70 kms while carrying scientific payloads.
  • The first and second stages of RH-200 are powered by solid motors.
  • So far, the ISRO has launched over 1,600 RH-200 rockets. On July 15, 2015, the rocket completed its 100th consecutive successful mission.
  • The rocket has served as a versatile platform for experiments and the testing of new technologies over the years.
  • For many years, the RH-200 rocket used a propellant made of polyvinyl chloride (PVC).
  • In September 2020, the first RH-200 with a new propellant based on hydroxyl-terminated Polybutadiene (HTPB) flew successfully from the TERLS.
  • The 199th launch (from Thumba) will happen on October 7 during the World Space Week celebrations.
  • The 200th will take place either towards the end of October or the beginning of November.
• Sounding rockets play a significant role in the ISRO story. ISRO was taking baby steps in rocketry when the RH-200 was first introduced.
• In addition to atmospheric studies, there was a focus on aspects such as spin stabilisation and solid motors.
• Since then, sounding rockets have been used in a variety of experiments, including those investigating eclipse phenomena.