‘Pushpak’ aircraft: Decoding India’s ambitious reusable launch vehicle

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The Indian Space Research Organization successfully conducted the second landing experiment with its ambitious reusable launch vehicle, Pushpak, on March 22, 2024.

Pushpaka, adapted from the epic Ramayana, is intended not only to launch missions into space, but also to return missions, similar to the American shuttle missions.

The idea is simple — democratize access to space and make it cheaper. To ensure this, the Indian Space Agency is focusing on developing indigenous technology in the form of RLVs.

The Pushpak mission is part of ISRO’s broader strategy to develop a fully reusable launch vehicle, which can reduce the current cost of spaceflight by a whopping 80%.

Currently, it can cost between $12,000 to $15,000 to launch a kilogram of payload into space. The aim is to reduce this to $500 – $1,000 per kilogram, with a two-fold approach: making the system recoverable and reusable, and adopting more efficient propulsion systems such as air-breathing rockets.

Developing India’s ‘Pushpak’ aircraft

The RLV program focuses on three main areas: powerful engines, sustained re-entry and safe landing.

Solve the engine puzzle

The first is the scramjet engine, which, unlike conventional engines, uses the high speed of the vehicle to compress the incoming air, eliminating the need to carry heavy oxidizers. This will not only reduce the liftoff mass of the vehicle, but also the cost.

The first experimental mission of ISRO’s scramjet engine to validate the air breathing propulsion system was successfully carried out on August 28, 2016 from Satish Dhawan Space Center SHAR, Sriharikota. After about 300 seconds of flight, the vehicle touched down in the Bay of Bengal, about 320 km from Sriharikota. It uses hydrogen as fuel and oxygen from atmospheric air as oxidizer.

Re-entering in one piece

One of the biggest challenges in space exploration missions is re-entering Earth’s thick atmosphere. Re-entry heat management continues to be a headache for space agencies around the world.

It is important to protect the inflorescence during its return from fire to the Earth’s atmosphere. ISRO is testing heat-resistant materials and re-entry profiles to ensure the vehicle survives the intense heat generated by hypersonic travel. In May 2016, a test flight reached an altitude of 65 km and re-entered the atmosphere at hypersonic speed, validating the RLV’s design.

Nailing the touchdown

Because the vehicle will be driven autonomously, safely downshifting to all three gears is paramount. The vehicle will act like a glider as it approaches the runway and the system must be precise and on point to make a pitch-perfect landing.

On March 22, 2024, the RLV Landing Experiment (LEX) demonstrated the third critical aspect of this vision: autonomous landing.

PM Modi was briefed about Pushpak during his visit to VSSC. (Photo: ISRO)

The experiment was designed to test the vehicle’s ability to handle non-trivial conditions—that is, conditions that deviate from the expected path. Pushpak was released with anomalies induced to assess the strength of its navigation, control and guidance mechanisms. Pushpak successfully demonstrated its ability to right and land autonomously.

These technologies include sophisticated navigation systems, a pseudolight system acting as a ground-based GPS alternative, a Ka-band radar altimeter for precise altitude measurement, an indigenous NavIC receiver and an innovative landing gear system.

In addition, the mission used aerofoil honeycomb fins and a brake parachute system for controlled descent and landing.

RLV

The Pushpak mission represents a leap towards making space exploration more sustainable and cost-effective. By demonstrating the reusability of flight hardware and systems, ISRO has demonstrated that it is possible to carry out space missions at a fraction of the cost.

Looking ahead, the RLV-TD program is set to undergo more experimental flights, including the Orbital Return Flight Experiment (OREX), and the Scramjet Propulsion Experiment (SPEX). These experiments will pave the way for the development of a two-stage orbital launch vehicle, which aims to more efficiently deliver payloads to their intended orbits.

The current winged RLV, with a wingspan of 3.6 m and an overall length of 6.5 m, is planned to be increased 1.6 times for the first stage of this reusable orbital launch vehicle.

The RLV’s design, which features a low lift-to-drag ratio, is optimized for high-speed, high-angle approach and landing at speeds up to 350 kmph. While a high lift-to-drag ratio is generally preferred for fuel efficiency in airplanes, a lower ratio is advantageous during landing, allowing for a controlled descent and safe touchdown.

Pushpak is gradually moving towards becoming a reality as India opens up to the world.

(This is an article written by Manish Purohit. Manish is a solar power and spacecraft solar panel expert with extensive experience in managing critical space missions including Chandrayaan-2 and Mangalyaan)

Published by:

Sibu Kumar Tripathi

Published on:

March 30, 2024

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