Why don't all the doors in Destiny have pressure sensors?

Question

In SGU: "Intervention" and "Awakenings" as well as some other episodes, the destiny is shown to contain airlocks with pressure sensors. A bar moves up as the pressure goes up and when the it is at the top, a light that was first red becomes green. The user can now open the door. They also said that kino's have sensors that scan atmospheric makeup.

In SGU: "Air" and "Intervention" as well as other episodes, they opened a door unknowingly there was a hull breach and vacuum on the other side, which doesn't sound like the ancients did a good job on the doors inside the ship while it was in their capabilities to do so.

The ancients even knew there was going to be some dangers along the line, so they equipped the ship with weapons and shields that can correct hull breaches, but why didn't they put pressure sensors on their airtight doors, so you don't unknowingly open a door with vacuum on the other side?

Answer 1

Airlocks have the pressure sensor since their seals are rated for hard vacuum and during normal operation will encounter it. Your internal doors may be able to withstand vacuum and if you have sufficient power for internal sensors and automatic doors they probably won't open automatically if an adjacent sensor is a low pressure zone. But that doesn't prevent them from manually opening doors to low pressure zones. They won't protect you if you insist on opening that door.

With the lack of power and manual door opening could lead to opening to vacuum. Also if the pressure sensors are damaged or power impaired they wouldn't trip a door failsafe. Taking into account state of the Destiny, it is probable that there are auto failsafes in place but they are broken, like the rest of the ship, and therefor cannot be relied on.

As far as I remember, every time the door opens to vacuum they are manually opening a door, not using the door panel.

Answer 2

At least in "Air" the door was locked -- it took an override from the control center to open it. (Source -- http://stargate.wikia.com/wiki/Air,_Part_2 ) Which I think suggests you are (at least somewhat) incorrect in your thought about Ancient ship design. But as Stargate Atlantis frequently pointed out, the Ancients did make mistakes.

Also -- don't discount the fact that Destiny was quite old in SGU, and had taken much damage over those years. While there were mechanisms in place to effect repairs (such as the repair drones), we don't know if there was enough time to be able to repair the sensors used to detect hull breaches all across the ship by the time of the episodes "Incursion" or "Intervention". Even with the level of redundancy put into many systems on Destiny (such as the FTL drive), it's possible that even those redundancies failed in some areas.

Answer 3

For the same reason that the toilet doors in aircraft are not airtight with crew required to "set to automatic and cross-check" whenever someone fancies a piss.

For the same reason that your front door is thicker than your bedroom door.

For the same reason that there is no crumple zone in the drivers' seat.

It is a general rule of construction that you do not use more resources than you need to. With airlocks functioning correctly, and the ship in otherwise good health, only the outermost doors need to be sealable. Everything else can be quick, cheap and efficient.

It's worth noting that the internal doors on Destiny were evidently good enough to prevent leaking to vacuum, and that the computer refused to open an internal door to vacuum (the lack of pressure outside of airlock having been caused by damage) until Eli overrode it. The corridors were all drawn in red on his computer screen.

The design is sufficient.