India is set to launch its first manned mission to space. The Indian Space Research Organisation (ISRO) has already set the process in motion. Gaganyaan will become a reality in 2022, in line with PM Modi’s plans. But ISRO needs to be ready on vital aspects before the Gaganyaan can take off

by TV Venkateswaran

The Human-Rated Launch Vehicle

Powered by the indigenous cryogenic engine, the GSLV MK-III, with a capacity to take a 4-ton payload to geosynchronous transfer orbit and 10-ton payload to low earth orbit, is amply suited for the Gaganyaan mission, with an estimated payload of 5–6 tons. However, the critical challenge is to make the craft carry humans.

There is no single protocol for human-rated certification but there are several safety features and built-in redundancies that make the craft safe for carrying humans to space. Redundancies are built into a space programme to meet unexpected challenges and human rated missions require a very high degree of redundancy.

ISRO has set the reliability target of 0.99 for the launch vehicle, which means only one out of a hundred launches can fail.

The space body is building three sets of GLSV MK-III variant rockets along with crew and service module. It will undertake two unmanned dry runs during December 2020 and June-July 2021, before the final launch with 2–3 Indian astronauts, sometime in December 2021 or early 2022. Other space agencies have often used chimps and dogs during the dry run. However, ISRO is proposing to use a humanoid robot resembling a human during the experimental launch.

Dry run will not be that dry: ISRO proposes to use the humanoid robot during the two test missions to carry out useful research. Forty projects on microgravity have already been shortlisted.

Emergency Escape System

The human variant of GSLV MK-III has an extra small rocket on top of its nose cone, called escape tower. The orbital module is attached to this emergency escape system. When something goes wrong with the rocket, seven specifically designed quick-acting solid fuel motors in the escape tower fire up and pull the module with humans away from the main rocket. Once it reaches a safe distance, parachutes are deployed, and the crew module is landed safely.

A crucial crew escape assembly test was conducted by ISRO on July 5, 2018. Called Pad abort test, the mock crew module with a mass of 12.6 ton was attached to the escape tower and tested.

The Crew Escape System along with the mock crew module soared skyward for about 2.75 km before unfurling its parachutes and floating back to the Earth’s surface safely. More tests will be undertaken before the humans are flown to space.

Orbital Crew Module

ISRO has years of experience building satellites and electronics that work in the harsh space environment. The challenge of an orbital module is a degree arduous. Electronics in the satellite are made to work in a vacuum in the space.

The spacecraft carrying humans have to be hermetically sealed and fitted with necessary operational and emergency systems. The orbital module will have a crew module with a cabin having desired air pressure, humidity and temperature. The crew module will be mated with a service module powered by two liquid-propellant engines. Both put together will have a combined weight of about 3 tons.

Hindustan Aeronautical Limited (HAL) has been roped to design and develop the crew module structural assembly. While the structural assembly has been completed, the internal furnishing is on its way.

Human Life Support Systems

The crew module that is designed to host three Indian astronauts is cramped. The cylindrical module has a diameter of just 3.5 metres and a length of 3.58 meters, little bigger than a minibus. Unlike the International space station, the module will not have a shower, bunker beds and workbenches. Nevertheless, as Indian astronauts will spend considerable time, about a week, near Earth-like conditions have to be maintained. In addition to removing carbon dioxide exhaled by the crew and recovering oxygen from it, harmful gases and smells must be removed. Sensors to detect and equipment to suppress fire and other emergencies must be equipped. Facilities for heating and preparing food, safe and sanitised disposal of human excreta also need to be provided.

ISRO is developing an Environmental Control & Life Support System (ECLSS) to make the crew module sustain human life in the harsh space environment. Various sub-systems of ECLSS including Thermal and Humidity Control System (THCS), CO2 and Odour Removal System (CORS) and Cabin Pressure Control System (CPCS) have been integrated into Cabin Environment Simulation Chamber, simulating the crew cabin volume, and integrated tests are in progress.

The ground testing and individual testing of gadgets from air scrubbers to the oven for heating the food is underway. Trials under simulated near-zero gravity and vacuum conditions will be done before testing them in pilot launches slated during the end of the year.

