ISRO’s objective is to fly a vehicle that is more cost-effective and provides very low-cost access to space. Pushpak Viman: India's reusable spacecraft paves the way for affordable space exploration

by Air Marshal Anil Chopra (Retd)

India’s Re-usable Launch Vehicle (RLV) Pushpak Viman made another experimental flight (RLV-LEX-02) this morning from Chalakere Runway. The car-sized winged rocket sometimes dubbed the “swadeshi space shuttle” is India’s bold attempt to enter the reusable rocket segment. The current flight test is the third of its autonomous landing ability in more complicated circumstances. “The Pushpak launch vehicle is India’s bold attempt to make access to space most affordable,” said S Somanath, chairman of the Indian Space Research Organisation (ISRO).

The “Pushpak Viman” is India’s legendary spaceship named in the Ramayana, known to be the vehicle of the Lord of Wealth, God Kubera. Therefore, it is decided to name India’s most audacious 21st-century spacecraft Pushpak. The 6.5-metre aeroplane-like spacecraft weighs 1.75 tons. The most expensive part, the upper stage, houses all the important electronics and is made reusable by bringing it back safely back to Earth. For the flight test, the craft was hoisted aboard an Indian Air Force (IAF) helicopter. During the descent or glide phase, small thrusters help the vehicle navigate to the exact spot where it is supposed to land.

India thought of building its version of the space shuttle nearly 15 years ago. Ten years ago, a dedicated team of engineers and scientists plunged into making RLV a reality. The RLV flew first time from Sriharikota in 2016 and successfully landed on a virtual runway in the Bay of Bengal. The RLV then sank into the sea as per plan and was not recovered. A second test was in April 2023, at the Chitradurga Aeronautical Test Range (ATR). Called the RLV-LEX-01, the winged rocket was taken up under-slung to an altitude by an IAF Chinook helicopter and then released. It thereafter glided and landed autonomously. The test was fully successful.

ISRO’s objective is to fly a vehicle that is more cost-effective and provides very low-cost access to space. The long-term operational goals would include positioning satellites in space and supporting their repair and refuelling in orbit. It would be used to retrieve satellites from orbit for refurbishment. It would also be used to reduce space debris. It is expected that in times to come, it could be a money spinner for India when it becomes a commercially available launcher.

India’s Aeronautical Test Range

The Aeronautical Test Range (ATR), is an outdoor testing and evaluation facility set up by DRDO exclusively for unmanned and manned aircraft. The ATR is managed by DRDO’s Aeronautical Development Establishment (ADE). It is located at Varavoo Kaval in Challakere Taluk of Chitradurga district on a 4,290-acre plot. The work on the range began in 2008. The range has a Range Control Centre (RCC) with an air traffic display system. It is equipped with a mission video distribution and display system. It has a radar centre which houses primary and secondary surveillance radars. It has two hangars which house the unmanned aerial vehicles Rustom-1 and Rustom-2. The runway is currently 2.2 km long and will be expanded to 3 km soon. In addition to unmanned aerial vehicles (UAVs), the range will be used to test air-to-ground weapons, parachutes and aerostats. The facility was formally inaugurated by the then-Union defence and finance Minister Arun Jaitley on 28 May, 2017.

US Space Shuttle

The very closely watched American Space Shuttle program, a partially reusable low Earth orbital spacecraft system, was operated from 1981 to 2011 by the National Aeronautics and Space Administration (NASA). Initially thought of in 1969, it was officially called the Space Transportation System (STS). The first orbiter, Enterprise, was built in 1976 and used in approach and landing tests but had no orbital capability. The kind of stage India is currently with Pushpak Viman. It began with four orbital test flights in 1981. The first operational flight was in 1982. Five complete Space Shuttle orbiter vehicles were built and flown on a total of 135 missions from 1981 to 2011. They launched from the Kennedy Space Center (KSC) in Florida. Operational missions launched numerous satellites, interplanetary probes, and the Hubble space telescope, conducted science experiments in orbit, participated in the Shuttle-Mir program with Russia and participated in the construction and servicing of the International Space Station (ISS). The Space Shuttle fleet’s total mission time was 1,323 days.

