Chandrayaan-3 landed successfully. After 60 years of ups and downs, what is the level of India's space program?

India's Chandrayaan-3 successfully landed on the moon, which also caused a lot of debate on the Internet. Many people want to know how good is India's space technology? What are the gaps between it and ours?

In fact, as the saying goes, laymen see the excitement while experts see the details. It is not comprehensive enough to discuss a country's aerospace technology based on the success or failure of a project. So today we will take a look at the development history of India's launch vehicles and have a glimpse of India's aerospace technology.

India's Chandrayaan-3, Image source: Internet

India's space industry has a high starting point but slow progress

India gained independence in 1947. Since it was not a major battlefield in World War II, the independence process did not involve fierce fighting. The remaining industrial and educational bases from Britain's many years of operation in India were still there. So compared to when the People's Republic of China was just founded, India's starting point was more or less higher than ours.

Not only is their starting point higher, but their international environment is also stronger than ours. Unlike us, there is no superpower like the United States that wants to strangle it in the cradle. It seems that such a starting point and environment should be more conducive to the development of aerospace technology, but in fact, it is just the opposite. It is precisely because of the relaxed international environment that they do not need to have nuclear technology and ballistic missile technology as soon as possible. The aerospace of various countries all started with ballistic missiles, which are essentially the same thing.

Until the 1960s, India had not seriously engaged in aerospace, and did not even have a national department dedicated to aerospace. In 1962, when we won the self-defense counterattack war on the Sino-Indian border, India began to catch up with us.

The satellite was launched into space using someone else's rocket

At this time, our DF-1 ballistic missile had been successfully tested and the DF-2 was under development, but India had nothing. Our DF-1 was copied from the P2 missile provided by the Soviet Union, which was equivalent to the Soviet Union providing the technology.

Could India do this? No, because they were promoting the Non-Aligned Movement at the time, which meant that no matter whether it was the United States or the Soviet Union, they would neither ally with you nor be hostile to you. They were playing the game of being close yet distant, and naturally it was impossible for them to obtain such important technology as ballistic missiles.

Without allies, there would be no hostile camp, so they could buy sounding rockets from various countries for research. They were the kind of little things that were as thick as a bowl and several meters long. They came from the United States, the Soviet Union, and France.

India's early sounding rockets could only be carried by bicycles.

In 1967, India finally successfully launched their first sounding rocket "Russini", which was 150 centimeters long and could fly up to 10,000 meters high. Today it is only a hail-proof rocket.

Three years later, China's Long March 1 rocket carried the Dongfanghong 1 satellite into Earth orbit. This time India was completely unable to sit still. What should it do?

At that time, Sino-Soviet relations had broken down, and the Soviet Union had been actively trying to win over India. So India signed an agreement with the Soviet Union, exchanging the right to use some important ports in India for cooperation in aerospace technology. It was too late for the Soviet Union to teach India how to build rockets, so India first built an artificial satellite and let the Soviet Union use their rockets to launch it.

Several early Indian rockets had poor performance

The Rockets' bumpy road to development

Later, after a failed launch, India's independently developed SLV-3 rocket sent their Russini-1 satellite into space in 1980. It seemed that the Indians had finally mastered space technology.

SLV-3 rocket. Image source: provided by the author

But if we look at the SLV-3, we will find that it is actually a bit strange. It uses a four-stage pure solid rocket. Solid rockets are simpler than liquid rockets, but their efficiency is also relatively low. Therefore, in order to be able to enter orbit, India had to divide it into four stages to send the 35-kilogram Lusini-1 into space. Moreover, the orbital altitude was relatively low, and it fell into the atmosphere after 20 months of operation.

Our Dongfanghong-1 weighs 173 kilograms and has a higher orbit altitude. It was launched in 1970 and is still in operation.

SLV-3 rocket. Image source: provided by the author

India also knows that the SLV rocket is too weak and can only solve the problem of whether it has one or not, but it is absolutely not practical. It can't do anything with a carrying capacity of less than 40 kilograms. So they made the ASLV based on the SLV, which is actually based on the original one with a booster added to the first stage, and all of them are solid rocket engines.

ASLV did improve its carrying capacity, but by how much? 150 kg in low Earth orbit, still not as good as our Long March 1. When ASLV was first launched, it was already 1987, a year before I was born. But it was not until I was in preschool, in 1994, that it achieved complete success in its fourth test launch.

ASLV rocket, Image source: provided by the author

Once it succeeds, will it be widely used?

Wrong, India immediately and resolutely abandoned this rocket, because the biggest drawback of solid rockets is their low efficiency, so it is difficult to use them to build a rocket with a large carrying capacity.

Although India's rockets are not very good, it is very good at building satellites. Various communication satellites and scientific satellites are launched one after another. However, these satellites are either too large or need to be sent to polar orbit, which ASLV cannot do. Therefore, India suffered the pain of having satellites but no rockets during that period.

