P18101: CubeSat Solar Sail
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Problem Definition

Table of Contents

Team Vision for Problem Definition Phase

The Problem Definition phase is the foundation for all of MSD I & II. The project cannot be completed without a clear definition of objectives and deliverables. For this phase, the team primarily sought to refine and expand the work done to create the project proposal. This included finalizing a Problem Definition and Use Cases as well as formally tabulating Customer Needs and Engineering Requirements. The team also began considering potential risks and challenges, and lastly set out to create a draft Project Plan for the remainder of MSD I.

The team was largely successful in meeting these phase objectives. The results are laid out below. The Customer Needs meeting was helpful for adding needs and clarifying use cases. This phase culminated in the Problem Definition Design Review. Although the specifications on this page may change, the team should now have the necessary groundwork to begin the design of the product with an accurate bearing towards the end goal.

Project Summary

A solar sail is a thin sheet of highly reflective material which utilizes the momentum of a star's photons to propel small spacecraft. Solar sails can be used both to accelerate spacecraft to high velocities and to deorbit existing satellites. This technology eliminates the need for traditional propellant fuels which are costly, heavy, and limited. Such a propulsion system is thus highly compatible with CubeSats, miniature satellites made primarily for scientific experimentation which focus on compact, standardized, and modular design. In 2015 the Planetary Society launched a larger CubeSat model with a solar sail incorporated amongst its scientific instruments.

The aim of this project is to design and prototype a deployment mechanism for a solar sail contained within a CubeSat. The goal is for this Cubesat to be integrated into another RIT Space Exploration satellite in order to test the concept of solar sail propulsion for positioning and high speed space travel. The desired outcome of this project is a repeatable and remote sail deployment system which meets all the specifications of CubeSat regulations, does not compromise stability, and minimizes weight and volume.

Use Cases

Two primary hypothetical use cases have been detailed for this activity. The first simulates a research mission primarily designed to observe the behavior of the solar sail system within its intended operating environment, while the second case details using the mechanism as a means to de-orbit a piece of detritus that would otherwise remain in space.
Use Case One: Research Mission

Use Case One: Research Mission

Use Case Two: Deorbiting Space Debris

Use Case Two: Deorbiting Space Debris

Project Goals and Key Deliverables

The expected end result of this project is for the SPEX team to receive a working prototype of the solar sail deployment mechanism, as well as all supporting documentation including but not limited to a bill of materials, access to all CAD files used in creation of the project, and so on.

The project is intended to be completed and demonstrated at the Imagine RIT festival in the Spring semester of 2018.

Customer Requirements (Needs)

Customer needs were based on preliminary discussions with the customers, as well as an interview conducted on Wednesday, August 30, 2017. In addition, requirements are added or updated as the semester progresses. The up-to-date document taking all of these inputs into consideration can be found here. These needs are prioritized on a numbering scale from one to nine, with a nine indicating a feature that is absolutely essential to the design, and three indicating features that would be ideal, but would not largely impact the project if they were not met.
Up-to-Date Customer Needs Table

Up-to-Date Customer Needs Table

Engineering Requirements (Metrics & Specifications)

Quantifiable engineering specifications were generated from the customers' needs following the interview conducted with them. Since the design must live within CubeSat regulations, it must operate within the conditions detailed within this document from the CubeSat program. These requirements are also listed within the same spreadsheet as the customer needs, and are linked above.
Up-to-Date Engineering Requirements Table

Up-to-Date Engineering Requirements Table

Constraints

As an Aerospace Senior Design project, this design comes with several unique constraints. Some relate to customer requirements, while many relate to the challenging environment of outer space itself. These are more general and encompassing than the specific requirements. Listed below are the chief design constraints which must be worked around going forward:

House of Quality

A House of Quality was constructed to compare the importance of each need from a customer standpoint and engineering standpoint. The importance scale from one to nine used earlier is utilized here, as well. Relative weights are obtained by multiplying the qualitative customer need's weight by the quantitative engineering requirement's weight. The live document can be found here.

House of Quality

House of Quality

Benchmarking

As this field is not yet largely occupied by other projects, there are not a large variety of comparisons to make in terms of performance. The most comparable design has been produced by the Planetary Society, and while this design was successfully launched into space, its communication systems initially malfunctioned. NASA has also produced a much larger scale model of the same type of design, however the project was canceled before it could be transported to space. NASA has also produced a design with a smaller sail area, but this design utilizes a different method of extending its sails. These designs were collectively used to generate initial target specifications to discuss to the customer, and were refined in the Engineering Specifications table above as more information was gleaned. The editable benchmarking table can be found here.

Benchmarking Table

Benchmarking Table

A key component of benchmarking was to determine how our design differs from existing ones. For this comparisons were made to the Planetary Society Lightsail CubeSat, the NASA Nanosail D and D2 CubeSats, the Lunar Flashlight CubeSat,the NASA Sunjammer, and the NASA NEA Scout CubeSat. This was primarily done to identify key aspects of the design and to compare them with ours to ensure we weren't doing work that someone else had already done. The results of this can be seen in the table below.

Updated Benchmarking

Updated Benchmarking

The key takeaways from this analysis are that our design is most similar to the Planetary Society Lightsail. Other designs have employed a variety of deployment mechanisms, but deploying all of the booms from a central spindle seems to be the most common. It has been shown that strain energy alone can deploy the booms, although most designs used motorized deployment. Aluminized materials, whether it is CP1, Kapton, or Mylar, are by far the most dominant sail materials. Our sail area is on the smaller scale compared to existing or planned projects, with all other small scale (<35 sq. m) sails also using the central spindle deployment. Our design differs from these though in that our sail is being stored in 4 separate storage areas while the other small scale sails deployed their sails from a central spindle like the booms.

Critical Design Challenges and Risk Management

Critical Design Challenges:

1. Location for building and testing

2. Sail material selection

3. Boom mechanism stability

4. Minimize moment created

5. Budget space for control system (button, communication, sail controls)

6. Double design for air brake as well as solar sail

7. Durability during launch

8. Designing for CubeSat specs

9. Attachment of sail to boom

10. Folding pattern

11. Electrical hardware designed for space

Risk Management:

public/Problem Definition Documents/P18101_Risk_V1_1.PNG

Design Review Materials

Below are links to documents related to and generated from the Problem Definition Design Review

Plans for next phase

In the next few weeks leading up to the next review, the main design goals are to identify the subsystems required to build the device. The sail itself is a crucial element of the design, so an appropriate amount of time will be dedicated to researching materials, as well as determining aspects such as the sail thickness and folding pattern. The rest of the time will be dedicated to developing the basic circuit for the activation of the deployment mechanism, as well as creating concepts for the deployment mechanism.

Team plans and individual plans will be determined and finalized following the first design review on 14 September, 2017, and may be subject to change as new elements of the project present themselves.

Each team member will complete the following tasks:

Victor Braescu:

Update Project Schedule

Complete Mass Feasibility Analysis

Collaborate with team to come up and evaluate system design concepts

Send email to Professor Barbosu asking for operating altitudes

Michael Berezny:

Collaborate with team to come up and evaluate system design concepts

Research existing solutions and sail material availability

Complete Volume Feasibility Analysis

Andrew Lewis:

Collaborate with team to come up with and evaluate system design concepts

Create high-level concept sketches for primary designs

Complete Moment Feasibility Analysis

Research sail material candidates and joining methods

Generate systems architecture flowchart based on inputs from team

Eric Pareis:

Collaborate with team to come up with and evaluate system design concepts

Complete cost of memory metals feasibility analysis

Research launch stresses and forces

Generate updated risk assessment


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