Mysore based Defence Food Research Laboratory (DFRL) has developed the ready to cook Indian cuisine for the Indian astronauts. The dry food has to be reconstituted by adding water to the desiccated pack. In microgravity, the crumbs can float anywhere and hence they have to be prepared in a unique way to avoid crumple. Drinks will be in Tetrapaks with specialised straws that will not spill drops.

Spacesuits

During ascent, descent and emergency situations, the crew have to don a spacesuit as a matter of precaution. Combining the best features of the American and Russian spacesuits, an Indian firm based at Vadodara, with the collaboration of ISRO’s Space Applications Centre (SAC), Ahmedabad, has indigenously developed astronaut crew escape suits.

Four layered and weighing just five kg the spacesuit can hold one bottle of oxygen which can allow the astronaut to breathe in space for about 60 minutes. The suit has features like a flexible hood zipper, touch screen sensitive gloves, utility pockets, air diverters and lightweight shoes. The suit could keep the astronaut comfortable even when the ambient temperature is as low as minus 40°C or as high as 80°C.

Re-Entry Module

Although ISRO has launched hundreds of satellites into space and a few to the moon and Mars, they are meant to remain in space and not designed to return to Earth. However, a human mission must return the crew safely back to Earth. Several precisely executed manoeuvres have to be made for the craft to re-enter and touch down without harm.

First, when the time comes for landing, the craft must de-orbit from 400 km to about 120 km altitude using the propulsion system in the service module. The craft should de-boost. Once the orbiter module drops down to a determined height, the solar panels and service module are to be jettisoned. The crew module must orient at an exact angle and speed. If not, the life of the crew will be in danger. Operations like aero-braking, deployment of parachutes must take place sequentially at the appointed time.

Some components of the re-entry procedures such as capsule separation, heat shields and aero-braking systems, deployment of the parachute, retro-firing, splashdown, flotation were tested during the Atmospheric Re-entry Experiment (CARE) experiment launch carried out during 2018. During the experiment, the dummy crew module was at a height of 126 km and hurled into space.

As the coasting craft came down to an altitude of 80 km, the engines were shut down. The aero-braking was set in motion. As the crew module reached a height of 15 km, the 2.3-meter diameter pilot parachutes, followed by the 6.2-meter drogue parachutes, were deployed. This reduced the speed to 50 meters per second.

When the module reached a height of about 5 km, a pair of main parachutes, 31 meters in diameter, largest ever made in India, was deployed. The performance of capsule separation, heat shields and aero-braking systems, deployment of parachutes, the firing of retro-rockets, inflation of the flotation on the impact of water and procedures to recover the crew capsule from the Bay of Bengal were satisfactory. Testing of completely integrated re-entry system awaits the dry runs.

Heatshield

Shooting stars are small space rocks that fall on Earth. While traversing the atmosphere, due to friction, they heat up and burst into flame.

In a similar manner, the crew capsule will turn into a ball of flame while re-entering Earth’s atmosphere during the landing manoeuvre. The temperature will soar to thousands of degrees. To prevent burning of the craft with the crew, thermal shield tiles made with unique materials are affixed on the exterior of the capsule.

The forward portion is covered with carbon phenolic tiles while the side panels are encased in head resistant tiles. The performance of the heat shield was tested during the CARE experiment.

Splashdown & Recovery Logistics

After the re-entry, the crew module will be falling towards the Earth like a stone. The module will break into million pieces, and Indian astronauts inside face death if the speed of the fall is not retarded.

Thanks to Aerial Delivery Research and Development Establishment, one of the research and development labs under the Defence Research and Development Organisation (DRDO), a robust, sturdy parachute has been developed. This, when deployed, reduces the vertical speed of the crew module from a breakneck pace of 216 meters per second to safe levels of 11 meters per second on touchdown.

The ISRO crew module, upon re-entry, is designed to splashdown in a predetermined spot in the sea. Once the crew module touches the water, the parachutes must disengage and separate. Flotation must inflate and keep the module from sinking under the sea.

The module must then broadcast a tracking signal beacon for the rescue and recovery ship to swiftly approach and take away the crew. The recovery logistics were also tested during the CARE experiments in 2014 when, after the crew module splashdown near Port Blair in Andaman, the Indian Coast Guard ships zoned in to trace the signal and recovered the module.

The author is a science communicator with Vigyan Prasar, New Delhi