Singularity - Space Apps Challenge

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For bigger spacecraft capable of executing bigger missions, some of the assembly may be done in space. Your challenge is to design a simple approach that enables components to be assembled in space.

TEADS : TEther Augmented Docking System

Summary

We have developed a docking mechanism termed TEADS (TEther Assisted Docking System) that incorporates state of the art innovation in tether propulsion systems and sensory relay (TriDAR, Flex Sensors) to allow autonomous guidance and docking of two spacecraft in orbit. It increases the safety and decreases the time consumption in docking procedures, aslo being backwards compatible with existing docking mechanisms on present space stations with small additional add-ons at the same time.

How We Addressed This Challenge

WORKING:

Phases of Docking

The Entire Docking System is an intricate yet completely automated mechanism, and can be described in three integral processes or steps :

1) Orbital Rendezvous in Tether Range

2) Tether Ejection and spacecraft capture

3) Retrieval of Spacecraft and Hard Docking

Orbital Rendezvous

The tracking spacecraft that is to dock with the space station will be launched via a rocket from the desired space launching facility.

Orbital Rendezvous will be carried out with the help of a standard Hohmann transfer maneuver to the desired rendezvous in line-of-sight such that the target spacecraft and the tracking spacecraft are in proximity and in docking-phase tether operation range (~10-100m).

Once in Proximity the two spacecraft will be ready to initiate automated tether guided docking maneuvers.

Tether ejection and Spacecraft Capture

The smart tether-guided docking mechanism is the main component of TEADS. Four maneuverable smart tethers equipped on the target spacecraft in a ring fashion that are independent yet symbiotically compatible with the androgynous International Docking Adapter will be released with the motive of capture of the tracking spacecraft and its subsequent docking with the station.

These guidable tethers are equipped with tether heads that can be maneuvered using small cold gas propulsion thrusters, which provide six degrees of rotary freedom in space. The procedure for maneuvering the individual cables is undertaken by an artificially intelligent model for tethered propulsion installed inside a docking and guidance computer on the main target station.

Numerous flex sensors inside the tether cable, information regarding the exact position of the tether with respect to the station apart from TriDAR data can be relayed back for enhanced maneuverability, enabling a target accuracy of mere millimeters.

These tether heads are then guided to attach with complementary docking ports, wherein on confirmed contact, 4 pin latches engage a hard lock on the tethers, to secure them safely with the spacecraft.

We also allow restricted data transfer as soon as the first tether docks allow for crucial data transfer required between the dragon and iss and increase in data & power transfer with the docking of 6 tentacles.

The margin for error (or precision required) with which the electromagnetic soft dock of the tether to the tether lock port on “dragon” is also more substantial and even allows for retrieval of individual tether and multiple attempts with a very short reset duration (time to retry or something).

Retrieval of Spacecraft and Hard Docking

After a secured tether lock the spacecraft that is to dock is pulled closer towards the main docking hatch of the space station using the tethers as well as the onboard spacecraft propulsion thrusters at the speed of 0.1m/s, the final docking procedure occurs similar to the current standard docking procedure. The spacecraft is pressurised and is hence hard-docked.

Our goal was to design a self guided docking system which would be faster than the existing docking mechanism. We hoped to achieve a design with less complexity as compared to the docking systems. We wanted to come up with a mechanism that would not struggle to align itself with the space station to start the soft docking

How We Developed This Project

Inspiration - We were inspired by the concept of the challenge that is to create. It is a more hands-on project where we can innovate, design, and force ourselves to come up with a completely new system. Unlike the other challenges that involved building an app or software, this one was all about imagination and building new technology.

Approach - We studied the existing technology and docking mechanisms. We looked for problems and challenges faced by them and thought of how they can be improved and how the docking can be made faster, easier, and softer. We looked at each system and tried to improvise them individually, brainstorm, and come up with a viable pragmatic efficient, and an innovative idea/model/mechanism.

Tools - NASA and other open-source data provided by space agencies and available on the world wide web. Fusion 360 for building the model (give credits to AZAM ALI).

