Adding to what Rory wrote regarding comm arrays:
You can also buy Tigersclaws at Technotic in Grim HEX, and at the Factory Line at the New Babbage Plaza (head to the center of the Plaza and walk downstairs). Buying them from the displays isn't working right now, but the Factory Line also has a terminal you can buy them from. You can also find them in loot crates.
To get in a comm array, you can park in a blind spot under the entrances, between the main structure and the solar panels, so your ship doesn't get shot at by the automated turrets. At least this used to be possible, and may or may not have changed. You can also shoot down the turrets, or have a buddy drop you off and pick you up. Using a hoverbike to get up to the entrance also works, and the Pulse is small enough to get inside. There are two entrances, located opposite from each other, 90 degrees from where the solar panels connect.
Hacking a comm array with a Tigersclaw takes about 5 minutes from the moment the hack starts. It sends an alert to other players, so you might get visitors. Sometimes, a comm array might be up, but the terminal says it's down. Simply click "reconnect" then "cancel" to take it down, without needing to insert a cryptokey. There's no automatic reconnection timer, it stays down as long as no one reactivates it.
There's been a bug for a while where you often cannot insert a cryptokey to hack the terminal. The issue has been marked as "under investigation" by CIG recently, and should hopefully get fixed soon.