What is PDR and CDR?

As someone who doesn’t like red tape there is no doubt that Preliminary design reviews (PDR) and Critical design review (CDR) have its uses and taking some of its aspects can be suitable for small organisations and hobbyists. Even carrying out a diet review session with peers or just taking the lessons learned from these sessions have benefits.

Preliminary design review (PDR)

A PDR is an assessment of the initial design against all the systems’ design requirements, and it is expected it will fulfill the project objectives. This also includes each subsystem, functions, interfaces, requirements, plans (schedules, experiments etc), costs and risks have been identified and sufficiently recorded. Essentially a PDR establishes this chosen concept to be the allocated baseline (1) in the project. Once it is deemed that the concept is mature enough the project can go ahead with detailing and realization of the design.

Critical design review CDR

A CDR is the final assessment of a detailed design before it can be manufactured, tested, and can meet all the requirements that were established at the beginning of the project (2). The main difference between a PDR and CDR is a PDR is to prove the design is mature enough to proceed where a CDR is to indicate the design will meet all the requirements. These requirements are not only performance but also risks, costs and scheduling. After the CDR the design will then be manufactured, tested, validated, and go into production or acceptance.

Promotes structure in your approach.

PDR and CDR reviews require structured reporting which can help promote good practice on report writing but also a good way of working. You are given objectives in how to succeed in these reviews and you must learn how to tackle such a significant milestone in the project.

You will learn to create plans for each subsystem, project timelines, testing plans, carry out sufficient research into the problem and maintain accurate and up to date records. Some red tape isn’t really a bad thing as some work on documentation will help avoid issues later and since you have planned everything out you are more prepared to overcome any foreseeable challenges.

Going through or pretending to work towards a review session will help eliminate bad habits and help you work in a more effective manner as you will avoid missing out on important information or design choices that could lead to expensive rework or delays.

Promotes due diligence.

You need to be able to justify your decisions in your current design and why you ignored alternative ideas. You can justify excluding or selecting your concept by using tools like Pugh Matrix and FMEA, results on calculations initial experiments on prototypes, simulations, reference to applicable standards and requirements.  This promotes the attitude that you carried out the required investigations, calculations, tests, carefully considered every option and detail you could feasibly think of based on your goals and requirements of the project. You selected a stainless steel bolt over and aluminium because it has the required strength, you selected a brass reaction wheel with a diameter of 10mm because it wouldn’t be affected by electromagnets in your satellite and allows the satellite to orientate itself quick and accurately enough. You replaced the payload because it wouldn’t fit or negatively affect the satellite’s performance. Every decision you have made has a reason and you know your design inside out. The review sessions can help you formulate better and more accurate experiments to prove out your final design as your design for experiments can also be reviewed. This will ensure that you don’t waste time and money on trials that might not be an accurate representation of its environment or demands.

Plus get into the habit of documenting everything even if this is a hobby project as you will forget some facets of your design and wonder why you selected 1 concept over the other. You don’t need to write a large document that you would send to NASA or ESA for your hobby 1P pocketqube that costs €200 to make but it’s useful just to record everything you have done to keep track of your project.

Promotes confidence.

Being able to justify every decision with facts should breed confidence in your design and help remove second guessing.  Having someone or a group of people with a fresh set of eyes reviewing your work can help identify flaws that you could have accidentally overlooked. Having your work scrutinized and being able to defend your work with facts and going through every detail of your concept will help build confidence going forward instead of double guessing yourself.

As uncomfortable review sessions can be they aren’t there to point out the blame or highlight your inadequacies. They are there to prevent your design or project from failing your or the customer’s goals, which are a much bigger problem which could have a negative impact on your confidence in the future.

Improves communication skills.

PDR and CDR reviews require you to be able to present and report on your design to people who may have no background knowledge on the project. This will help you develop skills where you can explain complicated concepts without confusing your audience while not omitting important information.

Can help build your network.

You won’t know everything and there are going to be details missed out and faults identified in your design, and you may not be able to answer or resolve these issues. This will require you to find out who has the required knowledge or skills to aid you. This could lead to meeting someone outside your current network which could lead to potentially new opportunities to share knowledge, contacts, and opportunities for future collaboration projects.

While PDR and CDR sessions won’t be applicable for all projects, especially for individuals, but by taking part in these sessions or learning what is required can help you improve your efficiency and employ good practices in your projects. You don’t need to do a full-blown review process but to have parties who aren’t involved in the day to day of a project allows you to talk to others about your ideas and could encourage you to reach out for help.

References

1. Preliminary Design Review (PDR). [Online] DAU. [Cited: February 14, 2023.] https://aaf.dau.edu/aaf/mca/pdr/.

2. Critical Design Review (CDR). [Online] Acq Notes. [Cited: February 14, 2023.] https://acqnotes.com/acqnote/acquisitions/critical-design-review.