The space shuttle comprised of an Orbiter Vehicle with three clustered main engines; a pair of recoverable solid rocket boosters; and the expendable external tank containing liquid hydrogen and liquid oxygen. It was launched vertically, like a conventional rocket. The rocket boosters were jettisoned before the vehicle reached orbit, while the main engines continued to operate, and the external tank was jettisoned after the main engine cutoff and just before orbit insertion. Thereafter, the orbiter’s two Orbital Maneuvering System (OMS) engines were used. At the end of the mission, the OMS supported deorbit and reentry into the atmosphere. During the reentry, the orbiter was protected by its thermal protection tiles. It then glided as a spaceplane to a runway landing, usually to the Shuttle landing facility at KSC, Florida, or to Rogers Dry Lake in Edwards Air Force Base, California. If the landing occurred at Edwards, the orbiter was flown back to the KSC atop the Shuttle Carrier Aircraft, a specially modified Boeing 747 designed to carry the shuttle on its back.

Four fully operational orbiters were initially built: Columbia, Challenger, Discovery, and Atlantis. Of these, two were lost in mission accidents: Challenger in 1986 and Columbia in 2003, with a total of 14 astronauts killed. A fifth operational orbiter, Endeavour, was built in 1991 to replace Challenger. The three surviving operational vehicles were retired from service following Atlantis’s final flight on 21 July, 2011. The US relied on the Russian Soyuz spacecraft to transport astronauts to the ISS thereafter.

American Crew Dragon Demo-2: First By Commercial Operator

Crew Dragon Demo-2 (SpaceX Demo-2) was the first crewed test flight of the Crew Dragon spacecraft. The spacecraft, named Endeavour, was launched on 30 May 2020 on a Falcon 9 rocket, and carried two NASA astronauts to ISS. It was the first crewed orbital spaceflight launched from the U.S. since the last Space Shuttle in 2011. It was the first ever operated by a commercial provider. Demo-2 completed the validation of crewed spaceflight operations using SpaceX hardware and received human-rating certification for the spacecraft, including astronaut testing of Crew Dragon capabilities in orbit.

Docking was autonomously controlled by the Crew Dragon, but monitored by the flight crew in case manual intervention became necessary. The spacecraft soft-docked with the ISS on 31 May 2020. Endeavour autonomously undocked from the station on 1 August 2020 and returned the astronauts to Earth in the first water landing by astronauts since 1975.

SpaceX Reusable Rockets

Elon Musk’s SpaceX has privately funded the development of orbital launch systems that can be reused many times. Technologies were developed over the last decade to facilitate the full and rapid reuse of space launch vehicles. The project’s long-term objectives include returning a launch vehicle’s first stage to the launch site within minutes and returning a second stage to the launch pad following orbital realignment with the launch site and atmospheric reentry in up to 24 hours.

The program was announced in 2011. SpaceX first achieved a successful landing and recovery of the first stage in December 2015. The first re-flight of a landed first stage occurred in March 2017 with the second occurring in June 2017 that one only five months after the maiden flight of the booster. The third attempt occurred in October 2017. Re-flights of refurbished first stages then became routine. In May 2021, they had the first booster to launch ten missions.

The reusable launch system technology was initially developed for the first stage of Falcon 9. After stage separation, the booster flips around and reenters the thicker part of the atmosphere. For landing, the rocket burns for final low-altitude deceleration and touchdown.

Developing reusable second stages is a more challenging engineering problem because the vehicle is travelling at orbital velocity. But, second stage reuse is considered vital to Elon Musk’s plans for settlements on Mars. As of 2023, SpaceX is developing the Starship system to be a fully reusable two-stage launch vehicle, intended to replace all of its other launch vehicles and spacecraft for satellite delivery and human transport - Falcon 9, Falcon Heavy and Dragon, and eventually support flights to the Moon and Mars. To date, they have had 251 re-flights.

