ISRO’s Heaviest Launch: BlueBird Block-2

• 26 Dec 2025

Source: IE 

Why in News? 

ISRO marked a major milestone by launching its heaviest satellite, BlueBird Block-2 (6,100 kg, by the US firm AST SpaceMobile), using the Launch Vehicle Mark-3 (LVM3) rocket, showcasing India’s strong heavy-lift launch capability. 

Summary 

• BlueBird Block-2, weighing 6,100 kg, is the heaviest payload deployed by ISRO, injected into LEO (160 - 2,000 km) to provide direct-to-mobile 4G/5G connectivity. 
• LVM-3 upgrades, including C32 cryogenic stage, semi-cryogenic engines, and bootstrap reignition, enhancing its payload capacity. 

What is BlueBird Block-2? 

• About: The BlueBird Block-2, is the heaviest payload ISRO has placed into orbit, surpassing the previous record of 5,700 kg (OneWeb satellites).  
  • The satellite was injected into a Low Earth Orbit (LEO) of approximately 520 km altitude. 
• Objective: It will provide direct-to-mobile connectivity, enabling 4G and 5G connectivity directly to mobile phones without requiring specialized ground stations. 
• Commercial Significance: This is ISRO's 3rd commercial mission using LVM-3, following two OneWeb satellite launches in 2022 and 2023.  
  • Despite global alternatives like SpaceX’s Falcon-9 and the ESA’s Ariane 6, the LVM-3 underscores ISRO’s capacity for heavy launches at much lower cost. 

Low Earth Orbit (LEO) 

• Overview: LEO extends from about 160 - 2,000 km above Earth’s surface, where satellites complete an orbit roughly every 90–120 minutes. 
• Satellites in LEO: It hosts satellites used for communications, Earth observation, scientific missions, and navigation. 
• Orbit Types: While many LEO satellites follow circular orbits, some operate in elliptical orbits. 
• Special Elliptical Orbits: Molniya and Tundra orbits provide longer dwell times over high-latitude regions and are used for communications and observation where geostationary coverage is limited. 

What is the LVM3 Launch Vehicle? 

• About: The LVM3 is ISRO's largest and most powerful heavy-lift rocket, with three stages. This rocket can carry payloads of up to 4,000 kilograms to Geosynchronous Transfer Orbit and 8,000 kg in LEO. 
  • Previously called the Geosynchronous Satellite Launch Vehicle Mk III, it launched for the first time in December 2014. 
• 3 Stages:  
  • First Stage: Uses two large S200 solid rocket boosters, which burn solid propellant HTPB (hydroxyl-terminated polybutadiene). 
  • Second Stage (Core): Uses liquid-fuelled stage, powered by two Vikas engines, burning UDMH (unsymmetrical dimethylhydrazine) and nitrogen tetroxide. 
  • Third Stage (Upper): Uses the C25 cryogenic stage,, equipped with the CE20 engine, burning liquid hydrogen and liquid oxygen. 
• Engine Optimization for Higher Efficiency:  
  • Cryogenic Stage Upgrade: ISRO is developing the C32 cryogenic stage for higher thrust and fuel capacity.  
  • Semi-Cryogenic Engine Development: ISRO  is developing semi-cryogenic engines using kerosene and liquid oxygen, which will raise LEO payload capacity from 8,000 kg to 10,000 kg. 
  • Bootstrap Reignition Technology: ISRO is developing bootstrap reignition capability for cryogenic engines, allowing the upper stage to restart without external gases like helium, reducing fuel weight and increasing payload capacity for multi-orbit missions. 
• Role in Future Missions: A modified LVM-3 with added human-safety redundancies will support Gaganyaan missions and later carry modules for the Bharatiya Antariksh Station, India’s planned space station. 

Frequently Asked Questions (FAQs) 

1. What is BlueBird Block-2? 
BlueBird Block-2 is a 6,100 kg commercial satellite by AST SpaceMobile, providing direct-to-mobile 4G/5G connectivity in LEO (160 km to 2,000 km). 

2. What is the significance of LEO? 
Low Earth Orbit (LEO) hosts communication, Earth observation, and navigation satellites, enabling low-latency global connectivity. 

3. What are the stages of the LVM-3 rocket? 
LVM-3 has three stages: S200 solid boosters, L110 liquid-fueled core, and C25 cryogenic upper stage, optimized for heavy-lift missions. 

UPSC Civil Services Examination, Previous Year Question (PYQ)  

Q. With reference to India’s satellite launch vehicles, consider the following statements: (2018)

1. PSLVs launch satellites useful for Earth resources monitoring whereas GSLVs are designed mainly to launch communication satellites. 
2. Satellites launched by PSLV appear to remain permanently fixed in the same position in the sky, as viewed from a particular location on Earth. 
3. GSLV Mk III is a four-stage launch vehicle with the first and third stages using solid rocket motors, and the second and fourth stages using liquid rocket engines. 

Which of the statements given above is/are correct?  

(a) 1 only 

(b) 2 and 3 

(c) 1 and 2 

(d) 3 only 

Ans: (a)

Q. In which of the following activities are Indian Remote Sensing (IRS) satellites used? (2015)

1. Assessment of crop productivity 
2. Locating groundwater resources 
3. Mineral exploration 
4. Telecommunications 
5. Traffic studies 

Select the correct answer using the code given below: 

(a) 1, 2 and 3 only  

(b) 4 and 5 only 

(c) 1 and 2 only  

(d) 1, 2, 3, 4 and 5 

Ans: (a)