At 7.25 am, on August 24, 2024, India achieved yet another milestone in space tech, when its first hybrid rocket ‘RHUMI’ was launched from the country’s coast. This achievement is testament to the country’s innovative spirit and paves the way for exploration of its vast potential in space science and technology.
RHUMI-1 is India’s first mobile-hybrid rocket that was successfully launched from Thiruvidanthai, on East Coast Road near Chennai.
Space Zone India, an aerospace technology firm based in Chennai, known for offering cost-effective long-term solutions in the space sector, initiated this project and completed it successfully. Anand Mahalingam, founder of Space Zone India, along with Mylswamy Annadurai, former director of ISRO Satellite Centre (ISAC) and project director and the visionary behind Chandrayaan 1, led the way towards achieving this feat.
The differences
RHUMI-1 is unique in its way that it is 100% pyrotechnic-free and 0% TNT. It is based on a generic fuel-based electric motor and has an electrically triggered parachute deployer. This way, it combines the perks of both liquid and solid fuel to improve efficiency and reduce operational costs.
The solid fuel in this hybrid rocket is used as a propellant, which is cast into a cylindrical shape and placed inside a rocket motor; while the oxidiser that is used to sustain the combustion is stored in a separate tank and fed into the combustion chamber.
But both these propellants are immobile and combust only when the fuel is converted into gaseous form and mixed with an oxidiser in the combustion chamber.
Apart from this, RHUMI-1 carried a payload of three CUBE satellites that were designed to monitor and gather information about atmospheric conditions like UV radiation, cosmic radiation intensity and air quality. The satellites that are present in this rocket will help collect all relevant data that will open doors to new research and development in this field. RHUMI-1 is also deployed with 50 PICO satellites to investigate and learn about various atmospheric factors, such as accelerometer readings, altitude and ozone levels for better understanding of environmental dynamics.
The launch
RHUMI-1, India’s first reusable hybrid rocket, is about 3.5-metres tall and weighs up to 8o kg, and was launched on Saturday, August 24, around 7.25 am. This was slightly behind the scheduled launch time of 7.00 am, according to Mahalingam, who further added that this rocket is a sounding rocket, which reached an altitude of 35 km after launch, and there was a team present to recover it from the sea since it is reusable. Though this was a short mission, RHUMI-1 returned to Earth after conducting several experiments within a limited timeframe. RHUMI is designed to travel a distance of 85 km, and the company has planned to gradually increase the current altitude to 50 km in the coming years.
During launch, there were strong gusts of wind which prompted the team to launch the rocket at 70 degrees inclination, instead of the pre-planned angle of 89 degrees. The rocket was launched using a mobile launchpad near the coast.
A brief history
The concept of hybrid rockets can be traced back to the early 1930s, when the Soviet Group for the Study of Reactive Motion led by Mikhail Klavdievich Tikhonravov designed and launched GIRD-9, on August 17, 1933, which reached an altitude of 400 metres. Tikhonravov explored the feasibility of using liquid oxidiser and solid fuel.
But during World War II, both the Allies and Axis Powers mostly engaged in making liquid-fueled and solid-fueled rockets, due to which, the development of hybrid rockets remained largely experimental.
It was in the 1940s when the California Pacific Rocket Society began to experiment with LOX (liquid oxygen), in combination with other kinds of fuel including wood, wax, and rubber. Among these, the most successful was rubber fuel, and even today, it remains the dominant fuel. The LOX/rubber rocket was launched in 1951, reaching an altitude of 9 km. Later, the organisation also conducted other experiments related to hybrid rockets, which were successful.
In the 1960s, European organisations began working on hybrid rockets. France-based ONERA and Sweden-based Volvo Flygmotor developed sounding rockets by using hybrid motor technology. The ONERA group developed a LEX-sounding rocket, and the company flew eight such rockets -- once in April 1964, thrice in June 1965, and four times in 1967, and the maximum altitude they achieved was about 100 km.
On the other hand, Volvo Flygmotor used a hypergolic propellant combination and used nitric acid for its oxidiser. It launched its hybrid rocket in 1969, which weighed about 20 kg and travelled up to 80 km.
It was in the late 20th century that the concept of hybrid rockets gained prominence in the field of commercial spaceflight. In 1998, ‘Space Dev’, a part of the space systems business in Sierra Nevada Corporation, acquired all the properties, designs and test results gathered by over 200 hybrid rocket firings from the American Rocket Company. This achievement portrayed the viability of hybrid tech for space tourism and other small-scale missions.
It was during this time that India also started showing interest in the concept of hybrid rockets. Early research focused on the potential of hybrid propulsion and its cost-effectiveness for space missions.
Today, hybrid rockets are used in various experimental and educational contexts, and even now, many are inclined towards the concept of hybrid rockets as they are cost-effective and a safer alternative to liquid-powered rockets. On that note, Space Zone India launched RHUMI-1 intending to help reduce launch costs and improve environmental sustainability.
RHUMI’s successful launch has paved the way for similar projects that will influence the future direction of hybrid rocket technology in India.
What is a hybrid rocket?
A hybrid rocket is a rocket engine that uses a combination of solid and liquid or gaseous propellants to produce thrust. The solid fuel is stored in a combustion chamber, while the oxidiser is stored in a separate tank. When the fuel is converted to gas and mixed with the oxidiser in the combustion chamber, both propellants combust.
Hybrid rockets were conceptualised in the USSR, during the 1930s. They are a relatively new addition to the space industry and are safer, more controllable and restartable. However, they suffer from some drawbacks, such as combustion inefficiency and a low regression rate.
