In its endeavour to develop cutting-edge technologies that are on par with elsewhere in the world, Indian space agency, ISRO, is developing methane-powered rocket engines. Methane, which can be synthesised with water and carbon dioxide in space, is often described as the space fuel of the future.
A senior official of ISRO told that the space agency is developing two ‘LOx methane’ engines (liquid oxygen oxidiser and methane fuel) engines. One of the two projects is trying to convert the existing cryogenic engine, which uses liquid hydrogen for fuel, into a LOx methane engine. The other is a smaller engine of 3 tonnes thrust, which will feature an electric motor. These are being developed at ISRO’s Liquid Propulsion Systems Centre at Trivandrum. The space agency’s officials are not willing to give further details, these being R&D projects and therefore could not come to fruition. Asked if ISRO’s efforts towards methane means its intention to shift away from the existing hydrazine-based fuels, the official said that he was “not making any such predictions.” ISRO currently prefers to use a fuel called Unsymmetrical Di-Methyl Hydrazine, along with Nitrogen tetroxide for oxidiser, in its liquid fuel (Vikas) engines, which are used in the lower stages of its rockets, PSLV and GSLV. This fuel, like all hydrazine-based fuels, is said to be highly toxic and cancer-causing. Globally, governments are keen on banning hydrazine. Besides, methane beats hydrazine on every other count, too. Apart from being non-toxic, it has a higher specific impulse (which means one kg of the gas can life one kg of mass for a longer time), it is easy to store, does not leave a residue upon burning, less bulky, and, importantly, can be synthesised up in space. Reactive to oxygen For example, Mars has both water on its land and water in its atmosphere — fuel for a return journey from Mars can be produced right there with these. But on the flipside, methane-fired engines need an igniter to start the fire. Hydrazine fuels are hypergolic, which means they start burning on their own upon coming in contact with oxygen. The move towards LOx methane is global, but only the Chinese are said to have developed a working engine — the 80-tonne (thrust) TQ-12 engine. Elon Musk’s company, SpaceX, is looking to make its Raptor rocket methane-fuelled. Mumbai-based start-up Manastu Space is developing a propulsion system that will use Hydrogen peroxide as fuel. The engine will be operation-ready in a couple of years, the company’s Chief Technical Officer, Ashtesh Kumar, told. Currently, Manastu’s engines are meant for steering satellites in orbit, but Kumar said that they can be scaled up to power launch vehicles. According to the company, the space industry started with Hydrogen peroxide, but moved to a ‘better’ hydrazine. But Manastu has developed a chemical additive, which it is trying to patent — the additive will enable Hydrogen peroxide to elbow hydrazine out of the competition. Meanwhile, a few other rocket fuels have emerged on the horizon — Ammonium di Nitramide in Europe and Hydroxyl Ammonium Nitrate in the US. The better fuels will make putting satellites in space or space research less expensive. The fun has just begun.