UPSC Prelims 2025 Q83: Axiom-4, SpaDeX, Gaganyaan — Explained
Consider the following space missions:
I. Axiom-4
II. SpaDeX
III. Gaganyaan
How many of the space missions given above encourage and support microgravity research?
- Only one
- Only two
- All the three
- None
Answer: (b) Only two
Statement-wise explanation
- I: correct — Axiom-4 (Ax-4) was a private crewed flight to the International Space Station run by Axiom Space on a SpaceX Crew Dragon. ISRO's Gaganyatri, Group Captain Shubhanshu Shukla, was the mission pilot. Before launch, ISRO had shortlisted seven microgravity experiments from Indian research labs and academic institutions to be done on the ISS. After the flight, ISRO reported all seven complete: tardigrades, myogenesis (muscle loss), sprouting of methi and moong seeds, cyanobacteria, microalgae, crop seeds, and a cognitive study using Voyager displays. Microgravity research was a core purpose of the mission.
- II: incorrect — SpaDeX (Space Docking Experiment) is a technology demonstration mission. ISRO gives its primary objective as rendezvous, docking and undocking of two small spacecraft of about 220 kg each, SDX01 (chaser) and SDX02 (target), in a roughly 470 km circular orbit. Its secondary objectives are power transfer between the docked spacecraft, control of the combined spacecraft, and payload operations after undocking. It launched on PSLV-C60 on 30 December 2024 and docked on 16 January 2025, making India the fourth country to dock in orbit. Microgravity research is not among its stated objectives.
- III: correct — Gaganyaan is India's human spaceflight programme. Its aim is to send a crew of three to a 400 km orbit for a 3-day mission and bring them back safely. The programme lists enabling microgravity research in fields such as biology, medicine and materials science among its goals. In September 2024 the Cabinet widened its scope to include the first module of the Bharatiya Antariksh Station (BAS-1) by 2028. The station is intended as a platform for microgravity research.
How to eliminate
This question is mostly settled by knowing why each mission exists. Ask what each one was built to do. Axiom-4 and Gaganyaan both put humans in orbit, and human spaceflight programmes are built around life-science and microgravity experiments. Axiom-4's seven Indian ISS experiments were widely reported before the exam. SpaDeX is in the name: Space Docking Experiment. It is a technology demonstrator for rendezvous and docking, which India needs for Chandrayaan-4 sample return and the Bharatiya Antariksh Station. If you know SpaDeX's stated purpose, the count is two. Watch the trap: the PSLV-C60 launch that carried SpaDeX also flew the POEM-4 platform, which did grow cowpea seeds in microgravity. That experiment belonged to the rocket's reused upper stage, not to the SpaDeX spacecraft. Fact to remember: SpaDeX = docking, undocking and power transfer between two satellites.
Know more
Microgravity is not the absence of gravity. At the ISS altitude of about 400 km, gravity is still roughly 90% of its strength at the surface. Astronauts float because the station and everything in it are in continuous free fall around Earth. Effective gravity drops to about a millionth of Earth's ('micro-g'). With gravity largely removed, scientists can study:
- Biology and medicine: muscle and bone loss, how microbes and algae grow, plant germination
- Materials science: crystal growth, alloys, fluid behaviour without convection
- Human factors: how astronauts think and perform in orbit
| Mission | Type | Agency | Core objective | Microgravity research? |
|---|---|---|---|---|
| Axiom-4 (2025) | Crewed, private flight to ISS | Axiom Space, with NASA, SpaceX, ISRO, ESA | First Indian to visit the ISS; about 18 days of science | Yes: 7 Indian experiments |
| SpaDeX (PSLV-C60, Dec 2024) | Uncrewed, two 220 kg satellites | ISRO | Rendezvous, docking, undocking, power transfer | Not an objective |
| Gaganyaan | Crewed, indigenous | ISRO | 3 crew to 400 km for 3 days; leads to BAS | Yes: stated aim |
How they fit together. Axiom-4 gave an ISRO astronaut hands-on ISS experience, and ISRO says what it learned will feed into the Indian human spaceflight programme. SpaDeX proves the docking technology needed to assemble the Bharatiya Antariksh Station in orbit; the first module, BAS-1, is targeted for 2028, and the full station for 2035. Gaganyaan is the crewed backbone that links them. After its scope was revised in September 2024, its total funding is ₹20,193 crore.
POEM (PSLV Orbital Experimental Module) reuses the PSLV's spent fourth stage as an orbital platform. POEM-4 carried 24 payloads: 14 from ISRO and 10 from startups and academia. They included VSSC's CROPS seed-germination box and a walking robotic arm.
In the news
All three missions were in the news in the months before Prelims 2025. SpaDeX launched on 30 December 2024 and docked on 16 January 2025. Ahead of its launch, ISRO announced in spring 2025 the seven Indian microgravity experiments for Shubhanshu Shukla's Axiom-4 flight. Gaganyaan's uncrewed test flights and the Bharatiya Antariksh Station plan were also being reported.