Russian Reusable Rocket Programs

Russia also had the space shuttle-type program “Buran”. Buran completed one uncrewed spaceflight in 1988 and was destroyed in 2002 due to the collapse of its storage hangar. The Buran-class orbiters used the expendable Energia rocket, a class of super heavy-lift launch vehicles. The project was abandoned.

The Soyuz-7 “Amur” is a partially-reusable, methane–fueled, orbital launch vehicle currently in the design concept stage in Russia. It will comprise reusable parts (10.5 tonnes) and expendable (13.6 tonnes). The Amur looks a lot like a SpaceX Falcon 9. The preliminary design process began in October 2020, with operational flights planned for no earlier than 2028. This family of new Russian rockets is meant to replace the legacy Soyuz. The new rocket, designated Soyuz-7 in 2013, was to be designed from the ground up. It is planned to have thrust vector control. It will be a scalable family with three versions covering the medium to heavy payload ranges. The first flight was earlier planned in 2022. Meanwhile, Russia’s Krylo-SV reusable rocket conducted drop test in August 2023. It is at a similar stage as the Indian project.

Chinese Reusable Rocket Programs

China has an advanced and aggressive space program. They are intensifying the pursuit of reusable rockets. They successfully carried out a test of the Kuaizhou reusable prototype rocket in January 2024. The rocket lifted off from the pad, and hovered in the air for nine seconds before landing back at the takeoff area. The flight lasted 22 seconds. The test was conducted by Expace, a company that operates under China Aerospace Science and Industry Corporation (CASIC), the giant Chinese state-owned defence and space contractor. Their sister organization, China Aerospace Science and Technology Corporation CASC, makes China’s Long March rockets. CASC plans to launch two large reusable rockets in 2025 (diameter 4m) and 2026 (5m). SpaceX’s Falcon Heavy diameter is 3.66m. Of course, SpaceX’s Starship (9m) will dwarf the planned Chinese rockets. The new launch vehicles are part of China’s plan to put a Chinese astronaut on the Moon by the year 2030.

China opened the space sector to private capital in 2014, leading to the emergence of a flurry of start-up's. A number of these are now launching, or are close to launching, liquid propellant rockets with potential reusability. Expace is known for its expendable Kuaizhou solid rockets, which have conducted two orbital launches this year already. The success of the latest test laid a solid foundation for the development of the Kuaizhou series of reusable liquid oxygen methane launch vehicles.

Beijing-based iSpace performed a pair of longer duration, higher altitude tests last year, with its vehicle translating to a separate landing target during the trial. Fellow startup Landspace then conducted its own hop test with a stainless steel methane prototype rocket at Jiuquan in January this year. Landspace aims to launch the full Zhuque-3 rocket whose first stage will be reusable, like that of SpaceX’s Falcon 9 in 2025. Another state-owned spinoff, CAS Space, is aiming to launch its reusable Kinetica-2 rocket in 2025 and has used a jet-powered prototype to test the guidance, navigation and control systems needed for rocket landings.

Commercial firm Galactic Energy performed a similar test last summer. The company aims to perform the first launch of the Pallas-1 expendable kerosene-liquid oxygen rocket late this year. The fact that China’s public sector has thrown in its weight behind the effort could mean that China will have multiple reusable launch vehicle options in the coming years.

Way Ahead India

India is already a significant space power. It is one of the only six countries in the world that possess full launch capabilities, deploy cryogenic engines, launch extra-terrestrial missions and operate large fleets of homegrown artificial satellites. It is the only country to have landed a spacecraft on Moon’s South Pole.

Big action is unfolding in reusable rockets and spaceplanes. The USA and China are moving very fast, with high funding. Pushpak Viman is an important stage for India’s reusable space transport system. India’s space program is being driven at the highest level by the Prime Minister’s Office itself. India has the lowest cost of payload for its space missions. It gives it a huge global market, especially the Global South looks up to it. We need to maintain focus and push ahead.

The writer is Director General, Centre for Air Power Studies