Build or buy?

With the FEA simulations, engineering drawings and tolerance stacks complete I am waiting on the suppliers responding to my RFQ (Request for Quote) for machining the worlds lightest 6P pocketqube deployer.  I will be comparing the quotes and then wil be raising an order soon.

While I am waiting for their responses I have been looking into buying a Hold Down Release Mechanism (HDRM) to complete the assembly. I would like to build my own lock but I decided to go for a Commercial Off The Shelf (COTS) to speed up development and reduce costs.

This made me think about the balance of developing in house and buying COTS which is something that I am sure people developing cubesats and pocketqubes on a budget. This is why I want to raise some things you should consider before deciding to build or buy.

Time

How long you have till launch or the length of time you have in a project is something that needs to be considered.

Developing and qualifying a new pocketqube system can take a lot of time and this needs to be considered if you are under a tight schedule. Fault finding and identifying the root causes can be a time consuming process. However one thing I have done in the past is take off the shelf components and modified them for my needs. This helped speed up my development. If you pick parts that you know will work then that will help eliminate possible causes to a failed test which will also help reduce downtime.

Expertise/Experience

Have you had previous experience in developing a similar system? Have you got the skills to be able to develop the subsystem or can you get help from a contactor,mentor or be able to join a training course?

If you do something for the 1st time (especially developing the various subsystems) it can be a daunting (but fun) task and you will likely make mistakes. However adequate training and support will help you avoid a lot of these mistakes.

However building your own system will enahnce your capabilities. You can use COTS components to learn how to design and build your custom parts.

Availability

Is there an off the shelf solution availble and can you acquire it on time?

If there is a system available and you can afford it you should consider the lead times as there is no point ordering that EPS system if it will arrive in 4 months time and you need to integrate your pocketqube to my 6P POD (hint hint) in 3 months.

If there is no solution that meets your requirements or none availble then you have no choice but to build one yourself.

Budget

It doesn’t take long to find out that spacequalified parts are expensive for expample the HDRM I want to use for my deployer won’t be cheap.

If you are running a company or paying a team you need to understand that wages is an expense that is always overlooked when developing an in house system.  Trying to build a custom solution on cheap parts or poor equipment is a false economy because you will more likely have to redo the design and it might take longer than it should be.

Also the complexity of the subsystem or part has to be considered. If it’s a simple mechanical system like a hinge yeah go ahead but if it’s an ADCS system or something just as complex you got to make sure you have the budget and time to develop and qualify it.

This can lead to a custom ADCS system being more expensive than a COTS ADCS. Also you have to make sure you have budgeted for rework, redesign and figuring out why your design failed as a new design built from scratch is more likely to fail in the 1st, 2nd and even 3rd attempts.  For example if it takes you 4 months to build and test your custom system while paying an engineer at €2000 per month then you include machining costs, material, tooling, testing and equipment you could be looking at double or treble the price (unless you can get freebies) than the off the shelf system.

Asking for offcuts from rejected material or samples can help reduce development costs.

If you have the budget to develop a system that meets your needs then batter in. Plus once you crack it you could sell the system to other pocketqube teams.

Conclusion

I will say in future I will be looking to develop my own custom HDRM as I want to improve my skills and have better control on leadtimes and costs of manufacturing my deployer. Plus I can also integrate the HDRM into the deployer which will help reduce it’s mass.

Building in house will enhance your knoweldge of your system and as you gain more experience,knoweldge and skills. This will allow you to build more advanced and reliable satellites at a faster rate. In addition it’s a great feeling when you bring a sketch to fully working solution.

When you are building a pocketqube or cubesat for the first time you should look into buying COTS for critical systems to help derisk the development. Once you have a space qualified system you could look into customising your satellites more in future missions.

 

Follow me on twitter (@Spaceca27508118) to keep up to date on the developments of my deployer.

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