- Sep 21, 2022
Also from abstract of paper submitted at International Astronautical Federation.Overview of Twelfth Five Year Plan 2012-2017
. . .
4.13 In order to demonstrate emerging new technology developments, a series of experimental satellites have been planned. One of the major missions being the technology demonstration related to Docking and Rendezvous. These satellites will be flown on the PSLV missions as auxiliary or co- passenger satellites
SourceISRO is planning an on-orbit Rendezvous Docking experiment in the near future, to develop and demonstrate the technology needed for rendezvous docking. In this experiment, two IMS(Indian Micro Satellite) Spacecrafts, one designated as target and the other designated as chaser, are launched by a PSLV launcher into two slightly different orbits. No communication link between the target and chaser during the far range rendezvous phase in which relative separation is around 50km to 5km range is envisaged and this phase is a ground guided phase. In the docking phase of the mission, docking sensors such as Laser Range Finder during the relative separation of 5 km to 0.25km, Docking Camera during the relative separation of 300m to 1m ,Visual Camera for real time imaging during the relative separation of 1m to docking are used respectively.
India’s space agency, ISRO, plans space docking experiment (SPADEX) next year, the agency’s Chairman, Kailasavadivoo Sivan, told Business Line today. Docking refers to connecting of two flying objects in space, either to transfer men or material from one to the other, or two join two structures to make a bigger one.
Two satellites would be sent to space on board a regular PSLV mission and the two would be made to dock with each other, Sivan said, describing the exercise as a technology demonstration experiment.
Mastering this extremely difficult technology is crucial for the operations of an Indian space station, a lab up in space—astronauts would need to be ferried from the earth to the space station and back. This can be achieved only if the vehicle carries the astronauts can dock with the space station.
Asked when ISRO planned to build a space station, Sivan said that the project was still some distance away, and would be taken up only after the Gaganyaan mission, which is to take astronauts to space and bring them back to earth safely, through the rigours of re-entry into earth’s atmosphere. Gaganyaan is expected to happen in December 2021.
Docking is broadly for two different purposes—for sending human beings from a shuttle to a space station, or for assembling large satellites in space. Each of these has different complexities. In the case of docking for human transfers, there is scope for human intervention if something goes wrong; when satellites mate in space to form larger structures, it all has to be done by using devices such as sensors and cameras.
Imagine two objects – satellites – flying in space at incredible velocities, of the order of 10 km a second. When they are a few kilometres away, they communicate with each other and the one in front slows down in order that the follower comes close. When they are close enough, onboard cameras (or, lasers) switch on and they ‘look’ at each other. Guided by camera, one latches on to the other and the two become a larger structure. This way, enormous structures can be built in space.
Elsewhere in the world, there are talks of space solar stations, which are giant solar power plants up in space which produce electricity from the sun and beam it down to earth in the form of microwaves.
Docking will be a key capability in future space operations and ISRO’s first step in that direction –SPADEX—will happen next year.
(2/3) As of now what we now about SpaDex is that it's gonna consist of two 200kg satellites - a target vehicle and a chaser vehicle. At launch they'll be stacked on top of each other held together by only the docking ports.
(3/3) After separation from launch vehicle both vehicles will undock and drift apart. Later the chaser vehicle will perform autonomous rendezvous and docking with the target vehicle. The docking mechanism in itself appears to be highly inspired from NASA's IDSS used on the ISS.
On the challenge of integrating a docking system that is compatible, he said standard docking systems are in the public domain.
“...Whoever can design a docking system that matches with the US design and standard, can be used. However, we will still need to have agreements with agencies to try it out given that there are multiple interfaces — electrical, mechanical and so on. It is not just one document, we will need to work with them to develop it. We will do that.
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