Rockets - popular examples

Launch vehicles are rockets that are used to carry satellites and other payloads into orbit. Satellite constellations are groups of satellites that work together to provide various services, such as communication, navigation, or observation. In this article, we will compare some of the launch vehicles and satellite constellations that are currently in operation or development.

LEO Satellites vs GEO Satellites

LEO stands for Low Earth Orbit. It is an orbit around the Earth with an altitude between 160 km and 2,000 km. LEO satellites have a shorter orbital period than higher orbits, which means they complete one revolution around the Earth faster. LEO satellites have advantages such as lower launch costs, lower latency (delay in communication), and higher resolution (for imaging). However, LEO satellites also have disadvantages such as shorter lifespan (due to atmospheric drag), higher orbital debris risk (due to higher density of objects), and lower coverage area. On the other hand, Geostationary satellites are satellites that orbit the Earth at an altitude of about 35,786 km and have the same orbital period as the Earth’s rotation. This means they appear to stay fixed over a point on the equator. Geostationary satellites are useful for communication, broadcasting, meteorology, and navigation purposes, as they can cover a large area of the Earth’s surface with a single satellite. However, geostationary satellites also have disadvantages such as high launch costs, high latency (delay in communication), and limited orbital slots. Some examples of geostationary satellites are GSAT series, Intelsat series, SES series, and DirecTV series.

GSAT

GSAT stands for Geostationary Satellite. It is a series of communication satellites developed by ISRO. GSAT satellites are placed in geostationary orbits (GEO), which means they orbit the Earth at the same speed as the Earth’s rotation and appear stationary in the sky. GSAT satellites provide various services,mainly telecommunication, broadcasting but also meteorology, disaster management, and navigation.

Side note: Some GSAT satellites having transponders operating in the Ku-band (10.7 GHz-12.7 GHz) are used in DTH Satellite Television. So lets digress a little and understand its evolution: In the 1980s, cable TV emerged in India using coaxial cable networks to deliver content in the VHF and UHF bands from foreign satellites like Intelsat to subscribers. Channels were received from satellites by “community antennae” which were then sent to individual subscribers via coaxial cables. Cable suffered from limited bandwidth, interference, and lack of reliability.

In the 2000s, DTH satellite services were launched. Here the “community antenna” was replaced by personal dish antenna in each subscriber’s roof/home. It uses the Ku-band (10.7 GHz -12.7 GHz) to provide higher quality digital TV signals across the country, with each TV channel taking roughly 6 MHz spacing. Services like Tata Sky, Dish TV, and Airtel Digital TV leased transponders on Indian satellites Insat 4A and GSAT-15 to broadcast hundreds of channels. DTH provided wider coverage but still relied on linear live channels. Doordarshan also provided some limited no. of free channels using the GSAT-10 satellilte through its DD Direct+ Dish Antenna.

Recently since 2016, OTT streaming platforms have transformed TV using broadband internet in the WiFi (2.4 GHz) and mobile bands (1-2 GHz). Services like Hotstar, Prime Video, and Netflix source content globally and host it locally, leveraging cloud infrastructure from providers like AWS. Accessing OTT via apps on smart devices, streaming delivers an on-demand experience.

While DTH uses powerful satellites at 93.5°E and 83°E orbital slots, OTT relies on content delivery networks with edge locations in major cities. DTH provides 200+ standard definition and high definition channels, while OTT is uncapped, offering thousands of hours of on-demand content.

Starlink & OpenWeb

Starlink is a satellite internet constellation operated by SpaceX, which aims to provide low-cost internet to remote locations. As of November 2022, Starlink consists of over 3,580 mass-produced small satellites in low Earth orbit (LEO), which communicate with designated ground transceivers1. The satellites operate at different altitudes depending on their orbital shell. OpenWeb is a proposed satellite internet constellation by OneWeb, a British company. OpenWeb plans to deploy about 650 satellites in LEO at an altitude of 1,200 km to provide global broadband connectivity. As of November 2022, OpenWeb has launched 322 satellites out of the planned initial constellation.