Finally, there is a useful one!

So the Indians learned from their mistakes and started to work hard with liquid rocket engines. With the help of some of the Soviet Union's experience, they finally built the PSLV, which has four core stages, the first and third stages are solid, the second and fourth stages are liquid, and it is also equipped with six solid rocket boosters. It has a low-Earth orbit carrying capacity of 3.8 tons and can send a 1.2-ton payload to geosynchronous orbit.

Although the design is still unconventional and different from those of the United States and the Soviet Union, the results are very good. It has been in use since the early 1990s and is very reliable. It has not only undertaken many commercial satellite launch missions, but the last time it launched 104 satellites in one rocket was also done by its later improved version.

PSLV rocket. Image source: provided by the author

The significance of PSLV is not only that India finally has a rocket that can be used, but more importantly, it has enabled India to develop a liquid rocket engine, Vikas, which was developed by India based on the French Viking-2 engine, which is also the engine of the Ariane rocket.

Its status in India is somewhat similar to that of the YF-20 in China. It uses conventional propellants, that is, hydrazine fuel, and has a similar thrust level of 70 to 80 tons. On PSLV, it was only used as a second stage, not as the main player. When India found it to be reliable and they needed a rocket with a stronger carrying capacity, Vikas took up the banner of Indian spaceflight.

They developed the GSLV series of rockets, with a total of three models: MK1, MK2 and MK3. The other configurations of the first and second generation GSLV are basically the same, with the first stage still using a solid rocket engine, four boosters powered by the Indian Vikas, and the second stage still using the Vikas engine.

Image source: provided by the author

It is worth mentioning that with this series of rockets, India has finally started to use advanced engines - hydrogen-oxygen engines.

Although it is difficult to increase the thrust of hydrogen-oxygen engines, they are very efficient and are particularly suitable for use in the upper stages of rockets. At this time, because the remaining weight is already very light, it does not need as much thrust as it does during takeoff, but its main feature is to save fuel and last longer. The hydrogen-oxygen engine used in the first generation of GSLV was the RD-56M purchased from the Soviet Union. This engine was originally designed by the Soviet Union for manned lunar landings, but the project later failed, so they were modified and sold to make extra money.

Later, India also developed its own hydrogen-oxygen engine, so when it came to the second generation of GSLV, the upper stage was replaced with an Indian-made one. The third generation of GSLV looks completely different from the previous two generations. The core stage was replaced with the Vikas engine mentioned earlier, finally making it the protagonist, while the boosters on both sides are still solid rocket engines, and the third stage is amazing. They used a 20-ton thrust CE-20 hydrogen-oxygen engine, which is an open-cycle hydrogen-oxygen engine. Among the upper stage hydrogen-oxygen engines in the world, the thrust is one of the best. You know, the YF-75D used on our Long March 5 has a thrust of only 9 tons.

Genealogy of India's launch vehicles. Image source: provided by the author

The GSLV-3 was the one that recently sent the lunar spacecraft to the moon. Its low-Earth orbit carrying capacity is about 10 tons, and its geosynchronous orbit carrying capacity is about 4 tons, which is basically the same as our mature Long March 2 and 3 series.

It can be said that, by now, the basic carrying capacity of India's launch vehicles has basically reached the level of ours in the 1990s. That is to say, whatever we could launch in the 1990s, they can now basically launch. In fact, we can see that, at least in the aspect of launch vehicles, the gap between India and us has not been significantly narrowed or expanded. Basically, we are catching up, and even some technologies of India are not inferior to ours.

For example, the technology of high-thrust solid rocket engines, because they have been using it, while we basically use liquid propulsion in aerospace, so it may be more mature than ours.

For example, as for the 20-ton hydrogen-oxygen upper stage mentioned earlier, we have already tested the 25-ton one, and it uses a closed expansion cycle, which is more advanced than India's. But at least they have actually used it to fly to the moon, while we have not actually flown it yet.

India's hydrogen-oxygen engine third stage, Image source: provided by the author

Therefore, on the road to the pinnacle of science and technology, researchers from all over the world are catching up with each other. If they don't make progress, they will fall behind. This is a battlefield without gun smoke. Whether it is abroad or in China, most professionals are working hard. What we need to do is to pay attention, understand and look at it correctly. This is the greatest support for our aerospace industry.

Planning and production

This article is a work supported by Science Popularization China Starry Sky Project

Produced by | Science Popularization Department of China Association for Science and Technology

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.

Author: Liang Yichen (Teacher Gou Sheng) Lecturer at Xi'an Aviation University

Review丨Liu Yong, Researcher, National Space Science Center, Chinese Academy of Sciences

Editors: Lin Lin, Ding Zong

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