SCP Foundation

SCP-XXXX is to be contained on Site 81 in a secure above ground (105m x 36m x 30m) hangar constructed of a standard steel alloy.

This is a little too precise, and it trips up over itself as a result. What does an "above ground hanger" mean? Is this building floating too? If you mean that this thing isn't stored underground, then you can just say hanger. Most readers know that a hanger can access the sky if it needs to, while a container can be massive and large but never give its inhabitant(s) access to the sky again. The exact dimensions of the hanger are unnecessary. The Foundation will automatically make sure the hanger is large enough to accommodate the zeppelin. However, being this specific implies that something horrible, or otherwise difficult to handle, will happen if the hanger is made with the dimensions of 105m x 37m x 30m.

The hangar has two small entrances on either side with electronic locks requiring Level 2 security clearance.

This isn't really necessary. This is mostly because the Foundation automatically locks the doors leading to anomalies. Furthermore, Level 2 is low enough that I don't think you really need it. This level encompasses most average researchers.

No personnel are allowed onsite between 10:00 PM and 5:00 AM without clearance from Dr. Schmidt.

Two things. First, as with the hanger dimensions, this implies that accessing this site outside of this time-frame results in a containment breach. Secondly, utilizing Dr. Schmidt as the sole junction for experimentation means that all experimentation will halt if Schmidt is incapacitated or unavailable. I would recommend simply stating that senior research staff have to authorize testing. You can insert Dr. Schmidt in other, more appropriate locations.

All items brought on board SCP-XXXX-A must be checked and logged, nothing brought onboard is to stay onboard when the hatch closes.

I assume this is because of the experiment logs you have yet to put up. So I will leave this untouched.

This is a safety precaution following experiment XXXX-03.

However, keep in mind that everything in the containment procedures are due to some specific reason. This part is redundant. When you put up the logs, the reasoning behind your previous statement should be self-explanatory.

Upon entry, personnel pass into an instance of SCP-XXXX hereon referred to as SCP-XXXX-A.

I'm conflicted regarding the separation between the idle SCP in the hanger and the other airship zipping around. This is mostly because you've relegated SCP-XXXX the duty of doorway. Personally, I believe that you can simply state that entering SCP-XXXX puts people in a mirror-dimensional version that can go anywhere.

Both SCP-XXXX and SCP-XXXX-A are completely indestructible, all attempts to break the windows or open the engine bay of either instance has been met with catastrophic failure resulting in █ deaths.

Grammatically, this needs to be split up with a semicolon at least. After indestructible, the last part of the second clause should read "all attempts(rest of sentence) have been met with (rest of sentence).

I wouldn't call XXXX indestructible. I would say it has an extremely lethal defense mechanism. This is because so far the only attempt at destruction has been the sledgehammer to the window. I would clarify what you mean by catastrophic failure since it's important to distinguishing between an entity that can kill things a lot faster before it can be killed, and an entity that can shrug off damage completely.

hours later, personnel boarded SCP-XXXX-A for the second time

While the Everest trip can be considered the discovery, the Mars trip sounds like it belongs more in a log than in the description. The description can state that SCP-XXXX can transport to interstellar locations, but the actual event that motivated this statement should be somewhere else.

Dear Dr. ██████,
This is the second god-damn time this year that you have nearly neutralized an SCP! SCP-XXXX is exceptionally valuable, the ability to randomly travel anywhere and do basic research on that environment is priceless,

This refers to the entire letter, not just this passage. The O5 letter is the weakest part of your article. This sounds more like a parent scolding a kid due to the irrational and unprofessional tone being displayed. Furthermore, stating that SCP-XXXX is priceless does not make it priceless. You have yet to justify that statement in your article. Show, do not tell. Furthermore, I find it unlikely that O5, who control global operations, would personally contact SCP-XXXX's researcher regarding this. Also, there are 13 O5 Council members. There is not an O5 staff.