ISRO's PSLV-C60/SPADEX (Space Docking Experiment) mission which will launch on 30th December 2024, is all about high-profile experiments that are aimed at enabling India's human spaceflight ambitions and exploration missions like Chandrayaan-4. While the SPADEX satellite docking is a preliminary step towards space station assembly technology, ISRO is also testing several other equipment that can be used in the proposed 'Bharatiya Antariksh Station', which ISRO hopes to get fully operational by 2035.

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By 2028, ISRO plans to launch the first module of the space station and gradually expand it by docking more modules. It is envisioned as a robotic space station at first, which will later be capable of hosting astronauts.

Also read: Explained: ISRO can now restart its 'CE20' Cryogenic engine in space

Here are the exciting experiments that ISRO Centres are launching aboard the POEM or PSLV Orbital Experimental Module(POEM): 

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Walking Robotic Arm

ISRO's Thiruvananthapuram-based ISRO Inertial Systems Unit (IISU) has already developed Vyommitra, a humanoid robot that will fly on the Gaganyaan uncrewed test flights. However, the walking robotic arm is an attempt at creating a walking robotic arm that moves around like a worm.

"In the microgravity environment of space, every free object floats. Therefore, we wanted to build and demonstrate a robotic arm that can walk around in space. We have placed a few grappling points on the experimental platform and the robotic arm will be connected to one such point. On command, the robotic arm can move like a worm - if the tail is now attached to one grappling point, its head can move to the next grappling point and attach itself over there. Once the head is attached to a grappling point, the tail can detach and move freely. Therefore, with multiple grappling points placed throughout the proposed Indian space station, we can try and use a 'walking robotic arm' to move around and carry out various functions, including the operation of systems, performing repairs, etc.," Padmakumar, the Director of ISRO's IISU told WION. 

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He added that this 1-metre-long robotic arm is specifically developed for the space environment and cannot be used on Earth. According to him, this walking robotic arm could serve various purposes in the future, such as performing repairs inside and outside the space station.

Also read: ISRO simulates space conditions for astronauts in 'Habitat-1'. Here's what it is

"Usually, astronauts have to venture out of the space station into the harsh and risky space environment to perform some repairs. However, we foresee that such walking robotic arms can someday perform some part of this role. This seems practical given the rate at which robotics and AI technology is progressing," he explained. 

Debris Capture Robotic Manipulator

Developed by ISRO's Vikram Sarabhai Space Centre, which focuses on developing space transportation systems, the objective of this experiment is to demonstrate the capturing of tethered (tied, but free-floating) debris using a robotic arm. Once in space, the robotic arm will perform 'visual servoing' (a control technique that uses visual feedback from a camera to guide the movement of a robot) and capture the tethered object that is freely floating in space. 

"There are various applications of being able to capture an object in space using a robotic arm. It can be deployed to capture pieces of free-floating space debris; it can be used to capture a satellite, repair it, carry out refuelling of a satellite," Dr. Unnikrishnan Nair, Director of ISRO's VSSC told WION. According to ISRO, this robotic arm will be capable of capturing free-floating debris and refuelling tethered and free-floating spacecraft in future POEM missions.

Lead Exempt Experimental System (LEXS)

Lead has been traditionally used in soldering (joining pieces of metal or wire together using a mixture of metals that is heated and melted). The primary reasons for using lead in soldering include its desirable properties such as low melting point, reliability, and ease of use, which make it suitable for a variety of applications across electronics, aerospace, electrical wiring, etc. 

However, despite its effectiveness, the use of lead in soldering has been increasingly restricted due to the health hazards associated with lead exposure and the environmental concerns.

The Restriction of Hazardous Substances (RoHS) directive, which was adopted by the European Union in 2003, restricts the use of lead and other hazardous substances in electronic products.

ISRO's VSSC has developed a DC-DC Converter using lead-free (RoHS-compliant) components and processes. The objective is to demonstrate and assess the reliability and functionality of a RoHS-compliant system in a microgravity environment.

"Our goal is to test this new system in the harsh conditions of space. Once it is proven to work in space, it can be adopted in our processes on earth as well, thereby improving our compliance with electronics industry-approved practices," Dr Unnikrishnan Nair, Director, VSSC, explained to WION. 

Compact Research Module for Orbital Plant Studies (CROPS)

The CROPS payload, developed by VSSC, is envisioned as a multi-phase platform to develop and evolve ISRO’s capabilities for growing and sustaining flora in extraterrestrial environments.

Designed as a fully automated system, a week-long experiment is planned to demonstrate seed germination and plant sustenance until the two-leaf stage in a microgravity environment. The experiment plans to grow eight cowpea seeds in a closed-box environment with active thermal control.

Passive measurements, including camera imaging, O2 and CO2 concentrations, relative humidity (RH), temperature, and soil moisture monitoring, are available for monitoring plant growth. 

"Plant growth in the microgravity environment of space is drastically different from that of Earth. On Earth, we have gravity, whereas in space, the plant's shoot need not be against gravity. This is our attempt at space farming. This will be of great use when we have our own functional space station with astronauts on board," Dr. Unnikrishnan Nair, Director of ISRO's VSSC, explained to WION.

Reaction Wheel Assembly (RWA)

A reaction wheel is a crucial component used in the attitude control system (ACS) of satellites. It helps control and stabilize the orientation (attitude) of the spacecraft in space without relying on thrusters or external forces.

As per the mission requirement, the satellite is required to orient towards a particular direction, and reaction wheels help accomplish that. This payload developed by IISU, is meant to study the attitude stabilisation of the POEM platform. 

"All our satellites are controlled by reaction wheels. When the wheels rotate in one direction, the satellite moves in the opposite direction. This time we have made these reaction wheels using commercially available electronics, which helps bring down the overall cost of the device and makes it affordable for academia and startups," Padmakumar, Director, IISU, explained to WION.