A rocket backpack system can help a soldier cross harsh terrains at high altitudes.
India shares a large tract of mountainous borders with multiple countries, manning which is a nightmare for the army. Not only is it difficult to build roads at high altitudes, but the army also has to contend with landslides and avalanches while traversing on these roads. Naturally, one thinks, “Why not fly rather than go from one place to another on the ground?”
Yes, we are talking about jetpacks – devices worn on the back that allow a single user to fly by means of propulsion produced by rapidly expelled gases.
Jetpacks are for real now but they are nothing close to the kind you see in science fiction movies. They have been used only for ceremonial purposes and no armed force in the world currently uses it. We talk to Major Lakshyajeet Singh Chauhan, an engineer in the Indian Army, about his research project on developing a rocket backpack motor for the Indian Army.
Maj. LS Chauhan details the hardships faced by the Indian Army in remote locations through his own experience of working in the army for 9 years. He says, “I was posted in the Siachen glacier as part of my infantry attachment. We used to witness sudden snowfalls and all the routes used to be blocked for days at a stretch. It is impossible to and a helicopter at such altitudes. If someone was ill, there was no way you could take him out of there in such conditions.” He goes on to say that due to ruthless weather, he had to spend a much longer time at the Siachen than he was designated to.
Jetpacks can be a real boon for the Indian Army. One can go to remote places without any hassle. Consider the same example of the Indian Army guarding mountain borders. If a couple of people in a company can fly, they can build a ropeway between the cliffs of two mountains, instead of the entire company coming down and climbing up again. The time taken to go from one peak to another is reduced. With this idea in mind, Maj. LS Chauhan started his M.Tech. project at IIT Madras. He discussed it with his guide Prof. PA Ramakrishna from the Department of Aeronautical Engineering, who agreed to work with him on this and give him the required guidance. Prof. Ramakrishna explains, “It is more like this… if you see monkeys climbing trees to get at the fruit, you will observe that they will first climb one tree and jump from one tree to another. People working in such fields do the same. It is possible in this terrain too. It is basically the same thing. One somehow manages to climb one peak and uses that advantage to go to another. This was the idea with which we started this work.”
Rocket backpacks have been around for sometime now but they have been only used for fun and recreation. They have a very low flight time and can just about carry a person. This project aims to build a portable one that can carry a soldier and his equipment. There was an attempt by Bell Helicopters to make one such device for the US Military. They built a device called the Bell Rocket Belt which was eventually rejected because it was expensive and there was no scope for carrying payload.
Let us take apart the rocket used in a jetpack. In the simplest terms, a rocket has a combustion chamber in which fuel comes in contact with a chemical called the oxidiser that helps the fuel burn. The burning of the fuel and the oxidiser controls the thrust. Controlling this thrust is crucial to control the motion of the person wearing the rocket backpack. Initially, for one to go up, the thrust has be greater than the pilot’s weight. And when the same person has to come down, he has to reduce his thrust so that it is less than his weight.
The type of fuel and oxidiser involved is used to classify the rocket. For example, in a liquid rocket, both the fuel and oxidiser are liquids while in a solid rocket, both of them are solids. The liquid rocket used in the Bell Rocket Belt had Hydrogen peroxide as its oxidiser which was hard to handle since it was explosive and ate through metal.
Maj. LS Chauhan and Prof. Ramakrishna were looking for something more benign than that. They wanted hybrid rockets to do the job for them. Such rockets have a liquid oxidiser and a solid fuel. Their primary advantage is that you can control the flow rate of oxygen and get the thrust level you require. This feature also exists with liquid rockets but not with solid rockets. But it is easier to control thrust in hybrid rockets than in liquid rockets as only one out of the fuel or the oxidiser is a liquid.
Moreover, hybrid rockets are known to be very safe. Prof. Ramakrishna’s lab has been working on them for over 10 years now. They have conducted over 2000 experiments on them without any mishaps. It is important to take safety into consideration when there is a human being on the other side. They plan to use water as the oxidiser in this system as it is not only very safe but also readily available.
Maj. LS Chauhan compares his experiences of working in the army with that of working on the research project.
He says that he was only doing a maintenance job in the army. After joining academia, he had to put his mind back into the thinking mode. He describes his experience of working for 8-9 months on something new and innovative as wonderful. The work was as strenuous as the army where he had to spend 70-80 hours every week. Yet, he says that he did not really mind working long hours as the work was very interesting. He feels that failure is a part of research. “Even though I put in my best efforts, something or the other kept going wrong. Sometimes, I thought I was on the wrong track. But, I kept going and eventually finished the propulsion part of the project and even designed the combustion chamber for the rocket backpack motor.” The different stages of the project are illustrated through the flowchart below.
He also acknowledges the need for a good mentor in a research project with the following words: “My professor helped me out a lot. Only the idea was mine. Most of the thinking and the design was done by him. I was only following his instructions.” One might ask the following question: “Bell Helicopters was a large organisation developing the rocket belt. How can a few students in the lab do it?”, to which Prof. Ramakrishna has a ready reply. “There are no technical difficulties associated with the project. We do have all the technology to develop it. Only its implementation and engineering within the weight budget and safety considerations is hard. All these things need to be taken care of and the product needs to be brought out.”
As a consequence of Maj. LS Chauhan’s work, the proposal of inclusion of the project under the Army Technology Board has been forwarded by the Military College of EME, where Maj. LS Chauhan is posted currently, to IIT Madras. This collaborative project worth Rs. 50 lakhs is expected to start in January 2016. It aims to develop a rocket backpack system capable of carrying a soldier for at least one minute at a cruise speed of 80 km/hr. All this needs to be done within a budget of Rs. 15 lakhs per backpack to ensure that the large requirement for such backpacks can be met at a reasonable cost.
Despite the availability of advanced technology and the required funding, the main challenge of the human body not being adapted to fly naturally remains an obstacle in this endeavour. The jetpack must accommodate for all factors of flight such as sufficient lift and to some extent, stabilisation. And, of course, the soldier operating the jetpack must be taught to fly it.
In conclusion, Maj. LS Chauhan wishes to give the following message to the students: “I wish good engineers and scientists would stay in India and work for the country instead of going abroad just for the sake of a higher pay. Being Indians, we should not leave our country. The joy of getting a fat paycheck is nothing compared to the satisfaction derived from serving the country, say by working in the army. My dear Indians, please stay back, work for the development of India and make it a strong and developed country.”
Major Lakshyajeet Singh Chauhan was an M.Tech. student (2013-2015) in the Department of Aerospace Engineering at IIT Madras. Before his Masters, he worked for 9 years for the Indian Army and was posted in Siachen and Kargil, among other places. He is currently an instructor in the Faculty of Aeronautical Engineering at the Military College of Electronics and Mechanical Engineering, Secunderabad.
Prof. PA Ramakrishna obtained his PhD from the Indian Institute of Science, Bangalore and joined IIT Madras in 2005. Currently, he is working as a Professor in the Department of Aerospace Engineering. His research interests are in aerospace propulsion, especially, solid and hybrid propellant combustion.
Sachin Nayak is a final year B.Tech. student of the Department of Electrical Engineering at IIT Madras. He loves microcontrollers, coding, swimming, running and, of course, reading and writing. He has been part of several organisations in the institute like the CFI Electronics Club, The Fifth Estate, Shaastra, etc. He plans to pursue graduate studies in Computer Science in the near future
Cover image : Representative image of a person operating a rocket backpack, Wikimedia Commons