First of all most of these Time Capsules USB ports are only USB 2.0. So while able to support a drive the speed of port is a bit anemic and as you are going with such a large drive you won't get the throughput you likely need.
Then we get into the USB power support which is your issue here as large drives will often need much more power! More so for a HDD vs SSD.
The killer is the larger HD drives disk mass increases as you add more platters, the head motors startup (torque) being the highest load time point. The USB standards make note of offering more power within USB 3.x
- USB 2.0: 5.0V - 500mA
- USB 3.0: 5.0 - 900mA
Here's a good writeup in more detail USB Decoded: All the Specs and Version Numbers
Backup and Large Data!
I had a similar issue, as my work was exceeding what I had for storage! As I'm an avid photographer and at one point had a part time business selling my work I needed to have my stuff accessible and I also didn't want to have only one copy of my work as that could be risky loosing many years of work.
I bought a collection of portable HDD's to use for off site backups and used a second set for rotation. That served me well at the beginning but as my work grew it became clear I needed something more. I then invested into a RAID box so I always had primary copy and then only used the portable drives for backup alone (still in rotation).
Even still the HDD's needed a sizable upgrade as the number of them was getting too large and becoming risky of not being able to recover my work. So I went with much larger SSD's reducing the number of drives then every three years I verified the integrity of the data to make sure it hadn't rotted as the early generation of SSD's had that as a risk. I only encountered the issue once and I replaced that drive with a newer one.
For guidance I follow Backblaze HDD Drive Stats making sure I haven't fallen into a low MTF HDD drive as well as Backblaze SDD Drive Stats while there SSD drives are mostly Seagate and Western Digital with a few others I haven't seen any testing with Samsung which I find interesting! But even with a low number and mostly used as a boot drive one has to consider the boot drive data is both static for the OS files, but very dynamic with caching! So there is a high degree of data churn and wear leveling taking place even on these drives. Which is why these SSD's can often fail from just too many rewrites, that is not the same issue of data rot! As they are really pushing these drives it gives you insight of what you can encounter!
So if you are like me I would alter your setup to a RAID if you need the data close by. And then look at least two drive sets for off site rotation. I mostly have drive sets setup by years as having one continuous backup that spans across so many drives also gets risky! I personally use Samsung drives based on my friends who work at a much higher level then even I ever did.
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