Agnikul showcased more than ‘rocket science’
On May 30, Indian space start-up Agnikul Cosmos demonstrated its proficiency in 3D-printed rocket engine technology with its successful launch of a suborbital flight of its Agnibaan rocket from its own launchpad at ISRO’s Satish Dhawan Space Centre in Sriharikota. Agnikul is a start-up incubated in the National Centre for Combustion R&D at IIT-Madras. It plans to develop and launch its own small-lift launch vehicle able to carry a 100-300 kg payload into a 700-km high low-earth orbit (LEO).
With the launch, Agnikul became only the second Indian private company to do a sub-orbital space launch, after Hyderabad-based Skyroot Aerospace, which launched its Vikram-S rocket in November 2022. Skyroot is expected to take the next step – of launching a rocket into orbital space later this year; Agnikul plans to do so in 2025.
The Agnikul launch was unique in many ways. The Agnibaan SOrTeD (Sub-Orbital Technology Demonstrator) launch was the first Indian launch from a private launchpad. It had the world’s first single-piece 3D-printed rocket engine. And it was a semi-cryogenic engine, a difficult technology to master and one that even ISRO is still in the process of developing.
ISRO, of course, developed fully cryogenic engine technology indigenously after a long effort. Its first successful launch with an indigenous cryogenic engine was in January 2014 (GSLV-D5/GSAT-14 mission). Cryogenic engine development is technically a very complex process. It uses propellants (oxygen and hydrogen) at extremely low temperatures. Oxygen liquifies at -183 deg C and Hydrogen at -253 deg C. Apart from handling these propellants at such low temperatures, there are additional challenges associated with thermal and structural difficulties.
During the early 1990s, Russia was to transfer this technology to India. However, there was fear in the minds of the Bill Clinton administration in the US that India could use this technology for long-range missile development and stopped Russia from transferring the technology. It has been reported that the current US President Joe Biden, who was then a senator, played a crucial role in denying this technology to India. India’s heavy satellite launch vehicle programme (GSAT series) suffered significantly due to this. The next stage in this programme is the development of a semi-cryogenic engine. This engine will utilize a propellant combination of Liquid Oxygen (LOX) and Kerosene. It is expected that ISRO will test this technology soon.
Not many technical details are available about the Agnikul semi-cryogenic engine programme. However, it needs to be mentioned that this private start-up aims to launch small/mini satellites (mass between 100 and 300 kg) into LEO, while ISRO is working towards developing semi-cryogenic technology to put satellites of 8-10 tons class into geostationary (36,000 km above the earth’s surface) orbit. It is also important to mention that to put heavy satellites (weighing up to 5 tons) in LEO, ISRO uses a vehicle called LVM3 (Launch Vehicle Mark-III), whose upper stage is cryogenic.
With this launch, Agnikul has achieved a major milestone in using additive manufacturing (3D printing) technology to design and build a rocket engine. This is the first-ever controlled flight of a semi-cryogenic liquid engine accomplished through 3D printing. For some time now, a few space agencies have been using 3D printing technology in the space domain. Even on the International Space Station (ISS), some routinely required parts are produced using 3D printing technology. Space agencies have been known to use 3D printing to produce engine parts and assemble them later. However, Agnikul 3D-printed its entire engine as a single piece. This process cuts the manufacturing cost and reduces the time required for vehicle assembly.
Some important experiments have been done in the last few years in 3D-printing entire rockets and spacecraft. The US company Relativity Space has been developing such systems since 2017. In March last year, it undertook an orbital launch of its Terran-1 vehicle. This was an expendable two-stage, small-lift launch vehicle with a majority of its components being 3D-printed. However, Terran-1 failed during the second stage. Presently, Relativity Space is working to develop a much larger, reusable vehicle called Terran-R. 3D printing technology has a great future in the space domain.
Today, companies are even undertaking experiments in using this technology to build infrastructure on the Moon and Mars. Presently, in earth-based facilities, this technology shows promise in enabling on-demand production of rocket and satellite components.
Agnikul is planning an orbital mission by the end of 2025. It has developed a mobile launchpad, called Dhanush, which gives it flexibility in terms of where it launches from. With proven technologies like 3D printing and semi-cryogenic engines, the company should be able to offer among the lowest cost satellite launch options for lower orbits.
(The writer is Deputy Director-General, MP-IDSA, New Delhi)