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India's LVM3 to launch the final Gen-1 satellites of OneWeb constellation

Updated: Mar 26, 2023

By completing the constellation, the company is taking a pivotal step forward in delivering global coverage.

LVM3 M3 at SLP

The Indian Space Research Organization's (ISRO) heaviest carrier rocket; LVM3 number M3, will launch thirty-six broadband satellites from British start-up OneWeb from the second launch pad in Sriharikota spaceport on India's east coast near Chennai.

This will be OneWeb’s eighteenth launch to-date and its third this year, completing its first generation LEO constellation, and enabling the company to initiate global coverage in 2023.

The launch is scheduled for March 26, 2023 at 03:30 UTC / 04:30 BST / 09:00am IST. The OneWeb satellites will be placed in an orbit inclined at 87.4° to the equator. The 643-ton rocket will take off pointing to a launch azimuth of 176.3°, then perform a 'dog-legged' maneuver to the south and assume the desired tilt "~138°, to avoid flying over Sri Lankan airspace.

Launch Infographics

NewSpace India Limited (NSIL), a company under the Space Department and the commercial arm of ISRO has signed two launch service contracts with M/s Network Access Associated Limited (OneWeb India Communications Ltd.), for the launch of the broadband communication satellites aboard the LVM3 launcher (previously called GSLV-Mk3). It is the first commercial release of LVM3 on demand through NSIL. This agreement with OneWeb is a historic milestone for NSIL and ISRO as the heavy Bahubali (“Stronger Boy”) rocket is entered the global market for commercial launch services since October 2022. OneWeb is a global communications network from space, enabling connectivity for governments, businesses, and communities, and is deploying a constellation of low earth orbit satellites. India's Bharti (Includes Bharti Airtel) firm acts as a major investor and shareholder in OneWeb.

36 OneWeb Satellites enclosed in Fairing (ISRO)

ISRO changes material color of C25 stage

For the first five launches of the LVM3 rocket, ISRO had been using a grey/black insulation material for the C25 stage and currently that material has been coated with a white.

LVM3 M3 vs M2

The C25 stage is a cryogenic stage, which comprises a cryogenic engine and fuel tanks that hold tons of super-chilled fuel and oxidizer — liquid oxygen and liquid hydrogen, along with its avionics systems. Engineering a cryogenic stage has unique design challenges, as liquid Hydrogen is stored at -253 degree centigrade and liquid Oxygen at -195 degree centigrade. To store these cryogenic fluids and maintain them at supercooled temperatures, special multi-layer insulation is provided for the fuel tanks and other structures.

C25 stage

To understand the science behind the color change has a simple thermal properties, says

Dr S. Unnikrishnan Nair, Director, Vikram Sarabhai Space Centre (VSCC) which is ISRO's lead facility for developing its operational rockets and future space transportation systems.

A rocket specialist with significant contributions towards launch vehicles and manned vehicle systems, Dr Nair explained that the reason behind the color change takes into account environmental-friendly manufacturing processes, better insulation properties and the use of lightweight materials.

"The previous insulation materials of C25 stage was based on Hydrochlorofluorocarbon (HCFC), which has its environmental concerns, we have decided and switched to greener alternatives based on chemicals such as Hydrofluoroolefin(HFO)," said Nair.

HCFCs are globally regarded as unsafe as they contain chlorine and have the potential to deplete the ozone layer. Owing to this, there are certain manufacturing caps on this material and ISRO is avoiding its use.

Regarding the grey/black color being replaced with white, he added that the earlier anti-static coating (meant to prevent a build-up of static electricity) has been replaced with a white one. He reasoned that this was owing to solar absorptivity, as dark colors like black attract a lot of heat and affect the temperature of the cryogenic fuels.

Nair also explained that it is not easy to add an extra coat of paint or extra layer of material to a rocket's upper body, as every kilogram of weight comes at a premium.

Every added component or layer of coating/paint adds to the rocket's weight and affects the vehicle's payload-carrying capacity. So, we have to keep in mind the science, the utility and also the environmental aspects. Hence, it takes time to develop new materials that are lightweight, suited for the purpose and at the same time cost-effective and environment-friendly.

OneWeb Gen-1 Satellites of M/s. Network Access Associates

This is OneWeb’s 18th launch, its third this year, bringing the total of OneWeb’s constellation to 618 satellites. This launch is a major milestone for the company, with the number of satellites now in-orbit enabling global service, the first LEO operator to reach this milestone. OneWeb will soon be ready to roll out its global coverage.

LVM3 M3 Flight Profile

LVM3 M3 OneWebL18 Deployment phase

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