Launch Vehicles

Soyuz

Soyuz is a family of expendable launch vehicles developed by Russia and the former Soviet Union. Soyuz can launch up to 8,200 kg of payload into LEO or up to 3,250 kg of payload into GTO. Soyuz uses four stages: a core stage with four strap-on boosters, a second stage, a third stage, and a payload fairing. Soyuz uses kerosene and liquid oxygen as propellants for the first three stages, and solid propellant for the fourth stage. Soyuz has been used to launch various payloads for Russia and other countries, such as Progress spacecraft, Soyuz spacecraft, GLONASS satellites, Galileo satellites, and O3b satellites. Soyuz is also the only launch vehicle that can carry crew to the International Space Station (ISS). The first flight of Soyuz was in 19662.

PSLV

PSLV stands for Polar Satellite Launch Vehicle. It is a four-stage launch vehicle developed by ISRO. It can launch up to 1,750 kg of payload into Sun-synchronous polar orbits (SSPO) of 600 km altitude. The first and third stages use solid rocket motors, while the second and fourth stages use liquid rocket engines. PSLV has been used to launch various satellites for India and other countries, such as Chandrayaan-1, Mars Orbiter Mission, Cartosat series, IRNSS series, and RISAT series. The first flight of PSLV was in 1993.

GSLV MkIII

GSLV MkIII stands for Geosynchronous Satellite Launch Vehicle Mark III. It is a three-stage launch vehicle developed by ISRO. It can launch up to 4,000 kg of payload into GTO/GEO. The first stage uses two solid rocket boosters while the second stage uses a liquid rocket engine. The third stage uses a cryogenic rocket engine that uses liquid hydrogen and liquid oxygen as propellants. GSLV MkIII has been used to launch India’s heaviest satellite GSAT-19, India’s second lunar mission Chandrayaan-2, and India’s first manned space mission Gaganyaan (planned for 2023). The first flight of GSLV MkIII was in 2014.

LVM3

LVM3 stands for Launch Vehicle Mark 3. It is another name for GSLV MkIII, but its meant for LEO & not GEO. LVM3 is also known as Bahubali, meaning “the one with strong arms” in Sanskrit. LVM3 is India’s most powerful launch vehicle built to lift satellites weighing up to 4 tons into GTO or about 10 tons to LEO.

Falcon 9

Falcon 9 is a two-stage reusable launch vehicle developed by SpaceX. It can launch up to 22 tons of payload into LEO or up to 8 tons of payload into GTO. The first stage uses nine Merlin engines that use liquid oxygen and kerosene as propellants. The second stage uses one Merlin engine that uses liquid oxygen and kerosene as propellants. Falcon 9 is designed to be reusable, meaning that the first stage can land back on Earth after launch and be reused for future missions. Falcon 9 has been used to launch various payloads for SpaceX and other customers, such as Dragon spacecraft, Starlink satellites, GPS satellites, NROL-76 spy satellite, and DSCOVR climate satellite. The first flight of Falcon 9 was in 2010.

Falcon Heavy

Falcon Heavy is a heavy-lift launch vehicle developed by SpaceX. It is essentially three Falcon 9 first stages strapped together with a second stage on top. It can launch up to 63 tons of payload into LEO or up to 26 tons of payload into GTO. The first stage consists of three cores that use nine Merlin engines each that use liquid oxygen and kerosene as propellants. The second stage uses one Merlin engine that uses liquid oxygen and kerosene as propellants. Falcon Heavy is designed to be partially reusable, meaning that the three cores can land back on Earth after launch and be reused for future missions. Falcon Heavy has been used to launch various payloads for SpaceX and other customers, such as Arabsat-6A communication satellite,

Starship

Starship is a fully reusable launch vehicle and spacecraft system developed by SpaceX. It consists of two stages: a “super heavy” booster and a “starship” upper stage (spacecraft). Starship can launch up to 100 tons of payload into LEO or up to 21 tons of payload into GTO. Starship uses 37 Raptor engines that use liquid oxygen and liquid methane as propellants. Starship is designed to be versatile, meaning that it can carry crew and cargo to various destinations, such as the moon, Mars, and beyond. Starship is also designed to be refueled in orbit, enabling long-duration missions. Starship is the successor of Falcon 9 and Falcon Heavy, and will eventually replace them. Starship has been used to perform several high-altitude flight tests, but has not yet reached orbit. The first orbital flight test of Starship is planned for 2023.