Problems & Achievement - One problem we faced was that all our innovations and ideas were already in existence and/or being currently developed so we were required to push ourselves for us to come up with something out of the box. As a result of which we came up with our tether guided soft docking system.

How We Used Space Agency Data in This Project

We started working on our challenge by reading the resources provided by NASA space apps challenge. We first read about OSAM and then in-space assembly of a telescope. This forced us to think about a mechanism that would assemble itself in space easily, instead of struggling to align itself with the space station to be able to dock precisely.

We read about the International Docking System Standard (IDSS) and Interface Definition Document (IDD) which is the result of a collaboration by the International Space Station membership to establish a standard docking interface to enable on-orbit crew rescue operations and joint collaborative endeavors utilizing different spacecraft. The spacecraft developer is supposed to make sure that all the verification and validation of the hardware are done in due course along with the analysis of final docking ensuring the needed docking performance and certification. The purpose of the IDSS IDD is to provide basic common design parameters to allow developers to dependently design compatible docking systems.

This document aided us to get acquainted with the current docking procedure and helped us approach the problem statement with a different standpoint.The document helped us in understanding the design better through diagrams which gave us a clear picture of what actually happens.

The first stage of docking establishes the initial capture of the docking vehicles and is performed by the Soft Capture System (SCS). During the capture phase, the active docking mechanism’s SCS aligns with and latches to the passive docking mechanism, then stabilizes the newly joined spacecraft relative to each other. The soft capture system then pulls the docking spacecraft together to initiate the second stage of docking, performed by the Hard Capture System (HCS).

Using the given information,we decided to think of a faster and softer docking mechanism. We devised a suitable SCS using tether cables to capture the incoming spacecraft. A self guided design which will easily align itself more precisely.

The HCS performs structural latching and sealing at the docking interface to transfer structural loads between the spacecraft and to create a transfer tunnel which can be pressurized for crew and cargo transfer for joint mission operations.

We came across a Tether Technology Interchange Meeting and a Tether docking of orbiting spacecraft Final report research paper on NTRS. This cleared all our doubts regarding tethers.

From Tether Technology Interchange Meeting research paper We learnt about the strength requirements, qualification testing, proof tests that need to be done, the weight, temperature and pressure conditions required while designing a competent tether technology. Tether based satellite technology has already been formulated, on the basis of existing thesis and experiments, we came up with our soft docking system keeping all said results in mind. While constructing our prototype, we also took the disadvantages and problems already faced in mind. Meteoroids and space debris can cause severe tether damage resulting in remnants recoiling into the body, the probability of tether server can be reduced by reducing its length and time deployed. Probability of tether server can be reduced by design and redundancy.

The Tether docking of orbiting spacecraft Final report gave us an in depth study of the system dynamics and some observation tables of the initial and final conditions of the chase vehicle behind the target vehicle. The report also mentioned the weight of the tethers used along with well descriptive diagrams of the tether. This helped us refine the tether design we had in mind.

We used other space agency data such as JAXA and ESA.

The research papers on tether we found on JAXA were all on electromagnetic tethers and their working. The document was about investigating an active space debris removal system that employs highly efficient electrodynamic tether technology. This gave us a clear idea of the working, the numerical data, diagrams, and graphs.

We found several integral resources from the ESA. This helped us generate ideas to build our system.

We then researched the different materials suitable to fabricate the tether cables. We explored the materials being used currently and studied their properties. We came across a research paper by NASA on NTRS where the physical properties of several materials in a tether-based use environment were provided. It showed pre and post-flight conditions of the material, the shortcomings, data which proved how long it would take a particular material to get eroded and which material can withstand radiation. With the help of this, we came up with a few suggestions, with the appropriate use of material sciences and after performing suitable tests, we were able to rule out several materials. We can decide on the relevant material needed.

Finally, after extensive research and collective knowledge acquired by documents provided by space-literate organizations and their faith in open data, we came up with a design of our own, a soft docking mechanism- TEADS: TEther Augmented Docking System.